High-hardness and high-bonding-force colorful iridescent composite film for plastic surface and its preparation method

Abstract

The present invention relates to the field of multi-layer films, and discloses a high-hardness and high-bonding-strength color-changing composite film for plastic surfaces and a preparation method thereof. The color-changing composite film comprises a Ti seed layer, an Al layer, a TiN layer, a TiAlN layer and an AlN layer which are sequentially deposited on the plastic surface by magnetron sputtering. The present invention generates structural colors related to the thickness of the top layer through the principle of thin-film interference. The multi-layer film structure exhibits double-resonance absorption, and a wide color gamut range is obtained on the chromaticity diagram. The present invention ingeniously deposits Ti, Al, TiN, TiAlN and AlN on the plastic surface in sequence by magnetron sputtering. Among them, the bonding layer Ti seed layer can greatly improve the adhesion of the multi-layer film structure, and at the same time, the overall brightness of the color is improved by applying a highly reflective Al layer. The structural colors obtained by thin-film interference have excellent color-changing and color-shifting effects, providing a new manufacturing method for high-end color decorative coatings on plastic surfaces.

Description

Technical Field

[0001] The present invention relates to the field of multi-layer films, and particularly to a high-hardness and high-bonding-colorful and iridescent composite film on the surface of plastics and a preparation method thereof. Background Art

[0002] Due to their diverse colors, low cost, and easy processing, colored plastics are widely used in industries such as art decorations, toys, packaging, and automobiles. Iridescent plastics are more applied in high-end markets and design fields. Their special optical effects give products stronger visual impacts and artistic senses, and they are widely seen in creative arts, automobiles, and luxury goods.

[0003] The production methods of traditional colored plastics and iridescent plastics with special visual effects such as color change, gradient, and metallic luster usually rely on the use of pigments, dyes, or other special additives to achieve unique color effects. The colored plastics on the market are usually formed by adding pigments or dyes to resins during the plastic processing and production process or coating colors on the surface of products. However, the compatibility between the molten resin and inorganic pigments is poor, which will cause uneven surface colors of plastic products. More importantly, some colored plastics made of chemical dyes have very poor long-term stability and will degrade over time, thus losing their chromaticity and brightness. And the direct coating method will lead to easy color fading of plastic products due to the poor bonding force between the coating and the plastic surface. In addition, the surface hardness of the colored plastics made by these methods is relatively low, and scratches and cracks are likely to appear during the manufacturing and transportation processes. And it is difficult to achieve the iridescent effect simply by using chemical dyes or coatings. Therefore, there is an urgent need for physical structural color plastic products with colored and iridescent effects. However, in practical applications, it is still a daunting challenge to simultaneously achieve a wide color gamut, high hardness, high bonding force, low-cost manufacturability, long-term stability, and variable viewing angles of structural colors.

[0004] Magnetron sputtering technology is an environmentally friendly surface film treatment technology. The film has a high density and low resource consumption. Magnetron sputtering refers to the process of depositing atoms of substances such as metals and compounds on the surface of a substrate to form a film by bombarding the surface of a target with energetic particles under vacuum conditions. Compared with traditional electroplating and electroless plating technologies, in magnetron sputtering technology, the plastic substrate does not need to be conductive, and the film is prepared at the atomic and molecular scales in a vacuum, with higher density, fewer defects, and better performance. When using magnetron sputtering technology to prepare multi-layer films, different colors are generated through interference effects. The prepared film has a dense structure, good stability, and the color does not fade during long-term use in the environment.

[0005] Many nitride semi-transparent coatings can produce structural colors with a wide color gamut, never fade, and are non-toxic and pollution-free through thin-film interference effects. Moreover, as the thickness of the semi-transparent interference layer increases, this structural color changes with the observer's viewing angle, having a good iridescent effect. Additionally, the metal nitride itself has a high hardness, thus providing good protection for colored and iridescent plastic decorations. However, the applicant found in previous experiments that the adhesion between the directly deposited metal compound and the plastic substrate is poor, and it is difficult to reflect most of the visible light to the top layer, resulting in a low color saturation. In addition, the melting point of the plastic is relatively lower than that of the metal, and the deposition time needs to be accurately controlled. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a high-hardness and high-binding-force colored iridescent composite film on the plastic surface and a preparation method thereof. The colored iridescent composite film on the plastic surface of the present invention simultaneously has the characteristics of high film-substrate binding force, high hardness, high wide color gamut, long-term stability, and variable viewing angle.

[0007] The specific technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a high-hardness and high-binding-force colored iridescent composite film on the plastic surface, which includes a Ti seed layer, an Al layer, a TiN layer, a TiAlN layer, and an AlN layer sequentially deposited on the plastic surface by magnetron sputtering.

[0009] Among them, the growth mode of the Al layer is an island-layer combined growth mode; the aluminum grain size in the Al layer ≥ 100 nm; the surface roughness of the Al layer < 3 nm; the AlN grain size in the AlN layer = 80 - 150 nm; the thickness of the AlN layer is 35 - 180 nm.

[0010] In the present invention, Ti, Al, TiN, TiAlN, and AlN are sequentially deposited on the plastic surface by magnetron sputtering. The Ti seed layer located in the first layer serves as an adhesion layer, which can significantly improve the adhesion of the subsequently deposited multilayer film. The Al layer in the second layer serves as a high-reflection layer, reflecting most of the visible light incident on the plastic substrate. The third layer is the TiN layer serving as a reflection layer, and the fourth layer is the TiAlN layer serving as a high-absorption dielectric layer. This double-layer TiAlN-TiN thin film, as a broadband absorber, can exhibit thickness-dependent colors, but its color gamut is relatively narrow. Therefore, when the present invention continues to deposit the fifth layer, the AlN layer serving as a semi-transparent dielectric layer, on the TiAlN-TiN absorber, a significant change in the observed color can occur. In particular, red and green are obtained after depositing AlN, and the corresponding color gamut is significantly expanded. When the AlN layer reaches a certain thickness, the structural color generated by thin-film interference changes with the change of the observer's perspective, producing an iridescent effect. This colored and iridescent nitride thin film has a dense surface, high color saturation, and high hardness, and has an excellent protective effect on the prepared colored and iridescent plastic products.

[0011] Specifically, the preparation principle of the high-hardness and high-bonding-strength iridescent composite thin film on the plastic surface of the present invention is as follows:

[0012] For the enhancement of the film-substrate bonding strength: The present invention ingeniously improves the film-substrate bonding strength by adding a Ti seed layer as a bonding layer. This is because the interface between the plastic and Ti has a high reactivity, and Ti reacts with the functional groups on the plastic surface to form a large number of C-Ti and (C-O)-Ti bonds, thereby improving the bonding strength between the thin film and the plastic. The subsequent Al layer deposited on the Ti seed layer improves the bonding strength by forming metal bonds between aluminum atoms and titanium atoms.

[0013] For the generation of structural color: A highly absorptive medium TiAlN layer is deposited on the TiN layer to construct a TiAlN-TiN absorber. When a semi-transparent dielectric AlN layer is deposited on the TiAlN-TiN absorber, the resulting color can change significantly. The multilayer film structure exhibits double-resonance absorption, greatly increasing the color gamut range. This is because the semi-transparent dielectric AlN layer and the light reflected from the TiAlN-TiN absorber will interact, thus generating interference-based colors. In this case, the color of the coating is determined not only by the electronic band structure (the refractive index of the material) but also by the geometry, that is, by the thickness of the thin film. Along with the increase in the thickness of the AlN layer, the interference-generated color will also show an iridescent effect. This is because the thickness of the top AlN layer directly determines the magnitude of the optical path difference. A thicker AlN layer requires a greater optical path difference to reach the interference condition, so different angular variations will more significantly affect the observed color. If the thickness of the AlN layer is too thin, it is difficult to produce the effect of thin-film interference and no color can be generated, only the golden yellow of the bottom layer. If the AlN layer is too thick, there is a color overlap interval for the same coating thickness, which will result in multiple light waves in a single-thickness coating, and the color of the coating is a mixture of multiple colors rather than a single color.

[0014] For the improvement of color brightness: First, the sputtering threshold energy of the Ti seed layer is higher than that of aluminum, and the Ti seed layer is denser and has a higher hardness. Compared with the plastic substrate, it can provide a higher surface energy interface for the subsequently deposited Al layer, thereby reducing the diffusion of Al on the seeded substrate, having more nucleation sites, and reducing the pinhole-like defects on the surface of the Al layer. Second, due to the similar dissociation energies of the Al-Al bond (264 kJ / mol) and the Ti-Al bond (263 kJ / mol), the Al layer grows in a layer-island bonding mode and the surface roughness is reduced. The present invention finds that the aluminum grain size deposited on the surface of the Ti seed layer is larger than that of the sample without the Ti seed layer coating. The larger the aluminum grain size, the fewer the grain boundaries, the weaker the grain boundary plasma resonance, and the less light scattering caused, so that the Al layer can provide a highly reflective substrate for the outermost TiN-TiAlN-AlN film layer structure, thereby achieving the effect of improving color brightness. In addition, the present invention also finds that the Ti seed layer can not only greatly improve the adhesion of the Al layer but also effectively reduce the surface roughness of the Al layer, avoiding defects such as pinholes, thereby further improving the reflectivity of the Al layer.

[0015] Preferably, the thickness of the Ti seed layer is 45 - 65 nm; the thickness of the Al layer is 20 - 30 nm; the thickness of the TiN layer is 45 - 50 nm; the thickness of the TiAlN layer is 40 - 50 nm.

[0016] Preferably, the plastic is one or more of polycarbonate (PC), polymethyl methacrylate (PMMA), polyphenylene sulfide (PPS), polystyrene (PS), and polyethylene terephthalate (PET); more preferably, it is polycarbonate (PC) or polystyrene (PS).

[0017] PC not only has high strength and excellent heat resistance, but also has good weather resistance and anti-aging performance, and can be used outdoors for a long time without failure. And PS not only has high hardness, but also has low cost and is easy to mass-produce.

[0018] In a second aspect, the present invention provides a method for preparing a plastic surface high-hardness and high-bonding-strength color-changing composite film, which includes the following steps:

[0019] 1) Depositing a Ti seed layer on the plastic surface by magnetron sputtering;

[0020] 2) Depositing an Al layer on the surface of the Ti seed layer by magnetron sputtering;

[0021] 3) Depositing a TiN layer on the surface of the Al layer by magnetron sputtering;

[0022] 4) Depositing a TiAlN layer on the surface of the TiN layer by magnetron sputtering;

[0023] 5) Depositing an AlN layer on the surface of the TiAlN layer by magnetron sputtering.

[0024] Preferably, in step 1), before depositing the Ti seed layer, the plastic surface is degreased, decontaminated, and dried; under inert conditions, the oxide layers on the titanium target and aluminum target are removed by magnetron sputtering, and the plastic surface is activated by surface plasma.

[0025] Preferably, in step 1), the deposition conditions of the Ti seed layer are: deposition current is 1.5 - 2.5 A, negative bias voltage is 60 - 100 V, and time is 8 - 20 min.

[0026] Preferably, in step 2), the deposition conditions of the Al layer are: deposited by facing target sputtering, deposition current is 2 - 4 A, negative bias voltage is 60 - 100 V, and time is 2 - 10 min.

[0027] Preferably, in step 3), the deposition conditions for depositing the TiN layer are: introducing 20 - 40 sccm of argon and 5 - 10 sccm of nitrogen, Ti target deposition current is 1.5 - 2.5 A, Ti target negative bias voltage is 60 - 100 V, Al target current is 0.2 - 0.4 A, and deposition time is 10 - 30 min.

[0028] Preferably, in step 4), the deposition conditions of the TiAlN layer are as follows: 20 - 40 sccm of argon and 5 - 10 sccm of nitrogen are introduced; the deposition current of the Ti target is 1.5 - 2.5 A, and the negative bias voltage of the Ti target is 60 - 100 V; the deposition current of the Al target is 1 - 2 A, and the deposition time is 5 - 15 min.

[0029] Preferably, in step 5), the deposition conditions of the AlN layer are as follows: 20 - 40 sccm of argon and 5 - 10 sccm of nitrogen are introduced; the deposition current of the Al target is 1 - 2 A, the negative bias voltage of the Al target is 60 - 100 V, and the deposition time is 20 - 180 min.

[0030] Preferably, in steps 3), 4) and 5), during sputtering, all current biases are turned off every 5 - 50 min to cool the chamber.

[0031] The purpose of the above settings is to prevent the internal temperature of the chamber from being too high during the deposition process, which may cause the plastic substrate to melt. The specific interval time depends on the melting point of the plastic.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) In the present invention, a Ti seed layer and an Al layer are sequentially formed on the plastic surface by magnetron sputtering; the Ti seed layer can greatly improve the adhesion of the Al layer. At the same time, the Ti seed layer can also improve the density of the Al layer, reduce the surface roughness of the Al layer, and avoid defects such as pinholes, thereby improving the color brightness of the color-changing composite film.

[0034] (2) Based on the thin-film interference principle, a pollution-free, non-fading, and high-color-saturation color-changing film is constructed on the plastic surface in the present invention. As the thickness of the AlN layer increases, the color of the composite film changes with the observer's viewing angle, showing a color-changing effect, with saturated colors, a wide color gamut, and good stability.

[0035] (3) By combining the plastic with the color-changing composite film in the present invention, the surface hardness of the plastic product is improved by the nitride ceramic film, which has an excellent protective effect on the plastic product. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic structural diagram of the color-changing composite film of the present invention.

[0037] Figure 2 It is a reflection spectrum diagram of Examples 1, 2, 3, 4, 5 and 6 in the wavelength range of 380 - 800 nm.

[0038] Figure 3 It is a CIE chromaticity diagram of Examples 1, 2, 3, 4, 5 and 6.

[0039] Figure 4 Digital photos of the composite film on the plastic surface: (a) Example 1, (b) Example 2, (c) Example 3, (d) Example 4, (e) Example 5, and (f) Example 6.

[0040] Figure 5 Digital photos of the iridescent composite film sample in Example 6 at different viewing angles: (a) 0 ° , (b) 22 ° , (c) 45 ° , (d) 68 ° , and (e) 90 ° .

[0041] Figure 6 SEM images of the highly reflective aluminum film: (a) Comparative Example 1; (b) Example 9.

[0042] Figure 7 SEM image of the iridescent composite film in Example 6.

[0043] Figure 8 Optical picture of the sample in Example 5 after the Rockwell hardness test.

[0044] Figure 9 Digital photos of the colored composite films on the PS plastic surface of Example 7 (left) and Example 8 (right). Detailed implementation mode

[0045] The present invention will be further described below in conjunction with the examples.

[0046] General example

[0047] First, a high-hardness and high-bonding-strength colored iridescent composite film on the plastic surface, which includes a Ti seed layer, an Al layer, a TiN layer, a TiAlN layer, and an AlN layer sequentially deposited on the plastic surface by magnetron sputtering.

[0048] Among them, the growth mode of the Al layer is the layer-island combined growth mode; the aluminum grain size in the Al layer is ≥100 nm; the surface roughness of the Al layer is <3 nm; the AlN grain size in the AlN layer is 80-150 nm.

[0049] In some preferred implementation cases, the thickness of the AlN layer is 35-180 nm, the thickness of the Ti seed layer is 45-50 nm; the thickness of the Al layer is 20-30 nm; the thickness of the TiN layer is 45-50 nm; the thickness of the TiAlN layer is 40-50 nm.

[0050] In some preferred embodiments, the plastic is one or more of polycarbonate (PC), polymethyl methacrylate (PMMA), polyphenylene sulfide (PPS), polystyrene (PS), and polyethylene terephthalate (PET); more preferably, it is polycarbonate (PC) or polystyrene (PS).

[0051] Secondly, a method for preparing a plastic surface high-hardness and high-bonding-colorful magic-color composite film specifically includes the following steps:

[0052] 1) Deposit a Ti seed layer on the plastic surface by magnetron sputtering.

[0053] In some preferred embodiments, the deposition conditions of the Ti seed layer are: deposition current is 1.5 - 2.5 A, negative bias voltage is 60 - 100 V, and time is 8 - 20 min. Controlling the deposition conditions of step 1) within the above range is because: if the current is too low, it is easy to result in a small number of sputtered atoms and low energy, slow film deposition rate, and the low-energy atoms reaching the plastic substrate cannot spontaneously migrate to the surface defects; conversely, if the current is too high, the number of sputtered atoms increases, and the temperature inside the cavity rises sharply with the deposition time, and the structure of the plastic substrate is easily damaged.

[0054] In some preferred embodiments, before depositing the Ti seed layer, degrease and decontaminate the plastic surface and dry it; under inert conditions, magnetron sputter to remove the oxide layers on the titanium target and aluminum target, and perform surface plasma activation on the plastic.

[0055] In some more preferred embodiments, first ultrasonically clean the plastic surface with chemical reagents and water to degrease and decontaminate it, and then dry and bake it with cold and hot air.

[0056] More preferably, the chemical reagent is anhydrous ethanol, isopropanol, or acetone. The baking temperature is 50 - 80 °C, and the time is 120 - 240 min.

[0057] More preferably, the magnetron sputtering to remove the oxide layers on the titanium target and aluminum target and perform surface plasma activation on the plastic specifically includes: fixing the plastic on the base stage in a closed non-equilibrium magnetron sputtering coating machine, evacuating; filling with inert gas, and sputtering and treating the titanium target, aluminum target, and plastic with a high negative bias voltage and a low current.

[0058] More preferably, the degree of vacuum for evacuation is 7.5×10 -6 -9.5×10 -6 torr. Since Al is extremely easy to be oxidized to aluminum oxide by oxygen in the atmosphere during deposition under low vacuum conditions, the above high vacuum conditions are sufficient to ensure the formation of a pure Al layer.

[0059] Further preferably, the high negative bias voltage is 200 - 500 V, and the low current is 0.2 - 0.4 A; the negative bias voltage power supply is a pulsed power supply with a frequency of 200 - 300 Hz and a pulse width of 400 - 600 μs. If the bias voltage is too low, it cannot play the role of ion cleaning the plastic substrate, and if it is too high, the energy of the particles hitting the plastic substrate is too high, and the plastic surface is easily heated and damaged. At the same time, if the current is too low, the target is not easily started, and if the current is too high, sputtering deposition of the film occurs during the process of depositing the film on the substrate.

[0060] In some more preferred embodiments, during sputtering, all current bias voltages are turned off every 5 - 20 minutes to cool the cavity.

[0061] 2) Deposit an Al layer on the surface of the Ti seed layer by magnetron sputtering.

[0062] In some preferred embodiments, the deposition conditions of the Al layer are as follows: facing - target sputtering deposition is used, the deposition current is 2 - 4 A, the negative bias voltage is 60 - 100 V, the Ti target current is 0.2 - 0.4 A, and the time is 2 - 10 minutes. The reasons for controlling the deposition conditions in step 2) are as follows: First, the sputtering deposition method with two targets placed opposite to each other is conducive to improving the deposition rate and the density of the Al layer. Second, if the current is too low, the number and energy of the sputtered aluminum atoms are small, and there is not enough energy to migrate to the defects when reaching the Ti layer; conversely, if the current is too high, the atomic deposition rate is too fast, resulting in an increase in surface defects. Third, if the negative bias voltage is too low, the kinetic energy of the sputtered particles decreases, and the effect of argon ion bombardment and compaction of the film weakens, but if the argon ion bombardment energy on the film is too high, the surface roughness of the film increases. Finally, if the deposition time is too short, the density of the film is low and light is easily transmitted through the film; if the deposition time is long, on the one hand, the substrate is easily heated and damaged, and on the other hand, the film growth changes from layer - by - layer growth to island - like growth, increasing the roughness.

[0063] 3) Deposit a TiN layer on the surface of the Al layer by magnetron sputtering.

[0064] In some preferred implementation cases, the deposition conditions for depositing the TiN layer are: 20-40sccm of argon and 5-10sccm of nitrogen are introduced, the Ti target deposition current is 1.5-2.5A, the Ti target negative bias voltage is 60-100V, the Al target current is 0.2-0.4A, and the deposition time is 10-30min. The deposition conditions of step 3) are controlled as follows: first, the nitrogen flow rate is controlled to 5-10sccm, because a lower nitrogen flow rate will increase the Ti atom content in the TiN layer and reduce the purity of the TiN layer; while a higher nitrogen flow rate will cause target poisoning, which is not conducive to the deposition process. However, if the titanium target sputtering current is too high, nitrogen molecules may be sputtered out, affecting the stable supply of nitrogen source, resulting in insufficient nitrogen content in the film, an increase in the proportion of titanium element in the titanium nitride film, and the formed film may be more biased towards metallic titanium (Ti) rather than titanium nitride (TiN). If the sputtering current is too low, the bombardment of nitrogen ions may be insufficient, the nitridation reaction may be incomplete, and the resulting film may lack sufficient nitrogen content. The final film may not be true titanium nitride (TiN), but metallic titanium (Ti) or titanium oxide, etc. Finally, too high a negative bias voltage will cause high-energy ions to bombard the film surface, which may make the surface uneven and increase the surface roughness. Especially in the early stages of film growth, too high a bias voltage will cause particle aggregation and irregular growth, which may affect the optical, electrical and mechanical properties of the film. Low negative bias voltage will reduce the bombardment intensity of ions on the film surface, resulting in the inability to effectively arrange the atoms of the film. The structure of the film may become loose and have a low density. The film formed in this way has poor mechanical properties (such as hardness and wear resistance) and may appear fragile and easy to peel off.

[0065] In some more preferred embodiments, during the sputtering, all current biases are turned off every 5-30 minutes of sputtering to allow the chamber to cool down.

[0066] 4) Depositing a TiAlN layer on the surface of the TiN layer by magnetron sputtering.

[0067] In some preferred embodiments, the deposition conditions of the TiAlN layer are as follows: introduce 20 - 40 sccm of argon gas and 5 - 10 sccm of nitrogen gas; the deposition current of the Ti target is 1.5 - 2.5 A, and the negative bias voltage of the Ti target is 60 - 100 V; the deposition current of the Al target is 1 - 2 A, and the deposition time is 5 - 15 min. The reason for controlling the deposition conditions in step 4) as above is that TiAlN can vary between two materials with different optical properties: TiN is a metallic conductive material with free electrons that can selectively absorb visible light, while AlN is a dielectric material transparent in the visible part of the spectrum. Therefore, by adjusting the ratio between Ti and Al, the optical constants of AlTiN can be adjusted between the metallic and dielectric properties of the material. TiAlN with a lower Al content is not very suitable for interference colors because too much light is easily absorbed.

[0068] In some more preferred embodiments, during sputtering, turn off all current biases every 5 - 15 min to cool the cavity.

[0069] 5) Deposit an AlN layer on the surface of the TiAlN layer by magnetron sputtering.

[0070] In some preferred embodiments, the deposition conditions of the AlN layer are as follows: introduce 20 - 40 sccm of argon gas and 5 - 10 sccm of nitrogen gas; the deposition current of the Al target is 1 - 2 A, the negative bias voltage of the Al target is 60 - 100 V, and the deposition time is 20 - 180 min. The reason for controlling the deposition conditions in step 5) as above is that control the argon gas flow rate at 5 - 15 sccm because after the deposition ends, the temperature in the cavity is slightly high, and introducing a small amount of argon gas can prevent the surface of the film from oxidizing. The ratio of nitrogen gas to argon gas needs to be strictly controlled. Although nitrogen gas can increase the formation of AlN, too much nitrogen gas will cause the nitriding reaction to be too intense, generating too many nitrogen ions, and these nitrogen ions may cause excessive sputtering of the aluminum target material, reducing the deposition rate of aluminum. In addition, too high a nitrogen concentration may lead to too high a nitrogen content in the film, forming pores, cracks or other defective structures, affecting the density and mechanical properties of the film. Too little nitrogen gas may cause aluminum atoms to not react with enough nitrogen molecules, resulting in too high an aluminum content in the deposited film, which may lead to the deposition of aluminum metal phase (instead of aluminum nitride), or the formation of non-ideal phases such as aluminum oxide. If the argon gas concentration is too high, relatively speaking, the nitrogen gas concentration will be lower, which may cause incomplete reaction between aluminum atoms and nitrogen atoms, inhibit the film formation process of aluminum nitride, and ultimately affect the nitriding degree of the film, and even may obtain a film of metallic aluminum. If the argon gas concentration is too low, the density of the working gas is low, the deposition rate is slow, and the film density difference.

[0071] In some more preferred embodiments, during sputtering, turn off all current biases every 5 - 30 min to cool the cavity.

[0072] Specific examples and comparative examples.

[0073] Comparative Example 1 (silvery white thin film)

[0074] (1) Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, the substrate was ultrasonically cleaned with isopropyl alcohol and deionized water for 15 min, dried by cold and hot air blowing and in a hot oven (temperature 70 °C, time 180 min), and then fixed on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough evacuation by a mechanical pump, the vacuum was pumped to 8.5×10 -6 torr.

[0075] (2) At room temperature, the working gas argon was introduced with a flow rate of 30 sccm. The turntable rotation speed was set at 4 r / min, the frequency of the pulsed bias power supply was set at 250 Hz, and the pulse width was set at 500 μs. First, the target and the substrate were sputter-cleaned with a negative bias of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and to activate the plastic substrate surface by plasma.

[0076] (3) The current for sputtering the Al target with the opposing target was changed to 2.71 A and the negative bias to 80 V. A highly reflective Al layer was sputtered on the plastic for 3 min with a thickness of 25 nm. After the sputtering process was completed, the current and voltage were turned off, the argon gas flow rate was adjusted to 10 sccm for 15 min, and then the coating process was turned off. After the chamber cooled to room temperature, it was taken out.

[0077] Example 1 (blue-violet composite thin film)

[0078] (1) Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, the substrate was ultrasonically cleaned with isopropyl alcohol and deionized water for 15 min, dried by cold and hot air blowing and in a hot oven (temperature 70 °C, time 180 min), and then fixed on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough evacuation by a mechanical pump, the vacuum was pumped to 8.5×10 -6 torr.

[0079] (2) At room temperature, the working gas argon was introduced with a flow rate of 30 sccm. The turntable rotation speed was set at 4 r / min, the frequency of the pulsed bias power supply was set at 250 Hz, and the pulse width was set at 500 μs. First, the target and the substrate were sputter-cleaned with a negative bias of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and to activate the plastic substrate surface by plasma.

[0080] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm, and then adjust the current of the Ti target back to 0.3 A.

[0081] (4) Change the current of the opposing target sputtering the Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. Without breaking the vacuum, turn off the currents of all targets. After the cavity cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the low current of the Al target to 0.3 A, and sputter a TiN layer for 20 min with a thickness of 48 nm. Then turn off the currents and biases of all targets.

[0082] (5) After the cavity cools for 1 h, introduce 30 sccm of argon and 7 sccm of nitrogen. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer for 10 min with a thickness of 45 nm. Lower the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer for 37 min with a thickness of 37 nm. During sputtering, turn off all current biases every 20 min of sputtering the AlN layer, and let the cavity cool for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm for 15 min, and then turn off the coating program. After the cavity cools to room temperature, take out the sample.

[0083] Example 2 (Forest Green Composite Film)

[0084] (1) Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, ultrasonically clean the substrate in isopropyl alcohol and deionized water for 15 min, dry it with cold and hot air blowing and in a hot oven (temperature 70 °C, time 180 min), and then fix it on the base stage of a closed unbalanced magnetron sputtering equipment (UDP - 650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0085] (2) Under room temperature conditions, introduce the working gas argon with a flow rate of 30 sccm, set the turntable rotation speed to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and the plasma activation of the plastic substrate surface.

[0086] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm, and then adjust the current of the Ti target back to 0.3 A.

[0087] (4) Change the current of the Al target (opposite target) to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. Without breaking the vacuum, turn off the currents of all targets. After the cavity cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the current of the low Al target to 0.3 A, and sputter a TiN layer for 20 min with a thickness of 48 nm. Then turn off the currents and biases of all targets.

[0088] (5) After the cavity cools for 1 h, introduce 30 sccm of argon and 7 sccm of nitrogen. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer for 10 min with a thickness of 45 nm. Reduce the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer for 61 min with a thickness of 61 nm. During sputtering, turn off all current biases every 20 min of sputtering the AlN layer, and let the cavity cool for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm for 15 min, and then turn off the coating program. After the cavity cools to room temperature, take out the sample.

[0089] Example 3 (Yellow-green composite film)

[0090] (1) Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, ultrasonically clean the substrate in isopropyl alcohol and deionized water for 15 min, dry it with cold and hot air blowing and in a hot oven (temperature 70 °C, time 180 min), and then fix it on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0091] (2) Under room temperature conditions, introduce the working gas argon with a flow rate of 30 sccm, set the rotation speed of the turntable to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and activate the surface of the plastic substrate by plasma.

[0092] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm, and then adjust the current of the Ti target back to 0.3 A.

[0093] (4) Change the current of the counter target Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. Without breaking the vacuum, turn off the currents of all targets. After the cavity cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the low current of the Al target to 0.3 A, and sputter a TiN layer for 20 min with a thickness of 48 nm. Then turn off the currents and biases of all targets.

[0094] (5) After the cavity cools for 1 h, introduce argon at 30 sccm and nitrogen at 7 sccm. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer for 10 min with a thickness of 45 nm. Lower the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer for 75 min with a thickness of 75 nm. During sputtering, turn off all current biases every 20 min of sputtering the AlN layer, and the cavity cools for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm for 15 min, and then turn off the coating program. After the cavity cools to room temperature, take it out.

[0095] Example 4 (Golden Composite Film)

[0096] (1) Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, the substrate is ultrasonically cleaned with isopropyl alcohol and deionized water for 15 min, dried by cold and hot air blowing and in a hot oven (temperature 70 °C, time 180 min), and then fixed on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0097] (2) At room temperature, introduce the working gas argon with a flow rate of 30 sccm, set the turntable rotation speed to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and the plasma activation on the surface of the plastic substrate.

[0098] (3)Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm, and then adjust the current of the Ti target back to 0.3 A.

[0099] (4)Change the current of the opposing Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. Without breaking the vacuum, turn off the currents of all targets. After the cavity cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the low current of the Al target to 0.3 A, and sputter a TiN layer for 20 min with a thickness of 48 nm. Then turn off the currents and biases of all targets.

[0100] (5)After the cavity cools for 1 h, introduce argon at 30 sccm and nitrogen at 7 sccm. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer for 10 min with a thickness of 45 nm. Lower the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer for 110 min with a thickness of 110 min. During sputtering, turn off all current biases every 20 min of AlN layer sputtering, and let the cavity cool for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm for 15 min, and then turn off the coating program. After the cavity cools to room temperature, take out the sample.

[0101] Example 5 (Orange-yellow composite film)

[0102] (1)Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, ultrasonically clean the substrate with isopropyl alcohol and deionized water for 15 min, dry it with cold and hot air blowing and in a hot oven (temperature 70 °C, time 180 min), and then fix it on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0103] (2)Under room temperature conditions, introduce the working gas argon with a flow rate of 30 sccm, set the turntable rotation speed to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and activate the plastic substrate surface by plasma.

[0104] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm, and then adjust the current of the Ti target back to 0.3 A.

[0105] (4) Change the current of the counter target Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. Without breaking the vacuum, turn off the currents of all targets. After the cavity cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the low current of the Al target to 0.3 A, and sputter a TiN layer for 20 min with a thickness of 48 nm. Then turn off the currents and biases of all targets.

[0106] (5) After the cavity cools for 1 h, introduce argon at 30 sccm and nitrogen at 7 sccm. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer for 10 min with a thickness of 45 nm. Lower the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer for 130 min with a thickness of 130 nm. During sputtering, turn off all current biases every 20 min of sputtering the AlN layer, and let the cavity cool for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm for 15 min, and then turn off the coating program. After the cavity cools to room temperature, take out the sample.

[0107] Example 6 (Iridescent Composite Film)

[0108] (1) Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, the substrate is ultrasonically cleaned with isopropyl alcohol and deionized water for 15 min, dried by cold and hot air blowing and in a hot oven (temperature 70 °C, time 180 min), and then fixed on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0109] (2) Under room temperature conditions, introduce the working gas argon with a flow rate of 30 sccm, set the turntable rotation speed to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and activate the plastic substrate surface by plasma.

[0110] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm, and then adjust the current of the Ti target back to 0.3 A.

[0111] (4) Change the current of the opposing Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. Without breaking the vacuum, turn off the currents of all targets. After the cavity cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the low current of the Al target to 0.3 A, and sputter a TiN layer for 20 min with a thickness of 48 nm. Then turn off the currents and biases of all targets.

[0112] (5) After the cavity cools for 1 h, introduce 30 sccm of argon and 7 sccm of nitrogen. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer for 10 min with a thickness of 45 nm. Lower the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer for 180 min with a thickness of 180 nm. During sputtering, turn off all current biases every 20 min of AlN layer sputtering, and let the cavity cool for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm for 15 min, then turn off the coating program, and take it out after the cavity cools to room temperature.

[0113] Example 7 (Violet-blue composite film)

[0114] (1) Cut the PS board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, ultrasonically clean the substrate with absolute ethanol and deionized water for 15 min, dry it with cold and hot air blowing and in a hot oven (temperature 60 °C, time 180 min), and then fix it on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0115] (2) At room temperature, introduce the working gas argon with a flow rate of 30 sccm, set the turntable rotation speed to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and the plasma activation on the surface of the plastic substrate.

[0116] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm. Deposit it in two times, with each time being 7 min. Then turn off the current of the Ti target and cool the chamber for 1 h.

[0117] (4) Change the current of the counter target Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. Under the condition of not breaking the vacuum, turn off the currents of all targets. After the chamber cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the low current of the Al target to 0.3 A, and sputter a TiN layer for 20 min with a thickness of 48 nm. Deposit it in two times, with each time being 10 min. Then turn off the currents and biases of all targets.

[0118] (5) After the chamber cools for 1 h, introduce argon at 30 sccm and nitrogen at 7 sccm. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer for 10 min with a thickness of 45 nm. Lower the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer for 31 min with a thickness of 31 nm. During sputtering, turn off all current biases every 9 min of sputtering the AlN layer and cool the chamber for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm, and keep it for 15 min. Then turn off the coating program and take it out after the chamber cools to room temperature.

[0119] Example 8 (Sky-blue composite film)

[0120] (1) Cut the PS board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, ultrasonically clean the substrate with absolute ethanol and deionized water for 15 min, dry it with cold and hot air blowing and in a hot oven (temperature of 60 °C, time of 180 min), and then fix it on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0121] (2) Under room temperature conditions, introduce the working gas argon with a flow rate of 30 sccm, set the turntable rotation speed to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and activate the plasma on the surface of the plastic substrate.

[0122] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer with a sputtering time of 14 min and a thickness of 55 nm. Deposit it in two times, with each time being 7 min. Then, turn off the current of the Ti target and cool the chamber for 1 h.

[0123] (4) Change the current of the opposing Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer with a sputtering time of 3 min and a thickness of 25 nm. Without breaking the vacuum, turn off the currents of all targets. After the chamber cools for 1 h, introduce argon and nitrogen with flow rates of 30 sccm and 7 sccm respectively. Turn on the current of the Ti target to 2.1 A and the current of the low Al target to 0.3 A, and sputter a TiN layer with a sputtering time of 20 min and a thickness of 48 nm. Deposit it in two times, with each time being 10 min. Then, turn off the currents and bias voltages of all targets.

[0124] (5) After the chamber cools for 1 h, introduce argon at 30 sccm and nitrogen at 7 sccm. At the same time, turn on the current of the Al target to 1.56 A and the current of the Ti target to 2.1 A, with a bias voltage of -80 V, and sputter the TiAlN layer with a sputtering time of 10 min and a thickness of 45 nm. Lower the current of the Ti target to 0.3 A, turn on the current of the Al target to 1.56 A, and sputter the AlN layer with a sputtering time of 41 min and a thickness of 41 nm. During sputtering, turn off all current and bias voltages every 9 min of sputtering the AlN layer and cool the chamber for 1 h. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10 sccm, and keep it for 15 min. Then, turn off the coating program and take it out after the chamber cools to room temperature.

[0125] Example 9 (Silver-white composite film)

[0126] (1) Cut the PC board into small round pieces with a diameter of 3 cm and a thickness of 3 mm as the substrate. Subsequently, ultrasonically clean the substrate with isopropyl alcohol and deionized water for 15 min respectively, dry it with cold and hot air blowing and in a hot oven (temperature: 70 °C, time: 180 min), and then fix it on the base stage of a closed unbalanced magnetron sputtering device (UDP-650). After rough pumping the vacuum with a mechanical pump, use an oil diffusion pump to pump the vacuum degree to 8.5×10 -6 torr.

[0127] (2) Under room temperature conditions, introduce the working gas argon with a flow rate of 30 sccm, set the rotation speed of the turntable to 4 r / min, set the frequency of the pulsed bias power supply to 250 Hz and the pulse width to 500 μs. First, sputter and clean the target and the substrate with a negative bias voltage of 200 V and a low current of 0.3 A for 10 min to remove the oxide layers on the surfaces of the Ti target and the Al target and activate the plasma on the surface of the plastic substrate.

[0128] (3) Change the current on the Ti target to 2.47 A and the negative bias voltage to 80 V. First, sputter the Ti seed layer for 14 min with a thickness of 55 nm, and then adjust the current of the Ti target back to 0.3 A.

[0129] (4) Change the current of the counter target Al target to 2.71 A and the negative bias voltage to 80 V. Sputter a high-reflection Al layer on the Ti seed layer for 3 min with a thickness of 25 nm. After the sputtering process is completed, turn off the current and voltage, adjust the argon gas flow rate to 10 sccm for 15 min, and then turn off the coating program. After the chamber cools down to room temperature, take out the sample.

[0130] Performance Testing and Characterization

[0131] Figure 1 is a schematic structural diagram of the color-changing composite thin film of the present invention. As Figure 1 shown, the thin film structure is a multi-layer film structure. The Ti seed layer is used as an adhesive layer to improve the film-substrate adhesion; the Al layer is used as a reflective layer to improve the color brightness. If a simple semi-transparent AlN layer is deposited, visible light is difficult to be reflected to the top layer, and the effect of thin film interference cannot be generated. When the high-absorbing medium TiAlN layer is deposited on the thinner TiN, a TiAlN-TiN absorber is constructed. Then, when the ultra-thin semi-transparent dielectric layer AlN layer is deposited on the TiAlN-TiN absorber, different colors can be obtained. The results show that the color-changing composite thin film designed by the present invention has a multi-layer film structure, and the adhesion can be improved by the Ti seed layer, the color brightness of the sample can be improved by the Al layer, and multiple colors can be obtained through the thin film interference effect of the multi-layer thin films.

[0132] Figure 2 are the reflection spectra of Examples 1, 2, 3, 4, 5 and 6 in the wavelength range of 380 - 800 nm. As Figure 2 shown, the maximum reflectivities of Examples 1, 2, 3, 4, 5 and 6 are obtained at 450 nm, 502 nm, 552 nm, 598 nm and 757 nm respectively, and the colors are blue-violet, forest green, yellow-green, golden yellow, orange-yellow and rose-red respectively. The maximum reflectivity can reach 68%, which indicates that the composite thin film on the PC surface has good color brightness. In Examples 1, 2, 3, 4, 5, 6, only the thickness of the topmost AlN layer is different, and the color is generated by the thin film interference of the top layer. The results show that multiple colors can be obtained through the thin film interference of the multi-layer film structure, and the color changes with the thickness of the topmost AlN layer.

[0133] Figure 3 are the CIE chromaticity diagrams of Examples 1, 2, 3, 4, 5 and 6. As Figure 3As shown, the fabricated sample colors almost cover the entire color gamut. As the deposition time of the top AlN layer increases, the thickness of the AlN layer increases, and the color changes in the direction of the blue arrow in the chromatogram, that is, from purple to red. This color change is a typical thin-film interference behavior. The results show that the composite film fabricated with the three-layer thin-film structure has the advantages of high chromaticity and wide color gamut.

[0134] Figure 4 Digital photos of the composite film on the plastic surface: (a) Example 1, (b) Example 2, (c) Example 3, (d) Example 4, (e) Example 5, and (f) Example 6. As Figure 4 shown, the color of Example 1 is blue-violet, the color of Example 2 is forest green, the color of Example 3 is yellow-green, the color of Example 4 is golden yellow, the color of Example 5 is orange-yellow, and the color of Example 6 is rose red. These all correspond to Curve 3 in the reflection spectrum. The results show that the composite film fabricated with the multi-layer thin-film structure has bright colors and high color saturation.

[0135] Figure 5 Digital photos of the iridescent composite film sample in Example 6 at different viewing angles: (a) 0 ° °, (b) 22 ° °, (c) 45 ° °, (d) 68 ° °, and (e) 90 ° °. As Figure 5 shown, when the shooting angle changes from 0 ° ° to 90 ° °, the color of the sample changes from rose red to golden yellow. The color will change with the observer's viewing angle, showing an iridescent effect, and the colors before and after the change have high brightness and high color saturation. This is because the thickness of the top AlN layer directly determines the optical path difference. When the thickness of the AlN layer increases, the range of the interference color change will also become larger. Because a thicker AlN layer requires a larger optical path difference to reach the interference condition, different angle changes will more significantly affect the observed color. The results show that the color of the sample fabricated with the multi-layer film structure will show an iridescent effect as the thickness of the top AlN layer increases.

[0136] Figure 6 SEM images of the high-reflection aluminum film: (a) Comparative Example 1 and (b) Example 9. As Figure 6As shown, individual fine grains on the surface layer of the single-layer aluminum film (Al) in Comparative Example 1 are clearly visible, the grain boundaries are obvious, and there are obvious changes in light and dark contrast. In contrast, the aluminum film with a titanium seed layer in Example 9 has a smooth and dense surface, the grain boundaries are not obvious, and there are no obvious changes in light and dark contrast. This indicates that the aluminum film in Comparative Example 1 grows in accordance with the Volmer-Weber mode, that is, the initial growth mode is isolated islands, which leads to an increase in the surface roughness of the aluminum film. In Example 9, due to the strong bond energies of Al-Al (264 kJ / mol) and Ti-Al (263 kJ / mol), the growth mode of the aluminum film changes from island growth to layer-island combined growth mode, resulting in a decrease in surface roughness. This is also related to the surface free energy of the aluminum (1.160 J / m 2 ) film deposition surface. The surface free energy of titanium (1.989 J / m 2 ) is significantly higher than that of the original polycarbonate (0.38 J / m 2 ). In Example 9, aluminum is deposited on the titanium seed layer with high surface free energy, the diffusion of aluminum atoms on the substrate is reduced, and there are more nucleation sites. The results show that by adding a titanium seed layer, a more layered growth mechanism is induced, the surface roughness of the thin film is reduced, the number of nucleation sites increases, the diffusion of aluminum atoms is reduced, and the reflectivity of the thin film is improved.

[0137] Figure 7 Figure (a) shows the SEM image of the iridescent composite thin film in Example 6. As Figure 7 shown, the surface of the AlN layer in (a) of Example 6 is very smooth, and almost no defects such as pinholes, cracks or large particles can be seen in the whole area. This smooth surface structure is beneficial for the coating to reflect visible light. The surface morphology of the AlN layer in (b) of Example 6 after being magnified at a high magnification shows that many small particles are evenly distributed on the thin film surface. The particle size is uniform, the average size is about 37 nm, and the arrangement is regular and uniform, indicating that the thin film structure is very dense. By measuring with Nano Measurer software, the particle size range of the AlN grains in Example 6 is 95 - 135 nm. The results show that the AlN layer prepared by magnetron sputtering has a smooth surface, a dense structure, good crystallization, uniform thickness, and meets the conditions for thin film interference with visible light.

[0138] Figure 8 Figure (a) shows the optical picture of Example 5 after the Rockwell hardness test. As Figure 8 shown, after the sample is pressed by a Rockwell hardness tester, no obvious peeling is observed under the microscope. Magnifying the local surface, only very fine radial cracks are observed, indicating that the multi-layer film structure has very good film-substrate adhesion with the plastic substrate. The results show that the addition of the Ti seed layer provides a transition layer between the metal nitride film and the plastic substrate, greatly improving the film-substrate adhesion.

[0139] Figure 9For Example 7 ( Figure 9 left sample) and Example 8 ( Figure 9 right sample), digital photos of the colored composite films on the PS plastic surface are shown. As Figure 9 shown, the color of the sample in Example 7 ( Figure 9 left sample) is purple-blue, and the sample in Example 8 ( Figure 9 right sample) is sky-blue. The coating on the PS plastic surface is dense and smooth, without obvious defects, with bright and vivid colors and high color saturation. The results show that this preparation method of the colored composite film is applicable to different plastics, and the colors produced still have high color saturation.

[0140] Table 1 shows the microhardness values of the original PC, PS, and Examples 1, 2, 3, 4, 5, 6, 7, and 8. On a Vickers hardness testing machine, a load of 0.098 N and a square pyramid diamond indenter with a relative angle of 136° are used to press into the surface of the sample. After maintaining the specified time, the length of the diagonal of the indentation is measured, and then the hardness (HV) is calculated according to the formula.

[0141]

[0142] F = load (N)

[0143] S = indentation surface area (mm 2 )

[0144] α = included angle of the opposite surface of the indenter = 136°

[0145] d = average length of the diagonal of the indentation (mm)

[0146] It can be seen from the data in Table 1 that the hardness of the original PC and PS is 14.51 kgf / mm 2 and 23.55 kgf / mm 2 , respectively, while the hardness of the PC plastic surface composite films in Examples 1, 2, 3, 4, 5, and 6 is 17.16 kgf / mm 2 , 17.36 kgf / mm 2 , 17.56 kgf / mm 2 , 17.77 kgf / mm 2 , 18.47 kgf / mm 2 , and 19.97 kgf / mm 2 , respectively, all higher than the hardness value of the original PC. The hardness of the PS surface composite films in Examples 7 and 8 is 25.68 kgf / mm 2 and 26.13 kgf / mm 2 , respectively, also higher than the hardness value of the original PS. This indicates that depositing the composite film can increase the hardness value of the plastic surface and has a good protective effect on plastic products.

[0147] Table 1

[0148]

[0149] In the present invention, the raw materials and equipment used, unless otherwise specified, are common raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0150] The above are only preferred embodiments of the present invention and do not impose any limitation on the present invention. Any simple modification, change and equivalent transformation made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A colorful composite film with high hardness and high bonding strength on a plastic surface, characterized in that: The method comprises a Ti seed layer, an Al layer, a TiN layer, a TiAlN layer and an AlN layer which are sequentially deposited on the plastic surface by magnetron sputtering; The thickness of the Ti seed layer was 55 nm, and the deposition conditions were as follows: deposition current 2.47 A, negative bias 80 V, and time 14 min; The thickness of the Al layer is 25nm, the growth mode is layer-island combined growth mode, and the surface roughness is less than 3nm; the deposition conditions are: target sputtering deposition, deposition current 2.71A, negative bias 80V, time 3min; The thickness of the TiN layer is 48 nm; The thickness of the TiAlN layer is 45 nm; The AlN grain size in the AlN layer is 80-150 nm; the thickness of the AlN layer is 180 nm; the deposition conditions are: argon flow rate 30 sccm, nitrogen flow rate 7 sccm; Al target deposition current 1.56 A, Al target negative bias 80 V, and deposition time 180 min.

2. The plastic surface high hardness and high bonding strength colorful composite film according to claim 1, characterized in that: The plastic is one or more of polycarbonate, polymethyl methacrylate, polyphenylene sulfide, polystyrene and polyethylene terephthalate.

3. The colorful composite film with high hardness and high bonding strength on plastic surface according to claim 2, characterized in that: The plastic is polycarbonate or polystyrene.

4. A method for preparing a colorful composite film with high hardness and high bonding strength on a plastic surface according to any one of claims 1 to 3, characterized in that include: 1) Depositing a Ti seed layer on the plastic surface by magnetron sputtering; 2) depositing an Al layer on the surface of the Ti seed layer by magnetron sputtering; 3) depositing a TiN layer on the surface of the Al layer by magnetron sputtering; 4) depositing a TiAlN layer on the surface of the TiN layer by magnetron sputtering; 5) Depositing an AlN layer on the surface of the TiAlN layer by magnetron sputtering.

5. The preparation method according to claim 4, characterized in that: In step 1), before depositing the Ti seed layer, the plastic surface is degreased, decontaminated and dried; the oxide layer on the surface of the titanium target and the aluminum target is removed by magnetron sputtering under inert conditions, and the plastic is surface plasma activated.

6. The preparation method according to claim 5, characterized in that: In step 1), the plastic surface is first ultrasonically cleaned with chemical reagents and water to remove oil and dirt, and then blown and dried with cold and hot air.

7. The preparation method according to claim 6, characterized in that: In step 1), the chemical reagent is anhydrous ethanol, isopropanol or acetone; the drying temperature is 50-80°C and the drying time is 120-240 minutes.

8. The preparation method according to claim 4, characterized in that: In step 3), the deposition conditions of the TiN layer are: 20-40 sccm of argon and 5-10 sccm of nitrogen, Ti target deposition current of 1.5-2.5 A, Ti target negative bias of 60-100 V, Al target current of 0.2-0.4 A, and deposition time of 10-30 min.

9. The preparation method according to claim 4, characterized in that: In step 4), the deposition conditions of the TiAlN layer are: 20-40 sccm of argon and 5-10 sccm of nitrogen; Ti target deposition current is 1.5-2.5A, Ti target negative bias voltage is 60-100V; Al target deposition current is 1-2A, and deposition time is 5-15min.

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