High-adhesion plastic reflector and preparation method thereof

Abstract

The invention relates to the technical field of coating, and discloses a high-adhesion plastic reflector and a preparation method thereof. The high-adhesion plastic reflecting mirror comprises a plastic substrate, and a TiAlN bonding layer, a Ti seed crystal layer and an Al reflecting layer which are sequentially deposited on the surface of the plastic substrate, c-N bonds, (C-O)-(Ti, Al, N) bonds and C-Ti and C-Al bonds are arranged between the TiAlN bonding layer and the plastic substrate, then, the chemical compatibility between TiAlN and the Ti seed crystal layer is high, Ti atoms can be slightly diffused into the TiAlN bonding layer, N atoms can also be slightly diffused into the Ti seed crystal layer, a thin and compact Ti-N reaction transition layer and a Ti-Ti metal bonding layer are formed, the adhesive force of the Ti layer can be greatly improved, and finally, the bonding strength of the Ti layer is improved. And the Al reflecting layer and the Ti seed crystal layer are tightly connected through a metal bond Ti-Al, so that strong adhesive force is obtained. According to the method, TiAlN, Ti and Al are sequentially deposited on the surface of the plastic substrate, the TiAlN located on the bottom layer can play a role of a bonding layer, and the TiAlN and the plastic surface can form a complex chemical bonding structure, so that the bonding force is improved.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a high-adhesion plastic reflector and its preparation method. Background Technology

[0002] Currently, most mirrors on the market are made by coating a metallic reflective layer onto clean, oil-free glass. However, the inherent properties of glass result in heavy and fragile mirrors, significantly increasing the cost of transportation and installation in daily life. Plastic, a polymer compound, possesses excellent properties such as high hardness, light weight, low cost, and high durability. Using plastic to replace glass in the manufacture of highly reflective mirrors not only makes them lighter but also less prone to breakage during everyday transportation.

[0003] High-reflectivity mirrors are typically fabricated by depositing metallic reflective materials onto a substrate surface. Based on this, there are many methods for fabricating plastic high-reflectivity mirrors, such as vacuum evaporation, spraying, or magnetron sputtering to deposit a reflective layer on one side of glass or plastic. Compared to traditional vacuum evaporation, magnetron sputtering is a physical vapor deposition technique commonly used for thin film deposition, capable of producing thin films with excellent crystallinity, density, and precise compositional control. The reflective layer is usually a metallic reflective material. Some researchers have experimented with using silver as the reflective metal because it has a high reflectivity of 96% in the 380-800 nm range. However, silver-based mirrors are prone to degradation under environmental conditions, have poor adhesion to some substrates, and lose their gloss due to sulfidation and chlorination, which greatly limits their application in practical production. Although the reflectivity of metallic Al is not as high as silver (85-90% in the 380-800 nm range), it is cheaper and more weather-resistant.

[0004] The durability of coatings largely depends on their ability to adhere to a substrate under mechanical stress. However, due to the significant differences in properties between metals and plastic substrates, the adhesion between metal layers and plastic substrates is weak, and metal layers are prone to detachment. One method to improve the adhesion between metal layers and plastic substrates is to increase the roughness of the bonding surface of the plastic substrate through sandblasting. However, sandblasting can only slightly improve the adhesion through mechanical interlocking, and the roughened surface after sandblasting also leads to a decrease in reflectivity. Studies have found that chemical bonding between different interfaces is far stronger than simple physical bonding. For example, patent US20120114950A1 discloses a method to improve the adhesion between metal and plastic by depositing one of magnesium, zirconium, Al, and Ti on a photosensitive plastic substrate activated by a UV lamp. However, the number of active free radicals -O· and -CO· generated after such weak UV light is small, making it difficult to significantly improve the adhesion, and this treatment can only be performed on photosensitive plastics, which limits its application range.

[0005] In the preliminary tests, the applicant found that the Al film produced by magnetron sputtering had poor adhesion to the plastic substrate. Furthermore, directly depositing the Al film on the plastic substrate not only resulted in high surface roughness, but also significantly reduced the reflectivity and lifespan of the mirror due to internal defects and pinhole-like flaws. Although adding a Ti seed layer could improve these defects and increase reflectivity, the coating still peeled off after multiple tape peel tests following the cross-cut test, failing to achieve perfect adhesion.

[0006] Against this backdrop, there is an urgent need for a non-destructive method for treating plastic surfaces that can generate a highly adhesive interface through chemical bonding at the metal / plastic interface without affecting the surface roughness of the plastic. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a high-adhesion plastic reflector and its preparation method. In this invention, TiAlN, Ti, and Al are sequentially deposited onto the surface of a plastic substrate. The TiAlN layer at the bottom acts as an adhesive layer, forming a complex chemical adhesive structure with the plastic surface, thereby improving the bonding strength.

[0008] The specific technical solution of this invention is as follows: First, the present invention provides a high-adhesion plastic reflector, which includes a plastic substrate and a TiAlN adhesive layer, a Ti seed layer and an Al reflective layer sequentially deposited on the surface of the plastic substrate; the TiAlN adhesive layer and the plastic substrate have C-N bonds, (C-O)-(Ti,Al,N) bonds and C-Ti,C-Al bonds.

[0009] This invention involves sequentially depositing TiAlN, Ti, and Al onto the surface of a plastic substrate. The invention reveals that the TiAlN layer at the bottom acts as an adhesive layer, forming a complex chemical adhesive structure with the plastic surface to improve bonding strength. Simultaneously, this high-hardness ceramic nitride underlayer also enhances the scratch resistance of the plastic substrate. Furthermore, the Ti seed layer in the middle effectively reduces the surface roughness of the Al reflective layer, preventing pinholes and other defects, thereby improving specular reflectivity. Specifically: Regarding the enhancement of interfacial adhesion: In previous studies, the applicant found that depositing a Ti seed layer on the surface of a plastic substrate could improve the adhesion between the plastic and the coating to some extent. However, after multiple tape peel tests following cross-cut adhesion, the coating still peeled off, failing to achieve perfect adhesion. Therefore, this invention deposits TiAlN on the surface of a plastic substrate. Taking a polycarbonate (PC) plastic substrate as an example, the combination of highly reactive N and Ti in TiAlN, along with selectively reactive Al, leads to complex cross-linking and mixing of interfacial groups, significantly improving the chemical bond coverage at the PC | TiAlN interface. Compared to depositing a Ti seed layer first, the PC | Ti interface, while exhibiting strong reactivity and forming most interfacial bonds (i.e., (C-O)-Ti and C-Ti bonds), lacks high-strength C-N bonds. This not only reduces the interfacial bond density but also directly results in weak cross-linking of the PC | Ti interfacial groups. Experimental results show significant differences in atomic reactivity and interface formation among different adhesive layers. Compared to the PC | Ti interface, the PC | TiAlN interface exhibits the highest interfacial bond density. The interactions of numerous C-N bonds at the interface and the strong cross-linking of interfacial groups promote a stronger interface formation in PC|TiAlN, achieving the highest density of interfacial bonds and the strongest interface. The subsequently deposited Ti seed layer exhibits strong chemical compatibility with TiAlN; Ti atoms can slightly diffuse into the TiAlN binder layer, and N atoms can also slightly diffuse into the Ti seed layer, forming a thin and dense Ti-N reaction transition layer and a Ti-Ti metallic bonding layer. This significantly improves the adhesion of the AlTi layer. Subsequently, the Al reflective layer and the Ti seed layer are tightly connected through metallic Ti-Al bonds, resulting in an extremely strong adhesion of the prepared coating.

[0010] Regarding the improvement of reflectivity: First, the sputtering threshold energy of the Ti seed layer is higher than that of Al, and the chemical compatibility between the Ti seed layer and TiAlN is strong. On the TiAlN substrate, a more crystallinity and denser Ti seed layer can be obtained. This is due to the Al-Al bond (264 kJ mol). −1 ) and Ti-Al bonds (263 kJ mol) −1 The similar dissociation energies of both lead to the Al layer growing in an island-bonding mode and reducing surface roughness. Finally, the Al grain size deposited on the Ti seed layer is larger than that of the sample without a Ti seed layer. Larger Al grains result in fewer grain boundaries, weakened grain boundary plasmon resonance, and reduced light scattering, thus increasing reflectivity. This high-reflectivity film can achieve a reflectivity exceeding 91% in the visible light range, while a single-layer Al film fabricated using the same process only achieves 84% ​​visible light reflectivity.

[0011] Preferably, the thickness of the TiAlN bonding layer is 50-100 nm; the thickness of the Ti seed layer is 20-80 nm; and the thickness of the Al reflective layer is 70-100 nm.

[0012] The present invention further optimizes the thickness of the above-mentioned layers. If the TiAlN bonding layer is too thin, the number of bonds between it and the plastic substrate will decrease, the adhesion will decrease, and thus the stability of the coating structure will be compromised. On the other hand, if the TiAlN bonding layer or Ti seed layer is too thick, the surface roughness will increase, which will increase the surface roughness of the Al layer subsequently deposited on the coating, thereby leading to a decrease in reflectivity.

[0013] Preferably, the Al reflective layer is grown in a layer-island hybrid mode, with Al grain size ≥ 100 nm and surface roughness < 2 nm.

[0014] Preferably, the TiAlN binder layer, Ti seed layer and Al reflective layer are deposited sequentially by magnetron sputtering.

[0015] Preferably, the plastic substrate is selected from one or more of polycarbonate (PC), polymethyl methacrylate (PMMA), polyphenylene sulfide (PPS), polystyrene (PS), and polyethylene terephthalate (PET); more preferably, it is polycarbonate (PC). PC not only has high strength and excellent heat resistance, but also good weather resistance and anti-aging properties, enabling it to be used for a long time in outdoor environments without failure.

[0016] Secondly, this invention provides a method for preparing a high-adhesion plastic reflector, which includes the following steps: 1) Cleaning treatment of the plastic substrate surface.

[0017] 2) Under inert conditions, magnetron sputtering is used to remove the oxide layer on the surface of Ti and Al targets and to activate the surface of plastic substrates by plasma.

[0018] 3) A TiAlN bonding layer was deposited on the surface of a plastic substrate by magnetron sputtering.

[0019] 4) A Ti seed layer is deposited on the surface of the TiAlN binder layer by magnetron sputtering.

[0020] 5) An Al reflective layer is deposited on the surface of the Ti seed layer by magnetron sputtering.

[0021] Preferably, in step 3), the deposition conditions of the TiAlN binder layer are as follows: the ratio of argon to nitrogen is 25-35: 4-10 sccm, the Al target current is 1.5-2.0A, the Ti target current is 2.0-3.0A, the negative bias voltage is 60-100V, and the time is 8-20min.

[0022] Too low a current results in fewer sputtered atoms with lower energy, a slower film deposition rate, and the low-energy atoms that reach the substrate cannot spontaneously migrate to surface defects. Conversely, too high a current increases the number of sputtered atoms, and the temperature inside the cavity rises sharply with the deposition time, making the plastic substrate structure easily damaged.

[0023] Preferably, in step 4), the deposition conditions of the Ti seed layer are: Ti target current of 2.0-3.0A, negative bias voltage of 60-100V, and time of 8-20min.

[0024] Preferably, in step 5), the deposition conditions of the Al reflective layer are as follows: target sputtering deposition is used, which is beneficial to improve the deposition rate and Al film density; the current is 1.0-3.0A, the negative bias voltage is 60-100V, and the time is 2-10min.

[0025] Compared with the prior art, the beneficial effects of the present invention are: (1) In this invention, TiAlN, Ti and Al are sequentially deposited onto the surface of a plastic substrate by magnetron sputtering. The TiAlN at the bottom layer can act as an adhesive layer, which can form a complex chemical adhesive structure with the plastic surface to improve the bonding force. At the same time, this high-hardness ceramic nitride bottom layer can also improve the scratch resistance of the plastic substrate.

[0026] (2) The chemical compatibility between TiAlN and Ti seed layer is strong, which can obtain Ti seed layer with higher crystallinity and denser density. At the same time, Ti atoms can diffuse slightly into TiAlN bonding layer, and N atoms can also diffuse slightly into Ti seed layer to form a thin and dense Ti-N reaction transition layer and Ti-Ti metal bonding layer, which can greatly improve the adhesion of Ti layer. After that, Al reflective layer and Ti seed layer are tightly connected by metal bond Ti-Al. It was also found that Ti seed layer can improve Al layer density, reduce Al layer surface roughness, avoid defects such as pinholes, and thus improve specular reflectivity.

[0027] (3) The plastic Al mirror of the present invention has good properties such as being strong, lightweight, low cost and highly durable. The use of the plastic mirror is not affected by transportation and installation-related issues. Attached Figure Description

[0028] Figure 1 The reflectance spectra of Comparative Example 1 and Comparative Example 2 are in the wavelength range of 380-800 nm.

[0029] Figure 2 AFM 10 × 10µm for high-adhesion PC reflectors 22D of the scanned area: (a) Comparative Example 1 and (c) Comparative 2D and 3D images: (b) Example 1 and (d) Example 2.

[0030] Figure 3 The reflection spectra of Comparative Example 2 and Example 1 are in the wavelength range of 380-800 nm.

[0031] Figure 4 SEM images of high-adhesion PC reflectors: (a) Comparative Example 2 and (b) Example 1.

[0032] Figure 5 Optical micrographs of a high-adhesion PC reflector after five tape peeling experiments: (a) Comparative Example 2, (b) Example 1 and digital photographs: (c) Comparative Example 2, (d) Example 1.

[0033] Figure 6 To test the C1s spectra of different adhesive layers and PC interfaces using XPS.

[0034] Figure 7 Planar views of a PC surface plate model visualized via VESTA: (a) the original surface and (b) the surface after deposition of different atoms of TiAlN and (c) Ti.

[0035] Figure 8 Optical micrographs of high-adhesion PC reflectors after automatic scratch testing: (a) Comparative Example 2 and (b) Example 1.

[0036] Figure 9 The relationship between the coefficient of friction and reciprocating time for the uncoated, Comparative Example 2 and Example 1 PC plastic samples is shown in (a), and their microhardness values ​​are shown in (b).

[0037] Figure 10 Digital photographs of high-adhesion PC reflectors for Comparative Example 1 (left), Comparative Example 2 (middle), and Example 1 (right). Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments.

[0039] General Implementation Examples First, a high-adhesion plastic reflector includes a plastic substrate and a TiAlN adhesive layer, a Ti seed layer and an Al reflective layer sequentially deposited on the surface of the plastic substrate; the TiAlN adhesive layer and the plastic substrate have C-N bonds, (C-O)-(Ti,Al,N) bonds and C-Ti,C-Al bonds.

[0040] Preferably, the thickness of the TiAlN bonding layer is 50-100 nm; the thickness of the Ti seed layer is 20-80 nm; and the thickness of the Al reflective layer is 70-100 nm.

[0041] Preferably, the Al reflective layer is grown in a layer-island hybrid mode, with Al grain size ≥ 100 nm and surface roughness < 2 nm.

[0042] Preferably, the TiAlN binder layer, Ti seed layer and Al reflective layer are deposited sequentially by magnetron sputtering.

[0043] Preferably, the plastic substrate is selected from one or more of polycarbonate (PC), polymethyl methacrylate (PMMA), polyphenylene sulfide (PPS), polystyrene (PS), and polyethylene terephthalate (PET); more preferably, it is polycarbonate (PC). PC not only has high strength and excellent heat resistance, but also good weather resistance and anti-aging properties, enabling it to be used for a long time in outdoor environments without failure.

[0044] Secondly, a method for preparing a high-adhesion plastic reflector includes the following steps: 1) Cleaning treatment of the plastic substrate surface.

[0045] Preferably, in step 1), the cleaning process includes: ultrasonically removing oil stains from the surface of the plastic substrate using chemical reagents and deionized water respectively, followed by drying with cold air, hot air and oven drying.

[0046] Preferably, in step 1), the chemical reagent is anhydrous ethanol, isopropanol, or acetone, and more preferably isopropanol.

[0047] Preferably, in step 1), the drying temperature is 60-80℃ and the time is 120-240 min.

[0048] 2) Under inert conditions, magnetron sputtering is used to remove the oxide layer on the surface of Ti and Al targets and to activate the surface of plastic substrates by plasma.

[0049] Preferably, step 2) specifically includes: fixing the plastic substrate on the base frame in a closed unbalanced magnetron sputtering coating machine, evacuating the vacuum; filling inert gas, and first sputtering the Ti target, Al target and plastic substrate with high negative bias and low current.

[0050] The high negative bias voltage is 200-500V. If the bias voltage is too low, it will not be effective for ion cleaning of the substrate; if it is too high, the energy of the particles impacting the substrate will be too high, and the substrate surface will easily overheat and be damaged. The low current is 0.2-0.4A. If the current is too low, the target material will not easily ignite; if the current is too high, the substrate will undergo the sputtering deposition process.

[0051] Preferably, in step 2), the power supply on the target of the closed-loop unbalanced magnetron sputtering coating machine is a DC power supply; the negative bias power supply on the base frame is a pulse power supply with a frequency of 200-300Hz and a pulse width of 400-600 μs.

[0052] Preferably, in step 2), the vacuum level after evacuation is 6.5 × 10⁻⁶. -6 -8.5×10 -6 torr; temperature is room temperature; inert gas argon, flow rate is 20-40 sccm; the rotation speed of the base stage is 3-5 r / min; the sputtering treatment time is 10-20 min.

[0053] Because Al is readily oxidized to Al₂O₃ by oxygen in the atmosphere under low vacuum conditions, high vacuum conditions are sufficient to ensure the formation of a pure Al layer. Furthermore, too low a working pressure is detrimental to target initiation, while too high a pressure causes energy loss after sputtered atoms collide with argon atoms in the cavity, preventing them from spontaneously migrating to defects on the film surface after reaching the substrate, resulting in poor film quality. Maintaining the stage rotation speed within the aforementioned range is beneficial for improving film deposition uniformity.

[0054] 3) A TiAlN bonding layer was deposited on the surface of a plastic substrate by magnetron sputtering.

[0055] Preferably, in step 3), the deposition conditions of the TiAlN binder layer are as follows: the ratio of argon to nitrogen is 25-35: 4-10 sccm, the Al target current is 1.5-2.0A, the Ti target current is 2.0-3.0A, the negative bias voltage is 60-100V, and the time is 8-20min.

[0056] 4) A Ti seed layer is deposited on the surface of the TiAlN binder layer by magnetron sputtering.

[0057] Preferably, in step 4), the deposition conditions of the Ti seed layer are: Ti target current of 2.0-3.0A, negative bias voltage of 60-100V, and time of 8-20min.

[0058] Preferably, in step 4), the current is adjusted back to 0.2-0.4A after sputtering. This is to protect the Ti target and prevent subsequent Al layer deposition onto the Ti target surface.

[0059] 5) An Al reflective layer is deposited on the surface of the Ti seed layer by magnetron sputtering.

[0060] Preferably, in step 5), the deposition conditions of the Al reflective layer are as follows: target sputtering deposition is used, which is beneficial to improve the deposition rate and Al film density; the current is 1.0-3.0A, the negative bias voltage is 60-100V, and the time is 2-10min.

[0061] Preferably, in step 5), after sputtering is complete, the current and voltage are turned off, the gas flow rate is reduced to 5-10 sccm, and this is maintained for 10-15 minutes before the coating process is shut down. This is because the temperature inside the chamber is slightly high after deposition, and a small amount of argon gas is introduced to prevent the Al film from oxidizing.

[0062] Specific embodiments and comparative examples Comparative Example 1 (PC-A1) (1) The PC substrate was ultrasonically cleaned with isopropanol and deionized water for 15 min, dried with cold and hot air and then dried in a hot oven (70℃, 180 min). It was then fixed on the base platform of a closed unbalanced magnetron sputtering equipment (UDP-650). After rough vacuuming with a mechanical pump, the vacuum degree was raised to 7.5×10⁻⁶ with an oil diffusion pump. -6 torr; (2) At room temperature, argon working gas is introduced at a flow rate of 30 sccm, the turntable speed is set to 4 r / min, the frequency of the pulse bias power supply is set to 250 Hz and the pulse width is set to 500 μs. The target and substrate are first sputtered with a negative bias of 200 V and a low current of 0.3 A for 10 min to remove the oxide layer on the surface of the Al target and the plasma activation on the surface of the plastic substrate. (3) Change the current for sputtering the Al target to 2.71A and the negative bias voltage to 80V, and sputter an Al reflective layer on the PC substrate for 3 minutes with a thickness of 30nm. After the sputtering process is completed, turn off the current and voltage, adjust the argon flow rate to 10sccm for 10 minutes, then turn off the coating program and remove the chamber after it has cooled to room temperature.

[0063] Comparative Example 2 (PC-Ti / Al) (1) The PC substrate was ultrasonically cleaned with isopropanol and deionized water for 15 min, dried with cold and hot air and then dried in a hot oven (70℃, 180 min). It was then fixed on the base platform of a closed unbalanced magnetron sputtering equipment (UDP-650). After rough vacuuming with a mechanical pump, the vacuum degree was raised to 7.5×10⁻⁶ with an oil diffusion pump. -6 torr; (2) At room temperature, argon gas is introduced as working gas with a flow rate of 30 sccm. The turntable speed is set to 4 r / min. The frequency of the pulse bias power supply is set to 250 Hz and the pulse width is set to 500 μs. The target and substrate are first sputtered with a negative bias of 200 V and a low current of 0.3 A for 10 min to remove the oxide layer on the surface of the Ti target and Al target and the plasma activation on the surface of the plastic substrate. (3) Change the current on the Ti target to 2.47A and the negative bias voltage to 80V, first sputter a Ti seed layer for 14min with a thickness of 50nm, and then adjust the current on the Ti target back to 0.3A; (4) Change the current for sputtering the Al target to 2.71A and the negative bias voltage to 80V, and sputter an Al reflective layer on the Ti seed layer for 3 minutes with a thickness of 30nm. After the sputtering process is completed, turn off the current and voltage, adjust the argon gas flow rate to 10sccm for 10 minutes, then turn off the coating program and remove the chamber after it has cooled to room temperature.

[0064] Example 1 (PC-TiAlN / Ti / Al) (1) The PC substrate was ultrasonically cleaned with isopropanol and deionized water for 15 min, dried with cold and hot air and then dried in a hot oven (70℃, 180 min). It was then fixed on the base platform of a closed unbalanced magnetron sputtering equipment (UDP-650). After rough vacuuming with a mechanical pump, the vacuum degree was raised to 7.5×10⁻⁶ with an oil diffusion pump. -6 torr; (2) At room temperature, argon gas is introduced as working gas with a flow rate of 30 sccm. The turntable speed is set to 4 r / min. The frequency of the pulse bias power supply is set to 250 Hz and the pulse width is set to 500 μs. The target and substrate are first sputtered with a negative bias of 200 V and a low current of 0.3 A for 10 min to remove the oxide layer on the surface of the Ti target and Al target and the plasma activation on the surface of the plastic substrate. (3) Then, argon gas was introduced at 30 sccm and nitrogen gas at 7 sccm. At the same time, the Al target current was turned on at 1.56 A and the Ti target current at 2.1 A, the bias voltage was -80 V, and the TiAlN layer was sputtered for 30 min with a thickness of 60 nm.

[0065] (4) Change the current on the Ti target to 2.41A and the negative bias voltage to 80V, first sputter a Ti seed layer for 14min with a thickness of 50nm, and then adjust the current on the Ti target back to 0.3A; (5) Change the current for sputtering the Al target to 2.71A and the negative bias voltage to 80V, and sputter an Al reflective layer on the Ti seed layer for 3 minutes with a thickness of 30nm. After the sputtering process is completed, turn off the current and voltage, adjust the argon gas flow rate to 10sccm for 10 minutes, then turn off the coating program and remove the chamber after it has cooled to room temperature.

[0066] Performance testing and characterization The following is the data from the test: Figure 1The reflectance spectra of Comparative Example 1 and Comparative Example 2 in the range of 380-800 nm are shown. Figure 1 As shown, the visible light reflectance in Comparative Example 1 is 84.07%, while the visible light reflectance of the film in Comparative Example 2 is significantly improved, reaching 92.63%. Under the same Al film deposition process conditions, this improvement in visible light reflectance is attributed to the addition of the Ti seed layer. The results show that the addition of the Ti seed layer can significantly improve the visible light reflectance of the Al film.

[0067] Figure 2 AFM 10 × 10µm for high-adhesion PC reflectors 2 2D images of the scanned area: (a) Comparative Example 1 and (c) Comparative Example 2; 3D images: (b) Comparative Example 1 and (d) Comparative Example 2. (e.g.) Figure 2 As shown, Comparative Example 1 ( Figure 2 (a) The 2D image of the sample shows an uneven surface with large differences in brightness, indicating that its surface has many irregular protrusions. Its 3D ( Figure 2 (c) The image also more clearly shows this phenomenon, confirming the presence of numerous sharp protrusions on its surface. Compared to Comparative Example 1, Comparative Example 2 ( Figure 2 The 2D image of the sample in (c) is relatively flat, with almost no difference in brightness or darkness on the surface, and no sharp protrusions. Its 3D ( Figure 2 (d) also shows a very smooth surface structure. Nanoscope analysis showed that the surface roughness Ra of the sample in Comparative Example 1 was 4.66 nm, while the surface roughness of the sample in Comparative Example 2 was only Ra = 1.77 nm. This indicates that the initial growth mode of the Al film in Comparative Example 1 was isolated islands, and the growth of each isolated island led to an increase in roughness. In contrast, the roughness of the Al-Al film in Comparative Example 2 was significantly increased due to the Al-Al (264 kJ mol... −1 ) and Ti─Al (263 kJ mol) −1 The tight bond energy of the Al film causes the growth mode to change from island growth to layer-island combined growth mode. This more layered growth mode leads to a decrease in the surface roughness of the film. Figure 2 The scanned area in (a) also shows a larger size than... Figure 2 (b) Smaller grain size in the sample. Reduced grain size leads to increased grain boundaries, and the plasmon resonance at the grain boundaries on the film surface results in enhanced light scattering, which is why Comparative Example 1... Figure 1 (a) shows a decrease in film reflectivity. The results indicate that the addition of a Ti seed layer leads to a more layered growth mechanism, which reduces the surface roughness of the film; while the increase in grain size reduces grain boundaries, and the reduction in light scattering caused by grain boundary plasmon resonance increases the film reflectivity.

[0068] Figure 3The reflectance spectra of Comparative Example 2 and Example 1 in the 380-800 nm range are shown. Figure 3 As shown, the visible light reflectance in Comparative Example 2 is 92.63%, and the visible light reflectance of the film layers in Example 1 is basically the same, at 92.65%. Under the same Al film deposition process conditions, the reflectance of the Al layer deposited on the Ti seed layer is not significantly different. The results indicate that the addition of TiAlN as a binder layer does not affect the reflectance of the Al film on the Ti seed layer. However, when the TiAlN coating is too thick, its surface roughness increases, which increases the surface roughness of the Ti and Al layers subsequently deposited on the coating, thus leading to a decrease in reflectance. When the coating thickness is too thin, the coating cannot form a strong bond with the PC interface that is completely covered, resulting in weakened adhesion.

[0069] Figure 4 SEM images of high-adhesion PC reflectors: (a) Comparative Example 2 and (b) Example 1. Figure 4 As shown, Comparative Example 2 ( Figure 4 (a) contains a Ti seed layer ( Figure 4 (b) The Al film surface is smooth and dense, with indistinct grain boundaries and no obvious changes in light and dark contrast. Example 1 ( Figure 4 (b) The surface morphology of the film is not significantly different from that of Comparative Example 2; the film surfaces are all very smooth. This smooth surface structure is Figure 3 The fundamental reason for the high reflectivity in Comparative Example 2 and Example 1 is that the addition of the high-adhesion TiAlN layer in Example 1 does not affect the morphology of the Al film on the Ti seed layer, as it remains due to Al-Al (264 kJ mol). −1 ) and Ti─Al (263 kJ mol) −1 The tight bond energy of TiAlN causes the Al film growth mode on the Ti seed layer to change from island-like growth to a layer-island combined growth mode, resulting in a reduction in surface roughness. The results show that adding TiAlN as a binder layer does not affect the growth mode of the Al film on the Ti seed layer, and therefore has no impact on the final reflectivity.

[0070] Figure 5 Optical micrographs of a high-adhesion PC reflector after five tape peeling experiments: (a) Comparative Example 2, (b) Example 1 and digital photographs; (c) Comparative Example 2, (d) Example 1. Figure 5 As shown in (a), many cracks are distributed around the scratch in the sample with Ti as the adhesive layer in Comparative Example 2 under an optical microscope, and the coating peels off. In contrast, only very fine cracks appear around the scratch in the sample with TiAlN as the adhesive layer in Example 1, which are almost invisible even under a microscope. Figure 5 (c) and Figure 5 (d) To more intuitively observe the peeling of the 100-grid tape after the sample was peeled off, the sample in Example 2 was compared with the sample in Example 2. Figure 5 (c) The coating peeled off after repeated tape peeling following the crisscross pattern, indicating poor adhesion. Compared with Comparative Example 2, the sample in Example 1 ( Figure 5 (d) No peeling occurred after repeated tape removal, demonstrating very strong adhesion. The results indicate that the PC reflector with TiAlN as the bonding layer exhibits higher mechanical adhesion, which improves the coating's durability. This is because the PC and TiAlN coatings have high adhesion through C-N bonds, (C-O)-(Ti,Al,N) bonds, and C-Ti, C-Al bonds. At appropriate deposition temperatures (even low temperatures, high-energy particle bombardment can provide activation energy), Ti atoms can slightly diffuse into the TiAlN bonding layer, or N atoms can slightly diffuse into the Ti seed layer, forming a thin and dense Ti-N reaction transition layer. This transition layer is chemically gradual, tightly connecting pure metallic Ti to ceramic TiAlN. Subsequently, the Al layer deposited on Ti forms a solid solution / compound transition layer through inter-atomic diffusion via the intermetallic Ti-Al bonds, generating strong adhesion between the Ti and Al layers. Figure 6 To test the C1s spectra of different adhesive layers at the PC interface using XPS. Figure 6XPS analysis revealed that the Ti-PC interface is primarily defined by (C-O)-Ti bonds and a small number of C-Ti bonds, while the TiAlN-PC interface is mainly defined by C-N bonds, (C-O)-(Ti,Al,N) bonds, C-Ti bonds, and C-Al bonds. Precise quantification of interfacial bonding was discussed using the Integrated Orbital Hamiltonian Group (ICOHP) analysis; a more negative ICOHP value indicates a stronger bond. Since the ICOHP value depends not only on the quantum chemical properties of the bond but also on the interatomic distance, the C-N bond strength is highest at interfaces independent of the metal nitride system (ICOHP values ​​range from -10 to -18 eV). In contrast, the strengths of (C-O)-Al, (C-O)-Ti, C-Al, and C-Ti bonds are significantly weaker (ICOHP values ​​range from -1 to -5 eV). Therefore, compared to the PC|Ti system, the PC|TiAlN interface not only possesses stronger C-N bonds and more interfacial bonds, but also exhibits a higher density of inter-group bonding. The complex cross-linked mixture of these groups may be the basis for the formation of a strong adhesive interface. Overall, XPS analysis indicates that the PC|Ti interface reflects the strong reactivity of Ti in generating interfacial C-Ti and (C-O)-Ti bonds, but the cross-linking effect is weaker due to the lack of high-strength interfacial C-N bonds. In contrast, the PC|TiAlN interface not only has a higher bond density but also numerous interfacial C-N bond interactions.

[0071] Figure 7 Planar views of a PC surface plate model visualized using VESTA are shown: (a) the original surface, (b) TiAlN with different atomic deposition, and (c) the surface after Ti deposition. Figure 7 As shown in (b), for the PC | TiAlN interface, the C-N bond plays a major role in the formation of the interface bond. Figure 7 (b) Furthermore, the combination of highly reactive N and Ti, along with selectively reactive Al, leads to complex cross-linking and mixing of interfacial groups, resulting in a significant increase in PC surface coverage after TiAlN deposition. For the PC | Ti interface ( Figure 7(c) Although Ti exhibits strong reactivity and can form most interfacial bonds at the PC | Ti interface, namely (C-O)-Ti and C-Ti bonds, the lack of high-strength C-N bonds not only leads to a decrease in interfacial bond density but also directly results in a weak cross-linking effect of the PC | Ti interfacial groups. Experimental results show that the Ti-PC interface is mainly defined by (C-O)-Ti and a small amount of C-Ti, while the interface formation between TiAlN and PC is mainly defined by C-N bonds, (C-O)-(Ti,Al,N) bonds, and C-Ti,C-Al bonds. Although the PC | Ti interface reflects the strong reactivity of Ti, which can generate interfacial C-Ti and (C-O)-Ti bonds, the lack of high-strength interfacial C-N bonds leads to a weak cross-linking effect. In contrast, the PC | TiAlN interface not only has a higher bonding density, but the interaction of many interfacial C-N bonds and the complex highly cross-linked and mixed structure of various interfacial groups promote stronger interface formation.

[0072] Figure 8 Optical micrographs of high-adhesion PC reflectors after testing with an automatic scratch tester: (a) Comparative Example 2 and (b) Example 1. As shown in the figures, the scratches on the two samples under the same load force show significant differences, such as... Figure 8 As shown in (a), the scratches on the sample surface are shallow, especially under low load conditions, the scratches are almost invisible, compared to Figure 8 (a) In comparison, Figure 8 The scratches on the sample surface in (b) are clearly visible, even under low load conditions. Experimental results show that the PC sample with the TiAlN binder layer has shallower scratches and higher hardness. This is likely because the TiAlN binder layer is a hard, wear-resistant coating with good wear resistance, thus the scratches are not obvious. However, the hardness of the Ti binder layer is much lower than that of the TiAlN layer, leading to scratches and cracks under smaller loads. This indicates that the embedding of the TiAlN thin layer significantly improves the wear resistance of the Al layer. Meanwhile, the Ti seed layer deposited directly on the plastic substrate faces fundamental obstacles due to the poor thermal stability, large thermal expansion mismatch, and low surface energy of the plastic substrate, resulting in lower hardness and Young's modulus of the Ti seed layer. On a hard, stable, and compatible substrate like TiAlN, a more crystalline and denser Ti seed layer can be obtained, with hardness and Young's modulus closer to that of bulk titanium. High hardness and a smooth surface structure contribute to the scratch resistance of the coating. Therefore, the increased scratch resistance of the TiAlN / Ti / Al layer sample may be attributed to the TiAlN layer being a hard ceramic coating.

[0073] Figure 9 The relationship between the coefficient of friction and reciprocating time for the uncoated, Comparative Example 2, and Example 1 plastic samples is shown. Figure 9 (a) and their microhardness values ​​( Figure 9 (b)). During the test, the average coefficient of friction for the uncoated PC sample was 0.69 (see [reference]). Figure 9 (a) The average coefficient of friction for the Ti / Al coated PC sample was 0.62, which was consistent with that of the uncoated PC sample. The coefficient of friction for the TiAlN / Al coated PC sample was lower than that for the uncoated PC sample (see [reference]). Figure 9 (a) Furthermore, as the sliding distance increases, the friction coefficient shows a decreasing trend. The average friction coefficient of the TiAlN / Al coated sample is 0.49, indicating that the TiAlN / Al coating improves the wear resistance of the PC substrate to a certain extent and plays a good protective role. Figure 9 (b) shows the microhardness values ​​of the three samples obtained using a Vickers hardness tester. As can be seen from the figure, the microhardness of the uncoated PC sample is 13.81 kg / mm². 2 The microhardness values ​​of the PC mirror samples in Comparative Example 2 and Example 1 were both improved, reaching 14.57 and 15.39 kg / mm², respectively. 2 Therefore, this increase in microhardness is due to the film coating on the plastic surface. The hardness of the TiAlN-coated sample is also slightly higher than that of the Ti-coated sample. This is because the TiAlN coating is a high-hardness ceramic nitride coating, and this slight increase is due to the thinner film thickness, making it difficult to produce a very significant difference. This is also related to... Figure 9 The tribological data in (a) remain consistent. The results show that the TiAlN-coated PC mirror sample exhibits higher tribological resistance and microhardness, which provides better protection for the fabricated PC mirror.

[0074] Figure 10 Digital photographs of the high-adhesion PC reflectors of Comparative Example 1 (left), Comparative Example 2 (middle), and Example 1 (right). Figure 10 As shown, all three PC reflector samples exhibited a bright silver-white color. However, compared to Comparative Example 2 and Example 1, the silver-white brightness of the PC reflector sample in Comparative Example 1 was lower, with a slight grayish tint. This is also consistent with... Figure 1 and Figure 3 The reflectivity curves of the samples remained consistent. The results indicate that the PC reflector fabricated using this invention has a smooth macroscopic surface and high brightness, meeting production requirements.

[0075] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high adhesion plastic mirror characterized by: The plastic substrate and the TiAlN adhesive layer, Ti seed layer and Al reflecting layer deposited on the surface of the plastic substrate in sequence; The TiAlN adhesive layer and the plastic substrate have C-N bond, (C-O)-(Ti, Al, N) bond and C-Ti, C-Al bond.

2. The high-adhesion plastic mirror of claim 1, wherein: The thickness of the TiAlN adhesive layer is 50-100 nm.

3. The high-adhesion plastic mirror of claim 2, wherein: The thickness of the Ti seed layer is 20-80 nm.

4. The high-adhesion plastic mirror of claim 3, wherein: The thickness of the Al reflecting layer is 70-100 nm.

5. The high-adhesion plastic mirror according to claim 1 or 4, wherein: The Al reflecting layer is grown in island combination mode, the size of Al grain is greater than or equal to 100 nm, and the surface roughness is less than 2 nm.

6. The high-adhesion plastic mirror of claim 1, wherein: The TiAlN adhesive layer, Ti seed layer and Al reflecting layer are deposited in sequence by magnetron sputtering.

7. A method of producing a high adhesion plastic mirror according to any one of claims 1 to 6, characterized in that The method comprises the following steps: depositing the TiAlN adhesive layer on the surface of the plastic substrate by magnetron sputtering; depositing the Ti seed layer on the surface of the TiAlN adhesive layer by magnetron sputtering; depositing the Al reflecting layer on the surface of the Ti seed layer by magnetron sputtering.

8. The method of claim 7, wherein: The deposition conditions of the TiAlN adhesive layer are as follows: the ratio of argon and nitrogen is 25-35:4-10 sccm, the Al target current is 1.5-2.0 A, the Ti target current is 2.0-3.0 A, the negative bias voltage is 60-100 V, and the time is 8-20 min.

9. The method of claim 7 wherein: The deposition conditions of the Ti seed layer are as follows: the Ti target current is 2.0-3.0 A, the negative bias voltage is 60-100 V, and the time is 8-20 min.

10. The method of claim 7 wherein: The deposition conditions of the Al reflecting layer are as follows: the deposition is carried out by using opposite target sputtering; the current is 1.0-3.0 A, the negative bias voltage is 60-100 V, and the time is 2-10 min.

Images