Thin films, devices, and methods of making devices

Abstract

The application provides a film and a preparation method and device thereof. The application sets a third film layer with a proper thickness, refractive index n and extinction coefficient k on the second film layer, and adjusts the components of the second film layer and the third film layer, so that the blue light reflected by the third film layer destructively interferes with the blue light reflected by the second film layer (destructive interference), and the yellow light reflected by the third film layer constructively interferes with the yellow light reflected by the second film layer (constructive interference), so that the chroma value b* of the film changes from a negative value to a positive value, and the film has a warm color effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of film coating, in particular to a thin film, a device and a preparation method of the device. BACKGROUND

[0002] Silver thin film has similar color to metal substrate such as stainless steel, and is widely used. The materials for making silver thin film in the current technology mainly include high reflectivity elements such as aluminum (Al), silver (Ag) and chromium (Cr). Aluminum is easy to form aluminum oxide on the surface, thereby reducing brightness, and is easy to be corroded by halogen ions and fail. Silver is limited in application scenarios due to high material cost. Chromium is widely used in silver film layer due to high corrosion resistance, high hardness, low surface energy and other advantages.

[0003] In the perception of human eyes, colors with a bias towards warm color system (b>0) will make people feel high-spirited, and colors with a bias towards cold color system (b<0) will make people feel indifferent and calm. The brightness (L) of the silver thin film of the Cr substrate can reach 83, which belongs to cold color system material, and will make people have the idea of sharp and indifferent product, so it is expected that the silver thin film on the surface of the product can be biased towards warm color system. SUMMARY

[0004] Therefore, the present application provides a thin film to achieve the effect of warm color system.

[0005] An embodiment of the present application provides a thin film formed on the surface of a substrate, which comprises a first film layer, a second film layer and a third film layer stacked in sequence. The first film layer is located on the surface of the substrate. The second film layer is located on the surface of the first film layer away from the second film layer. The third film layer is located on the surface of the second film layer away from the first film layer. The second film layer comprises chromium carbide. The third film layer comprises chromium carbide, and the atomic percentage content of chromium elements in the third film layer is lower than that in the second film layer. The thickness of the third film layer is 5-20 nm. When the incident light is in the wavelength range of 250-800 nm, the refractive index n of the second film layer is 1-3.8, and the extinction coefficient k of the second film layer is 1.8-4.3. When the incident light is in the wavelength range of 250-800 nm, the refractive index n of the third film layer is 1.2-3.3, and the extinction coefficient k of the third film layer is 1.8-4.3. The blue light reflected by the third film layer and the blue light reflected by the second film layer superimpose to produce destructive interference, and the yellow light reflected by the third film layer and the yellow light reflected by the second film layer superimpose to produce constructive interference.

[0006] In an embodiment, the thickness of the second film layer is 100-2000 nm.

[0007] In one embodiment, the thin film further comprises a transition layer between the first film layer and the second film layer. The thickness of the transition layer is 100 nm to 2000 nm. The transition layer comprises chromium silicon nitride, titanium silicon nitride or tungsten silicon nitride.

[0008] In one embodiment, the thickness of the first film layer is 100 nm to 2000 nm. The first film layer comprises chromium, titanium or tungsten.

[0009] In one embodiment, the thickness of the thin film is 950 nm to 6000 nm.

[0010] In one embodiment, the substrate comprises an electrically conductive material or a plastic. The electrically conductive material comprises a metal, silicon or carbon fiber. The metal comprises stainless steel, aluminum, titanium, copper, nickel or magnesium. The plastic comprises one or more of polyvinyl chloride, polypropylene, polymethyl methacrylate, polystyrene, polyvinyl acetate, polyethylene terephthalate, styrene-acrylonitrile copolymer, ethylene-vinyl acetate copolymer, polycarbonate or polyamide.

[0011] One embodiment of the present application provides a device comprising a substrate and a thin film as described above.

[0012] One embodiment of the present application provides a method for preparing a device, comprising the following steps: placing a substrate in a reaction furnace of a vacuum coating machine for cleaning; introducing argon into the reaction furnace and turning on the power supply and the target material to deposit a first film layer on the surface of the substrate; introducing argon and a reaction gas into the reaction furnace and turning on the power supply and the target material to deposit a second film layer on the surface of the first film layer, the second film layer comprising chromium carbide; introducing argon and a reaction gas into the reaction furnace and turning on the power supply and the target material to deposit a third film layer on the surface of the second film layer, thereby obtaining the thin film. The third film layer comprises chromium carbide. The atomic percentage of chromium in the third film layer is lower than that in the second film layer. The thickness of the third film layer is 10 nm to 20 nm. When the wavelength of incident light is in the range of 250 nm to 800 nm, the refractive index n of the second film layer is 1 to 3.8, and the extinction coefficient k of the second film layer is 1.8 to 4.3. When the wavelength of incident light is in the range of 250 nm to 800 nm, the refractive index n of the third film layer is 1.2 to 3.3, and the extinction coefficient k of the third film layer is 1.8 to 4.3. The blue light reflected by the third film layer and the blue light reflected by the second film layer superimpose to produce destructive interference, and the yellow light reflected by the third film layer and the yellow light reflected by the second film layer superimpose to produce constructive interference.

[0013] In one embodiment, in the step of depositing the first film layer, the flow rate of the argon gas is 150-500 sccm, the target material comprises a chromium target, a titanium target or a tungsten target, the working current of the power supply is 6-14 A, the voltage is 100-250 V, the duty cycle is 40-90%, and the duration is 54-66 min. In the step of depositing the second film layer, the flow rate of the argon gas is 50-300 sccm, the flow rate of the reaction gas is 5-35 sccm, the reaction gas comprises methane or acetylene, the target material comprises a chromium target, the number of the chromium target is W1, the working current of the power supply is I1, I1 is 6-14 A, the voltage is 100-250 V, the duty cycle is 40-90%, and the duration is T1, T1 is 22.5-27.5 min. In the step of depositing the third film layer, the flow rate of the argon gas is 50-300 sccm, the flow rate of the reaction gas is 5-35 sccm, the reaction gas comprises methane or acetylene, the target material comprises a chromium target, the number of the chromium target is W2, the working current of the power supply is I2, I2 is 6-14 A, the voltage is 100-250 V, the duty cycle is 40-90%, and the duration is T2, T2 is 3.15-3.85 min. Wherein, W2W1, I2I1, and T2T1.

[0014] In one embodiment, before the step of depositing the second film layer on the surface of the first film layer, the preparation method further comprises: introducing argon gas and nitrogen gas into the reaction furnace, and turning on the power supply and the target material to deposit a transition layer on the surface of the first film layer. The flow rate of the argon gas is 150-500 sccm, and the flow rate of the nitrogen gas is 25-80 sccm. The target material comprises a silicon target, and further comprises a chromium target, a titanium target or a tungsten target. The working current of the power supply is 6-14 A, the voltage is 100-250 V, the duty cycle is 40-90%, and the duration is 81-99 min.

[0015] The present application can change the chroma value b* of the thin film from a negative value to a positive value by setting a third film layer with a suitable thickness, refractive index n and extinction coefficient k on the second film layer, and adjusting the components of the second film layer and the third film layer to make the blue light reflected by the third film layer destructively interfere with the blue light reflected by the second film layer (destructive interference), and make the yellow light reflected by the third film layer constructively interfere with the yellow light reflected by the second film layer (constructive interference), so that the thin film has a warm color effect. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The device and the thin film of one embodiment of the present application are shown in the schematic diagram.

[0017] Figure 2 Schematic diagram for two waves superposition to produce constructive interference.

[0018] Figure 3 Schematic diagram for two waves superposition to produce destructive interference.

[0019] Figure 4 Schematic diagram of the film prepared in Comparative Example 1 of the present application.

[0020] Figure 5 Color distribution diagram of the film prepared in Examples 1-3 of the present application.

[0021] Figure 6 Refractive index n and extinction coefficient k curve diagram of the surface layer of the film prepared in Example 1 of the present application.

[0022] Figure 7 Refractive index n and extinction coefficient k curve diagram of the surface layer of the film prepared in Comparative Example 1 of the present application.

[0023] Figure 8A Scanning electron microscope (SEM) diagram of the film prepared in Example 1 of the present application.

[0024] Figure 8B Scanning electron microscope (SEM) diagram of the cross section of the film prepared in Example 1 of the present application.

[0025] Figure 9A Scanning electron microscope (SEM) diagram of the film prepared in Example 2 of the present application.

[0026] Figure 9B Scanning electron microscope (SEM) diagram of the cross section of the film prepared in Example 2 of the present application.

[0027] Figure 10A Scanning electron microscope (SEM) diagram of the film prepared in Example 3 of the present application.

[0028] Figure 10B Scanning electron microscope (SEM) diagram of the cross section of the film prepared in Example 3 of the present application.

[0029] Explanation of main element symbols

[0030] 1000: device; 100: film; 200: substrate; 10: first film layer; 20: second film layer; 30: third film layer; 40: transition layer.

[0031] The following specific embodiments will further illustrate the embodiments of the present application in conjunction with the above-mentioned figures. DETAILED DESCRIPTION

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. The terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the embodiments of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] It will be understood that when a layer is referred to as being "on" another layer, it can be directly on that other layer or there can be intermediate layers in between. Conversely, when a layer is referred to as being "directly" on another layer, there are no intermediate layers.

[0034] Embodiments of this application are described herein with reference to cross-sectional views, which are schematic diagrams of idealized embodiments (and intermediate configurations) of this application. Therefore, variations in the shapes illustrated due to manufacturing processes and / or tolerances are foreseeable. Consequently, embodiments of this application should not be construed as limited to the specific shapes of the areas illustrated herein, but should include, for example, deviations in shape due to manufacturing processes. The areas shown in the figures are merely illustrative, and their shapes are not intended to represent the actual shapes of the illustrated devices, nor are they intended to limit the scope of this application.

[0035] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] Please see Figure 1The first aspect of the present application provides a thin film 100 formed on the surface of a substrate 200. The thin film 100 comprises a first film layer 10, a second film layer 20 and a third film layer 30 arranged in sequence. The first film layer 10 is located on the surface of the substrate 200, the second film layer 20 is located on the surface of the first film layer 10 away from the second film layer 20, and the third film layer 30 is located on the surface of the second film layer 20 away from the first film layer 10. The first film layer 10 is used to connect the substrate 200 to increase the adhesion of the thin film 100 on the surface of the substrate 200, thereby reducing the probability of the thin film 100 falling off the surface of the substrate 200. The second film layer 20 and the third film layer 30 are used to reflect incident light, so that the thin film 100 presents a certain color (for example, silver color, etc.). The materials of the second film layer 20 and the third film layer 30 are both chromium carbide (CrC), which has a high refractive index n and a high extinction coefficient k, and has the characteristics of high reflection. Although the second film layer 20 and the third film layer 30 are both chromium carbide, the content of chromium element in the two film layers is different, so the incident light will be reflected on the surface of the third film layer 20 and the second film layer 20. In the present application, the atomic percentage of chromium element in the third film layer 30 is lower than that in the second film layer 20. The second film layer 20 formed by chromium carbide has the characteristics of high reflection, and the whole thin film 100 presents the effect of high brightness (L* is large); the third film layer 30 formed by chromium carbide can achieve the effect of yellow light reflection (constructive interference) without affecting the color and brightness of the second film layer 20, so that the thin film 100 achieves the effect of warm color system.

[0037] The thickness of the third film layer 30 is 5nm-15nm, for example, the thickness of the third film layer 30 can be 5nm, 6nm, 7nm, 8nm, 10nm, 11nm, 15nm or any value between any two adjacent values. When the incident light is in the wavelength range of 250nm-800nm, the refractive index n of the third film layer 30 is 1.2-3.3, and the extinction coefficient k of the third film layer 30 is 1.8-4.3. Under the above conditions, the blue light reflected by the third film layer 30 and the blue light reflected by the second film layer 20 superimpose to produce destructive interference, and the yellow light reflected by the third film layer 30 and the yellow light reflected by the second film layer 20 superimpose to produce constructive interference. The reasons for the blue light to produce destructive interference and the yellow light to produce constructive interference will be explained in detail below.

[0038] As shown in Figure 1 When the incident light enters the thin film 100, the incident light will be reflected by the third film layer 30 and the second film layer 20 respectively, and the total reflected light is the superposition of the reflected light of the third film layer 30 and the reflected light of the second film layer 20. As shown in Figure 2 If the wave peak (or wave trough) of the reflected light of the third film layer 30 is similar or consistent with the wave peak (or wave trough) of the reflected light of the second film layer 20, constructive interference (constructive interference) occurs. As shown in Figure 3As shown, if the peak (or trough) of the light reflected by the third film layer 30 is similar or identical to the trough (or peak) of the light reflected by the second film layer 20, destructive interference occurs. When the optical path difference 2nd=(i+1 / 2)λ, the two sets of reflected light constructively interfere; when the optical path difference 2nd=iλ, the two sets of reflected light destructively interfere. Here, d is the thickness of the third film layer 30, and i and n are integers, respectively.

[0039] The inventors of the present application have found that the composition, optical parameters (refractive index n, extinction coefficient k), and thickness of the interference film layer (the third film layer 30 of the present application) affect the chromaticity value (L*, a*, b*) of the thin film 100. Here, L* represents brightness (black and white), and L* is 0-100, with no negative value. The larger the L* value, the whiter (brighter) the thin film 100 is, and the smaller the L* value, the darker (darker) the thin film 100 is. a* represents red-green color, and has positive and negative values, with a* positive representing a red bias and a* negative representing a green bias (not red enough). b* represents yellow-blue color, and also has positive and negative values, with b* positive representing a yellow bias and b* negative representing a blue bias. That is, if the blue light destructively interferes and the yellow light constructively interferes, the chromaticity value b* is positive, and the color of the thin film 100 will be warm. Therefore, the inventors of the present application have adjusted the composition (chromium carbide, and the atomic percentage of chromium in the third film layer 30 is lower than the atomic percentage of chromium in the second film layer 20) of the second film layer 20 and the third film layer 30, the thickness d of the third film layer 30, and the refractive index n and extinction coefficient k of the third film layer 30, so that the optical path difference between the blue light reflected by the third film layer 30 and the blue light reflected by the second film layer 20 is an integer multiple of the wavelength (2nd=iλ), the blue light reflected by the third film layer 30 destructively interferes with the blue light reflected by the second film layer 20, the optical path difference between the yellow light reflected by the third film layer 30 and the yellow light reflected by the second film layer 20 is an odd multiple of half the wavelength (2nd=(i+1 / 2)λ), the yellow light constructively interferes, the chromaticity value b* changes from negative to positive while the chromaticity values L* and a* remain substantially unchanged, and thus the thin film 100 has a warm color effect.

[0040] In some embodiments, the third film layer 30 can be formed by a physical vapor deposition (PVD) technique. Specifically, the third film layer 30 can be formed by medium frequency magnetron sputtering (MF). The third film layer 30 can use chromium as the target material, and a reaction gas (methane or acetylene) can be introduced during sputtering. The target material can be a cylindrical target or a planar target, and the present application does not limit the target material.

[0041] In some embodiments, when the incident light is in the wavelength range of 250 nm to 800 nm, the refractive index n of the second film layer 20 is 1 to 3.8, and the extinction coefficient k of the second film layer 20 is 1.8 to 4.3. The thickness of the second film layer 20 can be 100 nm to 2000 nm. This ensures that the second film layer 20 can reflect the incident light. The thickness of the second film layer 20 can be 100 nm, 500 nm, 600 nm, 700 nm, 800 nm, 1000 nm, 2000 nm, or any value between any two adjacent values ​​mentioned above.

[0042] In some embodiments, the second film layer 20 can be formed by intermediate frequency magnetron sputtering. The second film layer 20 can use chromium as the target material, which can be a cylindrical target or a planar target. A reactive gas (methane or acetylene) needs to be introduced during the sputtering process.

[0043] In some embodiments, such as Figure 1 As shown, the thin film 100 also includes a transition layer 40, which is located between the first film layer 10 and the second film layer 20. The transition layer 40 can increase the bonding force between the second film layer 20 and the first film layer 10, and can further improve the adhesion of the thin film 100 to the surface of the substrate 200.

[0044] Furthermore, the thickness of the transition layer 40 can be 100nm to 2000nm to ensure the adhesion between the second film layer 20 and the first film layer 10. The thickness of the transition layer 40 can be 100nm, 500nm, 510nm, 540nm, 600nm, 650nm, 700nm, 1000nm, 2000nm, or any value between any two adjacent values ​​mentioned above.

[0045] Further, the transition layer 40 can be chromium silicon nitride (CrSiN), titanium silicon nitride (TiSiN), or tungsten silicon nitride (WSiN), and can be formed by intermediate frequency magnetron sputtering. The transition layer 40 can use chromium and silicon as the target material, or a chromium-silicon alloy in various proportions as the target material, and then a reactive gas (nitrogen) is introduced during sputtering to form the CrSiN transition layer 40. The transition layer 40 can use pure titanium and pure silicon as the target material, or a titanium-silicon alloy in various proportions as the target material, and then a reactive gas (nitrogen) is introduced during sputtering to form the TiSiN transition layer 40. The transition layer 40 can use pure tungsten and pure silicon as the target material, or a tungsten-silicon alloy in various proportions as the target material, and then a reactive gas (nitrogen) is introduced during sputtering to form the WSiN transition layer 40. The above-mentioned target materials can be cylindrical targets or planar targets, and this application is not limited thereto.

[0046] In some embodiments, the first film layer 10 can be made of, but not limited to, chromium, titanium or tungsten. The first film layer 10 can be formed by medium frequency magnetron sputtering, and the target material can be a chromium target, a titanium target or a tungsten target. The thickness of the first film layer 10 can be 190-400 nm, for example, the thickness of the first film layer 10 can be 190 nm, 195 nm, 210 nm, 270 nm, 300 nm, 350 nm, 400 nm or any value between any two adjacent values. The thickness of the first film layer 10 in the above range can ensure the adhesion of the thin film 100 on the surface of the substrate 200, thereby reducing the probability of the thin film 100 falling off the surface of the substrate 200.

[0047] In some embodiments, the total thickness of the thin film 100 can be 950-6000 nm, so as to ensure that the thin film 100 has a suitable thickness and is not easy to fall off, is not easy to scratch and expose the substrate 200, can control the cost and does not waste resources.

[0048] In some embodiments, the substrate 200 can be a conductive material or plastic. The conductive material can be, but not limited to, metal, silicon or carbon fiber, and the metal can be, but not limited to, stainless steel, aluminum, titanium, copper, nickel, magnesium, etc. The plastic can be one or more of polyvinyl chloride (PVC), polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene (PS), polyvinyl acetate (PVAc), polyethylene terephthalate (PET), styrene-acrylonitrile copolymer (SAN), ethylene-vinyl acetate copolymer (EVA), polycarbonate (PC) and polyamide (PA). The surface structure of the substrate 200 can be a polished surface, a wire-drawing surface or a sand-blasted surface, and if it is a polished surface, the color value L* of the thin film 100 can reach about 84 (L* ~ 84).

[0049] Please continue to refer to Figure 1 The second aspect of the present application provides a device 1000, which comprises a substrate 200 and a thin film 100 formed on the surface of the substrate 200. The device 1000 can be the shell of an electronic product, or a container for packaging other products (such as cosmetics, toys, food, etc.), which is not limited by the present application. The electronic product can be a desktop computer, a notebook computer, a tablet computer, a mobile phone, a media player, a television, a wristwatch device, a headset device, a headphone device, a head-mounted device, etc.

[0050] The third aspect of the present application provides a preparation method of a device 1000, which comprises steps S10-S50.

[0051] S10, placing the substrate 200 in the reaction furnace of a vacuum coating machine for cleaning.

[0052] In some embodiments, the substrate 200 can be plasma cleaned with argon (Ar). The flow rate of Ar can be 700-2000 sccm, the voltage (rotary bias) can be 500-1000 V, the duty cycle can be 50-90%, and the cleaning time can be 5-30 minutes. For example, the flow rate of Ar can be 1000 sccm, the voltage (rotary bias) can be 600 V, the duty cycle can be 80%, and the cleaning time can be 20 minutes.

[0053] In some embodiments, the substrate 200 can be pre-cleaned before being placed in the reaction furnace. The substrate 200 can be cleaned by pure water, cleaning agents (weak acid and weak base), bubbling, ultrasonic oscillation, and then dried and placed in a jig before being placed in a vacuum coating machine for vacuum pumping. First, the gas pressure in the reaction furnace can be pumped from atmospheric pressure to 20 Pa, and then the Roots pump can be started to assist in pumping to make the gas pressure in the furnace 7 Pa. Then, three molecular pumps are started to pump to a high vacuum state, and heating is started to make the temperature in the furnace 100°C, to remove the water and residual gas in the furnace, and to pump to 6.0x10 -3 Pa. Next, baking is performed at a constant pressure, the temperature in the furnace is increased to 120°C, and the temperature is adjusted back to 100°C after 2 hours of continuous pumping, and the pre-cleaning is completed. After the pre-cleaning is completed, the substrate 200 can be plasma cleaned.

[0054] S20, argon is introduced into the reaction furnace, and the power supply and the target material are turned on to deposit a first film layer 10 on the surface of the substrate 200.

[0055] In some embodiments, the flow rate of argon can be 150-500 sccm. The power supply and the target material are turned on, the working current can be 6-14 A, the rotary bias (voltage) can be 100-250 V, the duty cycle can be 40-90%, and the duration can be 60±60x10% min, i.e., 54-66 min. For example, the flow rate of Ar can be 300 sccm, two pairs of chromium targets can be turned on, the working current can be 8 A, the rotary bias can be 200 V, the duty cycle can be 70%, and the duration can be 60 min.

[0056] S30, argon and nitrogen are introduced into the reaction furnace, and the power supply and the target material are turned on to deposit a transition layer 40 on the surface of the first film layer 10.

[0057] In some embodiments, the flow rate of argon can be 150-500 sccm, and the flow rate of nitrogen can be 25-80 sccm. The target material can be a silicon target, and can also be a chromium target, a titanium target, or a tungsten target. The working current can be 6-14 A, the rotation bias (voltage) can be 100-250 V, the duty cycle can be 40-90%, and the duration can be 90±90×10% min, i.e. 81-99 min. For example, the flow rate of argon can be 300 sccm, and the flow rate of nitrogen can be 400 sccm. One pair of silicon targets and two pairs of chromium targets are turned on, the working current can be 10 A, the rotation bias (voltage) can be 150 V, the duty cycle can be 50%, and the duration can be 90 min.

[0058] In S40, argon and a reaction gas are introduced into the reaction furnace, and a power source and a target material are turned on to deposit a second film layer 20 on the surface of the transition layer 40 away from the first film layer 10. The second film layer 20 includes chromium carbide.

[0059] In some embodiments, the flow rate of argon can be 50-300 sccm, and the flow rate of the reaction gas can be 5-35 sccm. The reaction gas can be methane or acetylene. The target material can be a chromium target, and the number of chromium targets W1 can be adjusted according to actual needs. The working current of the power source can be I1, and I1 can be 6-14 A. The rotation bias (voltage) of the power source can be 100-250 V, the duty cycle can be 40-90%, and the duration can be T1, and T1 can be 25±25×10% min, i.e. 22.5-27.5 min. For example, the flow rate of argon can be 100 sccm, and the flow rate of acetylene can be 10 sccm. The number of chromium targets W1 turned on can be four pairs, the working current I1 of the power source can be 10 A, the rotation bias (voltage) can be 200 V, the duty cycle can be 50%, and the duration T1 can be 25 min.

[0060] In S50, argon and a reaction gas are introduced into the reaction furnace, and a power source and a target material are turned on to deposit a third film layer 30 on the surface of the second film layer 20 away from the transition layer 40, so as to obtain a thin film 100 as shown in FIG. 1C. The third film layer 30 includes chromium carbide. Figure 1

[0061] ​In some embodiments, the argon flow rate can be 50 sccm to 300 sccm, the reactant gas flow rate can be 5 sccm to 35 sccm, and the reactant gas can be methane or acetylene. The target material can be a chromium target, and the number of chromium targets W2 can be adjusted according to actual needs, but must be less than W1. The operating current of the power supply is I2, which is 6A to 14A, the rotor bias voltage can be 100V to 250V, the duty cycle can be 40% to 90%, and the duration is T2, which can be 3.5 ± 3.5 × 10% min, i.e., 3.15 min to 3.85 min. Wherein, W2 < W1, I2 < I1, and T2 < T1, to ensure that the atomic percentage content of chromium carbide in the third film layer is lower than that of chromium in the second film layer. The voltage during deposition of the third film layer can be equal to or less than the voltage during deposition of the second film layer, and the duty cycle during deposition of the third film layer can be equal to or less than the duty cycle during deposition of the second film layer. For example, the flow rate of argon can be 100 sccm, and the flow rate of acetylene can be 10 sccm. The number of chromium targets turned on, W2, can be 2 pairs, the operating current of the power supply, I2, can be 6A, the bias voltage of the rotating frame can be 200V, the duty cycle can be 50%, and the duration, T2, can be 3.5min.

[0062] The present application will be described in detail below with reference to specific embodiments and comparative examples.

[0063] Example 1

[0064] Pretreatment: The substrate (stainless steel, SUS 316) is cleaned with pure water and cleaning agents (weak acid and weak alkali), followed by bubbling and ultrasonic vibration. After drying, it is placed on a fixture and then placed in a vacuum coating machine for vacuuming. First, the pressure inside the reactor is evacuated from atmospheric pressure to 20 Pa. Then, a Roots pump is turned on to assist in evacuation, bringing the pressure inside the furnace to 7 Pa. Next, three molecular pumps are turned on to evacuate to a high vacuum state. Simultaneously, heating is initiated to raise the furnace temperature to 100°C, removing moisture and residual gas. The pressure is then reduced to 6.0 x 10⁻⁶. -3 Pa. Next, baking and pressure holding are performed, raising the oven temperature to 120°C and continuously evacuating for 2 hours before lowering the temperature back to 100°C, completing the pretreatment. After pretreatment, the substrate 200 can be plasma cleaned.

[0065] S10: The substrate is placed in the reaction furnace of the vacuum coating machine for cleaning. The Ar flow rate is 1000 sccm, the voltage (rotor bias voltage) is 600V, the duty cycle is 80%, and the cleaning time is 20 minutes.

[0066] S20, depositing the first film layer. Argon flow rate: 300 sccm, two pairs of chromium targets turned on, operating current: 8 A, rack bias: 200 V, duty cycle: 70%, duration: 60 min. The first film layer is a Cr layer.

[0067] S30, depositing a transition layer. The flow rate of argon is 300 sccm, and the flow rate of nitrogen is 40 sccm. One pair of silicon targets and two pairs of chromium targets are turned on, the working current is 10 A, the rotation bias (voltage) is 150 V, the duty cycle is 50%, and the duration is 90 min. The transition layer is CrSiN.

[0068] S40, depositing a second film layer. The flow rate of argon is 100 sccm, and the flow rate of acetylene is 10 sccm. Four pairs of chromium targets are turned on, the working current of the power supply is 10 A, the rotation bias (voltage) is 200 V, the duty cycle is 50%, and the duration is 25 min. The second film layer is CrC.

[0069] S50, depositing a third film layer. The flow rate of argon is 100 sccm, and the flow rate of acetylene is 10 sccm. Two pairs of chromium targets are turned on, the working current of the power supply is 6 A, the rotation bias (voltage) is 200 V, the duty cycle is 50%, and the duration is 3.5 min. The third film layer is CrC.

[0070] Example 2

[0071] The difference between Example 2 and Example 1 is that:

[0072] In S20, the flow rate of argon is 500 sccm, the working current is 6 A, the rotation bias is 100 V, the duty cycle is 40%, and the duration is 66 min;

[0073] In S30, the flow rate of argon is 150 sccm, the flow rate of nitrogen is 80 sccm, the working current is 6 A, the rotation bias (voltage) is 200 V, the duty cycle is 40%, and the duration is 99 min;

[0074] In S40, the flow rate of argon is 50 sccm, the flow rate of acetylene is 5 sccm, the working current is 14 A, the rotation bias (voltage) is 250 V, the duty cycle is 40%, and the duration is 27.5 min;

[0075] In S50, the flow rate of argon is 50 sccm, the flow rate of acetylene can be 5 sccm, the working current is 14 A, the rotation bias (voltage) is 250 V, the duty cycle is 40%, and the duration is 3.15 min.

[0076] Example 3

[0077] The difference between Example 3 and Example 1 is that:

[0078] In S20, the flow rate of argon is 150 sccm, the working current is 14 A, the rotation bias is 250 V, the duty cycle is 90%, and the duration is 54 min;

[0079] In S30, the flow rate of argon is 500 sccm, the flow rate of nitrogen is 25 sccm, the working current is 14 A, the rotating frame bias (voltage) is 250 V, the duty cycle is 90%, and the duration is 81 min.

[0080] In S40, the flow rate of argon is 300 sccm, the flow rate of acetylene is 35 sccm, the working current is 6 A, the rotating frame bias (voltage) is 100 V, the duty cycle is 90%, and the duration is 22.5 min.

[0081] In S50, the flow rate of argon is 300 sccm, the flow rate of acetylene is 35 sccm, the working current is 10 A, the rotating frame bias (voltage) is 100 V, the duty cycle is 90%, and the duration is 3.85 min.

[0082] Comparative Example 1

[0083] Comparative Example 1 differs from Example 1 in that step S50 is omitted, and a film as shown in Figure 4 is obtained. As shown in Figure 4 , the film of Comparative Example 1 includes the first film layer 20 (the first film layer 20 is located on the surface of the substrate 200), the transition layer 40, and the second film layer 20, which are sequentially arranged, and does not have the third film layer 30.

[0084] The films 100 prepared in Examples 1 to 3 are tested for color distribution, and a color distribution diagram as shown in Figure 5 is obtained. In the reaction furnace of the vacuum coating machine, the furnace body contains a total of 10 layers of upper, middle and lower layers, and the substrate 200 can be placed on the 10 layers for coating. The substrate 200 can have color difference due to different sputtering angles of the target material.

[0085] As can be seen from Figure 5 , in Examples 1 to 3 of the present application, the films 100 obtained from the substrates 200 of different layers in each example have relatively consistent and uniform color distribution. This indicates that the preparation method of the present application has high uniformity of color distribution of the films 100 in the upper, middle and lower layers in mass production.

[0086] The films of Example 1 and Comparative Example 1 are tested for colorimetric values using a color difference meter (manufacturer: Konica Minolta, model: CM3700A). The test results of the colorimetric values are shown in Table 1.

[0087] Table 1

[0088] L* a* b* Example 1 84.07 -0.17 1.85 Comparative Example 1 84.83 -0.23 -1

[0089] As shown in Table 1, the film in Example 1 has a b* value that changes from a negative value to a positive value while the L* and a* values remain unchanged, and the film in Example 1 has a warm color effect.

[0090] The films (surface layer) of Example 1 and Comparative Example 1 were tested for refractive index n and extinction coefficient k, and the test results are shown in Table 3. Figure 6 and Figure 7 As shown in Table 3, the refractive index n of the surface layer (third film layer) of the film in Example 1 is 1.2-3.3, and the extinction coefficient k is 1.8-4.3, within a wavelength range of 250 nm-800 nm. Figure 6 As shown in Table 3, the refractive index n of the surface layer (second film layer) of the film in Comparative Example 1 is 1-3.8, and the extinction coefficient k is 1.8-4.3, within a wavelength range of 250 nm-800 nm. Figure 7

[0091] The films of Examples 1-3 and Comparative Example 1 were analyzed by Energy Dispersive Spectrometer (EDS) combined with Scanning Electron Microscope (SEM). EDS bombards the surface of the film with an electron beam (test conditions: 10 kv, penetrating to the second film layer), excites the film to emit characteristic X-rays, and qualitatively and quantitatively analyzes the composition of the surface of the film according to the wavelength of the characteristic X-rays. The element types and contents (atomic percentage, representing the percentage of the number of atoms of a certain element in the total number of atoms) of the second film layer in Comparative Example 1, and the element types and contents (atomic percentage, representing the percentage of the number of atoms of a certain element in the total number of atoms) of the third film layer 30 and the second film layer 20 in Examples 1-3 are shown in Table 2 (other components are trace components that are commonly added during testing, such as oxygen atoms).

[0092] Table 2

[0093]

[0094]

[0095] In Comparative Example 1, the preparation steps of the second film layer are the same as those of the second film layer in Example 1, and therefore, the composition of the second film layer in Example 1 is basically the same as that of the second film layer in Comparative Example 1. As shown in Table 2, the atomic percentage (At%) of chromium in the third film layer and the second film layer in Example 1 is slightly lower than that in Comparative Example 1, indicating that the atomic percentage of chromium in the third film layer in Example 1 is lower than that in the second film layer.

[0096] ​When using energy dispersive spectroscopy coupled with scanning electron microscopy to perform elemental analysis on the surface of the thin films in Examples 1-3, the following results can also be obtained: Figure 8A to Figure 10B The electron microscope image shown.

[0097] Depend on Figure 8A It can be seen that in Example 1, the deposition of the third film layer 30 is relatively uniform. Figure 8B It can be seen that the thickness of the first film layer 20 is 195nm, the thickness of the transition film layer 40 is 568nm, and the thickness of the second film layer 20 is 195nm.

[0098] Depend on Figure 9A It can be seen that in Example 2, the deposition of the third film layer 30 is relatively uniform. Figure 9B It can be seen that the thickness of the first film layer 20 is 195nm, the thickness of the transition film layer 40 is 571nm, and the thickness of the second film layer 20 is 179nm.

[0099] Depend on Figure 10A It can be seen that in Example 3, the deposition of the third film layer 30 is relatively uniform. (From...) Figure 10B It can be seen that the thickness of the first film layer 20 is 195nm, the thickness of the transition film layer 40 is 574nm, and the thickness of the second film layer 20 is 182nm.

[0100] The films 100 of Examples 1-3 were subjected to chemical tests to assess their resistance to various chemicals commonly encountered in daily life. The chemicals used in the tests may include, but are not limited to: Banana Boat sunscreen, Ivory dishwashing liquid, Fantastik cleaning agent, yellow mustard, Coca-Cola, 70% isopropyl alcohol, extra virgin olive oil, petrolatum, ketchup, mayonnaise, 409 cleaning agent, sprays, acetone, artificial sweat, L'Oréal hairspray, Maybelline lipstick, Maybelline blush, sebum, hand sanitizer, black coffee, screen cleaner, Clorox disinfectant, and oleic acid.

[0101] After evenly coating the film surface with the aforementioned chemicals, store it under refrigeration or at 65°C and 90% humidity for 72 hours. Then clean the film, visually inspect it, and observe whether any discoloration, corrosion, or delamination occurs on the film surface, and record the grade. Grade A indicates no difference before and after the test; Grade B indicates a small area of ​​discoloration after the test, or discoloration only occurs when water vapor is sprayed onto the product; Grade Ca indicates obvious visual discoloration after the test (maximum 55% gray); Grade Cb indicates obvious visual discoloration after the test (maximum 70% gray); Grade Cc indicates obvious visual discoloration after the test (maximum 80% gray); Grade D indicates film damage and abnormal surface texture, but no corrosion points; Grade F indicates the film is corroded and delaminated.

[0102] The thin films of embodiments 1-3 of the present application, after being smeared with most of the above chemicals, most of the grades are B, that is, there is a small area of color difference after testing or there is color difference phenomenon when water vapor is sprayed on the product; after being smeared with Maybelline lipstick or Maybelline blush, the thin film has no difference before and after testing, and the grade is A; after being smeared with a small part of the chemicals, the grade is C.a. It shows that the thin films of embodiments 1-3 of the present application have good corrosion resistance and can fully meet the use requirements in daily life.

[0103] The thin film 100 and the preparation method thereof of the embodiments of the present application set a third film layer 30 with a suitable thickness, refractive index n and extinction coefficient k on the second film layer 20, and adjust the components of the second film layer 20 and the third film layer 30, so that the blue light reflected by the third film layer 30 destructively interferes (destructive interference) with the blue light reflected by the second film layer 20, and the yellow light reflected by the third film layer 30 constructively interferes (constructive interference) with the yellow light reflected by the second film layer 20, so that the chroma value b* of the thin film 100 changes from negative to positive, and then the thin film 100 has the effect of warm color system.

[0104] The above description is some specific embodiments of the present application, but in the actual application process, it cannot be limited to these embodiments only. Other modifications and changes made by those skilled in the art according to the technical concept of the present application should belong to the protection scope of the present application.

Claims

1. A thin film formed on a surface of a substrate, characterized by, The thin film comprises a first film layer, a second film layer and a third film layer arranged in sequence, The first film layer is arranged on the surface of the substrate, the second film layer comprises chromium carbide, the third film layer comprises chromium carbide, the atomic percentage of chromium in the third film layer is lower than that in the second film layer, the thickness of the second film layer is 100 nm to 2000 nm, the thickness of the third film layer is 10 nm to 20 nm, the refractive index n of the second film layer is 1 to 3.8 and the extinction coefficient k of the second film layer is 1.8 to 4.3 in the wavelength range of 250 nm to 800 nm of incident light, the refractive index n of the third film layer is 1.2 to 3.3 and the extinction coefficient k of the third film layer is 1.8 to 4.3 in the wavelength range of 250 nm to 800 nm of incident light, the blue light reflected by the third film layer and the blue light reflected by the second film layer superimpose to generate destructive interference, and the yellow light reflected by the third film layer and the yellow light reflected by the second film layer superimpose to generate constructive interference. The thin film further comprises a transition layer arranged between the first film layer and the second film layer, the thickness of the transition layer is 100 nm to 2000 nm, and the transition layer comprises chromium silicon nitride, titanium silicon nitride or tungsten silicon nitride.

2. The film of claim 1, wherein The thickness of the first film layer is 100 nm to 2000 nm, and the first film layer comprises chromium, titanium or tungsten.

3. The film of claim 1, wherein The thickness of the thin film is 950 nm to 6000 nm.

4. The film of claim 1, wherein The substrate is a conductive material or a plastic, the conductive material comprises a metal, silicon or carbon fiber, the metal comprises stainless steel, aluminum, titanium, copper, nickel or magnesium, and the plastic comprises one or more of polyvinyl chloride, polypropylene, polymethyl methacrylate, polystyrene, polyvinyl acetate, polyethylene terephthalate, styrene-acrylonitrile copolymer, ethylene-vinyl acetate copolymer, polycarbonate and polyamide.

5. An electronic product housing, characterized by, The substrate and the thin film as claimed in any one of claims 1 to 4.

6. A method of producing a housing for an electronic product, characterized by The method comprises the following steps: The substrate is placed in a reaction furnace of a vacuum coating machine for cleaning; Argon is introduced into the reaction furnace, and a power source and a target material are turned on to deposit a first film layer on the surface of the substrate; Argon and nitrogen are introduced into the reaction furnace, and the power source and the target material are turned on to deposit a transition layer on the surface of the first film layer; wherein the flow rate of the argon is 150 sccm to 500 sccm, the flow rate of the nitrogen is 25 sccm to 80 sccm, the target material comprises a silicon target, and further comprises a chromium target, a titanium target or a tungsten target, the working current of the power source is 6 A to 14 A, the voltage is 100 V to 250 V, the duty cycle is 40% to 90%, and the duration is 81 min to 99 min; Argon and a reaction gas are introduced into the reaction furnace, and the power source and the target material are turned on to deposit a second film layer on the surface of the transition layer, and the second film layer comprises chromium carbide; Argon and a reaction gas are introduced into the reaction furnace, and the power source and the target material are turned on to deposit a third film layer on the surface of the second film layer to obtain a thin film. The third film layer includes chromium carbide, the atomic percentage of chromium in the third film layer is lower than that in the second film layer, the thickness of the second film layer is 100 nm to 2000 nm, and the thickness of the third film layer is 10 nm to 20 nm; the refractive index n of the second film layer is 1 to 3.8 and the extinction coefficient k of the second film layer is 1.8 to 4.3 in the wavelength range of 250 nm to 800 nm of incident light; the refractive index n of the third film layer is 1.2 to 3.3 and the extinction coefficient k of the third film layer is 1.8 to 4.3 in the wavelength range of 250 nm to 800 nm of incident light; the blue light reflected by the third film layer and the blue light reflected by the second film layer superimpose to produce destructive interference, and the yellow light reflected by the third film layer and the yellow light reflected by the second film layer superimpose to produce constructive interference; the thickness of the transition layer is 100 nm to 2000 nm, and the transition layer includes chromium silicon nitride, titanium silicon nitride or tungsten silicon nitride.

7. The preparation method of claim 6, wherein, In the step of depositing the first film layer, the flow rate of the argon is 150 sccm to 500 sccm, the target material includes a chromium target, a titanium target or a tungsten target, the working current of the power supply is 6 A to 14 A, the voltage is 100 V to 250 V, the duty cycle is 40% to 90%, and the duration is 54 min to 66 min; In the step of depositing the second film layer, the flow rate of the argon is 50 sccm to 300 sccm, the flow rate of the reaction gas is 5 sccm to 35 sccm, the reaction gas includes methane or acetylene, the target material includes a chromium target, the number of the chromium target is W1, the working current of the power supply is I1, I1 is 6 A to 14 A, the voltage is 100 V to 250 V, the duty cycle is 40% to 90%, and the duration is T1, T1 is 22.5 min to 27.5 min; In the step of depositing the third film layer, the flow rate of the argon is 50 sccm to 300 sccm, the flow rate of the reaction gas is 5 sccm to 35 sccm, the reaction gas includes methane or acetylene, the target material includes a chromium target, the number of the chromium target is W2, the working current of the power supply is I2, I2 is 6 A to 14 A, the voltage is 100 V to 250 V, the duty cycle is 40% to 90%, and the duration is T2, T2 is 3.15 min to 3.85 min; W2 < W1, I2 < I1, and T2 < T1.

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