A diamond-like composite film for food preservation, its preparation method and application

Abstract

This invention provides a diamond-like carbon (DLC) composite film for food preservation, its preparation method, and its application. The structure of the DLC composite film includes a base layer and a DLC composite coating fixed to at least one surface of the base layer. The DLC composite coating includes an intermediate transition layer, a metal-doped DLC functional layer, and a surface modification layer sequentially disposed therefrom. This application utilizes the SP-rich content in the DLC composite coating... 3 The dense structure of hybrid carbon bonds, combined with a multilayer composite design, makes the composite film significantly superior to traditional food preservation films in terms of its barrier properties against oxygen and water vapor. The diamond-like carbon coating described in this application can significantly improve the gas barrier properties of polymer materials, preventing oxygen from penetrating the packaging and effectively delaying the oxidative spoilage of food. Experimental data shows that the oxygen permeability of the composite film of this invention can be reduced to 0.73 cc / m. 2 / 24h / atm, meeting the high barrier requirements for food preservation packaging.

Description

Technical Field

[0001] This invention belongs to the field of food packaging technology, specifically relating to a diamond-like composite film for food preservation, its preparation method, and its application. Background Technology

[0002] Food packaging and preservation materials are crucial for ensuring food safety and extending shelf life. Traditional plastic films such as polyethylene (PE), polypropylene (PP), and polyester (PET) are widely used due to their low cost and good processing performance; however, their barrier properties against gases such as oxygen and water vapor are limited. Low-molecular-weight oxygen can still penetrate the plastic film and enter the packaging, causing oxidation and spoilage of the packaged food, thus reducing its preservation effect. Furthermore, traditional plastic films lack antibacterial properties and are easily adhered to by microorganisms during room temperature storage and transportation, further shortening shelf life and posing safety hazards.

[0003] To improve the barrier properties of plastic packaging materials, various surface coating treatments have been employed in existing technologies. One type of technology involves depositing silicon oxide or aluminum oxide coatings on the surface of the plastic film, but this suffers from poor mechanical ductility and insufficient adhesion. Another type involves depositing silicon-doped diamond-like carbon (Si-DLC) layers on the surface of food containers. While this can improve oxygen barrier properties and mechanical properties, its deposition process requires high temperatures and is difficult to achieve large-area uniform coating on highly flexible food preservation films. Other literature reports multilayer plastic film treatment schemes containing transition layers and titanium-doped diamond-like carbon layers, but these schemes are mainly used to improve hydrophobic and oleophobic properties, and lack a systematic design for the comprehensive gas barrier, antibacterial, and preservation effects required for freshness preservation.

[0004] Nanodiamond materials have also been explored for applications in food preservation. For example, adding nanodiamonds to polymer coatings can improve coating stability and delay the formation of micropores, thereby extending the shelf life of fruits; or preparing polyvinyl alcohol-nanodiamond composites to achieve antibacterial and UV protection functions. However, in these methods, nanodiamonds are dispersed in the matrix as fillers, leading to problems such as uneven dispersion, easy migration and failure of functional additives, and insufficient adaptability to multilayer packaging structures. Furthermore, existing diamond-like carbon (DLC) coatings still require further improvement in low-temperature deposition, adhesion enhancement, and safety in contact with food.

[0005] Therefore, there is an urgent need to develop a food preservation composite film that combines high gas barrier properties, excellent antibacterial properties, good biocompatibility, and ease of processing to meet the needs of high-end food preservation packaging. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a diamond-like carbon (DLC) food preservation composite film with high gas barrier properties, excellent antibacterial properties, good biocompatibility, and ease of processing, along with its preparation method and applications. The DLC composite film of this invention is particularly suitable for the preservation packaging of fruits and vegetables, chilled meat, seafood, and high-fat foods, effectively solving the problems of insufficient gas barrier and antibacterial properties, easy coating peeling, and limited functionality in existing food preservation packaging materials.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A diamond-like carbon composite film for food preservation includes a base layer and a diamond-like carbon composite coating fixed to at least one surface of the base layer; the diamond-like carbon composite coating includes an intermediate transition layer, a diamond-like carbon functional layer doped with metal elements, and a surface modification layer arranged sequentially from the inside to the outside.

[0008] The base layer is any one of PE preservation film, PP preservation film, PET preservation film or PVDC preservation film, preferably a food-grade plastic film with a thickness of 10~50μm.

[0009] The intermediate transition layer is either a carbon transition layer or a carbon-silicon composite transition layer, preferably with a thickness of 5-20 nm; the intermediate transition layer is used to enhance the bonding force between the base layer and the diamond-like functional layer.

[0010] The molar ratio of carbon to silicon in the carbon-silicon composite transition layer is 1.5:1 to 4:1.

[0011] The metal-doped diamond-like functional layer is a titanium-doped diamond-like carbon layer (Ti-DLC) or a silver-doped diamond-like carbon layer (Ag-DLC), preferably with a thickness of 15~35 nm; The atomic doping amount of metal elements in the diamond-like carbon functional layer is 0.5%~8.0%; titanium doping can improve the hardness and wear resistance of the film, and silver doping can impart antibacterial activity to the film.

[0012] The surface modification layer is a fluorinated organic coating or a siloxane-containing modification layer, preferably with a thickness of 2~15 nm; the surface modification layer is used to impart a synergistic function of hydrophobicity and oleophobicity and to reduce bacterial adhesion to the surface of the composite film.

[0013] Preferably, the total thickness of the diamond-like composite coating is 30~60 nm; too small a thickness will result in insufficient barrier performance, while too large a thickness will easily lead to increased coating brittleness and peeling risk.

[0014] An organosilane interlayer is further provided between the intermediate transition layer and the metal-doped diamond-like carbon functional layer. Preferably, the organosilane interlayer is an aminosilane coupling agent interlayer with a thickness of 2~10 nm. This interlayer is used to fill microcracks that may occur in the diamond-like carbon coating and improve the overall gas barrier performance.

[0015] The method for preparing the diamond-like carbon composite film for food preservation includes the following steps: (1) Plasma pretreatment of the substrate; (2) Deposit the intermediate transition layer on the surface of the base layer; (3) Deposit the diamond-like functional layer with metal doping on the surface of the intermediate transition layer; (4) Deposit the surface modification layer on the surface of the diamond-like functional layer doped with metal elements; (5) Post-process the composite film obtained by depositing the surface modification layer in step (4) to obtain the diamond-like composite film for food preservation.

[0016] In step (1), the specific operation for plasma pretreatment of the substrate is as follows: the substrate is placed in a vacuum chamber, argon gas is introduced, and the background vacuum degree of the vacuum chamber is controlled to be ≤5×10. -3 Argon gas is introduced to bring the chamber pressure to 0.5~2.0 Pa. The bias power supply and plasma source are turned on to etch and clean the thin film surface for 5~30 min to remove surface adsorbed impurities and improve surface activity.

[0017] In step (2), the specific operation of depositing the intermediate transition layer on the substrate surface is as follows: maintain the vacuum chamber temperature at 20~50℃, control the working gas pressure at 0.5~1.5Pa, introduce argon or a mixture of argon and methane, and use magnetron sputtering or plasma-enhanced chemical vapor deposition to deposit a carbon transition layer or a carbon-silicon composite transition layer on the substrate surface; the deposition parameters are: target current 0.5~2.0A, negative bias voltage -180 V~-100V, bias frequency 50~200 kHz, deposition time 5~20 min, forming an intermediate transition layer with a thickness of 5~20 nm.

[0018] In step (3), the specific operation of depositing the metal-doped diamond-like carbon functional layer on the surface of the intermediate transition layer is as follows: maintain the chamber temperature at 20~50℃, co-sputter deposit a titanium-doped diamond-like carbon layer or a silver-doped diamond-like carbon layer on the surface of the intermediate transition layer; adopt the co-sputtering method of carbon target and metal target, carbon target current 1.5~4.0 A, metal target current 0.3~1.5 A, negative bias voltage -200 V~-80 V, bias voltage frequency 80~200 kHz, argon or argon / nitrogen mixed gas is introduced, the working gas pressure is controlled at 0.3~1.0 Pa, the deposition time is 10~40 min, and a metal-doped diamond-like carbon functional layer with a thickness of 15~35 nm is formed.

[0019] In steps (2) to (3), the deposition of the intermediate transition layer, the diamond-like functional layer doped with metal elements, and the surface modification layer are all carried out using magnetron sputtering or plasma-enhanced chemical vapor deposition. The temperature of the vacuum chamber during the deposition process is 20~50℃, and the temperature of the substrate during the deposition process is not higher than 60℃.

[0020] In step (4), the specific operation of depositing the surface modification layer on the surface of the metal-doped diamond-like functional layer is as follows: maintain the chamber temperature at 25~50℃, and deposit a fluorinated organic coating or a siloxane-containing modification layer on the surface of the metal-doped diamond-like functional layer; the fluorinated organic coating is deposited by introducing a fluorinated precursor gas (such as C4F8, C2F6 or CHF3) and turning on the plasma source, controlling the precursor gas flow rate at 10~50 sccm, the radio frequency power at 50~200 W, and the deposition time at 2~15 min to form a fluorocarbon surface layer with a thickness of 2~15 nm; or a low surface energy siloxane solution is coated by dip-coating, and a hydrophobic and oleophobic surface modification layer is formed after thermal curing.

[0021] In step (5), the specific operation of the post-processing is as follows: the deposited composite film is left to age at room temperature for 6~24h, or kept at 40~60℃ under vacuum for 1~4h, in order to eliminate the internal stress of the coating and enhance the density of the film layer.

[0022] Throughout the deposition process, the temperature of the vacuum chamber is controlled at 20~50℃, and the temperature of the base plastic film does not exceed 60℃ during deposition to ensure that the heat-sensitive plastic film does not deform or degrade. The preferred manufacturing process utilizes a roll-to-roll continuous PECVD or magnetron sputtering production line to achieve industrial-scale mass production.

[0023] The diamond-like carbon composite film is used in food preservation. As a barrier and antibacterial functional layer in packaging films, it is used for the preservation packaging of fruits and vegetables, fresh meat, seafood, dairy products, or cooked foods.

[0024] Research has revealed that the diamond-like carbon (DLC) composite coating described in this invention is rich in sp. 3 The dense structure of hybrid carbon bonds is a metastable amorphous network structure, and its specific characteristics can be described from three aspects: bonding composition, spatial morphology, and structural properties. (a) Bonding constitutes core features Structure with sp 3 Hybridized carbon bonds constitute the majority (sp in tetrahedral amorphous carbon ta-C subtype) 3 The content can exceed 80%, while mixing in a small amount of SP. 2 Hybridized carbon bonds regulate toughness, and hydrogen-containing subtypes also contain a certain number of CH bonds to fill pores. 3 The hybrid carbon-carbon bonds are shorter and have higher bond energies, providing core strength support for the dense structure.

[0025] (b) Spatial stacking morphology Overall, it exhibits amorphous packing with long-range disorder and short-range order: sp 3 Hybridized carbon atoms are interconnected in a tetrahedral coordination manner, forming a continuous three-dimensional covalent network framework; a small amount of sp... 2 Hybrid carbon atoms are mostly dispersed in the form of nanoclusters to fill the gaps in the framework, and will not form long-range graphite crystal regions; the novel gradient composite structure will also construct a honeycomb-like three-dimensional framework by implanting nanocrystal seeds, further optimizing the compactness and avoiding porosity defects.

[0026] (c) Performance benefits derived from the structure This dense structure allows the coating to achieve a hardness of ≥60GPa (approximately 6000~10000HV) while maintaining extremely low porosity and surface roughness that can be controlled at the nanometer level. It retains the ultra-high hardness and wear resistance of diamond while avoiding the brittleness of pure crystalline diamond through its amorphous structure, and also has good toughness and substrate compatibility.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention provides a diamond-like carbon composite film for food preservation, comprising a base layer and a diamond-like carbon composite coating fixed to at least one surface of the base layer; the diamond-like carbon composite coating comprises an intermediate transition layer, a diamond-like carbon functional layer doped with metal elements, and a surface modification layer arranged sequentially from the inside to the outside; thereby, this application utilizes the diamond-like carbon composite coating rich in sp... 3 The dense structure of hybrid carbon bonds, combined with a multilayer composite design, makes the composite film significantly superior to traditional food preservation films in terms of its barrier properties against oxygen and water vapor. The diamond-like carbon coating described in this application can significantly improve the gas barrier properties of polymer materials, preventing oxygen from penetrating the packaging and effectively delaying the oxidative spoilage of food. Experimental data shows that the oxygen permeability of the composite film of this application can be reduced to 0.73 cc / m.2 The coating operates at 24h / atm, meeting the high barrier requirements for food preservation packaging. Simultaneously, the diamond-like carbon (DLC) coating is microwave-permeable, ensuring it does not interfere with microwave heating processes within the food packaging.

[0028] (2) This application incorporates antibacterial active metal elements such as silver into the diamond-like carbon functional layer, giving the film continuous physical antibacterial properties, which can effectively inhibit bacterial growth on the surface of food packaging; furthermore, the hydrophobic and oleophobic synergistic effect of the surface modification layer significantly reduces microbial adhesion and stain attachment, providing double protection for food hygiene and safety. The diamond-like carbon film itself also has good anti-mildew properties, further enhancing the hygiene and safety of food packaging.

[0029] (3) The diamond-like composite coating described in this application has excellent chemical inertness and biocompatibility. It does not react with general organic and inorganic acids, alkalis, salts, oils, etc., and will not migrate harmful substances into food, thus meeting the hygiene and safety standards for food packaging materials.

[0030] (4) This application significantly enhances the adhesion between the coating and the plastic substrate through plasma pretreatment and the design of an intermediate transition layer. The presence of the intermediate transition layer makes the adhesion of the diamond-like carbon functional layer stronger, the film more uniform, and less prone to peeling off, effectively solving the problem of poor adhesion of traditional inorganic barrier coatings. This application adopts a roll-to-roll low-temperature continuous deposition process, which is suitable for large-scale industrial production and is green and environmentally friendly.

[0031] (5) The diamond-like composite film prepared by the present invention does not contain aluminum foil, has good flexibility and transparency, and the packaging substrate can be repeatedly recycled, coated and reused, saving energy and materials, which is in line with the development direction of circular economy and green packaging. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Example 1 This embodiment provides a diamond-like composite film for food preservation, the structure of which includes a base PET film and a diamond-like composite coating fixed on the surface of the base film; the diamond-like composite coating includes a carbon transition layer, an organosilane interlayer, a silver-doped diamond-like functional layer and a fluorocarbon surface modification layer arranged sequentially from the inside to the outside.

[0034] The method for preparing the diamond-like carbon composite film for food preservation includes the following steps: (1) Take a 20μm thick food-grade PET film as the base layer, place it in the vacuum chamber, and evacuate to a background vacuum of 1.0×10. -3 Argon gas was introduced to bring the chamber pressure to 1.0 Pa, and plasma etching and cleaning was initiated for 15 minutes, with the temperature controlled at 25°C.

[0035] (2) Deposition of carbon transition layer. The vacuum chamber temperature was kept at 25°C and the working pressure was 0.8 Pa. A mixture of argon and methane gas (volume ratio 1:2) was introduced. Medium frequency magnetron sputtering technology was used with carbon target current of 1.2 A, negative bias voltage of -150 V, bias frequency of 150 kHz, and deposition time of 8 min to form a carbon transition layer with a thickness of 12 nm.

[0036] (3) Add an organosilane interlayer. Immerse the PET film with the carbon transition layer in a 2% (w / w) γ-aminopropyltriethoxysilane (KH-550) ethanol solution for 10 min, then remove it and dry and cure it in an oven at 60°C for 30 min to form an organosilane interlayer with a thickness of 6 nm.

[0037] (4) Deposition of silver-doped diamond-like carbon functional layer. The vacuum chamber temperature was maintained at 30℃, the working pressure at 0.6 Pa, and argon gas was introduced. A co-sputtering method with carbon and silver targets was used, with a carbon target current of 3.0 A, a silver target current of 0.6 A, a negative bias voltage of -130 V, a bias frequency of 120 kHz, and a deposition time of 20 min to form a silver-doped diamond-like carbon layer with a thickness of 25 nm and a silver doping amount of 3.5%.

[0038] (5) Deposition of fluorocarbon surface modification layer. The chamber temperature was maintained at 30°C, and C4F8 precursor gas was introduced at a flow rate of 25 sccm, RF power of 120 W, and deposition time of 5 min to form a fluorocarbon coating with a thickness of 8 nm.

[0039] (6) Post-processing. The deposited composite film was kept at 50°C under vacuum for 2 h and then cooled naturally to obtain a diamond-like composite film for food preservation.

[0040] Example 2 This embodiment provides a diamond-like composite film for food preservation, the structure of which includes a base PE film and a diamond-like composite coating fixed on the surface of the base film; the diamond-like composite coating includes a carbon-silicon composite transition layer, a titanium-doped diamond-like functional layer (titanium-doped diamond-like carbon layer) and a siloxane surface modification layer arranged sequentially from the inside to the outside.

[0041] The method for preparing the diamond-like carbon composite film for food preservation includes the following steps: (1) Take a food-grade PE film with a thickness of 25μm as the base layer, place it in the vacuum chamber, and evacuate to a base vacuum degree of 1.0×10. -3 Argon gas was introduced to bring the chamber pressure to 1.0 Pa, and plasma etching and cleaning was initiated for 15 minutes, with the temperature controlled at 25°C.

[0042] (2) Deposition of carbon-silicon composite transition layer. A carbon target and a silicon target co-sputtering method is used, with a carbon target current of 1.0 A, a silicon target current of 0.3 A, a negative bias voltage of -140 V, a bias voltage frequency of 130 kHz, and a deposition time of 10 min to form a carbon-silicon composite transition layer with a thickness of 15 nm, wherein the ratio of carbon to silicon in the carbon-silicon composite transition layer is 2~2.5:1.

[0043] (3) Deposition of titanium-doped diamond functional layer. The vacuum chamber temperature was maintained at 30℃, the working pressure at 0.5 Pa, and argon gas was introduced. Co-sputtering with carbon and titanium targets was used. The carbon target current was 3.5 A, the titanium target current was 0.8 A, the negative bias voltage was -120 V, the bias voltage frequency was 120 kHz, and the deposition time was 25 min to form a titanium-doped diamond carbon layer with a thickness of 30 nm and a titanium doping amount of 4.0%.

[0044] (4) Deposition of siloxane surface modification layer. An ethanol solution containing hydrophobic siloxane (mass fraction 0.5%) was coated on the surface of the titanium-doped diamond layer using the dip-coating method at a speed of 20 cm / min. After drying at room temperature, the coating was heat-cured at 60℃ for 30 min to form a siloxane surface modification layer with a thickness of about 5 nm.

[0045] (5) Post-processing. The deposited composite film was kept at 50°C under vacuum for 2 h and then cooled naturally to obtain a diamond-like composite film for food preservation.

[0046] Comparative Example 1 This comparative example uses the same PET substrate as Example 1, but without the diamond-like carbon composite coating, and its barrier properties are directly tested. See Table 1 for details.

[0047] Comparative Example 2 This comparative example provides a composite film for food preservation, which differs from Example 1 only in that the composite film layer includes a PET base layer, a carbon transition layer and a fluorocarbon surface modification layer arranged sequentially.

[0048] Comparative Example 3 This comparative example provides a composite film for food preservation, which differs from Example 1 only in that the composite film layer includes a PET base layer, a carbon transition layer, an organosilane interlayer, and a fluorocarbon surface modification layer arranged sequentially.

[0049] Experimental Example The oxygen permeability and water vapor permeability of the diamond-like carbon (DLC) film before and after the film formation described in Example 1 are compared, as shown in Table 1.

[0050] Table 1 - Comparison of oxygen permeability and water vapor permeability before and after diamond-like carbon (DLC) film formation. As shown in Table 1, the oxygen permeability is increased by 26 times and the water vapor permeability is increased by 13 times, which means that oxygen and water vapor are effectively blocked, thus achieving a better preservation effect.

[0051] Fresh blueberries were packaged using the diamond-like carbon composite film prepared in Example 1, the film prepared in Example 2, the uncoated PET film of Comparative Example 1, and commercially available PE preservation film, 100 g per package, and stored at 4°C for 15 days. The sensory quality, weight loss rate, and spoilage rate of each group of blueberries were observed and measured daily. The sensory quality of the blueberries during storage was scored on a 5-point scale. A score of 5 indicates freshness, no water loss, and good color; a score of 1 indicates severe spoilage and inedibility; scores of 2 to 4 are between 1 and 5, with freshness increasing sequentially. Details are shown in the table below.

[0052] Table 2 - Comparison of the preservation effects of different composite films as packaging films As shown in Table 1, the diamond-like carbon composite film described in this application possesses high gas barrier properties, excellent antibacterial properties, good biocompatibility, and ease of processing. When used for blueberry preservation, it maintains good fruit firmness and color on day 15, with a weight loss rate of less than 5% and no obvious flavor spoilage, making it suitable for preserving fruits, vegetables, or food. In contrast, the films in Comparative Examples 1-3 and commercially available preservation films showed significant water loss and wilting in blueberries around day 10-12, with some blueberries exhibiting mold spots and a weight loss rate of 8-12%. Therefore, the preservation performance of the composite film in this application is superior to that of the films in Comparative Examples 1-3.

[0053] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A diamond-like composite film for food preservation, characterized in that, The material includes a base layer and a diamond-like composite coating fixed to at least one side of the base layer; the diamond-like composite coating includes an intermediate transition layer, a diamond-like functional layer with metal elements, and a surface modification layer arranged sequentially from the inside to the outside.

2. The diamond-like composite film for food preservation according to claim 1, characterized in that, The base layer is any one of PE preservation film, PP preservation film, PET preservation film or PVDC preservation film, preferably with a thickness of 10~50 μm.

3. The diamond-like carbon composite film for food preservation according to claim 1 or 2, characterized in that, The intermediate transition layer is either a carbon transition layer or a carbon-silicon composite transition layer, and preferably has a thickness of 5~20 nm. The molar ratio of carbon to silicon in the carbon-silicon composite transition layer is 1.5:1 to 4:

1.

4. The diamond-like composite film for food preservation according to claim 1, characterized in that, The metal-doped diamond-like functional layer is a titanium-doped diamond-like carbon layer or a silver-doped diamond-like carbon layer, preferably with a thickness of 15~35 nm. The atomic doping amount of the metal element in the metal-doped diamond-like functional layer is 0.5% to 8.0%.

5. The diamond-like composite film for food preservation according to claim 1, characterized in that, The surface modification layer is a fluorine-containing organic coating or a siloxane-containing modification layer, preferably with a thickness of 2~15 nm; Preferably, the total thickness of the diamond-like composite coating is 30~60 nm.

6. The diamond-like composite film for food preservation according to claim 1, characterized in that, An organosilane interlayer is further provided between the intermediate transition layer and the metal-doped diamond-like functional layer. Preferably, the organosilane interlayer is an aminosilane coupling agent interlayer with a thickness of 2~10 nm.

7. The method for preparing a diamond-like composite film for food preservation according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Plasma pretreatment of the substrate; (2) Deposit the intermediate transition layer on the surface of the base layer; (3) Deposit the diamond-like functional layer with metal doping on the surface of the intermediate transition layer; (4) Deposit the surface modification layer on the surface of the diamond-like functional layer doped with metal elements; (5) Post-process the composite film obtained by depositing the surface modification layer in step (4) to obtain the diamond-like composite film for food preservation.

8. The method for preparing a diamond-like composite film for food preservation according to claim 7, characterized in that, In steps (2) to (4), the intermediate transition layer, the metal-doped diamond-like functional layer, and the surface modification layer are deposited using magnetron sputtering or plasma-enhanced chemical vapor deposition. The temperature of the vacuum chamber during the deposition process is 20~50℃, and the temperature of the substrate during the deposition process is not higher than 60℃.

9. The method for preparing a diamond-like composite film for food preservation according to claim 7, characterized in that, In step (5), the specific operation of the post-processing is as follows: the deposited composite film is left to age at room temperature for 6~24h, or kept at 40~60℃ under vacuum for 1~4h.

10. The application of the diamond-like composite film according to any one of claims 1-7 in food preservation.

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