Liquid-repellent film and packaging material including the same

Abstract

To identify a more excellent liquid repellent film structure and supply such a liquid repellent film stably.SOLUTION: A liquid repellent film 10 comprises: hydrophilic particles 4; and a resin 6 having a liquid repellent part. The hydrophilic particles 4 form an irregular structure, and the resin 6 having the liquid repellent part covers at least a surface of the irregular structure. The liquid repellent film is configured so that: (a) a front layer part of the liquid repellent film 10 includes carbon, fluorine, oxygen and silicon, and with a total amount of atoms of the carbon, fluorine, oxygen and silicon on the front layer part measured by an X-ray photoelectron spectroscopy (XPS) as a reference, a content of the fluorine is 25 atom% or more, and 50 atom% or less; (b) a range from the front layer part to an inside of the liquid repellent film 10 includes the carbon, the fluorine, the oxygen and the silicon, and with a total number of atoms of the carbon, fluorine, oxygen and silicon as a reference, in a range from the front layer part to the inside measured on the basis of chemical element mapping data by an SEM-EDS method, a content of the fluorine is 5 atom% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a liquid-repellent article whose surface exhibits excellent liquid-repellent properties against water and oil, and relates to a liquid-repellent film that imparts properties to the surface of packaging materials for contents such as food, medicines, cosmetics, and daily necessities that prevent the contents from adhering to the surface. [Background technology]

[0002] Conventionally, a liquid-repellent film has been formed on the surface of packaging materials for various contents to prevent the contents from adhering to the surface. For example, Patent Document 1 discloses a liquid-repellent film that can be produced at low cost, can be made from a variety of materials for the base material, is thin, and has excellent transparency.

[0003] The liquid-repellent film of Patent Document 1 is formed by laminating a base coat layer and a top coat layer on a substrate film, and a large uneven structure is formed in the base coat layer by fixing large-diameter particles to the surface of the substrate film with a thermoplastic resin, and a small uneven structure is formed in the top coat layer by fixing small-diameter particles to the surface of the base coat layer with a resin having liquid-repellent portions, thus forming an uneven structure with severe undulations as a whole. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 6522841 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors formed liquid-repellent films under various conditions in order to put them into practical use, and found that some of them exhibited superior liquid-repellent properties. Therefore, an object of the present invention is to identify a film structure that exhibits superior liquid-repellent properties and to provide such liquid-repellent films in a stable manner. [Means for solving the problem]

[0006] After extensive research, the inventors focused on the fluorine atom content ratio in the surface layer of the liquid-repellent film and the fluorine atom content ratio in the range from the surface layer to the interior of the liquid-repellent film. They found that when these ratios are within a predetermined range, the liquid-repellent film exhibits superior liquid repellency, which led to the completion of the present invention.

[0007] That is, the liquid-repellent film of the present invention is hydrophilic. Fumed Silica Microparticles Particles and liquid-repellent areas and fluorine-based copolymers containing hydrophilic moieties and a resin, Fumed Silica Microparticles The particles form a rough structure, Fluorine-based copolymer At least the surface of the concave-convex structure is covered with a resin. It is configured as follows: A liquid-repellent film, (a) the liquid-repellent film Range from the surface to a depth of 5 nm contains carbon, fluorine, oxygen and silicon, and the Range from the surface of the liquid-repellent film to a depth of 5 nm The fluorine content is 25 atomic % or more and 50 atomic % or less based on the total number of carbon, fluorine, oxygen and silicon atoms, (b) the liquid-repellent film 2 to 3 μm deep from the surface The range includes carbon, fluorine, oxygen and silicon, and is measured based on element mapping data by SEM-EDS method. 2 to 3 μm depth from the surface of the liquid-repellent film The fluorine content is 5 atomic % or less based on the total number of carbon, fluorine, oxygen and silicon atoms in the range the law of nature, (c) In the area from the surface of the liquid-repellent film to a depth of 5 nm, the ratio of the fluorine content to the silicon content is in the range of 3 to 4. It is characterized by the fact that

[0008] In the liquid-repellent film of the present invention, Range from the surface of the liquid-repellent film to a depth of 5 nm In the case of fluorine content is higher than oxygen content, 2 to 3 μm depth from the surface of the liquid-repellent film In the range up to 10 ...

[0010] The packaging material of the present invention is characterized by comprising a substrate and the above-described liquid-repellent film formed on the substrate. [Effects of the Invention]

[0011] According to the present invention, it has been revealed that a liquid-repellent film exhibiting superior liquid repellency can be formed by controlling the fluorine content in the surface layer of the liquid-repellent film to 25 atomic % or more and 50 atomic % or less, and controlling the fluorine content in the range from the surface layer to the interior of the liquid-repellent film to 5 atomic % or less. More preferably, the fluorine content is 30 atomic % or more and 45 atomic % or less in the surface layer portion, and 4 atomic % or less in the range from the surface layer portion to the interior. Here, X-ray photoelectron spectroscopy (XPS) measures the content (atomic percent) of fluorine and other elements present in the range from the surface of the surface layer of the liquid-repellent film to a depth of approximately 5 nm, and SEM-EDS (also called SEM-EDX) measures the content (atomic percent) of fluorine and other elements present in the range from the surface of the surface layer of the liquid-repellent film to a depth of approximately 2 to 3 μm based on element mapping data. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram schematically illustrating a cross-sectional structure of a liquid-repellent film according to an embodiment. [Figure 2] FIG. 10 is an SEM image and a diagram of the SEM-EDS analysis results of the liquid-repellent film of Example 3-4. [Figure 3] FIG. 10 is an SEM image and a diagram of SEM-EDS analysis results of the liquid-repellent film of Comparative Example 2-3. [Figure 4] FIG. 10 is an SEM image and a diagram of SEM-EDS analysis results of the liquid-repellent film of Comparative Example 4-5. [Figure 5] FIG. 1 is a diagram showing the results of XPS analysis of a liquid-repellent film produced under the same conditions as in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will now be described in detail with reference to the drawings. Figure 1 is a schematic cross-sectional view of a liquid-repellent film 10 according to a first embodiment.

[0014] (base material) The substrate 2 is not particularly limited as long as it can serve as a support, and has at least one layer made of a resin-containing film, paper, or metal foil. The resin-containing film may be at least one resin film selected from styrene-based resins, olefin-based resins, polyester-based resins, nylon-based resins, ethylene-vinyl alcohol copolymers, and acrylic-based resins. When the substrate 2 is multilayered, the lamination method is not particularly limited, and methods such as dry lamination, wet lamination, and heat lamination can be used. The substrate 2 may also be subjected to inorganic or metal vapor deposition treatment. The substrate 2 may be printed, and the printing method is not particularly limited, and known methods such as gravure printing, flexographic printing, and screen printing can be used.

[0015] The thickness of the substrate 2 is not particularly limited, but a thickness of 1 to 200 μm is generally used for a film, and a thickness of about 200 μm to 10 mm is generally used for a sheet.

[0016] (liquid repellent film) The liquid-repellent film 10 is a film having liquid-repellent properties, and is formed so as to cover the surface of the substrate 2 as shown in Figure 1. The liquid-repellent film 10 is formed by applying a liquid-repellent layer paint containing hydrophilic particles 4 and a resin 6 having liquid-repellent portions to the surface of the substrate 2 and drying it.

[0017] (hydrophilic particles) Although fine hydrophilic oxide particles such as titanium oxide, zinc oxide, and aluminum oxide can be used as the hydrophilic particles 4, it is particularly preferable to prepare a coating using hydrophilic silica fine particles with an average primary particle diameter of 7 to 40 nm. During the coating process, some of the hydrophilic silica fine particles with this particle size will form a moderate agglomeration state, and the resin 6 having liquid-repellent moieties will be retained in the porous voids formed in the agglomerates 8, contributing to the low wettability of the surface of the liquid-repellent film 10. The surface of the substrate 2 is covered with agglomerates 8 of hydrophilic particles 4, and the surfaces of the agglomerates 8 of hydrophilic particles 4 are covered with the resin 6.

[0018] (Resin with liquid-repellent portion) The liquid-repellent portion is preferably made of a fluororesin, and the portion containing a fluororesin is preferably a resin composition containing, for example, a perfluoroalkyl group, a polyfluoroalkyl group, or a perfluoropolyether group.

[0019] (Liquid-repellent film thickness and contact angle) The thickness of the liquid-repellent film 10 is not particularly limited, but is preferably 100 nm to 1.5 μm. Furthermore, the contact angle when contacting oleic acid is preferably 130 degrees or more, which provides practical liquid repellency. Furthermore, the contact angle when contacting hexadecane is preferably 120 degrees or more.

[0020] (How to apply liquid-repellent coating) The liquid-repellent film 10 is formed by applying a liquid-repellent layer coating material, in which hydrophilic particles 4 and a resin 6 having liquid-repellent moieties are dissolved or dispersed in a solvent, onto the substrate 2 and then drying the coating material. The solvent is not particularly limited, but examples include water, ethanol, isopropyl alcohol (IPA), n-butyl alcohol, and other alcohols. After application, the coating material is preferably dried by heating in air at a temperature of 50°C or higher and lower than 300°C.

[0021] (Fluorine content) The inventors focused on the fluorine content (atomic percent) in the surface layer of the liquid-repellent film 10 and the fluorine content (atomic percent) in the range from the surface layer to the interior of the liquid-repellent film 10, and found that the liquid-repellent film 10 exhibits superior liquid repellency when these values ​​are within a predetermined range. The predetermined range is 25 atomic % or more and 50 atomic % or less in the surface layer, and 5 atomic % or less in the range from the surface layer to the interior. In other words, it is better for the fluorine that exhibits liquid repellency to be concentrated in the surface layer of the liquid-repellent film 10, and it is better for the liquid-repellent film 10 as a whole to have a lower fluorine content.

[0022] The fluorine content in the surface layer of the liquid-repellent coating 10 is closely related to the liquid repellency. Fluorine atoms easily bond with all elements, and the bond with carbon atoms (C—F bonds) is particularly strong. Fluorine compounds that have such C—F bonds on their surface are in the most stable state, and the force of attraction between fluorine compound molecules (intermolecular cohesive energy) is weak, resulting in low surface tension and thus excellent liquid repellency.

[0023] The surfaces of hydrophilic particles 4 (metal oxide particles) or their aggregates 8 are usually covered with surface functional groups such as hydroxyl groups, which impart hydrophilicity, moisture adsorption, and high cohesiveness and adhesiveness to the surface. Fluorinating such surfaces reduces the surface free energy by covering the surface hydroxyl groups with fluorine groups, and imparts to the hydrophilic particles 4 or their aggregates 8 surface properties that are practically desirable, i.e., fluidity, dispersibility in solvents, low moisture absorption (water), or water repellency.

[0024] In conventional surface-hydrophobicized metal oxide particles such as hydrophobic silica, the high dispersion of the particles tends to result in non-hydrophobic portions appearing on the surface, and the surface hydrophobicity of the coating film formed by these particles is prone to deterioration over time.In contrast, imparting liquid repellency to the surface by covering it with fluorine groups is less susceptible to such deterioration over time.

[0025] If the fluorine content in the surface layer of the liquid-repellent film 10 is below the lower limit (25 atomic %) of the predetermined range, the desired liquid repellency may not be exhibited. On the other hand, if the fluorine content in the surface layer exceeds the upper limit (50 atomic %) of the predetermined range, no further improvement in liquid repellency can be expected, and instead, polarity may be generated in the surface layer, reducing the liquid repellency.

[0026] It is also preferable that the fluorine content is greater than the oxygen content in the surface layer portion, and that the fluorine content is less than the oxygen content in the range from the surface layer portion to the interior.

[0027] Furthermore, it is preferable that the ratio of the fluorine content to the silicon content in the surface layer is 1 or more. In this case, fluorine will be sufficiently concentrated in the surface layer. The fluorine / silicon content ratio is an indicator of the amount of fluorine atoms present in the surface layer, and if this ratio is less than 1.0, it indicates that there are few fluorine atoms present in the surface layer, and liquid repellency tends to be insufficient.

[0028] It is also possible to form a laminated structure with a liquid-repellent layer equivalent to the liquid-repellent film 10 described above as a top coat layer and the base coat layer described below.

[0029] (base coat layer) The base coat layer contains a thermoplastic resin, such as polyester, polyolefin, chlorinated polyolefin, polystyrene, nylon, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, acrylonitrile butadiene styrene copolymer, ethylene vinyl acetate copolymer, polyacetal, polymethyl methacrylate, methacrylic styrene copolymer, cellulose acetate, polyurethane, or polycarbonate.

[0030] The base coat layer may also contain hydrophilic silica particles (herein referred to as hydrophilic silica beads) and a thermoplastic resin, and may have a relatively large uneven structure due to the hydrophilic silica beads.

[0031] (hydrophilic silica beads) The hydrophilic silica beads have an average particle size on the order of micrometers, for example, and may be appropriately selected from crystalline silica and amorphous silica (dry silica, wet silica, silica gel, etc.). The shape of the hydrophilic silica beads is not particularly limited, and various shapes such as polyhedrons and irregular shapes can be selected. Porous hydrophilic silica beads may also be used. Large-diameter particles may also be included instead of hydrophilic silica beads. For example, hydrophilic oxide fine particles such as titanium oxide, zinc oxide, and aluminum oxide can be used. Acrylic resin beads may also be included as large-diameter particles. The average particle size of these particles is, for example, 1 to 60 μm, preferably 1 to 12 μm.

[0032] (Base coat layer application method) The base coat layer is formed by applying a coating material in which hydrophilic silica beads and a thermoplastic resin are dissolved or dispersed in a solvent to the substrate 2 and then drying the coating material. The solvent is not particularly limited, but examples include hydrocarbons such as n-hexane, cyclohexane, toluene, benzene, and xylene, ketones such as acetone and methyl ethyl ketone, and alcohols.

[0033] When hydrophilic silica beads are contained, the average thickness of the part where hydrophilic silica beads are present and the part where hydrophilic silica beads are not present is taken as the average thickness of the base coat layer, and the average thickness is preferably slightly smaller than the particle diameter of hydrophilic silica beads, about 0.2 to 1.5 μm.If all hydrophilic silica beads are buried in thermoplastic resin, the uneven structure of hydrophilic silica beads is not formed, so the amount of thermoplastic resin applied to hydrophilic silica beads is set so that an appropriate space for air pockets is generated between adjacent hydrophilic silica beads.

[0034] (Anti-adhesion film for O / W emulsion) The resin 6 having the liquid-repellent moiety can be a copolymer of a liquid-repellent moiety and a hydrophilic moiety. In particular, the use of a fluorine-based copolymer resin makes it possible to obtain a liquid-repellent film 10 suitable for preventing the adhesion of oil-in-water (O / W) emulsions such as coffee creamer. Such copolymers include, for example, a block copolymer structure consisting of a polymer containing a liquid-repellent moiety and a polymer containing a hydrophilic moiety. The liquid-repellent moiety is preferably a liquid-repellent moiety made of a fluororesin (e.g., perfluoroalkyl group, polyfluoroalkyl group, perfluoropolyether group). Hydrophilic moieties include hydroxyl group, carboxyl group, amino group, oxyethylene group, and alkoxysilyl group. When such a block copolymer covers hydrophilic silica particles, the copolymer containing the liquid-repellent moiety is surface-oriented in an air atmosphere due to the relationship between the surface free energy. Furthermore, copolymers containing hydrophilic moieties have a high affinity with hydrophilic silica particles 4 having surface hydrophilic properties such as silanol groups, which helps to bond the block copolymer to the hydrophilic silica particles 4.

[0035] Here, among the liquid-repellent portions constituting the copolymer resin of the liquid-repellent portion and the hydrophilic portion that can be used in the liquid-repellent film 10 of this embodiment, an example containing a fluororesin is shown in formula (1).

[0036] [ka]

[0037] Moreover, an example of a hydrophilic moiety constituting the copolymer resin that can be used in the liquid-repellent film 10 of this embodiment is given in formula (2).

[0038] [ka] where R represents hydrogen or an alkyl group, preferably not more than six, and n is an integer.

[0039] An O / W emulsion is a state in which minute oily micelles are dispersed in an aqueous liquid. In this embodiment, when the resin 6 having the liquid-repellent moiety is made of a block copolymer of a polymer containing a liquid-repellent moiety such as fluorine and a polymer containing a hydrophilic moiety, the O / W emulsion exhibits an anti-adhesion effect for the following reasons.

[0040] First, when the agglomerate 8 of the hydrophilic particles 4 is covered with a block polymer resin, the hydrophilic portion of the block polymer resin is oriented toward the agglomerate 8 of the hydrophilic particles 4, and accordingly the liquid-repellent portion is oriented outward.

[0041] When the O / W emulsion comes into contact with the liquid-repellent membrane 10, its hydrophilic parts attract water, which is the continuous phase of the emulsion, making it difficult for the micelles, which are the oil components of the O / W emulsion, to come into contact with the liquid-repellent membrane 10, thereby preventing damage to the micelles.

[0042] Furthermore, the presence of the polymer in the liquid-repellent portion of the liquid-repellent film 10 also prevents the liquid-repellent film 10 from becoming wet with the attracted water. In particular, this adhesion prevention function is maintained even after the O / W emulsion has been in contact with the liquid-repellent film 10 for a long period of time.

[0043] The liquid-repellent film 10 of this embodiment is suitable for use as a packaging film or sheet, and is also suitable for being attached to existing packaging films or sheets. For example, the liquid-repellent film 10 of this embodiment can be used as a packaging material for pouches containing food, cosmetics, detergent, shampoo, conditioner, etc., or as a packaging material for lids on food containers for yogurt, pudding, jelly, etc. The liquid-repellent film 10 of this embodiment can also be used as a packaging material for cakes that use cream, or for foods such as dumplings that are covered in viscous sauces. [Example]

[0044] The present invention will be described in more detail below based on examples, but the present invention is not limited to the contents of these examples.

[0045] <Examples 1-6 and Comparative Examples 1-5> A liquid-repellent film sample was prepared as follows. (1) Base material The substrate used was a 20 μm thick aluminum foil or a 25 μm thick biaxially oriented polypropylene film (OPP), as shown in Table 1. The surface of the OPP to be coated was subjected to corona treatment to improve wettability.

[0046] (2) Base coat layer Using hydrophilic silica beads having the average particle size shown in Table 1 and a chlorinated polyolefin resin as a thermoplastic resin, coating materials were prepared by dissolving and dispersing them in a solvent at the following blending ratio. In Example 1, the base coat layer was formed using only a thermoplastic resin (without hydrophilic silica beads), and the blending ratio was resin:solvent (toluene only)=20:80 (mass %). In Example 2, no base coat layer was formed. The compounding ratio of Example 3-4 was beads: resin: solvent (toluene, MEK) = 3:10:87 (mass %). The compounding ratio of Example 5-6 was beads:resin:solvent (toluene, MEK)=6.2:7.8:86 (mass %). The paint was applied to the substrate in the amount shown in Table 1 and then dried to form a base coat layer. The amount applied is the value of the solid content excluding the solvent.

[0047] (3) Topcoat layer Commercially available hydrophilic fumed silica microparticles with the average primary particle diameter shown in Table 1 were used, and a fluorine-based copolymer resin (resin containing polyfluoroalkyl methacrylate resin) was used as the resin containing the liquid-repellent moiety. These were dissolved and dispersed in solvents (water, 2-propanol) at the following blending ratios to prepare a paint. The compounding ratio of Example 1-4 was silica:resin:solvent=5:5:90 (mass %). The compounding ratio of Example 5-6 was silica:resin:solvent=4.8:3.2:92 (mass %). The coating material was applied to the substrate in the amount shown in Table 1 and then dried to form a topcoat layer.

[0048] Samples of Comparative Examples 1-5 were also prepared as shown in Table 1, and the preparation methods, materials, etc. were the same as those of the Examples. In Comparative Example 1, water was used as the solvent.

[0049] [Table 1]

[0050] (4) Method for measuring the composition ratio of the surface layer of the liquid-repellent film Using an X-ray photoelectron spectroscopy (XPS) analyzer, the composition ratio (content ratio) of fluorine (F), oxygen (O), carbon (C), and silicon (Si) contained in the surface layer of the liquid-repellent film (the area from the surface of the liquid-repellent film to a depth of approximately 5 nm) was measured under the following conditions. XPS equipment: Kratos AXIS NOVA X-ray source: monochromated Al Kα X-ray output emission: 15mA Anode HT:15kV Measurement area: 700μm x 300μm

[0051] (5) Method for measuring the composition ratio of the liquid-repellent film from the surface to the interior Using a scanning electron microscope equipped with an energy dispersive X-ray analyzer (SEM-EDS device), elemental mapping data was measured under the following mapping conditions, and based on this, the composition ratios (content ratios) of fluorine (F), oxygen (O), carbon (C), and silicon (Si) contained in the range from the surface to the interior of the liquid-repellent film (range from the surface of the liquid-repellent film to a depth of approximately 2 to 3 μm) were obtained. SEM-EDS equipment: JEOL JSM-IT100 Accelerating voltage: 10 kV Process time: T2 Dead Time (PC): 75 Magnification: 5000x Resolution: 1024 x 768 (pixels) Number of scans: 10 Characteristic X-rays used in the analysis: Kα rays

[0052] The inventors focused on the fluorine content in the liquid-repellent film, but not on the difference in fluorine content measured by either XPS or SEM-EDS alone, but on the difference in fluorine content measured by both XPS and SEM-EDS. In other words, in a liquid-repellent film having a complex uneven structure made of hydrophilic silica microparticles, when the fluorine content near the uneven surface (for example, up to a depth of about 5 nm from the surface) and the fluorine content in a range from the uneven surface to a relatively deep position (for example, up to a depth of about 2 to 3 μm from the surface) are each appropriate values, the film will exhibit excellent liquid repellency.

[0053] (6) Evaluation method for liquid repellency The liquid repellency of the liquid repellent film was evaluated based on the contact angles of water and two types of oil as follows. Pure water: Place 10 μL of pure water on the liquid-repellent film. Contact Angle Meter DropMaster Series DMs-401 The contact angle was measured using a contact lens tester (manufactured by Kyowa Interface Science Co., Ltd.). Oleic acid: 10 μL of oleic acid was placed on the liquid-repellent film and measured in the same way as for water. Hexadecane: 10 μL of hexadecane was placed on the liquid-repellent film and measured in the same manner as for water.

[0054] A sample with a contact angle of 150° or more with pure water and a contact angle of 130° or more with oleic acid was evaluated as "exhibiting excellent liquid repellency" and given a grade of "A." Among these, a sample with a contact angle of 120° or more with hexadecane was evaluated as "exhibiting even better liquid repellency" and given a grade of "AA." A sample with a contact angle of less than 150° with pure water or less than 130° with oleic acid was given a grade of "B."

[0055] The results of the XPS measurement are shown in Table 2, and the results of the SEM-EDS measurement are shown in Table 3. The content of each component is expressed in atomic percent (atomic %). The evaluation results of the liquid repellency are shown in Table 4.

[0056] [Table 2]

[0057] [Table 3]

[0058] [Table 4]

[0059] As shown in the results of Tables 2 to 4, the fluorine content of the surface layer of the samples of Examples 1 to 6 was in the range of 25 atomic % or more and 50 atomic % or less. The fluorine content in the area from the surface layer to the interior was 5 atomic % or less. All of the samples of Examples 1 to 6 exhibited liquid repellency of "A" or higher. In particular, the samples of Examples 3 to 6, in which a relatively large uneven structure formed by hydrophilic silica beads was formed in the base coat layer, were evaluated as "AA," the best in terms of liquid repellency.

[0060] The samples in Examples 1 to 6 differ in that they have a base coat or not, and the combination of base coat components is different, but they have one thing in common: a top coat layer of hydrophilic silica microparticle aggregates is distributed on the surface of the base coat or substrate, and the resulting uneven surface is covered with a fluorine-based copolymer resin.

[0061] The fluorine content measured by XPS in Table 2 indicates the distribution of fluorine on the uneven surface of the top coat layer (at a depth of approximately 5 nm), and indicates that fluorine-based copolymer resin is concentrated in this range, with little hydrophilic silica microparticles distributed. Furthermore, the fluorine content measured by SEM-EDS in Table 3 indicates that the proportion of fluorine in the entire top coat layer is lower than the proportion of fluorine on the surface. When these values ​​are within the above ranges, a film with excellent liquid repellency can be formed.

[0062] In contrast, in the sample of Comparative Example 1, the top coat layer (without the base coat layer) was formed only from a fluorine-based copolymer resin, so there was no uneven structure due to hydrophilic silica fine particles, and the fluorine content was excessive (more than 50 atomic %) in the XPS measurement (surface layer portion) in Table 2. Furthermore, the sample of Comparative Example 1 also had a high fluorine content (more than 5 atomic %) in the SEM-EDS measurement (entire top coat layer) in Table 3. In addition, in the sample of Comparative Example 2, the proportion of hydrophilic silica particles contained in the top coat layer was small (12 mass%), so the fluorine-based copolymer resin covering the surface was larger in volume than the uneven structure caused by the hydrophilic silica particles.As a result, while the fluorine content in the surface layer in Table 2 was 50 atomic % or less, the fluorine content in the entire top coat layer (from the surface layer to the interior) in Table 3 was large (5 atomic % or more). Therefore, as shown in Table 4, the samples of Comparative Examples 1 and 2 have small contact angles with water and oil, and are rated low in liquid repellency ("B").

[0063] In addition, the samples of Comparative Examples 3-5 have topcoat layers formed using hydrophilic silica microparticles with various average primary particle sizes. These samples contain a certain proportion of hydrophilic silica microparticles, and the uneven structure is formed by the aggregation of hydrophilic silica microparticles. For the samples of Comparative Examples 3-5, the fluorine content measured by SEM-EDS (overall topcoat layer) in Table 3 is within the specified range (5 atomic % or less; in Comparative Example 5, the fluorine content did not reach the detection limit). However, the fluorine content measured by XPS (surface layer) in Table 2 is low (25 atomic % or less). This is thought to be due to the lack of fluorine-based copolymer resin covering the surface of the uneven structure formed by the aggregation of hydrophilic silica microparticles in these samples, resulting in the distribution of hydrophilic silica microparticles up to the surface of the uneven structure. These structures lack fluorine distributed on the surface of the uneven structure, resulting in insufficient liquid repellency ("B"), as shown in Table 4.

[0064] As shown in Table 2, the ratio of the fluorine (F) content to silicon (Si) content in the surface layer portion is 1 or more in the samples of Examples 1-6 and Comparative Examples 1-3, and in particular, the ratio in the sample of Example 1-6 is between 3 and 4. A ratio of the F content to Si content in the surface layer portion of 1 or more can be a requirement for achieving excellent liquid repellency.

[0065] Furthermore, when the contents of fluorine (F) and oxygen (O) in the surface layer portion are compared in Table 2, the samples of Examples 1-6 and Comparative Examples 1-2 all have a higher content of fluorine F than oxygen O. A higher content of fluorine F than oxygen O in the surface layer portion can be a requirement for achieving excellent liquid repellency.

[0066] Furthermore, as shown in Table 3, the fluorine (F) content in the entire top coat layer was smaller than the oxygen (O) content in all of the samples of Examples 1-6 and Comparative Examples 2-5. A smaller fluorine (F) content than oxygen (O) content in the entire top coat layer can be a requirement for exhibiting excellent liquid repellency.

[0067] The energy distribution diagrams of the SEM-EDS measurements are shown in Figures 2 to 4, along with 5000x SEM images. The scale bar in the SEM images is 5 μm. In the energy distribution diagrams of the SEM-EDS measurements, in addition to peaks for the C, O, F, and Si components, a chlorine (Cl) peak was also detected. This is thought to be the Cl component of the chlorinated polyolefin resin used as the thermoplastic resin in the base coat layer.

[0068] The relatively large spheres in the SEM images of Figures 2 to 4 are hydrophilic silica beads. As the SEM images of the liquid-repellent film show, it is difficult to distinguish between structures that exhibit excellent liquid repellency and those that do not based solely on the external structural characteristics of the liquid-repellent film. Therefore, as in the present invention, there is a significant advantage in that it is possible to determine whether a structure exhibits excellent liquid repellency by focusing on the fluorine content in the liquid-repellent film and determining whether the fluorine content measured by both the XPS and SEM-EDS methods falls within a predetermined numerical range.

[0069] Under the same conditions as in Example 1 (base coat layer not containing hydrophilic silica beads: 0.64 g / m 2 , Top coat layer: 0.71 g / m 2 ) was used to measure the composition ratio of fluorine (F), oxygen (O), potassium (K), carbon (C), chlorine (Cl), and silicon (Si) contained in the liquid-repellent film under the following conditions using an X-ray photoelectron spectroscopy analyzer (XPS analyzer) different from the above. XPS equipment: ULVAC PHI QUANTERA SXM X-ray source: Monochromated Al Kα radiation X-ray output: 25W X-ray beam diameter: 100 μm Photoelectron take-off angle: 45° Argon ions (Ar + ) Sputtering rate: Approximately 15 nm / min (SiO2 equivalent) Sputter depth 1st time: 0 nm 2nd time: 7.5 nm 3rd time: 15nm The results are shown in Figure 5. The composition ratio of K and Cl is very small. By converting the measurement results at the sputtering depth (0 nm) into values ​​for only four components (F, O, C, Si), F: 34.1 atomic %, O: 31.1 atomic%, C: 23.0 atomic%, Si:11.8 atomic% As a result, it can be seen that the F content is 25 atomic % or more and 50 atomic % or less based on the total number of F, O, C, and Si atoms in the surface layer of the liquid-repellent film. [Explanation of symbols]

[0070] 2 Base material 4 Hydrophilic particles 6. Resin with liquid-repellent properties 8 aggregates 10 Liquid repellent film

Claims

1. A liquid-repellent film comprising hydrophilic fumed silica fine particles and a fluorine-based copolymer resin containing a liquid-repellent moiety and a hydrophilic moiety, wherein the hydrophilic fumed silica fine particles form an uneven structure, and the fluorine-based copolymer resin covers at least the surface of the uneven structure, (a) the liquid-repellent film contains carbon, fluorine, oxygen, and silicon in a region from the surface to a depth of 5 nm, and the fluorine content is 25 atomic % or more and 50 atomic % or less based on the total number of carbon, fluorine, oxygen, and silicon atoms in the region from the surface to a depth of 5 nm as measured by X-ray photoelectron spectroscopy; (b) the liquid-repellent film contains carbon, fluorine, oxygen, and silicon in a region from the surface to a depth of 2 to 3 μm, and the fluorine content is 5 atomic % or less based on the total number of carbon, fluorine, oxygen, and silicon atoms in the region from the surface to a depth of 2 to 3 μm as measured based on elemental mapping data obtained by SEM-EDS; (c) A liquid-repellent film, characterized in that the ratio of the fluorine content to the silicon content is within a range of 3 to 4 in a range from the surface of the liquid-repellent film to a depth of 5 nm.

2. The liquid-repellent film according to claim 1, characterized in that the fluorine content is greater than the oxygen content in a range from the surface of the liquid-repellent film to a depth of 5 nm, and the fluorine content is less than the oxygen content in a range from the surface of the liquid-repellent film to a depth of 2 to 3 μm.

3. A packaging material comprising a substrate and the liquid-repellent film according to claim 1 or 2 formed on the substrate.

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