Base material film for forming inorganic thin film layer, and multilayer film

Abstract

Provided is a base material film for forming an inorganic thin film layer, wherein: a surface treatment is performed on at least one surface of a base material film that contains a polypropylene-based resin as a main component; with respect to contact angle with water of the base material film, the ratio (C1 / C2) of the contact angle (C1) with water of an untreated surface to the contact angle (C2) with water of a treated surface is 1.4 or more; and the ten-point average roughness (Rzjis) of the surface of the base material film is 15 nm or less.

Description

Substrate films for forming inorganic thin layers and laminated films

[0001] The present invention relates to a substrate film for forming an inorganic thin film layer, which is used in the packaging fields of foods, pharmaceuticals, industrial products, etc., and a laminate film obtained by laminating an inorganic thin film layer on the substrate film. More specifically, the present invention relates to a substrate film that can exhibit excellent gas barrier properties at low cost when made into a gas barrier laminate film having an inorganic thin film layer using easily recyclable materials or heat-resistant materials.

[0002] In recent years, regulations aimed at reducing the use of disposable plastics have been strengthened in Europe and other countries around the world. Behind this trend is growing international awareness of resource recycling and the worsening waste problems in emerging countries. As a result, there is a demand for environmentally friendly products that comply with the 3Rs (recycle, reuse, reduce) for plastic packaging materials for food, pharmaceuticals, etc.

[0003] The performance requirements for the aforementioned environmentally friendly packaging materials include (1) being made from materials that are easy to recycle, (2) having gas barrier properties that can block various gases and extend the shelf life, and (3) having a laminate structure that places a low burden on the environment (for example, using a small amount of material itself, or being recyclable by converting it into a monomaterial).

[0004] In recent years, the use of polypropylene film has been attracting attention in order to achieve the above (1) and (3). Polypropylene film is widely used in a wide range of applications, including packaging for food and various other products, electrical insulation, and surface protection films. Due to its molecular structure, polypropylene film is capable of exhibiting high water vapor barrier properties. Furthermore, since polypropylene- or polyethylene-based heat seal resins are generally used as sealants to be bonded to the surface substrate film, for example, by using a polypropylene film as the surface substrate and an unstretched polypropylene sheet as the sealant, a mono-material packaging material can be achieved as a whole while maintaining gas barrier properties, enabling the design of environmentally friendly packaging materials that are easy to recycle, etc.

[0005] However, with regard to the gas barrier property of (2) above, although polypropylene films have water vapor barrier properties, the water vapor barrier properties of these films are not sufficient compared to, for example, transparent inorganic vapor-deposited polyester films, which are generally considered to have excellent water vapor barrier properties, and there is also the problem that the oxygen barrier properties of these films are very poor.

[0006] In contrast to this, gas barrier laminates are generally used in which a thin metal film made of aluminum or the like or an inorganic thin film made of an inorganic oxide such as silicon oxide or aluminum oxide is formed on the surface of a plastic substrate film such as a polyester film. Among these, those in which a thin film of an inorganic oxide such as silicon oxide, aluminum oxide, or a mixture thereof is formed are widely used because they do not require the use of aluminum foil, are transparent so that the contents can be confirmed, and furthermore, the formed film is very thin and does not hinder recyclability.

[0007] A method has also been disclosed for imparting gas barrier properties to polypropylene films by laminating an inorganic thin film (e.g., Patent Document 1). However, the surface of the polypropylene film is highly uneven due to its molecular structure, and there are many cracks in the inorganic thin film layer, which makes it difficult to achieve sufficient gas barrier properties.

[0008] To address these problems, a method has been disclosed in which a polyvinyl alcohol polymer resin composition is used between a polypropylene film and an inorganic thin film layer to smooth the surface on which the inorganic thin film layer is formed, thereby imparting gas barrier properties (e.g., Patent Document 2). However, when a polyvinyl alcohol polymer resin composition is used, a concentration of at least 0.5 g / m is required to achieve sufficient gas barrier performance. ２ It was necessary to laminate a mass of more than this amount. Increasing the amount of adhesion could result in impurities during recycling, making recycling itself difficult. It was also not suitable from the perspective of mono-materialization using a single material. Furthermore, there was the problem that the manufacturing costs would increase due to the increase in the number of lamination steps and the increase in the amount of adhesion of the alcohol polymer resin composition.

[0009] Japanese Patent Publication No. 53-12953 Japanese Patent Application Laid-Open No. 2021-20392

[0010] The gas barrier performance of Patent Document 1 was insufficient. Patent Document 2 required a thick film thickness to exhibit gas barrier performance, and did not consider improving processability by thinning the coating layer or environmental and manufacturing costs. In other words, there has not been a material that satisfies all three of the performance requirements for the environmentally friendly packaging material: (1) containing a recyclable material as a constituent material, (2) having gas barrier performance that can block various gases and extend the shelf life, and (3) having a laminate structure that is easy to recycle and has a low environmental impact (mono-material).

[0011] The present invention was made in light of the problems of the conventional technology, and aims to provide a laminate film that can be formed into a laminate structure composed of almost a single resin type, mainly a polypropylene film, which has a low environmental impact, and that, when made into a gas barrier laminate film with an inorganic thin film layer, has excellent gas barrier properties, is easy to produce, and is economical.

[0012] The present inventors discovered that by treating the surface of a plastic substrate film on which an inorganic thin film layer is to be formed, the film surface can be made hydrophilic, allowing the inorganic thin film layer to be deposited uniformly and densely, and also making the substrate film surface extremely smooth, thereby enabling the formation of an inorganic thin film layer that is less susceptible to cracking, thereby further improving the gas barrier properties and completing the present invention.

[0013] That is, the present invention comprises the following: 1. A substrate film for forming an inorganic thin film, characterized in that at least one surface of a substrate film mainly composed of a polypropylene resin is surface-treated, the ratio (C1 / C2) of the water contact angle of the substrate film between the water contact angle of the untreated surface (C1) and the water contact angle of the treated surface (C2) satisfies the relationship of 1.4 or more, and the ten-point average roughness (Rzjis) of the substrate film surface is 15 nm or less. 2. A laminate film, characterized in that an inorganic thin film layer is laminated on the treated surface of the substrate film described in 1. 3. The laminate film described in 2., characterized in that the inorganic thin film layer contains at least one selected from the group consisting of silicon oxide, aluminum oxide, and magnesium oxide. 4. An oxygen permeability of 1,300 ml / m2 or more in an environment of 23°C x 65% RH ２ 2. The laminated film according to 2., characterized in that the compressive strength is d MPa or less.

[0014] The present invention provides a film that can be formed into a laminate structure composed of almost a single resin type, mainly a polypropylene film, which has a low environmental impact, and when formed into a gas barrier laminate film with an inorganic thin film layer, it is possible to provide a laminate film that has excellent gas barrier properties, is easy to produce, and is economical.

[0015] The present invention provides a substrate film for forming an inorganic thin film layer, characterized in that at least one surface of the substrate film, primarily composed of a polypropylene resin, is surface-treated, the ratio (C1 / C2) of the water contact angle of the substrate film between the untreated surface (C1) and the treated surface (C2) satisfies a relationship of 1.4 or greater, and the ten-point average roughness (Rzjis) of the substrate film surface is 15 nm or less. The present invention also provides a laminate film in which an inorganic thin film layer is laminated on the treated surface of the substrate film. The laminate film may also include a protective layer, a printed layer, etc. in addition to the inorganic thin film layer.

[0016] Each layer of the laminate film will be described below. [Base Film] The base film used in the present invention is preferably a biaxially oriented film. Known biaxially oriented polypropylene resin films can be used as the biaxially oriented film, and the raw materials, blending ratios, and the like are not particularly limited. For example, the biaxially oriented film may be a polypropylene homopolymer (propylene homopolymer), or a random copolymer or block copolymer containing propylene as the main component with one or more α-olefins selected from ethylene, butene, pentene, hexene, and the like, or a mixture of two or more of these polymers. Furthermore, known additives such as antioxidants, antistatic agents, and plasticizers may be added to modify the physical properties. For example, petroleum resins and terpene resins may be added.

[0017] The substrate film may be a single-layer film or a laminated film in which multiple resin films are laminated. When a laminated film is used, the type of laminate, the number of layers, and the lamination method are not particularly limited and can be selected from known methods depending on the purpose. However, the substrate film is preferably a laminated film composed of three layers, such as a surface layer (B), a substrate layer (A), and a surface layer (C). This three-layer structure allows the film to achieve both smoothness and barrier properties. The substrate film, primarily composed of a polypropylene resin, has poor smoothness due to its excellent flexibility, which can lead to blocking, or adhesion between films. Therefore, an antiblocking agent is generally added to form surface irregularities. This surface irregularity can result in insufficient thin film formation by vapor deposition or coating, leading to problems such as poor barrier properties. In other words, it is preferable to minimize the amount of antiblocking agent added to the surface layer (B), which is vapor-deposited, and to add a large amount of antiblocking agent to the surface layer (C). When an antiblocking agent is added to the base layer (A), the antiblocking agent may appear on the surface of the surface layer (B) over time, causing cracks in the vapor deposition formed, and preventing sufficient barrier properties from being exhibited.

[0018] Antiblocking agents can be appropriately selected from inorganic particles such as silica, calcium carbonate, kaolin, and zeolite, and organic particles such as acrylic, polymethacrylic, and polystyrene particles. Among these, silica and polymethacrylic particles are particularly preferred. The average particle size of the antiblocking agent is preferably 1.0 to 3.0 μm, more preferably 1.0 to 2.7 μm. The average particle size is measured by taking a photograph with a scanning electron microscope, measuring the horizontal Feret's diameter using an image analyzer, and expressing the average value. There are no particular restrictions on the amount of antiblocking agent added, as long as the amount added to the surface layer (B) and the surface layer (C) is adjusted so that the haze, dynamic friction coefficient, center surface average roughness (SRa), and air release time are within the specified ranges. However, the antiblocking agent may appear on the surface of the surface layer (B) or fall off, causing cracks in the vapor deposition formed, which may result in insufficient barrier properties. Therefore, it is desirable to add the minimum amount of anti-blocking agent that keeps the haze, dynamic friction coefficient, center surface average roughness (SRa), and air release time within the specified ranges.

[0019] The base film contains a polypropylene-based resin as a main component. In this specification, "containing a polypropylene-based resin as a main component" means that the base film contains 90% by mass or more of the polypropylene-based resin when the entire base film is taken as 100% by mass. The content of the polypropylene-based resin is preferably 95% by mass or more, more preferably 98% by mass or more, when the entire base film is taken as 100% by mass.

[0020] In the present invention, the polypropylene-based resin constituting the base film is preferably a propylene homopolymer that does not substantially contain a comonomer, and even if a comonomer is contained, the comonomer amount is preferably 0.5 mol% or less. The upper limit of the comonomer amount is more preferably 0.3 mol%, and even more preferably 0.1 mol%. Within this range, crystallinity is improved, the heat shrinkage rate at high temperatures is reduced, and heat resistance is improved. Note that a trace amount of comonomer may be contained within a range that does not significantly reduce crystallinity.

[0021] The polypropylene-based resin constituting the base film preferably contains a propylene homopolymer obtained only from propylene monomers, and even if it is a propylene homopolymer, it is most preferable that it does not contain heterogeneous bonds such as head-to-head bonds.

[0022] From a practical standpoint, the lower limit of the xylene-soluble content of the polypropylene resin constituting the base film is preferably 0.1% by mass. The upper limit of the xylene-soluble content is preferably 7% by mass, more preferably 6% by mass, and even more preferably 5% by mass. Within this range, crystallinity is improved, the thermal shrinkage at high temperatures is further reduced, and heat resistance is improved.

[0023] In the present invention, the lower limit of the melt flow rate (MFR) (230°C, 2.16 kgf) of the polypropylene resin is preferably 0.5 g / 10 min. The lower limit of the MFR is more preferably 1.0 g / 10 min, even more preferably 2.0 g / 10 min, particularly preferably 4.0 g / 10 min, and most preferably 6.0 g / 10 min. Within the above range, the mechanical load is small, and extrusion and stretching are easy. The upper limit of the MFR is preferably 20 g / 10 min. The upper limit of the MFR is more preferably 17 g / 10 min, even more preferably 16 g / 10 min, and particularly preferably 15 g / 10 min. Within the above range, stretching is easy, thickness unevenness is reduced, the stretching temperature and heat setting temperature can be easily increased, the heat shrinkage rate is smaller, and heat resistance is improved.

[0024] From the viewpoint of heat resistance, the substrate film may be a uniaxially stretched film in the longitudinal direction (MD direction) or the transverse direction (TD direction), but is preferably a biaxially stretched film. In the present invention, by stretching at least uniaxially, a film having a low thermal shrinkage rate at high temperatures and high heat resistance, which was not expected with conventional polypropylene films, can be obtained. Examples of stretching methods include simultaneous biaxial stretching and sequential biaxial stretching, but sequential biaxial stretching is preferred from the viewpoint of improving flatness, dimensional stability, thickness unevenness, etc.

[0025] In the sequential biaxial stretching method, a polypropylene resin is heated and melted in a single-screw or twin-screw extruder to a resin temperature of 200°C to 280°C, formed into a sheet through a T-die, and extruded onto a chill roll at a temperature of 10°C to 100°C to obtain an unstretched sheet. The sheet is then stretched in the machine direction (MD) at a ratio of 3.0 to 8.0 times at a temperature of 120°C to 165°C, and subsequently, after preheating in a tenter, stretched in the transverse direction (TD) at a ratio of 4.0 to 20.0 times at a temperature of 155°C to 175°C. Furthermore, after biaxial stretching, the sheet can be heat-set at a temperature of 165°C to 175°C while allowing a relaxation of 1% to 15%.

[0026] In order to improve handling properties (e.g., winding properties after lamination), the substrate film used in the present invention preferably contains particles to form protrusions on the film surface. Examples of particles to be contained in the film include inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, and alumina, and heat-resistant polymer particles such as acrylic, PMMA, nylon, polystyrene, polyester, and benzoguanamine-formalin condensate. From the viewpoint of transparency, the particle content in the film is preferably low, for example, from 1 ppm to 1000 ppm. The average particle diameter of the particles is preferably 1.0 to 3.0 μm, more preferably 1.0 to 2.7 μm. The average particle diameter here is measured by taking a photograph with a scanning electron microscope, measuring the Feret's diameter in the horizontal direction using an image analyzer, and expressing it as the average value. Furthermore, from the viewpoint of transparency, it is preferable to select particles with a refractive index close to that of the resin used. In addition, the film may contain antioxidants, ultraviolet absorbers, antistatic agents, dyes, lubricants, nucleating agents, adhesives, antifogging agents, flame retardants, antiblocking agents, inorganic or organic fillers, etc., to impart various functions to the film as needed.

[0027] In the present invention, the thickness of the substrate film is set arbitrarily according to each application, but the lower limit is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 4 μm or more. On the other hand, the upper limit of the thickness is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and particularly preferably 100 μm or less. If the thickness is too thin, handling tends to be poor. On the other hand, if the thickness is too thick, not only is there a problem in terms of cost, but also poor flatness tends to occur due to curling when wound into a roll and stored.

[0028] The haze of the base film of the present invention is preferably transparent from the viewpoint of visibility of contents, and specifically is preferably 6% or less, more preferably 5% or less, and even more preferably 4% or less. Haze tends to deteriorate, for example, when the stretching temperature or heat setting temperature is too high, when the cooling roll (CR) temperature is high and the cooling rate of the stretched raw sheet is slow, or when the low molecular weight content is too high. Therefore, by adjusting these, it can be controlled within the above range.

[0029] The substrate film of the present invention may be subjected to corona discharge treatment, glow discharge treatment, or flame treatment as long as the treatment does not impair the object of the present invention, but the plasma treatment described below is preferred in order to make the surface of the substrate film hydrophilic and smooth. Furthermore, the substrate film may be subjected to known anchor coating treatment, printing, decoration, etc.

[0030] The apparatus used for surface treatment of the substrate film in the present invention may be a normal pressure plasma modification apparatus, an atmospheric pressure plasma surface modification apparatus, or a vacuum plasma surface treatment apparatus. The type of plasma can be selected from arc discharge, corona discharge, dielectric barrier discharge, microwave discharge, and the like. This plasma treatment can simultaneously achieve two effects: a chemical effect, such as introducing functional groups onto the surface of the substrate film using the generated radicals and ions, and a physical effect, such as ion etching the surface to remove impurities adhering to the substrate film surface or melting the surface with the treatment heat to smooth the surface. This surface treatment allows the formation of a dense thin film of inorganic oxide during subsequent vapor deposition processing. As a result, the adhesion between the substrate film and the inorganic thin film layer can be strengthened, leading to improved gas barrier properties and prevention of cracking.

[0031] The plasma irradiation method can be selected from known methods such as direct, remote, and spot types. However, to satisfy the claims of the present invention, it is desirable to select the direct or remote type. The direct and remote types allow for high-speed, wide-width processing of substrate films and are economically advantageous. The spot type has a narrow processing width and is therefore economically disadvantageous for producing substrate films for forming inorganic thin film layers. Furthermore, because high-density plasma is irradiated locally, the degree of processing is high, but surface irregularities are likely to occur, and the surface smoothness of the substrate film is lost, resulting in a problem that when an inorganic thin film layer is formed, the inorganic thin film layer is prone to cracking.

[0032] Gas species used for plasma treatment include air, oxygen gas, nitrogen gas, helium gas, argon gas, or a mixture thereof. To hydrophilize the substrate film surface and improve the gas barrier properties of the formed inorganic thin film layer, oxygen gas and nitrogen gas are preferably contained. By introducing oxygen gas or the like, the generated oxygen plasma breaks carbon-carbon bonds on the substrate film surface, and the introduction of oxygen or the like forms functional groups such as hydroxyl groups, carbonyl groups, ester groups, and amino groups, thereby improving the hydrophilicity of the film surface. The lower limit of the oxygen and nitrogen gas mixture amount is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. On the other hand, the upper limit of the gas mixture amount is not particularly limited as long as it is within a range that allows stable plasma discharge. If the gas mixture amount is too small, the substrate film surface will not be sufficiently hydrophilized, resulting in the problem of not achieving satisfactory gas barrier properties when an inorganic thin film layer is formed.

[0033] The atmospheric pressure during plasma treatment is set arbitrarily to suit each application and existing equipment, but the upper limit is preferably atmospheric pressure or below. There is no particular limit on the lower limit of the atmospheric pressure as it depends on the equipment performance, but the lower the pressure, the better. Atmospheric pressure plasma is a treatment performed at atmospheric pressure, so impurities are mixed into the air, and the degree of treatment of the substrate film is reduced. However, atmospheric pressure plasma equipment has an aspect of being relatively economical. On the other hand, vacuum plasma, which can lower the atmospheric pressure, has less air containing impurities, so the degree of treatment of the substrate film is higher. However, due to the cost of equipment maintenance, it is less economical.

[0034] In the present invention, the lower limit of the watt density of the plasma treatment is 7000 W·min / m 2 More preferably, 8000 W・min / m 2 More preferably, 8500 W·min / m 2 On the other hand, the upper limit of watt density is 17000W・min / m 2 The preferred range is 17,000 W·min / m or less. 2 or less, more preferably 16000 W·min / m 2The reasons are as follows: If the watt density of the plasma treatment is low, the hydrophilization of the substrate film surface is insufficient, and satisfactory gas barrier properties cannot be obtained when an inorganic thin film layer is formed. If the watt density is high, the substrate film surface becomes rough due to partial strong melting caused by the treatment heat.

[0035] In the present invention, the length of the discharge electrode is set arbitrarily so as to obtain the desired watt density, but the lower limit is preferably 0.2 m or more. More preferably, it is 0.25 m or more, and even more preferably, it is 0.3 m or more. On the other hand, the upper limit of the discharge electrode length is preferably 10 m or less. More preferably, it is 9.5 m or less, and even more preferably, it is 9 m or less. If the discharge electrode length is short, the watt density during treatment increases and a high plasma treatment effect can be obtained, but there is a problem that the width of the film that can be treated is small, resulting in poor productivity. If the discharge electrode length is long, a longer width of film can be treated at one time, which is advantageous in terms of production, but there is a problem that a sufficient treatment effect cannot be obtained.

[0036] In the present invention, the film running speed is also set arbitrarily so as to obtain the target watt density, but the lower limit is preferably 0.1 m / min or more, more preferably 0.2 m / min or more, and even more preferably 0.3 m / min or more. On the other hand, the lower limit is preferably 400 m / min or less, more preferably 350 m / min or less, and even more preferably 300 m / min or less. A slow film running speed can result in poor productivity. A fast film running speed is advantageous in terms of productivity, but can result in insufficient treatment effectiveness. Furthermore, the discharge power can be set arbitrarily depending on the target watt density and device characteristics.

[0037] [Inorganic Thin Film Layer] The inorganic thin film layer is a thin film made of a metal or an inorganic oxide. There are no particular limitations on the material forming the inorganic thin film layer as long as it can be formed into a thin film. However, from the viewpoint of gas barrier properties, inorganic oxides such as aluminum, silicon oxide (silica), aluminum oxide (alumina), and a mixture of silicon oxide and aluminum oxide are preferred. In this composite oxide, the mixing ratio of silicon oxide to aluminum oxide is preferably in the range of 20 to 70% by mass of Al in terms of the mass ratio of the metal components. If the Al concentration is less than 20% by mass, the water vapor barrier properties may be reduced. On the other hand, if the Al concentration exceeds 70% by mass, the inorganic thin film layer tends to become hard, which may result in destruction of the film during secondary processing such as printing or lamination, resulting in reduced gas barrier properties. Furthermore, when the Al concentration is 100% by mass, the water vapor barrier performance is good, but the surface tends to be smooth due to the single material, and the surface tends to have poor slipperiness, making it prone to processing defects (wrinkles, acne, etc.). Note that silicon oxide here refers to SiO or SiO ２ and various silicon oxides such as AlO and Al ２ O ３ and the like, or mixtures thereof.

[0038] The thickness of the inorganic thin film layer is usually 1 to 100 nm, preferably 5 to 50 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties. On the other hand, even if the thickness is excessively greater than 100 nm, the corresponding improvement in gas barrier properties cannot be obtained and is actually disadvantageous in terms of flex resistance and production costs.

[0039] The method for forming the inorganic thin film layer is not particularly limited, and any known vapor deposition method may be appropriately employed, such as physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD). A typical method for forming the inorganic thin film layer will be described below, taking silicon oxide / aluminum oxide-based thin films as an example. For example, when using vacuum deposition, silicon oxide, aluminum oxide, aluminum, a mixture of silicon oxide and aluminum oxide, or a mixture of silicon oxide and aluminum is preferably used as the vapor deposition raw material. These vapor deposition raw materials are typically particles, and the particle size is preferably such that the pressure during vapor deposition does not change, with a preferred particle diameter being 1 mm to 5 mm. Heating methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be employed. Furthermore, reactive vapor deposition using reactive gases such as oxygen, nitrogen, hydrogen, argon, carbon dioxide, and water vapor, or ozone addition or ion-assisted deposition can also be employed. Furthermore, the film formation conditions can be changed as desired by applying a bias to the deposition target (the laminated film to be deposited), heating or cooling the deposition target, etc. The deposition material, reactive gas, bias, heating / cooling, etc. of the deposition target can be changed in the same way when the sputtering method or the CVD method is adopted.

[0040] [Protective Layer] In the present invention, a protective layer can be provided on the inorganic thin film layer when additional gas barrier performance or processing such as printing is required. The inorganic thin film layer is not a completely dense film, but has minute defects scattered therein. By forming a protective layer by coating the inorganic thin film layer with a specific resin composition for the protective layer described below, the resin in the resin composition for the protective layer penetrates into the defects in the inorganic thin film layer, resulting in stable gas barrier properties. In addition, using a material with gas barrier properties for the protective layer itself greatly improves the gas barrier performance of the laminate film. However, attention should be paid to the increased cost due to the additional process steps involved when providing a protective layer. It should also be noted that the protective layer can change physical properties such as surface roughness.

[0041] The amount of the protective layer applied is 0.10 to 0.50 g / m ２ This allows the protective layer to be uniformly controlled during coating, resulting in a film with fewer coating irregularities and defects. In addition, the cohesive force of the protective layer itself is improved, and the adhesion between the inorganic thin film layer and the protective layer is also strengthened. The protective layer deposition amount is 0.50 g / m ２ If the thickness of the protective layer exceeds 0.10 g / m, the gas barrier property is improved, but the cohesive force inside the protective layer becomes insufficient and the uniformity of the protective layer is also reduced, which may result in unevenness or defects in the coat appearance, or in the inability to fully exhibit gas barrier property and adhesiveness, which is also disadvantageous in terms of cost. ２ If it is less than this, sufficient gas barrier properties may not be obtained.

[0042] Examples of resin compositions used for the protective layer formed on the surface of the inorganic thin film layer of the laminate film of the present invention include those containing vinyl alcohol-based, urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, polybutadiene-based, or other resins to which an epoxy-based, isocyanate-based, melamine-based, or other curing agent has been added.

[0043] The method for applying the resin composition for the protective layer is not particularly limited as long as it is a method that can apply the resin composition for the protective layer to the surface of a film to form a layer. For example, a conventional coating method such as gravure coating, reverse roll coating, wire bar coating, or die coating can be used.

[0044] [Printed Layer] Furthermore, the laminate film of the present invention may have at least one printed layer or other plastic substrate and / or paper substrate laminated between the substrate film and the protective layer or on the outer surface thereof.

[0045] As the printing ink for forming the printing layer, aqueous and solvent-based resin-containing printing inks are preferably used. Examples of resins used in printing inks include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may contain known additives such as antistatic agents, light-blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoamers, crosslinking agents, anti-blocking agents, and antioxidants. The printing method for forming the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. To dry the solvent after printing, known drying methods such as hot air drying, heat roll drying, and infrared drying can be used.

[0046] The substrate film of the present invention exhibits the following film properties, which are measured and evaluated by the methods described later in the examples.

[0047] In the substrate film subjected to the plasma treatment of the present invention, the ratio (C1 / C2) of the water contact angle of the untreated surface (C1) to the water contact angle of the treated surface (C2) measured 1 second after the drop of water is preferably 1.4 or more. More preferably, it is 1.45 or more. Meanwhile, the upper limit of the ratio of the water contact angles before and after the plasma treatment is preferably 2.3 or less. More preferably, it is 2.2 or less. The ratio of the water contact angles before and after the plasma treatment serves as an index of the degree of polarity of the substrate film subjected to the plasma treatment. It is expected that the polar groups present on the surface of the substrate film subjected to the plasma treatment of the present invention are localized. In other words, to measure the degree of polarity of the substrate film, an evaluation method capable of measuring the degree of polarity over an area of ​​several square millimeters, such as contact angle measurement, is preferable to microscopic evaluation. Furthermore, since measurements taken immediately after dropping water onto the substrate film may not provide stable values, it is preferable to measure the contact angle 1 second after the drop of water. When the contact angle ratio is within the above range, the substrate film surface becomes highly polarized, and when an inorganic thin film layer is laminated, the adhesion between the substrate film surface and the inorganic thin film layer is enhanced, resulting in maximum gas barrier performance. If the ratio of the water contact angles before and after plasma treatment is less than 1.4, the amount of polar groups on the plasma-treated substrate film surface is low, the inorganic thin film layer is formed sparsely, and sufficient gas barrier properties may not be obtained. On the other hand, if the ratio of the water contact angles before and after plasma treatment is 2.3 or more, the plasma treatment is so strong that the surface becomes uneven, making it difficult for inorganic deposition to accumulate on the substrate film surface, resulting in many cracks and defects in the formed inorganic thin film layer.

[0048] In the plasma-treated substrate film of the present invention, the ten-point mean roughness (Rzjis) of the plasma-treated surface measured using a scanning probe microscope is preferably 15 nm or less, more preferably 14 nm or less. The lower limit of Rzjis is not particularly limited because it depends on the Rzjis of the substrate film used, but the lower the Rzjis value, the better. The ten-point mean roughness of the plasma-treated surface serves as an indicator of the likelihood of cracks and defects occurring in the inorganic thin film layer to be formed. By ensuring that the ten-point mean roughness value is within the above range, an inorganic thin film layer that is less susceptible to cracks and defects can be formed, thereby maximizing gas barrier performance. If the ten-point mean roughness is greater than 15 nm, it becomes difficult for inorganic deposition material to deposit on the substrate film surface, resulting in increased cracks and defects in the inorganic thin film layer formed.

[0049] The total thickness of the laminated film of the present invention is preferably 9 μm or more and 200 μm or less, more preferably 10 μm or more and 150 μm or less, even more preferably 12 μm or more and 100 μm or less, and particularly preferably 15 μm or more and 80 μm or less.

[0050] The preferred range of oxygen permeability of the laminated film of the present invention under the conditions of 23°C x 65% RH is 1 ml / m ２ / d / MPa or more, 1300ml / m ２ / d / MPa or less. More preferably, 1200 ml / m ２ / d / MPa or less, more preferably 1000 ml / m ２ / d / MPa or less.

[0051] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. The evaluation methods and physical property measurement methods used in each example and comparative example are as follows.

[0052] (1) Method for Evaluating Contact Angle Values ​​Each substrate film obtained in each Example and Comparative Example was measured on the untreated and treated surfaces of the substrate film in an atmosphere of room temperature 23°C and relative humidity 65% ​​using a contact angle measuring device ("KRUSS DSA100" manufactured by Sanyo Trading Co., Ltd.) using the sessile drop method. 2 μl of water was dropped on the coating layer surface, and the contact angle value was measured 1 second after the drop.

[0053] (2) Ten-point average roughness (Rzjis) (nm) In each example and comparative example, the ten-point average roughness (Rzjis) of the surface of the surface layer (B) side of the obtained base film was measured using a scanning probe microscope (Shimadzu Corporation, "SPM-9700"). Measurements were performed in phase mode over a measurement length range of 2 μm in both the X and Y directions, and the obtained images were corrected (tilt, line fit, noise line removal) and then determined in accordance with the definition described in JIS-B0601 (2001).

[0054] (3) Evaluation Method of Oxygen Permeability The oxygen permeability of the laminated films obtained in each Example and Comparative Example was measured in accordance with JIS-K7126B method using an oxygen permeability measuring device ("OX-TRAN (registered trademark) 1 / 50" manufactured by MOCON Co., Ltd.) under an atmosphere of a temperature of 23°C and a humidity of 65% RH. The oxygen permeability was measured in the direction in which oxygen permeated from the substrate film side.

[0055] [Preparation of Base Film] Details of the polypropylene resin raw materials used in the preparation of the base film below, the film forming conditions, and the raw material blending ratios are shown in Tables 1 to 4.

[0056]

[0057]

[0058]

[0059]

[0060] (OPP-1) For the base layer (A), polypropylene homopolymer PP-1 (Sumitomo Noblen FLX80E4, manufactured by Sumitomo Chemical Co., Ltd.) shown in Table 1 was used. For the surface layer (B), a blend of 96.4 wt% of polypropylene homopolymer PP-1 shown in Table 1 and 3.6 wt% of masterbatch A shown in Table 2 was used. For the surface layer (C), a blend of 94.0 wt% of polypropylene homopolymer PP-1 shown in Table 1 and 6.0 wt% of masterbatch A shown in Table 2 was used. For the base layer (A), a 45 mm extruder was used, for the surface layer (B), a 25 mm extruder was used, and for the surface layer (C), a 20 mm extruder was used. The raw resins were melted at 250 ° C. and co-extruded from a T-die into a sheet, and the surface layer (B) was cooled and solidified so that it came into contact with a cooling roll at 30 ° C., and then stretched 4.5 times in the machine direction (MD) at 135 ° C. Next, in a tenter, both ends of the film in the width direction (TD) were clamped with clips, preheated at 173 ° C, stretched 8.2 times in the width direction (TD) at 164 ° C, and then heat-set at 171 ° C while relaxing 6.7% in the width direction (TD). The film-forming conditions at this time were designated as film-forming conditions a. In this way, a substrate film (biaxially oriented polypropylene film) having a configuration of surface layer (B) / substrate layer (A) / surface layer (C) was obtained. The thickness of the obtained film was 20 μm (thicknesses of surface layer (B) / substrate layer (A) / surface layer (C) were 1.0 μm / 18.0 μm / 1.0 μm).

[0061] [Surface Treatment of Substrate Film] (Example 1) OPP-1 was used as the substrate film, and plasma treatment was performed on the surface of the surface layer (B) side of the substrate film using a Precise 300C atmospheric pressure plasma surface modification device manufactured by E-Square Corporation. The treatment conditions were as follows: nitrogen gas was used; the distance between the substrate film and the treatment source was 5 mm; the discharge power was 1200 W; the discharge electrode length was 0.3 m; and the film running speed was 0.5 m / min. The target substrate film was obtained under the same conditions as Example 1, except that the film running speed was 0.3 m / min. (Comparative Example 1) The target substrate film was obtained under the same conditions as Example 1, except that plasma treatment was not performed. (Comparative Example 2) Corona treatment was performed using a corona treatment device with an IGBT-type high-frequency power supply manufactured by Softal Corona & Plasma GmbH. The target substrate film was obtained under the same conditions as in Example 1, except that the air gas was used, the discharge power was 19,000 W, the discharge electrode length was 9 m, and the film running speed was 250 m / min. (Comparative Example 3) The target substrate film was obtained under the same conditions as in Example 1, except that the film running speed was 0.6 m / min. (Comparative Example 4) The target substrate film was obtained under the same conditions as in Example 1, except that the film running speed was 0.1 m / min. (Comparative Example 5) Plasma treatment was performed using an atmospheric pressure plasma surface modification device, FG5001+1RD1004, manufactured by Nippon Plasmatreat Co., Ltd. The target substrate film was obtained under the same conditions as in Example 1, except that the air gas was used, the distance between the substrate film and the treatment source was 3 mm, the discharge power was 4,200 W, the discharge electrode length was 0.02 m, and the film running speed was 12 m / min.

[0062] [Formation of Inorganic Thin Film Layer] The method for producing the inorganic thin film layer in each Example and Comparative Example is described below. Silicon oxide was vapor-deposited on the surface of the surface layer (B) side of the substrate film to form the inorganic thin film layer. Using a small vacuum vapor deposition device (VWR-400 / ERH, manufactured by ULVAC KIKO Co., Ltd.), silicon oxide was vapor-deposited on the surface of the surface layer (B) side of the substrate film. －３After reducing the pressure to below 10 Pa, granular silicon monoxide was placed in a Nilaco evaporation source B-110 below the substrate and evaporated by heating to form a silicon oxide film (M-1) with a thickness of 30 nm on the film.

[0063] As described above, a substrate film and a laminate film having an inorganic thin film layer on the substrate film were produced. The raw materials and production methods of the films used in the above examples and comparative examples are shown in Tables 1 to 4. In addition, the obtained laminate films were subjected to various evaluations, and the results are shown in Table 5.

[0064]

[0065] According to the present invention, it is possible to provide a film that can be formed into a laminate structure composed of almost a single resin type, mainly a polypropylene film, which has a low environmental impact, and when made into a gas barrier laminate film with an inorganic thin film layer, it is possible to provide a laminate film that has excellent gas barrier properties, is easy to produce, and is economical.

Claims

1. A substrate film for forming an inorganic thin film layer, comprising a substrate film whose main component is a polypropylene-based resin and at least one surface of which is surface-treated, wherein the ratio (C1 / C2) of the water contact angle of the substrate film between the water contact angle of the untreated surface (C1) and the water contact angle of the treated surface (C2) satisfies the relationship of 1.4 or more, and the ten-point average roughness (Rzjis) of the surface of the substrate film is 15 nm or less.

2. A laminated film comprising the substrate film according to claim 1 and an inorganic thin film layer laminated on the treated surface.

3. The laminated film according to claim 2, wherein the inorganic thin film layer contains at least one material selected from the group consisting of silicon oxide, aluminum oxide, and magnesium oxide.

4. Oxygen permeability at 23°C x 65% RH is 1300 ml / m ２ 3. The laminated film according to claim 2, characterized in that the modulus is dMPa or less.

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