Laminated film for forming inorganic thin film layer

Abstract

[Problem] To provide a laminated film which is formed of a laminate of a polypropylene film as a main body and has a basic single resin type with less environmental load, and has gas barrier properties required for a packaging material when an inorganic film layer is laminated. [Means for Solving the Problem] A laminated film for forming an inorganic film layer, characterized by having a cover layer laminated on at least one surface of a base material layer of a polypropylene resin as a main component, and satisfying the following conditions (I) to (III). (I) The heat elongation rate at 130°C of the laminated film is 10% or less in the MD direction and the TD direction. (II) The total of the maximum peak height (Rp) and the maximum valley depth (Rv) obtained by measuring the side surface of the cover layer with a scanning probe microscope is 30.0 nm or less. (III) The attachment amount of the cover layer is 0.10 g / m 2 or more and 0.50 g / m 2 or less.

Description

Technical Field

[0001] This invention relates to laminated films used in the packaging of food, pharmaceuticals, industrial products, etc. More specifically, it relates to laminated films that exhibit excellent gas barrier properties when formed using readily recyclable materials to create a gas barrier film having an inorganic film layer.

[0002] In recent years, countries around the world, particularly in Europe, have strengthened restrictions on reducing the use of single-use plastics. This is accompanied by increased international awareness of resource recycling and the deepening of waste problems in emerging economies. Therefore, from the perspective of the 3Rs (recycle, reuse, reduce), there is a demand for environmentally responsive products for plastic packaging materials used in food, pharmaceuticals, and other products.

[0003] As for the aforementioned performance requirements for environmentally friendly packaging materials, examples include (1) being formed from easily reusable materials; (2) having gas barrier properties that block various gases and extend the shelf life; and (3) forming a laminated structure with low environmental impact (e.g., using less material and being able to reuse materials from a single material).

[0004] In recent years, the use of polypropylene film has received much attention in order to achieve the aforementioned (1) and (3). Polypropylene film is widely used in a wide range of applications, such as food and various commodity packaging, electrical insulation, and surface protection films. Due to its molecular structure, polypropylene film can exhibit high water vapor barrier properties. Furthermore, as a sealant bonded to the substrate film, it is usually a polypropylene-based or polyethylene-based heat-sealing resin. Therefore, by using polypropylene film in the substrate and unstretched polypropylene sheet in the sealant, it is possible to achieve gas barrier properties, realize the single material of the entire packaging material, and make it easy to reuse, thus making it an environmentally friendly packaging material design.

[0005] However, regarding the gas barrier properties mentioned above (2), although polypropylene film has water vapor barrier properties, it is not sufficient compared to transparent inorganic vapor-deposited polyester film, which is generally considered to have excellent water vapor barrier properties, and it has very poor oxygen barrier properties.

[0006] In contrast, barrier laminates are commonly used where a metallic film made of aluminum or an inorganic film made of inorganic oxides such as silicon dioxide or aluminum oxide is formed on the surface of a plastic substrate film such as a polyester film. Among these, films made of inorganic oxides such as silicon dioxide, aluminum oxide, or mixtures thereof are widely used because they eliminate the need for aluminum foil, are transparent, allow for easy identification of the contents, are very thin, and do not impede reusability.

[0007] A method for imparting gas barrier properties by laminating inorganic films in polypropylene films has also been disclosed (e.g., Patent Document 1). However, due to its molecular structure, the surface of polypropylene films has large irregularities, and the inorganic film layers contain many cracks, resulting in insufficient gas barrier properties.

[0008] To address these issues, a method has been disclosed that uses a polyvinyl alcohol polymer resin composition between a polypropylene film and an inorganic film layer to smooth the surface of the inorganic film layer, thereby imparting gas barrier properties (e.g., Patent Document 2). However, if a polyvinyl alcohol polymer resin composition is used, it exhibits high humidity dependence, resulting in reduced oxygen barrier properties under high humidity, and the water vapor barrier properties are also insufficient. Furthermore, to achieve adequate gas barrier performance, a layer thickness of at least 0.5 g / m² is required. 2 The above-mentioned quality is concerning. Increasing the amount of adhesive residue raises concerns about it becoming an impurity during reuse, potentially making reuse itself more difficult. Furthermore, it's unsuitable from a single-material perspective based on a single raw material. Moreover, increasing the amount of adhesive residue also increases manufacturing costs.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: International Publication No. 2017 / 221781

[0012] Patent Document 2: Japanese Patent Application Publication No. 2021-20392 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] In Patent Document 1, the gas barrier performance is insufficient. In Patent Document 2, the gas barrier performance under high humidity is insufficient, and in order to achieve the desired effect, the film thickness needs to be increased, without considering the improvement of processability, environment, and manufacturing costs of the thin film based on the covering layer. That is, there has been no material that meets all three of the following requirements as an environmentally friendly packaging material: (1) it includes reusable materials as constituent materials; (2) it has gas barrier performance that blocks various gases and can extend the shelf life; (3) it forms a laminate structure that is easy to reuse and has low environmental impact (single material).

[0015] This invention was made in light of the problems of the prior art described above.

[0016] That is, the objective of this invention is to provide a laminated film that is composed of a basically single resin type with low environmental impact, which can be used to form a polypropylene film as the main body, and which has the gas barrier properties required for packaging materials when the inorganic film layers are laminated.

[0017] Solution for solving the problem

[0018] The inventors discovered that by designing a laminated film with specified performance that meets the requirements, a film exhibiting good gas barrier properties when laminated with inorganic film layers can be provided, thus completing the present invention.

[0019] That is, the present invention comprises the following components.

[0020] 1. A laminated film for forming an inorganic thin film layer, characterized in that a cover layer is laminated on at least one side of a substrate layer in which a polypropylene resin is the main component, wherein the laminated film satisfies the following conditions (I) to (III).

[0021] (I) The heating elongation of the aforementioned laminated film at 130°C is less than 10% in both the MD and TD directions.

[0022] (II) The total of the maximum peak height (Rp) and maximum valley depth (Rv) obtained by measuring the side surface of the capping layer using a scanning probe microscope is less than 30.0 nm.

[0023] (III) The amount of the coating layer is 0.10 g / m 2 Above and 0.50g / m 2 the following.

[0024] 2. The laminated thin film for forming an inorganic thin film layer as described in 1. above, characterized in that the heating elongation of the laminated thin film at 100°C is less than 3% in both the MD direction and the TD direction.

[0025] 3. The laminated thin film for forming an inorganic thin film layer according to 1. or 2. above, characterized in that, in the total internal reflection infrared absorption spectrum measured from the capping layer side of the aforementioned laminated thin film, at 1070±10 cm⁻¹... -1 The region exhibits the highest absorption peak intensity (P2) at 1720±10 cm⁻¹. -1 The region has a maximum absorption peak intensity (P1) ratio (P2 / P1) of 0.1 or higher and 30.0 or lower.

[0026] 4. A laminated film, characterized in that an inorganic film layer is laminated on the capping layer of the laminated film described in any one of the preceding 1. to 3.

[0027] 5. The laminated thin film according to 4. above, characterized in that the aforementioned inorganic thin film layer contains Al and / or Si.

[0028] The effects of the invention

[0029] Based on the above-described technology, the inventors can provide a laminated film that takes into account the environment and has the gas barrier properties required for packaging materials when the inorganic film layers are laminated. Detailed Implementation

[0030] The present invention will now be described in detail.

[0031] A laminated film for forming an inorganic thin film layer is characterized in that a cover layer is laminated on at least one side of a substrate layer in which a polypropylene resin is the main component, and the laminated film satisfies the following conditions (I) to (III).

[0032] (I) The heating elongation of the aforementioned laminated film at 130°C is less than 10% in both the MD and TD directions.

[0033] (II) The total of the maximum peak height (Rp) and maximum valley depth (Rv) obtained by measuring the side surface of the capping layer using a scanning probe microscope is less than 30.0 nm.

[0034] (III) The amount of the coating layer is 0.10 g / m 2 Above and 0.50g / m 2 the following.

[0035] The following describes each layer of the laminated film.

[0036] [Substrate Thin Film Layer]

[0037] In this invention, the propylene-based resin stretched film used as the substrate film is preferably a biaxially stretched film. The biaxially stretched polypropylene-based resin film can be any known biaxially stretched polypropylene-based resin film, and its raw materials, mixing ratios, etc., are not particularly limited. For example, it can be a polypropylene homopolymer (propylene homopolymer). Alternatively, it can be a random copolymer, block copolymer, or a mixture of two or more α-olefins selected from ethylene, butene, pentene, and hexene, with propylene as the main component. Furthermore, for the purpose of property modification, known additives such as antioxidants, antistatic agents, and plasticizers can be added; for example, petroleum resins and terpene resins can be added.

[0038] Furthermore, the biaxially oriented polypropylene resin film used in this invention can be a single-layer film, or it can be a laminated film composed of multiple resin films comprising a biaxially oriented polypropylene resin film. There are no particular limitations on the type of laminate, the number of layers, or the lamination method used to form the laminated film; any known method can be selected according to the purpose.

[0039] In this invention, the polypropylene resin constituting the substrate film is preferably a propylene homopolymer that is substantially free of comonomers. If comonomers are included, the amount of comonomers is preferably 0.5 mol% or less. The upper limit of the amount of comonomers is more preferably 0.3 mol%, and even more preferably 0.1 mol%. Within the above range, crystallinity is improved, dimensional changes at high temperatures are reduced, that is, the elongation at a certain temperature (hereinafter, heating elongation) is reduced, and heat resistance is improved. It should be noted that comonomers may be included in trace amounts as long as they do not significantly reduce crystallinity.

[0040] The polypropylene resin constituting the substrate film preferably comprises a propylene homopolymer obtained solely from propylene monomers, and even if it is a propylene homopolymer, it is most preferably free of different types of bonds such as head-to-head bonds.

[0041] From a practical standpoint, the lower limit of xylene-soluble substances in the polypropylene resin constituting the substrate film is preferably 0.1% by mass. The upper limit of xylene-soluble substances is preferably 7% by mass, more preferably 6% by mass, and even more preferably 5% by mass. If it is within the above range, the crystallinity is improved, the elongation at heating becomes smaller, and the heat resistance is improved.

[0042] In this invention, the lower limit of the melt flow rate (MFR) of the polypropylene resin (230°C, 2.16 kgf) is preferably 0.5 g / 10 min. More preferably, the lower limit of the MFR is 1.0 g / 10 min, further preferably 2.0 g / 10 min, particularly preferably 4.0 g / 10 min, and most preferably 6.0 g / 10 min. Within these ranges, the mechanical load is low, and extrusion and stretching become easier. The upper limit of the MFR is preferably 20 g / 10 min. More preferably, the upper limit of the MFR is 17 g / 10 min, further preferably 16 g / 10 min, and particularly preferably 15 g / 10 min. Within these ranges, stretching becomes easier, or thickness unevenness is reduced, or stretching temperature and heat setting temperature can be easily increased, heating elongation becomes smaller, and heat resistance is improved.

[0043] From the perspective of heat resistance, the aforementioned substrate film can be a uniaxially stretched film in the longitudinal direction (MD direction) or transverse direction (TD direction), and is preferably a biaxially stretched film. In this invention, by stretching at least along a uniaxial direction, a film with low heat shrinkage at high temperatures and high heat resistance, which is unpredictable in conventional polypropylene films, can be obtained. As stretching methods, simultaneous biaxial stretching and sequential biaxial stretching can be cited, and sequential biaxial stretching is preferred from the perspective of good planarity, dimensional stability, and thickness uniformity.

[0044] As a sequential biaxial stretching method, polypropylene resin is heated and melted in a uniaxial or biaxial extruder at a resin temperature of 200°C to 280°C, formed into a sheet using a T-die, and extruded onto cooling rollers at a temperature of 10°C to 100°C to obtain an unstretched sheet. Next, it can be stretched along the length direction (MD direction) at a temperature of 120°C to 165°C to a ratio of 3.0 to 8.0 times. Then, after preheating in a tenter frame, it is stretched along the transverse direction (TD direction) at a temperature of 155°C to 175°C to a ratio of 4.0 to 20.0 times. Furthermore, after biaxial stretching, it can be heat-set while allowing a relaxation of 1% to 15% at a temperature of 165°C to 175°C.

[0045] For the substrate film used in this invention, in order to impart operability (e.g., rollability after lamination), it is preferable that the film contains particles and forms protrusions on the film surface. Examples of particles contained in the film include inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, and alumina, as well as heat-resistant polymer particles such as acrylic acid, PMMA, nylon, polystyrene, polyester, and benzoguanamine / formalin condensates. From the perspective of transparency, it is preferable that the particle content in the film is low, for example, preferably 1 ppm or more and 1000 ppm or less. Furthermore, the preferred average particle size is 1.0 to 3.0 μm, more preferably 1.0 to 2.7 μm. The method for determining the average particle size is as follows: taking photographs using a scanning electron microscope, measuring the horizontal Freret diameter using an image analyzer, and expressing the average value. Furthermore, from the perspective of transparency, it is preferable to select particles with a refractive index close to that of the resin used. In addition, to impart various functions to the film as needed, it may also contain antioxidants, ultraviolet absorbers, antistatic agents, pigments, lubricants, nucleating agents, adhesives, antifogging agents, flame retardants, antiblocking agents, inorganic or organic fillers, etc.

[0046] In addition to the polypropylene resin used in this invention, other materials may be included in the film to improve the mechanical properties of the substrate film and the adhesion to the ink layer and adhesive layer stacked on the aforementioned gas barrier coating, without impairing the purpose of this invention. Examples include polypropylene resins other than those mentioned above, random copolymers of propylene and ethylene and / or α-olefins with 4 or more carbon atoms, and various elastomers.

[0047] In this invention, the thickness of the substrate film can be arbitrarily set according to various applications, with a lower limit preferably of 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. When the thickness is too thin, the operability tends to become poor. On the other hand, when the thickness is too thick, not only is there a problem in terms of cost, but when it is wound into rolls for storage, it becomes easier for poor winding to occur, resulting in poor planarity.

[0048] From the viewpoint of visibility of the contents, the haze of the polypropylene film used as the substrate of the present invention is preferably transparent, specifically, 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, the cooling roller (CR) temperature is high, the cooling rate of the stretched blank is slow, or there is an excessive amount of low molecular weight material. Therefore, by adjusting these factors, it can be controlled within the aforementioned range.

[0049] Furthermore, in the substrate film layer of the present invention, corona discharge treatment, glow discharge treatment, flame treatment, and surface roughening treatment can be performed as long as it does not impair the purpose of the present invention. In addition, known anchoring coating treatment, printing, decoration, etc. can also be performed.

[0050] [Overlay]

[0051] In this invention, the capping layer provides sufficient gas barrier properties when stacking inorganic film layers. By having a capping layer, the exposure of oligomers from the polypropylene resin and anti-blocking materials can be suppressed. Furthermore, when other layers are stacked on the capping layer, the interlayer adhesion can be improved. In particular, the formation of inorganic film layers presents not only adhesion issues but also problems such as the inability to form films on protruding portions based on surface irregularities, leading to poor gas barrier properties. Moreover, since the capping layer itself uses a gas barrier material, the gas barrier performance of the stacked film can be significantly improved. Furthermore, the capping layer prevents hot water from penetrating the substrate; therefore, as a result, film whitening after boiling or cooking can be reduced.

[0052] In this invention, it is preferable that the coating layer has an adhesion amount of 0.10–0.50 g / m³. 2 Therefore, the coating layer can be uniformly controlled during coating, resulting in a film with less uneven coating or fewer defects. Furthermore, the coating layer helps suppress oligomer exposure, stabilizing the haze after cooking. The preferred coating layer amount is 0.15 g / m³. 2 Above, more preferably 0.20 g / m 2 The above, further optimized, is 0.35g / m 2The preferred value is 0.50 g / m³. 2 Below, more preferably below 0.50 g / m 2 Further optimization of 0.45g / m 2 The following applies: If the amount of coating material exceeds 0.50 g / m². 2 While this improves gas barrier properties, it also weakens the cohesive force within the coating layer, reducing its uniformity and resulting in uneven coating appearance and defects. Furthermore, a thicker film raises concerns about processability, such as adhesion issues or increased manufacturing costs. There are also concerns about its adverse effects on film reusability. On the other hand, if the protective layer thickness is less than 0.10 g / m²... 2 There is a concern that sufficient air barrier properties and interlayer tightness may not be achieved.

[0053] In addition to urethane-based, polyester-based, acrylic, titanium-based, isocyanate-based, imine-based, and polybutadiene-based resins, the resin composition used in the cover layer of this invention may also include resins containing curing agents such as epoxy-based, isocyanate-based, and melamine-based resins. Further, it may include crosslinking agents such as silicone-based crosslinking agents, oxazoline compounds, carbodiimide compounds, and epoxy compounds.

[0054] In particular, the inclusion of polyurethane resin provides barrier properties beyond the high aggregation of the urethane bonds themselves. Furthermore, the polar groups interact with the inorganic film layer, and the presence of the amorphous portion also contributes to its flexibility. Therefore, damage can be suppressed under flexural loads, making it a preferred choice. Polyester resin can also be expected to achieve similar effects, making it suitable. In this invention, polyurethane comprising polyester and isocyanate is preferred; furthermore, from the viewpoint of improving adhesion, the addition of a silicone-based crosslinking agent is more preferable.

[0055] (1) Polyurethane resin

[0056] To improve gas barrier properties, the polyurethane resin used in this invention is more preferably a polyurethane resin containing an aromatic or aromatic aliphatic diisocyanate as a main component. Particularly preferred is the presence of a m-xylene diisocyanate component. By using the above-mentioned resin, the aggregation force of the urethane bonds can be further improved by utilizing the stacking effect of the aromatic rings, resulting in excellent gas barrier properties.

[0057] In this invention, the proportion of aromatic or aromatic aliphatic diisocyanates in the polyurethane resin is preferably set to 50 mol% or more (50-100 mol%) out of 100 mol% of the polyisocyanate component. The total proportion of aromatic or aromatic aliphatic diisocyanates is preferably 60-100 mol%, more preferably 70-100 mol%, and even more preferably 80-100 mol%. If the total proportion of aromatic or aromatic aliphatic diisocyanates is less than 50 mol%, there is a possibility that good gas barrier properties may not be obtained.

[0058] (2) Crosslinking agent

[0059] In the polyurethane resin used in this invention, various crosslinking agents can be incorporated to improve the film's cohesiveness and moisture-heat resistance, without compromising its gas barrier properties. Examples of crosslinking agents include silicone-based crosslinking agents, oxazoline compounds, carbodiimide compounds, and epoxy compounds. Silicone-based crosslinking agents are particularly preferred, especially from the viewpoint of improving water-resistant adhesion to inorganic film layers. Furthermore, oxazoline compounds, carbodiimide compounds, and epoxy compounds can also be used in combination as crosslinking agents.

[0060] From the perspective of crosslinking inorganic and organic substances, silane coupling agents are preferred as silicon-based crosslinking agents. Examples of silane coupling agents include: hydrolyzable alkoxysilane compounds, such as halogenated alkoxysilanes (e.g., 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc., chloroC2-4 alkyltriC1-4 alkoxysilanes), and epoxysilanes with epoxy groups [2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, 3-glycidoxyethyltriethoxysilane, etc.]. propyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane and other glycidoxyC2-4 alkyltriC1-4 alkoxysilanes, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and other glycidoxydiC2-4 alkyldiC1-4 alkoxysilanes, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-Epoxycyclohexyl)propyltrimethoxysilane, etc. (epoxycycloalkyl)C2-4 alkyltriC1-4 alkoxysilanes, etc., alkoxysilanes containing amino groups [2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc., aminoC2-4 alkyltriC1-4 alkoxysilanes, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, etc., aminodiC2-4 alkyldiC1-4 alkoxysilanes, 2-[N-(2-aminoethyl)amino]ethyl Trimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltriethoxysilane, etc. (2-aminoC2-4 alkyl)aminoC2-4 alkyltriC1-4 alkoxysilane, 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane, 3-[N-(2-aminoethyl)amino]propylmethyldiethoxysilane, etc. (aminoC2-4 alkyl)aminodiC2-4 alkyldiC1-4 alkoxysilane, etc., alkanes with mercapto groups alkyl silanes (such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc., thiol-C2-4 alkyltriC1-4 alkoxysilanes, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc., thiol-diC2-4 alkyldiC1-4 alkoxysilanes, etc.), vinyl alkoxysilanes (such as vinyltrimethoxysilane, vinyltriethoxysilane, etc., vinyltriC1-4 alkoxysilanes, etc.), and alkoxysilanes with olefinic unsaturated bonding groups. [2-(meth)acryloyloxyethyltrimethoxysilane, 2-(meth)acryloyloxyethyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, etc. (meth)acryloyloxyC2-4alkyltriC1-4alkoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, etc. (meth)acryloyloxydiC2-4alkyldiC1-4alkoxysilane, etc.] etc. These silane coupling agents can be used alone or in combination of two or more. Among these silane coupling agents, silane coupling agents having an amino group are preferred.

[0061] The silicon-based crosslinking agent is preferably added to the capping layer at 0.05–4.00% by mass, more preferably 0.10–3.50% by mass, and even more preferably 0.15–3.00% by mass. By adding the silane coupling agent, the curing of the membrane is advanced, and the cohesion is improved. As a result, a membrane with excellent water resistance and adhesion is achieved, and the effect of preventing the exposure of oligomers can also be expected. If the addition amount exceeds 3.00% by mass, the curing of the membrane is advanced and the cohesion is improved, but some unreacted portions may be generated, raising concerns about reduced interlayer adhesion. On the other hand, if the addition amount is less than 0.05% by mass, there is a concern that sufficient cohesion may not be obtained.

[0062] (3) Polyester resin

[0063] The polyester resin used in this invention is manufactured by polycondensation of a polycarboxylic acid component and a polyol component. The molecular weight of the polyester is not particularly limited, as long as it imparts sufficient toughness, coating suitability, and solvent solubility to the coating material; a number average molecular weight of 1000 to 50000, more preferably 1500 to 30000, is acceptable. The functional groups at the ends of the polyester are also not particularly limited; they can be alcohol-terminated, carboxylic acid-terminated, or both. When an isocyanate-based curing agent is used, it is necessary to form a polyester polyol primarily composed of alcohol-terminated components.

[0064] The polyester used in this invention preferably has a Tg of 10°C or higher. This is because if the temperature is lower, the resin becomes adhesive after the coating operation, making it prone to sticking and difficult to perform the post-coating winding operation. This is because if the Tg is below 10°C, even with the addition of anti-sticking materials, it is difficult to prevent sticking under high pressure near the core. A more preferred Tg is 15°C or higher, and even more preferably 20°C or higher.

[0065] The polyester used in this invention is produced by polycondensation of a polycarboxylic acid component and a polyol component.

[0066] [Polycarboxylic acid components]

[0067] The polycarboxylic acid component of the polyester used in this invention is characterized by containing at least one of an ortho-oriented aromatic dicarboxylic acid or its anhydride. By forming an ortho-ortho orientation, its solubility in solvents is improved, allowing for uniform coating of the substrate. The uniformly coated capping layer exhibits less fluctuation in barrier properties, thus contributing to the suppression of oligomer whitening. Furthermore, by forming an ortho-ortho orientation, a film with excellent flexibility is formed, and interfacial adhesion is improved. Therefore, damage to the substrate caused by damp heat treatment can be reduced, which is related to the suppression of oligomers.

[0068] Examples of aromatic polycarboxylic acids or their anhydrides that are substituted at the ortho position include phthalic acid or its anhydride, naphthalene 2,3-dicarboxylic acid or its anhydride, naphthalene 1,2-dicarboxylic acid or its anhydride, anthraquinone 2,3-dicarboxylic acid or its anhydride, and 2,3-anthracarboxylic acid or its anhydride. These compounds may have substituents on any carbon atom of the aromatic ring. Examples of such substituents include chloro, bromo, methyl, ethyl, isopropyl, hydroxy, methoxy, ethoxy, phenoxy, methylthio, phenylthio, cyano, nitro, amino, phthalimide, carboxyl, carbamoyl, N-ethylcarbamoyl, phenyl, or naphthyl. Furthermore, polyester polyols containing 70 to 100 mol% of these polycarboxylic acids relative to 100 mol% of the total composition exhibit high barrier properties and excellent solubility as an essential solvent for coating materials, making them particularly preferred.

[0069] In this invention, other polycarboxylic acid components can be copolymerized without impairing the invention's effectiveness. Specifically, as aliphatic polycarboxylic acids, the following substances can be used alone or in mixtures of two or more: succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, etc.; as polycarboxylic acids containing unsaturated bonds, the following substances can be used alone or in mixtures of two or more: maleic anhydride, maleic acid, fumaric acid, etc.; as alicyclic polycarboxylic acids, the following substances can be used alone or in mixtures of two or more: 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, etc.; as aromatic polycarboxylic acids... Polycarboxylic acids, which can be used alone or in mixtures of two or more, include: terephthalic acid, isophthalic acid, pyromellitic acid, trimellitic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, biphenyl dicarboxylic acid and its anhydrides, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid and the anhydrides or esterifying derivatives of these dicarboxylic acids; p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid and the esterifying derivatives of these dihydroxycarboxylic acids, etc. From the viewpoint of organic solvent solubility and gas barrier properties, succinic acid, 1,3-cyclopentanedicarboxylic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, and biphenyl dicarboxylic acid are preferred.

[0070] [Polyol Components]

[0071] The polyol component of the polyester used in this invention is not particularly limited as long as it can synthesize a polyester exhibiting gas barrier properties. Preferably, it contains at least one polyol component selected from the group consisting of ethylene glycol, propylene glycol, butanediol, neopentyl glycol, cyclohexanediol, and 1,3-dihydroxyethylbenzene. It is presumed that the fewer carbon atoms between oxygen atoms, the less flexible the molecular chain becomes, and the less permeable to oxygen. Therefore, ethylene glycol is most preferably used as the main component.

[0072] In this invention, the aforementioned polyol components are preferably used; however, other polyol components may also be copolymerized without impairing the effects of this invention. Specifically, examples of diols include 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, methylpentanediol, dimethylbutanediol, butylethyl propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Examples of tri- or higher alcohols include glycerol, trimethylolpropane, trimethylolethane, tri(2-hydroxyethyl) isocyanurate, 1,2,4-butanetriol, pentaerythritol, and dipentaerythritol. In particular, polyesters containing glycerol and tri(2-hydroxyethyl) isocyanurate within triols exhibit moderately high crosslinking density due to their branched structure, resulting in good organic solvent solubility and excellent barrier properties, and are therefore particularly preferred.

[0073] Examples of catalysts used in the reaction to obtain the polyester of the present invention include tin-based catalysts such as monobutyltin oxide and dibutyltin oxide, titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, and zirconium oxide-based catalysts such as tetrabutyl zirconate. Preferably, a combination of the aforementioned titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, which have high activity for esterification reactions, and the aforementioned zirconium oxide catalysts is used. The amount of the aforementioned catalyst is 1 to 1000 ppm relative to the total mass of the reactants used, more preferably 10 to 100 ppm. If it is less than 1 ppm, it is difficult to obtain the desired catalytic effect; if it is more than 1000 ppm, when using an isocyanate curing agent, it may sometimes hinder the urethane esterification reaction.

[0074] (4) Isocyanate-based curing agents

[0075] In this invention, when polyester resin is used as the main agent constituting the coating layer, an isocyanate-based agent is required as a curing agent to form a polyurethane resin. In this case, the coating layer becomes cross-linked, thus offering advantages such as improved heat resistance, abrasion resistance, and stiffness. Therefore, it is also easily used in boiling and retort packaging. On the other hand, there are problems such as: the liquid cannot be reused after mixing the curing agent, and a curing (aging) process is required after coating. As an advantage, as a simple external varnish, examples include: no concern about thickening of the coating liquid, easy management of coating manufacturing, the ability to dilute and reuse the coating liquid, and the elimination of a curing process (so-called aging process). In this case, the polyester used can be terminated in polyols, polycarboxylic acids, or mixtures of both, all without problems. On the other hand, the resin in the coating layer is linear, therefore, sometimes insufficient heat resistance and abrasion resistance occur, and it is not suitable for boiling and retort packaging.

[0076] When a curing agent is used in the coating layer, since it is a coating of a thin film, isocyanate curing systems are preferred from the viewpoint of the film's heat resistance. In this case, the resin component of the coating material must be a polyester polyol. On the other hand, when an epoxy compound is used as the curing agent, it must be a polyester polycarboxylic acid. In these cases, the coating layer becomes cross-linked, thus offering advantages in heat resistance, abrasion resistance, and improved stiffness. Therefore, it is also easy to use for boiling and retort packaging. On the other hand, there are also problems such as the inability to reuse the liquid after mixing the curing agent and the need for a curing (aging) process after coating.

[0077] In the case of the polyisocyanate compound used in this invention, when the polyester has hydroxyl groups, at least a portion reacts to form a urethane structure, thereby becoming highly polar as a resin component. This further enhances the gas barrier function by causing aggregation between polymer chains. Furthermore, when the resin of the coating material is a linear resin, crosslinking with a ternary or higher polyisocyanate imparts heat resistance and abrasion resistance. The polyisocyanate compound used in this invention can be a diisocyanate, a ternary or higher polyisocyanate, a low-molecular-weight compound, or a high-molecular-weight compound; however, if a portion of the backbone contains an aromatic ring or an aliphatic ring, it is preferred from the viewpoint of improving the gas barrier function. Examples include: toluene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, naphthalene diisocyanate, which are isocyanates having aromatic rings; hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, norbornane diisocyanate, which are isocyanates having aliphatic rings; or trimers of these isocyanate compounds; and compounds containing terminal isocyanate groups obtained by reacting excess of these isocyanate compounds with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerol, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, etc., or high-molecular-weight active hydrogen compounds such as various polyester polyols, polyether polyols, and polyamides.

[0078] The coating method for the resin composition used for the coating layer is not particularly limited as long as it is a method of forming a layer by coating it onto the surface of a film. For example, conventional coating methods such as gravure coating, reverse roller coating, wire rod coating, and die coating can be used.

[0079] When forming the coating layer, it is preferable to apply the resin composition for the coating layer and then heat-dry it. The drying temperature is preferably 100–145°C, more preferably 110–140°C, and even more preferably 110–130°C. If the drying temperature is below 100°C, there is a concern that the coating layer may not dry sufficiently. On the other hand, if the drying temperature exceeds 145°C, excessive heat will be applied to the film, which may cause the film to become brittle or shrink, resulting in poor processability. In particular, it is especially preferable to first evaporate the solvent at a relatively low temperature of 80°C–110°C immediately after coating, and then dry it at a temperature above 120°C to obtain a uniform film. Furthermore, it is even more effective in terms of film formation of the coating layer to apply additional heat treatment in a low-temperature region, rather than drying.

[0080] [Inorganic Thin Film Layer]

[0081] The laminated film of the present invention can have an inorganic film layer on the surface of the aforementioned cover layer. The inorganic film layer is a film formed of metal or inorganic oxide. There are no particular limitations on the material forming the inorganic film layer, as long as it can form a film. From the viewpoint of gas barrier properties, inorganic oxides such as aluminum, silicon dioxide, aluminum oxide, and mixtures of silicon dioxide and aluminum oxide are preferred. In this composite oxide, the mixing ratio of silicon dioxide and aluminum oxide is preferably in the range of 20 to 70% by mass (Al, based on the mass ratio of the metal components). If the Al concentration is below 20% by mass, the water vapor barrier properties may become lower. On the other hand, if it exceeds 70% by mass, the inorganic film layer tends to harden, and there is a concern that the film may be damaged during secondary processing such as printing and lamination, thereby reducing the gas barrier properties. In addition, when the Al concentration is 100% by mass, the water vapor barrier performance becomes good, but since it is a single material, there is a tendency for the surface to be smooth, resulting in poor slippage and making it easy to produce processing defects (wrinkles, acne, etc.). It should be noted that silicon oxide here refers to various silicon oxides such as SiO and SiO2 or mixtures thereof, while aluminum oxide refers to various aluminum oxides such as AlO and Al2O3 or mixtures thereof.

[0082] The thickness of inorganic thin film layers is typically 1–100 nm, preferably 5–50 nm. If the thickness of the inorganic thin film layer is less than 1 nm, it is sometimes difficult to obtain satisfactory gas barrier properties. On the other hand, even if it exceeds 100 nm and becomes excessively thick, it does not achieve a comparable improvement in gas barrier properties, and becomes disadvantageous in terms of bending resistance and manufacturing cost.

[0083] There are no particular limitations on the method for forming inorganic thin film layers. For example, physical vapor deposition (PVD) methods such as vacuum evaporation, sputtering, and ion plating, or known vapor deposition methods such as chemical vapor deposition (CVD) can be used. Hereinafter, a typical method for forming inorganic thin film layers will be described using silicon oxide / alumina-based thin films as an example. For example, in the case of vacuum evaporation, a mixture of SiO2 and Al2O3, or a mixture of SiO2 and Al, is preferably used as the evaporation raw material. Particles are usually used as these evaporation raw materials, but in this case, the size of each particle is desired to maintain the degree of pressure stability during evaporation; a particle size of 1 mm to 5 mm is preferred. Heating can be performed using resistance heating, high-frequency induction heating, electron beam heating, laser heating, etc. Alternatively, reactive vapor deposition can be performed by introducing oxygen, nitrogen, hydrogen, argon, carbon dioxide, water vapor, etc., as reactant gases, or by using ozone addition or ion-assisted methods. Furthermore, the film formation conditions, such as applying a bias voltage to the deposited object (the laminated thin film for evaporation), or heating or cooling the deposited object, can be arbitrarily changed. The evaporation material, reactant gas, bias voltage of the deposited object, heating, and cooling can be changed in the same way as in sputtering or CVD methods.

[0084] [Protective Layer]

[0085] In this invention, when further gas barrier properties are required, or when processing such as printing is needed, a protective layer can be provided on the aforementioned inorganic thin film layer. The inorganic thin film layer is not a completely dense film and contains scattered, minute defects. By coating the inorganic thin film layer with a specific protective layer resin composition (described later) to form a protective layer, the resin in the protective layer resin composition penetrates into the defects of the inorganic thin film layer, resulting in stable gas barrier properties. Furthermore, the protective layer itself uses a gas barrier material, thereby significantly improving the gas barrier properties of the laminated film. It should be noted that by providing a protective layer, the cost increases due to the added processing steps, and the materials used create an environmental burden. Additionally, it should be noted that the protective layer causes changes in physical properties such as surface roughness.

[0086] The preferred adhesion amount of the protective layer is 0.10–0.50 g / m³. 2 Therefore, the protective layer can be uniformly controlled during coating, resulting in a film with less uneven coating or fewer defects. Furthermore, the adhesion of the protective layer itself is improved, and the bond between the inorganic film layer and the protective layer becomes stronger. If the amount of protective layer adhered exceeds 0.50 g / m²... 2While this improves gas barrier properties, it also weakens the cohesive force within the protective layer and reduces its uniformity. Consequently, unevenness and defects may occur in the coating appearance, or the gas barrier and adhesion properties may not be fully realized. On the other hand, if the protective layer thickness is less than 0.10 g / m²... 2 There is a concern that sufficient air barrier properties and interlayer tightness may not be achieved.

[0087] Examples of resin compositions used in the protective layer formed on the surface of the inorganic film layer of the laminated film of the present invention include resins containing curing agents such as epoxy, isocyanate, and melamine, which are resins of vinyl alcohol, urethane, polyester, acrylic, titanium, isocyanate, imine, and polybutadiene.

[0088] The coating method for the protective layer resin composition is not particularly limited as long as it is a method of forming a layer by coating it onto the surface of a film. For example, common coating methods such as gravure coating, reverse roller coating, wire rod coating, and die coating can be used.

[0089] [Laminated Thin Film]

[0090] The laminated films of the present invention exhibit the following film properties. It should be noted that the following properties were measured and evaluated using the methods described later in the examples.

[0091] The 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, further preferably 12 μm or more and 100 μm or less, and particularly preferably 15 μm or more and 80 μm or less.

[0092] In addition, the thickness of all substrate layers is preferably 50% or more and 99% or less, more preferably 60% or more and 97% or less, particularly preferably 70% or more and 95% or less, and most preferably 80% or more and 92% or less, relative to the overall thickness of the film.

[0093] In the laminated thin film of the present invention, the total reflectance infrared absorption spectrum of the capping layer is at 1070±10 cm⁻¹ -1 The region exhibits the highest absorption peak intensity (P2) at 1720±10 cm⁻¹. -1 The ratio (P2 / P1) of the peak intensity of maximum absorption in the region having the highest absorption peak is preferably in the range of 0.1 or higher and 30.0 or lower. Preferably, it is in the range of 0.1 to 20.0, more preferably in the range of 0.2 to 10.0. (1720±10cm) -1 The peak originates from the C=O structure of aromatic and aromatic aliphatic ester skeletons, serving as an indicator of the amount of polyester skeleton. Additionally, 1070±10 cm⁻¹ -1The peak originating from C-OH is an indicator of the amount of hydroxyl groups derived from the polyester in the capping layer. (P2 / P1) represents the ratio of hydroxyl groups in the polyester backbone. When this ratio is within the aforementioned range, the film becomes highly polarized without compromising its toughness. When the inorganic film layer is laminated, the adhesion between the capping layer and the inorganic film layer is increased, resulting in maximum gas barrier properties. If (P2 / P1) is below 0.1, the amount of hydroxyl groups in the capping layer is low, and the film formation of the inorganic film layer becomes sparse, sometimes making it difficult to achieve gas barrier properties. On the other hand, if (P2 / P1) exceeds 30.0, the bonding force with the inorganic film layer is enhanced, but cross-linking in the capping layer does not occur, raising concerns about reduced film-forming properties and brittleness. To ensure that the (P2 / P1) value of the capping layer is within the aforementioned specified range, it is necessary to use the aforementioned materials to achieve the aforementioned specified adhesion amount, further ensuring that the material mixing ratio is within the aforementioned suitability range, and combining this with the drying and heat treatment conditions described later.

[0094] In the laminated film of the present invention, the heating elongation at 100°C is preferably 3% or less in both the MD direction and TD direction. Therefore, since the substrate is less prone to elongation due to heat received from the evaporation source and vapor-deposited particles during the lamination of the inorganic film layers, the gas barrier properties and quality can be further improved. The heating elongation in the MD direction and TD direction at 100°C is preferably 2.8% or less, more preferably 2.5% or less, and the lower limit is preferably 0%. If the heating elongation in the MD direction at 100°C exceeds 3%, the laminated film will deform due to heat received from the evaporation source and vapor-deposited particles during the lamination of the inorganic film layers, sometimes resulting in a decrease in gas barrier properties or quality.

[0095] Furthermore, the heating elongation at 130°C is preferably 10% or less in both the MD and TD directions. The heating elongation in both the MD and TD directions at 130°C is preferably 8% or less, more preferably 7% or less, even more preferably 6.5% or less, and the lower limit is preferably 0%.

[0096] In this invention, the heating elongation is a value measured by the TMA method, based more specifically on the method described in the embodiments.

[0097] The sum of the maximum peak height (Rp) and maximum valley depth (Rv) of the surface of the capping layer side of the laminated thin film of the present invention, based on scanning probe microscopy (AFM), is suitable to be 0.1 nm or more and 30.0 nm or less. The maximum peak height (Rp) and maximum valley depth (Rv) are determined according to the definition described in JIS-B0601 (1994) after measurement in dynamic mode using scanning probe microscopy (AFM) with a measurement length of 2 μm in both the X and Y directions, and after correction (slope, straight line fitting, noise line removal) of the obtained image.

[0098] The maximum peak height (Rp) and maximum valley depth (Rv) within a 2μm square range based on AFM are indicators of the unevenness of the resin itself, beyond the large peaks and valleys formed by anti-blocking agents and lubricants. When an inorganic film layer is laminated on the surface of the capping layer, the unevenness may lead to poor formation of the inorganic film layer and induce cracking. When the total of the maximum peak height (Rp) and maximum valley depth (Rv) exceeds 30.0 nm, the surface unevenness is large, which can cause delamination during the formation of the inorganic film and result in poor barrier properties. The total of the maximum peak height (Rp) and maximum valley depth (Rv) on the side surface of the capping layer is more preferably 20.0 nm or less, more preferably 10.0 nm or less, and most preferably 7.0 nm or less.

[0099] When an inorganic film layer is laminated on the laminated film of the present invention, the oxygen permeability under the conditions of 23°C × 65% RH is preferably 15 cc / m. 2 / d / atm or less. More preferably 10cc / m 2 Below / d / atm, further optimization is 8cc / m 2 Below / d / atm. The preferred lower limit for oxygen permeability is 0.1cc / m. 2 / d / atm or higher. Additionally, the water vapor transmission rate under 40℃×90%RH conditions is preferably 3.0 g / m. 2 / d or less. Further preferred is 2.5g / m 2 / d or less, more preferably 2.0g / m 2 The preferred lower limit for water vapor transmission rate is 0.1 g / m². 2 / d or more.

[0100] [Layered Body]

[0101] When the laminated film of the present invention is used as a packaging material, it is preferable to form a laminate having a heat-sealing resin layer, referred to as a sealant. The heat-sealing resin layer is typically disposed on the side of the cover layer or inorganic film layer, but sometimes it is disposed on the outside of the substrate film layer (the side opposite to the inorganic film forming surface). The heat-sealing resin layer is typically formed using extrusion lamination or dry lamination. As the thermoplastic polymer forming the heat-sealing resin layer, any olefin-based polyethylene resin such as HDPE, LDPE, and LLDPE, polypropylene resin, ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, ionomer resin, etc., can be used, as long as sufficient adhesive properties of the sealant are achieved. Among these, LLDPE or polypropylene resin, which has high versatility, is particularly preferred from the viewpoints of durability, sealing strength, price, and simplification. The thickness of the sealant layer is preferably 20–100 μm, more preferably 30–90 μm, and more preferably 40–80 μm. If the thickness is less than 20 μm, sufficient sealing strength cannot be obtained, and the sealant may lack firmness and be difficult to handle. On the other hand, if the thickness exceeds 100μm, in addition to the increased rigidity which reduces its operability as a bag, there is also a concern that the price will become more expensive.

[0102] [Adhesive layer]

[0103] The adhesive layer used in this invention can be a general-purpose laminating adhesive. For example, solvent-free, water-based, or hot-melt adhesives with polyurethane, polyester, polyamide, epoxy, poly(meth)acrylic, polyethyleneimine, ethylene-(meth)acrylic acid, polyvinyl acetate, (modified) polyolefin, polybutadiene, wax, or casein as main components can be used. Among these, urethane or polyester adhesives are preferred, considering heat resistance and flexibility to adapt to the thermal elongation of each substrate. The lamination method for the above adhesive layer can be, for example, direct gravure coating, reverse gravure coating, lip coating, die coating, roller coating, dip coating, knife coating, spray coating, fountain coating, or other methods. To achieve sufficient adhesion, the coating amount after drying is preferably 1–8 g / m³. 2 More preferably 2-7 g / m 2 Further optimization of 3-6 g / m 2 If the coating amount is less than 1g / m 2 If this is not achieved, it becomes difficult to adhere to the entire surface, resulting in reduced adhesion. Additionally, if it exceeds 8g / m²... 2 If the film takes too long to fully cure, it becomes more likely to leave unreacted residues, resulting in reduced adhesion.

[0104] [Printed Layer]

[0105] Furthermore, in the laminated film of the present invention, at least one or more printed layers, other plastic substrates and / or paper substrates may be laminated between or on the outside of the substrate film layer and the heat-sealing resin layer.

[0106] As the printing ink for forming the printing layer, water-based and solvent-based resin-containing printing inks are preferred. Examples of resins used in the printing ink 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-shielding agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, defoamers, crosslinking agents, anti-blocking agents, and antioxidants. The printing method for setting the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. Known drying methods such as hot air drying, hot roller drying, and infrared drying can be used for drying the solvent after printing.

[0107] Example

[0108] Next, the present invention will be described in further detail with reference to embodiments, but the present invention is not limited to the following examples. It should be noted that the evaluation of the thin film is performed according to the following measurement method.

[0109] [Determination Method]

[0110] (1) Method for determining the total reflectance infrared absorption spectrum of laminated thin films

[0111] In each embodiment and comparative example, for the surface of the capping layer of each laminated film monomer obtained in the stage of laminating a capping layer on the substrate film, the total internal reflection infrared absorption spectrum was measured by total internal reflection absorption infrared spectrometry, and the value at 1720±10cm was determined. -1 The region exhibits the highest absorption peak intensity (P1) and at 1070±10 cm⁻¹. -1 The region with the maximum absorption peak intensity (P2) is calculated, and the intensity ratio (P2 / P1) is determined. The peak intensity is calculated based on the peak height obtained by perpendicularly connecting the baseline with zero absorbance to each peak apex.

[0112] (2) Maximum peak height (Rp) and maximum valley depth (Rv) (nm)

[0113] In each embodiment and comparative example, the maximum peak height (Rp) and maximum valley depth (Rv) of the capping layer side of the obtained laminated film were measured using a scanning probe microscope (Shimadzu SPM-9700). Measurements were performed in phase mode within a measurement length of 2 μm in both the X and Y directions. After correcting the obtained image (slope, straight line fitting, noise line removal), the measurements were determined according to the definitions described in JIS-B0601 (1994).

[0114] (3) Adhesion amount of the coating layer

[0115] In each embodiment and comparative example, each laminated film obtained in the stage of laminating a cover layer on a substrate film is used as a sample. A 100mm × 100mm test piece is cut from the sample, and the cover layer is wiped with acetone. The adhesion amount is calculated from the mass change of the film before and after wiping.

[0116] (4) Elongation at heating (%)

[0117] In each embodiment and comparative example, the elongation at heating was determined using a thermomechanical analysis apparatus (Shimadzu Corporation's "TMA-60") based on temperature-modulated TMA.

[0118] The thermal elongation in the MD direction is as follows: Strips were cut from the laminated films of the examples and comparative examples, with a width of 30 mm along the MD direction and a width of 4 mm along the TD direction, to prepare samples. The measurement conditions were as follows: the chuck spacing was set to 10 mm, the measurement temperature range was set to 30°C to 150°C, the heating rate was set to 20°C / min, and the tensile load applied to the sample sheet was set to 0.39 N. The thermal elongation was calculated from the chuck spacing (mm) when the furnace temperature reached 100°C and the chuck spacing (mm) when it reached 130°C.

[0119] The thermal elongation in the TD direction is as follows: Strips were cut from the laminated films of the examples and comparative examples, with a width of 30 mm along the TD direction and a width of 4 mm along the MD direction, to prepare samples. The measurement conditions were as follows: the chuck spacing was set to 10 mm, the measurement temperature range was set to 30°C to 150°C, the heating rate was set to 20°C / min, and the tensile load applied to the sample sheet was set to 0.39 N. The thermal elongation was calculated from the chuck spacing (mm) when the furnace temperature reached 100°C and the chuck spacing (mm) when it reached 130°C.

[0120] The elongation at 100°C (S100) and the elongation at 130°C (S130) are calculated using the following formulas.

[0121] (S100) = (Chuck spacing at 100℃ - Chuck spacing before heating) / Chuck spacing before heating × 100

[0122] (S130) = (Chuck spacing at 130℃ - Chuck spacing before heating) / Chuck spacing before heating × 100

[0123] (5) Composition and thickness of inorganic thin film layers

[0124] For the laminated films (after film stacking) obtained in the examples and comparative examples, the film thickness composition was determined using a fluorescence X-ray analysis apparatus (Rigaku Corporation "ZSX100e") and a pre-prepared standard curve. It should be noted that the conditions for exciting the X-ray tube were set to 50 kV and 70 mA.

[0125] (6) Evaluation method of oxygen permeability

[0126] For the laminated films (after lamination) obtained in each embodiment and comparative example, the oxygen permeability was measured using an oxygen permeability measuring device (MOCON "OX-TRAN (registered trademark) 1 / 50") in an atmosphere of 23°C and 65% RH, according to the JIS-K7126B method. It should be noted that the oxygen permeability was measured in the direction in which oxygen permeates from the substrate layer side.

[0127] (7) Evaluation method of water vapor transmission rate

[0128] For the laminated films (after lamination) obtained in each embodiment and comparative example, the water vapor transmission rate was measured using a water vapor transmission rate measuring apparatus (MOCON "PERMATRAN-W3 / 33MG") at a temperature of 40°C and a humidity of 90% RH, according to the JIS-K7129B method. It should be noted that the water vapor transmission rate was measured in the direction in which water vapor passes through from the substrate layer side.

[0129] (8) Appearance evaluation method

[0130] In each embodiment and comparative example, after the cover layer is laminated, the appearance of the side surface of the cover layer is visually evaluated.

[0131] ○: No defects occurred, good

[0132] ×: Any defects such as wrinkles, uneven coating, or pinholes have occurred.

[0133] [Fabrication of the Substrate Thin Film Layer]

[0134] The details of the polypropylene resin raw materials used in the production of the following polyolefin substrate films, the film-making conditions, and the raw material mixing ratios are shown in Tables 1 to 4.

[0135] [Table 1]

[0136]

[0137] [Table 2]

[0138]

[0139] [Table 3]

[0140] Thin film forming conditions a b Melting resin temperature (°C) 250 250 Cooling roller temperature (°C) 30 30 Longitudinal stretch ratio (times) 4.5 4.5 Longitudinal tensile temperature (°C) 135 125 Width-direction stretch ratio (times) 8.2 8.2 Width-direction stretching preheating temperature (°C) 173 168 Tensile temperature in the width direction (°C) 164 155 Heat setting temperature (°C) 171 165 Relaxation rate in the width direction (%) 6.7 6.7

[0141] [Table 4]

[0142]

[0143] (OPP-1)

[0144] The substrate layer (A) uses polypropylene homopolymer PP-1 as shown in Table 1.

[0145] In addition, the surface layer (B) is made by mixing polypropylene homopolymer PP-1 as shown in Table 1 at a ratio of 96.4% by weight and masterbatch A as shown in Table 2 at a ratio of 3.6% by weight.

[0146] The surface layer (C) is made by blending polypropylene homopolymer PP-1 as shown in Table 1 at a ratio of 94.0% by weight and masterbatch A as shown in Table 2 at a ratio of 6.0% by weight.

[0147] The substrate layer (A) was extruded using a 45mm extruder, the surface layer (B) using a 25mm extruder, and the surface layer (C) using a 20mm extruder. The raw resin was melted at 250°C and co-extruded into sheets through a T-die. The surface layer (B) was cooled and cured by contacting a 30°C cooling roller, and then stretched to 4.5 times its original length in the longitudinal direction (MD) at 135°C. Then, in a tenter frame, the film was held at both ends in the width direction (TD) by clamps, preheated at 173°C, and stretched to 8.2 times its original length in the width direction (TD) at 164°C. After a 6.7% relaxation in the width direction (TD), it was heat-set at 171°C. These film-forming conditions are set as film-forming condition a.

[0148] Thus, a biaxially oriented polypropylene film consisting of surface layer (B), substrate layer (A), and surface layer (C) was obtained.

[0149] The surface of the surface layer (B) of a biaxially oriented polypropylene film was corona treated using a corona treatment machine manufactured by SOFTAL Corona & Plasma GmbH at an applied current of 0.75 A, and then wound up using a winding machine. The resulting film had a thickness of 20 μm (the thicknesses of the surface layer (B) / substrate layer (A) / surface layer (C) were 1.0 μm / 18.0 μm / 1.0 μm).

[0150] (OPP-2)

[0151] The substrate layer (A) uses 40.0% by weight of polypropylene homopolymer PP-2 as shown in Table 1 and 60.0% by weight of polypropylene homopolymer PP-3 as shown in Table 1.

[0152] In addition, the surface layer (B) is made by mixing polypropylene homopolymer PP-3 as shown in Table 1 at a ratio of 96.4% by weight and masterbatch A as shown in Table 2 at a ratio of 3.6% by weight.

[0153] The surface layer (C) is made by blending polypropylene homopolymer PP-3 as shown in Table 1 at a ratio of 94.0% by weight and masterbatch A as shown in Table 2 at a ratio of 6.0% by weight.

[0154] The substrate layer (A) was extruded using a 45mm extruder, the surface layer (B) using a 25mm extruder, and the surface layer (C) using a 20mm extruder. The raw resin was melted at 250°C and co-extruded into sheets through a T-die. After surface layer (B) was cooled and cured by contact with a 30°C cooling roller, it was stretched to 4.5 times its original length in the longitudinal direction (MD) at 125°C. Then, in a tenter frame, the film was held at both ends in the width direction (TD) by clamps, preheated at 168°C, stretched to 8.2 times its original length in the width direction (TD) at 155°C, and then heat-set at 165°C while relaxing by 6.7% in the width direction (TD). These film-forming conditions are set as film-forming condition b.

[0155] Thus, a biaxially oriented polypropylene film consisting of surface layer (B), substrate layer (A), and surface layer (C) was obtained.

[0156] The surface of the surface layer (B) of a biaxially oriented polypropylene film was corona treated using a corona treatment machine manufactured by SOFTAL Corona & Plasma GmbH at an applied current of 0.75 A, and then wound up using a winding machine. The resulting film had a thickness of 20 μm (the thicknesses of the surface layer (B) / substrate layer (A) / surface layer (C) were 1.0 μm / 18.0 μm / 1.0 μm).

[0157] [Creating an overlay]

[0158] The following illustrates the methods for fabricating the cover layer used in the various embodiments and comparative examples.

[0159] [Polyester Resin (A)]

[0160] Polyester polyol (DIC Corporation's "DF-COAT GEC-004C": 30% solids content) was used as the polyester component.

[0161] [Polyisocyanate crosslinking agent (B)]

[0162] The trimethylolpropane adduct of m-xylene diisocyanate (Mitsui Chemicals Co., Ltd. "Takenate D-110N": 75% solids) was used as the polyisocyanate component.

[0163] [Silane Coupling Agent (C)]

[0164] N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd. "KBM-603") was used as a silane coupling agent.

[0165] [Polyurethane Resin (D)]

[0166] A dispersion of polyester polyurethane resin (DIC Corporation's "HYDRAN (registered trademark) AP-201"; solids content 23%) was used as the polyurethane resin.

[0167] [Polyurethane Resin (E)]

[0168] A dispersion of polyester polyurethane resin (Mitsui Chemicals Co., Ltd. "TAKELAC (registered trademark) WPB531"; solids content 30%) was used as the polyurethane resin.

[0169] [Coating Solution 1]

[0170] A solution (15% by mass) of silane coupling agent (C) dissolved in acetone and isocyanate (B) are mixed in the following ratio and stirred with a magnetic stirrer for 10 minutes. The resulting mixture is diluted with methyl ethyl ketone and 1-methoxy-2-propanol (hereinafter PGM), and polyester resin (A) is further added to obtain target coating solution 1. The mixing ratios are shown below.

[0171] Polyester resin (A) 10.62% by mass

[0172] Isocyanate (B) 4.07% by mass

[0173] Silane coupling agent (C) ※ Acetone diluent 1.73% by mass

[0174] Methyl ethyl ketone 69.55% by mass

[0175] PGM 14.03% by mass

[0176] [Coating Liquid 2]

[0177] Mix the following coating agents to prepare coating solution 2.

[0178] Water 43.91% by mass

[0179] Isopropanol 30.00% by mass

[0180] Polyurethane resin (D) 26.09% by mass

[0181] [Coating Liquid 3]

[0182] Mix the following coating agents to prepare coating solution 3.

[0183] Water 46.00% by mass

[0184] Isopropanol 30.00% by mass

[0185] Polyurethane resin (E) 24.00% by mass

[0186] [Fabrication of laminated thin films]

[0187] (Examples 1 and 2)

[0188] The substrate film used was OPP-1, and the cover layer used was coating solution 1. The coating was applied to the corona-treated surface of the substrate film using a gravure roller coating method and dried in a 130°C oven for 10 seconds. At this point, the coating thickness was 0.40 g / m². 2 Afterwards, a post-heat treatment at 40°C for 2 days was performed to obtain the target laminated film.

[0189] (Example 3)

[0190] The target laminated film was obtained under the same conditions as in Example 1, except that coating liquid 2 was used as the covering layer.

[0191] (Example 4)

[0192] The coating thickness was changed to 0.25 g / m². 2 In addition, the target laminated film was obtained under the same conditions as in Example 1.

[0193] (Example 5)

[0194] The drying temperature was changed to 110°C, but otherwise the target laminated film was obtained under the same conditions as in Example 1.

[0195] (Example 6)

[0196] The drying temperature was changed to 150°C, but otherwise the target laminated film was obtained under the same conditions as in Example 1.

[0197] (Comparative Example 1)

[0198] The same substrate film as in Example 1 is used, but without the overlay layer.

[0199] (Comparative Example 2)

[0200] The target laminated film was obtained under the same conditions as in Example 1, except that coating liquid 3 was used as the cover layer.

[0201] (Comparative Example 3)

[0202] OPP-2 was used as the substrate film, and the target laminated film was obtained under the same conditions as in Example 1.

[0203] [Formation of Inorganic Thin Film Layers]

[0204] The following illustrates the methods for fabricating the inorganic thin film layers used in the various embodiments and comparative examples.

[0205] (M-1; Example 1, Comparative Example 1)

[0206] As the inorganic thin film layer M-1, a composite oxide layer of silicon dioxide and aluminum oxide is formed on the capping layer by electron beam evaporation. As the evaporation source, granular SiO2 (99.9% purity) and Al2O3 (99.9% purity) with a diameter of approximately 3 mm to 5 mm are used. The resulting film (containing the inorganic thin film layer / capping layer) has an inorganic thin film layer (SiO2 / Al2O3 composite oxide layer) thickness of 13 nm. Furthermore, the composition of this composite oxide layer is SiO2 / Al2O3 (mass ratio) = 60 / 40.

[0207] (M-2; Examples 2-6, Comparative Examples 2-3)

[0208] As the inorganic thin film layer M-2, metallic aluminum was deposited on the capping layer by vapor deposition. A small vacuum vapor deposition apparatus (ULVAC Machine Co., Ltd., VWR-400 / ERH) was used, with the pressure reduced to 10. -3 After Pa is below, aluminum foil with a purity of 99.9% is mounted on the Nilaco CF-305W vapor deposition source from the bottom of the substrate, and the aluminum is heated and evaporated to form a 40nm thick aluminum film on the thin film.

[0209] Various evaluations were performed on the laminated films obtained as described above, and the results are shown in Table 5.

[0210] [Table 5A]

[0211]

[0212] [Table 5B]

[0213]

[0214] Industrial availability

[0215] According to the present invention, a laminated film can be provided that is composed of a basically single resin type with low environmental impact, which is used to form a polypropylene film as the main body, and has the gas barrier properties required for packaging materials when the inorganic film layers are laminated.

Claims

1. A laminated thin film for forming an inorganic thin film layer, characterized in that, It has a cover layer laminated on at least one side of the substrate layer, which uses polypropylene resin as the main component. The total internal reflection infrared absorption spectrum measured from the capping layer side of the stacked thin film shows that at 1070±10 cm⁻¹... -1 The region exhibits the highest absorption peak intensity P2 at 1720±10 cm⁻¹. -1 The region has a maximum absorption peak intensity P1 ratio P2 / P1 that is above 0.1 and below 30.

0. The laminated film satisfies the following conditions (I) to (III). (I) The thermal elongation of the laminated film at 130°C is less than 10% in both the MD and TD directions. (II) The total of the maximum peak height Rp and the maximum valley depth Rv obtained by measuring the side surface of the capping layer using a scanning probe microscope is less than 30.0 nm. (III) The amount of the coating layer is 0.10 g / m 2 Above and 0.50g / m 2 the following.

2. The laminated thin film for forming an inorganic thin film layer according to claim 1, characterized in that, The elongation at 100°C of the laminated film is less than 3% in both the MD and TD directions.

3. A laminated thin film, characterized in that, It has an inorganic thin film layer stacked on the cover layer of the laminated film as described in claim 1 or 2.

4. The laminated film according to claim 3, characterized in that, The inorganic thin film layer contains Al and / or Si.

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