Laminated Film

Abstract

A multilayer film which has a coting layer and an inorganic thin film layer on one surface of a base material film, and which is characterized by satisfying the requirements (a) to (f) described below. (a) The base material film contains from 50% by weight to 95% by weight of a polyester resin that is recycled from PET bottles. (b) The surface hardness of the multilayer film in the inorganic thin film layer surface is 120 N / mm2 or less. (c) The coating layer contains, as a constituent, a resin that has an oxazoline group or a carbodiimide group. (d) The content ratio of an isophthalic acid component relative to the total dicarboxylic acid component in the whole polyester resin that constitutes the base material film is from 0.5% by mole to 5.0% by mole. (e) The coefficient of static friction μs and the coefficient of kinetic friction μd of the inorganic thin film layer surface / opposite surface of the multilayer film are within the range of from 0.20 to 0.40. (f) The arithmetic mean roughness Ra in a 2 μm square area of the multilayer film is within the range of from 2.0 to 6.0 nm.

Description

[Technical Field]

[0001] The present invention relates to a laminate film used in the packaging fields of foods, medicines, industrial products, etc. More specifically, the present invention relates to a laminate film having, in this order, an inorganic thin film layer and a protective layer on a base film layer made of polyester resin recycled from PET bottles, and having excellent barrier properties, adhesiveness, and processability. [Background technology]

[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) when it comes to plastic packaging materials for food, pharmaceuticals, etc.

[0003] The performance required for the aforementioned environmentally friendly packaging materials includes being made from recycled materials, having gas barrier properties that can block various gases and extend shelf life, and using materials that have a low environmental impact (for example, not using organic solvents or using small amounts of materials).

[0004] A typical recycled material is polyester resin recycled from PET bottles, and there is a known technology for producing polyester film for body wrap labels that is less prone to static electricity problems without compromising productivity or quality from polyester resin derived from PET bottles, which has a low oligomer content (see, for example, Patent Document 1). Demand for such film applications is expected to expand due to future tightening of environmental regulations.

[0005] On the other hand, in food applications that require blocking various gases such as water vapor and oxygen, gas barrier laminates are generally used, in which a metal thin 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. Among these, those formed with a thin film (inorganic thin film layer) of an inorganic oxide such as silicon oxide, aluminum oxide, or a mixture thereof are widely used because they do not require the use of aluminum foil and are transparent, allowing the contents to be confirmed.

[0006] Regarding the gas barrier films made of the aforementioned recycled materials and inorganic thin films, a laminate film has been proposed that uses polyester resin recycled from PET bottles and has low heat shrinkage and small thickness variations, resulting in a gas barrier laminate film with an inorganic thin film layer and a sealant layer that exhibits good gas barrier properties (e.g., Patent Document 2). However, this conventional technology was insufficient for applications requiring higher barrier performance. Furthermore, there was no discussion of retort resistance or film processability. Furthermore, there was also the problem that the inorganic thin film layer was prone to cracking due to physical damage such as bending, resulting in a decrease in barrier properties.

[0007] As a means of maintaining barrier properties and adhesion even after retort processing, it has been reported that a coating layer made of an oxazoline group-containing water-soluble polymer is provided between a substrate film and an inorganic thin film layer formed, for example, by a vapor deposition method (see, for example, Patent Document 3). Providing a coating layer between a substrate film and an inorganic thin film can be performed continuously during the film formation of the substrate, and is expected to result in greater cost reduction than forming a protective layer on an inorganic thin film. However, with the above configuration, the coating layer itself does not have gas barrier properties, and the contribution to gas barrier properties is largely due to the inorganic thin film layer alone, resulting in a problem of insufficient gas barrier properties. Furthermore, the above conventional technology does not consciously use substrates with low environmental impact, raising concerns about a significant environmental impact.

[0008] Attempts to improve the barrier properties of films composed of inorganic thin films have included providing a protective layer with gas barrier properties on top of the inorganic thin film. Examples include a method in which a water-soluble polymer, an inorganic layered compound, and a metal alkoxide or its hydrolyzate are coated on the inorganic thin film, followed by a sol-gel process to form a composite of the inorganic material containing the inorganic layered compound and the water-soluble polymer on the inorganic thin film. Another example is a laminate in which a metaxylylene group-containing polyurethane is coated on the inorganic thin film (see, for example, Patent Document 4). However, providing a protective layer increases the number of processing steps, raising concerns about increased costs and environmental impact. Furthermore, improving the barrier performance of a protective layer requires a certain film thickness or the use of a special coating material, which also contributes to increased costs and environmental impact. Furthermore, the above-mentioned conventional techniques do not consciously use environmentally friendly substrates, raising concerns about significant environmental impact. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-91862 [Patent Document 2] Patent No. 6500629 [Patent Document 3] Patent No. 5560708 [Patent Document 4] Patent No. 4524463 Summary of the Invention [Problem to be solved by the invention]

[0010] In Patent Document 2, there is room for improvement in the gas barrier properties of the inorganic thin film layer, and retort properties and processability were not considered. In Patent Document 3, there is room for improvement in the gas barrier properties of the inorganic thin film layer, and the environmental impact was not taken into consideration. In Patent Document 4, the environmental impact was not taken into consideration.

[0011] The present invention has been made in light of the problems with the prior art. Specifically, the objective of the present invention is to provide an environmentally friendly laminated film having a base film layer made of polyester resin recycled from PET bottles, a coating layer, and an inorganic thin film layer on top of the base film layer, which has excellent barrier performance, can maintain its barrier properties and adhesiveness even after severe moist heat treatment such as retort sterilization, and has excellent processability. [Means for solving the problem]

[0012] The present inventors have discovered that the barrier properties of an inorganic thin film layer can be improved by controlling the surface hardness of an environmentally friendly substrate film made from polyester resin recycled from PET bottles, and further discovered that the barrier properties and adhesiveness can be maintained even after severe moist heat treatment such as retort treatment by providing a coating layer between the substrate and the inorganic thin film layer, thereby completing the present invention.

[0013] That is, the present invention comprises the following configurations. (1) A laminate film having a coating layer and an inorganic thin film layer on one side of a base film, characterized in that the laminate film satisfies the following requirements (a) to (f): (a) The base film contains 50% by weight or more and 95% by weight or less of polyester resin recycled from PET bottles. (b) The surface hardness of the inorganic thin film layer of the laminated film is 120 N / mm 2 It must be less than or equal to: (c) The coating layer contains a resin having an oxazoline group or a carbodiimide group as a constituent component. (d) The content of isophthalic acid components relative to all dicarboxylic acid components in all polyester resins constituting the base film is 0.5 mol % or more and 5.0 mol % or less. (e) The static friction coefficient μs and the dynamic friction coefficient μd of the inorganic thin film layer surface and the opposite surface of the laminated film are both in the range of 0.20 to 0.40. (f) The arithmetic mean roughness Ra of the laminated film within a 2 μm square is in the range of 2.0 to 6.0 nm. (2) The laminated film according to (1), wherein the inorganic thin film layer is a layer of aluminum oxide or a composite oxide of silicon oxide and aluminum oxide. (3) The laminated film according to (1) or (2), which has a protective layer containing a urethane resin on the inorganic thin film layer. (4) A packaging material comprising the laminate film according to any one of (1) to (3) above, and a sealant layer laminated on one side of the laminate film. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a laminate film using recycled materials, which has an excellent gas barrier property in the inorganic thin film layer and has excellent barrier property and adhesiveness even after severe moist heat treatment such as retort sterilization. Moreover, the laminate film of the present invention has few processing steps and is easy to produce, so it is excellent in both economy and production stability, and it is possible to provide a gas barrier film with uniform properties. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below. [Base film layer] In the present invention, as described below, a preferred embodiment uses recycled polyester resin recovered from PET bottles containing an isophthalic acid component as an acid component as the raw material for the substrate film. Therefore, the substrate film is a mixed resin of recycled polyester resin and virgin raw material, i.e., non-recycled resin, and the intrinsic viscosity of the resin constituting the film refers to the value obtained by measuring the intrinsic viscosity of the mixed resin constituting the film. The lower limit of the intrinsic viscosity of the resin constituting the film, as measured by the substrate film, is preferably 0.58 dL / g, more preferably 0.60 dL / g. If the intrinsic viscosity is less than 0.58 dL / g, many recycled resins from PET bottles have an intrinsic viscosity exceeding 0.68 dL / g. Reducing the viscosity when using such recycled resins to produce a film can result in thickness unevenness, which is undesirable. Furthermore, the film can become discolored, which is undesirable. The upper limit is preferably 0.70 dL / g, more preferably 0.68 dL / g. If the viscosity exceeds 0.70 dL / g, the resin becomes difficult to extrude from the extruder, which can reduce productivity, which is undesirable.

[0016] The lower limit of the thickness of the substrate film is preferably 8 μm, more preferably 10 μm, and even more preferably 12 μm. If it is less than 8 μm, the strength of the film may be insufficient, which is undesirable. The upper limit is preferably 200 μm, more preferably 50 μm, and even more preferably 30 μm. If it exceeds 200 μm, the film may become too thick and processing may become difficult. In addition, an increased film thickness is undesirable in terms of environmental impact, so it is preferable to reduce the volume as much as possible.

[0017] The lower limit of the refractive index in the thickness direction of the substrate film is preferably 1.4930, more preferably 1.4940. If it is less than 1.4930, the orientation may be insufficient, and the laminate strength may not be obtained. The upper limit is preferably 1.4995, more preferably 1.4980. If it exceeds 1.4995, the surface orientation may be disrupted, and the mechanical properties may be insufficient, which is not preferable.

[0018] The lower limit of the heat shrinkage rate of the base film in the machine direction (sometimes referred to as MD) and the transverse direction (sometimes referred to as TD) when treated at 150°C for 30 minutes is preferably 0.1%, more preferably 0.3%. If it is less than 0.1%, the improvement effect will saturate and the film may become mechanically brittle, which is not preferable. The upper limit is preferably 3.0%, more preferably 2.5%. If it exceeds 3.0%, dimensional changes during processing such as printing may cause pitch deviation, which is not preferable. Furthermore, if it exceeds 3.0%, dimensional changes during processing such as printing may cause shrinkage in the width direction, which is not preferable.

[0019] As a raw material for the substrate film, it is preferable to use recycled polyester resin made from PET bottles containing an isophthalic acid component as an acid component. The crystallinity of the polyester used in PET bottles is controlled to improve the bottle's appearance, and as a result, polyesters containing 10 mol% or less of isophthalic acid are sometimes used. The inclusion of isophthalic acid disrupts the crystalline structure of the polyester, contributing to the flexibility of the substrate, and controlling this can create a surface that is easy to laminate an inorganic thin film on.

[0020] The lower limit of the amount of terephthalic acid component of all dicarboxylic acid components constituting the polyester resin contained in the base film is preferably 95.0 mol%, more preferably 96.0 mol%, even more preferably 96.5 mol%, and particularly preferably 97.0 mol%. A content of less than 95.0 mol% is not preferred because crystallinity decreases and the heat shrinkage rate may increase. Furthermore, the upper limit of the amount of terephthalic acid component of the polyester resin contained in the film is preferably 99.5 mol%, more preferably 99.0 mol%. Since recycled polyester resins made from PET bottles often contain dicarboxylic acid components other than terephthalic acid, such as isophthalic acid, it is not preferred for the terephthalic acid component constituting the polyester resin in the film to exceed 99.5 mol%, as this makes it difficult to produce polyester films with a high proportion of recycled resin.

[0021] In the present invention, controlling the amount of isophthalic acid relative to the total dicarboxylic acid components constituting the polyester resin contained in the base film is important for imparting flexibility to achieve barrier performance. The lower limit is preferably 0.5 mol%, more preferably 0.7 mol%, even more preferably 0.9 mol%, and particularly preferably 1.0 mol%. Some recycled polyester resins made from PET bottles contain a large amount of isophthalic acid. Therefore, it is not desirable for the isophthalic acid component constituting the polyester resin in the film to be less than 0.5 mol%, as this makes it difficult to produce a polyester film with a high recycled resin content. Furthermore, the surface flexibility may decrease, making the inorganic thin film layer more susceptible to stress loads during lamination, potentially resulting in a deterioration in barrier performance. The upper limit of the amount of isophthalic acid relative to the total dicarboxylic acid components constituting the polyester resin contained in the film is preferably 5.0 mol%, more preferably 4.0 mol%, even more preferably 3.5 mol%, and particularly preferably 3.0 mol%. A content exceeding 5.0 mol% is not desirable because it reduces crystallinity and may increase the heat shrinkage rate. Furthermore, if the substrate becomes too soft, the inorganic thin film may not be able to keep up with the changes, which may result in a deterioration in barrier performance. By setting the content of the isophthalic acid component within the above range, the softening effect on the substrate surface makes it easier for the inorganic thin film layer to deposit, and as a result, good barrier properties can be achieved.

[0022] The upper limit of the intrinsic viscosity of the recycled resin from PET bottles is preferably 0.90 dL / g, more preferably 0.80 dL / g, even more preferably 0.77 dL / g, and particularly preferably 0.75 dL / g. If the intrinsic viscosity exceeds 0.9 dL / g, the resin becomes difficult to extrude from the extruder, which may reduce productivity, and is therefore not preferred.

[0023] The lower limit of the content of polyester resin recycled from PET bottles in the film is preferably 50% by weight, more preferably 65% ​​by weight, and even more preferably 75% by weight. A content of less than 50% by weight results in a low content of recycled resin, which is undesirable in terms of contributing to environmental protection. Furthermore, the amount of isophthalic acid component decreases, which may prevent the development of the flexibility advantageous for laminating inorganic thin film layers. On the other hand, the upper limit of the content of polyester resin recycled from PET bottles is preferably 95% by weight, more preferably 90% by weight, and even more preferably 85% by weight. A content exceeding 95% by weight is undesirable because it may be difficult to sufficiently add lubricants or additives such as inorganic particles to improve the film's functionality. Polyester resin recycled from PET bottles can also be used as a masterbatch (high-concentration resin) to add lubricants or additives such as inorganic particles to improve the film's functionality.

[0024] As the lubricant type, inorganic lubricants such as silica, calcium carbonate, and alumina are preferred, as well as organic lubricants, with silica and calcium carbonate being more preferred. These can provide transparency and lubricity. The average particle size of the lubricant particles is preferably within the range of 0.05 to 3.0 μm when measured with a Coulter counter.

[0025] The lower limit of the lubricant content in the base film is preferably 0.01% by weight, more preferably 0.015% by weight, and even more preferably 0.02% by weight. If it is less than 0.01% by weight, the lubricating properties may decrease. The upper limit is preferably 1% by weight, more preferably 0.2% by weight, and even more preferably 0.1% by weight. If it exceeds 1% by weight, the transparency may decrease, which is not preferable.

[0026] While the manufacturing method of the substrate film used in the laminate film of the present invention is not particularly limited, the following manufacturing method is recommended. The temperature setting for melting and extruding the resin in the extruder is important. The basic concept is (1) to suppress degradation by extruding at as low a temperature as possible since the polyester resin used in PET bottles contains an isophthalic acid component, while (2) to melt the intrinsic viscosity and fine highly crystalline portions sufficiently and uniformly, it is necessary to provide a portion that can be melted at high temperature or high pressure. The inclusion of an isophthalic acid component reduces the stereoregularity of the polyester, leading to a lower melting point. Therefore, extrusion at high temperatures can significantly reduce or degrade the melt viscosity due to heat, resulting in reduced mechanical strength and an increase in the amount of degraded foreign matter. Furthermore, simply lowering the extrusion temperature may not achieve sufficient melt-kneading, resulting in increased thickness unevenness and foreign matter such as fisheyes. Based on the above, recommended manufacturing methods include, for example, using two extruders in tandem, increasing the pressure in the filter section, and using a screw with high shear force as part of the screw configuration.

[0027] The lower limit of the set temperature in the resin melting section in the extruder (excluding the highest set temperature in the compression section of the screw in the extruder) is preferably 270° C., and the upper limit is preferably 290° C. If the temperature is below 270° C., extrusion is difficult, and if the temperature is above 290° C., resin deterioration may occur, which is not preferable. The lower limit of the maximum set temperature of the compression section of the screw in the extruder is preferably 295°C. Polyester resins used in PET bottles often contain high-melting-point crystals (260°C to 290°C) for transparency reasons. Furthermore, additives and crystallization nucleating agents are added, which can cause variations in the fine melting behavior within the resin material. Temperatures below 295°C are not preferred, as it becomes difficult to sufficiently melt them. The upper limit of the maximum set temperature of the compression section of the screw in the extruder is preferably 310°C. Temperatures above 310°C can cause resin degradation, which is not preferred.

[0028] The lower limit of the time for the resin to pass through the highest set temperature zone of the compression section of the screw in the extruder is preferably 10 seconds, more preferably 15 seconds. If it is less than 10 seconds, the polyester resin used in the PET bottle will not be sufficiently melted, which is not preferred. The upper limit is preferably 60 seconds, more preferably 50 seconds. If it exceeds 60 seconds, the resin is more likely to deteriorate, which is not preferred. By setting the extruder within this range, it is possible to obtain a film with little thickness unevenness, foreign matter such as fisheyes, and coloration, while using a large amount of polyester resin recycled from PET bottles.

[0029] The molten resin is extruded onto a cooling roll in the form of a sheet and then biaxially stretched. Although simultaneous biaxial stretching may be used as the stretching method, sequential biaxial stretching is particularly preferred. This method makes it easier to achieve both the productivity and the quality required for the present invention.

[0030] In the present invention, the film stretching method is not particularly limited, but the following points are important. When stretching a resin having an intrinsic viscosity of 0.58 dl / g or more and containing an isophthalic acid component, the stretching ratio and temperature in the machine direction (MD) and transverse direction (TD) are important. If the MD stretching ratio and temperature are inappropriate, the stretching force will not be applied uniformly, resulting in insufficient molecular orientation, which may increase thickness unevenness and insufficient mechanical properties. Furthermore, in the subsequent TD stretching step, the film may break or experience extreme thickness unevenness. If the TD stretching ratio and temperature are inappropriate, the film may not be stretched uniformly, resulting in poor balance between the machine and transverse orientations and insufficient mechanical properties. Furthermore, if the film proceeds to the subsequent heat setting step with significant thickness unevenness or insufficient molecular chain orientation, uniform relaxation will not be achieved, leading to further thickness unevenness and insufficient mechanical properties. Therefore, it is basically recommended that in MD stretching, the temperature be controlled as described below to perform stretching in stages, and in TD stretching, stretching be performed at an appropriate temperature so as not to significantly impair the orientation balance. Although not limited to the following embodiment, an example will be described.

[0031] As a method for stretching in the machine direction (MD), a roll stretching method or an IR heating method is preferred.

[0032] The lower limit of the MD stretching temperature is preferably 100°C, more preferably 110°C, and even more preferably 120°C. If the temperature is less than 100°C, even if a polyester resin with an intrinsic viscosity of 0.58 dl / g or more is stretched and molecularly oriented in the machine direction, the film may break or have extremely poor thickness in the subsequent transverse stretching step, which is not preferred. The upper limit is preferably 140°C, more preferably 135°C, and even more preferably 130°C. If the temperature exceeds 140°C, the molecular chain orientation may be insufficient, resulting in insufficient mechanical properties, which is not preferred.

[0033] The lower limit of the MD stretching ratio is preferably 2.5 times, more preferably 3.5 times, and even more preferably 4 times. If it is less than 2.5 times, even if a polyester resin with an intrinsic viscosity of 0.58 dl / g or more is stretched and molecularly oriented in the machine direction, film breakage or extreme thickness defects may occur in the subsequent transverse stretching step, which is not very preferable. The upper limit is preferably 5 times, more preferably 4.8 times, and even more preferably 4.5 times. If it exceeds 5 times, the effects of improving mechanical strength and thickness unevenness may saturate, making it less meaningful.

[0034] Although the MD stretching method may be the single-stage stretching described above, it is more preferable to divide the stretching into two or more stages, which allows for good stretching of polyester resins made from recycled resins containing isophthalic acid, which have a high intrinsic viscosity, and improves thickness unevenness, laminate strength, mechanical properties, etc.

[0035] The lower limit of the first-stage MD stretching temperature is preferably 110°C, more preferably 115°C. If the temperature is lower than 110°C, the film will not be sufficiently longitudinally stretched, resulting in poor flatness, which is undesirable. The upper limit of the first-stage MD stretching temperature is preferably 125°C, more preferably 120°C. If the temperature exceeds 125°C, the molecular chain orientation will be insufficient, which may result in a decrease in mechanical properties, which is undesirable.

[0036] The lower limit of the first-stage MD stretching ratio is preferably 1.1 times, more preferably 1.3 times. By using weak stretching in the first stage at 1.1 times or more, a polyester resin having an intrinsic viscosity of 0.58 dl / g or more can be finally stretched longitudinally sufficiently, thereby increasing productivity. The upper limit of the first-stage MD stretching ratio is preferably 2 times, more preferably 1.6 times. A ratio exceeding 2 times is not preferred because the orientation of molecular chains in the longitudinal direction becomes too high, making it difficult to stretch in the second and subsequent stages or resulting in a film with poor thickness unevenness.

[0037] The lower limit of the MD stretching temperature in the preferred second stage (or final stage) is preferably 110°C, more preferably 115°C. At 110°C or higher, polyester resins with an intrinsic viscosity of 0.58 dl / g or higher can be sufficiently stretched longitudinally, making transverse stretching possible in the next step, and improving thickness unevenness in the longitudinal and transverse directions. The upper limit is preferably 130°C, more preferably 125°C. Temperatures above 130°C are not preferred because crystallization is promoted, making transverse stretching difficult or increasing thickness unevenness.

[0038] The lower limit of the preferred second-stage (or final-stage) MD stretching ratio is preferably 2.1 times, more preferably 2.5 times. If it is less than 2.1 times, even if a polyester resin with an intrinsic viscosity of 0.58 dl / g or more is stretched and molecularly oriented in the machine direction, film breakage or extreme thickness defects may occur in the subsequent transverse stretching step, which is not preferred. The upper limit is preferably 3.5 times, more preferably 3.1 times. If it exceeds 3.5 times, the machine orientation becomes too high, making it impossible to stretch in the second or subsequent stages, or the resulting film may have significant thickness unevenness, which is not preferred.

[0039] The lower limit of the TD stretching temperature is preferably 110°C, more preferably 120°C, and even more preferably 125°C. If the temperature is less than 110°C, the stretching stress in the transverse direction increases, which may cause the film to break or the thickness unevenness to become extremely large, and this is not preferred. The upper limit is preferably 150°C, more preferably 145°C, and even more preferably 140°C. If the temperature exceeds 150°C, the orientation of the molecular chains does not increase, which may cause a decrease in mechanical properties, and this is not preferred.

[0040] The lower limit of the transverse direction (TD) stretching ratio is preferably 3.5 times, more preferably 3.9 times. If it is less than 3.5 times, the molecular orientation may be weak and the mechanical strength may be insufficient, which is not preferable. In addition, the orientation of the molecular chains in the machine direction is high, which results in a poor balance between the machine and machine directions, resulting in large thickness variations, which is not preferable. The upper limit is preferably 5.5 times, more preferably 4.5 times. If it exceeds 5.5 times, it may break, which is not preferable.

[0041] To obtain a substrate film for use in the laminate film of the present invention, it is desirable to appropriately set the conditions for heat setting in the tenter following TD stretching and for cooling the film to room temperature. Polyester films containing recycled resins from PET bottles containing isophthalic acid have lower crystallinity, are more susceptible to micro-melting, and have lower mechanical strength than conventional polyethylene terephthalate films that do not contain isophthalic acid. Therefore, if the film is suddenly exposed to high temperatures under tension after stretching or if it is suddenly cooled under tension after high-temperature heat setting, the inevitable temperature difference across the film's width disrupts the tension balance in the width direction, resulting in thickness unevenness and poor mechanical properties. On the other hand, attempting to address this phenomenon by lowering the heat setting temperature may result in insufficient laminate strength. In the present invention, it is recommended that the film be subjected to heat setting 1 at a slightly lower temperature, heat setting 2 at a sufficiently higher temperature (or heat setting 3, if necessary), followed by a slow cooling step to cool the film to room temperature. However, this method is not limited to this, and examples thereof include a method of controlling the film tension in accordance with the hot air speed in the tenter and the temperature of each zone, a method of performing heat treatment at a relatively low temperature in an oven with a sufficient length after stretching, and a method of relaxing the film with a heated roll after heat setting.

[0042] As an example, a method of controlling the temperature of a tenter is shown below: Heat fixation zones 1, 2, and 3 are arranged in this order from the upstream side in the film flow direction in the heat fixation zone of the tenter.

[0043] The lower limit of the temperature for heat setting 1 is preferably 160°C, more preferably 170°C. Temperatures below 160°C are not preferred because the final heat shrinkage rate is large, which can lead to misalignment or shrinkage during processing. The upper limit is preferably 215°C, more preferably 210°C. Temperatures above 215°C are not preferred because the film is suddenly exposed to high temperatures, which can lead to thickness variations or breakage.

[0044] The lower limit of the heat setting time 1 is preferably 0.5 seconds, more preferably 2 seconds. If it is less than 0.5 seconds, the film temperature may not rise sufficiently. The upper limit is preferably 10 seconds, more preferably 8 seconds. If it exceeds 10 seconds, productivity may decrease, which is not preferable.

[0045] The lower limit of the temperature for heat setting 2 is preferably 220°C, more preferably 227°C. Temperatures below 220°C are undesirable because the thermal shrinkage rate increases, which can lead to misalignment or shrinkage during processing. The upper limit is preferably 240°C, more preferably 237°C. Temperatures above 240°C are undesirable because the film may melt or, even if it does not melt, it may become brittle.

[0046] The lower limit of the time for heat setting 2 is preferably 0.5 seconds, more preferably 3 seconds. If it is less than 0.5 seconds, breakage may occur during heat setting, which is not preferable. The upper limit is preferably 10 seconds, more preferably 8 seconds. If it exceeds 10 seconds, sagging may occur, resulting in thickness unevenness, which is not preferable.

[0047] If necessary, the lower limit of the temperature for heat setting 3 is preferably 205°C, more preferably 220°C. If the temperature is less than 205°C, the heat shrinkage rate increases, which may cause misalignment or shrinkage during processing, and is therefore not preferred. The upper limit is preferably 240°C, more preferably 237°C. If the temperature exceeds 240°C, the film may melt, or even if it does not melt, it may become brittle, which is also not preferred.

[0048] If necessary, the lower limit of the time for heat setting 3 is preferably 0.5 seconds, more preferably 3 seconds. If it is less than 0.5 seconds, breakage may occur easily during heat setting, which is not preferable. The upper limit is preferably 10 seconds, more preferably 8 seconds. If it exceeds 10 seconds, sagging may occur, resulting in thickness unevenness, which is not preferable.

[0049] TD relaxation can be performed at any point during heat setting. The lower limit is preferably 0.5%, more preferably 3%. If it is less than 0.5%, the thermal shrinkage rate, particularly in the lateral direction, becomes large, which may result in misalignment or shrinkage during processing, which is not preferred. The upper limit is preferably 10%, more preferably 8%. If it exceeds 10%, sagging may occur, which may result in thickness unevenness, which is not preferred.

[0050] The lower limit of the annealing temperature after TD heat setting is preferably 90°C, more preferably 100°C. If the temperature is less than 90°C, the film contains isophthalic acid, and therefore, shrinkage due to a sudden temperature change may cause thickness unevenness or breakage, which is not preferred. The upper limit of the annealing temperature is preferably 150°C, more preferably 140°C. If the temperature exceeds 150°C, a sufficient cooling effect may not be obtained, which is not preferred.

[0051] The lower limit of the annealing time after heat setting is preferably 2 seconds, more preferably 4 seconds. If it is less than 2 seconds, sufficient annealing effect may not be obtained, which is not preferable. The upper limit is preferably 20 seconds, more preferably 15 seconds. If it exceeds 20 seconds, it is likely to be disadvantageous in terms of productivity, which is not preferable.

[0052] The upper limit of the haze per thickness of the base film layer in the present invention is preferably 0.66% / μm, more preferably 0.60% / μm, and even more preferably 0.53% / μm. When printing is performed on a base film layer having a haze of 0.66% / μm or less, the quality of the printed characters and images is improved.

[0053] Furthermore, the base film layer in the present invention may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, or surface roughening treatment, and may also be subjected to known anchor coating treatment, printing, decoration, etc., as long as the object of the present invention is not impaired.

[0054] Furthermore, a layer of another material may be laminated on the base film layer of the present invention, and as a method for this, the layer may be laminated after the base film layer is produced, or during film formation.

[0055] [Inorganic thin film layer] The gas barrier laminate film of the present invention has an inorganic thin film layer on the surface of the base film layer. The inorganic thin film layer is a thin film made of a metal or 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 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 relative to the mass of the metal. 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, if the Al concentration is 100% by mass, the water vapor barrier performance is good, but the surface tends to be smooth due to the use of a single material, resulting in poor slipperiness and the likelihood of processing defects (wrinkles, acne, etc.). The silicon oxide referred to here is a variety of silicon oxides such as SiO and SiO2, or a mixture thereof, and the aluminum oxide is a variety of aluminum oxides such as AlO and Al2O3, or a mixture thereof.

[0056] The inorganic thin film layer has a thickness of 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.

[0057] The method for forming the inorganic thin film layer is not particularly limited, and any known deposition method, such as physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD), may be appropriately employed. A typical method for forming an 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, a mixture of SiO2 and Al2O3 or a mixture of SiO2 and Al is preferably used as the deposition source. These deposition sources are typically particles, and the particle size is preferably large enough to prevent pressure changes during deposition, with a preferred particle diameter of 1 mm to 5 mm. Heating methods include resistance heating, high-frequency induction heating, electron beam heating, and laser heating. Reactive deposition can also be employed, using reactive gases such as oxygen, nitrogen, hydrogen, argon, carbon dioxide, and water vapor, or by adding ozone or ion-assisted deposition. Furthermore, the deposition conditions can be freely modified by applying a bias to the deposition target (the laminated film to be deposited) or by heating or cooling the deposition target. The deposition material, reactive gas, bias of the deposition target, heating / cooling, etc. can be changed in the same way when the sputtering method or the CVD method is adopted.

[0058] In the present invention, the surface hardness (flexibility) is controlled by the content of isophthalic acid in the substrate film. By controlling the surface hardness within a predetermined range, the flexibility facilitates deposition of an inorganic thin film layer on the substrate, resulting in a coating film with excellent barrier properties. The surface hardness is 60 to 120 N / mm 2 The surface hardness is preferably 65 N / mm 2 More preferably, 70N / mm 2 More than 75N / mm 2 More preferably, it is 115N / mm 2 or less, more preferably 110 N / mm 2 Below 105 N / mm, particularly preferably 2 The surface hardness of the laminated film is 120N / mm 2If the surface hardness exceeds 60 N / mm, the flexibility of the surface will decrease, and the inorganic thin film layer will be susceptible to stress load when laminating the inorganic thin film layer, which may result in a deterioration in barrier performance. 2 If the thickness is less than 1000 nm, the inorganic thin film may become too soft and be unable to follow the change, resulting in a deterioration in barrier performance. This is also undesirable from the viewpoint of processability, which will be described later.

[0059] [Coating layer] The laminate film of the present invention may have a coating layer between the substrate film layer and the inorganic thin film layer to ensure gas barrier properties and laminate strength after retort treatment, as well as slippage for improved processability. Resin compositions used for the coating layer between the substrate film layer and the inorganic thin film layer include resins such as urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, and polybutadiene-based resins to which curing agents such as epoxy-based, isocyanate-based, melamine-based, oxazoline-based, and carbodiimide-based curing agents have been added. The resin compositions used for these coating layers preferably contain a silane coupling agent having at least one organic functional group. Examples of the organic functional group include an alkoxy group, an amino group, an epoxy group, and an isocyanate group. The addition of the silane coupling agent further improves the laminate strength after retort treatment.

[0060] Among the resin compositions used for the coating layer, it is preferable to use a resin containing an oxazoline group or a carbodiimide group, and it is more preferable to use a mixture of an acrylic resin and a urethane resin in addition to these. These functional groups have high affinity with inorganic thin films and can react with oxygen-deficient portions of inorganic oxides or metal hydroxides generated during the formation of the inorganic thin film layer, thereby exhibiting strong adhesion to the inorganic thin film layer. Furthermore, unreacted functional groups present in the coating layer can react with carboxylic acid terminals generated by hydrolysis of the base film layer and the coating layer to form crosslinks.

[0061] In the present invention, the coating weight of the coating layer is 0.010 to 0.200 (g / m 2) is preferable. This allows the coating layer to be controlled uniformly, resulting in dense deposition of the inorganic thin film layer. In addition, the cohesive force within the coating layer is improved, and the adhesion between the substrate film, coating layer, and inorganic thin film layer is also increased, thereby improving the water-resistant adhesion of the coating layer. The coating layer preferably has a deposition weight of 0.015 (g / m 2 ) or more, more preferably 0.020 (g / m 2 ) or more, more preferably 0.025 (g / m 2 ) or more, and preferably 0.190 (g / m 2 ) or less, more preferably 0.180 (g / m 2 ) or less, more preferably 0.170 (g / m 2 ) or less. The coating layer adhesion weight is 0.200 (g / m 2 ), the cohesive force inside the coating layer becomes insufficient, and good adhesion may not be achieved. In addition, the uniformity of the coating layer also decreases, which may cause defects in the inorganic thin film layer and reduce the gas barrier properties. Furthermore, if the coating layer is too thick, the flexibility effect of the substrate is reduced, leading to a deterioration in the gas barrier properties. Moreover, the manufacturing cost increases, which is economically disadvantageous. On the other hand, if the coating layer thickness is more than 0.010 (g / m 2 If the thickness is less than 1 / 2 mm, the substrate cannot be sufficiently covered, and there is a risk that sufficient gas barrier properties and interlayer adhesion cannot be obtained.

[0062] The method for forming the coating layer is not particularly limited, and conventionally known methods such as coating methods can be used. Among coating methods, offline coating and in-line coating are preferred. For example, in the case of in-line coating, which is performed in the process of producing a base film layer, the conditions for drying and heat treatment during coating depend on the coating thickness and the conditions of the equipment, but it is preferable to feed the film to a stretching process in the perpendicular direction immediately after coating and dry it in a preheating zone or stretching zone of the stretching process. In such cases, it is usually preferable to use a temperature of about 50 to 250°C. Examples of the solvent to be used when using the coating method include aromatic solvents such as benzene and toluene; alcohol solvents such as methanol and ethanol; ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as ethyl acetate and butyl acetate; and polyhydric alcohol derivatives such as ethylene glycol monomethyl ether.

[0063] In the present invention, the surface hardness (flexibility) is controlled by the content of isophthalic acid in the substrate film. By controlling the surface hardness within a predetermined range, the flexibility facilitates penetration and deposition of the coating layer on the substrate, resulting in a uniform coating film. The surface hardness of the coating layer side of the film in which the coating layer is laminated on the substrate film is 120 N / mm 2 The surface hardness is preferably 115 N / mm2 or less, more preferably 110 N / mm2 or less. 2 or less, more preferably 105 N / mm 2 The surface hardness of the laminated film is 120N / mm 2 If the hardness exceeds 60 N / mm, the flexibility of the surface will decrease and it will be difficult to obtain the penetration effect of the coating layer. 2 is preferred, and 65N / mm 2 is more preferable, and 70N / mm 2 is more preferable, and 75N / mm 2 In the case of a laminated film in which an inorganic thin film layer, which will be described later, is further laminated on the coating layer, the preferred range of the surface hardness on the inorganic thin film layer side is the same as the above range.

[0064] As mentioned above, reducing the surface hardness can be expected to improve barrier performance, but there is a concern that slipperiness may also be impaired. Poor slipperiness can lead to problems such as wrinkles during vapor deposition or winding up during coating and lamination processes, or even small convex defects (pimples) caused by the film getting caught during winding, or blocking. In the present invention, controlling the surface roughness of the laminated film can impart appropriate slipperiness to the substrate surface while maintaining the flexibility of the substrate, resulting in a film with excellent processability. The surface roughness of the film is preferably 2.0 to 6.0 nm in terms of average roughness Ra in a 2-μm square observation area using an atomic force microscope (AFM). This imparts minute irregularities to the surface, resulting in excellent slipperiness. The roughness is preferably 2.5 to 5.5 nm, more preferably 3.0 to 5.0 nm, and even more preferably 3.5 to 4.5 nm. If the roughness exceeds 6 nm, the inorganic thin film layer may not be uniformly laminated due to the irregularities, resulting in reduced gas barrier properties. On the other hand, if the roughness is less than 2 nm, the surface is flat and therefore the slipperiness deteriorates.

[0065] Methods for adjusting the surface roughness within the above range include providing a coating layer or surface treatment such as corona treatment. Among these, providing a coating layer is preferred from the viewpoint of simultaneously providing water-resistant adhesion and slipperiness. The roughness of the coating layer can be adjusted by changing the mixing ratio of two or more materials to change the dispersibility of the resin, by changing the amount of the coating layer applied, or by changing the solvent used for dilution when preparing the coating solution.

[0066] The static friction coefficient μs and dynamic friction coefficient μd of the inorganic thin film layer surface / coating layer surface of the laminate film of the present invention are preferably in the range of 0.20 to 0.40, more preferably 0.275 to 0.375, and even more preferably 0.30 to 0.35. If the slippage of the laminate film exceeds 0.40, wrinkles may occur during film winding, which may cause acne. On the other hand, if the slippage is less than 0.20, the film may slip upward, causing shear during winding.

[0067] [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 metal oxide layer is not a completely dense film, but has minute defects scattered throughout. By forming a protective layer by coating a specific protective layer resin composition (described below) on the metal oxide layer, the resin in the protective layer resin composition penetrates into the defects in the metal oxide layer, resulting in stable gas barrier properties. In addition, using a material with gas barrier properties for the protective layer itself significantly improves the gas barrier performance of the laminate film. However, it should be noted that providing a protective layer increases costs due to the additional steps and may also have an environmental impact depending on the materials used. It should also be noted that the protective layer may change the surface roughness described above.

[0068] The protective layer adhesion amount is 0.10 to 0.40 (g / m 2 ) is preferable. 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 coating weight of the protective layer is preferably 0.13 (g / m 2 ) or more, more preferably 0.16 (g / m 2 ) or more, more preferably 0.19 (g / m 2 ) or more, and preferably 0.37 (g / m 2 ) or less, more preferably 0.34 (g / m 2 ) or less, more preferably 0.31 (g / m 2 ) or less. The protective layer adhesion is 0.400 (g / m 2 ), the gas barrier properties improve, but the cohesive force inside the protective layer becomes insufficient and the uniformity of the protective layer also decreases, which can result in unevenness or defects in the coat appearance and insufficient gas barrier properties and adhesiveness. On the other hand, if the thickness of the protective layer is more than 0.10 (g / m 2 If the thickness is less than 1 / 2 mm, sufficient gas barrier properties and interlayer adhesion may not be obtained.

[0069] 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 obtained by adding a curing agent such as an epoxy-based, isocyanate-based, or melamine-based to a resin such as a urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, or polybutadiene-based resin. In particular, the inclusion of a urethane resin is preferred because, in addition to the barrier performance due to the high cohesiveness of the urethane bond itself, the polar groups interact with the inorganic thin film layer and the presence of amorphous portions provides flexibility, thereby suppressing damage to the inorganic thin film layer even when a bending load is applied.

[0070] (urethane resin) From the viewpoint of improving barrier properties through cohesion, the urethane resin used in the present invention preferably has a glass transition temperature (Tg) of 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. However, in order to develop adhesive strength, a soft resin with excellent flexibility and a Tg of 100°C or lower may be mixed in. In this case, the addition ratio of the soft resin is preferably within the range of 0 to 80%, more preferably within the range of 10 to 70%, and even more preferably within the range of 20 to 60%. When the addition ratio is within the above range, cohesion and flexibility can be achieved at the same time, resulting in good barrier properties and adhesiveness. However, if the addition ratio exceeds 80%, the film may become too soft, which may lead to a decrease in barrier performance.

[0071] From the viewpoint of improving gas barrier properties, it is more preferable to use a urethane resin containing an aromatic or araliphatic diisocyanate component as a main constituent component. Among these, it is particularly preferable to contain a metaxylylene diisocyanate component. By using the above resin, the cohesive strength of the urethane bond can be further increased due to the stacking effect between aromatic rings, resulting in good gas barrier properties.

[0072] In the present invention, the proportion of aromatic or araliphatic diisocyanate in the urethane resin is preferably 50 mol% or more (50 to 100 mol%) based on 100 mol% of the polyisocyanate component (F). The total proportion of aromatic or araliphatic diisocyanate is preferably 60 to 100 mol%, more preferably 70 to 100 mol%, and even more preferably 80 to 100 mol%. The "Takelac (registered trademark) WPB" series, commercially available from Mitsui Chemicals, Inc., can be used as such a resin. If the total proportion of aromatic or araliphatic diisocyanate is less than 50 mol%, good gas barrier properties may not be obtained.

[0073] The urethane resin used in the present invention may be blended with various crosslinking agents (silicon-based crosslinking agents) to improve the cohesive strength and moist heat-resistant adhesion of the film, as long as the gas barrier properties are not impaired. Examples of crosslinking agents include silicon-based crosslinking agents, oxazoline compounds, carbodiimide compounds, and epoxy compounds. Among these, blending a silicon-based crosslinking agent can particularly improve water-resistant adhesion to the inorganic thin film layer. From this viewpoint, silicon-based crosslinking agents are particularly preferred. Other crosslinking agents such as oxazoline compounds, carbodiimide compounds, and epoxy compounds may also be used in combination.

[0074] 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.

[0075] When forming a protective layer, it is preferable to apply a protective layer resin composition and then heat-dry it. The drying temperature is preferably 110 to 190°C, more preferably 130 to 185°C, and even more preferably 150 to 180°C. Drying temperatures below 110°C can result in insufficient drying of the protective layer, or in a slow progress in film formation of the protective layer, resulting in reduced cohesive strength and water-resistant adhesion, and consequently reduced barrier properties and hand-tearability. On the other hand, drying temperatures above 190°C can result in excessive heat being applied to the film, making it brittle and reducing puncture strength, or shrinking and impairing processability. Drying at 150°C or higher, preferably 160°C or higher, can effectively promote film formation of the protective layer, increasing the adhesive area between the resin of the protective layer and the inorganic thin film layer and improving water-resistant adhesion. It is particularly preferable to first volatilize the solvent at a relatively low temperature of 90 to 110°C immediately after application, and then dry at 150°C or higher, as this results in a uniform film. In addition to drying, additional heat treatment at a temperature as low as possible is also effective in accelerating the formation of the protective layer.

[0076] As described above, the laminated film of the present invention has the characteristic of having excellent gas barrier performance before treatment by using a polyester resin derived from PET bottles that contains isophthalic acid and has a low environmental impact as the substrate, and by providing a coating layer, it can maintain its barrier properties and adhesion to the inorganic thin film layer even after severe wet heat treatment.

[0077] [Packaging materials] When the laminated film of the present invention is used as a packaging material, it is preferable to form a laminate having a heat-sealable resin layer called a sealant. The heat-sealable resin layer is usually provided on an inorganic thin film layer, but it may also be provided on the outside of the base film layer (the surface opposite to the surface on which the coating layer is formed). The heat-sealable resin layer is usually formed by extrusion lamination or dry lamination. The thermoplastic polymer forming the heat-sealable resin layer may be any polymer that can exhibit sufficient sealant adhesiveness, and examples of such polymers include polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resins, ethylene-vinyl acetate copolymers, ethylene-α-olefin random copolymers, and ionomer resins.

[0078] [Adhesive layer] The adhesive layer used in the present invention can be a general-purpose laminating adhesive. For example, solvent-free, aqueous, or hot-melt adhesives based on poly(ester)urethane, polyester, polyamide, epoxy, poly(meth)acrylic, polyethyleneimine, ethylene-(meth)acrylic acid, polyvinyl acetate, (modified) polyolefin, polybutadiene, wax, or casein can be used. Among these, urethane or polyester adhesives are preferred in terms of their moist heat resistance that can withstand retort treatment and their flexibility that can adapt to dimensional changes in each substrate. The adhesive layer can be applied by, for example, direct gravure coating, reverse gravure coating, kiss coating, die coating, roll coating, dip coating, knife coating, spray coating, fountain coating, or other methods. To achieve sufficient adhesion after retort, a coating weight of 1 to 8 g / m2 after drying is required. 2 More preferably, it is 2 to 7 g / m 2 , and more preferably 3 to 6 g / m 2 The coating amount is 1g / m 2 If it is less than 8 g / m, it will be difficult to bond the entire surface, and the adhesive strength will decrease. 2 If the amount exceeds this, it takes a long time for the film to completely cure, unreacted material is likely to remain, and adhesive strength decreases.

[0079] Furthermore, the laminate film of the present invention may have at least one printed layer or other plastic substrate and / or paper substrate layer laminated between or on the outside of the inorganic thin film layer or substrate film layer and the heat-sealable resin layer.

[0080] 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.

[0081] The laminate of the present invention has an oxygen permeability of 15 ml / m under conditions of 23°C x 65% RH both before and after retort treatment. 2 In order to achieve good gas barrier properties, it is preferable that the viscosity is 12.5 ml / m or less. 2 ·d·MPa or less, preferably 10ml / m 2 ·d·MPa or less. Oxygen permeability is 15ml / m 2 If the gas barrier strength exceeds 1.5 MPa, it will be difficult to use in applications that require high gas barrier properties. 2 If the oxygen permeability is less than 1 ml / m, the barrier performance will be excellent, but the residual solvent will not easily permeate to the outside of the bag, which is undesirable as it may result in a relatively increased amount of migration to the contents. 2 ·d·MPa or more.

[0082] The laminate of the present invention has a water vapor permeability of 2.0 g / m under conditions of 40°C x 90% RH both before and after retort treatment. 2 In order to achieve good gas barrier properties, it is preferable that the thickness is 1.5 g / m or less. Furthermore, by controlling the amount of the inorganic thin film layer component deposited, it is possible to obtain a thickness of 1.5 g / m or less. 2 ·d or less, preferably 1.0 g / m 2 d or less. The water vapor permeability is 2.0 g / m 2 If the water vapor permeability exceeds 0.1 g / m before and after retort treatment, it becomes difficult to use the film in applications that require high gas barrier properties. 2 If the water vapor permeability is less than 0.1 g / m, the barrier performance will be excellent, but the residual solvent will be less likely to permeate to the outside of the bag, which is undesirable because there is a risk that the amount of water vapor that migrates to the contents will increase relatively. 2 ·d or more.

[0083] The laminate of the present invention preferably has a water-wet lamination strength of 1.0 N / 15 mm or more under conditions of 23°C x 65% RH both before and after retort treatment, more preferably 1.5 N / 15 mm or more, and even more preferably 2.0 N / 15 mm or more. If the lamination strength is less than 1.0 N / 15 mm, peeling may occur due to bending load or liquid contents, resulting in deterioration of barrier properties or leakage of contents. Furthermore, hand tearability may also be impaired. [Example]

[0084] 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 films were evaluated by the following measurement methods.

[0085] (1) Intrinsic viscosity (IV) of the raw resin and the resin that constitutes the base film The sample was dried in a vacuum at 130°C overnight, then crushed or cut, and 80 mg of the crushed sample was precisely weighed and dissolved in a mixed solution of phenol / tetrachloroethane = 60 / 40 (volume ratio) at 80°C for 30 minutes by heating. After dissolving by heating at 80°C, the sample was cooled to room temperature, and the mixed solvent prepared in the above ratio was added to a measuring flask to make 20 ml, after which the viscosity was measured at 30°C (unit: dl / g). An Ostwald viscometer was used to measure the intrinsic viscosity.

[0086] (2) Contents of terephthalic acid and isophthalic acid components contained in the raw material polyester and the polyester constituting the base film A sample solution was prepared by dissolving the raw polyester resin or polyester film in a solvent containing a 10:1 (volume ratio) mixture of chloroform D (manufactured by Eurisop) and trifluoroacetic acid D1 (manufactured by Eurisop). The sample solution was then subjected to NMR measurement of the protons in the sample solution using an NMR device (Varian GEMINI-200 nuclear magnetic resonance analyzer) at a temperature of 23°C and an accumulation count of 64. In the NMR measurement, the peak intensity of a specific proton was calculated, and the content (mol%) of terephthalic acid and isophthalic acid components in 100 mol% of the acid component was calculated.

[0087] (3) Thickness of the base film Measurement was carried out using a dial gauge in accordance with JIS K7130-1999 Method A.

[0088] (4) Thermal shrinkage rate of the base film in the longitudinal and transverse directions A 10 mm wide sample of the base film was taken, and benchmark lines were marked at 200 mm intervals at room temperature (27°C). The distance between the benchmark lines was measured (L 0). The film was then sandwiched between papers and placed in a hot air oven controlled at a temperature of 150°C. After 30 minutes of treatment, the film was removed and the distance between the benchmark lines was measured (L). The thermal shrinkage was calculated using the following formula: Samples were taken in both the machine and cross directions. Heat shrinkage rate (%) = {(L 0 - L ) / L 0} × 100

[0089] (5) Refractive index in the thickness direction of the base film The refractive index in the thickness direction (Nz) was determined in accordance with JIS K7142 using an Abbe refractometer NAR-1T (manufactured by Atago Co., Ltd.) with sodium D line as the light source, a test piece with a refractive index of 1.74, and methylene iodide as the intermediate liquid.

[0090] (6) Composition and thickness of inorganic thin film layer The film thickness composition of the laminated films (after thin film lamination) obtained in the examples and comparative examples was measured using a fluorescent X-ray analyzer ("ZSX100e" manufactured by Rigaku Corporation) based on a previously prepared calibration curve. The excitation X-ray tube conditions were 50 kV and 70 mA.

[0091] (7) Coating thickness In each example and comparative example, each laminated film obtained at the stage of laminating a coating layer on a base film was used as a sample, and a 100 mm × 100 mm test piece was cut out from this sample. The coating layer was wiped off with 1-methoxy-2-propanol or dimethylformamide, and the amount of adhesion was calculated from the change in mass of the film before and after wiping. (8) Method for measuring surface hardness of laminated film The surface hardness of the laminated film was measured using a dynamic ultra-microhardness tester (Shimadzu Corporation, "DUH-211"). Specifically, a load-unload test was performed on the protective layer surface of a single laminated film fixed to a glass plate with adhesive using a diamond triangular pyramid indenter (Berkovich type) with an edge angle of 115°. The Martens hardness obtained was used as the surface hardness value. The test conditions were a test force of 1.0 mN, a loading rate of 0.02 mN / s, and a holding time of 2 seconds. Note that the hardness measured under these conditions had an indentation depth of 0.3 μm or more, which was sufficiently large compared to the thickness of the coating layer and inorganic thin film layer, and was interpreted as representing the surface hardness of the substrate.

[0092] (9) Measurement method for arithmetic mean roughness of laminated film The surface roughness of the laminated film was measured using a scanning probe microscope (SPM) (Shimadzu Corporation, SPM9700) (cantilever: Olympus OMCL-AC200TS, observation mode: phase mode). Specifically, SPM images were taken of the film surface over a 2 μm square field of view. The resulting images were corrected for tilt in the X, Y, and Z directions using the tilt correction function of the SPM's software, and the arithmetic mean roughness (Ra) was calculated. The roughness curve was obtained by removing surface waviness components longer than a specified wavelength from the cross-sectional curve using a high-pass filter. A reference length was extracted from the roughness curve along the mean line of the extracted section, and the X axis was plotted along the mean line of the extracted section, with the Y axis along the longitudinal magnification. The roughness curve was then expressed as y = f(X), and the value calculated using the following equation was expanded two-dimensionally: Ra=1 / L∫ L 0|f(x)|dx L: Reference length

[0093] (10) Measurement method of friction coefficient of laminated film The static friction coefficient μs and dynamic friction coefficient μd on the vapor-deposited and non-vapor-deposited surfaces of the film were measured in a 50% RH atmosphere according to ASTM-D-1894.

[0094] [Preparation of laminated body] A 15 μm-thick nylon film (Toyobo Co., Ltd., "N1100") was laminated onto the laminates obtained in the Examples and Comparative Examples using a urethane-based two-component curing adhesive (Mitsui Chemicals, Inc., "Takelac® A525S" and "Takenate® A50" blended in a 13.5:1 (mass ratio)). A 70 μm-thick unstretched polypropylene film (Toyobo Co., Ltd., "P1146") was then laminated onto the nylon film using the same urethane-based two-component curing adhesive as above using a dry lamination method. The laminated gas barrier laminates for evaluation (hereinafter sometimes referred to as "Laminate A") were obtained by aging at 40°C for 4 days. The thickness of the adhesive layer formed with the urethane-based two-component curing adhesive after drying was approximately 4 μm.

[0095] (11) Evaluation method for oxygen permeability The laminate prepared in the above [Preparation of Laminated Body] was measured for oxygen permeability under normal conditions in an atmosphere of 23°C and 65%RH using an oxygen permeability measuring device (MOCON's "OX-TRAN (registered trademark) 1 / 50") in accordance with JIS-K7126 Method B. The oxygen permeability measurement was performed in the direction in which oxygen permeates from the substrate film side of the laminated body to the heat-sealable resin layer side. The laminated body prepared in the above [Preparation of Laminated Body] was subjected to a moist heat treatment by being kept in hot water at 130°C for 30 minutes, and then dried at 40°C for 1 day (24 hours). The oxygen permeability (after retort) of the resulting moist heat-treated laminated body was measured in the same manner as above.

[0096] (12) Evaluation method for water vapor permeability The water vapor permeability of the laminate prepared in the above [Preparation of Laminate] was measured under normal conditions at a temperature of 40°C and a humidity of 90%RH using a water vapor permeability measuring device ("PERMATRAN-W 3 / 33MG" manufactured by MOCON) in accordance with JIS-K7129 Method B. The water vapor permeability was measured in the direction in which water vapor permeated from the heat-sealable resin layer side of the laminate to the base film side. On the other hand, the laminate prepared in the above [Preparation of Laminated Body] was subjected to a moist heat treatment by being kept in hot water at 130°C for 30 minutes, and then dried at 40°C for 1 day (24 hours). The water vapor permeability (after retort) of the resulting moist heat treated laminate was measured in the same manner as above.

[0097] (13) Evaluation method for laminate strength The laminated body prepared above was cut into a width of 15 mm and a length of 200 mm to prepare a test piece, and the laminate strength (normal state) was measured using a Tensilon universal material testing machine (Tensilon UMT-II-500 model, manufactured by Toyo Baldwin Co., Ltd.) under conditions of a temperature of 23°C and a relative humidity of 65%. The laminate strength was measured at a tensile speed of 200 mm / min, with water applied between the laminated film layer and the heat-sealable resin layer of each laminated film obtained in the examples and comparative examples, and the strength was measured when the laminated film layer and the heat-sealable resin layer were peeled at a peel angle of 90°. On the other hand, the laminate prepared above was subjected to retort treatment by holding it in pressurized hot water at a temperature of 130°C for 30 minutes, and then immediately after that, a test piece was cut out from the resulting laminate after retort treatment in the same manner as above, and the laminate strength (after retort treatment) was measured in the same manner as above.

[0098] (14) Evaluation of processability of laminated film The film rolls obtained after vapor deposition of the laminates described in the Examples and Comparative Examples were inspected for the presence or absence of four defects: wrinkles, pimples, winding misalignment, and blocking. Those with no defects were marked with an ◯, those with any one defect were marked with a △, and those with two or more defects were marked with an ×.

[0099] The coating liquids used in Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Table 1 below.

[0100] [Carbodiimide crosslinking agent (A)] As a carbodiimide-based crosslinking agent, commercially available "Carbodilite (registered trademark) SV-02" manufactured by Nisshinbo Co., Ltd. (solid content: 40%) was prepared. [Resin (B) having an oxazoline group] A commercially available water-soluble acrylate containing oxazoline groups (Epocross (registered trademark) WS-300, manufactured by Nippon Shokubai Co., Ltd.; solid content: 10%) was prepared as a resin having oxazoline groups. The amount of oxazoline groups in this resin was 7.7 mmol / g.

[0101] [Acrylic resin (C)] As the acrylic resin, a 25% by mass emulsion of a commercially available acrylic acid ester copolymer ("Movinyl (registered trademark) 7980" manufactured by Nichigo Movinyl Co., Ltd.) was prepared. The acid value (theoretical value) of this acrylic resin was 4 mg KOH / g.

[0102] [Urethane resin (D)] A commercially available polyester urethane resin dispersion (Mitsui Chemicals' "Takelac (registered trademark) W605"; solids content 30%) was prepared as the urethane resin. The acid value of this urethane resin was 25 mgKOH / g, and the glass transition temperature (Tg) measured by DSC was 100°C. The proportion of aromatic or araliphatic diisocyanate to the total polyisocyanate component measured by 1H-NMR was 55 mol%. [Silane coupling agent (E)] As a silane coupling agent, a commercially available product "KBM903 (registered trademark)" (solid content 100%) manufactured by Shin-Etsu Chemical Co., Ltd. was prepared. When used, it was diluted with water to give a 2% aqueous solution.

[0103] [Urethane resin (F)] In a four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 143.95 parts by mass of meta-xylylene diisocyanate, 25.09 parts by mass of 4,4'-methylenebis(cyclohexyl isocyanate), 28.61 parts by mass of ethylene glycol, 5.50 parts by mass of trimethylolpropane, 12.37 parts by mass of dimethylolpropionic acid, and 120.97 parts by mass of methyl ethyl ketone as a solvent were mixed and stirred at 70 ° C. under a nitrogen atmosphere. It was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 35 ° C., and then 9.14 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 794.97 parts by weight of water was added to a reaction vessel equipped with a high-speed homodisperser, and the temperature was adjusted to 15°C. While stirring and mixing at 2000 min-1, the polyurethane prepolymer solution was added and dispersed in water. An amine aqueous solution containing 22.96 parts by weight of 2-[(2-aminoethyl)amino]ethanol and 91.84 parts by weight of water was then added. Next, an amine aqueous solution containing 2.38 parts by weight of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (trade name: KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) and 9.50 parts by weight of water was added, and a chain extension reaction was carried out. Subsequently, methyl ethyl ketone and a portion of the water were removed under reduced pressure to obtain a polyurethane dispersion (E) with a solids content of 25% by weight and an average particle size of 70 nm. The resulting polyurethane dispersion (D-1) had a Si content (calculated based on the charge) of 1200 mg / 1 kg and a metaxylylene group content (calculated based on the charge) of 32% by weight.

[0104] [Coating liquid 1 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Water 53.48% by mass Isopropanol 22.00% by mass Oxazoline group-containing resin (A) 18.70% by mass Acrylic resin (B) 3.74% by mass Urethane resin (C) 1.98% by mass

[0105] [Coating liquid 2 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Water 60.58% by mass Isopropanol 15.00% by mass Oxazoline group-containing resin (A) 18.70% by mass Acrylic resin (B) 3.74% by mass Urethane resin (C) 1.98% by mass

[0106] [Coating liquid 3 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Water 57.80% by mass Isopropanol 25.00% by mass Carbodiimide crosslinking agent (A) 2.10% by mass Urethane resin (F) 8.00% by mass Silane coupling agent (E) 7.10% by mass

[0107] [Coating liquid 4 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Water 59.00% by mass Isopropanol 25.00% by mass Urethane resin (F) 16.00% by mass

[0108] The methods for producing the laminated films used in each of the Examples and Comparative Examples are described below. The films used in Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 1.

[0109] (Preparation of polyester resin recycled from PET bottles) After washing away any remaining beverages and other foreign matter from PET beverage bottles, the resulting flakes were crushed and melted in an extruder. The flakes were filtered twice using successively smaller mesh filters to remove even finer particles, and then filtered a third time using a filter with the smallest mesh size (50 μm) to obtain recycled polyester raw material. The resulting resin had a composition of terephthalic acid / isophthalic acid / ethylene glycol = 97.0 / 3.0 / / 100 (mol%), and the resin's intrinsic viscosity was 0.70 dL / g. This was designated Polyester A.

[0110] (Preparation of base film) Polyester B was a polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl / g, composed of 100% terephthalic acid / ethylene glycol (mol%) and 100% ethylene glycol (mol%). Polyester C was a masterbatch of polyester B containing 0.3% amorphous silica with an average particle size of 1.5 μm. The raw materials were dried at 125°C for 8 hours under a reduced pressure of 33 Pa. The mixture was mixed in a weight ratio of A / B / C = 70 / 20 / 10 and then fed into a single-screw extruder. The resin temperature was set to 280°C from the extruder through the melt line, filter, and T-die. However, the resin temperature was set to 305°C for 30 seconds from the start of the compression section of the extruder screw, after which it was returned to 280°C.

[0111] The molten material extruded from the T-die was brought into close contact with a cooling roll to form an unstretched sheet. This was then stretched 1.41 times in the machine direction using rolls heated to 118°C with different peripheral speeds (MD1), and further stretched 2.92 times in the machine direction using rolls heated to 128°C with different peripheral speeds (MD2). The machine-stretched sheet was introduced into a tenter, and one side of the film was coated with Coating Solution 1 using a fountain bar coating method. The sheet was introduced into the tenter while drying, preheated to 121°C, and then stretched 4.3 times transversely at 131°C. The heat setting was then performed at 180°C with no relaxation (0%) for 2.5 seconds (TS1), followed by 231°C with 5% relaxation for 3.0 seconds (TS2), followed by 222°C with no relaxation for 2.5 seconds (TS3). Subsequently, the film was cooled at 120° C. for 6.0 seconds in the same tenter, and finally taken up by a winder to obtain a biaxially oriented polyester film having a thickness of 12 μm.

[0112] In preparing the base film layer described in each example and comparative example, laminate films were produced and evaluated in the same manner, except that the blending amounts of polyesters A / B / C or the coating liquid constituting the coating layer were changed as shown in Table 1.

[0113] The method for producing the inorganic thin film layer used in each example and comparative example will be described below. The method used in examples 1 to 7 and comparative examples 1 to 5 is shown in Table 1. (Formation of inorganic thin film layer M-1) Aluminum oxide was vapor-deposited onto the base film layer to form the inorganic thin film layer M-1. The method for vapor-depositing aluminum oxide onto the base film layer involved placing the film on the unwinding side of a continuous vacuum deposition machine and running it over a cooled metal drum until the film was wound up. The continuous vacuum deposition machine was then depressurized to 10-4 Torr or less, and 99.99% pure aluminum metal was loaded into an alumina crucible from below the cooling drum. The aluminum metal was then heated and evaporated, and oxygen was supplied to the vapor, causing an oxidation reaction that caused it to adhere and deposit on the film, forming a 10 nm thick aluminum oxide film.

[0114] (Formation of inorganic thin film layer M-2) As the inorganic thin film layer M-2, a composite oxide layer of silicon dioxide and aluminum oxide was formed on the base film layer by electron beam evaporation. The evaporation sources used were 3-5 mm particulate SiO2 (purity 99.9%) and Al2O3 (purity 99.9%). The thickness of the inorganic thin film layer (SiO2 / Al2O3 composite oxide layer) in the film thus obtained (film containing an inorganic thin film layer / coating layer) was 13 nm. The composition of this composite oxide layer was SiO2 / Al2O3 (mass ratio) = 60 / 40.

[0115] In this way, a laminate film having a coating layer / inorganic thin film layer on a substrate film was produced. The obtained laminate film was evaluated. The results are shown in Table 2.

[0116] [Table 1]

[0117] [Table 2] [Industrial Applicability]

[0118] According to the present invention, it is possible to provide a laminate film using recycled materials, which has an excellent gas barrier property in the inorganic thin film layer and has excellent barrier property and adhesiveness even after severe moist heat treatment such as retort sterilization. Moreover, the laminate film of the present invention has few processing steps and is easy to produce, so it is excellent in both economy and production stability, and it is possible to provide a gas barrier film with uniform properties.

Claims

1. A laminate film having a coating layer and an inorganic thin film layer on one side of a base film, characterized in that the laminate film satisfies the following requirements (a) to (f): (a) The base film contains 50% by weight or more and 95% by weight or less of a polyester resin containing 10 mol% or less of an isophthalic acid component recycled from PET bottles. (b) The surface hardness of the laminated film, defined as the Martens hardness on the inorganic thin film layer surface, is 120 N / mm ２ It must be less than or equal to: (c) The coating layer contains a resin having an oxazoline group or a carbodiimide group as a constituent component. (d) The content of isophthalic acid components relative to the total dicarboxylic acid components in the total polyester resin constituting the base film is 0.5 mol % or more and 5.0 mol % or less. (e) The static friction coefficient μs and dynamic friction coefficient μd of the inorganic thin film layer surface and the opposite surface of the laminated film are both in the range of 0.20 to 0.

40. (f) The arithmetic mean roughness Ra of the laminated film in a 2 μm square area is in the range of 2.0 to 6.0 nm.

2. 2. The laminated film according to claim 1, wherein the inorganic thin film layer is a layer of aluminum oxide or a composite oxide of silicon oxide and aluminum oxide.

3. 3. The laminated film according to claim 1, further comprising a protective layer containing a urethane resin on the inorganic thin film layer.

4. A sealant layer is laminated on one side of the laminate film according to any one of claims 1 to 3. packaging materials.

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