TW202408791A - Multilayer film, lid material for food packaging container, and food packaging container - Google Patents

Abstract

The purpose of the present invention is to provide a multilayer film which is excellent in terms of all of anti-fogging properties, easy-opening properties, impact resistance, and environmental friendliness. The multilayer film has at least two layers: a substrate layer; and an anti-fogging layer, wherein (a) the heat seal strength at each temperature of 120 DEG C, 140 DEG C, 160 DEG C, and 180 DEG C is 2.0-12.0 N/15 mm, (b) the water contact angle under the conditions of 5 DEG C and 50% RH is 50 DEG or less, (c) the peel strength between the anti-fogging layer surface and the substrate layer surface of the multilayer film is 1 N/15 mm or less, (d) the impact strength at 5 DEG C is 0.5 J or more, (e) the thickness unevenness of the multilayer film is 10% or less in both the MD direction and the TD direction, (f) the substrate layer of the multilayer film contains a recycled polyester resin, and the amount of isophthalic acid relative to the total dicarboxylic acid units is 0.5-3.2 mol%.

Description

Laminated films, lidding materials for food packaging containers, and food packaging containers

The present invention relates to a laminated film that combines easy opening, anti-fogging properties and environmental adaptability. Specifically, it relates to a laminated film that is more suitable for heat bonding with packaging containers. In particular, it relates to a laminated film used as a cover material for food packaging containers.

As a material for packaging vegetables and other fruits and vegetables, containers formed of plastic films or sheets are currently used. Containers made of polyester-based materials such as polyethylene terephthalate (PET) are widely used in consideration of not only aesthetic appearance such as transparency and gloss, but also recyclable materials. When using such a polyester-based container, an embedded-shaped lid, also called a fitting lid, has conventionally been used as a lid material. However, there are disadvantages such as the risk of the lid falling off due to external stress, causing the contents to scatter, or the risk of foreign matter being mixed in when the product is opened during display. Therefore, in recent years, the use of top-sealing films as covering materials has been advancing. The main properties required for top sealing include: anti-fog, easy opening, impact resistance, and adhesion resistance. The anti-fog property is, for example, the function of preventing the water vapor emitted from the content from fogging the cover material during storage or displaying the product when the content is fruits and vegetables such as salad, making it difficult to recognize the content. Ease of opening shows the following functions: whether it is easy to open and whether the lid material does not break when opening, so that it can be opened beautifully. Impact resistance refers to the following indicators: for example, whether there is any damage to the cover material due to external impact when transporting the product or the weight of overlapping products during display. The adhesion resistance is the following function: It prevents adhesion when the top sealing film is stored in a roll due to the heat sealing layer provided in the top sealing material, thus affecting the operability.

Patent Document 1 proposes an adhesive composition that contains polyester resin A with a glass transition temperature of -30°C to 30°C and an anti-fogging agent C. It is suitable for laminating food packaging containers and lidding films. Since the heat seal strength and anti-fog properties are good, biaxially aligned polyester film is used as the cover material, so it is expected that the impact resistance will also be good. However, the biaxially aligned polyester film used as a cover material is a general biaxially stretched film, and the tear strength tends to be reduced due to the production method of the biaxially stretched film. Therefore, when a container is opened and damage caused by peeling between the container and the lid material is transmitted to the lid material film, it is expected that it will easily break and fail to exhibit easy opening properties.

Patent Document 2 proposes a cover material that is made of polyester-based components and has a sealing layer and a base material layer. The cover material exhibits good heat-sealing properties and anti-fog properties relative to the container. Since it has good anti-fog properties and is a biaxially oriented polyester film, it is expected to have good impact resistance. On the other hand, the heat seal strength will be very strong and it is expected that it will be difficult to peel off easily when the container is opened. Furthermore, even in embodiments with weak heat sealing strength, the strength is likely to change drastically when the heat sealing temperature is changed, and it is expected that it will be difficult to maintain the desired heat sealing strength during actual manufacturing steps. In addition, since copolymerized polyester resin is used in the sealing layer, the resulting biaxially aligned polyester film is expected to have a large thickness variation. When the thickness is uneven, the sealing layer will stick when stored in a roll, which will greatly affect the operability.

Patent document 3 proposes a laminated film that uses a biaxially oriented polyester film as a base layer and an off-line coated polyester resin layer as a heat-sealable outer layer, and exhibits good heat-sealability for food trays. Although the heat-seal strength and anti-fogging properties are good, since the biaxially oriented polyester film used as the base layer is a general biaxially stretched film, it is expected that the base layer will break when the container is opened and it will not be easy to open. In addition, since the Tg of the polyester resin used for the heat-seal outer layer is 0°C to 30°C and it is a single resin, it is expected that the blocking resistance is poor.

Polyethylene terephthalate (PET) is widely used as molded products such as films and containers due to its excellent mechanical strength, chemical resistance and other characteristics. In recent years, due to increasingly serious environmental problems and resource conservation, etc. On the other hand, recycling these used PET containers has been available for many years. For example, used PET containers are crushed, washed, melted and pelletized, and recycled into films for food packaging. On the other hand, there are also problems with using such recycled raw materials to make membranes. One is that compared to PET films made from raw materials derived from fossil fuels, PET films derived from recycled raw materials tend to have poorer thickness accuracy. This is because a small amount of isophthalic acid is added to PET bottles for beverages and PET containers for food, which are sources of recycled raw materials, to improve formability. By adding isophthalic acid, the yield stress decreases during the production of PET films and the thickness accuracy decreases. [Prior technical literature] [Patent Document]

[Patent Document 1] International Publication No. 2008/179689. [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-114992. [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-209996.

[The problem that the invention wants to solve]

The purpose of the present invention is to provide a laminated film with good anti-fogging, easy opening and impact resistance. The purpose is also to provide a laminated film and a lid material (also called a top seal material) for a food packaging container using the laminated film, wherein the laminated film further uses recycled raw materials and has excellent thickness accuracy. [Means for solving the problem]

The present inventors discovered that by designing the film-forming conditions, a base film with excellent balance between impact strength and tear strength and good thickness unevenness can be obtained. Furthermore, they discovered that by combining this base film with an anti-fog layer containing polyester resins having two or more glass transition temperatures, a laminated film most suitable for use as a lidding film for polyester containers can be obtained. Based on the aforementioned technical insights, further reviews and improvements were accumulated, and the invention shown below was completed.

[item 1] A laminated film having at least two layers: a base material layer and an anti-fog layer; (a) Heat seal the anti-fog layer of the aforementioned laminated film and an unstretched polyethylene terephthalate sheet with a thickness of 200 μm at 0.2 MPa at each temperature of 120°C, 140°C, 160°C, and 180°C. Seconds, the heat sealing strength measured using a test piece with a width of 15mm is from 2.0N/15mm to less than 12.0N/15mm; (b) Under the conditions of 5°C and 50% relative humidity (R.H.), drop 1 μL of distilled water on the surface of the anti-fog layer of the aforementioned laminated film, and the water contact angle measured after 5 seconds is below 50°; (c) The impact strength under the condition of 5℃ in the pendulum impact test is above 0.5J; (d) The tear strength under the condition of 5°C is 100mN or more in both the MD direction and the TD direction of the aforementioned laminated film; (e) The thickness unevenness of the above-mentioned laminated film in both the MD direction and the TD direction is 10% or less, as determined by the calculation formula of the following formula (1); Uneven thickness (%) = (Tmax-Tmin)/Tave×100 Formula (1) Tmax: maximum thickness of laminated film Tmin: minimum thickness of laminated film Tave: average thickness of laminated film (f) The base material layer contains a recycled polyester resin, and the isophthalic acid content of the base material layer is 0.5 mol% or more and 3.2 mol% or less based on all dicarboxylic acid units.

According to item 1, the heat sealing strength when heat sealing at each temperature of 120°C, 140°C, 160°C, and 180°C is from 2.0N/15mm to 12.0N/15mm, and there is a necessary gap between the container and the lid material. Heat sealing strength, and when the cover material is opened, the cover material can be opened easily and in a manner that does not damage the cover material. According to item 1, 1 μL of distilled water is dropped on the surface of the anti-fog layer of the laminated film, and the water contact angle measured after 5 seconds is 50° or less, indicating excellent anti-fogging properties. According to item 1, the impact strength under the condition of 5℃ is more than 0.5J, which has the effect of preventing the damage of the cover material caused by strong impact from the outside. According to item 1, the tear strength under the condition of 5°C in the MD direction and TD direction of the aforementioned laminated film is 100mN or more, and it has easy opening properties. That is, when the container is opened, it can be suppressed that damage caused by peeling between the container and the lid material is transmitted to the laminated film, causing the lid material to break. According to item 1, the thickness unevenness of the laminated film in both the MD direction and the TD direction is less than 10%, which can prevent adhesion in the film roll. According to Item 1, the base layer of the laminated film contains a polyester resin composed of recycled raw materials, and the isophthalic acid content is 0.5 mol% or more and 3.2 mol% or less based on all dicarboxylic acid units, and is environmentally adaptable. sex.

The present invention preferably has the following structure of item 2. [Item 2] In the case of the laminated film described in item 1, in which a sample with a length of 200 mm is cut out from the laminated film and the film thickness is imaged at intervals of 0.5 mm, in the thickness concave-convex pattern, the part with the largest difference between the maximum thickness of the convex part and the minimum thickness of the concave part is set as the maximum convex part, and at this time, the value of the thickness unevenness of the maximum convex part obtained by the calculation formula of the following formula (2) in the MD direction and the TD direction is less than 6%. Thickness unevenness of the maximum convex part (%) = (maximum thickness of the maximum convex part - minimum thickness of the maximum convex part) / Tave × 100 Formula (2)

According to Item 2, by setting the thickness unevenness of the largest convex portion to 6% or less, it is possible to prevent local application of stress at locations with large thickness differences in the film roll to cause adhesion and rupture during unwinding. An accident in the processing step.

The present invention preferably has the structure of the following item 3 or later. [Item 3] The laminated film as described in Item 1 or 2, wherein the anti-fog layer of the aforementioned laminated film is laminated to the substrate layer of the aforementioned laminated film, and under the condition of 40°C, a load of 450kgf/ ^m2 is applied After leaving for a week, the peel strength measured using a test piece with a width of 15 mm was 1.0 N/15 mm or less.

According to item 3, the peeling strength when the antifogging layer of the laminate film and the substrate layer of the laminate film are superimposed is 1.0 N/15 mm or less, which can prevent the films from sticking to each other.

[Item 4] A multilayer film as described in any one of Items 1 to 3, wherein the strength ratio of the tear strength in the MD direction to the tear strength in the TD direction of the multilayer film measured at 5°C (tear strength _MD /tear strength _TD ) is 0.6 or more and 1.5 or less.

According to item 4, by setting the orientation of the MD direction and the TD direction in the laminate film to be isotropic, the lid material can be easily opened regardless of the opening direction.

[item 5] The laminated film according to any one of items 1 to 4, wherein the alignment coefficient of the laminated film is 0.6 or more and 1.5 or less, as determined by the calculation formula of equation (3) using an Abbe refractometer. Alignment coefficient = {Nx-(Ny+Nz)/2}/{Ny-(Nx+Nz)/2} Equation (3) Nx: refractive index in the MD direction of the film Ny: refractive index in the TD direction of the film Nz: refractive index in the thickness direction of the film

According to item 5, by setting the orientation of the MD direction and the TD direction in the laminate film to be isotropic, the lid material can be easily opened regardless of the opening direction.

[Item 6] A laminated film as described in any one of items 1 to 5, wherein the substrate layer is a biaxially aligned polyester film. [Item 7] A laminated film as described in any one of items 1 to 6, wherein the antifogging layer contains at least two resins, a polyester resin (A) having a glass transition temperature Tg of 0°C to 40°C and a polyester resin (B) having a glass transition temperature Tg of 41°C to 80°C. [Item 8] A laminated film as described in item 7, wherein the mass ratio of the polyester resin (A) to the polyester resin (B) in the resin constituting the antifogging layer is polyester resin (A): polyester resin (B) = 50/50 to 90/10.

According to items 7 and 8, the anti-fog layer has at least two polyester resins with different glass transition temperatures, thereby achieving both heat sealability and preventing the cover material from cracking when the cover material is opened.

[Item 9] The laminated film as described in Item 7 or 8, wherein the antifogging layer contains a nonionic surfactant. [Item 10] The laminated film as described in Item 9, wherein the HLB value of the nonionic surfactant is greater than 3 and less than 10.

According to items 9 and 10, the laminated film of the present invention has anti-fogging properties.

[item 11] The laminated film according to any one of items 1 to 10, wherein the haze of the laminated film is less than 10%. [item 12] The laminated film according to any one of items 1 to 11 includes the adhesive layer, the base material layer and a printing layer.

Furthermore, the present invention provides a cover material for food packaging containers using the above-mentioned laminated film. [item 13] A cover material for food packaging containers, which includes the laminated film described in any one of items 1 to 12.

Furthermore, the present invention provides a food packaging container having a lid material using the above-mentioned laminated film. [item 14] A food packaging container having a lid material for food packaging containers as described in item 13. [Invention effect]

According to the present invention, a laminated film and a cover material having excellent anti-fogging properties, easy opening properties, impact resistance and anti-adhesion properties can be provided.

[Antifogging layer] The antifogging layer in the laminated film of the present invention preferably contains at least the following polyester resin (A), polyester resin (B) and antifogging agent (C) components. By containing the polyester resin (A) component and the polyester resin (B) component, not only excellent easy opening property, wide sealing temperature range and anti-blocking property can be exhibited, but by containing the antifogging agent (C) component, excellent antifogging property can also be exhibited. In addition, in order to further improve the anti-blocking property, an anti-blocking agent (D) may also be contained.

The polyester resin (A) and the polyester resin (B) are preferably polyesters having the following chemical structure: a carboxylic acid component composed of a polyvalent carboxylic acid compound having a valence of more than or equal to 2, and a polyvalent carboxylic acid compound having a valence of more than or equal to 2. The chemical structure obtained by polycondensation of the alcohol component composed of alcohol compounds. When the polyester has a chemical structure obtained by polycondensation between a carboxylic acid component composed of a polyvalent carboxylic acid compound of bivalent or higher and an alcohol component composed of a polyhydric alcohol compound of bivalent or higher, polycarboxylic acid is preferred. At least one of the acid compound and the polyol compound is a copolyester resin composed of two or more components. In addition, the polycarboxylic acid compound and the polyol compound are preferably copolyester resins mainly composed of a carboxylic acid component and a diol component. Here, "mainly" means that the total of the dicarboxylic acid component and the diol component is 200 mol% relative to the total of the total acid component and the total alcohol component constituting the polyester resin (A) used in the present invention. The ear basis accounts for more than 100 mol%.

As dicarboxylic acid, aromatic dicarboxylic acid or aliphatic dicarboxylic acid is preferred, and aromatic dicarboxylic acid is more preferred. When the total amount of carboxylic acid components is set to 100 mol%, the lower limit of the copolymerization amount of aromatic dicarboxylic acid components is preferably 40 mol%, more preferably 45 mol, and particularly preferably 50 mol%. By setting it to 40 mol% or more, the glass transition temperature Tg can be suppressed to a low value.

Specific examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, etc., but are not limited to these components. Specific examples of aliphatic dicarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, etc., but are not limited to these components. These dicarboxylic acids may be used alone, or two or more types may be used in combination. In addition, as other polycarboxylic acid components, aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-(hydroxyethoxy)benzoic acid, fumaric acid, maleic acid, itaconic acid, hexagonal acid, etc. can be used. Hydrophthalic acid, tetrahydrophthalic acid and other unsaturated alicyclic dicarboxylic acids, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid Alicyclic dicarboxylic acids such as hexanedicarboxylic acid, etc. In addition, tricarboxylic acids or tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid, and anhydrides of tricarboxylic acids or tetracarboxylic acids may also be contained as needed.

As the diol component, an aliphatic diol is preferred. When the total amount of the diol components is set to 100 mol%, the lower limit of the copolymerization amount of the aliphatic diol component is preferably 70 mol%, more preferably 75 mol%, and particularly preferably 80 mol%. By setting it to 70 mol% or more, the glass transition temperature Tg can be suppressed to a low value.

Specific examples of aliphatic diols include: ethylene glycol, propylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-butanediol. Diol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, Polypropylene glycol, polytetramethylene glycol, etc., but are not limited to these components. These diol components may be used individually or in combination of 2 or more types. In addition, as other diol components, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanediol, and bisphenol A can also be used. The ethylene oxide adduct and propylene oxide adduct, the ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, etc. In addition, a small amount of triols and tetraols such as trimethylolethane, trimethylolpropane, glycerin, and neopentylerythritol may also be included as needed.

The glass transition temperature Tg of the polyester resin (A) is preferably from 0°C to 40°C, more preferably from 5°C to 35°C, particularly preferably from 10°C to 30°C. By setting it to 0° C. or higher, the blocking resistance becomes good. By setting the temperature to 40°C or lower, the heat sealing strength can be controlled within a predetermined range and easy opening can be obtained.

The lower limit of the reduced viscosity (ηsp/c) of the polyester resin (A) is preferably 0.2 dl/g, more preferably 0.4 dl/g, and particularly preferably 0.6 dl/g. When the reduced viscosity is 0.2 dl/g or more, the resin cohesion is expressed and the heat seal strength is expressed.

The number average molecular weight (Mn) of the polyester resin (A) is preferably 5,000 or more, more preferably 10,000 or more, and particularly preferably 15,000 or more. By setting it to 5000 or more, resin cohesion is expressed and heat sealing strength is expressed. There is no particular upper limit, but it is preferably 50,000 or less, more preferably 40,000 or less.

The glass transition temperature of the polyester resin (B) is preferably from 41°C to 80°C, more preferably from 46°C to 75°C, particularly preferably from 51°C to 60°C. By setting it within the above range, the heat sealing strength can be set within the range of the requirements, and easy opening properties can be obtained.

The lower limit of the reduced viscosity (etasp/c) of the polyester resin (B) is preferably 0.1dl/g, more preferably 0.2dl/g, and particularly preferably 0.3dl/g. By setting it to 0.1 dl/g or more, resin cohesion is expressed and heat sealing strength is expressed.

The number average molecular weight (Mn) of the polyester resin (B) is preferably 2000 or more, more preferably 5000 or more, and particularly preferably 10000 or more. When it is 2000 or more, the resin cohesion is exhibited and the heat seal strength is exhibited. The upper limit is not particularly limited, but is preferably 30000 or less, and more preferably 20000 or less.

By mixing at least two polyester resins with different glass transition temperatures, a certain degree of heat sealing strength and ease of opening can be obtained in a wide temperature range of 120°C to 180°C. The mechanism by which the ease of opening described above is achieved by mixing polyester resins with different glass transition temperatures is probably because cohesion cracking in the anti-fog layer selectively occurs when heat sealing strength is measured. Generally speaking, when measuring heat seal strength, the location of failure is usually considered to proceed from the location with the weakest mechanical strength. The anti-fogging layer in the laminated film of the present invention is considered to be because the polyester resin (B) with a high glass transition temperature exhibits high heat sealing strength with the sealing surface, and the polyester resin (A) with a low glass transition temperature is The mechanical strength of the anti-fog layer is reduced, in other words, the anti-fog layer is brittle. Therefore, compared with the mechanical strength of the anti-fog layer, the mechanical strength of the heat sealing strength is greater, and selective agglomeration and rupture occur in the anti-fog layer with the weakest mechanical strength. Therefore, in the present invention, by mixing at least two polyester resins with different glass transition temperatures, it is possible to selectively produce cohesion cracking in the anti-fog layer that does not depend on the heat sealing temperature, and exhibit performance in a wide temperature range. Easy to open.

The lower limit of the mass ratio of the polyester resin (A) to the polyester resin (B) is preferably polyester resin (A): polyester resin (B) = 50:50, more preferably 45:55, and particularly preferably 60:40. By setting the mass ratio to 50:50 or more, the antifogging layer can be made brittle, and the heat seal strength described in the claim can be set within a wide temperature range, thereby obtaining easy opening properties. The upper limit of the mass ratio of the polyester resin (A) to the polyester resin (B) is preferably polyester resin (A): polyester resin (B) = 90:10, more preferably 85:15, and particularly preferably 80:20. By setting the ratio to 90:10 or less, the sealing strength of the sealing surface can be increased, and the heat seal strength can be set within the range described in the claim in a wide temperature range, thereby achieving easy opening properties.

The antifogging agent (C) is not particularly limited as long as it can impart antifogging properties, and for example, anionic surfactants, nonionic surfactants, cationic surfactants, or amphoteric surfactants can be used. Among them, nonionic surfactants are preferably used.

For example, examples of anionic surfactants include sulfate ester salts of higher alcohols, higher alkyl sulfonates, higher carboxylates, alkyl benzene sulfonates, polyoxyethylene alkyl sulfates, and polyoxyethylene alkyl sulfates. Phenyl ether sulfate, vinyl sulfosuccinate. Examples of nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyethylene glycol fatty acid ester, ethylene oxide and propylene oxide block copolymer, and polyoxyethylene. Fatty amide, ethylene oxide-propylene oxide copolymer and other compounds with polyoxyethylene structure or sorbitan derivatives. Examples of cationic surfactants include alkylamine salts, dialkylamine salts, trialkylamine salts, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, and alkyl chloride. Alkyl benzalkonium chloride. Examples of amphoteric surfactants include lauryl betaine and lauryl dimethylamine oxide.

Specific examples of the nonionic surfactant include sorbitan monostearate, sorbitan distearate, sorbitan monopalmitate, sorbitan dipalmitate, and sorbitol. Sorbitan-based surfactants such as anhydride monobehenate, sorbitan di(behenate), sorbitan monolaurate, sorbitan dilaurate, etc.; glycerol monolaurate, Glyceryl dilaurate, diglyceryl monopalmitate, diglyceryl dipalmitate, glyceryl monostearate, glyceryl distearate, diglyceryl monostearate, diglyceryl distearate, Glycerol-based surfactants such as diglyceryl monolaurate and diglyceryl dilaurate; polyethylene glycol-based surfactants such as polyethylene glycol monostearate and polyethylene glycol monopalmitate; trihydroxy Trimethylolpropane-based surfactants such as methylpropane monostearate; lauryl diethanolamine, oleyl diethanolamine, stearyl diethanolamine, lauryl diethanolamine, oleyl diethanolamine, hard Diethanol alkyl amine series and diethanol alkyl amide series surfactants such as aliphatic diethanol amide; neopentyl erythritol series surfactants such as neopentyl glycol monopalmitate and polyoxyethylene sorbitan monoanhydride Stearate, polyoxyethylene sorbitan distearate, monostearate and distearate of sorbitan-diglycerol condensation polymer, etc. These nonionic surfactants may be used alone or in combination of two or more types.

Specifically, cationic surfactants include amine salts such as laurylamine acetate, triethanolamine monoformate, and stearylamide ethyl diethylamine acetate; quaternary ammonium salts such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, dilauryldimethylammonium chloride, distearyldimethylammonium chloride, lauryldimethylbenzylammonium chloride, and stearyldimethylbenzylammonium chloride. These cationic surfactants may be used alone or in combination of two or more.

The lower limit of the hydrophilic-lipophilic balance (HLB) value of the anti-fogging agent (C) is preferably 3, more preferably 4, and particularly preferably 5. By setting it to 3 or more, anti-fogging properties are expressed. The upper limit of the HLB value of the anti-fog agent (C) is preferably 10, more preferably 9, and even more preferably 8. By setting it to 10 or less, excessive precipitation of the anti-fog agent on the film surface can be prevented, and deterioration of haze and reduction in sealing strength can be prevented.

The content of the antifogging agent (C) in the antifogging layer is preferably 1.0 mass % to 10.0 mass % in terms of solid content concentration, more preferably 1.5 mass % to 9.5 mass % and particularly preferably 2.0 mass % to 9.0 mass %. When the content is 1.0 mass % or more, antifogging properties are exhibited. When the content is 10.0 mass % or less, the fogging is good and the reduction in heat seal strength caused by excessive precipitation of the antifogging agent on the film surface can be suppressed.

The anti-fog layer of the present invention may contain an anti-adhesive agent (D). Examples of the anti-blocking agent include inorganic particles, organic particles, waxes, etc., and the anti-blocking agent can be contained to an extent that does not cause a decrease in heat sealing strength. These anti-adhesive agents may be used alone, or two or more types may be used in combination. In the solid content concentration conversion of the anti-fog layer, the lower limit of the anti-blocking agent content is preferably 0.1 mass%, more preferably 0.3 mass%, and particularly preferably 0.5 mass%. If it is 0.1 mass % or more, adhesion resistance will be exhibited. In the solid content concentration conversion of the anti-fog layer, the upper limit of the anti-adhesive agent content is preferably 5.0 mass%, more preferably 4.5 mass%, and particularly preferably 4.0 mass%. If it is 5.0 mass% or less, the heat sealing strength will not be impaired.

Examples of inorganic particles include: inorganic particles containing metal oxides, hydroxides, sulfates, carbonates or silicates such as magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony or titanium. Among these inorganic particles, silica particles are particularly preferred. The shape of the particles may be any shape such as powder, granules, particles, plates, needles, etc.

Examples of the organic particles include polymethylmethacrylate resin, polystyrene resin, nylon resin, melamine resin, benzoguanamine resin, phenol resin, urea resin, silicone resin, and methacrylate resin. , or polymer particles such as acrylate resin; or cellulose powder, nitrocellulose powder, wood powder, waste paper powder, starch, etc. The shape of the particles can be any shape such as powder, granular, granular, flat, needle-shaped, etc.

Specific examples of waxes include hydrocarbon waxes such as mobile paraffin, natural paraffin, micro paraffin, synthetic paraffin, and polyethylene wax; fatty acid waxes such as stearic acid; stearic acid amide , palmitic acid amide, methylene distearamide, ethyl distearamide, oleic acid amide, esylic acid amide (esylic acid amide) and other fatty acid amide waxes; lower alcohols of fatty acids Ester-based waxes such as esters, polyol esters of fatty acids, and polyethylene glycol esters of fatty acids; alcohol-based waxes such as cetyl alcohol and stearyl alcohol; olefin-based waxes; natural waxes such as castor wax and carnauba wax ; Metal soaps derived from fatty acids with 12 to 30 carbon atoms, etc.

The anti-fog layer is laminated on at least one side of the base material layer. Regarding the lamination method, it can be produced by the following methods: co-extrusion with the resin composition constituting the base material layer, dry lamination of the base material layer and the anti-fog layer, and lamination of the anti-fog layer to the base material layer. Extrusion coating, or solvent coating method on the base material layer. Preferably, the organic solvent of the resin composition constituting the anti-fog layer is applied (coated) to the base material layer and dried to obtain the laminated film of the present invention.

The thickness of the anti-fog layer is preferably 0.3 μm or more, more preferably 0.5 μm or more, and particularly preferably 0.7 μm. If it is 0.3 μm or more, heat sealability is exhibited. The upper limit of the thickness of the anti-fog layer is preferably less than 3.0 μm, more preferably less than 2.8 μm, even more preferably less than 2.6 μm. If it is less than 3.0 μm, the thickness unevenness of the laminated film can be suppressed to a low level, and the blocking resistance becomes good.

[Substrate layer] The substrate layer in the laminated film of the present invention is preferably a biaxially oriented polyester film for the purpose of improving the impact resistance of the laminated film. If it is an unstretched polyester film, there are concerns that the impact resistance is poor due to the manufacturing method of the unstretched polyester film, and the film may be damaged due to external impact or the load generated by overlapping products during display. In other words, if it is an unstretched polyester film, the thickness unevenness is likely to become large due to the manufacturing method of the unstretched polyester film, and it is easy to cause adhesion when it is made into a roll. In addition, there is no particular limitation on the manufacturing method of the biaxially oriented polyester film. It can be either synchronous biaxial stretching or sequential biaxial stretching. However, when using the blown film method, it is easy to produce uneven thickness due to the manufacturing method of the blown film method, and it is easy to cause adhesion when it is made into a roll, so it is not good.

The main component of the substrate layer of the present invention is not particularly limited as long as it is polyester, and preferably polyethylene terephthalate is used as the main component. In addition, other polyesters may be contained within the scope that does not damage the present invention. Specifically, polyester resins include polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, and the like; polyester resins copolymerized with dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, cyclohexane dicarboxylic acid, adipic acid, azelaic acid, and sebacic acid; and polyester resins copolymerized with diol components such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, cyclohexanediol, polyethylene glycol, polytetramethylene glycol, and polycarbonate diol.

The substrate layer of the present invention preferably comprises a polyester resin composed of recycled raw materials obtained by recycling waste plastics. As the recycled raw materials, both pre-consumer materials of waste plastics generated from the film manufacturing step and post-consumer materials of waste plastics after use can be used. From the perspective of reducing plastic waste and reducing environmental load, post-consumer materials are preferred. As post-consumer materials, there can be listed: fibers containing polyester resin as a main component, containers for food/beverages, containers for detergents/drugs, other containers, packaging, etc. Plastic containers with high production volume and high recycling volume after use, that is, plastic bottles are more suitable.

In the polyester resin composition forming the base material layer, the polyester resin composed of recycled raw materials obtained from plastic containers as raw materials preferably contains at least 60 mass % or more of the total polyester resin, and more preferably contains 70 mass % or more. Mass% or more, more preferably 80 mass% or more.

As methods of recycling, there are physical recycling and chemical recycling, and both physical recycling and chemical recycling methods are acceptable. Hereinafter, an aspect will be described, which is a method of manufacturing post-consumer recycled materials through physical recycling of plastic containers whose main raw material is PET.

[Physically recycled polyester resin] Sort the used plastic containers that have been recycled in such a way that they are not mixed with other materials or garbage, remove labels, etc., and crush them into thin pieces. There are many cases where foreign matter adheres to or gets mixed into these sheets. In addition, it is also necessary to consider the situation where consumers fill used plastic containers with chemical substances such as medicines or solvents. For example, it can be presumed to be detergents for tableware, insecticides, herbicides, pesticides, or various oils. Since ordinary cleaning cannot fully remove chemical substances attached to the surface of plastic containers, it is better to perform alkaline cleaning. As the alkali metal hydroxide solution used in this washing step, a sodium hydroxide solution or a potassium hydroxide solution is used. In this cleaning step, pre-washing can also be performed before alkali washing. When alkali cleaning is not performed, foreign matter will remain in the resin of the raw material. The mixing of these foreign matter will not only cause breakage during film production and reduce productivity, but also remain in the form of foreign matter in the film, which may cause damage. The appearance of the film, or the reason for the loss of printing in subsequent printing steps.

The concentration of the aqueous solution of alkali metal hydroxide used in the above-mentioned cleaning step varies with the temperature, time, and stirring state, but is generally in the range of 1% to 10% by weight. In addition, the time required for cleaning is 10 to 100 minutes. In order to improve efficiency, it is better to clean while stirring.

It is preferable to wash and dry after alkali washing. Alkaline washing and washing can also be repeated several times. In the alkali washing step, the aqueous solution component of the alkali metal hydroxide used for cleaning remains in the sheet, and then passes through the melt extrusion step in the subsequent granulation and granulation step or the melt extrusion step in film formation, thus affecting the The physical properties of the resulting film.

In this washing step, a portion of the plastic container flakes are hydrolyzed by an aqueous solution of an alkaline metal hydroxide. In addition, the degree of polymerization of the resin is reduced due to heating during film formation. Furthermore, after the recycled plastic container is crushed for reuse, the degree of polymerization is reduced due to the heat or moisture applied during re-melting and granulation. Although it can be directly reused, when the degree of polymerization is reduced depending on the purpose of use, the formability, strength, transparency or heat resistance may deteriorate, and it may not be directly reused. In this case, in order to restore the reduced degree of polymerization, it is better to solid-phase polymerize the crushed and washed plastic container flakes or the flakes melted and granulated.

In the solid-state polymerization step, the washed flakes, or the flakes obtained by melt extrusion and granulated, can be inert gases such as nitrogen and rare gases at 180°C to 245°C (preferably 200°C to 240°C). Continuous solid phase polymerization is carried out in gas.

The polyester resin that is ultimately used as recycled plastic bottles is preferably adjusted into sheets or under the condition that the inherent viscosity is 0.55dl/g to 0.90dl/g, preferably 0.60dl/g to 0.85dl/g. Solid phase polymerization is carried out under particle conditions.

The step of granulating the flakes is explained. The flakes are melted, extruded, cooled, and granulated using an extruder with a degassing means and a filtering means. In the melting step of the extruder, the melt kneading can be performed at a temperature of usually 260°C to 300°C, preferably 265°C to 295°C. The flakes obtained by crushing the plastic bottles to be filled must be fully dried in advance, preferably to a condition of 5ppm to 200ppm, preferably 10ppm to 100ppm, and more preferably 15ppm to 50ppm. In the case where the flakes contain a lot of water, a hydrolysis reaction is performed in the melting step, and the inherent viscosity of the obtained polyester resin is reduced. As a degassing means, it is preferred to have at least one vacuum exhaust hole in the melting area of the resin. In addition, the extruder preferably has a filter as a filtering means that can filter and remove solid foreign matter with a particle size of 25 μm or more, preferably 15 μm or more, and more preferably 10 μm or more in the molten resin. The molten resin that has passed through the filter is cooled in water through a mold and then cut into particles of a desired shape for granulation.

The flakes or granules obtained by the above method are alone or mixed with polyester resin composed of virgin raw materials, extruded from the extruder into sheets, and extended along the MD direction and TD direction to obtain biaxially aligned polyester. membrane.

In the substrate layer of the present invention, the lower limit of the amount of isophthalic acid relative to the total dicarboxylic acid units is preferably 0.5 mol%, more preferably 1.0 mol%, and particularly preferably 1.5 mol%. For example, a small amount of isophthalic acid is added to PET bottles for the purpose of improving formability. Such recycled raw materials from PET containers must contain isophthalic acid, and as a result, the amount of isophthalic acid in the substrate layer is 0.5 mol% or more. The upper limit of the amount of isophthalic acid relative to the total dicarboxylic acid units is preferably 3.2 mol% or less, more preferably 2.7 mol% or less, and particularly preferably 2.2 mol% or less. By setting it to 3.2 mol% or less, the upper yield stress during stretching of the substrate film can be suppressed from being excessively reduced, and as a result, it can be stretched uniformly and the deterioration of thickness unevenness can be prevented.

In order to improve the lubricity of the laminate film, inorganic lubricants such as titanium dioxide, micro-silicon dioxide, kaolin, calcium carbonate, and organic lubricants such as long-chain fatty acid esters may be added. In addition, colorants, antistatic agents, ultraviolet absorbers, etc. may also be added as needed.

The layer structure of the base material layer is not particularly limited. It can be a single-layer structure, a two-layer structure, a three-layer structure, a four-layer structure, or a super multi-layer structure. In addition, the composition of each layer can also be different.

The method for obtaining the base layer is not particularly limited, but the T-molding method is preferred from the viewpoint of good thickness accuracy. The blown film method is prone to uneven thickness due to the production method of the blown film method.

The upper limit of the cooling roller temperature is preferably below 40° C., more preferably below 20° C. If it is below 40° C., the crystallinity of the melted polyester resin composition will not become too high when it is cooled and solidified, and it will be easy to stretch.

The lower limit of the stretching temperature in the longitudinal direction (also referred to as the MD direction) is preferably 90°C, more preferably 95°C, and particularly preferably 100°C. If it is 90°C or higher, the cracking can be suppressed. The upper limit of the stretching temperature in the MD direction is preferably 140°C, more preferably 135°C, and particularly preferably 130°C. If it is 140°C or lower, the orientation can be fully achieved, and the impact strength of the film after biaxial orientation can be improved.

The lower limit of the extension ratio in the MD direction is preferably 3.0 times, more preferably 3.2 times, and particularly preferably 3.4 times. If it is 3.0 times or more, the thickness unevenness becomes better and the adhesion resistance improves. The upper limit of the extension ratio in the MD direction is preferably 4.0 times, more preferably 3.8 times, and particularly preferably 3.6 times. By setting it to 4.0 times or less, breakage can be suppressed.

The lower limit of the extension temperature in the transverse direction (also called TD direction) is preferably 100°C, more preferably 105°C, and particularly preferably 110°C. If it is 100°C or above, fracture can be suppressed. The upper limit of the extension temperature in the TD direction is preferably 140°C, more preferably 135°C, and particularly preferably 130°C. If it is 140°C or lower, sufficient alignment can be achieved and the impact strength of the film after biaxial alignment can be improved.

The lower limit of the extension ratio in the TD direction is preferably 3.5 times, more preferably 3.6 times, and particularly preferably 3.7 times. If it is 3.5 times or more, thickness unevenness becomes good and adhesion resistance improves. The upper limit of the extension ratio in the MD direction is preferably 4.5 times, more preferably 4.4 times, and particularly preferably 4.3 times. By setting it to 4.5 times or less, breakage can be suppressed.

The laminated film of the present invention preferably achieves a balance between impact strength and tear strength, and also has good thickness unevenness. With respect to thickness unevenness, the stretching step in the TD direction has the greatest impact, especially closely related to the film-making conditions of the substrate layer. For example, if the stretching ratio in the TD direction increases, the impact strength increases and the thickness unevenness decreases, but the tear strength decreases. In the stretching step in the TD direction, it is better to adopt a method of setting the TD stretching mode to a multi-stage stretching method as shown in FIG2, or a method of setting it to a logarithmic form as shown in FIG3. If it is a general linear TD stretching mode as shown in FIG1, it is necessary to reduce the stretching ratio to achieve a balance between impact strength and tear strength. In this case, the thickness unevenness will become larger, resulting in concerns about deterioration of adhesion resistance. On the other hand, if it is a multi-stage stretching method or a logarithmic TD stretching mode, the film orientation can be suppressed without reducing the stretching ratio, and the thickness unevenness can still be maintained and a balance between impact strength and tear strength can be achieved, so it is better.

In the case of multi-stage stretching along the TD direction, it is preferred that the multi-stage stretching is more than two stages and less than five stages. Multi-stage stretching is preferred because the stretching stress can be changed by changing each stretching temperature, thereby suppressing the orientation. As shown in FIG2 , in multi-stage stretching, it is preferred to set the mode to maintain a fixed length after each stage of stretching is completed. In addition, it is preferred to adopt the following temperature mode: in each stage of stretching, a temperature difference of more than 2°C is set, and the temperature is lowered from the first stage of stretching to the final stage of stretching.

The lower limit of the heat fixing temperature is preferably 180°C, more preferably 190°C, and particularly preferably 200°C. If it is 180°C or above, the thermal shrinkage rate can be reduced. The upper limit of the heat fixing temperature is preferably 240°C, more preferably 230°C, and particularly preferably 220°C. If it is 240°C or lower, the impact strength can be prevented from decreasing.

The lower limit of the relaxation rate is preferably 0.5%, more preferably 1.0%, and particularly preferably 2.0%. If it is 0.5% or more, the thermal shrinkage rate can be kept low. The upper limit of the relaxation rate is preferably 10%, more preferably 8%, and particularly preferably 6%. If it is set to 10% or less, sagging can be prevented, and adhesion can be prevented when forming a roll.

The lower limit of the thickness of the substrate layer of the present invention is preferably 5 μm, more preferably 10 μm, and particularly preferably 15 μm. By setting it to 5 μm or more, the impact strength and tear strength can be maintained. The upper limit of the thickness of the substrate layer of the present invention is preferably 100 μm, more preferably 80 μm, and particularly preferably 50 μm. By setting it to 100 μm or less, it can be suitably used as a cover material.

[Laminated film] The water contact angle in the present invention is measured under the conditions of a measuring temperature of 5°C and a relative humidity of 50% (50%R.H.). A-PET containers containing food such as salads are often stored and displayed under refrigerated conditions, and anti-fog properties become important at this time. Therefore, as a condition for a water contact angle that appropriately expresses anti-fogging properties under refrigerated conditions, a condition of 5°C is more appropriate than a general room temperature condition.

The upper limit of the water contact angle of the laminated film of the present invention is preferably 50°, more preferably 40°, and particularly preferably 30°. By setting it to 50° or less, even if water vapor scattered from the contents adheres to the laminated film, the water droplets can spread thinly, and fog will not appear on the appearance. The lower limit of the water contact angle of the laminated film of the present invention is preferably 10°, more preferably 15°, and particularly preferably 20°. By setting it to 10° or more, it is possible to prevent the anti-fog agent from excessively precipitating on the surface and thereby reducing the heat sealing strength.

The lower limit of the heat seal strength of the laminated film of the present invention and the unstretched polyethylene terephthalate sheet with a thickness of 200 μm when heat-sealed at each temperature of 120°C, 140°C, 160°C, and 180°C is preferably 2N/15mm, more preferably 3N/15mm, and particularly preferably 4N/15mm. By setting it to 2N/15mm or more, it can be sealed with sufficient strength when used as a lid material.

When the laminated film of the present invention and an unstretched polyethylene terephthalate sheet with a thickness of 200 μm are heat-sealed at each temperature of 120°C, 140°C, 160°C, and 180°C, the upper limit of the heat-sealing strength is the same. 12N/15mm is preferred, 11N/15mm is more preferred, and 10N/15mm is particularly preferred. By setting it to 12N/15mm or less, in addition to not requiring excessive force when opening due to excessive sealing strength when used as a lid material, it is also possible to prevent the laminated film from cracking due to excessive sealing strength.

One feature of the present invention is that when the laminated film is used as an amorphous polyethylene terephthalate (A-PET) lidding material, a certain degree of heat seal strength can be generated within a wide temperature range by intentionally generating cohesive fractures in the antifogging layer when the lidding material is opened.

When the antifogging layer of the laminated film of the present invention is superimposed on the substrate layer of the laminated film and a load of 450 kgf/ ^m2 is applied and the peeling strength is left at 40°C for one week, the upper limit is 1.0 N/15 mm, preferably 0.8 N/15 mm, and particularly preferably 0.6 N/15 mm. By setting it to 1.0 N/15 mm or less, accidents in the processing steps such as adhesion of the films when made into a roll form, and cracking when unrolling, etc. can be prevented. In the present invention, the antifogging layer has at least two polyester resins with different glass transition temperatures, which has the effect of inhibiting the adhesion of the films.

The lower limit of the impact strength of the laminated film of the present invention is 0.5 J, more preferably 0.6 J, and even more preferably 0.8 J. By setting it to 0.5 J or more, the laminated film has sufficient strength to withstand external stress during container transportation or display, thereby preventing the cover material from breaking.

The lower limit of the tear strength of the laminated film of the present invention is 100 mN, preferably 110 mN, and particularly preferably 120 mN. By setting it to 100 mN or more, it is possible to avoid the cohesive rupture in the antifogging layer generated when the container is opened from being transmitted to the substrate layer, directly causing the entire substrate layer to rupture, thereby achieving good unsealing properties.

In the laminated film of the present invention, the lower limit of the strength ratio (tear strength _MD /tear strength _TD ) of the tear strength in the MD direction to the tear strength in the TD direction is 0.6, more preferably 0.7, and particularly preferably 0.8. By setting it to 0.6 or more, the orientation of the laminated film can be isotropically suppressed, and easy opening properties can be obtained. Generally speaking, when the lid is opened, there will be subtle differences depending on how each person opens it, so the vertical and horizontal forces exerted on the lid are random. Therefore, the anisotropy is strong and prone to rupture.

The upper limit of the strength ratio of the tear strength in the MD direction to the tear strength in the TD direction (tear strength _MD /tear strength _TD ) in the laminated film of the present invention is 1.5, preferably 1.3, and particularly preferably 1.1. By setting it to 1.5 or less, the orientation of the laminated film can be isotropically suppressed, and easy opening properties can be obtained.

The lower limit of the alignment coefficient obtained by using an Abbe refractometer and calculating the following formula (3) for the laminated film of the present invention is 0.6, more preferably 0.7, and particularly preferably 0.8. By setting it to 0.6 or more, the orientation of the laminated film can be isotropically suppressed, and easy opening properties can be obtained. Alignment coefficient = {Nx-(Ny+Nz)/2}/{Ny-(Nx+Nz)/2} Equation (3) Nx: refractive index in the MD direction of the film Ny: refractive index in the TD direction of the film Nz: refractive index in the thickness direction of the film

The upper limit of the orientation coefficient of the laminated film of the present invention obtained by using an Abbe refractometer and the calculation formula of the following formula (3) is 1.5, preferably 1.3, and particularly preferably 1.1. By setting it to 1.5 or less, the orientation of the laminated film can be isotropically suppressed, and easy opening properties can be obtained.

The upper limit of the thickness unevenness of the laminated film of the present invention is preferably 10% in both the MD direction and the TD direction, more preferably 6%, and particularly preferably 4%. By setting it below 10%, it is possible to prevent the accidental processing step of cracking during unrolling due to local stress applied at the location of poor thickness unevenness when making a roll.

The upper limit of the thickness unevenness of the maximum convex portion of the laminated film of the present invention is preferably 6% in both the MD direction and the TD direction, more preferably 5%, and particularly preferably 4%. By setting it to be less than 6%, it is possible to prevent the accidental processing step of cracking during unwinding due to local stress applied at the location of the poor thickness unevenness when making a roll. The so-called large thickness unevenness of the maximum convex portion means that the thickness difference within the maximum convex portion is large. If the thickness difference of the maximum convex portion is large, when making a roll form, excessive winding stress will be applied to the maximum thickness portion of the maximum convex portion, resulting in a state that is more prone to adhesion. Therefore, if the thickness unevenness of the maximum convex portion is small and the winding stress can be widely dispersed, adhesion can be prevented.

The maximum convex part in the present invention refers to a sample of 200 mm in length cut out from the laminated film at intervals of 0.5 mm, with the vertical axis being the thickness (unit: μm) and the horizontal axis being the measurement position (unit: mm). When the thickness polyline is visualized, in the concave-convex pattern of thickness expressed, the difference between the maximum thickness of the convex part and the minimum thickness of the concave part is greatest. FIG. 5 shows an example of the above image and the largest convex portion.

The upper limit of the haze of the laminated film of the present invention is preferably 10% or less, more preferably 8%, particularly preferably 6%. If it is 10% or less, the transparency will be high when used as a cover material, and the contents can be fully recognized.

The laminated film of the present invention is suitably used as a packaging material. In particular, it is suitably used as a lid material for food packaging containers. When used as a lid material for food packaging containers, it is preferred that the antifogging layer of the laminated film is in contact with the edge of the container opening of the food packaging container to seal. The food packaging container using the laminated film of the present invention as a lid material is not particularly limited, and is preferably a polyester container, and particularly preferably an A-PET (amorphous polyethylene terephthalate) container.

[Example] Indicates the physical property evaluation method. [Thickness of base material layer] The thickness of the base material layer was measured using an electronic micrometer Millitron 1202D manufactured by Seiko EM Co., Ltd. before the anti-fog agent was laminated.

[Thickness of anti-fog layer] The thickness of the laminated film (base material layer + anti-fog layer) was measured using an electronic micrometer Millitron 1202D manufactured by Seiko EM Co., Ltd. Afterwards, completely wipe off the anti-fog layer side of the laminated film with a solvent that can dissolve the anti-fog layer. The thickness of the wiped sample is measured in the same manner, and the thickness of the anti-fog layer is calculated by the following formula (4). The thickness of the anti-fog layer (μm) = the thickness of the laminated film (μm) – the thickness of the film after erasing (μm) Formula (4)

[Content of isophthalic acid component in substrate layer] The sample was dissolved in a solvent prepared by mixing chloroform D (manufactured by EURISO-TOP) and trifluoroacetic acid D1 (manufactured by EURISO-TOP) at a volume ratio of 10:1 to prepare a sample solution. The NMR (Nuclear Magnetic Resonance) ("GEMINI-200"; manufactured by Varian) was used to measure the proton NMR of the sample solution at a temperature of 23°C and a cumulative number of 64 measurements. The NMR measurement is to calculate the peak intensity of the predetermined proton and calculate the content (molar %) of the terephthalic acid component and the isophthalic acid component in 100 molar % of the acid component.

[Mist density of laminated film] According to JIS K7361-1, the laminated film was cut into a square shape with a side of 10 cm, and the mist density was measured using a mist meter NDH2000 manufactured by Nippon Densho Co., Ltd. The measurement was carried out at six locations, and the average value of the measured values was set as the actual measured mist density value.

[Heat seal strength] An unstretched polyethylene terephthalate sheet with a thickness of 200 μm was overlapped with the antifog layer side of the laminate film. This sample was heat-sealed. The heat seal conditions were set to a top bar temperature between 120°C and 180°C with 20°C as the scale, a bottom bar temperature of 30°C, a pressure of 0.2 MPa, and a time of 1 second. The heat-sealed sample was cut out in such a way that the seal width became 15 mm. The heat seal strength was measured using a tensile tester "AGS-KNX" (manufactured by Shimadzu Corporation) with a sample chuck spacing of 20 mm and a tensile speed of 200 mm/min. The heat seal strength is expressed as the strength per seal width of 15 mm (N/15 mm).

[Water contact angle] The water contact angle of the antifog layer of the laminate film was measured using a contact angle meter "PORTABLE CONTACT ANGLE METER PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.)" at 5°C and 50% relative humidity (R.H.). The amount of water dropped for one measurement was set to 1μL, and the angle between the antifog layer and the water drop was read 5 seconds after the drop. The water contact angle was read using the θ/2 method, and the water contact angle was measured at 10 locations for each sample, and the average of the measured values was set as the contact angle of the sample.

[Evaluation of adhesion resistance] Two evaluation samples with a size of 15cm×15cm are cut from the laminated film of the present invention. The substrate layer side and the antifogging layer side of the evaluation sample are overlapped, a load of 450kgf/ ^m2 is applied from above, and the samples are left at 40°C for one week. Afterwards, the evaluation samples are taken out and cut into pieces with a width of 15mm to measure the peeling strength of the substrate layer and the antifogging layer. The peeling strength is measured using a tensile testing machine "AGS-KNX" (manufactured by Shimadzu Corporation) with a sample chuck spacing of 20mm and a tensile speed of 200mm/min. The peeling strength is expressed as the strength per 15mm (N/15mm).

[Impact Strength] The impact strength of the laminated film was measured at 5°C and 50% relative humidity (R.H.) using an impact tester (manufactured by Toyo Seiki Seisaku-sho, Ltd.). The impact ball surface used was an impact ball surface with a diameter of approximately 1.2 inches.

[Tear strength] The tear strength of the laminated film was measured using a light load tear tester (manufactured by Toyo Seiki Seisaku-sho) in accordance with JIS-K7128-2. The notch was 12.7 mm.

[Orientation coefficient] A 5 mm square sample was cut from the laminate film. For this sample, the refractive index in the longitudinal direction (Nx), the refractive index in the transverse direction (Ny), and the refractive index in the thickness direction (Nz) of the film were measured using the JIS K7142-1996 A method with sodium D line as the light source and diiodomethane as the contact liquid using the Abbe refractometer NAR-1T (manufactured by Atago Co., Ltd.). The orientation coefficient is calculated by the following formula (1). Orientation coefficient = {Nx-(Ny+Nz)/2}/{Ny-(Nx+Nz)/2} Formula (1)

[Uneven Thickness] Cut out strip-shaped samples with a length of 200 mm and a width of 40 mm in the TD and MD directions from five positions of the laminated film. This sample was measured using a continuous contact thickness meter (manufactured by Mikuron Measuring Instruments Co., Ltd.) at a speed of 5 m/min and an interval of 0.5 mm. According to the maximum value, minimum value and average thickness of the measured thickness, use the following formula (1) to calculate the thickness unevenness in the TD direction and MD direction respectively, and use it as the average value of the five positions, and further calculate the MD The largest value among the thickness unevenness in the direction and the thickness unevenness in the TD direction is set as the thickness unevenness of the laminated film (%). Thickness unevenness (%) = (T _max - T _min )/T _ave × 100 Formula (1) T _max : The maximum thickness of the laminated film T _min : The minimum thickness of the laminated film T _ave : The average thickness of the laminated film

[Uneven thickness of the largest convex part] Long strip-shaped samples with a length of 200 mm and a width of 40 mm in the TD and MD directions were cut out from five positions of the laminated film. This sample was measured using a continuous contact thickness meter (manufactured by Mikuron Measuring Instruments Co., Ltd.) at a speed of 5 m/min and an interval of 0.5 mm. As shown in Figure 5, from the entire measurement range of 1000mm, the largest convex portion with the largest difference between the maximum thickness and the minimum thickness is found within an arbitrary measurement range of 200mm. Using the maximum thickness, the minimum thickness, and the average thickness of the maximum convex portion, the thickness unevenness of the maximum convex portion is calculated according to the following formula (2). Uneven thickness of the largest convex part (%) = (Maximum thickness of the largest convex part – Minimum thickness of the largest convex part)/Tave×100 Formula (2)

[Anti-fog evaluation] Cut the laminated film into a 30cm×30cm square sample. Inject 300 mL of 50°C hot water into a plastic container (capacity: 500 mL, diameter of the opening: about 10 cm), and cover the opening of the plastic container with the sample so that the anti-fog layer side becomes the hot water side to prepare an evaluation sample. . Furthermore, the opening is fixed and sealed with a rubber band. After this evaluation sample was left to stand for 30 minutes at 5° C., water droplets adhering to the cover material were visually evaluated based on the following standards. Judgment Y: Fogging caused by water droplets does not reach 1/4 of the entire area of the opening. Judgment N: Fogging caused by water droplets accounts for more than 1/4 of the total area of the opening.

[Easy to open] The antifog layer side of the laminate film was superimposed on an A-PET container of the shape and size shown in Figure 4, and heat-sealed from the top of the laminate film. The heat-sealing conditions were set at 120°C, 140°C, 160°C, and 180°C, with a pressure of 0.2 MPa and a time of 1 second. Afterwards, the ease of peeling off the laminate film when peeled off by hand was evaluated based on the following tactile sensation. Judgment A: Sufficient adhesion and easy to peel off by hand. Judgment B: Insufficient adhesion and peeling even without applying force. Judgment C: The adhesion was too strong and could not be easily peeled off by hand. Judgment D: The film broke when opening.

[Production Example] (1) Polyester A-1 Dimethyl terephthalate [55 parts by mass], dimethyl isophthalate [15 parts by mass], dimethyl sebacate [30 parts by mass], ethylene glycol [30 parts by mass], and 2,2-dimethyl-1,3-propanediol [30 parts by mass] were added to an ester reaction tank, and the temperature was raised to 230°C over 4 hours to carry out an ester exchange reaction. After the ester exchange reaction was completed, the system was heated to 250°C and the pressure was reduced to 10 torr over 60 minutes, and a polycondensation reaction was carried out at 250°C for 60 minutes. Thereafter, nitrogen was introduced into the system, and the vacuum was released to terminate the polycondensation reaction. After the reaction was completed, the polyester resin was taken out and cooled to obtain polyester A-1. The glass transition temperature was 7°C.

(2)Polyester A-2 Add dimethyl terephthalate [70 parts by mass], dimethyl sebacate [30 parts by mass], ethylene glycol [30 parts by mass], and propylene glycol [70 parts by mass] into the ester reaction tank and spend 4 hours The temperature was raised to 230°C to perform transesterification reaction. After completion of the transesterification reaction, while raising the temperature in the system to 250°C, the pressure was reduced to 10 torr over 60 minutes, and a polycondensation reaction was performed at 250°C for 60 minutes. Thereafter, nitrogen gas was introduced into the system and the vacuum was released to terminate the polycondensation reaction. After the reaction is completed, the polyester resin is taken out and cooled to obtain polyester A-2. The glass transition temperature is 16°C.

(3)Polyester A-3 Dimethyl phthalate [45 parts by mass], dimethyl isophthalate [39 parts by mass], dimethyl sebacate [16 parts by mass], ethylene glycol [75 parts by mass], 2,2 -Dimethyl-1,3-propanediol [25 parts by mass] was added to the ester reaction tank, and the temperature was raised to 230°C over 4 hours to perform a transesterification reaction. After completion of the transesterification reaction, while raising the temperature in the system to 250°C, the pressure was reduced to 10 torr over 60 minutes, and a polycondensation reaction was performed at 250°C for 60 minutes. Thereafter, nitrogen gas was introduced into the system and the vacuum was released to terminate the polycondensation reaction. After the reaction is completed, the polyester resin is taken out and cooled to obtain polyester A-3. The glass transition temperature is 32°C.

(4) Polyester B-1 Dimethyl terephthalate [45 parts by mass], dimethyl isophthalate [45 parts by mass], dimethyl sebacate [10 parts by mass], ethylene glycol [50 parts by mass], and propylene glycol [50 parts by mass] were added to an ester reaction tank, and the temperature was raised to 230°C over 4 hours to carry out an ester exchange reaction. After the ester exchange reaction was completed, the system was heated to 250°C and the pressure was reduced to 10 torr over 60 minutes, and a polycondensation reaction was carried out at 250°C for 60 minutes. Thereafter, nitrogen was introduced into the system, and the vacuum was released to terminate the polycondensation reaction. After the reaction was completed, the polyester resin was taken out and cooled to obtain polyester B-1. The glass transition temperature was 47°C.

(5) Polyester B-2 Dimethyl terephthalate [50 parts by mass], dimethyl isophthalate [50 parts by mass], ethylene glycol [50 parts by mass], and 2,2-dimethyl-1,3-propanediol [50 parts by mass] were added to an ester reaction tank, and the temperature was raised to 230°C over 4 hours to carry out an ester exchange reaction. After the ester exchange reaction was completed, the system was heated to 250°C and the pressure was reduced to 10 torr over 60 minutes, and a polycondensation reaction was carried out at 250°C for 60 minutes. Thereafter, nitrogen was introduced into the system, and the vacuum was released to terminate the polycondensation reaction. After the reaction was completed, the polyester resin was taken out and cooled to obtain polyester B-2. The glass transition temperature was 67°C.

The physical properties of polyester A-1, polyester A-2, polyester A-3, polyester B-1, and polyester B-2 are shown in Table 1.

[Table 1] unit polyester resin A-1 A-2 A-3 B-1 B-2 composition Polycarboxylic acid ingredients terephthalic acid Mol% 55 70 45 45 50 isophthalic acid Mol% 15 - 39 45 50 sebacic acid Mol% 30 30 16 10 - Polyol ingredients Ethylene glycol Mol% 50 30 75 50 50 propylene glycol Mol% - 70 - 50 - 2,2-dimethyl-1,3-propanediol Mol% 50 - 25 - 50 physical properties reduced viscosity dl/g 1.0 0.6 0.8 0.6 0.6 number average molecular weight ━ 30000 17000 32000 16000 18000 glass transition temperature ℃ 7 16 32 47 67

(6) Polyester C: Physically recycled polyester resin After the used plastic bottles for beverages that have been recycled are washed out of any remaining foreign matter such as beverages, they are crushed into thin slices. The obtained flakes were washed with 3.5 wt% sodium hydroxide solution under stirring conditions at a flake concentration of 10 wt%, 85°C, and 30 minutes. After alkali washing, the flakes were taken out and washed with distilled water with stirring at a flake concentration of 10% by weight, 25° C., and 20 minutes. Replace the distilled water and repeat this cleaning step twice. After washing, the flakes are dried and melted with an extruder. The filters are sequentially changed to a fine mesh size filter and filtered twice for fine foreign matter. In the third filtration, a filter with a minimum mesh size of 50 μm is used. Filtration was performed to obtain polyester resin C with an intrinsic viscosity of 0.69 dl/g and an isophthalic acid content of 3.0 mol %.

(7) Polyester D: virgin polyester resin A PET resin derived from fossil fuels with terephthalic acid/ethylene glycol = 100//100 (mol%) (intrinsic viscosity of 0.62 dl/g) was used. [Example 1] Polyester C [42 parts by mass], polyester D [58 parts by mass] and porous silica particles [0.1 parts by mass] were put into an extruder. After the resin was melted at 280°C in the extruder, it was cast from a 280°C T-die and bonded to a cooling roll at 20°C using an electrostatic bonding method to obtain a single-layer unstretched sheet. Subsequently, the unstretched sheet was stretched 3.5 times in the MD direction at a temperature of 115°C, and then stretched 4.0 times in the TD direction through a multi-stage stretching tenter in a stretching mode. The multi-stage stretching is a three-stage stretching, the first stage stretching is carried out at 115°C, the second stage stretching is carried out at 112°C, and the third stage stretching is carried out at 109°C. Furthermore, a fixed length mode is set between each stretching stage. After TD stretching, a heat fixation treatment is immediately carried out at 220°C for 3 seconds and a 7% relaxation treatment is carried out for 1 second to obtain a biaxially oriented polyester film with a thickness of 25μm. This biaxially oriented polyester film is used as the substrate layer.

Polyester A-1 [75 mass %], polyester B-2 [19 mass %], antifogging agent C-1 (Rikemal L-71-D manufactured by Riken Vitamin Co., Ltd., nonionic surfactant, HLB 7.3) [5 mass %], anti-adhesion agent D (SYLOID C-812 manufactured by Grace Co., Ltd., amorphous silica) [1 mass %] were heated and stirred in an ethyl acetate solution to obtain a coating agent (A). This coating agent was applied off-line on the substrate layer to a thickness of 2 μm. This layer was used as an antifogging layer.

[Example 2] A laminated film was obtained in the same manner as in Example 1, except that the TD stretching mode of the biaxially aligned polyester film of the base layer was changed to a logarithmic form.

[Example 3] Except that the thickness of the antifogging layer was changed to 0.3 μm, a laminated film was obtained in the same manner as in Example 1.

[Example 4] A laminated film was obtained in the same manner as in Example 1 except that the thickness of the anti-fog layer was changed to 2.9 μm.

[Example 5 to Example 9] A laminated film was obtained in the same manner as in Example 1 except that the coating agent composition of the anti-fog layer was changed.

The compositions of coating agents (B) to (L) used in Examples 5 to 9 and Comparative Examples 6 to 11 described later are shown in Table 2. In addition, as antifogging agent C-2, a nonionic surfactant (NOIGEN ES-149D, HLB11.5 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used.

[Example 10] It was the same as Example 1 except that the resin composition used for the base material layer was changed to polyester C [91 parts by mass], polyester D [9 parts by mass] and porous silica particles [0.1 parts by mass]. way to obtain a laminated film.

[Table 2A]

[Table 2B]

Table 3 shows the physical properties and various evaluation results of the laminated films obtained in the Examples.

[Table 3A] unit Example 1 Example 2 Example 3 Example 4 Example 5 laminated film structure base material layer thickness μm 25 25 25 25 25 Amount of isophthalic acid Mol% 1.5 1.5 1.5 1.5 1.5 Extension ratio MD/TD times 3.5/4.0 3.5/4.0 3.5/4.0 3.5/4.0 3.5/4.0 TD extension method ━ Multiple extensions Logarithmic form Multiple extensions Multiple extensions Multiple extensions TD extension temperature first stage ℃ 115 115 115 115 115 second stage 112 112 112 112 The third stage 109 109 109 109 Anti-fog layer coating agent ━ (A) (A) (A) (A) (B) thickness μm 2.0 2.0 0.3 2.9 2.0 Laminated film physical properties Haze % 3.9 4.1 2.1 6.5 4.4 Heat seal strength 120℃ N/15mm 4.5 4.4 2.4 6.4 10.7 140℃ 4.1 4.3 2.1 6.4 11.3 160℃ 4.4 4.3 2.1 6.4 11.3 180℃ 4.2 4.3 2.4 5.8 11.2 water contact angle Spend 20 twenty two 20 twenty two 25 Peel strength N/15mm 0.4 0.3 0.2 0.8 0.0 Impact strength J 0.63 0.67 0.72 0.66 0.66 Tear strength MD mN 233 220 235 241 222 TD 163 154 161 165 161 MD/TD ━ 1.43 1.43 1.46 1.46 1.38 Alignment coefficient ━ 0.71 0.71 0.71 0.78 0.77 uneven thickness % 6.5 6.7 4.5 9.2 5.7 Uneven thickness of convex portion % 2.7 3.1 1.6 5.1 2.3 Anti-fog evaluation ━ Y Y Y Y Y Ease of opening evaluation 120℃ ━ A A A A A 140℃ ━ A A A A A 160℃ ━ A A A A A 180℃ ━ A A A A A

[Table 3B] unit Example 6 Example 7 Example 8 Example 9 Example 10 laminated film structure base material layer thickness μm 25 25 25 25 25 Amount of isophthalic acid Mol% 1.5 1.5 1.5 1.5 3.2 Extension ratio MD/TD times 3.5/4.0 3.5/4.0 3.5/4.0 3.5/4.0 3.5/4.0 TD extension method ━ Multiple extensions Multiple extensions Multiple extensions Multiple extensions Multiple extensions TD extension temperature first stage ℃ 115 115 115 115 115 second stage 112 112 112 112 112 The third stage 109 109 109 109 109 Anti-fog layer coating agent ━ (C) (D) (E) (F) (A) thickness μm 2.0 2.0 2.0 2.0 2.0 Laminated film physical properties Haze % 3.5 4.1 4.2 4.1 3.3 Heat seal strength 120℃ N/15mm 2.2 6.5 8.2 3.2 4.1 140℃ 2.2 6.8 8.0 3.4 3.9 160℃ 3.2 6.9 8.6 4.1 4.4 180℃ 2.7 6.9 8.6 4.1 4.6 water contact angle Spend twenty one 26 twenty two twenty one twenty two Peel strength N/15mm 0.9 0.1 0.0 0.7 0.8 Impact strength J 0.72 0.62 0.63 0.72 0.63 Tear strength MD mN 221 232 234 239 229 TD 160 157 160 165 157 MD/TD ━ 1.38 1.48 1.46 1.45 1.46 Alignment coefficient ━ 0.71 0.71 0.71 0.70 0.74 Uneven thickness % 7.7 6.6 6.9 6.9 9.7 Uneven thickness of convex portion % 3.1 2.7 2.2 2.5 5.5 Anti-fog evaluation ━ Y Y Y Y Y Ease of opening evaluation 120℃ ━ A A A A A 140℃ ━ A A A A A 160℃ ━ A A A A A 180℃ ━ A A A A A

[Comparative example 1] A laminated film was obtained in the same manner as in Example 1, except that the TD stretching mode of the biaxially aligned polyester film of the base material layer was changed to a linear type. The obtained laminated film had low tear strength in the TD direction and was unsatisfactory because the film was broken during easy-openability evaluation.

[Comparative example 2] A laminated film was obtained in the same manner as in Example 1, except that the TD stretching mode of the biaxially aligned polyester film of the base layer was changed to a linear type and the TD stretching ratio was changed to 3.5 times. The obtained laminated film had poor blocking resistance and impact strength.

[Comparative Example 3] A laminated film was obtained in the same manner as Example 1 except that the TD stretching mode of the biaxially oriented polyester film of the substrate layer was changed to a linear type, the MD stretching ratio was changed to 4.0 times, and the TD stretching ratio was changed to 3.5 times. The obtained laminated film had poor blocking resistance.

[Comparative example 4] A laminated film was obtained in the same manner as in Example 1 except that the thickness of the anti-fog layer was changed to 0.2 μm. The obtained laminated film had a large water contact angle, and not only had poor anti-fog properties, but also had low heat sealing strength, and was poor in heat sealing when evaluating ease of opening.

[Comparative example 5] A laminated film was obtained in the same manner as in Example 1 except that the thickness of the anti-fog layer was changed to 3.2 μm. The obtained laminated film had poor blocking resistance.

[Comparative Example 6] Except for changing the coating composition of the antifogging layer, a laminated film was obtained in the same manner as in Example 1. The obtained laminated film had a high heat seal strength, but was difficult to open when evaluating the ease of opening and was poor.

[Comparative Example 7] Except for changing the coating composition of the antifogging layer, a laminated film was obtained in the same manner as in Example 1. The obtained laminated film not only had poor anti-blocking properties, but also had low heat-seal strength and could not be heat-sealed when evaluating easy-opening properties.

[Comparative example 8] A laminated film was obtained in the same manner as in Example 1 except that the coating agent composition of the anti-fog layer was changed. The obtained laminated film had high heat sealing strength, but was difficult to open when evaluating the ease of opening, which was unsatisfactory.

[Comparative Example 9] A laminated film was obtained in the same manner as in Example 1 except that the coating agent composition of the anti-fog layer was changed. The heat-sealing strength of the obtained laminated film was low, and it was unsatisfactory because it could not be heat-sealed when evaluating easy-openability.

[Comparative Example 10] A laminated film was obtained in the same manner as in Example 1 except that the coating agent composition of the anti-fog layer was changed. The resulting laminated film had a large water contact angle and poor anti-fogging properties.

[Comparative Example 11] Except for changing the coating composition of the antifogging layer, a laminated film was obtained in the same manner as in Example 1. The obtained laminated film not only had poor anti-blocking properties, but also had low heat-seal strength. It was not heat-sealable when evaluating the ease of opening and was poor.

[Comparative Example 12] A laminated film was obtained in the same manner as in Example 1, except that the resin composition used for the base layer was changed to polyester C [100 parts by mass] and porous silica particles [0.1 parts by mass]. The obtained laminated film had poor blocking resistance.

[Comparative Example 13] A laminated film was obtained in the same manner as in Example 1, except that the resin composition used for the base layer was changed to polyester D [100 parts by mass] and porous silica particles [0.1 parts by mass]. The obtained laminated film does not use recycled raw materials, so it is not suitable for the environment.

Table 4 shows the physical properties and various evaluation results of the laminated films obtained in the comparative examples.

[Table 4A] Unit Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Laminated film structure Substrate layer thickness μm 25 25 25 25 25 Isophthalic acid content Mole % 1.5 1.5 1.5 1.5 1.5 Extension ratio MD / TD times 3.5 / 4.0 3.5 / 3.5 4.0 / 3.5 3.5 / 4.0 3.5 / 4.0 TD extension method ━ Straight line Straight line Straight line Multi-segment extension Multi-segment extension TD stretching temperature Phase 1 ℃ 115 115 115 115 115 Phase 2 112 112 Phase 3 109 109 Anti-fog layer Coating agent ━ (A) (A) (A) (A) (A) thickness μm 2.0 2.0 2.0 0.2 3.2 Laminated film properties Fog % 3.9 5.5 5.1 1.9 7.1 Heat seal strength 120℃ N/15mm 4.0 4.3 4.3 1.5 7.8 140℃ 4.4 4.1 4.1 1.8 7.7 160℃ 4.4 5.1 4.9 1.3 7.8 180℃ 4.4 4.9 4.4 1.5 7.6 Water contact angle Spend 18 19 twenty two 53 twenty one Peel strength N/15mm 0.0 1.4 1.3 0.0 1.2 Impact strength J 0.71 0.44 0.55 0.63 0.76 Tear strength MD mN 201 222 121 222 225 TD 98 148 191 150 157 MD/TD ━ 2.05 1.50 0.63 1.48 1.43 Orientation coefficient ━ 0.52 0.98 1.24 0.77 0.77 Uneven thickness % 4.7 12.3 10.2 4.9 10.5 Uneven thickness of convex part % 1.5 7.7 6.9 2.2 6.4 Anti-fog evaluation ━ Y Y Y N Y Evaluation of ease of opening 120℃ ━ D A A B A 140℃ ━ D A A B A 160℃ ━ D A A B A 180℃ ━ D A A B A

[Table 4B] unit Comparative example 6 Comparative example 7 Comparative example 8 Comparative example 9 Comparative example 10 laminated film structure base material layer thickness μm 25 25 25 25 25 Amount of isophthalic acid Mol% 1.5 1.5 1.5 1.5 1.5 Extension ratio MD/TD times 3.5/4.0 3.5/4.0 3.5/4.0 3.5/4.0 3.5/4.0 TD extension method ━ Multiple extensions Multiple extensions Multiple extensions Multiple extensions Multiple extensions TD extension temperature first stage ℃ 115 115 115 115 115 second stage 112 112 112 112 112 The third stage 109 109 109 109 109 Anti-fog layer coating agent ━ (G) (H) (I) (J) (K) thickness μm 2.0 2.0 2.0 2.0 2.0 Laminated film physical properties Haze % 3.9 3.5 4.0 10.1 2.9 Heat seal strength 120℃ N/15mm 12.2 1.4 11.8 1.1 4.4 140℃ 12.2 1.4 12.5 1.2 5.5 160℃ 12.4 1.5 12.4 1.2 5.3 180℃ 13.1 1.1 12.5 0.7 5.3 water contact angle Spend twenty two twenty two twenty four 7 55 Peel strength N/15mm 0.0 1.1 0.0 0.2 0.7 Impact strength J 0.64 0.78 0.64 0.64 0.66 Tear strength MD mN 241 233 222 234 241 TD 166 160 152 166 166 MD/TD ━ 1.45 1.46 1.46 1.41 1.45 Alignment coefficient ━ 0.81 0.78 0.69 0.71 0.77 Uneven thickness % 6.1 9.1 7.9 6.0 6.6 Uneven thickness of convex portion % 2.3 4.6 3.8 2.5 3.0 Anti-fog evaluation ━ Y Y Y Y N Ease of opening evaluation 120℃ ━ C B A B A 140℃ ━ C B C B A 160℃ ━ C B C B A 180℃ ━ C B C B A

[Table 4C] Unit Comparative Example 11 Comparative Example 12 Comparative Example 13 Laminated film structure Substrate layer thickness μm 25 25 25 Isophthalic acid content Mole % 1.5 3.5 0 Extension ratio MD / TD times 3.5 / 4.0 3.5 / 4.0 3.5 / 4.0 TD extension method ━ Multi-segment extension Multi-segment extension Multi-segment extension TD stretching temperature Phase 1 ℃ 115 115 115 Phase 2 112 112 112 Phase 3 109 109 109 Anti-fog layer Coating agent ━ (L) (A) (A) thickness μm 2.0 2.0 2.0 Laminated film properties Fog % 3.3 3.3 4.1 Heat seal strength 120℃ N/15mm 1.1 4.4 4.6 140℃ 1.3 4.4 4.1 160℃ 1.9 4.1 4.3 180℃ 1.4 4.2 4.5 Water contact angle Spend twenty two 19 20 Peel strength N/15mm 1.9 1.8 0.4 Impact strength J 0.73 0.66 0.64 Tear strength MD mN 240 232 235 TD 167 166 162 MD/TD ━ 1.44 1.40 1.45 Orientation coefficient ━ 0.71 0.69 0.72 Uneven thickness % 8.4 10.4 6.0 Uneven thickness of convex part % 4.7 6.5 2.4 Anti-fog evaluation ━ Y Y Y Evaluation of ease of opening 120℃ ━ B A A 140℃ ━ B A A 160℃ ━ B A A 180℃ ━ B A A

[Fig. 1] A schematic diagram showing a linear extension pattern in the TD direction in the film manufacturing step. [Fig. 2] A schematic diagram showing a stretching pattern of multi-stage stretching in the TD direction in the film manufacturing step. [Fig. 3] A schematic diagram showing a logarithmic extension pattern in the TD direction in the film manufacturing step. [Fig. 4] A schematic diagram of the shape of an amorphous polyethylene terephthalate (A-PET) container used to evaluate ease of opening in the Examples. [Fig. 5] A diagram showing an example of the largest convex portion expressed when the film thickness is imaged.

Claims (14)

A laminate film comprises at least two layers, namely a substrate layer and an antifogging layer; (a) the antifogging layer of the laminate film is heat-sealed with an unstretched polyethylene terephthalate sheet having a thickness of 200 μm at 0.2 MPa for one second at temperatures of 120°C, 140°C, 160°C and 180°C, and the heat-sealing strength measured using a test piece having a width of 15 mm is from 2.0 N/15 mm to 12.0 N/15 mm; (b) 1 μL of distilled water is dripped onto the surface of the antifogging layer of the laminate film at 5°C and 50% relative humidity (RH), and the water contact angle measured after 5 seconds is less than 50°; (c) The impact strength in a pendulum impact test at 5°C is 0.5 J or more; (d) The tear strength at 5°C in both the MD direction and the TD direction of the aforementioned laminated film is 100 mN or more; (e) The thickness unevenness of the aforementioned laminated film in both the MD direction and the TD direction obtained by the calculation formula of the following formula (1) is less than 10%; Thickness unevenness (%) = (T _max - _{T min} ) / _Tave × 100 Formula (1); T _max : Maximum thickness of the laminated film; T _min : Minimum thickness of the laminated film; _Tave : Average thickness of the laminated film; (f) The aforementioned substrate layer comprises a recycled polyester resin, and the amount of isophthalic acid in the aforementioned substrate layer is greater than 0.5 mol % and less than 3.2 mol % relative to the total dicarboxylic acid units. In the case of a laminate film as described in claim 1, in which a sample having a length of 200 mm is cut out from the laminate film and the film thickness is imaged at intervals of 0.5 mm, in the thickness concave-convex pattern represented, the portion having the largest difference between the maximum thickness of the convex portion and the minimum thickness of the concave portion is set as the maximum convex portion. At this time, the thickness unevenness of the maximum convex portion obtained by the calculation formula of the following formula (2) in the MD direction and the TD direction is less than 6%; Thickness unevenness of the maximum convex portion (%) = (maximum thickness of the maximum convex portion - minimum thickness of the maximum convex portion) / T _ave × 100 Formula (2). A laminate film as claimed in claim 1 or 2, wherein the antifogging layer of the laminate film and the substrate layer of the laminate film are superimposed and left to stand for one week at 40°C under a load of 450 kgf/ ^m2 , and the peel strength measured using a test piece with a width of 15 mm is less than 1.0 N/15 mm. The multilayer film as claimed in claim 1 or 2, wherein the strength ratio of the tear strength in the MD direction to the tear strength in the TD direction of the multilayer film measured at 5°C (tear strength _MD /tear strength _TD ) is greater than 0.6 and less than 1.5. The laminated film according to claim 1 or 2, wherein the alignment coefficient of the aforementioned laminated film is 0.6 or more and 1.5 or less, as determined by using an Abbe refractometer and calculating the formula (3); Alignment coefficient = {Nx-(Ny+Nz)/2}/{Ny-(Nx+Nz)/2} Formula (3); Nx: refractive index in the MD direction of the film; Ny: refractive index in the TD direction of the film; Nz: refractive index in the thickness direction of the film. The laminated film as recited in claim 1 or 2, wherein the substrate layer is a biaxially aligned polyester film. The laminated film according to claim 1 or 2, wherein the anti-fog layer at least contains a polyester resin (A) with a glass transition temperature Tg of 0°C or more and 40°C or less and a glass transition temperature Tg of 41°C or more and 80°C. The following two types of polyester resin (B). The laminated film as claimed in claim 7, wherein in the resin constituting the antifogging layer, the mass ratio of the polyester resin (A) to the polyester resin (B) is polyester resin (A): polyester resin (B) = 50/50 to 90/10. The laminated film according to claim 7, wherein the anti-fog layer contains a nonionic surfactant. The laminate film as recited in claim 9, wherein the HLB value of the nonionic surfactant is greater than or equal to 3 and less than or equal to 10. For a laminated film as described in claim 1 or 2, the mist concentration of the laminated film is less than 10%. The laminated film according to claim 1 or 2 includes the adhesive layer, the base material layer and a printing layer. A cover material for food packaging containers, including the laminated film described in any one of claims 1 to 12. A food packaging container comprises a food packaging container cover as described in claim 13.

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