Antifogging sheet and food packaging container

Abstract

An antifogging sheet comprising a polymer sheet and an antifogging layer provided on one surface of the polymer sheet, wherein the antifogging layer contains a polyglycerol ester of fatty acid.

Description

Anti-fogging sheet and food packaging container

[0001] The present invention relates to an anti-fogging sheet and a food packaging container.

[0002] Food packaging containers, which consist of a container body made of a polymer sheet and a lid fitted together, are used as containers for selling food in stores such as supermarkets, convenience stores, and department stores. The lids of such food packaging containers are transparent so that the food inside the container can be seen. However, moisture contained in the food can adhere to the lid and form condensation, causing the lid to fog up and reduce visibility. For this reason, an anti-fogging layer is generally provided on the lid (or the sheet from which the lid is made) to impart anti-fogging properties.

[0003] For example, Patent Document 1 discloses an anti-fogging styrene-based transparent resin sheet characterized in that the surface of the styrene-based transparent resin sheet is treated with an anti-fogging agent containing 70 to 99% by mass of a sucrose laurate and 30 to 1% by mass of a sucrose stearate having an HLB of 12 or more.

[0004] Japanese Patent Application Laid-Open No. 2004-67955

[0005] When forming a lid, the sheet (raw sheet) that serves as the lid material is usually wound around a core material and set in the forming machine. However, static electricity can be generated in the raw sheet due to friction between the wound raw sheets. Because such static electricity generation poses a risk of producing defective products, antistatic treatment, such as applying an antistatic agent to the surface of the raw sheet opposite the surface on which the anti-fogging layer is provided, is performed as a countermeasure against static electricity. However, according to the inventors' studies, it is desirable that the anti-fogging layer itself also has antistatic properties. In contrast, the anti-fogging layer containing sucrose laurate as described in Patent Document 1 does not necessarily have antistatic properties, leaving room for improvement.

[0006] Therefore, one aspect of the present invention aims to provide an anti-fog sheet provided with an anti-fog layer having excellent antistatic properties.

[0007] The present inventors have found that an anti-fogging layer having excellent antistatic properties can be obtained by using a polyglycerol fatty acid ester in place of a sucrose laurate.

[0008] [1] An anti-fog sheet comprising a polymer sheet and an anti-fog layer provided on one surface of the polymer sheet, the anti-fog layer containing a polyglycerol fatty acid ester. [2] The anti-fog sheet according to [1], wherein the polyglycerol fatty acid ester has an HLB of 12 or more. [3] The anti-fog sheet according to [1] or [2], wherein the content of the polyglycerol fatty acid ester is 35 mass% or more based on the total mass of the anti-fog layer. [4] The mass per unit area of ​​the anti-fog layer is 10 mg / m or more. ２ 100mg / m or more ２ [5] The anti-fog sheet according to any one of [1] to [3], wherein the anti-fog layer further comprises a hydrophilic polymer other than the polyglycerol fatty acid ester, and the mass ratio of the content of the polyglycerol fatty acid ester to the content of the hydrophilic polymer is 50 / 50 or more and 60 / 40 or less. [6] The anti-fog sheet according to any one of [1] to [5], wherein the anti-fog layer further comprises a sucrose fatty acid ester, and the mass ratio of the content of the polyglycerol fatty acid ester to the content of the sucrose fatty acid ester is 80 / 20 or more and 99 / 1 or less. [7] The anti-fog sheet according to any one of [1] to [6], further comprising a release layer provided on the other surface of the polymer sheet and containing a release agent. [8] The anti-fog sheet according to any one of [1] to [7], wherein the polymer sheet is a biaxially oriented sheet of a styrene-based polymer. [9] A food packaging container formed from the anti-fogging sheet according to any one of [1] to [8].

[0009] According to one aspect of the present invention, it is possible to provide an anti-fog sheet provided with an anti-fog layer having excellent antistatic properties.

[0010] FIG. 1 is a schematic cross-sectional view showing one embodiment of an anti-fogging sheet.

[0011]

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. Fig. 1 is a schematic cross-sectional view showing one embodiment of an anti-fog sheet. As shown in Fig. 1, the anti-fog sheet 1 according to one embodiment includes a polymer sheet 2, an anti-fog layer 3 provided on one surface of the polymer sheet 2, and a release layer 4 provided on the other surface of the polymer sheet 2.

[0012] The polymer sheet 2 is a sheet formed of a polymer. The type of polymer is not particularly limited and may be appropriately selected from known polymers. In one embodiment, the polymer may be a styrene-based polymer containing a styrene-based monomer unit as a monomer unit.

[0013] The styrene-based polymer may be a styrene-based homopolymer containing only styrene-based monomer units as monomer units (e.g., general-purpose polystyrene (GPPS)), or may be a styrene-based copolymer containing styrene-based monomer units and other monomer units as monomer units.

[0014] Examples of the styrene-based monomer unit include units of styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, pt-butylstyrene, etc. The styrene-based monomer unit is preferably a styrene unit.

[0015] Examples of other monomer units contained in the styrene-based copolymer include units of (meth)acrylonitrile, (meth)acrylic acid, maleic anhydride, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate.

[0016] The styrene-based polymer is preferably a styrene-based copolymer. The styrene-based copolymer may be, for example, a copolymer consisting of styrene-based monomer units and (meth)acrylonitrile units. In this copolymer, the mass ratio of the (meth)acrylonitrile units to the styrene-based monomer units may be 12 / 88 or more, 16 / 84 or more, or 20 / 80 or more, and may be 38 / 62 or less, 34 / 66 or less, or 30 / 70 or less.

[0017] The styrene-based copolymer may be, for example, a copolymer consisting of styrene-based monomer units and (meth)acrylic acid units, in which the mass ratio of (meth)acrylic acid units to styrene-based monomer units may be 1 / 99 or more, 2 / 98 or more, or 3 / 97 or more, and may be 20 / 80 or less, 16 / 84 or less, or 12 / 88 or less.

[0018] The polystyrene-equivalent weight average molecular weight of the styrene-based polymer measured by the SEC method may be 100,000 or more, 130,000 or more, or 150,000 or more, and may be 250,000 or less, 220,000 or less, or 200,000 or less.

[0019] The content of the polymer (preferably a styrene-based polymer) in the polymer sheet 2 may be 97% by mass or more, 98% by mass or more, or 99% by mass or more, based on the total mass of the polymer sheet 2, and may be 99.9% by mass or less, 99.7% by mass or less, or 99.5% by mass or less.

[0020] The polymer sheet 2 may further contain a rubber-modified high impact polystyrene resin (HIPS). The content of the rubber-modified high impact polystyrene resin may be 0.1% by mass or more, 0.3% by mass or more, or 0.5% by mass or more, and may be 3% by mass or less, 2% by mass or less, or 1% by mass or less, based on the total mass of the polymer sheet 2.

[0021] The polymer sheet 2 may contain a biomass-derived component. The monomer units contained in the polymer may be biomass-derived components, or the polymer itself may be a biomass-derived component. For example, some or all of the styrene-based monomer units may be biomass-derived components. Furthermore, some or all of the monomer units contained in the polymer may be recycled monomer units, or the polymer itself may be a recycled polymer.

[0022] The polymer sheet 2 may further contain other components such as an ultraviolet absorber, a light stabilizer, an antioxidant, a lubricant, a plasticizer, a colorant, an antistatic agent, a flame retardant, a reinforcing fiber, and a filler.

[0023] The polymer sheet 2 is preferably a biaxially oriented sheet, more preferably a biaxially oriented sheet of the above-mentioned styrene-based polymer. The biaxially oriented sheet is obtained by melt-kneading a composition containing a polymer (preferably a styrene-based polymer) in an extruder, extruding the composition through a die (particularly a T-die), and then sequentially or simultaneously stretching the composition in two axial directions.

[0024] The thickness of the polymer sheet 2 (preferably a biaxially oriented sheet) may be 0.05 mm or more, 0.08 mm or more, or 0.1 mm or more, and may be 0.6 mm or less, 0.5 mm or less, or 0.4 mm or less.

[0025] The anti-fogging layer 3 contains a polyglycerol fatty acid ester. This provides an anti-fogging layer with superior antistatic properties compared to when, for example, sucrose laurate is used. The degree of polymerization of the polyglycerol constituting the polyglycerol fatty acid ester may be 2 or more, 4 or more, or 6 or more, and may be 16 or less, 14 or less, or 12 or less. The fatty acid constituting the polyglycerol fatty acid ester may be a saturated fatty acid or an unsaturated fatty acid. The number of carbon atoms of the fatty acid may be 10 or more and 18 or less. Specific examples of fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and linoleic acid.

[0026] Specific examples of polyglycerol fatty acid esters include diglycerol laurate, diglycerol stearate, diglycerol oleate, tetraglycerol laurate, tetraglycerol stearate, tetraglycerol oleate, hexaglycerol stearate, hexaglycerol oleate, decaglycerol laurate, decaglycerol stearate, and decaglycerol oleate.

[0027] The polyglycerol fatty acid ester preferably has an HLB (Hydrophilic-Lipophilic Balance) of 12 or more, from the viewpoint of obtaining an anti-fogging layer that is particularly excellent in antistatic properties as well as anti-fogging properties. In this specification, HLB refers to the HLB calculated by the Atlas method. The HLB of the polyglycerol fatty acid ester may be 13 or more, 14 or more, or 15 or more, or may be 20 or less, 19 or less, 18 or less, 17 or less, 16 or less, or 15 or less.

[0028] The HLB of polyglycerol fatty acid ester can be adjusted by the relative amount of hydrophilic group and hydrophobic group in polyglycerol fatty acid ester.Specifically, for example, when the carbon number of the fatty acid constituting polyglycerol fatty acid ester is increased, the relative amount of hydrophobic group in polyglycerol fatty acid ester is increased, so the HLB of polyglycerol fatty acid ester is reduced.On the contrary, when the carbon number of the fatty acid constituting polyglycerol fatty acid ester is reduced, the relative amount of hydrophobic group in polyglycerol fatty acid ester is reduced, so the HLB of polyglycerol fatty acid ester is increased.

[0029] When the anti-fog layer 3 contains a polyglycerol fatty acid ester (particularly a polyglycerol fatty acid ester having an HLB of 12 or more), the lubricity of the anti-fog sheet 1 tends to deteriorate. If the anti-fog sheet 1 has poor lubricity, for example, when the anti-fog sheet 1 is wound around a core and set in a molding machine to form a lid, the anti-fog layer 3 and the release layer 4, which come into contact with each other, stick to each other, making them difficult to slide, which may cause manufacturing problems.

[0030] From the viewpoint of suppressing the deterioration of lubricity as described above, the anti-fogging layer 3 preferably further contains a hydrophilic polymer other than polyglycerol fatty acid ester (hereinafter simply referred to as "hydrophilic polymer"). Examples of hydrophilic polymers include polyvinyl alcohol, polysaccharides, acrylic acid polymers or salts thereof, vinylpyrrolidone homopolymers or copolymers, and polyoxyethylene-polyoxypropylene copolymers. The hydrophilic polymer is preferably polyvinyl alcohol.

[0031] The degree of polymerization of polyvinyl alcohol may be 200 or more, and from the viewpoint of providing an excellent appearance of the anti-fog sheet 1 after long-term (e.g., 6 months) storage, is preferably 300 or more or 400 or more. The degree of polymerization of polyvinyl alcohol may be 2500 or less, and from the viewpoint of providing an excellent appearance of the anti-fog sheet 1, is preferably 2000 or less, 1500 or less, 1200 or less, 1000 or less, 900 or less, 800 or less, 700 or less, or 600 or less.

[0032] The saponification degree of the polyvinyl alcohol may be 78 mol% or more, and from the viewpoint of particularly excellent antifogging properties, preferably 80 mol% or more, 83 mol% or more, or 85 mol% or more. The saponification degree of the polyvinyl alcohol may be 99 mol% or less, and from the viewpoint of excellent appearance of the antifogging sheet 1, preferably 97 mol% or less, 96 mol% or less, or 95 mol% or less.

[0033] From the viewpoint of suppressing the deterioration of lubricity as described above, the anti-fogging layer 3 preferably further contains a sucrose fatty acid ester. The fatty acid constituting the sucrose fatty acid ester may be a saturated fatty acid or an unsaturated fatty acid. The number of carbon atoms in the fatty acid may be 6 or more, 8 or more, or 10 or more, and may be 30 or less, 28 or less, or 24 or less. The fatty acid is preferably a saturated fatty acid. Examples of saturated fatty acids include caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and montanic acid. The sucrose fatty acid ester is preferably sucrose stearyl acid ester.

[0034] The content of the polyglycerol fatty acid ester in the anti-fogging layer 3 may be 35% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more, based on the total mass of the anti-fogging layer 3, and may be 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less.

[0035] The content of the hydrophilic polymer in the anti-fogging layer 3 may be 25% by mass or more, 30% by mass or more, or 35% by mass or more, and may be 60% by mass or less, 55% by mass or less, or 50% by mass or less, based on the total mass of the anti-fogging layer 3.

[0036] The content of sucrose fatty acid ester in the anti-fogging layer 3 may be 1 mass% or more, 3 mass% or more, or 5 mass% or more, and may be 15 mass% or less, 12 mass% or less, or 9 mass% or less, based on the total mass of the anti-fogging layer 3.

[0037] The mass ratio of the polyglycerol fatty acid ester content to the hydrophilic polymer content in the anti-fogging layer 3 (polyglycerol fatty acid ester / hydrophilic polymer) may be 40 / 60 or more, and from the viewpoint of particularly excellent anti-fogging properties, is preferably 45 / 55 or more, 50 / 50 or more, or 51 / 49 or more. The mass ratio may be 70 / 30 or less, and from the viewpoint of suppressing deterioration of lubricity, is preferably 65 / 35 or less or 60 / 40 or less.

[0038] The mass ratio of the polyglycerin fatty acid ester content to the sucrose fatty acid ester content in the anti-fogging layer 3 (polyglycerin fatty acid ester / sucrose fatty acid ester) may be 75 / 25 or more, and is preferably 80 / 20 or more or 85 / 15 or more from the viewpoint of excellent appearance of the anti-fogging sheet 1. The mass ratio may be 99.5 / 0.5 or less, and is preferably 99 / 1 or less, 98 / 2 or less, or 97 / 3 or less from the viewpoint of suppressing deterioration of lubricity.

[0039] The amount of the anti-fogging layer 3 provided on the polymer sheet 2 can be appropriately set. The mass per unit area of ​​the anti-fogging layer 3 is 5 mg / m ２ From the viewpoint of excellent anti-fogging properties, it is preferably 10 mg / m ２ or more than 20 mg / m ２The mass per unit area of ​​the anti-fogging layer 3 is 110 mg / m ２ From the viewpoint of excellent appearance of the anti-fog sheet 1, it is preferably 100 mg / m ２ Below, 90mg / m ２ or less, or 80 mg / m ２ The following is the result.

[0040] The anti-fogging layer 3 is formed, for example, by applying an aqueous solution containing the above components (anti-fogging layer aqueous solution) to one surface (a surface that has been subjected to corona treatment as necessary) of the polymer sheet 2 and drying it. From the viewpoints of suppressing unevenness during application and improving coatability, the viscosity of the anti-fogging layer aqueous solution at 25°C (viscosity measured with a tuning fork vibro viscometer) may be 0.5 mPa·s or more, 0.7 mPa·s or more, or 0.9 mPa·s or more, and may be 2.0 mPa·s or less, 1.8 mPa·s or less, or 1.5 mPa·s or less.

[0041] The release layer 4 contains a release agent. The release agent may be appropriately selected from known release agents. The release agent may be, for example, silicone. The silicone may be, for example, a silicone having a viscosity of 1,000 to 30,000 mm at 23°C. ２ Silicone of the formula (I) / s can be used.

[0042] The release layer 4 may further contain an anionic surfactant. When the release layer 4 contains an anionic surfactant, the antistatic properties of the surface of the anti-fog sheet 1 on the release layer 4 side are improved. Examples of anionic surfactants include alkyl ether carboxylates, alkyl sulfonates, α-sulfofatty acid methyl ester salts, alkyl sulfate ester salts, and phosphate ester salts.

[0043] The amount of the release layer 4 provided on the polymer sheet 2 can be set appropriately. The mass per unit area of ​​the release layer 4 is 3 mg / m ２ Above, 4mg / m ２ or more, or 5 mg / m ２ or more, and ２ Below, 25mg / m ２ or less than 20 mg / m ２ It may be the following:

[0044] The release layer 4 is formed, for example, by applying an emulsion containing the above components onto the other surface of the polymer sheet 2 and drying it.

[0045] In the embodiment described above, the anti-fog sheet 1 is composed of three layers including the release layer 4, but in another embodiment, the anti-fog sheet may not have a release layer. The anti-fog sheet according to another embodiment may be composed of two layers, for example, a polymer sheet and an anti-fog layer provided on one surface of the polymer sheet.

[0046] The anti-fog sheet described above can be used for molded articles such as packaging containers by molding. In the case of a packaging container, it is preferable that the surface of the anti-fog layer side of the anti-fog sheet is the surface that comes into contact with the contents of the container. As a molded article, a food packaging container (i.e., a packaging container containing food as its contents) is suitable, and a lid for a food packaging container is particularly suitable. As a method for obtaining a molded article from the anti-fog sheet, hot plate molding using a commercially available general hot plate compressed air molding machine is preferably used.

[0047] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0048] [Preparation of Anti-Fog Sheet] (Example 1) An anti-fogging sheet was prepared by the following procedure. First, a styrene-based polymer (general-purpose polystyrene (GPPS) manufactured by Toyo Styrene Co., Ltd.) was extruded using a sheet extruder (a T-die width of 500 mm and a diameter of 40 mm extruder manufactured by Tanabe Plastic Machinery Co., Ltd.) to obtain a sheet. This sheet was stretched using a batch-type biaxial stretching machine (manufactured by Ever Sokki Co., Ltd.) to obtain a polymer sheet (biaxially stretched sheet of styrene-based polymer, thickness: 0.25 mm).

[0049] Furthermore, an aqueous solution for an anti-fogging layer was prepared containing 0.7% by mass of polyglycerol fatty acid ester 1 (HLB: 15, Poem J-0021, manufactured by Riken Vitamin Co., Ltd.), 0.5% by mass of polyvinyl alcohol (PVA1, degree of polymerization: 500, degree of saponification: 88 mol%), and 0.08% by mass of sucrose stearate (S-1570, manufactured by Mitsubishi Chemical Corporation).

[0050] One surface of the polymer sheet was subjected to a corona treatment to adjust the temperature to 52 dyne, and the aqueous solution for the anti-fogging layer was applied to the corona-treated surface at a concentration of 5 g / m using a bar coater. ２ The anti-fog layer was formed on one surface of the polymer sheet by applying the anti-fog layer in an amount of 50 mg / m² and then drying the applied anti-fog layer in an oven at 70°C for 5 minutes. The mass per unit area of ​​the anti-fog layer was 50 mg / m² as shown in Table 1. ２ It was.

[0051] Subsequently, an aqueous solution of silicone emulsion (SM7025EX, manufactured by Dow Corning Toray Co., Ltd.) with a solid content concentration of 0.2% by mass was applied at a concentration of 5 g / m using a bar coater onto the other surface of the polymer sheet (the surface on which the anti-fogging layer was not formed). ２ After that, the sheet was dried in an oven at 70°C for 5 minutes to form a release layer on the other surface of the polymer sheet. The mass per unit area of ​​the release layer was 10 mg / m ２ It was.

[0052] (Examples 2 to 3 and Comparative Example 1) Anti-fog sheets were prepared in the same manner as in Example 1, except that polyglycerin fatty acid ester 1 was replaced with polyglycerin fatty acid ester 2 (HLB: 13), polyglycerin fatty acid ester 3 (HLB: 5.6), or sucrose laurate as shown in Table 1.

[0053] Examples 4 to 11 Anti-fog sheets were prepared in the same manner as in Example 1, except that the composition of the anti-fog layer (% by mass based on the total mass of the anti-fog layer) was changed as shown in Tables 2 and 3.

[0054] (Examples 12 to 15) Anti-fog sheets were prepared in the same manner as in Example 1, except that the mass per unit area of ​​the anti-fog layer was changed as shown in Table 4 by adjusting the coating amount of the aqueous solution for the anti-fog layer.

[0055] (Examples 16 to 21) Anti-fog sheets were produced in the same manner as in Example 1, except that one of the following polyvinyl alcohols (PVA2 to PVA7) was used instead of polyvinyl alcohol (PVA1) as shown in Table 5. PVA2 (degree of polymerization: 500, degree of saponification: 78 mol%) PVA3 (degree of polymerization: 500, degree of saponification: 85 mol%) PVA4 (degree of polymerization: 500, degree of saponification: 95 mol%) PVA5 (degree of polymerization: 500, degree of saponification: 99 mol%) PVA6 (degree of polymerization: 200, degree of saponification: 88 mol%) PVA7 (degree of polymerization: 2500, degree of saponification: 88 mol%)

[0056] [Evaluation of Anti-Fog Sheets] The anti-fogging sheets of the Examples and Comparative Examples obtained as described above were evaluated as follows. The results are shown in Tables 1 to 5.

[0057] (Antistatic property) The half-life (unit: sec) of the anti-fog layer side of the anti-fog sheet was measured according to the half-life measurement method of JIS L 1094. The shorter the half-life, the better the antistatic property.

[0058] (Slipperiness) A pair of test pieces was cut out from the anti-fog sheet, and the inclination angle (angle at which sliding begins, unit: deg) was measured in accordance with the inclination method of JIS P8147 "Paper and paperboard -- Determination of static and dynamic coefficients of friction" with the surface of one test piece facing the anti-fog layer and the surface of the other test piece facing the release layer in contact with each other. A smaller inclination angle indicates better slipperiness.

[0059] (Appearance) The haze of the anti-fog sheet was measured using a haze meter NDH5000 (Nippon Denshoku Co., Ltd.) in accordance with JIS K7136. The appearance was evaluated according to the measured haze value using the following criteria: A: Haze less than 1.5% B: Haze 1.5% or more but less than 3.0% C: Haze 3.0% or more

[0060] (Appearance after storage) The anti-fog sheet was wound up and stored in a roll state at 23°C for 6 months. The haze of the anti-fog sheet after storage was measured using a haze meter NDH5000 (Nippon Denshoku Co., Ltd.) in accordance with JIS K7136. The appearance was evaluated according to the measured haze value using the following criteria: A: Haze less than 1.5% B: Haze 1.5% or more but less than 3.0% C: Haze 3.0% or more

[0061] (Anti-fogging properties) Using a hot plate molding machine HPT-400A (manufactured by Wakisaka Engineering), a lid (dimensions: length 241 mm x width 193 mm x height 28 mm) was molded from the anti-fogging sheet under conditions of a hot plate temperature of 135°C and a heating time of 2.0 seconds. A container capable of fitting the obtained lid was prepared, and 100 g of 95°C water was placed in the container, followed by the lid and leaving it at 23°C for 10 minutes. After leaving it, the contents (water) of the container were visually observed through the lid, and the anti-fogging properties were evaluated according to the visibility according to the following criteria. A: The contents can be clearly seen. B: Due to dew on the lid, the contents are more difficult to see than in "A" above. C: There was more dew on the lid than in "B" above, and the contents were not necessarily sufficiently visible.

[0062] (Contact Angle of Water) In accordance with JIS R3257, a contact angle meter DM-701 (Kyowa Interface Science) was used to measure the contact angle of water (unit: deg) 30 seconds after 2 μL of distilled water was dropped on the surface of the anti-fog layer side of the anti-fog sheet.

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] 1...anti-fogging sheet, 2...polymer sheet, 3...anti-fogging layer, 4...release layer

Claims

1. An anti-fog sheet comprising: a polymer sheet; and an anti-fog layer provided on one surface of the polymer sheet, the anti-fog layer comprising a polyglycerol fatty acid ester.

2. The anti-fogging sheet according to claim 1, wherein the HLB of the polyglycerol fatty acid ester is 12 or more.

3. The anti-fog sheet according to claim 2, wherein the content of the polyglycerol fatty acid ester is 35 mass% or more based on the total mass of the anti-fog layer.

4. The mass per unit area of ​​the anti-fogging layer is 10 mg / m ２ 100mg / m or more ２ The anti-fog sheet according to claim 1, wherein:

5. The anti-fogging sheet according to claim 1, wherein the anti-fogging layer further contains a hydrophilic polymer other than the polyglycerol fatty acid ester, and the mass ratio of the content of the polyglycerol fatty acid ester to the content of the hydrophilic polymer is 50 / 50 or more and 60 / 40 or less.

6. The anti-fogging sheet according to claim 5, wherein the anti-fogging layer further contains a sucrose fatty acid ester, and the mass ratio of the content of the polyglycerin fatty acid ester to the content of the sucrose fatty acid ester is 80 / 20 or more and 99 / 1 or less.

7. The anti-fog sheet according to claim 1, further comprising a release layer provided on the other surface of the polymer sheet and containing a release agent.

8. The anti-fog sheet according to any one of claims 1 to 7, wherein the polymer sheet is a biaxially oriented sheet of a styrene-based polymer.

9. A food packaging container formed from the anti-fogging sheet according to claim 8.

Images