Antibacterial sheet and its use

Abstract

To provide an antibacterial sheet capable of efficiently dispersing an antibacterial component to an entire inside of a hermetically sealable food container such as a lunch box and its usage.SOLUTION: An antibacterial sheet comprises an antibacterial layer containing an antibacterial component such as AITC, a first surface layer capable of sustainably releasing the antibacterial component, and a second surface layer capable of sustainably releasing the antibacterial component, in which a release amount per a unit time of the antibacterial component from the first surface layer is larger than the release amount per a unit time of the antibacterial component from the second surface layer. In a food container that houses a food in a container body and is hermetically sealed with a lid, the antibacterial sheet is arranged such that the first surface layer faces the lid body, and the second surface layer faces the food. Since an antibacterial action can be surely applied to the food in a region distanced from the antibacterial sheet, without contacting the antibacterial sheet to an entire surface of the food, it is possible to apply the antibacterial action to an entire food and can maintain a hygiene state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an antibacterial sheet and a method for using the same, and more particularly to an antibacterial sheet used to prevent food spoilage in a sealable food container such as a lunch box, and a method for using the same. [Background technology]

[0002] In recent years, an increasing number of people are bringing their own lunches to school or work for nutritional and economic reasons. When a lunch box is prepared in the morning and eaten at lunchtime, the food is placed in a sealable food container such as a lunch box and left out for several hours before lunchtime. Therefore, if the food is left in an environment with high temperatures and humidity, especially in the summer, there is a high risk of bacteria and mold growing and spoiling the food by the time it is eaten.

[0003] For these reasons, technologies have been proposed that take into consideration the hygiene of food stored in containers at room temperature. For example, Patent Document 1 describes an antibacterial sheet in which a gas-impermeable layer is provided on one side of a kneaded layer of an antibacterial volatile agent and a kneading resin, and a gas permeation control layer that restricts the permeation of volatile gases is provided on the other side. In the examples of Patent Document 1, allyl isothiocyanate, a component of mustard, is used as the antibacterial volatile agent, a biaxially oriented polyester film is used for the gas-impermeable layer, and a biaxially oriented polypropylene film is used for the gas permeation control layer. When using this antibacterial sheet, by placing it on top of food with the gas permeation control layer (biaxially oriented polypropylene film) facing, the antibacterial gas is controlled to be released slowly only from the side that comes into contact with the food, which is said to prevent spoilage of the food. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-171208 Summary of the Invention [Problem to be solved by the invention]

[0005] The antibacterial sheet of Patent Document 1 can exert antibacterial effects on the areas that come into contact with food and the areas nearby, but the antibacterial components do not reach areas away from the antibacterial sheet sufficiently, resulting in inferior antibacterial performance. Furthermore, lunch boxes come in a variety of sizes, and to ensure versatility that can accommodate all sizes, the dimensions of the antibacterial sheet cannot be made too large. For this reason, the above-mentioned problems are likely to occur when the sheet is used in lunch boxes with a large volume.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide an antibacterial sheet that can efficiently diffuse antibacterial components throughout the interior of a sealable food container such as a lunch box, and a method for using the same. [Means for solving the problem]

[0007] In order to achieve the above object, the invention described in claim 1 is as follows: An antibacterial sheet for use in a food container having a container body and a lid, in which food is contained in the container body and sealed by the lid, an antibacterial layer containing a volatile antibacterial component; and a film provided on one side of the antibacterial layer, Facing the lid body, a first surface layer capable of gradually releasing an antibacterial component, and a second surface layer provided on the other side of the antibacterial layer; Facing the food, and a second surface layer capable of sustained release of an antibacterial component; The first surface layer and the second surface layer are formed of biaxially oriented polypropylene, the thickness of the first surface layer is thinner than the thickness of the second surface layer, and the antibacterial layer contains allyl isothiocyanate as an antibacterial component at 200 to 1000 mg / m 2 the thickness of the first surface layer is 10 μm to 30 μm, the thickness of the second surface layer is 20 μm to 60 μm, and the thickness ratio of the first surface layer to the second surface layer is 1 / 6 to 6 / 7; The amount of the antibacterial component released per unit time from the first surface layer is greater than the amount of the antibacterial component released per unit time from the second surface layer. The sum of the surface area of ​​the first surface layer and the surface area of ​​the second surface layer per unit volume of the food container is 6 to 24 mm 2 / mL range is.

[0008] With this configuration, the antibacterial component is gradually released from both the first surface layer and the second surface layer. The antibacterial component is released in a larger amount from the first surface layer than from the second surface layer. Furthermore, since both the first surface layer and the second surface layer are made of biaxially oriented polypropylene, the antibacterial component can be gradually released from both layers. Since the first surface layer is thinner than the second surface layer, the amount of the antibacterial component released per unit time is greater than that from the second surface layer. Furthermore, allyl isothiocyanate is released as the antibacterial component in an amount of 200 to 1000 mg / m 2 Since it contains the antibacterial agent, it reliably exerts antibacterial effects without impairing the flavor of food. Since the thickness ratio between the first surface layer and the second surface layer is within a specified range, the amount of antibacterial component released per unit time is greater than that of the second surface layer. The antibacterial sheet has a total thickness of the first surface layer and the second surface layer in the range of approximately 30 to 90 μm. Furthermore, the antibacterial component released from the first surface layer diffuses through the space between the surface of the food and the lid. The antibacterial component released from the second surface layer reaches the food in the vicinity of the antibacterial sheet directly. It exerts a suitable antibacterial effect without impairing the flavor of food. The antibacterial component release area per unit volume of the food container is 6 mm 2 If the concentration is less than 24 mm / mL, the antibacterial component release area may not be adequately effective. 2 If the concentration exceeds 100mg / mL, the antibacterial component may be released in excess, which may transfer to food and impair its flavor. 。

[0013] Claim 2 The invention described is 1st article In the configuration of the above invention, the thickness of the first surface layer is 15 μm to 25 μm, the thickness of the second surface layer is 30 μm to 50 μm, and the ratio of the thickness of the first surface layer to the thickness of the second surface layer is 1 / 3 to 2 / 3.

[0014] With this configuration, the ratio of the thickness of the first surface layer to the second surface layer falls within a predetermined range, so that the amount of antibacterial component released per unit time is greater than that of the second surface layer.The total thickness of the first surface layer and the second surface layer is in the range of approximately 45 to 75 μm, resulting in an antibacterial sheet. [Effects of the Invention]

[0019] In the invention described in claim 1, the antibacterial component released from the first surface layer is released in a large amount, thereby enabling the antibacterial effect of the antibacterial component released from the first surface layer to be wider than the antibacterial effect of the antibacterial component released from the second surface layer. Furthermore, since the first and second surface layers are made of the same material, the amount of antibacterial component released can be controlled by controlling the thickness of these layers. Furthermore, an antibacterial sheet with the required strength, ease of handling, and high safety can be provided. Furthermore, the antibacterial component released from the second surface layer directly exerts its antibacterial effect on food in the area close to the antibacterial sheet. The antibacterial component released and diffused from the first surface layer exerts its antibacterial effect on food in areas distant from the antibacterial sheet. By setting the release amount of the antibacterial component released from the first surface layer to a moderately large amount per unit time, the antibacterial effect can be reliably exerted on food in areas distant from the antibacterial sheet. This allows the antibacterial effect to be exerted on the entire food, maintaining hygiene, even without the antibacterial sheet contacting the entire surface of the food. As a result, the antibacterial sheet does not need to be large in size, making it highly versatile for food containers of different internal volumes. 2 / mL range, it is possible to obtain a reliable antibacterial effect while avoiding the antibacterial ingredients from impairing the flavor of food. 。

[0022] Claim 2 The invention described is 1st article In addition to the effects of the above-mentioned invention, an antibacterial sheet that is easier to handle can be provided. [Brief explanation of the drawings]

[0025] [Figure 1] 1A and 1B are diagrams showing an antibacterial sheet according to an embodiment of the present invention, in which (A) is a plan view and (B) is a front view. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a portion of the antibacterial sheet of FIG. 1. [Figure 3] Figures explaining how to use an antibacterial sheet according to an embodiment of the present invention, where (A) is a cross-sectional view showing the capacity of placing an antibacterial sheet in a food container (lunch box) with food stored in the container body, and (B) is a cross-sectional view showing the situation in which the antibacterial sheet exerts its antibacterial effect inside a sealed food container. DETAILED DESCRIPTION OF THE INVENTION

[0026] Figure 1 shows an antibacterial sheet according to an embodiment of the present invention, where (A) is a plan view and (B) is a front view, Figure 2 is an enlarged cross-sectional view of a portion of the antibacterial sheet of Figure 1, and Figure 3 is a view explaining how to use the antibacterial sheet according to an embodiment of the present invention, where (A) is a cross-sectional view showing the capacity of the antibacterial sheet when placed in a food container (lunch box) with food stored in the container body, and (B) is a cross-sectional view showing the situation in which the antibacterial sheet exerts its antibacterial effect inside a sealed food container.

[0027] The antibacterial sheet 10 of the present invention is used to exert an antibacterial effect on the entire food 5 contained in a sealable food container 1 such as a lunch box, thereby inhibiting the growth of bacteria and mold.

[0028] The antibacterial sheet 10 in this example has a three-layer structure comprising an antibacterial layer 20 containing an antibacterial component, a first surface layer 11 provided on one side of the antibacterial layer 20, and a second surface layer 12 provided on the other side of the antibacterial layer 20.

[0029] The antibacterial layer 20 is a layer containing a volatile antibacterial component. Examples of the antibacterial component that can be used include isothiocyanate esters such as allyl isothiocyanate (hereinafter referred to as "AITC"), eucalyptus oil, menthol, rosemary, and hinokitiol. AITC, in particular, is known as a component of wasabi and mustard, and is considered to have low toxicity to the human body, making it suitable as an antibacterial component for food.

[0030] The antibacterial layer 20 is formed from a resin material kneaded with the antibacterial component. The resin material to be kneaded should be one that can be kneaded with the antibacterial component and is permeable to the gas volatilized from the antibacterial component. Examples of such resin materials include rosin, rosin ester, modified products thereof, and urethane resin. In particular, the use of rosin, rosin ester, or modified products thereof reduces the viscosity of the kneaded mixture, allowing it to be kneaded at a relatively low temperature, resulting in advantages such as reduced drug loss and easier coating.

[0031] When AITC is used as the antibacterial component, the preferred content of AITC in the antibacterial layer 20 is 1 / m of the antibacterial sheet. 2 The AITC content is preferably set in the range of 30 to 6000 mg per m², more preferably in the range of 200 to 1000 mg per m². 2 If the concentration is less than 6000mg / m, the antibacterial effect may be insufficient. 2 If the AITC exceeds this limit, it may impair the flavor of the food.

[0032] If necessary, an antioxidant may be added to the resin material forming the antibacterial layer to improve the stability of the antibacterial component. Examples of antioxidants that can be used include BHT (dibutylhydroxytoluene) and vitamin C (L-ascorbic acid).

[0033] The first surface layer 11 and the second surface layer 12 are both made of a material that has the property of allowing the antibacterial component to be gradually released from the antibacterial layer 20. Examples of such materials include polyethylene film, unstretched polypropylene film, and biaxially oriented polypropylene film (hereinafter abbreviated as "OPP").

[0034] One method for manufacturing the antibacterial sheet 10 configured as described above is to coat one side of the first surface layer 11 (or second surface layer 12) with a resin material kneaded with an antibacterial component to form the antibacterial layer 20, then laminate the second surface layer 12 (or first surface layer 11) on top of this antibacterial layer 20, and then cure the resin component of the antibacterial layer 20 to integrate the entire layer. If necessary, a printed layer may be provided between the first surface layer 11 or second surface layer 12 and the antibacterial layer 20, or on the first surface layer 11 or second surface layer itself, to display a design such as letters or figures. Furthermore, an adhesive layer or a release film may be provided on the surface of the antibacterial sheet 10.

[0035] The antibacterial sheet 10 of this example is characterized in that it is configured so that the amount of antibacterial component released per unit time from the first surface layer 11 is greater than the amount of antibacterial component released per unit time from the second surface layer 12. To achieve this configuration, the first surface layer 11 and the second surface layer 12 can be made of different materials, or if made of the same material, can be made to have different thicknesses. That is, the amount of antibacterial component released can be increased by reducing the layer thickness. For example, when both the first surface layer 11 and the second surface layer 12 are made of OPP, it is preferable that the thickness d1 of the first surface layer 11 be 10 μm to 30 μm, the thickness d2 of the second surface layer 12 be 20 μm to 60 μm, and the ratio d1 / d2 of the thickness d1 of the first surface layer 11 to the thickness d2 of the second surface layer be set in the range of 1 / 6 to 6 / 7. More preferably, the thickness d1 of the first surface layer 11 is 15 μm to 25 μm, the thickness d2 of the second surface layer 12 is 30 μm to 50 μm, and the thickness ratio d1 / d2 of the first surface layer 11 to the second surface layer 12 is set in the range of 1 / 3 to 2 / 3. The thickness d3 of the antibacterial layer 20 is preferably in the range of 5 to 30 μm, and more preferably in the range of 10 to 15 μm.

[0036] When the first and second surface layers are made of the same material, the release amount of the antibacterial component can be controlled by adjusting the ratio of the thicknesses of these layers. Furthermore, when the thicknesses of the layers are set as described above, an antibacterial sheet product can be provided that is easy to handle and has the necessary strength.

[0037] Next, a method of using the antibacterial sheet 10 will be described with reference to Figure 3. As shown in the figure, a food container 1 is assumed to have a lid 2 and a container body 3, with food 5 contained in the container body 3 and sealed with the lid 2. Here, a food container 1 with a width dimension larger than its depth, such as a typical lunch box, is recommended. For such a food container 1, as shown in Figure 3(A), the antibacterial sheet 10 is placed on top of the food 5 so that the first surface layer 11 faces the lid 2 and the second surface layer 12 faces the food 5. Then, as shown in Figure 3(B), the lid 2 is closed with the antibacterial sheet 10 placed on the food 5, sealing the food container 1.

[0038] When left in this state, the antibacterial component of the antibacterial layer is released from both the first surface layer 11 and the second surface layer 12. The antibacterial component released from the first surface layer 11 diffuses through the space between the lid 2 and the surface of the food 5. The antibacterial component released from the second surface layer 12 reaches the food 5 directly near the antibacterial sheet 10. In this example, the amount of antibacterial component released per unit time from the first surface layer 11 is set to be greater than the amount of antibacterial component released per unit time from the second surface layer 12. This increases the reach of the antibacterial component released from the first surface layer 11, ensuring that the antibacterial effect is exerted on food 5 in areas far from the antibacterial sheet 10. On the other hand, the antibacterial effect can be exerted directly on food 5 in areas closer to the antibacterial sheet 10 by the antibacterial component released from the second surface layer 12, ensuring the antibacterial effect even when the amount of antibacterial component released per unit time is smaller than that from the first surface layer 11. Because of this effect, the antibacterial sheet of this example can exert an antibacterial effect on the entire food even though it has a small surface area, making it possible to suppress the growth of bacteria and mold and maintain good hygiene.As a result, an antibacterial sheet with a small surface area can be used for food containers with a large capacity, making it highly versatile.

[0039] The antibacterial sheet 10 of this example gradually releases antibacterial components from both the first and second surface layers, and therefore exhibits excellent antibacterial effects even in relatively small dimensions. However, to efficiently exert the antibacterial effect of the antibacterial sheet inside a food container, it is preferable to set the relationship between the antibacterial component release area of ​​the antibacterial sheet and the capacity of the food container within a specific range. Specifically, if the antibacterial component release area of ​​the antibacterial sheet is defined as the sum of the surface area of ​​the first surface layer and the surface area of ​​the second surface layer, the value of the antibacterial component release area per unit capacity of the food container (antibacterial component release area mm 2 / Food container capacity (mL) 6~24mm 2 / mL, particularly preferably 10 to 15 mm 2 / mL, the above value is within 6mm 2 If the concentration is less than 24 mm / mL, the antibacterial effect may not be satisfactory. 2If the concentration exceeds 1 / mL, the amount of antibacterial component released will be excessive, which may impair the flavor of the food. By setting the antibacterial component release area per unit volume of the food container within the above range, it is possible to exert an antibacterial effect on the entire food without the antibacterial sheet being sized to cover the entire surface of the food contained in the food container, and there is no risk of impairing the flavor of the food.

[0040] Furthermore, if an antibacterial sheet is left in an open space when not in use, the antibacterial component will be released into the air over time, which may cause the sheet to lose its antibacterial function when in use. Therefore, when not in use, it is desirable to store the antibacterial sheet in an aluminum pouch bag, for example, made by laminating aluminum foil and resin film and sealing it with a zipper or chuck, to prevent the release of the antibacterial component. If stored in this way, the antibacterial sheet can be easily removed when in use, allowing it to be used immediately in a lunch box or the like. [Example]

[0041] <Production of antibacterial sheets> First, a resin material for forming the antibacterial layer was prepared by kneading a rosin ester resin with AITC as an antibacterial component and a small amount of antioxidant. The AITC content was 530 mg / m 2 The thickness was adjusted to be 12 μm. Next, one side of a 20 μm thick OPP film (first surface layer) was coated with this resin material to a thickness of 12 μm to form an antibacterial layer. Next, a 40 μm thick OPP film (second surface layer) was laminated on the surface of this antibacterial layer to produce an antibacterial sheet raw roll with an antibacterial layer laminated in the middle. This antibacterial sheet raw roll was cut to a sheet size of 45 mm × 60 mm or 90 mm × 60 mm to obtain the desired antibacterial sheets. The antibacterial sheet cut to a size of 45 mm × 60 mm was designated Example 1, and the antibacterial sheet cut to a size of 90 mm × 60 mm was designated Example 2. The antibacterial component release area of ​​the antibacterial sheet of Example 1 was 5,400 mm 2 The antibacterial component release area of ​​the antibacterial sheet of Example 2 is 10,800 mm 2 This becomes: <Antibacterial test> (Preparation of specimen) In addition to Examples 1 and 2, the same antibacterial layer as in Examples 1 and 2 was used, but the thickness of the OPP film forming the first surface layer and second surface layer was changed as shown in Table 1. Antibacterial sheet raw rolls were produced in the same manner as in Examples 1 and 2, and these were cut to a size of 45 mm x 60 mm to provide the antibacterial sheets of Examples 3 to 5 and Reference Examples 1 and 2. Next, an antibacterial sheet raw roll was produced in the same manner as in Example 1, except that a 25 μm thick PET film was used for the first surface layer instead of the OPP film, and this antibacterial sheet raw roll was cut to a size of 45 mm x 60 mm to provide the antibacterial sheet of Comparative Example 1.

[0042] [Table 1] (E. coli culture test) The cultured E. coli was collected and suspended in sterilized water. An equal amount of this E. coli suspension was spread onto XM-G agar medium (manufactured by Nissui Pharmaceutical Co., Ltd.) filled into a petri dish, and multiple petri dishes were prepared. Additionally, multiple lunch boxes with a capacity of 450 mL and a capacity of 950 mL, each equipped with a sealable lid and container body, were prepared as food containers.

[0043] The antibacterial sheets of Examples 1, 3-5, Reference Examples 1 and 2, and Comparative Example 1 were attached to the backside of the lid of a 450 mL lunch box. Meanwhile, the antibacterial sheet of Example 2 was attached to the backside of the lid of a 900 mL lunch box. The antibacterial sheet was attached to the lid by placing the first surface layer facing the lid and attaching the antibacterial sheet to the backside of the lid with 5 mm-wide double-sided tape attached to both ends of the short side of the first surface layer. Additionally, 450 mL and 900 mL lunch boxes without an antibacterial sheet attached to the lid were prepared as blanks (Comparative Examples 2 and 3). Table 2 shows the antibacterial component release area per unit volume of the lunch box for the antibacterial sheets of Examples 1-5, Comparative Example 1, and Reference Examples 1 and 2.

[0044] [Table 2] (Test Method) The petri dishes coated with the E. coli suspension on the agar medium were placed in the containers of each lunch box prepared as described above, then sealed with lids. The occurrence of E. coli was visually confirmed after 9 and 18 hours at 37°C. XM-G agar medium is a medium specifically for E. coli, and when E. coli grows and forms colonies, it turns blue (blue to blue-purple). Therefore, antibacterial properties can be evaluated by visually checking the number of colonies and their growth status. The evaluation results are shown in Table 3.

[0045] [Table 3] The test results shown in Table 3 confirm that the antibacterial sheets of Examples 1 to 5 of the present invention exhibit good antibacterial effects. Comparative Example 1 and Reference Examples 1 and 2 also exhibit antibacterial effects, but compared to the Examples of the present invention, the colony formation status after a long period of time shows that there are differences in the durability of the antibacterial action. That is, the results of Comparative Example 1 show that antibacterial performance decreases when the first surface layer does not have the function of releasing antibacterial components. Comparison with Reference Examples 1 and 2 shows that antibacterial performance decreases when the layer thickness ratio between the first surface layer and the second surface layer deviates from the specified range.

[0046] In the above embodiment, the antibacterial sheet has a rectangular shape in plan view, but it may have any shape such as a square, circle, or oval.

[0047] One or both of the first surface layer and the second surface layer may be made of a material other than OPP, such as a non-oriented polypropylene film, which has sustained release properties for the antibacterial component.

[0048] The antibacterial layer may be formed by using a resin material containing an antibacterial component, or by directly coating an antibacterial agent on either the first surface layer or the second surface layer.

[0049] The food containers that can be used are not limited to lunch boxes, but can also be multi-tiered boxes, plastic containers with lids for selling food, or any container that can hold food and is sealed with a lid.

[0050] The antibacterial sheet can be used by placing it on the surface of the food contained in the container or by attaching it to the backside of the lid. In this case, it is recommended to apply double-sided tape to the surface of the first surface layer in advance.

[0051] For large-capacity food containers, a large-sized antibacterial sheet may be used, but multiple small-sized antibacterial sheets may also be used. [Explanation of symbols]

[0052] 1...Food container 2...Lid 3...Container body 5...Food 10...Antibacterial sheet 11...First surface layer 12...Second surface layer 20…Antibacterial layer d1: Thickness of the first surface layer d2: Thickness of the second surface layer d3: Antibacterial layer thickness In addition, the same reference numerals in each drawing indicate the same or corresponding parts.

Claims

1. An antibacterial sheet for use in a food container having a container body and a lid, in which food is contained in the container body and sealed by the lid, an antibacterial layer containing a volatile antibacterial component; a first surface layer provided on one surface of the antibacterial layer, facing the lid, and capable of gradually releasing the antibacterial component; a second surface layer provided on the other side of the antibacterial layer, facing the food, and capable of slowly releasing the antibacterial component; the first surface layer and the second surface layer are formed of biaxially oriented polypropylene; the thickness of the first surface layer is smaller than the thickness of the second surface layer; The antibacterial layer contains allyl isothiocyanate as an antibacterial component at a concentration of 200 to 1000 mg / m ２ Contains the thickness of the first surface layer is 10 μm to 30 μm; the thickness of the second surface layer is 20 μm to 60 μm; a thickness ratio of the first surface layer to the second surface layer is 1 / 6 to 6 / 7; the amount of the antibacterial component released per unit time from the first surface layer is greater than the amount of the antibacterial component released per unit time from the second surface layer; The sum of the surface area of ​​the first surface layer and the surface area of ​​the second surface layer per unit volume of the food container is 6 to 24 mm ２ / mL range, Antibacterial sheet.

2. the thickness of the first surface layer is 15 μm to 25 μm; the thickness of the second surface layer is 30 μm to 50 μm; a thickness ratio of the first surface layer to the second surface layer is 1 / 3 to 2 / 3; The antibacterial sheet according to claim 1.

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