JP7640337B2 - Container lid material - Google Patents

Description

The present invention relates to a novel container lid material.

For example, in containers that hold foods such as yogurt, jelly, pudding, ice cream, tofu, and chawanmushi, the food is stored in a sealed state by heat-sealing a lid to the opening of the container.

For such lid materials, a technology has been proposed in which the surface is treated with hydrophobic particles to repel the food contents and prevent them from adhering to the lid material.

For example, a packaging material is known in which hydrophobic oxide fine particles having a primary particle average diameter of 3 to 100 nm are attached to at least a portion of the surface of a layer containing a thermoplastic resin (Patent Document 1).

For example, a content non-adhesive packaging material is known in which a binder layer, a heat seal layer, and a hydrophobic layer are laminated in this order on a base layer, the binder layer is made of a thermosetting resin in which mixed particles with an average particle size of 1 to 100 μm are dispersed, and the mixed particles form an uneven surface on the heat seal layer side, the heat seal layer is made of a thermoplastic resin laminated on the uneven surface, and the hydrophobic layer is made of hydrophobic fine particles with an average particle size of 5 nm to 1 μm and an inorganic binder (Patent Document 2).

JP 2011-93315 A JP 2015-34038 A

However, with these conventional techniques, the hydrophobic particles cause light scattering, resulting in a cloudy, whitish appearance of the surface-treated surface. As a result, even if advertisements or information about the contents are printed on the base of the surface-treated surface (for example, the back surface of a lid), it is difficult to see. In other words, when a printed substrate is surface-treated with hydrophobic particles as described above, there is a problem that the printed content can be difficult to read depending on the color and darkness of the print. For this reason, the reality is that the back surface of a lid material that has been surface-treated with hydrophobic particles must be left plain.

On the other hand, even if the surface has been treated in this way, if the surface can be seen through the base, it will be possible to see the contents of various characters, colors, patterns, etc. displayed on the back of the lid, thereby improving the convenience and design of the lid.

Therefore, the main objective of the present invention is to provide a container lid that exhibits excellent adhesion prevention properties while allowing the display content, such as letters and patterns, located below the adhesion prevention layer to be visible.

The inventors conducted extensive research in light of the problems with the prior art and discovered that a lid material with a specific configuration can achieve the above-mentioned objective, which led to the completion of the present invention.

That is, the present invention relates to the following container lid material.
1. A lid material including at least a base layer, a transparent resin layer, a hot melt resin layer, and an anti-adhesive layer in this order, and a character pattern is expressed on at least one layer of a) the base layer, b) the transparent resin layer, and c) an intermediate layer that may be formed between the two layers,
(1) The transparent resin layer has a thickness of 10 to 40 μm,
(2a) the hot melt resin layer contains a wax component, a rosin component, and an ethylene-vinyl acetate copolymer;
(2b) the adhesion amount of the hot melt resin layer is 10 to 40 g/ ^m2 in dry weight,
(2c) protrusions having a height of 40 to 100 μm are formed on the surface of the hot melt resin layer;
(2d) the number of protrusions is 2000 to 5000 per square inch;
(3a) the anti-adhesion layer is disposed as an outermost layer;
(3b) the adhesion prevention layer contains hydrophobic oxide fine particles having an average primary particle size of 3 to 100 nm;
(3c) the adhesion amount of the anti-adhesion layer is 0.3 to 1.0 g/ ^m2 in terms of dry weight;
(4) The content of the character pattern can be visually confirmed through the anti-adhesive layer.
A container lid material characterized by the above.
2. The container lid material according to claim 1, wherein the transparent resin layer contains at least one of a polyolefin resin, a polyester resin, a polyurethane resin, an epoxy resin, an acrylic resin, and a vinyl resin.
3. A packaged product comprising a cup-shaped container filled with a content, the opening of which is sealed with the anti-adhesion layer of the container lid material according to claim 1 or 2 facing the inside of the container.
4. The packaging product according to item 3, wherein an anti-adhesion layer on a region where the opening of the cup-shaped container and the transparent resin layer of the lid are thermally bonded is embedded in the transparent resin layer and/or the hot melt resin layer during thermal bonding, thereby thermally bonding the transparent resin layer of the lid.

According to the present invention, it is possible to provide a lid material that exhibits excellent adhesion prevention while allowing the display contents such as letters and patterns located below the adhesion prevention layer to be visually recognized. In particular, in the lid material of the present invention, the transparent resin layer and the adhesion prevention layer are configured to exhibit transparency, so that the display contents such as letters and patterns can be accurately visually recognized or read even though the letters, patterns, etc. are covered with the transparent resin layer, the hot melt resin layer, and the adhesion prevention layer. At the same time, since the adhesion prevention layer is disposed on the outermost layer (top surface), it is possible to exhibit a high adhesion prevention effect (water repellency).

The lid material of the present invention, which has these characteristics, can be used as a lid material for various containers. In particular, it can be suitably used as a lid material used to seal the inside of a container (lid material for airtight containers). Therefore, it can be advantageously used as a lid material for containers that store, for example, food, cosmetics, medicines, quasi-drugs, etc.

FIG. 2 is a diagram showing a specific example of the layer structure of the covering material of the present invention. 1 is a schematic cross-sectional view of a container (cup-shaped container) sealed with a lid material of the present invention. FIG. 2 is a diagram showing the results of surface observation of a hot melt resin layer (HM) in Example 1. FIG. 2 is a diagram showing the observation results of a cross section of a laminate in Example 1.

The container lid material of the present invention (the lid material of the present invention) is a lid material including at least a base layer, a transparent resin layer, a hot melt resin layer and an adhesion prevention layer in this order, and a character pattern is expressed on at least one layer of a) the base layer, b) the transparent resin layer and c) an intermediate layer that may be formed between the two layers,
(1) The transparent resin layer has a thickness of 10 to 40 μm,
(2a) the hot melt resin layer contains a wax component, a rosin component, and an ethylene-vinyl acetate copolymer;
(2b) the adhesion amount of the hot melt resin layer is 10 to 40 g/ ^m2 in dry weight,
(2c) protrusions having a height of 40 to 100 μm are formed on the surface of the hot melt resin layer;
(2d) the number of protrusions is 2000 to 5000 per square inch;
(3a) the anti-adhesion layer is disposed as an outermost layer;
(3b) the adhesion prevention layer contains hydrophobic oxide fine particles having an average primary particle size of 3 to 100 nm;
(3c) the adhesion amount of the anti-adhesion layer is 0.3 to 1.0 g/ ^m2 in terms of dry weight;
(4) The content of the character pattern can be visually confirmed through the anti-adhesive layer.
It is characterized by:

Figure 1 shows an example of the layer structure of one of the lid materials of the present invention. The lid material of the present invention 10 has a base material layer 11 disposed below, and a printed layer formed as an intermediate layer 12 on top of the base material layer 11. The printed layer expresses characters or designs. Character designs include, for example, characters (including numbers, symbols, etc.), designs, pictures, patterns, designs, figures, and other displays. More specifically, examples include product names, manufacturer names, bar codes, PR text, illustrations, logos, trademarks (marks), characters, designs, and prize/entry displays. A transparent resin layer 13 is formed above the printed layer. In Figure 1, the transparent resin layer 13 is laminated in a state where it is in direct contact with the intermediate layer 12.

In FIG. 1, an intermediate layer 12, which is a printed layer expressing a character pattern, is introduced, but it is not necessary to form an intermediate layer, and the form is not particularly limited as long as the means is capable of expressing the character pattern. For example, any of the following methods may be used: a base layer or transparent protective layer expressing a character pattern, or an intermediate layer with a three-dimensional character pattern is introduced.

When forming an intermediate layer such as a printed layer, it may be formed on the entire surface of the base layer (so-called solid printing, etc.) or it may be formed on only a part of the base layer surface.

A hot melt resin layer 14 is formed on the surface (upper part) of the transparent resin layer 13. A specific uneven surface is formed in the hot melt resin layer 14. In FIG. 1, the hot melt resin layer 14 is formed so as to be in direct contact with the surface of the transparent resin layer 13.

An anti-adhesion layer 15 is formed on the surface of the hot melt resin layer 14. More specifically, the anti-adhesion layer 15 is formed by accumulating a plurality of hydrophobic oxide microparticles 15a on the uneven surface of the hot melt resin layer 14. The anti-adhesion layer 15 is disposed as the outermost surface layer of the lid material of the present invention. When used as a lid material for a container, the anti-adhesion layer 15 is exposed to a surface that may come into contact with the contents, but even if it comes into contact with the contents, the anti-adhesion layer 15 repels the contents, preventing the contents from adhering (sticking) to the lid material.

The hydrophobic oxide particles 15a are attached and fixed to the surface of the hot melt resin layer 13 or the transparent resin layer 14, or in contact with other hydrophobic oxide particles. A plurality of hydrophobic oxide particles 15a may be aggregated together to form a three-dimensional network structure. This can provide a higher adhesion prevention effect.

In the lid material of the present invention, as described above, the character pattern is expressed below the hot melt layer 14, and the display content of the character pattern can be seen through the hot melt layer and the anti-adhesion layer. As shown in FIG. 1, when the lid material is viewed from above A of the anti-adhesion layer, the display content (printed content) of the printing layer, which is the intermediate layer 12, can be seen through the hot melt layer 14 and the transparent resin layer 13. Therefore, for example, if character information is printed on the printing layer, the character information can be read. In particular, by adopting the specific layer structure as described above, the lid material of the present invention can achieve an excellent anti-adhesion effect and obtain higher visibility, even though the character pattern is covered by the anti-adhesion layer, the hot melt resin layer, and the transparent resin layer.

The thickness of the lid material of the present invention can be set appropriately depending on, for example, the type of contents and the shape of the container, and can be, for example, in the range of about 70 to 200 μm, but is not limited to this. Each layer will be described in more detail below.

In the present invention, the substrate layer functions as a core material for the lid material. In particular, the substrate layer imparts stiffness to the lid material, imparts durability to the lid material against breakage, etc., and provides strength to the lid material so that the lid material does not break accidentally when it is peeled off while it is adhered to the container.

In addition, in cases where it is undesirable for the contents filled in the container to be exposed to light, air, etc., the base material can be provided with a layer that has the effect of suppressing the transmission of light, preventing the intrusion of outside air, or suppressing the transmission of gas, thereby preventing the smell of the contents from escaping outside the container.

The material of the substrate layer is not particularly limited as long as it has the above-mentioned functions, and various materials such as plastics, rubber, metals, glass, ceramics, and paper can be used. Therefore, as materials for forming the substrate layer, for example, paper, synthetic paper, resin film, resin film with a vapor deposition layer, synthetic resin plate, aluminum foil or other metal foil, metal plate, woven fabric, nonwoven fabric, leather, synthetic leather, wood, glass plate, etc., alone or composite materials or laminate materials thereof can be suitably used. Among these, it is preferable to use aluminum foil or resin film with a vapor deposition layer, since it can prevent the transmission of light or gas while also obtaining a predetermined strength.

The thickness of the substrate layer is not particularly limited, but is usually about 7 to 30 μm, and preferably 12 to 20 μm.

The transparent resin layer mainly plays the roles of a) ensuring cushioning as a base for the anti-adhesion layer in order to laminate the anti-adhesion layer on the base layer, and b) imparting adhesion to the hot melt resin. In addition, along with these functions, the transparent resin layer can also contribute to the sealing property with the container as a lid material.

The transparent resin layer contains a resin component, and preferably contains a thermoplastic resin having thermal adhesive properties as the resin component. This allows the transparent resin layer to function as a thermal adhesive layer, and as a result, the adhesion prevention layer (particularly the hydrophobic oxide fine particles) can be firmly fixed to the substrate layer as described above.

From the above viewpoint, the thermoplastic resin constituting the transparent resin layer is not limited to any resin having thermal adhesive properties, and examples of such resins include adhesives such as polyolefin-based resins, polyester-based resins, polyurethane-based resins, epoxy-based resins, acrylic-based resins, and vinyl-based resins. More specifically, a) low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid copolymer, vinyl chloride-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-propylene copolymer, methyl pentaethylene polymer, polybutene polymer, polyethylene, polypropylene, and other polyolefin resins, b) acid-modified polyolefin resins obtained by modifying these polyolefin resins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid, as well as c) polyvinyl acetate resins, poly(meth)acrylic resins, polyacrylonitrile resins, polyvinyl chloride resins, and the like. Other examples include blend resins of these, copolymers containing combinations of monomers that constitute these, and modified resins.

Among these, in the present invention, polyolefin resins are preferred, and among these, polyethylene resins are more preferred. More specifically, examples include polyethylene resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene, as well as ethylene copolymers such as ethylene-vinyl acetate copolymer resins. Among these, in the present invention, it is preferred to employ polyethylene resins, and low-density polyethylene resins can be particularly preferably employed.

The method for forming the transparent resin layer is not particularly limited, and examples thereof include a) a method of applying and drying a solution in which a transparent resin is dissolved in a solvent or a dispersion in which a transparent resin is dispersed in a solvent, b) a method of extruding and applying a molten transparent resin, followed by cooling and solidifying, and c) a method of laminating a transparent resin film with or without an adhesive, etc. In order to improve adhesion to the substrate, it is preferable to apply an adhesive (anchor coating agent) to the substrate layer in an ^amount of about 0.01 to 1.0 g/m2 as necessary.

When forming an adhesive layer, the adhesive that can be used is not limited as long as it can be used for food applications, and for example, a laminating adhesive can be suitably used. Examples of laminating adhesive components include polyester adhesives, polyether adhesives, and polyurethane adhesives. The properties of the adhesive are also not limited, and any of solvent-based, solventless, and water-based adhesives can be used. If necessary, a coating liquid containing hydrophobic particles can be applied and dried, and then the opposite side of the film can be laminated to another substrate.

From the viewpoint of sealing with the container and light transmission, the thickness of the transparent resin layer is preferably about 10 to 40 μm. If the thickness is less than 10 μm, the cushioning effect when sealing the container is weak, and the seal balance becomes poor, making it more likely that sealing defects will occur. If the thickness exceeds 40 μm, the color tone of the surface on the back of the lid becomes cloudy, making it difficult to clearly see the printed layer.

The content of the thermoplastic resin in the transparent resin layer may be sufficient as long as it can exhibit the cushioning properties described above, and is usually about 90 to 100% by mass, but is not limited to this.

In addition, other additives can be appropriately blended into the transparent resin layer as necessary within the range that does not impair the effects of the present invention. For example, dispersants, colorants, anti-settling agents, viscosity modifiers, defoamers, fillers, antistatic agents, ultraviolet absorbers, oxygen absorbers, etc. can be blended.

In the present invention, it is preferable that the transparent resin layer does not contain particles (hereinafter referred to as "filler particles") having a particle size that gives the surface of the transparent resin layer unevenness. In this case, the size of the filler particles is large enough to give the surface of the transparent resin layer unevenness derived from the filler particles, and the average particle size (measured by a laser diffraction particle size distribution meter) is usually 10 to 40 μm, and particularly 12 to 30 μm.

Hot-melt resin layer The hot-melt resin layer contributes to the thermal adhesion when the lid material of the present invention is joined to the container, and also plays a role in ensuring the ease of opening the lid material of the present invention joined to the container.

The hot melt resin layer contains a wax component, a rosin component, and an ethylene-vinyl acetate copolymer.

The wax component is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax, natural waxes such as carnauba wax and palm wax, and synthetic waxes such as polyethylene and polypropylene. The content of the wax component in the hot melt resin layer is usually about 20 to 80% by weight, but is not limited to this.

The rosin component is not limited to, and examples thereof include various rosins such as gum rosin and wood rosin. The content of the rosin component in the hot melt resin layer is usually about 0.5 to 30% by weight, but is not limited to this.

The ethylene-vinyl acetate copolymer may be any copolymer of ethylene and vinyl acetate, and various grades may be used. The content of the ethylene-vinyl acetate copolymer in the hot melt resin layer is usually about 20 to 50% by weight, but is not limited to this.

In addition to these three components, the hot melt resin layer may contain other additives as long as they do not impede the effects of the present invention. Examples of additives include the various additives listed in the explanation of the transparent resin layer.

In the present invention, a hot melt resin layer can be formed using a composition containing each of these components. As such a composition, a known or commercially available hot melt adhesive can be used. For example, the hot melt adhesive is applied in a molten state and then cooled and solidified. If hydrophobic oxide fine particles are then applied, the hydrophobic oxide fine particles can be attached directly to the thermal adhesive layer, facilitating continuous production of the packaging material of the present invention.

The hot melt resin layer has protrusions with a height of 40 to 100 μm formed on its surface (the anti-adhesion layer side), and the density (number) of the protrusions is 2,000 to 5,000 per square inch. This allows the hydrophobic oxide particles in the anti-adhesion layer to be more firmly fixed, and also makes it easier for the hydrophobic oxide particles to be embedded during thermal bonding, resulting in a higher seal.

The shape of the protrusion is not particularly limited, and may be, for example, substantially conical, substantially pyramidal, substantially cylindrical, substantially prismatic, substantially hemispherical, etc. Furthermore, one or more of these shapes may be included.

The height of the protrusions is the height from the transparent resin layer, which is the base, to the top of the protrusions, and is usually in the range of 40 to 100 μm, and preferably 50 to 80 μm. As described above, the density of the protrusions is usually in the range of 2000 to 5000 pieces/square inch, and preferably 3000 to 4000 pieces/square inch. By setting it in such a range, good adhesion prevention can be achieved. If the height of the protrusions is less than 40 μm or the density is less than 2000 pieces/square inch, the hydrophobic oxide fine particles are weakly fixed and easily detached during transportation, etc., making it difficult to maintain good adhesion prevention. On the other hand, if the height of the protrusions exceeds 100 μm or the density exceeds 5000 pieces/square inch, the color tone of the surface on the back side of the lid becomes cloudy, making it difficult to clearly see the printed layer.

In the present invention, the height of the protrusions can be confirmed by using a cutting machine such as a microtome to cut a smooth cross section of the apex of the protrusion, and observing and measuring the length of the cross section under a microscope. In addition, the density of the protrusions can be measured by observing the sample under a microscope so that the entire field of view is filled with the sample, counting the number of protrusions in the field of view, and converting this to the number per unit area (total number/area of field of view).

In addition, in the present invention, protrusions with a height of less than 40 μm or protrusions with a height of more than 100 μm may be included as long as they do not impede the effects of the present invention.

The amount of the hot melt resin layer attached is about 10 to 40 g/ ^m2 in terms of dry weight, and preferably 15 to 25 g/ ^m2 . If the amount of attachment is less than 10 g/ ^m2 , the hydrophobic oxide particles cannot be embedded in the thermal adhesive layer, which hinders sealing with the container. If the amount of attachment exceeds 40 g/ ^m2 , the color tone of the surface on the back side of the lid becomes cloudy, making it difficult to clearly see the printed layer.

The method for forming the hot melt resin layer is not particularly limited, so long as the specified protrusions as described above are formed. For example, a hot melt resin layer having the above-mentioned protrusions can be suitably formed by applying the hot melt resin in a molten state using a gravure plate having a specified surface unevenness, and then cooling and solidifying the resin.

Anti-adhesion layer The anti-adhesion layer is a layer provided on the outermost surface of the back of the lid of a container lid material. In other words, it is a layer that can come into contact with the contents when the container lid material is adhered to a container. The anti-adhesion layer contains hydrophobic oxide fine particles. The anti-adhesion layer only needs to contain hydrophobic oxide fine particles, and may also contain a binder resin that bonds the hydrophobic oxide fine particles together. Preferably, a part of the anti-adhesion layer is embedded in the thermoplastic resin in the transparent resin layer, and bonds the hydrophobic oxide fine particles together.

The hydrophobic oxide fine particles are not particularly limited as long as they have hydrophobicity, and may be those that have been hydrophobized by surface treatment. For example, hydrophilic oxide fine particles may be surface-treated with a silane coupling agent or the like to make the surface hydrophobic. The type of oxide is also not limited as long as it has hydrophobicity. For example, at least one of silica (silicon dioxide), alumina, titania, etc. may be used. These may be publicly known or commercially available. Examples of silica include products under the names "AEROSIL R972", "AEROSIL R972V", "AEROSIL R972CF", "AEROSIL R974", "AEROSIL RX200", and "AEROSIL RY200" (all manufactured by Nippon Aerosil Co., Ltd.), "AEROSIL R202", "AEROSIL R805", "AEROSIL R812", and "AEROSIL R812S" (all manufactured by Evonik Degussa). Examples of titania include product under the name "AEROXIDE TiO ₂ T805" (manufactured by Evonik Degussa). An example of alumina is fine particles such as "AEROXIDE Alu C" (manufactured by Evonik Degussa) whose particle surfaces have been made hydrophobic by treating them with a silane coupling agent.

Among these, hydrophobic silica fine particles can be preferably used. In particular, hydrophobic silica fine particles having trimethylsilyl groups on the surface are preferred because they provide better adhesion prevention. Commercially available products that correspond to this include, for example, the aforementioned "AEROSIL R812" and "AEROSIL R812S" (both manufactured by Evonik Degussa).

The hydrophobic oxide fine particles contained in the adhesion prevention layer preferably have a primary average particle diameter of 3 to 100 nm, and more preferably 5 to 20 nm. By setting the primary particle average diameter within the above range, the hydrophobic oxide fine particles are in a moderately aggregated state, and gas such as air can be retained in the voids in the aggregate, resulting in excellent adhesion prevention. In other words, this aggregated state is maintained even after adhesion to the transparent resin layer, so excellent adhesion prevention can be achieved.

In the present invention, the primary particle average diameter can be measured using a scanning electron microscope (FE-SEM). If the resolution of the scanning electron microscope is low, it may be measured using another electron microscope such as a transmission electron microscope in combination. Specifically, if the particle shape is spherical, the diameter is considered to be the diameter, and if the particle shape is non-spherical, the average of the longest and shortest diameters is considered to be the diameter. The average diameter of 20 particles randomly selected by observation using a scanning electron microscope or the like is taken to be the primary particle average diameter.

The amount (weight after drying) of the hydrophobic oxide fine particles to be attached to the transparent resin layer is 0.3 to 1.0 g/m ^2. By setting it within the above range, better non-adhesiveness can be obtained for a long period of time, and it is more advantageous in terms of preventing the hydrophobic oxide fine particles from falling off, costs, etc. It is preferable that the hydrophobic oxide fine particles attached to the thermal adhesive layer form a porous layer having a three-dimensional network structure.

The hydrophobic oxide fine particles may be attached to the entire surface of the transparent resin layer (the entire surface of the surface opposite to the substrate layer side), or may be attached to the area excluding the area where the transparent resin layer is thermally bonded (so-called adhesive margin). In the present invention, even if they are attached to the entire surface of the transparent resin layer, most or all of the hydrophobic oxide fine particles present on the area where the transparent resin layer is thermally bonded are embedded in the transparent resin layer, so that thermal bonding is not hindered, and it is also preferable from the viewpoint of industrial production that they are attached to the entire surface of the transparent resin layer.

The thickness of the adhesion prevention layer can be set appropriately within the range of the adhesion amount described above, for example, about 0.1 to 5 μm, but is not limited to this.

The method for forming the adhesion prevention layer is not particularly limited, but it can be suitably carried out by a method including a step of applying a dispersion liquid in which hydrophobic oxide particles are dispersed in a solvent to a part or the entire surface of the transparent resin layer, and drying the applied liquid.

The solvent used in the dispersion is not particularly limited, and one or more solvents commonly used in food production, such as water, ethanol, etc., can be used.

There are no particular limitations on the amount of hydrophobic oxide particles contained in the dispersion, but it is generally preferable to set the amount appropriately within the range of about 5 to 200 g/L (liter).

The dispersion may also contain dispersants, colorants, anti-settling agents, viscosity modifiers, binders, defoamers, etc., as necessary, within the limits that do not impair the effects of the present invention.

The method for applying the dispersion onto the transparent resin layer is not particularly limited, and any known method such as roll coating, various gravure coatings, bar coating, doctor blade coating, comma coater, brush coating, etc. can be appropriately used. Note that the hydrophobic oxide fine particles can be applied more uniformly if they are mixed into the dispersion medium.

The coating amount (weight after drying) can be appropriately set depending on the desired water repellency or oil repellency, but is usually about 0.3 to 1.0 g/m ² , and preferably 0.4 to 0.6 g/m ^2. By setting it within the above range, a porous layer made of anti-adhesive particles can be more reliably formed, resulting in more excellent non-adhesiveness over a long period of time, and further advantages in terms of preventing the fine particles from falling off, costs, etc.

After coating, the coated surface is dried to obtain a film with the adhesion-preventing particles adhered to the resin substrate film. There are no particular limitations on the drying method, and either natural drying or heat drying may be used. When heat drying is used, the temperature is usually about 60 to 190°C, and preferably 80 to 150°C. The heating time may be set appropriately depending on the heating temperature, etc., but is usually about 3 to 30 seconds.

The water repellency of the formed adhesion prevention layer is preferably such that the contact angle with pure water (25°C) is 140 degrees or more, and particularly 150 degrees or more.

Other layers In the lid material of the present invention, other layers may be formed as long as they do not impede the effects of the present invention. For example, an adhesive layer may be interposed between the layers. In addition, for example, a printed layer, an overcoat layer, a clear layer, etc. may be formed on the opposite side of the substrate to the side on which the transparent resin layer is formed (i.e., the surface on which the lid material is exposed to the outside).

Expression of character pattern In the lid material of the present invention, a character pattern is expressed in at least one layer of a) the base material layer, b) the transparent resin layer, and c) an intermediate layer that may be formed between the two layers. As described above, in the lid material of the present invention, the character pattern is expressed on the lower side of the hot melt resin layer (the side opposite to the anti-adhesive layer), and the display content can be seen through. In the conventional lid material, characters, patterns, etc. are applied to the front surface (outside), but since an anti-adhesive layer is formed on the back surface, even if a character pattern is displayed, it is not visible or difficult to see, so printing on the back surface has been avoided. In contrast, in the lid material of the present invention, even if an anti-adhesive layer is formed on the outermost layer, the character pattern arranged on the lower layer can be seen through, so it is possible to freely apply character patterns and other designs to the back surface of the lid material.

As shown in Figure 1, the method of expressing the character pattern may be any method as long as the displayed content can be seen from above the adhesion prevention layer. Examples include, but are not limited to, a) a method of introducing a printed layer as an intermediate layer, b) a method of forming a three-dimensional character pattern by using unevenness, c) a method of forming a base layer, transparent resin layer or intermediate layer using a film on which a character pattern has already been expressed during production, and d) a method of laminating members expressing a character pattern. In addition, each of these methods may be used alone or in combination of two or more.

In the above method a), the printing layer can be formed by printing ink in a predetermined pattern using a known printing method such as gravure printing, flexographic printing, inkjet printing, silk screen printing, etc. The printing layer can also be formed by transferring the printing layer using a transfer film, etc. In this way, the printing layer can be formed by printing the surface of the base layer using ink, transfer film, etc.

When applying a printing layer, the color is not limited, and various colors of ink, such as white, black, red, green, and yellow, can be used as appropriate. In particular, when the contents to be filled in the container are food, etc., it is preferable to use edible ink, since this ensures higher safety. In addition, the ink may be either oil-based ink or water-based ink.

In the above (b), examples of the method of forming the character pattern three-dimensionally by the unevenness include (b1) a method of forming the character pattern by engraving the base layer, the transparent resin layer, or the intermediate layer, and (b2) a method of forming the base layer, the transparent resin layer, or the intermediate layer using a film on which the character pattern has been formed three-dimensionally by the unevenness in advance. The method of (b1) above is not particularly limited, and may be either engraving by laser (non-contact type) or engraving by various engraving machines (contact type). The method of (b2) above is also not limited, and examples of the method include a method of molding by press molding using a mold on which a character pattern for transfer is printed. In the above (b), the unevenness may be formed on either one side or both sides of each layer. In addition, when it is formed on one side, it may be either the side on which the transparent resin layer is laminated or the opposite side.

In the above (c), examples include (c1) a method of forming a base layer, a transparent resin layer, or an intermediate layer using a film incorporating a component expressing a character pattern (for example, a plate or the like having a specific character pattern embedded therein), and (c2) a method of forming a base layer, a transparent resin layer, or an intermediate layer using a film on which a pattern, character, or the like is drawn using a colored resin.

In the above (d), for example, a method of laminating a member expressing a character pattern onto a base layer, a transparent resin layer, or an intermediate layer can be mentioned.

In addition, in the lid material of the present invention, text patterns may also be displayed on the other side of the base layer (the outer side of the container). These may be the same as the printing layer of known lid materials.

2. Use of the container lid The lid of the present invention can be used as a lid for various containers. More specifically, it is used to close the opening of a container with the anti-adhesion layer on the outermost surface of the lid of the present invention disposed on the inside of the container. That is, the lid of the present invention includes a substrate (sheet-like substrate), and both sides of the substrate face the outside of the container and the inside of the container when the lid of the container is used as a lid for the container.

Figure 2 shows a packaged product 20 in which the opening of a cup-shaped container 17 filled with contents 16 is closed by the lid material 10 of the present invention in Figure 1. The flange portion 17a of the opening of the cup-shaped container 17 and the transparent resin layer 13 and hot melt resin layer of the lid material are bonded by thermal adhesion (heat sealing), and as a result, the contents 16 can be sealed. In this case, before thermal bonding, the hydrophobic oxide particles 15a of the adhesion prevention layer 15 are laminated on the thermally bonded area of the lid material of the present invention, but during thermal bonding, the hydrophobic oxide particles are embedded in the transparent resin layer 13 and/or hot melt resin layer 14. This achieves particularly strong bonding between the transparent resin layer 13 and the container opening. Since the hydrophobic oxide particles 15a are exposed in the area other than the thermally bonded area, when food or the like is contained as the contents, the contents are less likely to adhere to the lid material even if the contents come into contact with the lid material.

In the lid material 10 of the present invention shown in FIG. 2, the surface facing the inside of the container comprises, in order from the base material layer 11, an intermediate layer (printed layer) 12, a transparent resin layer 13, a hot melt resin layer 14, and an anti-adhesion layer 15. If necessary, the surface facing the outside of the container can be appropriately provided with, for example, a second base material layer, a printed layer, a protective layer for protecting the printed layer, etc. (not shown).

In this case, the printing layer 12 provided on the surface of the base material layer 11 on the side having the adhesion prevention layer 15 is also called the lid back printing, and the printing applied to the other surface is also called the front printing. Generally, information about the contents to be filled in the container (e.g., product name, logo, ingredients, expiration date, image of the contents, barcode, etc.) is printed on the front printing. In general lid back printing that does not have a function to prevent the contents from adhering may be printed with information about the product, campaign information, advertisements, etc., but in the conventional technology, when the back of the lid has a function to prevent the contents from adhering to the back of the lid, the back printing is avoided because the structure of the adhesion prevention function of the surface causes light to be diffused and becomes white and dull, making it difficult to see. In contrast, the lid material of the present invention, for example as shown in FIG. 1, can be seen through the adhesion prevention layer 15 and the transparent resin layer 13 even when viewed from the A direction, so that the display content can be reliably and easily understood. As such, container lid materials that have a function to prevent contents from adhering but do not have a lid back print, and container lid materials that have a lid back print but do not have a function to prevent contents from adhering are both publicly known, but container lid materials that have a lid back print and also have a function to prevent contents from adhering are essentially contradictory requirements when manufacturing container lid materials, but the lid material of the present invention achieves both.

In Figure 2, a cup-shaped container is shown, but the container shape is not limited as long as the lid material of the present invention can be applied, and it can be applied to any shape such as a tray or bottle.

The contents to be loaded into the container are not particularly limited, and may be any of foods such as yogurt, pudding, and ice cream, as well as cosmetics, medicines, and the like. The nature of the contents is also not limited, and may be applied to, for example, solid materials as well as fluid materials. The contents may be either gel-like or non-gel-like. Furthermore, the contents may be a material that contains at least one of water and oil (oils and fats), but contents that contain water are particularly suitable.

The following examples and comparative examples are presented to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to the examples.

Example 1
A polyurethane-based dry lamination adhesive (weight after drying 3.5 g/m ² ; abbreviated as D) was used on one side of an aluminum foil (1N30, soft foil; abbreviated as AL) having a thickness of 15 μm to bond it to the printed surface of a polyethylene terephthalate film (abbreviated as PET) having a thickness of 12 μm, which had been subjected to reverse printing (abbreviated as print), to prepare a substrate layer. The aluminum surface of this substrate layer was printed. The printing was performed with a two-dimensional barcode design to make it easier to compare visibility. An anchor coat (main component: polyester resin; abbreviated as AC) treatment was applied on this printed layer, and low-density polyethylene resin (abbreviated as LDPE) was extruded and laminated to a film thickness of 20 μm. Furthermore, a hot melt agent (35 parts by weight of wax, 35 parts by weight of rosin, and 30 parts by weight of ethylene-vinyl acetate copolymer; abbreviated as HM) was gravure hot melt coated onto the low density polyethylene to a weight of 20 g/ ^m2 , a thickness of 50 μm, and approximately 3,500 particles/square inch. This resulted in a laminate having a structure of "PET/printing/D/AL/printing/AC/LDPE/HM".
Here, the surface of the hot melt resin layer (HM) of the obtained laminate was observed. The surface was observed with a scanning electron microscope, the number of protrusions in the field of view was counted, and the density of the protrusions was calculated by dividing the number by the area of the field of view. A micrograph of the surface is shown in Figure 3. A cross section of the laminate was also cut out, and the height of all the protrusions in the cross section was measured. A micrograph of the cross section is shown in Figure 4. The density and height of the protrusions are shown in Table 1 (similar measurements were also made in the following Examples and Comparative Examples, and the results are also shown in Table 1).
Next, a coating solution was prepared as an anti-adhesion layer by dispersing 5 g of hydrophobic oxide fine particles (product name "AEROSIL R812S" manufactured by Evonik Degussa, BET specific surface area: 220 ^m2 /g, primary particle average diameter: 7 nm) in 100 mL of ethanol. This coating solution was applied to the transparent resin layer surface of the laminate by a bar coating method so that the weight after drying was 0.5 g/ ^m2 , and then the coating solution was dried at 100°C for about 10 seconds to evaporate the ethanol, thereby obtaining a container lid material sample.

Example 2
A container lid material sample was obtained in the same manner as in Example 1, except that the low density polyethylene film thickness was 10 μm, the hot melt agent weight was 10 g/m ² , the thickness was 40 μm, and there were about 2000 pieces/square inch.

Example 3
A container lid material sample was obtained in the same manner as in Example 1, except that the low density polyethylene film thickness was 40 μm, the hot melt agent weight was 40 g/m ² , the thickness was 100 μm, and there were about 5000 pieces/square inch.

Comparative Example 1
A container lid material sample was prepared in the same manner as in Example 1, except that no adhesion preventing layer was provided.

Comparative Example 2
A container lid material sample was obtained in the same manner as in Example 1, except that the coating amount of hydrophobic oxide fine particles as the adhesion prevention layer was set to 1.2 g/ ^m2 in terms of weight after drying.

Comparative Example 3
A container lid material sample was obtained in the same manner as in Example 1, except that the low density polyethylene film thickness was 9 μm, the hot melt agent weight was 8 g/m ² , the thickness was 20 μm, and there were about 1800 pieces/square inch.

Comparative Example 4
A container lid material sample was obtained in the same manner as in Example 1, except that the low density polyethylene film thickness was 45 μm, the hot melt agent weight was 50 g/m ² , the thickness was 110 μm, and there were about 5,500 pieces/square inch.

Comparative Example 5
A container lid material sample was obtained in the same manner as in Example 1, except that the hydrophobic oxide fine particles in the adhesion prevention layer were changed to Silophobic-100 (manufactured by Fuji Silysia Chemical), which is hydrophobic silica particles having an average primary particle diameter of 2.7 μm.

Test Example 1 (visibility of lid back printing)
The visibility of the print on the back of the lid was evaluated for the samples obtained in each Example and Comparative Example. The readability of the printed two-dimensional barcode was evaluated using the camera of a smartphone (Samsung Electronics Galaxy SC-04J). The evaluation method was to bring the camera close to the smartphone at a distance of 10 to 15 cm so that the entire two-dimensional barcode was displayed in the entire field of view of the smartphone through the camera, and samples that could be read immediately were marked as "◯", and samples that took several seconds to read or could not be read were marked as "X". The evaluation results are shown in Table 1.

Test Example 2 (Seal Strength)
Packages were produced using lids cut from each packaging material into the shape of the lid (a circle with a diameter of 75 mm with a tab). Specifically, the lids were heat-sealed onto the flanges of a flanged paper/polyethylene container (flange width 3 mm, flange outer diameter 70 mm, height approximately 55 mm, internal volume approximately 130 cm3, paper approximately 300 μm thick coated with 100 μm polyethylene and molded so that the polyethylene was on the inside of the container), to produce each package. The heat-sealing conditions were a temperature of 160° C. and a pressure of 1 kg/ ^cm2 for 1 second.
The tab of the lid material on each package was pulled at a speed of 100 mm/min in a direction at an elevation angle of 45 degrees from the opening start point, the maximum load at the time of opening was taken as the seal strength (N), n = 6 points were measured for each package, and the average value was calculated. Samples that showed good openability with an average value of 10.0 to 15.0 N/CUP were rated "◯", and samples that showed a weak seal strength with an average value of less than 5.0 N/CUP or a seal strength exceeding 15.0 N/CUP were rated "X".

Test Example 3 (Anti-adhesion properties)
A container seal sample was obtained in the same manner as in Test Example 2, except that the heat sealing conditions were changed from a temperature of 160° C. and a pressure of 1 kg/cm ² to 180° C. and a pressure of 3 kg/cm ² .
Each of the prepared packages was vibrated for 1 minute 40 seconds (10 Hz-10 seconds, 15 Hz-10 seconds, 20 Hz-10 seconds, 25 Hz-10 seconds, and 30 Hz-10 seconds, repeated twice, with up and down reciprocating vibration), with an amplitude of 2.2 mm (vertical direction), and an acceleration of about 2G, using a vibration tester (IDEX Corporation, TRANSPORTATION TESTER BF-30U). The lid was then opened with fingers, and the amount of yogurt attached to each lid (adhesion area) was visually judged. On the surface (anti-adhesion layer) in contact with the contents, samples with an adhesion area of 0% or more and less than 10% were marked as "◯", samples with an adhesion area of 10% or more and less than 30% were marked as "△", and samples with an adhesion area of 30% or more and less than 100% were marked as "X". The evaluation results are shown in Table 1.

As is clear from the results in Table 1, the container lid material of the present invention has the function of preventing the contents from adhering to the back of the lid, while also making it possible to clearly recognize the printed content of the printing layer, regardless of the color or darkness of the printing layer on the back of the lid.

Claims (4)

A lid material including at least a base layer, a transparent resin layer, a hot melt resin layer, and an anti-adhesive layer in this order, and a character pattern is expressed on at least one layer of a) the base layer, b) the transparent resin layer, and c) an intermediate layer that may be formed between the two layers,
(1) The transparent resin layer has a thickness of 10 to 40 μm,
(2a) the hot melt resin layer contains a wax component, a rosin component, and an ethylene-vinyl acetate copolymer;
(2b) the adhesion amount of the hot melt resin layer is 10 to 40 g/ ^m2 in dry weight,
(2c) protrusions having a height of 40 to 100 μm are formed on the surface of the hot melt resin layer;
(2d) the number of protrusions is 2000 to 5000 per square inch;
(3a) the anti-adhesion layer is disposed as an outermost layer;
(3b) the adhesion prevention layer contains hydrophobic oxide fine particles having an average primary particle size of 3 to 100 nm;
(3c) the adhesion amount of the anti-adhesion layer is 0.3 to 1.0 g/ ^m2 in terms of dry weight;
(3d) the hydrophobic oxide fine particles aggregate with each other to form a three-dimensional network structure, and the three-dimensional network structure is a porous layer;
(4) The content of the character pattern can be visually confirmed through the anti-adhesive layer.
A container lid material characterized by the above. The container lid material according to claim 1, wherein the transparent resin layer contains at least one of polyolefin-based resin, polyester-based resin, polyurethane-based resin, epoxy-based resin, acrylic-based resin, and vinyl-based resin. A packaged product in which a cup-shaped container is filled with contents, and the opening of the container is sealed with the anti-adhesion layer of the container lid material described in claim 1 or 2 facing the inside of the container. The packaging product according to claim 3, wherein an anti-adhesion layer on the area where the opening of the cup-shaped container and the transparent resin layer of the lid material are thermally bonded is embedded in the transparent resin layer and/or the hot melt resin layer during thermal bonding, thereby thermally bonding the transparent resin layer of the lid material.