DESCRIPTION EASILY OPENABLE FILM, COVER MATERIAL AND CONTAINER TECHNICAL FIELD The present invention relates to an easily openable film, and a cover material and a container, each using the film. More specifically, the present invention relates to an easily openable film excellent in its low-temperature heat-sealing property, low odorousness, and appearance of peeled face, an easily openable film excellent in its low-temperature heat-sealing property, heat resistance, and appearance of peeled face, and a cover material and a container each using the film.

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit pursuant to 35 U. S. C. §119 (e) of U. S.

Provisional Applications No. 60/520,653 filed on November 18, 2003, and No.

60/523,110 filed on November 19,2003, and prioirity is claimed on Japanese Patent Applications No. 2003-357629 filed October 17,2003, No. 2003-357630 filed October 17,2003, No. 2004-277690 filed September 24,2004, and No. 2004-277691 filed September 24,2004, and U. S. Provisional Applications No. 60/520,653 filed on November 18,2003, and No. 60/523, 110 filed on November 19,2003, the contents of which are incorporated herein by reference.

BACKGROUND ART In the field of container packages for food, medical products and the like, containers equipped with an easily openable cover material are widely used. Among

containers constituted by a container body and a cover material, there is a strong move toward use, in recent food containers, of polyester-based resins which are less adsorbing of the food flavor for the container body.

Representative examples of the polyester-based resin include polyethylene terephthalate (PET), polybutylene terephthalate and polyethylene naphthalate. In particular, when PET is in a substantially amorphous state, the PET is widely used for so-called A-PET containers, and when PET is in a partially crystallized state and has heat resistance, the PET is widely used for C-PET containers. Also, the container after being filled with food or medical product is subjected to a sterilization treatment such as boiling or retorting. From this viewpoint, use of an A-PET container or a C-PET container is increasing.

Engineering plastic such as polycarbonate, polyethersulfone, and the like, have been used for medical containers. For example, the medical containers include half-kit containers which are used for kit-products referred to as half-kits.

Half-kit containers comprise a dissolved solution container in which a dissolved solution is stored and a capsule in which a needle made of resin is stored and which is connected and combined with the dissolved solution container. The capsule comprises a capsule body and a cover material which is peelable from the capsule body. In order to mix the dissolved solution and other medicament such as antibiotic, or the like. which are stored in the half-kit container, first of all, the cover material of the capsule is peeled.

Then, the needle made of resin in the capsule is stuck into a medical container such as a vial in which medicament such as antibiotic, or the like is stored and which is sealed with a rubber stopper. As a result, the dissolved solution container and the medical container are connected, and thereby the dissolved solution and the medicament are mixed. The mixed medicament is discharged from the dissolved solution container through an

injection needle.

In these half-kit containers, engineering plastics, such as polycarbonate and polyethersulfone are used for the capsule body.

Moreover, the half-kit container comprising the capsule in which the resin needle is stored, is explained above. However, there is other half-kit container comprising the capsule in which the capsule body and the resin needle are combined together as a unit.

Polycarbonate is used as raw material for a production method for a container in which a polycarbonate sheet is subjected to vacuum forming or pressure forming, and for an injection mold method for a container and a part such as a capsule constituting a container. In particular, since polycarbonate has excellent heat resistance, polycarbonate has been increasingly used for heat sterilization applications.

The cover material used for these containers is generally in the form that a sealant film is laminated with biaxially stretched polypropylene film, biaxially stretched polyamide film, biaxially stretched polyester film, paper, aluminum foil, or the like.

The sealant film is an easily openable film capable of being heat-sealed to a container body made of polyester or polycarbonate. The easily openable film is desired to have many functions.

For example, the easily openable film is desired to have sufficient seal strength to impart the easy openability (usually from 5 to 20 N/15 mm-width is necessary) and stability thereof, in addition to have low-temperature sealability which enables sealing at a temperature and a pressure, at which the container body does not change the shape. In addition, the easily openable film is desired to have heat resistance such that there is no deformation, or the like, or opening during high-temperature treatments such as boiling and retorting, and good appearance without the easily openable film remaining

(hereinafter referred to as a"no-film remaining"property). Specifically, phenomenon, in which easily openable film does not remain ununiformly on a peeled face of the container or in which easily openable film in fiberous states forms between the easily openable film and the peeled face during peeling off from the peeled face of the container, is referred to have good appearance without film remaining property (no-film remaining property).

In addition, the easily openable film is desired to have a low odorousness, that is, when the film is sterilized by heat or active energy light, such as gamma ray, electron beam, and ultraviolet light, the film generates little unpleasant odor, and the film is also desired to have no or little deterioration of heat-seal strength.

As for the easily openable film, various techniques have been heretofore disclosed and some techniques are being practically used.

For example, Patent Document 1 (JP-A-59-59444 (the term"JP-A"as used herein means an"unexamined published Japanese patent application") ) discloses a two-layer film consisting of a support layer comprising a polyethylene-based resin and a seal layer constituted by a composition comprising a saturated polyester resin and a specific polyethylene-based resin.

Patent Document 2 (JP-A-60-180833) discloses a resin composition comprising a specific polyester-based resin and a polyethylene, a polypropylene or a graft-modified product thereof as a film material which imparts smoothness of the peeled face.

Patent Document 3 (Japanese Patent No. 2883025) discloses a sealant film comprising two layers, that is, a layer comprising a mixture of a polar group-containing ethylene-based copolymer, a polyolefin resin and an acid-modified polyolefin, and a layer adjacent thereto comprising a mixture of a polar group-containing ethylene-based copolymer and an ethylene-propylene copolymer.

Patent Document 4 (Japanese Patent No. 2724938) discloses a cohesive failure-type sealant film having a layer comprising a polar group-containing ethylene-based copolymer and a polypropylene or an ethylene-propylene copolymer.

Patent Document 5 (JP-A-2002-160329) discloses a film comprising two layers, that is, a seal layer comprising a polyester-based resin and a layer adjacent thereto comprising a polar group-containing ethylene-based copolymer.

However, in the invention of Patent Document 1, the support layer comprises a polyethylene-based resin, and therefore, the interlayer adhesive strength between the support layer and the seal layer is weak, as a result, interlayer separation readily occurs and the seal layer is liable to remain ununiformly on the container body. That is, this invention is not satisfactory in view of a no-film remaining property.

The invention of Patent Document 2 does not have satisfactory in the low-temperature heat-sealing property. Furthermore, since a specific polyester-based resin is used, when a graft-modified product is used, this is expensive and the profitability is disadvantageously low.

The invention of Patent Document 3 is not satisfied from the standpoint of stably expressing heat-seal strength or imparting heat resistance high enough to withstand the temperature conditions during boiling, retorting, or the like.

In the invention of Patent Document 4, the seal layer peels off by undergoing cohesive failure and therefore, a part of the seal layer remains ununiformly on the container body. Thus, this invention is not satisfactory with respect to the no-film remaining property. Also, this invention is not satisfactory in the expression of the necessary heat-seal strength and stability thereof.

The film of Patent Document 5 is not only insufficient in the heat resistance but also has a problem in that due to weak interlayer adhesive strength between the first layer

and the second layer, interlayer separation between the first layer and the second layer of the film often occurs and this readily causes film remaining, that is, film flakes remain ununiformly, or the like.

The present invention has been made under these circumstances and an object of the present invention is to provide an easily openable film satisfactory in all of its low-temperature heat-sealing property, heat resistance, and no-film remaining property, an easily openable film satisfactory in all of its low-temperature heat-sealing property, low odorousness, and no-film remaining property, and a cover material and a container each using the film.

DISCLOSURE OF THE INVENTION As a result of intensive investigations for an easily openable film excellent in the low-temperature heat-sealing property and heat resistance, free from ununiform film remaining, that is, film flakes do not remain or film fibers are not formed between the film and the peeled face, and ensured to reveal superior appearance after peeling, the present inventors have found that the above-described object can be attained by using a film comprising the following constitutions. The present invention has been accomplished based on this finding.

That is, the present invention relates to an easily openable film in the following (1).

(1) An easily openable film having a seal layer and a support layer adjacent to the seal layer, said seal layer comprising a seal material containing (A) an ethylene-based copolymer of an ethylene and an alkyl (meth) acrylate or a vinyl ester and (B) a polyester resin, and

said support layer comprising a support material containing (A) said ethylene-based copolymer and (C) a polyolefin resin.

In addition, as a result of intensive investigations for an easily openable film excellent in the low-temperature heat-sealing property and low odorousness, free from uniform film remaining, that is, film flakes do not remain or film fibers are not formed between the film and the peeled face, and ensured to reveal superior appearance after peeling, the present inventors have found that the above-described object can be attained by using a film comprising the following constitutions. The present invention has been accomplished based on this finding.

That is, the present invention relates to an easily openable film in the following (2).

(2) An easily openable film having a seal layer containing (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate component and (B) a polyester resin.

In addition, the present invention relates to an easily openable film in the following (3) to (6).

(3) The easily openable film as described in (1) or (2), wherein the melting point of said polyester resin (B) is from 100 to 135°C.

(4) The easily openable film as described in (1), wherein said seal material comprises from 40 to 90% by mass of said ethylene-based copolymer (A) and from 60 to 10% by mass of said polyester resin (B), provided that the total of the ethylene-based copolymer (A) and the polyester resin (B) is 100 parts by mass.

(5) The easily openable film as described in (2), wherein said seal material comprises from 40 to 90% by mass of said ethylene-based copolymer (A') and from 60 to 10% by mass of said polyester resin (B), provided that the total of the ethylene-based

copolymer (A') and the polyester resin (B) is 100 parts by mass.

(6) The easily openable film as described in (2), wherein a support layer containing (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate component and (C) a polyolefin resin is provided adjacently to said seal layer.

In addition, the present invention relates to a cover material in the following (7) and a container in the following (8) to (10).

(7) A cover material using the easily openable film as described in (1) or (2).

(8) A container comprising said cover material as described in (7).

(9) A container comprising a container body made of polyester and said cover material as described in (7).

(10) A container comprising a container body made of polycarbonate and said cover material as described in (7).

According to the present invention, an easily openable film satisfactory in all of its low-temperature heat-sealing property, heat resistance, and no-film remaining property, an easily openable film satisfactory in all of its low-temperature heat-sealing property, low odorousness, and no-film remaining property, and a cover material and a container each using the film can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. In the following, unless otherwise indicated, the"parts"and"%"denoting the amount ratio are based on mass.

First, the easily openable film of the present invention will be explained.

The first easily openable film of the present invention has a seal layer and a support layer adjacent to the seal layer.

The seal layer comprises a seal material containing (A) an ethylene-based copolymer comprising an ethylene and an alkyl (meth) acrylate or a vinyl ester (hereinafter sometimes simply referred to as a"component (A) ") and (B) a polyester resin (hereinafter sometimes simply referred to as a"component (B)").

The"alkyl (meth) acrylate" as used herein includes alkyl acrylate and alkyl methacrylate.

The component (A) in the seal material is a copolymer obtained by copolymerizing an ethylene and an alkyl (meth) acrylate or a vinyl ester.

That is, the component (A) includes a copolymer of an ethylene and an alkyl (meth) acrylate (ethylene-alkyl acrylate copolymer) and a copolymer of an ethylene and a vinyl ester (ethylene-vinyl ester copolymer).

In the component (A), either an ethylene-alkyl acrylate copolymer or an ethylene-vinyl ester copolymer may be used alone or these copolymers may be used in combination.

The alkyl group in the alkyl (meth) acrylate is not particularly limited, but an alkyl group having 12 or less carbon atoms is generally used.

Examples of the alkyl (meth) acrylate having such an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate and octyl (meth) acrylate.

That is, examples of the component (A) using such an alkyl (meth) acrylate include an ethylene-methyl (meth) acrylate copolymer, an ethylene-ethyl (meth) acrylate copolymer, an ethylene-propyl (meth) acrylate copolymer, an ethylene-butyl (meth) acrylate copolymer, an ethylene-hexyl (meth) acrylate copolymer, an ethylene-cyclohexyl (meth) acrylate copolymer and an ethylene-octyl (meth) acrylate copolymer.

Among the alkyl (meth) acrylates, those having 4 or less carbon atoms are preferred because of their excellent heat resistance. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate and butyl (meth) acrylate are preferred, and methyl (meth) acrylate is more preferred. When methyl (meth) acrylate is used, methyl acrylate is still more preferred.

The vinyl ester is also not particularly limited and examples thereof include vinyl acetate and vinyl butyrate, with vinyl acetate being preferred.

In the component (A), those alkyl (meth) acrylates and vinyl esters may be used individually or in combination of two or more thereof, but in view of not only stabilization of heat-seal strength but also low odorousness of film, sole use of methyl (meth) acrylate is preferred, and sole use of methyl acrylate is more preferred.

In the component (A), the ethylene content is preferably from 70 to 90% by mass, and more preferably from 80 to 85% by mass. If the content is less than 70 % by mass, the heat resistance may not be satisfactory or blocking of the easily openable film may readily occur, whereas if the ethylene content exceeds 90% by mass, this may cause bad dispersion between the component (A) and the polyester resin (B) when these are mixed, and the heat-seal strength may not be stably expressed.

The melt flow rate (hereinafter referred to as"MFR") of the component (A) is not particularly limited but is generally from 0.1 to 100 g/10 min, preferably from 1 to 30 g/10 min.

In the present invention, unless otherwise indicated, the MFR is a value measured according to JIS K 7210 under the conditions that the temperature is 190°C and the load of 21. 18 N.

Examples of the commercial product which can be used for the component (A) include J-REX (registered trademark) EVA and REXPEARL (registered trademark) both

produced by Japan Polyolefins Co. , Ltd. , and Acryft (registered trademark) produced by Sumitomo Chemical Co. , Ltd. and so on.

The polyester resin (B) in the seal material is a thermoplastic polyester resin and this is a polycondensate of a polybasic acid and a polyhydric alcohol.

Examples of the polybasic acid include, but are not limited to, a phthalic acid, an isophthalic acid, a terephthalic acid, a maleic acid, a succinic acid, an adipic acid and a 2,6-naphthalenedicarboxylic acid.

Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, glycerin, trimethylolpropane, 1,3-butanediol, 1,4-butanediol, pentaerythritol, neopentyl glycol, 1, 6-hexanediol and 1,4-cyclohexyldimethanol.

These polybasic acids and polyhydric alcohols can be used in an arbitrary combination, that is, an arbitrary polybasic acid and an arbitrary polyhydric alcohol may be used in combination, or one or more polybasic acids and one or more polyhydric alcohols may be used.

The melting point of the component (B) is preferably from 100 to 135°C for obtaining an easily openable film having good low-temperature heat-sealing property and good heat resistance. The melting point as used herein is a value measured according to JIS K 7121 by the differential scanning calorimetry (DSC).

The MFR of the component (B) is not particularly limited but is generally from 0.1 to 100 g/10 min, preferably from 1 to 30 g/10 min. Examples of the commercial product which can be used for the component (B) include VYLON (registered trademark) produced by Toyobo Co. , Ltd.

The seal material preferably comprises from 40 to 90% by mass of the ethylene-based copolymer (A) and from 60 to 10% by mass of the polyester resin (B).

That is, the ratio between the ethylene-base copolymer (A) and the polyester resin (B)

contained in the seal material is 40 to 90/60 to 10, more preferably 60 to 80/40 to 20.

If the ratio of the component (A) contained exceeds 90, a desired heat-seal strength may not be obtained, whereas if the ratio of the component (A) contained is less than 40, the heat-seal strength may have a large dispersion or the interlayer adhesive strength between the seal layer and the support layer may become weak, as a result, film remaining is readily caused.

The ratio of the MFR of the component (A) to the MFR of the component (B) is not particularly limited, but the MFR of component (A) /MFR of component (B) is preferably from 0.3 to 3 for obtaining good dispersion of respective components in the seal material and in turn stabilization of the heat-seal strength.

The support layer comprises a support material containing (A) the above-described ethylene-based copolymer and (C) a polyolefin resin (hereinafter sometimes simply referred to as a"component (C)").

Here, the ethylene-based copolymer (A) in the support material is the same copolymer as the ethylene-based copolymer (A) in the seal material. That is, when the component (A) in the seal material is an ethylene-alkyl (meth) acrylate copolymer, the component (A) used in the support material is an ethylene-alkyl (meth) acrylate copolymer, and when the component (A) in the seal material is an ethylene-vinyl ester copolymer, the component (A) used in the support material is an ethylene-vinyl ester copolymer.

In the support material, preferred ranges and examples regarding the ethylene component content in the component (A), the MFR of the component (A) and the commercial product which can be used for the component (A) are the same as those of the component (A) in the seal material, but the ethylene-based copolymers (A) in the seal material and in the support material need not be the same resin, that is, they may be

copolymers differing in the kind of compound used as the alkyl methacrylate, the kind of compound used as the vinyl ester, the ethylene content, the MFR, or the like. However, when the same copolymer is used for the seal material and the support material, the interlayer adhesive strength between the seal layer and the support layer is more elevated reducing the occurrence of film remaining and, therefore, this is preferred.

In the support layer, in addition to the same copolymer as the ethylene-based copolymer (A) used for the seal layer, an ethylene-based copolymer (A) different from the ethylene-based copolymer (A) used for the seal material may be further contained if its content is less than 30% by mass based on the entire mass of the component (A). If the different copolymer occupies 30% by mass or more of the component (A), the interlayer adhesive strength between the support layer and the seal layer tends to be weak readily causing film remaining and, therefore, this is not preferred.

Examples of the polyolefin resin (C) for use in the support material include high-density polyethylene, low-density polyethylene, linear low-density polyethylene and polypropylenes called homo, random and block.

Among these, preferred are linear low-density polyethylene and high-density polyethylene because of their high compatibility with the ethylene-based copolymer (A) and high heat resistance.

The polyolefin resin (C) can be produced by a high-pressure process using a peroxide initiator or a low/middle-pressure process using a Ziegler-Natta catalyst, a metallocene catalyst or the like. The production process is not particularly limited and various processes such as bulk, slurry, vapor phase or solution methods can be used.

The MFR of the polyolefin resin (C) is not particularly limited but is generally from 0.1 to 100 g/10 min, preferably from 0.1 to 50 g/10 min.

The blending ratio of the component (A) to the component (C) in the support

material is not particularly limited, but the blending ratio of the component (A) is preferably from 40 to 90% by mass, and more preferably from 60 to 80% by mass, per 100% by mass in total of the component (A) and the component (C). If the blending ratio of the component (A) is less than 40% by mass, the interlayer adhesive strength between the seal layer and the support layer may decrease to readily cause interlayer separation and film remaining is sometimes caused, whereas if it exceeds 90% by mass, the heat resistance may decrease.

The first easily openable film of the present invention may have a form of two-layer film comprising only the seal layer and the support layer or multilayer film consisting of three or more layers where the seal layer, the support layer, and other layers are laminated.

In a more preferred embodiment of the first easily openable film of the present invention, a support outer layer, which is a polyolefin layer comprising (C) a polyolefin resin, is provided on the support layer in the side opposite the seal layer to come adjacent to the support layer.

When such a support outer layer is provided, this facilitates the lamination of the first easily openable film of the present invention with a substrate comprising polyester, polyamide, polypropylene or the like. Also, the heat resistance is more increased.

Specific examples of the substrate include a uniaxially or biaxially stretched film comprising polyester, polyamide, polypropylene or the like, a film obtained by vapor-depositing aluminum, silica, alumina or the like on such a uniaxially or biaxially stretched film, paper and an aluminum foil. One substrate may be used or two or more substrates may be laminated. This substrate can be subjected to a treatment such as coloration or printing and therefore, an easily openable film excellent in decorative design, barrier property, light-shielding property, pinhole resistance and curling

resistance can be provided.

Examples of the method for laminating the easily openable film with the substrate include, but are not limited to, a method of previously shaping the first easily openable film of the present invention and laminating it with the substrate by dry lamination, a method of laminating the easily openable film with the substrate through a polyethylene or the like by sandwich lamination, and a method of directly laminating the resins constituting the easily openable film of the present invention on the substrate by a multilayer extrusion lamination molding machine.

The thickness of the first easily openable film of the present invention is not particularly limited but is preferably from 10 to 100 u. m, and within this range, the low-temperature heat-sealing property, heat-seal strength and the like are satisfactory.

The thickness is more preferably from 20 to 90 u. m, still more preferably from 25 to 80 , um.

The ratio of the thickness of the seal layer to the thickness of the support layer is preferably (thickness of the seal layer): (thickness of the support layer) = 10 to 40 : 90 to 60 (provided that the total of the thickness of the seal layer and the thickness of the support layer is 100), and more preferably (thickness of the seal layer): (thickness of the support layer) = 20 to 40: 80 to 60. In the case where the support outer layer is provided in addition to the support layer, the ratio in the thickness is preferably (thickness of the seal layer): (thickness of the support layer): (thickness of the support outer layer) = 10 to 40: 10 to 30: 30 to 80, and more preferably (thickness of the seal layer): (thickness of the support layer): (thickness of the support outer layer) = 20 to 40: 10 to 30 : 30 to 70.

The composition of the seal material, support material or the like constituting each layer such as seal layer or support layer may contain a resin other than the

components (A), (B) and (C) within the range of not departing from the object of the present invention, that is, not impairing the low-temperature heat-sealing property, heat resistance and no-film remaining property of the easily openable film.

Specific examples of such resin include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene and polybutene, ethylene-unsaturated monocarboxylic acid copolymers and metal salts thereof, such as ethylene- (meth) acrylic acid copolymer, various elastomers such as ethylene-propylene copolymerized elastomer, ethylene-1-butene copolymerized elastomer, styrene-butadiene copolymerized elastomer and their hydrogenated products, and known adhesive resins used as a tackifier resin in the so-called hot melt adhesive field, such as aliphatic hydrocarbon resin, alicyclic hydrocarbon resin, aromatic hydrocarbon resin, polyterpene-based resin and rosins.

In the seal material, support material or the like for use in the present invention, arbitrary additives such as antioxidant, antistatic agent, antiblocking agent, coloring agent, ultraviolet absorbent and organic or inorganic filler may be blended according to the purpose.

In the present invention, the seal material, support material or the like constituting each layer is prepared by simultaneously or successively mixing the components (A), (B) and (C), additives and resins. Specific examples of the method therefor include a method of mixing respective components by a tumbler, a Henschel mixer or the like and charging these into a molding machine, and a method of mixing respective components by a tumbler or a Henschel mixer and then melt-mixing these by a single screw extruder, a twin screw extruder, a Banbury mixer, a kneader or the like.

The method for producing the first easily openable film of the present invention is not particularly limited, but examples thereof include a method of producing the film

by charging the seal material, support material and the like into a multilayer T-die molding machine or a multilayer inflation molding machine and co-extruding the materials, and a method of previously shaping a film of either one of the seal layer or the support layer from the seal material or support material and melt-laminating another layer on the film by an extrusion lamination method.

As described above, in the first easily openable film of the present invention, the ethylene-based copolymer (A) and the polyester resin (B) are used in the seal material and the ethylene-based copolymer (A) and the polyolefin resin (C) are used in the support material, so that the easily openable film can have good low-temperature heat-sealing property and heat resistance high enough to cause no deformation at a sterilization treatment such as boiling and retorting, and can successfully maintain the heat-seal strength even under the conditions such as sterilization treatment.

Furthermore, in the first easily openable film of the present invention, the ethylene-based copolymer (A) and the polyester resin (B) are used in the seal material and the same ethylene-based copolymer (A) as the ethylene-based copolymer (A) in the seal material is used in the support material, so that when heat-sealed, high adhesive strength can be exhibited between the seal layer and the support layer and the seal layer can be free from cohesive failure, as a result, separation readily occurs at the interface between the seal layer and the container body. In this way, interlayer separation or cohesive failure does not arise but interface separation takes place when applied to a container and peeled off therefrom, so that excellent no-film remaining property and good peeling appearance can be achieved.

Here, when (B) a polyester resin having a melting point of 100 to 135°C is used, the low-temperature heat-sealing property and the heat resistance both can be easily attained.

Furthermore, when the ratio between the ethylene-base copolymer (A) and the polyester resin (B) contained in the seal material is 40 to 90/60 to 10, the easily openable film can hold the heat-seal strength and at the same time, can be prevented from dispersion of the heat-seal strength.

The second easily openable film of the present invention has a seal layer containing (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate component (hereinafter sometimes simply referred to as "component (A')") and (B) a polyester resin (hereinafter sometimes simply referred to as "component (B)").

The"methyl (meth) acrylate" as used herein includes methyl acrylate and methyl methacrylate.

The second easily openable film of the present invention may be a single-layer film comprising only the seal layer or may be a multilayer film obtained by laminating the seal layer and other layers.

In the present invention, the component (A') for use in the second seal layer comprises an ethylene component and a methyl (meth) acrylate component. Specific examples of the component (A') include an ethylene-methyl acrylate copolymer and an ethylene-methyl methacrylate copolymer. One of these copolymers may be used alone or these two copolymers may be used in combination, but an ethylene-methyl acrylate copolymer is preferably used alone in view of not only stability of the heat-seal strength but also low odorousness of the easily openable film.

In the component (A') for use in the present invention, the content of the ethylene component is preferably from 70 to 90% by mass, more preferably from 80 to 85%. If the content is less than 70% by mass, the heat resistance may not be satisfied or blocking of the easily openable film may readily occur, whereas if the ethylene

component content exceeds 90% by mass, this may cause bad dispersion with the polyester resin (B) mixed and the heat-seal strength may not be stably expressed.

The MFR of the component (A') is not particularly limited but is generally from 0.1 to 100 g/10 min, preferably from 1 to 30 g/10 min.

Examples of the commercial product which can be used for the component (A') include REXPEARL (registered trademark) produced by Japan Polyolefins Co. , Ltd. and Acryft (registered trademark) produced by Sumitomo Chemical Co. , Ltd.

In the present invention, the polyester resin (B) for use in the seal layer of the second easily openable film is the same thermoplastic polyester resin as used in the first easily openable film, and this is a polycondensate of a polybasic acid and a polyhydric alcohol.

The seal layer can be obtained by mixing at least the ethylene-based copolymer (A') and the polyester resin (B).

In the seal layer, the mixing ratio of the ethylene-based copolymer (A') to the polyester resin (B) is preferably 40 to 90/60 to 10, more preferably 60 to 80/40 to 20. If the mixing ratio of the component (A') exceeds 90, a desired heat-seal strength may not be obtained and this is not preferred, whereas if the mixing ratio of the component (A') is less than 40, the heat-seal strength may have a large dispersion.

The ratio of the MFR of the component (A') to the MFR of the component (B) is not particularly limited, but the MFR of component (A')/MFR of component (B) is preferably from 0. 3 to 3 for obtaining good dispersion of mixed resins and in turn stabilization of the heat-seal strength.

In the second easily openable film of the present invention, a support layer containing (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate component and (C) a polyolefin resin (hereinafter sometimes

simply referred to as a"component (C) ") is preferably provided adjacently to the seal layer.

By providing the support layer, in addition to the low-temperature heat-sealing property, low odorousness and no-film remaining property, when heat-sealing is applied, the temperature range where good heat-seal strength can be maintained is broadened.

That is, the heat resistance of the heat-seal is enhanced, and therefore, when such an easily openable film is used, a container capable of tightly enclosing and holding the contents even during a sterilization treatment such as boiling or retorting can be constituted.

At this time, the support layer must be adjacent to the seal layer so that the support layer can successfully support the seal layer under the temperature conditions during a sterilization treatment.

The above-described support layer has a high interlayer adhesive strength to the seal layer, and therefore, the film remaining problem does not occur.

In the present invention, the ethylene-based copolymer (A') for use in the support layer of the second easily openable film comprises, similarly to the ethylene-based copolymer (A') for use in the seal layer, an ethylene component and a methyl (meth) acrylate component. In the support layer, preferred ranges and examples regarding the ethylene component content in the component (A'), the MFR of the component (A') and the commercial product which can be used for the component (A') are the same as those of the component (A') in the seal layer, but the ethylene-based copolymers (A') in the seal layer and in the support layer need not be the same resin, that is, may be methyl methacrylate and methyl acrylate or may be copolymers differing in the ethylene component content, MFR or the like. However, when the same resin is used for the seal layer and the support layer, the interlayer adhesive strength between the

seal layer and the support layer is more elevated reducing the occurrence of film remaining and, therefore, this is preferred.

When the second easily openable film comprises the support layer, the polyolefin resin (C) used in the support layer includes the polyolefin resin (C) used for the support layer of the first easily openable film.

Among these, preferred are linear low-density polyethylene and high-density polyethylene because of their high compatibility with the ethylene-based copolymer (A') and high heat resistance.

When a support layer is provided with the second easily openable film, the mixing ratio of the component (A') to the component (C) is not particularly limited, but the blending ratio of the component (A') is preferably from 40 to 90% by mass, and more preferably from 60 to 80% by mass, per 100% by mass in total of the component (A') and the component (C). If the blending ratio of the component (A') is less than 40% by mass, the interlayer adhesive strength between the seal layer and the support layer may decrease to readily cause interlayer separation and film remaining is liable to occur, whereas if it exceeds 90% by mass, the heat resistance may decrease.

In the second easily openable film of the present invention, when a support layer is provided, a support outer layer comprising (C) a polyolefin resin is preferably provided on the support layer in the side opposite the seal layer to come adjacent to the support layer.

When such a support outer layer is provided, this facilitates the lamination of the second easily openable film of the present invention with a substrate comprising polyester, polyamide, polypropylene or the like. Also, the heat resistance is more increased.

Specific examples of the substrate used in the second easily openable film

include the substrates used in the first easily openable film.

In addition, the second easily openable film and the substrate are laminated in the same manner as described in the first easily openable film.

The thickness of the second easily openable film of the present invention is not particularly limited but is preferably from 10 to 100 u. m and within this range, the low-temperature heat-sealing property, heat-seal strength and the like are satisfactory.

The thickness is more preferably from 20 to 90 urn, and still more preferably from 25 to 80, um.

In the case of the second easily openable film further having the support layer, the ratio of the thickness of the seal layer to the thickness of the support layer is preferably (thickness of the seal layer): (thickness of the support layer) = 10 to 40: 90 to 60 (provided that the total of the thickness of the seal layer and the thickness of the support layer is 100), and more preferably (thickness of the seal layer): (thickness of the support layer) = 20 to 40: 80 to 60. In the case where the support outer layer is provided in addition to the support layer, the ratio in the thickness is preferably (thickness of the seal layer): (thickness of the support layer): (thickness of the support outer layer) = 10 to 40: 10 to 30 : 30 to 80, and more preferably (thickness of the seal layer): (thickness of the support layer): (thickness of the support outer layer) = 20 to 40: 10 to 30 : 30 to 70.

In each layer such as the seal layer of the second easily openable film of the present invention, a resin other than the components (A'), (B) and (C) may be blended within a range which does not depart from the object of the present invention, that is, not impairing the low-temperature heat-sealing property, low odorousness, and no-film remaining property.

Specific examples of such resins include polyolefin resins, ethylene-unsaturated

monocarboxylic acid copolymers and metal salts thereof, various elastomers, and known adhesive resins used as a tackifier resin in the so-called hot melt adhesive field, etc., which are used in the first easily openable film.

In each layer such as the seal layer and the support layer of the second easily openable film of the present invention, similarly in the first easily openable film, arbitrary additives such as antioxidants, antistatic agents, antiblocking agents, coloring agents, ultraviolet absorbents and organic or inorganic fillers may be blended according to the purpose.

In the present invention, the composition constituting each layer is prepared by simultaneously or successively mixing the components (A'), (B) and (C), additives and resins. Specific examples of the method therefor include a method of mixing respective components by a tumbler, a Henschel mixer or the like and charging these into a molding machine, and a method of mixing respective components by a tumbler or a Henschel mixer and then melt-mixing these by a single screw extruder, a twin screw extruder, a Banbury mixer, a kneader or the like.

The method for producing the second easily openable film of the present invention is not particularly limited. A method of producing the film by an extrusion method using a T-die molding machine or an inflation molding machine is generally employed.

When the second easily openable layer comprises the support layer, the method for producing the second easily openable film having a support layer, includes, for example, a method of producing the film by a co-extrusion method using a multilayer T-die molding machine or a multilayer inflation molding machine, and a method of previously shaping a film of either one of the seal layer or the support layer and melt-laminating another layer on the film by an extrusion lamination method.

As described above, in the second easily openable film of the present invention, (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate component and (B) a polyester resin are used in the seal layer, so that the second easily openable film can be free from emission of an unpleasant odor and ensured to exhibit good low-temperature heat-sealing property, and when applied to a container, excellent no-film remaining property.

Here, when (B) a polyester resin having a melting point of 100 to 135°C is used, the low-temperature heat-sealing property and the heat resistance both can be easily attained.

Furthermore, when the mixing ratio of the ethylene-base copolymer (A') to the polyester resin (B) in the seal layer is 40 to 90/60 to 10, the easily openable film can hold the heat-seal strength and, at the same time, and dispersion of the heat-seal strength can be prevented.

When a support layer containing (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate component and (C) a polyolefin resin is further provided adjacently to the seal layer, the easily openable film can have heat resistance suitable for a sterilization treatment such as boiling or retorting, in addition to the low-temperature heat-sealing property and no-film remaining property.

The cover material of the present invention will be explained below.

The cover material of the present invention is constituted by using the first or second easily openable film of the present invention and this is mainly fitted to a container body such as a cup or tray to constitute an easily openable container.

In applying the first easily openable film of the present invention to the cover material, the first easily openable film may have a form of a two-layer film comprising the seal layer and the support layer.

In applying the second easily openable film of the present invention to the cover material, the second easily openable film may have a form of a single layer film comprising the seal layer and a two-layer film comprising the seal layer and the support layer.

However, in general, in the first or second easily openable film, since decorative design, barrier property, light-shielding property, pinhole resistance, curling resistance and the like can be easily imparted, the first or second easily openable film comprising the substrate via the support outer layer is preferably used.

The cover material comprising the first easily openable film of the present invention has the first easily openable film, and therefore, is satisfactory in all of the low-temperature heat-sealing property to a container body, the peeling appearance and the heat resistance.

The cover material comprising the second easily openable film of the present invention has the second easily openable film, and therefore, is satisfactory in all of the low-temperature heat-sealing property to a container body, the peeling appearance and the low odorousness. In addition, when the second easily openable film comprises the support layer, the cover material comprising the second easily openable film has also excellent heat resistance.

The container of the present invention will be explained below.

This container can be constituted, for example, by the cover material of the present invention and a cup-or tray-shaped container body having a bonding part in a shape capable of closely contacting with the cover material, such as a flange, and a housing part for housing the content such as food. When this container is made of the first easily openable film, the seal layer side of the first easily openable film constituting the cover material is closely contacted with the bonding part of the container body.

When this container is made of the second easily openable film comprising the support layer, the seal layer side of the second easily openable film constituting the cover material is closely contacted with the bonding part of the container body, similarly in the container made of the first easily openable film.

After the content is filled or stored in the housing part, the cover material is disposed to come into contact with the bonding part of the container body and the cover material is heat-sealed to the container body by using a hot plate, a high frequency, an ultrasonic wave or the like, whereby the container of the present invention can be fabricated.

Examples of the resin for the container body which can be used include polyester, polystyrene, polypropylene, polycarbonate and polyvinyl chloride. Among these, polyester or polycarbonate is preferred, because this resin is excellent particularly in transparency, low-temperature heat-sealing property and heat-seal strength.

Polyester comprises a unit originated from terephthalic acid and glycol.

Polyester contains A-PET having a low degree of crystalinity, PETG which is made by copolymerization of units generated from 1,4-cyclohexane dimethanol, and C-PET having a high degree of crystalinity. In addition, a B-PET sheet and a B-PET container (marketed by INABATA & Co. Ltd. ) are also used.

When the cover material made of the easily openable film of the present invention is provided with the container body made of polyester, no film, such as film in a flake state or a fiberous state, remains on the peeled face of the container body after peeling off the cover material. The peeled face has excellent appearance, which is similar to the surface before sealing by heat.

When the cover material made of the easily openable film of the present invention is provided with the container body made of polycarbonate, a peeling mark, in

which the seal resin remains uniform is formed on either of the container body and the cover material after peeling off. Such uniform peeling marks have an excellent appearance and this shows that the container body and the cover material are reliably sealed before peeling. Confirmation of the seal conditions by the peeling mark is very important in the medical field. Therefore, the easily openable film, the cover material, and the container of the present invention are preferably used in the medical field which requires the formation of uniform peeling marks, in addition to the food field in which peeling marks and film remaining on the peeled face are not needed.

A laminated body comprising an inner face layer formed of the above-described resin used for the container body, including polyethylene, and a paper, aluminum foil, and a barrier resin layer may also be used for the container body.

The container where the cover material is heat-sealed to the bonding part of the container body at a low temperature facilitates storage of the content in a closed state, can be easily opened and ensures excellent appearance of the bonding part after opening, that is, ensures excellent peeling appearance.

In particular, since the container made of the first easily openable film is excellent in heat resistance, the container can be subsequently subjected to a sterilization treatment such as boiling and retorting.

In particular, the container made of the second easily openable film has low odorousness.

Moreover, when the container is made of the second easily openable film comprising the support layer, the container is excellent in the heat resistance and therefore, can be subsequently subjected to a sterilization treatment such as boiling and retorting.

Here, when a container body comprising a polyester-based resin is used, a

container which adsorbs food flavor less and is satisfactory in its low-temperature heat-sealing property, peeling appearance, and heat resistance of the cover material can be provided. When a container body comprising polycarbonate is used, a container, which is satisfied in both heat resistance and transparency, can be provided.

The container of the present invention can be suitably used for housing, for example, food such as tofu, gelidium, yogurt, jelly, coffee drinks, lactic acid beverages, instant noodles, Japanese confectionery and processed meat, or contents such as medicaments, medical appliances and toners.

Examples The present invention is described below by referring to Examples, but the present invention is not limited to these Examples.

Resin In the following, the MFR was measured according to JIS K 7120 under the conditions that the temperature was 190°C and the load was 21. 18 N.

(A) and (A') Ethylene-Based Copolymer El : Ethylene-methyl acrylate copolymer having an MFR of 6 g/10 min and a methyl acrylate content of 20% by mass ("REXPEARL RB"4200, produced by Japan Polyolefins Co. , Ltd.) E2: Ethylene-methyl methacrylate copolymer having an MFR of 7 g/10 min and a methyl methacrylate content of 15% by mass ("Acryft"WH302, produced by Sumitomo Chemical Co. , Ltd.) E3: Ethylene-vinyl acetate copolymer having an MFR of 2 g/10 min and a vinyl

acetate content of 15% by mass ("J-REX EVA"VE430A, produced by Japan Polyolefins Co. , Ltd.) E4: Ethylene-methyl methacrylate copolymer having an MFR of 7 g/10 min and a methyl methacrylate content of 18% by mass ("Acryft WH303", produced by Sumitomo Chemical Co. , Ltd.) (B) Polyester Resin ES 1 : Polyester resin having an MFR of 13 g/10 min and a melting point of 126°C ("VYLON"GM-913, produced by Toyobo Co. , Ltd.) ES2: Polyester resin having an MFR of 10 g/10 min and a melting point of 112°C ("VYLON"GM-990, produced by Toyobo Co. , Ltd.) (C) Polyolefin Resin PO 1 : High-density polyethylene having an MFR of 3.5 g/10 min and a density of 0.955 g/cm3 ("J-REX HD", produced by Japan Polyolefins Co. , Ltd.) P02 : Linear low-density polyethylene having an MFR of 10 g/10 min and a density of 0.922 g/cm3 ("HARMOREX LL", produced by Japan Polyolefins Co. , Ltd.) P03 : Linear low-density polyethylene having an MFR of 3.5 g/10 min and a density of 0.905 g/cm3 ("HARMOREX LL NC524A", produced by Japan Polyolefins Co. , Ltd.) P04 : Linear low-density polyethylene having an MFR of 3.5 g/10 min and a density of 0.921 g/cm3 ("HARMOREX LL NC574R", produced by Japan Polyolefins Co. , Ltd.) Other Resins RE1 : Ethylene-ethyl acrylate copolymer having an MFR of 6 g/10 min and an ethyl acrylate content of 18% by mass ("NUC-6170", produced by Nippon Unicar Company

Limited) RE2: Ethylene-ethyl acrylate copolymer having an MFR of 5 g/10 min and an ethyl acrylate content of 19% by mass ("EVAFLEX-EEAA702", produced by DuPont-Mitsui Polychemicals Co. , Ltd.) RE3 : Ethylene-vinyl acetate copolymer having an MFR of 2 g/10 min and a vinyl acetate content of 15% by mass ("J-REX EVAVE430A", produced by Japan Polyolefins Co. , Ltd.) RE4: Ionomer having an MFR of 3 g/10 min and a density of 0.940 g/cm3 ("HIMILLAN", Zn ion type, produced by DuPont-Mitsui Polychemicals Co. , Ltd.) Production of Multilayer Easily Openable Film Various resins were mixed by a Henschel mixer to give a composition shown in Table 1, thereby preparing a seal material for forming a seal layer, a support material for forming a support layer and depending on the case, a polyolefin resin for forming a polyolefin layer. These mixed resins were charged into a three-layer T-die molding machine and shaped at a temperature of 210°C to obtain an easily openable film having a seal layer and a support layer constituted as shown in Table 1. The surface of the multilayer easily openable film in the side opposite the seal layer, that is, the surface of the support or polyolefin layer was subjected to a corona treatment and thereto, a biaxially stretched polyethylene terephthalate film having a thickness of 12 u. m was dry-laminated as the substrate to form a laminated body. This laminated body was used as the cover material sample.

In Table 1,"%"denotes"% by mass".

Table 1 Film name Seal layer Support layer Support outer layer (thickness : µm) (thickness : µm) (thickness: u. m) EI : 70% EI : 80% F1 ES1 : 30% P01 : 20% (10) (40) E2: 50% E1 : 90% F2 ES 1 : 50% PO1 : 10% (10) (40) E3: 60% EI : 90% F3 ES2: 40% PO1 : 10% (10) (40) E1 : 70% EI : 90% PO2:100% F4 ES1 : 30% PO1 : 10% (30) (10) (10) E1 : 50% E1 : 90% PO1 : 10% F5 ES1 : 50% PO1 : 10% P02 : 90% (10) (10 (30) EI : 70% E1 : 80% F6 ES1 : 30% P01 : 20% (10) (40) E1 : 70% EI : 90% PO4:100% F7 ES1 : 30% P03 : 10% (10) (10) (30) E1 : 70% E1 : 90% RF1 P02 : 30% PO1 : 10% (10) (40) EI : 70% PO2:100% RF2 ES1:30% (40) (10) Ex : 50% E1 : 100% RF3 ES2:50% (40) (10) ES1:100% E1: 70% E1:90% RF4 ES1:30% PO1 : 10% (10) (30)

Production of Single-Layer Easily Openable Film Easily openable films comprising only a seal layer (hereinafter referred to as a "single-layer easily openable film") were produced.

Various resins were mixed by a Henschel mixer to give a composition shown in Table 2, charged into a single-layer T-die molding machine and shaped at a temperature

of 210°C to obtain a single-layer easily openable film having a thickness shown in Table 2.

One surface of the obtained single-layer easily openable film was subjected to a corona treatment and thereto, a biaxially stretched polyethylene terephthalate film having a thickness of 12 pm was dry-laminated as the substrate to form a laminated body. This laminated body was used as the cover material sample.

Table 2 Film (A') (B) (C) Other resins Film name Ethylene-based Polyester Polyolefin thickness copolymer resin resin (, um) F11 E1 : 70% ES1 : 30% 30 F12 E4: 50% ES1: 50% 40 F13 E1 : 80% ES2: 20% 50 F14 EI : 40% ES1 : 30% P03 : 30% 30 CF11 E1 : 50% ES1 : 50% 50 CF12 E4: 40% ES1 : 60% 50 RF11 ES1 : 30% P03 : 70% 30 RF12 ES1 : 30% RE1: 70% 30 RF13 ES1 : 50% RE2: 50% 40 RF14 ES2 : 20% RE3: 80% 50 RF15 ES1 : 50% P04 : 50% 50 RF16 ES1 : 50% RE4: 50% 50 RF17 ES1 : 50% PO1 : 50% 50 RCF11 ES1 : 50% P03 : 50% 50

Evaluation of Easily Openable Film The cover material obtained above was cut into a width of 20 mm and this cover material was superposed on an A-PET sheet ("TEIJIN TETRON SHEET", produced by Teijin Limited, thickness: 300 urn) or a polycarbonate sheet ("LEXAN sheet CARBOGLASS@", produced by Asahi Glass Co. , Ltd. , thickness: 2mm) by laying the seal layer of the easily openable film so as to come into contact with the sheet.

By using a hot plate, the cover material was heat-sealed by one side heating from the cover material side under a pressure of 0.2 MPa for a sealing time of 3 seconds

at a temperature of 130°C, 150°C or 170°C.

Heat-seal Strength of the multilayer easily openable film Heat-seal strength (heat resistant heat-seal strength) of the easily openable films, which were allowed to stand under high temperature conditions, were evaluated.

The heat-sealed sample was cut at both ends to obtain a 15 mm-width sample for measurement of the heat-seal strength.

The samples comprising an A-PET sheet and the sample obtained in Example 5 were heated by dipping in hot water at 85°C for 30 minutes. The samples comprising a polycarbonate sheet besides the sample of Example 5 was heated at 121 °C for 30 minutes in a hot-water sterilizer. After heating, the heated samples were left standing at a temperature of 23°C and a relative humidity of 50% for 24 hours to effect conditioning.

The heat-seal strength after conditioning was evaluated by a peel test of 180° peeling at a peeling rate of 300 mm/min and shown by the heat-seal strength per 15-mm width.

Heat-Seal Strength of Single-Layer Easily Openable Film The heat-sealed sample was cut at both ends to obtain a 15 mm-width sample for measurement of the heat seal strength. The sample was left standing at a temperature of 23°C and a relative humidity of 50% for 24 hours to effect conditioning. The heat seal strength after conditioning was measured by 180° peeling at a peeling rate of 300 mm/min and shown by the heat seal strength per 15-mm width.

Deformation Resistance of multilayer easily openable layer under Hot Water conditions: Heat resistance

When the heat-sealed sample comprises an A-PET sheet and the heat-sealed sample obtained in Example 5, the heat-sealed sample was dipped in hot water at 85°C for 30 minutes and observed with the eye and rated on the following three-stage scale.

When the heat-sealed sample comprises a polycarbonate sheet, the heat-sealed sample besides the heat-sealed sample of Example 5 was subjected to a sterilization treatment at 121 °C for 30 minutes, and this was observed with the eye and rated on the following three-stage scale. o : Not deformed. x Shrunk and deformed. xx : Once melted and solidified in the partially flowed state.

In the following Table 3, this evaluation is denoted by"Heat resistance".

Peeled Face Appearance The peeled face of the A-PET sheet or the polycarbonate sheet of the sample used for the measurement of heat-seal strength was observed with the eye and rated on the following two-stage scale.

The A-PET sheet face is smooth and no easily openable film remains. x The easily openable film remains on some parts of A-PET sheet face. z : Uniform clouded peeling mark exists on the surface of the polycarbonate sheet or the surface of the cover material.

A : The easily openable film remains in a flake state or a fiberous state on some parts of the surface of the polycarbonate sheet.

Odor of Single-Layer Easily Openable Film 10 g of the obtained single-layer easily openable film was placed in a glass

bottle and after capping the glass bottle, heated in an oven at 60°C for 1 hour. After the heating, the glass bottle with a cap was left standing at room temperature for 1 day. The glass bottle was uncapped and the odor was smelled and rated on the following four-stage scale.

(Q) : Almost no odor.

#: 0 : Odorous but not unpleasant.

A : Slightly unpleasant odor but in a level of no problem.

X: Strong unpleasant odor.

Table 3 Film Heat-seal Heat-seal Heat Peeled face Sheet name temp. strength resistance appearance (N/15mm) 130°C 11. 2 0 0 Ex. 1 F1 150°C 11. 8 0 0 A-PET sheet 170°C 12.3 0 0 130°C 13. 0 Ex. 2 F2 150°C 13.0 O 0 A-PET sheet 170°C 13. 3 0 130°C 10. 1 0 Ex. 3 F3 150°C 10. 8 0 0 A-PET sheet 170°C 11.3 130°C 11.4 0 0 Ex. 4 F4 150°C 11.3 0 0 A-PET sheet 170°C 11.8 0 0 130°C 11.8 # # Polycarbonate s e 170°C 13. 5 # # 130°C 11. 2 Ex. 6 F6 150°C 11.8 0 O A-PET sheet 170°C 12. 3 0 130°C 12.3 # # Polycarbonate Ex.7 F1 150°C 12.9 # # sheet 170°C 14.1 0 a 130°C 16.3 # # Polycarbonate Ex. 8 F2 150°C 17.0 # # sheet 170°C 17.5 0 a 130°C 16.0 # # Polycarbonate Ex.9 F5 150°C 17.7 # # sheet 170°C 18.2 0 # 130°C 11.9 0 0 Ex. 10 F7 150°C 11. 8 # # A-PET sheet 170°C 12. 3 130°C 0 # # Com. RF1 150°C 0 # # A-PET sheet Ex.1 170°C 0 # # 130°C 5.6 (interlayer) Com. RF2 150°C 4.8 (interlayer) # # A-PET sheet Ex. 2 170°C 5.5 (interlayer) # # 130°C 12. 1 xx x Com. RF3 150°C 11.5 ## # A-PET sheet Ex. 3 170°C 13.0 ## # 130°C 30. 2 Com. RF4 150°C 33.4 0 x A-PET sheet Ex. 4 170°C 33. 8 130°C 5.0 (interlayer) # # Com. Polycarbonate RF2 150°C 5.1 (interlayer) # # Ex.5 sheet 170°C 4.3 (interlayer) # # In Table 3,"interlayer"means that interlayer peeling was generated.

Table 4 Film Heat-seal Peeled face Odor Sheet name strength appearance (N/15mm) Example 11 F11 10. 3 O O A-PET sheet Example 12 F12 11.1 O A A-PET sheet Example 13 F13 8. 2 0 O A-PET sheet Example 14 F14 9.5 0 O A-PET sheet Example 15 CF11 12.0 a 0 Polycarbonate sheet Example 16 CF12 13.6 z 0 Polycarbonate sheet Com. Ex. 6 RF11 1.0 (A-PET sheet Com. Ex. 7 RF12 9.0 O x A-PET sheet Com. Ex. 8 RF13 10. 1 O x A-PET sheet Com. Ex. 9 RF14 7.5 O x A-PET sheet Com. Ex. 10 RF15 0.5 O 0 A-PET sheet Com. Ex. 11 RF16 1. 0 A-PET sheet Com. Ex. 12 RF17 0.3 O O A-PET sheet Com. Ex. 13 RCF11 2.0 A O Polycarbonate sheet

As apparent from Table 3, the easily openable films obtained in Examples 1 to 4, 6, and 10 have sufficiently high heat seal strength even when heat-sealed at 130°C, that is, a low-temperature heat-sealing property at a temperature of causing no deformation of A-PET sheet is caused, and all were satisfactory in the peeled face appearance. In addition, no film remained on the peeled face, and the appearance was excellent.

Furthermore, even when placed under hot water conditions, these films did not undergo deformation and maintained a stable heat seal strength. That is, the films had heat resistance high enough to cause no separation under conditions such as hot water.

On the other hand, as shown in Table 3, in Comparative Example 1 where the seal layer contains a polyolefin resin in place of the polyester resin (B), the heat seal strength after dipping in a hot water at 85°C was 0, that is, the cover material sample was

separated from the A-PET sheet.

In Comparative Example 2 where the support layer does not contain the ethylene-based copolymer (A), interlayer peeling was generated between the seal layer and the support layer at the peeling test and film remaining was caused in the peeling test.

In Comparative Example 3 where the support layer does not contain the polyolefin resin (C), serious deformation was caused in the evaluation of heat resistance and the peeled face appearance was poor. In Comparative Example 4 where the seal layer does not contain the ethylene-based copolymer (A) and the support layer contains a polyester resin in place of the polyolefin resin (C), an easily openable property was not exhibited due to excessively high heat seal strength and an unsatisfactory peeled face appearance was generated.

The easily openable films obtained in Examples 7 to 9 had sufficient high heat-seal strength to the polycarbonate sheet after the heat sterilization treatment at 121°C, in addition to no deformation. Moreover, in the easily openable films obtained in Examples 7 to 9, a uniformly clouded peeling mark was observed on the surface of the polycarbonate sheet or the cover material, and these easily openable films were excellent in appearance. Furthermore, it was confirmed that before peeling off the cover material, the polycarbonate sheet and the cover material were reliably sealed.

In the easily openable film obtained in Comparative Example 5, which does not contain ethylene copolymer (A) in the support layer, similarly to polyester sheet (Comparative Example 2), an interlayer peeling was generated between the seal layer and the support layer at the peeling test and film remaining was caused at the peeling test.

As apparent from Table 4, the easily openable films obtained in Examples 11 to 16 had sufficiently high heat seal strength even when this was heat-sealed at 130°C, that

is, it had a low-temperature heat-sealing property, and all were satisfied in the low odorousness and the peeled face appearance.

In the easily openable films comprising the A-PET sheet obtained in Examples 11 to 14, the peeled face was smooth, and there is no-film remaining. These easily openable films were excellent in peeled face appearance.

In the easily openable films comprising the polycarbonate sheet obtained in Examples 15 and 16, a uniformly clouded peeling mark existed on the peeled face, these easily openable films had excellent peeled face appearance. That is, it was confirmed that before peeling of the cover material, the polycarbonate sheet and the cover material are reliably sealed, in addition to having an excellent peeled face appearance.

On the other hand, in Comparative Examples 6, and 10 to 13 where (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate was not contained, peeled face appearance failure or insufficiency of heat seal strength was confirmed.

In Comparative Examples 7 to 9 where Resin RE1, RE2 or RE3 containing a copolymerization component different from the methyl (meth) acrylate component was contained, an unpleasant odor was emitted.

Furthermore, as apparent from Table 3, in Examples 1 to 10 where a support layer containing (A') an ethylene-based copolymer comprising an ethylene component and a methyl (meth) acrylate component and (C) a polyolefin resin was further provided, not only an excellent low-temperature heat-sealing property to enable heat sealing even at 130°C but also a constant heat seal strength stabilized over a wide temperature range from 130 to 170°C was exhibited. In other words, the film had a wide heat-sealable temperature width and heat resistance high enough to withstand hot water or the like.

In addition, it was confirmed that the easily openable films of Examples 1, 4 to 7,

9, and 10, which contained ethylene-methyl acrylate copolymer, generated slightly unpleasant odor but in a level of no problem (stage: 0 in Table 4) by evaluation of odor of the easily openable films.

Industrial Applicability The easily openable film and the cover material using the film of the present invention are suitably used for a container for housing, for example, food such as tofu, gelidium, yogurt, jelly, coffee drink, lactic acid beverages, instant noodles, Japanese confectionery and processed meat, or contents such as medicaments, medical appliances and ink cartridges. In particular, when a substrate is provided in the easily openable film, the content can be made to be easily viewed by using a transparent substrate or the substrate may be subjected to, for example, printing, coloration or vapor deposition to impart decorative design, barrier property, light-shielding property, pinhole resistance, curling resistance or the like, so that the film can be suitably used for various uses.