Patent Description:
Carrier tapes used for transporting or storing electronic components such as microchips are known as packaging materials. By using the carrier tape, electronic components and the like that are difficult to handle due to their too small size can be stored and transported by accommodating them one by one in the recessed portions provided on the carrier tape.

The carrier tape has recessed portions that can accommodate electronic components and the like, and is packaged by closing the recessed portions with a cover tape.

Further, plastic containers or paper containers including an easily peelable lid material are known as packaging materials for foods and drinks such as cup noodles, jellies, and yogurts, pharmaceuticals, and the like.

As the cover tape or lid material as described above, there is a demand for an easily peelable film that can be peeled off smoothly at the time of peeling while having appropriate adhesiveness.

As an easily peelable adhesive resin composition used for such an easily peelable film, for example, an adhesive resin composition containing an ethylene-vinyl acetate copolymer and a tackifier resin is known (see, for example, <CIT>).

<CIT> discloses an easily peelable film obtained by laminating a base material film with an adhesive containing <NUM> parts by weight of an ethylene-vinyl acetate copolymer (A) having a vinyl acetate content of <NUM> to <NUM>% by weight as measured by JIS K <NUM>-<NUM> and a melt mass flow rate of <NUM> to <NUM>/<NUM> as measured by JIS K <NUM>-<NUM>, <NUM> to <NUM> parts by weight of a tackifier resin (B), and <NUM> to <NUM> parts by weight of a low-molecular-weight ethylene-vinyl acetate copolymer (C) having a viscosity of <NUM> to <NUM>, 000mPa·s as measured at <NUM> using a Brookfield viscometer.

<CIT> discloses a self-adhesive type surface protection film with its adhesive layer composed of an ethylene-based resin composition comprising <NUM> pts. of (A) an ethylene/vinyl acetate copolymer having a melt flow rate of <NUM>-<NUM>/<NUM> and containing <NUM>-<NUM> mass% of vinyl acetate and <NUM>-<NUM> pts. of (B) an ethylene/vinyl acetate copolymer having a melt viscosity level of <NUM>-<NUM> mPa. s at <NUM> as determined by the Brookfield viscometer and containing <NUM>-<NUM> mass% of vinyl acetate.

<CIT>discloses an adhesive resin composition comprising: <NUM>-<NUM> wt% of an ethylene-vinyl acetate copolymer (A) which comprises <NUM>-<NUM> wt% of ethylene residue group units and <NUM>-<NUM> wt% of vinyl acetate residue group units and which has a melt mass flow rate of <NUM>-<NUM>/<NUM> as measured by JIS K6924-<NUM>; <NUM>-<NUM> wt% of an ethylene-vinyl acetate copolymer (B) which comprises <NUM>-<NUM> wt% of ethylene residue group units and <NUM>-<NUM> wt% of vinyl acetate residue group units; <NUM>-<NUM> wt% of a low-density polyethylene (C); <NUM>-<NUM> wt% of a tackifier resin (D); and <NUM>-<NUM> wt% of an antistatic agent (E).

As a packaging material, a paper carrier tape or a paper container using paper as a base material may be used. A cover tape for a paper carrier tape and a lid material for a paper container are required to have appropriate adhesiveness (that is, adhesiveness to such an extent that the cover tape and the lid material can be easily peeled off while having necessary adhesiveness to a paper base material) and not to cause paper peeling (that is, paper of the paper base material is not peeled off and fluffed) when being peeled off from the paper base material.

According to the studies of the present inventors, it has become clear that an easily peelable film using an adhesive resin composition containing an ethylene-vinyl acetate copolymer and a tackifier resin has room for improvement in the performance balance between low temperature heat sealability to paper base material, adhesiveness to paper base material, easy peelability from paper base material, and anti-blocking property.

The present invention has been made in view of the above circumstances, and provides an easily peelable film excellent in performance balance between low temperature heat sealability to paper base material, adhesiveness to paper base material, easy peelability from paper base material, and anti-blocking property.

The present inventors have made extensive studies to achieve the above object. As a result, the present inventors have found that an easily peelable film excellent in balance between low temperature heat sealability, adhesiveness, easy peelability and anti-blocking property can be realized by using a combination of a specific ethylene-vinyl acetate copolymer, a tackifier resin and an ethylene-vinyl acetate copolymer having a specific viscosity, thereby completing the present invention.

According to the present invention, the following easily peelable film comprising an adhesive resin composition is provided.

The present invention is directed to an easily peelable film comprising:.

According to one embodiment of the easily peelable film according to the present invention,.

According to a further embodiment of the easily peelable film according to the present invention,.

According to a further embodiment of the easily peelable film according to the present invention,
the melt mass flow rate (MFR, JIS K <NUM>:<NUM>, <NUM>, <NUM> load) of the ethylene-vinyl acetate copolymer (C) is <NUM>/<NUM> or more and less than <NUM>/<NUM>.

According to a further embodiment the easily peelable film according to the present invention, further comprises:
an antistatic agent (D).

According to a preferred embodiment of the easily peelable film, when a content of the ethylene-vinyl acetate copolymer (A) is <NUM> parts by mass,
the content of the antistatic agent (D) is <NUM> parts by mass or more and <NUM> parts by mass or less.

According to the present invention, it is possible to provide an easily peelable film excellent in performance balance between low temperature heat sealability to paper base material, adhesiveness to paper base material, easy peelability from paper base material, and anti-blocking property.

<FIG> is a cross-sectional view schematically showing an example of a structure of an easily peelable film to an embodiment of the present invention.

Unless otherwise specified, "X to Y" in the numerical range represents X or more and Y or less.

An adhesive resin composition which is contained in the easily peelable film of the present invention contains an ethylene-vinyl acetate copolymer (A) in which a content of a structural unit derived from vinyl acetate is <NUM>% by mass or more and <NUM>% by mass or less, and a melt mass flow rate (MFR, JIS K <NUM>:<NUM>, <NUM>, <NUM> load) is <NUM>/<NUM> or more and <NUM>/<NUM> or less, a tackifier resin (B), and an ethylene-vinyl acetate copolymer (C) having a viscosity of <NUM>, <NUM> mPa·s or more and <NUM>, <NUM> mPa·s or less measured at <NUM> using a Brookfield viscometer.

As described above, according to the studies of the present inventors, it has become clear that an easily peelable film using an adhesive resin composition containing an ethylene-vinyl acetate copolymer and a tackifier resin has room for improvement in performance balance between low temperature heat sealability to paper base material, adhesiveness to paper base material, easy peelability from paper base material, and anti-blocking property.

The present inventors have made extensive studies to achieve the above object. As a result, the present inventors have found that an easily peelable film excellent in balance between low temperature heat sealability, adhesiveness, easy peelability and anti-blocking property can be realized by using an adhesive resin composition containing an ethylene-vinyl acetate copolymer (A), a tackifier resin (B) and an ethylene-vinyl acetate copolymer (C).

That is, according to the adhesive resin composition of the present embodiment, by containing the above components, it is possible to realize an easily peelable film excellent in performance balance between low temperature heat sealability to paper base material, adhesiveness to paper base material (for example, having appropriate adhesive strength capable of protecting contents), easy peelability from paper base material (for example, suppressing fluffing of the paper base material at the time of peeling, stably peeling the paper base material without breaking the paper base material), and anti-blocking property.

Hereinafter, each component constituting the adhesive resin composition contained in the easily peelable film according to the present embodiment will be described.

An ethylene-vinyl acetate copolymer (A) according to the present embodiment has a content of a structural unit derived from vinyl acetate of <NUM>% by mass or more and <NUM>% by mass or less, from the viewpoint of improving low temperature heat sealability and anti-blocking property.

Further, the lower limit of the content of the structural unit derived from vinyl acetate is preferably <NUM>% by mass or more, more preferably <NUM>% by mass or more, and still more preferably <NUM>% by mass or more, from the viewpoint of further improving the low temperature heat sealability.

The upper limit of the content of the structural unit derived from vinyl acetate is preferably <NUM>% by mass or less, more preferably <NUM>% by mass or less, and still more preferably <NUM>% by mass or less, from the viewpoint of further improving anti-blocking property and antistatic properties.

The content of the structural unit derived from vinyl acetate can be determined in accordance with JIS K <NUM>:<NUM> by heating a polymer in an electric oven at <NUM> or higher to decompose the polymer, and subjecting the obtained acetic acid derived from vinyl acetate to neutralization titration.

Further, the ethylene-vinyl acetate copolymer (A) according to the present embodiment has a melt mass flow rate of <NUM>/<NUM> or more and <NUM>/<NUM> or less measured at a temperature of <NUM> and a load of <NUM> in accordance with JIS K <NUM>: <NUM> from the viewpoint of improving low temperature heat sealability and easy peelability.

Further, the lower limit of the melt mass flow rate is preferably <NUM>/<NUM> or more, and more preferably <NUM>/<NUM> or more, from the viewpoint of further improving the low temperature heat sealability, heat seal strength and easy peelability.

The upper limit of the melt mass flow rate is preferably <NUM>/<NUM> or less, and more preferably <NUM>/<NUM> or less, from the viewpoint of further improving processing stability and anti-blocking property.

A method for producing the ethylene-vinyl acetate copolymer (A) according to the present embodiment is not particularly limited, and the ethylene-vinyl acetate copolymer (A) can be produced by a known method. For example, the ethylene-vinyl acetate copolymer (A) can be obtained by radical copolymerization of each polymerization component under high temperature and high pressure. Further, the ethylene-vinyl acetate copolymer (A) used may be a commercially available product.

Since the tackifier resin has a function of imparting tackiness to the resin, it is possible to easily adjust the adhesive strength of the adhesive resin composition.

The tackifier resin is selected from resins having a function of imparting tackiness. Examples of the tackifier resin include aromatic hydrocarbon resins, alicyclic hydrocarbon resins, aliphatic hydrocarbon resins, terpene resins, rosins, styrene resins, and coumarone-indene resins.

Examples of the aromatic hydrocarbon resin include resins obtained by polymerizing a fraction containing at least one vinyl aromatic hydrocarbon having <NUM> to <NUM> carbon atoms such as vinyltoluene, indene, and α-methylstyrene, and resins obtained by copolymerizing these fractions with an aliphatic hydrocarbon fraction.

Examples of the alicyclic hydrocarbon resins include resins obtained by polymerization after cyclodimerization of diene components in spent C4 to C5 fractions, resins obtained by polymerization of cyclic monomers such as cyclopentadiene, and resins obtained by nuclear hydrogenation of aromatic hydrocarbon resins (for example, hydrogenated petroleum resins).

Examples of the aliphatic hydrocarbon resin include resins obtained by polymerizing a fraction containing at least one or more mono- or di-olefins having <NUM> to <NUM> carbon atoms such as <NUM>-butene, isobutene, butadiene, <NUM>,<NUM>-pentadiene, and isoprene.

Examples of the terpene resin include α-pinene polymer, β-pinene polymer, dipentene polymer, terpene-phenol copolymer, α-pinene-phenol copolymer, and hydrogenated products thereof.

Examples of rosins include rosins such as gum rosin, wood rosin, and tall oil, and modified products thereof, and examples of modified products include products subjected to modification such as hydrogenation, disproportionation, dimerization, and esterification.

Examples of the styrene resin include resin-like polymers having a low molecular weight obtained by polymerizing styrene monomers such as styrene, vinyltoluene, α-methylstyrene, and isopropyltoluene.

The tackifier resin is preferably a resin having a softening point of <NUM> to <NUM>. Generally, when the softening point is <NUM> or higher, the effect of excellent heat resistance tends to be exhibited, and when the temperature is <NUM> or lower, the effect of imparting tackiness tends to be excellent.

The softening point of the tackifier resin may be a value measured based on the softening point testing method (ring ball method) in accordance with JIS K <NUM>:<NUM>.

The content of the tackifier resin (B) is preferably <NUM> part by mass or more, more preferably <NUM> parts by mass or more, and still more preferably <NUM> parts by mass or more, based on <NUM> parts by mass of the content of the ethylene-vinyl acetate copolymer (A), from the viewpoint of further improving low temperature heat sealability and heat seal strength.

Further, the content of the tackifier resin is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less, and still more preferably <NUM> parts by mass or less, based on <NUM> parts by mass of the content of the ethylene-vinyl acetate copolymer (A), from the viewpoint of further improving easy peelability.

An ethylene-vinyl acetate copolymer (C) according to the present invention has a viscosity of <NUM>,<NUM> mPa·s or more and <NUM>,<NUM> mPa·s or less measured at <NUM> using a Brookfield viscometer, from the viewpoint of improving the stability of adhesive strength and easy peelability.

The lower limit of the viscosity is preferably <NUM>,<NUM> mPa·s or more, more preferably <NUM>,<NUM> mPa·s or more, still more preferably <NUM>,<NUM> mPa·s or more, further preferably <NUM>,<NUM> mPa·s or more, and particularly preferably <NUM>,<NUM> mPa·s or more, from the viewpoint of further improving stability of adhesive strength, easy peelability, anti-blocking property, and processability.

The upper limit of the viscosity is preferably <NUM>,<NUM> mPa·s or less, more preferably <NUM>,<NUM> mPa·s or less, and still more preferably <NUM>,<NUM> mPa·s or less, from the viewpoint of further improving stability of the adhesive strength and easy peelability.

The ethylene-vinyl acetate copolymer (C) according to the present invention has a content of a structural unit derived from vinyl acetate of <NUM>% by mass or more and <NUM>% by mass or less, from the viewpoint of improving low temperature heat sealability and anti-blocking property.

Further, the lower limit of the content of the structural unit derived from vinyl acetate is preferably <NUM>% by mass or more, and more preferably <NUM>% by mass or more, from the viewpoint of further improving the low temperature heat sealability.

The upper limit of the content of the structural unit derived from vinyl acetate is <NUM>% by mass or less, from the viewpoint of further improving anti-blocking property and antistatic properties.

Further, the ethylene-vinyl acetate copolymer (C) according to the present embodiment preferably has a melt mass flow rate as measured at a temperature of <NUM> and a load of <NUM> in accordance with JIS K <NUM>:<NUM> of <NUM>/<NUM> or more and less than <NUM>/<NUM>, and more preferably <NUM>/<NUM> or more and less than <NUM>/<NUM>, from the viewpoint of improving anti-blocking property.

The content of the ethylene-vinyl acetate copolymer (C) is preferably <NUM> parts by mass or more, more preferably <NUM> part by mass or more, and still more preferably <NUM> parts by mass or more, based on <NUM> parts by mass of the content of the ethylene-vinyl acetate copolymer (A), from the viewpoint of further improving stability of the adhesive strength and easy peelability.

Further, the content of the ethylene-vinyl acetate copolymer (C) is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less, and still more preferably <NUM> parts by mass or less, based on <NUM> parts by mass of the content of the ethylene-vinyl acetate copolymer (A), from the viewpoint of further improving stability of the adhesive strength and easy peelability.

A method for producing the ethylene-vinyl acetate copolymer (C) according to the present embodiment is not particularly limited, and the ethylene-vinyl acetate copolymer (C) can be produced by a known method. For example, the ethylene-vinyl acetate copolymer (A) can be obtained by radical copolymerization of each polymerization component under high temperature and high pressure. Further, the ethylene-vinyl acetate copolymer (C) used may be a commercially available product.

An adhesive resin composition according to the present embodiment preferably further contains an antistatic agent (D) from the viewpoint of improving the antistatic properties of the easily peelable film to be obtained. For example, it is possible to prevent charging when the cover tape is peeled off from the carrier tape. As a result, it is possible to suppress damage to the electronic component due to static electricity and adhesion of the electronic component to the cover tape.

The content of the antistatic agent (D) is preferably <NUM> parts by mass or more, more preferably <NUM> parts by mass or more, and still more preferably <NUM> parts by mass or more, based on <NUM> parts by mass of the content of the ethylene-vinyl acetate copolymer (A), from the viewpoint of further improving antistatic properties.

Further, the content of the antistatic agent (D) is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less, and still more preferably <NUM> part by mass or less, based on <NUM> parts by mass of the content of the ethylene-vinyl acetate copolymer (A), from the viewpoint of further improving adhesive strength.

Examples of the antistatic agent include a conductive polymer, a nonionic surfactant, and an anionic surfactant.

The conductive polymer is not particularly limited, and examples thereof include polythiophene, polyaniline, polypyrrole, polyethyleneimine, and allylamine-based polymers. Polythiophene is preferable from the viewpoint of low humidity dependence of antistatic performance. Here, polythiophene refers to a polymer of unsubstituted or substituted thiophene. In particular, the substituted thiophene polymer is preferably poly(<NUM>,<NUM>-ethylenedioxythiophene).

The nonionic surfactant is not particularly limited, and examples thereof include polyalkylene glycol-based nonionic surfactants such as a higher alcohol alkylene oxide type, an alkylphenol alkylene oxide type, an alkylamide type, an alkylamine type, and a polyalkylene glycol fatty acid ester type, and polyhydric alcohols and fatty acid ester-based nonionic surfactants thereof.

The anionic surfactant is not particularly limited, and examples thereof include an aliphatic or aliphatic group-substituted aromatic sulfonate, a higher alcohol sulfate ester salt, a higher alcohol ether (alkylene oxide adduct) sulfate ester salt, a higher alcohol phosphate ester salt, and a higher alcohol ether (ethylene oxide adduct) phosphate ester salt.

Such an antistatic agent can be used alone or in combination of two or more.

The antistatic agent used may be of a liquid type or may be dissolved in a suitable solvent and coated on the surface of the heat sealable layer described later.

The adhesive resin composition according to the present embodiment may contain components other than the above as long as the effects of the present invention are not impaired. Other components are not particularly limited, and examples thereof include an anti-blocking agent, a slip agent, an antioxidant, a heat stabilizer, a light stabilizer, a pigment, and a dye. The other components may be used alone or in combination of two or more.

Examples of the anti-blocking agent include silica, aluminosilicate (zeolite, and the like).

Examples of the slip agent include various amides such as palmitamide, stearamide, behenamide, oleamide, erucamide, oleyl palmitamide, stearyl palmitamide, methylenebisstearamide, methylenebisoleamide, ethylenebisoleamid, ethylenebiserucamide; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; and hydrogenated castor oil.

The adhesive resin composition according to the present embodiment is suitably used for adhering a paper base material. That is, the adhesive resin composition according to the present embodiment is suitably used for a cover tape for closing a housing portion for housing a microchip or the like of a paper carrier tape which is a paper container for transporting an electronic component.

Examples of the paper carrier tape include a paper carrier tape in which a bottom cover tape is heat-sealed to one surface (lower surface) of a storage mount having a plurality of punched holes formed at regular intervals in the longitudinal direction and the punched holes are used as recessed portions capable of storing electronic components; and a paper carrier tape in which a plurality of recessed portions capable of storing electronic components are formed at regular intervals in the longitudinal direction of the storage mount by embossing the storage mount.

By overlapping a cover tape on the carrier tape and adhering the cover tape by heat sealing or the like, it is possible to close the recessed portions accommodating a microchip such as an IC chip and store and transport the microchip.

Further, the adhesive resin composition according to the present embodiment is also suitably used as a lid material of a packaging paper container for foods and drinks such as cup noodles, jelly, and yogurt, as well as medicines.

In the adhesive resin composition according to the present embodiment, the total content of the ethylene-vinyl acetate copolymer (A), the tackifier resin (B), the ethylene-vinyl acetate copolymer (C), and the antistatic agent (D) is preferably <NUM>% by mass or more, more preferably <NUM>% by mass or more, even more preferably <NUM>% by mass or more, and particularly preferably <NUM>% by mass or more, based on <NUM>% by mass of the entire adhesive resin composition. As a result, it is possible to further improve the performance balance between low temperature heat sealability to paper base material, adhesiveness to paper base material, easy peelability from paper base material, and anti-blocking property of the easily peelable film to be obtained.

A method for preparing the adhesive resin composition is not particularly limited, and examples thereof include a method of preparing the adhesive resin composition by dry-blending and mixing the ethylene-vinyl acetate copolymer (A), the tackifier resin (B), the ethylene-vinyl acetate copolymer (C), and optionally the antistatic agent (D) with other components; and a method of preparing the adhesive resin composition by melt-kneading the ethylene-vinyl acetate copolymer (A), the tackifier resin (B), the ethylene-vinyl acetate copolymer (C), and optionally the antistatic agent (D) with other components in an extruder.

<FIG> is a cross-sectional view schematically showing an example of a structure of an easily peelable film <NUM> to an embodiment of the present invention.

The easily peelable film <NUM> according to the present embodiment is an easily peelable film containing a base material layer <NUM>, and a heat sealable layer <NUM> provided on one surface of the base material layer <NUM>, in which the heat sealable layer <NUM> includes the adhesive resin composition according to the present embodiment.

The easily peelable film of the present embodiment is preferably used as a cover tape for a paper carrier tape, which is a paper container for transporting electronic components.

The base material layer <NUM> is a layer provided for the purpose of improving the handleability, mechanical properties, heat resistance, and other properties of the easily peelable film <NUM>.

Examples of the base material layer <NUM> include a plate-like material (sheet or film) made of paper, aluminum, polyester (for example, polyethylene terephthalate), polyethylene, polypropylene, polystyrene, polyamide, aluminum-deposited polyester, aluminum-deposited polypropylene, silica-deposited polyester, or the like. Among these, a sheet or film made of polyethylene terephthalate is preferable. The base material layer <NUM> may have not only a single layer structure but also a laminated structure of two or more layers.

The thickness of the base material layer <NUM> is, for example, <NUM> or more and <NUM> or less, and preferably <NUM> or more and <NUM> or less, from the viewpoint of mechanical strength and workability.

The surface of the base material layer <NUM> on the side to be adhered (or laminated) to the heat sealable layer <NUM> may be subjected to a physical treatment such as a corona treatment, a plasma treatment, a flame treatment, or an ozone treatment in order to increase the adhesive strength to the heat sealable layer <NUM>. Further, the base material layer <NUM> may be subjected to a known anchor coating treatment.

The heat sealable layer <NUM> is a layer for imparting heat sealability to the easily peelable film <NUM>, and is made of the adhesive resin composition according to the present embodiment.

The thickness of the heat sealable layer <NUM> is, for example, <NUM> pm or more and <NUM> pm or less, preferably <NUM> pm or more and <NUM> or less, and more preferably <NUM> or more and <NUM> or less.

The easily peelable film <NUM> according to the present embodiment may be provided with an intermediate layer such as polyethylene between the base material layer <NUM> and the heat sealable layer <NUM>. The intermediate layer is a layer provided to enhance the adhesiveness between the base material layer <NUM> and the heat sealable layer <NUM> and to enhance the processability when forming the heat sealable layer <NUM>.

A method for producing the easily peelable film <NUM> according to the present embodiment is not particularly limited, and a forming method commonly used for thermoplastic resins can be applied. For example, the production method can be carried out by a known method using a T-die extruder, a blown film machine or the like.

For example, the adhesive resin composition according to the present embodiment can be obtained by feeding the adhesive resin composition from a hopper of a T-die extruder and extruding the adhesive resin composition into a film from a tip of the T-die onto the base material layer <NUM>.

Further, in the method for producing the easily peelable film <NUM> according to the present embodiment, a method commonly used for forming a multilayer film can be applied. For example, the production method can be carried out by a known method using a multilayer T-die extruder, a multilayer blown film machine or the like.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples.

Details of the components used in the preparation of the adhesive resin composition are as follows.

EVA1: Ethylene-vinyl acetate copolymer (MFR = <NUM>/<NUM>, ethylene content = <NUM>% by mass, vinyl acetate content = <NUM>% by mass).

Tackifier resin <NUM>: Hydrogenated product of alicyclic hydrocarbon resin (manufactured by Arakawa Chemical Industries, Ltd. , Alcon P-<NUM>).

Here, the MFR (melt mass flow rate) was measured at a temperature of <NUM> and a load of <NUM> in accordance with JIS K7210: <NUM>.

Further, the viscosity of the ethylene-vinyl acetate copolymer (C) was measured at <NUM> using a Brookfield viscometer.

Antistatic agent <NUM>: Nonionic surfactant (product name: Electro Stripper TS7B, manufactured by Kao Corporation).

Each component was melt-kneaded at <NUM> in an extruder (<NUM> mmϕ, L/D = <NUM>, front tip Dulmage flight screw) at the mixing ratio shown in Table <NUM> to obtain an adhesive resin composition. The obtained adhesive resin composition was cut into pellets and used for preparing a laminated film for evaluation.

First, a biaxially stretched polyethylene terephthalate (PET) film (thickness <NUM>) was prepared. Using an extruder (<NUM> mmϕ, L/D = <NUM>), a screw (three stage type, groove depth ratio = <NUM>), and a die (<NUM> width, inner Deckel-type), a <NUM>-thick low-density polyethylene polymer layer (density: <NUM>/m<NUM>, MFR (according to JIS K7210:<NUM>, temperature: <NUM>, load: <NUM>) : <NUM>/<NUM>, melting point: <NUM>) was laminated on the PET-film via an anchor coating agent under the conditions of an air gap of <NUM>, a processing speed of <NUM>/min, and a processing temperature of <NUM>.

Next, a layer (thickness: <NUM>) made of the adhesive resin composition shown in Table <NUM> was laminated on the layer of the low-density polyethylene polymer using the extruder, screw and die under the conditions of an air gap of <NUM>, a processing speed of <NUM>/min and a processing temperature of <NUM> to prepare a laminated film for evaluation (easily peelable film).

The following evaluations were performed on the obtained laminated film for evaluation. The results obtained are shown in Table <NUM>.

The laminated film for evaluation was cut out in the MD direction (resin flow direction at the time of producing laminated film for evaluation) with a width of <NUM>. A sample was prepared by overlapping one surface of a paper base material (paper carrier tape made in Korea) cut into a <NUM> width in the same manner as the laminated film for evaluation and the surface of the laminated film for evaluation on which the layer made of the adhesive resin composition (heat sealable layer) was laminated, and heat sealing the paper base material and the laminated film for evaluation under the following conditions using a heat sealer (heat seal tester TP-<NUM>-B manufactured by Tester Sangyo Co,. The heat sealing was performed under the conditions of a heat sealing temperature of <NUM>, a heat sealing time of <NUM> seconds, a heat sealing bar width of <NUM>, and a gauge pressure of <NUM> MPa.

After the heat sealing, the laminated film was peeled off from the paper base material using a peeling tester (VG-<NUM>, manufactured by Vanguard Systems INC. ) under the conditions of a peeling angle of <NUM>° and a peeling speed of <NUM>/min, and the peeling force was measured.

The laminated film was peeled off from the paper base material and the peeling force was measured in the same manner as in (<NUM>) peeling strength except that the heat sealing temperature was changed to <NUM>.

The sample after the measurement of the peeling strength was observed with a microscope.

Using a resistivity meter (HIRESTA-UP, UR-<NUM> probe manufactured by Mitsubishi Chemical Analytech Co. ), the surface resistivity of the easily peelable film was measured under the conditions of a measurement voltage of <NUM> V, a measurement time of <NUM> seconds, <NUM>, and <NUM>% RH to evaluate the antistatic properties.

Two laminated films for evaluation were prepared in a strip shape having a <NUM> width, and the surface on the heat sealable layer side and the surface on the biaxially stretched polyester film side were overlapped with each other, and left in an oven at <NUM> for <NUM> hours while applying a load of <NUM>/cm<NUM>.

Next, the two laminated films for evaluation were peeled off using a peeling tester (VG-<NUM>, manufactured by Vanguard Systems INC. ) under the conditions of a peeling angle of <NUM>° and a peeling speed of <NUM>/min, and the peeling force was measured.

As is clear from Table <NUM>, the easily peelable films using the adhesive resin compositions of Examples <NUM> to <NUM> were excellent in performance balance between low temperature heat sealability, adhesiveness, easy peelability and anti-blocking property. On the other hand, the easily peelable films using the adhesive resin compositions of Comparative Examples <NUM> and <NUM> were inferior in performance balance between low temperature heat sealability, adhesiveness, easy peelability and anti-blocking property.

Claim 1:
An easily peelable film (<NUM>) comprising:
a base material layer (<NUM>); and
a heat sealable layer (<NUM>) provided on one surface of the base material layer (<NUM>),
wherein the heat sealable layer (<NUM>) includes an adhesive resin composition,
wherein the adhesive resin composition comprises an ethylene-vinyl acetate copolymer (A) in which a content of a structural unit derived from vinyl acetate is <NUM>% by mass or more and <NUM>% by mass or less, and a melt mass flow rate (MFR, JIS K <NUM>:<NUM>, <NUM>, <NUM> load) is <NUM>/<NUM> or more and <NUM>/<NUM> or less;
a tackifier resin (B); and
an ethylene-vinyl acetate copolymer (C) having a viscosity of <NUM>, <NUM> mPa·s or more and <NUM>, <NUM> mPa·s or less measured at <NUM> using a Brookfield viscometer,
wherein the easily peelable film (<NUM>) is a cover tape for a paper carrier tape, and
wherein the ethylene-vinyl acetate copolymer (C) has a content of a structural unit derived from vinyl acetate of <NUM>% by mass or more and <NUM>% by mass or less.