JP2010059308A - Surface-modified resin film and method for modifying surface of resin film - Google Patents

Abstract

Provided is a surface-modified resin film having high adhesive strength even when a laminated film with another resin film is produced only by thermocompression bonding without using an adhesive or an anchor coat agent.
At least one surface of a substrate is a resin film made of a thermoplastic resin having a thickness of 10 to 500 μm, which is surface-modified by an atmospheric pressure plasma apparatus, and has a depth of about 10 nm or less from the surface. A thermal adhesion modified layer is formed, and the peak area derived from the C—C bond (S ₁ : modified) found in the binding energies 11 to 17 eV of the valence band spectrum at a depth of 4 nm from the film surface by XPS observation. The post-quality peak area, S ₀ : peak area before modification, S ₁ / S ₀ : peak area ratio before and after modification, and polyethylene terephthalate (PET) is S ₁ / S ₀ <0.8, nylon ( NY) in _S 1 _{/ S} 0 <0.89, and has a _S 1 _{/ S} 0 <0.9 in linear low density polyethylene (L-LDPE).
[Selection figure] None

Description

  The present invention relates to a surface-modified resin film and a resin film surface modification method.

  In the field of packaging containers and bags (hereinafter collectively referred to as packaging containers) used for packaging foods, beverages, electronic device parts, pharmaceuticals, etc., the contents to be laminated and packaged by combining two or more types of resin films A laminated film having a necessary function is used according to the properties of the product and the method of using the packaged package. As such a laminated film, for example, after filling the contents, when the filling port of the packaging container is sealed by welding with a heating bar, so-called heat sealing, heat sealing is applied to the inner surface of the packaging container which becomes the heat sealing surface. A polyolefin resin layer such as polyethylene having excellent properties is used as the heat seal layer. The laminated film is laminated with a resin film such as polyester, nylon, or polypropylene in order to reinforce the strength or impart other functions. For this reason, a laminated film in which a polyethylene resin excellent in heat sealability and a polyester film, for example, are laminated in advance is prepared and molded into a final packaging container.

  By the way, when laminating a polyethylene resin film and another resin film, the adhesive strength is insufficient unless an adhesive layer or an anchor coat layer formed by applying an adhesive or an anchor coat agent on the surface of the resin film is used. Sometimes. However, when an anchor coat layer or an adhesive layer is used, VOC (volatile organic compound) generated by evaporating and drying the solvent during the laminating process of those resin films is a problem in that it is dissipated into the atmosphere. Yes. In addition, when an adhesive layer is used, an aging period of about several days is required after dry lamination, and there is a problem that production efficiency is low.

Furthermore, there may be a problem with the aptitude relationship between the contents and the packaging container. For example, in a medical fluid such as an infusion solution, a solvent remaining in an anchor coat layer or an adhesive layer used in a packaging container, or a low molecular component resulting from the anchor coat agent or the adhesive may cause an interaction. Also, odor may be a problem in foods and the like. As a countermeasure against environmental problems, a method capable of reducing the amount of organic solvent used is required.
For this reason, as a more preferable method for producing a laminated film for a packaging container, there is a demand for a method capable of producing a laminated film having high adhesive strength without using an anchor coat layer or an adhesive layer.

In response to such a demand, various proposals have been made regarding a method for producing a laminated film without using an anchor coat layer or an adhesive layer by performing a treatment for increasing the adhesive strength (for example, Patent Document 1). -6).
In Patent Document 1, at least one surface of a plastic substrate is oxidized by corona treatment, plasma treatment, flame plasma treatment, electron beam irradiation, ultraviolet irradiation, etc., and at least one surface of a melt-extruded film is subjected to ozone treatment. An extrusion laminating method in which both are brought into contact with each other and pressure-bonded is described.
In Patent Document 2, at least one surface of a plastic substrate is subjected to electron beam irradiation treatment, low-pressure plasma treatment, atmospheric pressure plasma treatment, or corona discharge treatment in an atmosphere of an inert gas such as argon, helium, krypton, neon, xenon, or nitrogen. And an extrusion laminating method in which at least one surface of a melt-extruded film is subjected to ozone treatment and then brought into contact with each other and pressure-bonded.

In Patent Document 3, in order to activate the surface of the synthetic resin and improve the adhesion to the printing ink and the metal vapor deposition film, a mixed gas atmosphere substantially composed of nitrogen and carbon dioxide (preferably the oxygen concentration is 0.1 vol. % Or less), a surface treatment method for a synthetic resin is described.
Patent Document 4 discloses the number of nitrogen and carbon atoms on the surface of a substrate film by ESCA method by corona discharge treatment in nitrogen gas (oxygen concentration of 3 vol% or less), carbon dioxide gas or a mixed gas atmosphere of nitrogen / carbon dioxide gas. A surface to be processed having a ratio (N / C) in the range of 0.001 to 0.1 is generated, and a water / lower alcohol mixed solution or water is used as a solvent on the surface to be processed. A method for producing a gas barrier film is described in which a coating agent containing a layered compound as a main constituent is applied and dried to form a coating film.

Patent Document 5 discloses a method of laminating at least two or more polyolefin resins such as linear low density polyethylene (L-LDPE) and unstretched polypropylene (CPP) without using an adhesive. ing. Specifically, the surface of the laminated resin is subjected to low-temperature plasma treatment using a scanning glow discharge plasma apparatus, and then laminated by thermocompression bonding.
Patent Document 6 discloses that substrates obtained by plasma-treating the surface of a fluororesin sheet with an atmospheric pressure plasma treatment apparatus do not use an adhesive and do not change the structure / composition, and have a melting point of the substrate or lower. A bonding apparatus and a bonding method for bonding by pressure bonding at a temperature are shown.
JP 7-314629 A JP-A-9-234845 Japanese Patent Publication No.57-30854 Japanese Patent Laid-Open No. 9-1111017 JP-A-3-162420 JP 2008-75030 A

  However, in the methods proposed in Patent Documents 1 and 2, the adhesive strength may be insufficient only by performing a combination of a corona treatment in a known air atmosphere and a UV / ozone treatment.

  Patent Documents 3 and 4 describe methods for improving adhesion by modifying the surface of a synthetic resin by corona discharge treatment in an atmosphere containing nitrogen and substantially no oxygen. However, these patent documents only describe the adhesion to a coating film containing printing ink, a metal vapor-deposited film, a water-soluble polymer and an inorganic layered compound as main components. In order to confirm the adhesiveness between the surface treatment surface of the synthetic resin activated by such a surface treatment method and the resin film by thermocompression bonding, the present inventor has performed a corona discharge treatment in a nitrogen gas atmosphere. On the other hand, when an attempt was made to produce a laminated film by a method of thermally laminating a resin film having an untreated surface, sufficient adhesive strength could not be obtained.

In Patent Document 5, low-temperature plasma treatment is performed on the surface of a polyolefin resin such as linear low-density polyethylene (L-LDPE), which is a nonpolar thermoplastic resin, using a scanning glow discharge plasma apparatus. Later, it is disclosed that lamination is performed by thermocompression bonding. In addition, when laminating a polar thermoplastic resin such as polyester and a nonpolar thermoplastic resin, it is processed only with the nonpolar thermoplastic resin by the modulated magnetic field plasma apparatus, but the polar thermoplastic resin. The surface is preferably used without plasma treatment because a high interlayer adhesion strength can be obtained. In this case, it can be confirmed by XPS analysis and ESCA analysis that C—O groups and C═O groups are generated when processed with a modulated magnetic field plasma apparatus, and it is assumed that these generated functional groups contribute to adhesion. Yes.
However, the analysis of the state in the depth range from the plasma-treated resin surface to about 10 nm and the definition of the general preferable surface modified layer state are not shown. In addition, according to the embodiment, for example, the thermocompression bonding temperature when PP and LDPE are thermocompression bonded is 100 ° C., but no pressurizing force is shown.

Patent Document 6 uses an atmospheric pressure plasma processing apparatus in which a lower alcohol which is a primary alcohol or a secondary alcohol having 4 or less carbon atoms is vaporized and mixed with an inert gas and supplied to an electrode. A method is disclosed in which surface modification is performed on substrates whose surfaces are made of a fluororesin, and the surface-modified substrates are thermocompression bonded at a temperature equal to or lower than the melting point of the substrates.
It is said that hydrophilicity is imparted to the fluororesin on the surface by surface modification, but the state of the depth range from the plasma-treated resin surface to about 10 nm was analyzed, and the state of a general preferable surface modified layer was defined. Things are not shown. In addition, the thermocompression bonding temperature at the time of thermocompression bonding is, for example, 200 ° C. or less for polytetrafluoroethylene (PTFE) having a melting point of 327 ° C., but no pressure is shown, so that it is intended for industrial use. I can't.

  The present invention has been made in view of the above. Even if a laminated film with another resin film is produced only by thermocompression bonding without using an adhesive or an anchor coating agent, the surface modification has high adhesive strength. It is an object of the present invention to provide a resin film and a surface modification method for the resin film.

In order to solve the above problems, the present invention is a surface modification method performed on a resin film made of a thermoplastic resin having a thickness of 10 to 500 μm, and the thermoplastic resin constituting the resin film is made of polyethylene terephthalate ( PET), nylon (NY), or linear low-density polyethylene (L-LDPE), subjected to atmospheric pressure plasma treatment under the following operating conditions (1) to (3), and the surface of the resin film A surface-modifying method for a resin film, characterized in that a heat-adhesive modified layer is formed at a depth of about 10 nm or less.
(1) The atmospheric pressure plasma treatment is a corona discharge treatment in a nitrogen gas atmosphere or an atmospheric pressure glow plasma treatment in a rare gas atmosphere such as helium or argon.
(2) The reaction gas is based on nitrogen gas or oxygen gas, and one or more of H ₂ , NH ₃ , CH ₄ , CO ₂ , and N ₂ O may be added or not added.
(3) Peak area derived from C—C bonds found in binding energy of 11 to 17 eV in the valence band spectrum at a depth of 4 nm from the film surface as observed by an X-ray photoelectron spectrometer (XPS) Is measured before and after reforming, and the ratio of the peak area before and after reforming (S ₁ / S ₀ ), which is the ratio of the peak area before reforming (S ₀ ) and the peak area after reforming (S ₁ ). ) is, _S 1 _{/ S} 0 in the polyethylene terephthalate (PET) <0.8, nylon (NY) in _S 1 _{/ S} 0 <0.89, linear low density polyethylene (L-LDPE) in _S 1 / S The irradiation time, applied power, and frequency of atmospheric pressure plasma are adjusted so as to suppress the formation of the thermal adhesion modified layer in a range where ₀ <0.9.

In order to solve the above problems, the present invention is a resin film made of a thermoplastic resin having a thickness of 10 to 500 μm, wherein at least one surface of a base material is surface-modified by an atmospheric pressure plasma apparatus, The thermoplastic resin constituting the resin film is one of polyethylene terephthalate (PET), nylon (NY), or linear low density polyethylene (L-LDPE), and has a depth of about 10 nm or less from the surface of the resin film. In addition, a heat-adhesive modified layer was formed, and as observed by an X-ray photoelectron spectrometer (XPS), the binding energy (Binding Energy) of the valence band spectrum at a depth of 4 nm from the film surface was observed as 11 to 17 eV. C-C peak areas derived from the binding _{(S 1} which is: peak area after modification, _{S 0:} before modification of the peak area, _{S 1} S _0: Peak area ratio of the modified front and rear) is, _S 1 _{/ S} 0 in the polyethylene terephthalate (PET) <0.8, Nylon (NY) in _S 1 _{/ S} 0 <0.89, linear low density polyethylene (L-LDPE) provides a surface-modified resin film characterized in that S ₁ / S ₀ <0.9.

  When the thermoplastic resin constituting the resin film is polyethylene terephthalate (PET), the surface-modified resin film of the present invention has a surface on which the heat-adhesive modified layer of the resin film is formed, and an air corona treatment Adhesive agent and anchor agent by facing the air corona-treated surface of the linear low density polyethylene (L-LDPE) resin film (unstretched linear low density polyethylene film, trade name: SK615P, manufactured by Tamapoly Co., Ltd.) Adhesive strength when heated and pressure-bonded by holding at a temperature of 160 ° C. and a pressure of 0.4 MPa for 10 seconds without applying JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 ° The strength when peeled at a speed of 5 mm / min by the measurement method specified in “peeling” is 600 gf / inch or more. Preferred.

  When the thermoplastic resin constituting the resin film is nylon (NY), the surface-modified resin film of the present invention is subjected to an air corona treatment with the surface of the resin film on which the heat adhesion modified layer is formed. A linear low density polyethylene (L-LDPE) resin film (unstretched linear low density polyethylene film manufactured by Tamapoly Co., Ltd., trade name: SK615P) facing the air corona treated surface, Adhesive strength when heated and pressure-bonded by holding at a temperature of 160 ° C. and a pressure of 0.4 MPa for 10 seconds without application is JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 degree peeling As a strength when peeled at a speed of 5 mm / min by the measurement method defined in ", it is preferably 1000 gf / inch or more.

  In the surface-modified resin film of the present invention, when the thermoplastic resin constituting the resin film is linear low density polyethylene (L-LDPE), a heat adhesion modified layer of the resin film is formed. The surface and the air corona-treated surface of an air corona-treated polyethylene terephthalate (PET) resin film (biaxially stretched polyethylene terephthalate film manufactured by Toyobo Co., Ltd., trade name: E5102) are applied to each other and an adhesive and an anchor agent are applied. The adhesive strength when heated and pressure-bonded by holding at a temperature of 160 ° C. and a pressure of 0.4 MPa for 10 seconds is JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 degree peeling” The strength when peeled at a speed of 5 mm / min by the measurement method specified in Section 6 shall be 600 gf / inch or more. It is preferred.

  According to the present invention, a laminated film having high adhesive strength can be produced even if a laminated film is produced only by thermocompression bonding without using an adhesive layer or an anchor coat layer.

  The heat-adhesive modified layer of the surface-modified resin film obtained by the present invention is formed on a functional group generated by surface modification with a conventional plasma apparatus, for example, a main chain or side chain of a polymer. The generated carbonyl group (> CO), carboxyl group (—COOH), etc. do not contribute to adhesion, but are due to low molecular decomposition products accompanying the breakage of polymer chains in an extremely shallow portion of 10 nm or less from the resin surface. The heat adhesion modified layer contributes to adhesion. Further, the adhesion mechanism of the heat-adhesive modified layer of the surface-modified resin film according to the present invention cannot be explained only by an adhesion mechanism based on hydrogen bonding or intermolecular force at the interface of the adhesive layer.

Adhesion that provides high adhesive strength between the resin layers of the laminated film when the laminated film is produced by thermocompression bonding with other, for example, a corona-treated resin film, using the surface-modified resin film obtained by the present invention Although the mechanism is not clear, for example, the following adhesion mechanism can be considered.
First, at a depth of 10 nm or less from the surface of the surface-modified resin film obtained by the present invention, the polymer main chain and side chain constituting the resin composition are cleaved, and the polymer having a relatively small molecular weight. Group (short molecule group) is formed and becomes a heat-adhesive modified layer.
This short molecule group has a low melting point compared to the resin composition inside the base film, and is assumed to be in a molten state at a temperature lower than the temperature at which the inside of the base film is melted to exhibit thermal adhesiveness. .

For this reason, for example, the surface-modified surface of a surface-modified polyethylene terephthalate (PET) resin film obtained in the present invention and a commercially available air corona-treated linear low-density polyethylene (L-LDPE) A resin film (unstretched linear low-density polyethylene film manufactured by Tamapoly Co., Ltd., trade name: SK615P) is opposed to the air corona-treated surface, and a temperature of 160 ° C. and a pressure of 0 are applied without applying an adhesive and an anchor agent. When held at 4 MPa for 10 seconds and thermocompression bonded, only the heat-adhesive modified layer on the surface-modified PET surface is melted at 160 ° C., which is the melting point of PET, which is 252 ° C. or lower. A linear low-density polyethylene (L-LDPE) resin film that has been subjected to air corona treatment in the molten state on the other side to be bonded and the molten resin are mixed together. There is then considered to be bonded solidified and lowered resin temperature.
The above description of the adhesion mechanism describes one of the possibilities of the adhesion mechanism that has occurred, and is not intended to limit the present invention by this description.

The present invention will be described below based on the best mode.
The surface-modified resin film of the present invention is a resin film made of a thermoplastic resin having a thickness of 10 to 500 μm, wherein at least one surface of a substrate is surface-modified by an atmospheric pressure plasma apparatus, The surface modified surface is observed by the following observation method of an X-ray photoelectron spectrometer (XPS), and a heat adhesion modified layer is formed at a depth of about 10 nm or less from the surface of the resin film. A surface-modified resin film characterized by

Here, the observation of the X-ray photoelectron spectrometer (XPS) measures a valence band spectrum having a depth of 4 nm from the film surface, and is found in the binding energy of the valence band spectrum (Binding Energy) 11 to 17 eV. The peak area derived from the CC bond (S ₁ : peak area after modification, S ₀ : peak area before modification, S ₁ / S ₀ : peak area ratio before and after modification) is polyethylene terephthalate (PET). ) For S ₁ / S ₀ <0.8, for nylon (NY), S ₁ / S ₀ <0.89, for linear low density polyethylene (L-LDPE), S ₁ / S ₀ <0.9. It is characterized by.

In the prior art, the method of observing the surface-modified resin film by XPS was quantification of C _1s , O _1s , N _1s, etc. of inner-shell electrons focusing on the generation of functional groups.
In the prior art, the depth from the surface of the resin film is generally observed in the vicinity of 7 to 8 nm, and detailed analysis of the depth of 5 nm or less from the surface of the resin film has not been made. The present inventors have noticed that the adhesive strength of the laminated resin film differs depending on the subtle difference in the state of the atmospheric pressure plasma treatment, and 5 nm or less from the surface of the resin film that has not been analyzed in detail in the prior art. By observing the depth state (valence band spectrum), the present invention could be achieved.

In the present invention, the peak derived from the C—C bond found in the binding energy (Binding Energy) 11 to 17 eV of the valence band spectrum at a depth of 4 nm from the film surface by observation with an X-ray photoelectron spectrometer (XPS). The surface (S ₁ : peak area after reforming, S ₀ : peak area before reforming, S ₁ / S ₀ : peak area ratio before and after reforming) is surface-modified by the atmospheric pressure plasma apparatus. What is different is shown, for example, for a polyethylene terephthalate (PET) resin film, for example.
First, FIG. 1 is a graph showing a valence band spectrum at a depth of 4 nm from the surface of an untreated polyethylene terephthalate (PET) resin film before surface modification. FIG. 2 is a graph of Example 2 showing a valence band spectrum at a depth of 4 nm from the surface of a surface-modified polyethylene terephthalate (PET) resin film according to the present invention described later.

The solid line waveform in FIG. 1 is a valence electron in which the photoelectron detection angle is set so that a depth of 4 nm can be measured from the surface of the resin film to be measured, and the electron count number measured according to the binding energy is plotted. It is a graph which shows a band spectrum. Moreover, the waveform of the broken line in FIG. 1 is an integral for obtaining the peak area derived from the C—C bond seen in the binding energy 11 to 17 eV of the valence band spectrum at a depth of 4 nm from the surface of the film. A curve is shown, and the peak area S ₀ before surface modification is obtained.
In FIG. 2, similarly, the broken line waveform indicates the peak area derived from the C—C bond found in the binding energy of 11 to 17 eV in the valence band spectrum at a depth of 4 nm from the surface of the film. and it shows the integral curve for the peak area S ₁ after the surface modification is obtained.

Here, when the peak area S ₁ after the surface modification obtained in FIG. 2 is compared with the peak area S ₀ before the surface modification obtained in FIG. 1, the peak of the waveform peak indicated by the broken line is obtained by the surface modification. It can be seen that the peak area is decreased. In this case, the peak area ratio S ₁ / S ₀ before and after the reforming is 0.69. This indicates that the total number of C—C bonds at a depth of 4 nm from the surface of the resin film is reduced by surface modification, and the binding energy of the valence band spectrum (Binding Energy) 11 The peak area ratio derived from the C—C bond seen at ˜17 eV can serve as an index for determining the quality of surface modification on the surface of the resin film in the present invention.
Here, before and after the surface modification of the polyethylene terephthalate (PET) resin film, the peak areas derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV are different. In the examples described later, nylon (NY) and linear low-density polyethylene (L-LDPE) are also derived from the C—C bond at a valence band spectrum of 11 to 17 eV. The measurement results of the peak area ratio are described.

(Thermoplastic resin film)
The thermoplastic resin film that can be used in the present invention is polyethylene terephthalate (PET), nylon (NY), or linear low density polyethylene (L-LDPE).
The melting points of these thermoplastic resins are polyethylene terephthalate (252 ° C.), nylon (220 ° C.), and linear low density polyethylene (110 to 135 ° C.), respectively.

It is necessary to perform the thermocompression bonding temperature of the laminated film at a temperature lower than the melting point of polyethylene terephthalate (PET) and nylon (NY). When thermocompression bonding is performed at a temperature higher than the melting points of polyethylene terephthalate (PET) and nylon (NY), there is a problem that the resin adheres to the heating roll and the surface of the resin becomes rough.
The thermocompression bonding temperature when thermocompression bonding of linear low density polyethylene (L-LDPE) surface-modified by air corona treatment or atmospheric pressure plasma treatment and polyethylene terephthalate (PET) subjected to atmospheric pressure plasma treatment is as follows. It is 110-180 degreeC, and it is preferable to carry out with the applied pressure of 0.1-0.5 MPa.
Thermocompression bonding temperature when thermocompression bonding of linear low density polyethylene (L-LDPE) surface-modified by air corona treatment or atmospheric pressure plasma treatment and nylon (NY) subjected to atmospheric pressure plasma treatment Is 110 to 180 ° C., and is preferably performed at a pressure of 0.1 to 0.5 MPa. Adhesive strength is improved by increasing the thermocompression bonding temperature, time and pressure. What is necessary is just to select suitably the conditions from which the target adhesive strength is obtained.

The thickness of the resin film used in the present invention is preferably about 10 to 500 μm. If the thickness is 10 μm or less, it tends to be wrinkled, and it is difficult to perform roll-to-roll processing, resulting in inconvenience in handling. On the other hand, if the thickness exceeds 500 μm, the rigidity is high and the flexibility is lost, and similarly to the case where the thickness is too thin, it is difficult to perform the roll-to-roll processing and the handling is caused unnecessarily.
Accordingly, when the surface-modified resin films according to the present invention are laminated by thermocompression bonding to produce a laminated film, the total thickness does not exceed 500 μm in order to wind up the laminated resin film as a roll. It is necessary to consider so.
In addition, when the thickness of the laminated resin film exceeds 500 μm, it is difficult to wind up the laminated resin film on a roll body. It will be produced as a sheet.

(Laminated film manufacturing method)
As a method for producing a laminated film using the present invention, when laminating a second resin film made of another thermoplastic resin on the surface of the first base resin film made of a thermoplastic resin, the following ( It can be carried out by the steps 1) to (3).
(1) A surface treatment is performed on the surface of the first base resin film by the atmospheric pressure plasma treatment according to the present invention.
(2) The surface of the second resin film is subjected to surface treatment by atmospheric pressure plasma treatment according to the present invention or by corona discharge treatment (air corona treatment) in an air atmosphere.
(3) The surface of the second resin film that has been subjected to the surface treatment is superimposed on the surface of the first base resin film that has been subjected to the surface treatment, and is laminated by thermocompression bonding.
The reaction gas for the atmospheric pressure plasma treatment is not limited to the one based on nitrogen gas, but may be based on oxygen gas.

  In the present invention, the two resin films to be laminated are films made of a thermoplastic resin. The thermoplastic resin forming these films is any one of polyethylene terephthalate (PET), nylon (NY), and linear low density polyethylene (L-LDPE).

  When the laminate is a thermal laminate, the two resin films can be laminated by heating and thermocompression bonding in a state where they are overlapped. Of the two resin films laminated by thermal lamination, one of the resin films is preferably made of polyolefin, and the other resin film is preferably made of polyester or polyamide. The surface modification treatment for the two resin films to be laminated may be performed first as long as it is a stage prior to lamination. Further, the surface modification treatment may be performed simultaneously or in parallel on the two films to be laminated. When laminating three or more thermoplastic resin films, it is possible to produce a laminated film of three or more layers by repeating the surface modification treatment and laminating process on the surface to be laminated as many times as necessary. . In addition, after surface modification treatment on both surfaces of the base resin film, by laminating and laminating two other resin films subjected to surface modification treatment on each surface of the base resin film, A three-layer laminated film in which different resin films are laminated on both sides of the base resin film can also be produced.

When the laminate is an extrusion laminate, the second resin film manufactured by the melting method is used. In the two resin films laminated by extrusion lamination, it is preferable that the first base resin film is made of polyester or polyamide, and the second resin film is made of polyolefin.
The second resin film by extrusion lamination can be produced by melting a thermoplastic resin in an extruder and extruding the molten resin from a T-die, for example, into a film shape. In the extrusion laminating method, a molten resin film in a heat-melted state extruded from a T-die comes into contact with a base resin film and is pressure-bonded between two rolls to form a laminated film.
The surface modification treatment for the base resin film is performed before the extrusion lamination. In order to perform the surface modification treatment on the second resin film produced by the T die, a treatment device such as an air corona discharge is installed below the T die, and the second resin film is brought into contact with the base resin film at the second stage. What is necessary is just to perform the process of surface modification with respect to the surface of the side which contacts the base-material resin film of a resin film.

(Corona discharge treatment)
Thermoplastic polyolefin resin films such as polyethylene and polypropylene do not have a polar group in the surface layer, and therefore have low ink printability and adhesion to other resins. For this reason, in order to improve the printability of ink and the adhesion to other resins, the surface of the resin film is modified by corona discharge treatment. In the surface modification treatment by corona discharge, corona discharge is generated in the atmosphere using a high-frequency power supply voltage, and the electrons and ions generated along with the corona discharge are irradiated to the surface of the resin film, and functional groups are formed on the surface of the resin film. The surface modification of the resin film is performed by adding.

(Corona discharge treatment in air atmosphere (air corona treatment))
In the usual surface modification treatment by corona discharge performed in an air atmosphere, the surface of the resin film subjected to the corona discharge treatment is oxidized, and on the surface of the resin film, a carbonyl group is bonded to the main chain or side chain of the polymer. It is considered that oxygen functional groups such as (> CO) and carboxyl groups (—COOH) are mainly generated.

(Corona discharge treatment in nitrogen gas atmosphere)
By performing corona discharge treatment in a nitrogen gas atmosphere, it is thought that nitrogen functional groups such as amino groups (—NH ₂ ) that are thought to contribute to adhesion are mainly generated in the main chain and side chain of the polymer film surface. It is done. Furthermore, unlike corona discharge treatment (air corona treatment) in a normal air atmosphere, corona discharge treatment in a nitrogen gas atmosphere causes discharge in a nitrogen gas atmosphere, so corona discharge treatment (air corona discharge in an air atmosphere). The generation of a fragile layer due to impurities in the air generated when the treatment is performed is suppressed. Some patent documents describe that nitrogen gas can also be used as an atmospheric gas for atmospheric pressure glow plasma treatment, but it is not atmospheric pressure glow plasma discharge when the discharge state is observed. However, corona discharge in a nitrogen gas atmosphere is capable of lightning-like streamer-like (linear) lightning, that is, a gentler (mild) glow discharge than corona discharge in an air atmosphere by adjusting discharge conditions. Therefore, it can be used for surface modification that is more uniform than air corona treatment.

(Atmospheric pressure glow plasma treatment)
Conventionally, low-temperature plasma treatment for discharging in a vacuum state has been used for surface modification. However, since vacuum equipment is required, there is a drawback that the apparatus becomes large and the operation is complicated. For this reason, an atmospheric pressure plasma treatment apparatus that generates a glow discharge state that can only be generated in a vacuum state at atmospheric pressure and performs surface modification using the reaction radicals, electrons, etc. generated by the glow discharge state is usually It has come to be used simply for improvement and adhesion improvement.

  Atmospheric pressure glow plasma treatment uses a rare gas element such as helium or argon as the atmospheric gas to maintain a stable glow discharge, which is more streamer-like (linear) like lightning, that is, more than corona discharge in an air atmosphere. Uniform surface modification without unevenness is possible. Some patent documents describe that nitrogen gas can also be used as an atmospheric gas for atmospheric pressure glow plasma treatment, but it is not atmospheric pressure glow plasma discharge when the discharge state is observed.

The atmospheric pressure plasma treatment in the present invention is a corona discharge treatment in a nitrogen gas atmosphere or an atmospheric pressure glow plasma treatment in a rare gas atmosphere such as helium or argon.
In atmospheric pressure plasma treatment using oxygen as a reactive gas, oxygen functional groups such as carbonyl groups (> CO) and carboxyl groups (—COOH) are mainly generated on the main chain and side chains of the polymer on the surface of the resin film. . Further, by using nitrogen-based gas as a reaction gas, for example, N ₂ , N ₂ O, NH _3, etc., and further mixing hydrogen (H ₂ ), oxygen (O ₂ ), etc., amino groups, amide groups, etc. The present inventors have confirmed that it can be intentionally introduced.
Further, CH ₄ , CO ₂ or the like may be added to the reaction gas.

In consideration of these, in the present invention, when the surface modification treatment is performed on the surface of the resin film using the atmospheric pressure plasma treatment, the corona discharge treatment in a nitrogen gas atmosphere or the large amount in a rare gas atmosphere such as helium or argon. Performed using atmospheric pressure glow plasma treatment.
Furthermore, in the present invention, in the atmospheric pressure plasma treatment, the plasma generated by the atmospheric pressure plasma apparatus is applied to the surface of the resin film so that the heat adhesion modified layer is formed in an extremely shallow portion of 10 nm or less from the resin surface. The irradiation time, applied power, and frequency are adjusted.
When performing the surface modification treatment, it is desirable to analyze the state in the depth range from the surface of the resin film to about 10 nm by XPS. In the valence band spectrum at a depth of 4 nm from the surface of the resin film, by measuring the peak area derived from the C—C bond found in the binding energy of 11 to 17 eV, a preferred thermal adhesion modified layer Can be observed. In addition, by confirming that the valence band spectrum at a depth of about 10 nm from the surface of the resin film has not changed, the depth of the thermal adhesion modified layer is about 10 nm or less from the surface of the resin film. It can be confirmed that the heat-adhesive modified layer is not formed deeper than about 10 nm from the surface.

  Hereinafter, the present invention will be specifically described with reference to examples.

(Measuring equipment, measuring method)
In order to confirm the effect of the present invention, the experiment conducted was performed using the following measuring equipment and measuring method.

・ Processing conditions by atmospheric pressure plasma treatment Frequency 20kHz ~ 13.56MHz
Power 10 ~ 1kW
Irradiation time 0.001-10 seconds He flow rate 0-5 slm (standard liter per minute)
N ₂ flow rate 20 sccm (standard cubic centimeter per minute) to 5 slm
Distance between electrodes 1-4mm

-X-ray photoelectron spectroscopic analyzer (XPS): model ESCA-5800ci manufactured by ULVAC-PHI

-Measurement of adhesive strength: Measured according to JIS K 6854-1 "Measurement method for adhesive peel strength test Part 1: 90 degree peel".

Example 1
The surface of the polyethylene terephthalate (PET) resin film was modified using an atmospheric pressure plasma treatment apparatus, and the surface-modified polyethylene terephthalate (PET) resin film of the present invention was produced. The processing conditions are an irradiation time of 0.05 s, an applied power of 10 W, and a frequency of 13.56 MHz.
A surface-modified surface of a polyethylene terephthalate (PET) resin film (biaxially stretched polyethylene terephthalate film manufactured by Toyobo Co., Ltd., trade name: E5102) having a thickness of 12 μm was subjected to surface modification treatment using an atmospheric pressure plasma treatment apparatus. The surface was observed with an X-ray photoelectron spectrometer (XPS), and it was confirmed that a heat-adhesive modified layer was formed at a depth of about 10 nm or less from the surface of the resin film. A quality polyethylene terephthalate (PET) resin film was obtained.

Before obtaining the peak area derived from the C—C bond seen in the binding energy of 11 to 17 eV in the valence band spectrum at a depth of 4 nm from the surface of the surface-modified polyethylene terephthalate (PET) resin film The peak area derived from the C—C bond seen in the binding energy of 11 to 17 eV in the valence band spectrum at a depth of 4 nm from the surface of the untreated polyethylene terephthalate (PET) resin film before the surface modification Ask for.
FIG. 1 shows the valence band spectrum of an untreated polyethylene terephthalate (PET) resin film before surface modification. In FIG. 1, the solid line waveform is 4 nm from the surface of the resin film to be measured. It is a graph which shows the valence band spectrum which set the detection angle of the photoelectron so that depth could be measured, and plotted the electron count number measured according to the binding energy. Moreover, the broken line waveform in FIG. 1 is an integral curve for obtaining the peak area derived from the C—C bond seen in the binding energy 11 to 17 eV of the valence band spectrum at a depth of 4 nm from the film surface. And the peak area S ₀ before surface modification is obtained.
Next, regarding the surface-modified polyethylene terephthalate (PET) resin film of Example 1, CC bonds found in binding energies (Binding Energy) of 11 to 17 eV at a depth of 4 nm from the film surface. As a result of measuring the peak area S ₁ derived from the above, the peak area ratio before and after the modification was S ₁ / S ₀ = 0.74 after the modification.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)

  Next, the surface of the resin film of Example 1 on which the heat adhesion modified layer was formed, and a commercially available air corona-treated linear low density polyethylene (L-LDPE) resin film (manufactured by Tamapoly Co., Ltd.) Hold the air-corona-treated surface of the stretched linear low-density polyethylene film (trade name: SK615P) for 10 seconds at a temperature of 160 ° C. and a pressure of 0.4 MPa without applying an adhesive and an anchor agent. The adhesive strength at the time of thermocompression bonding is the strength when peeled at a speed of 5 mm / min by the measurement method specified in JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 degree peeling”. It was measured. The measurement result of the peel strength of the laminated film was 810 gf / inch.

(Example 2)
The surface-modified polyethylene terephthalate (PET) resin film of Example 2 was subjected to the same operation as in Example 1 except that the atmospheric pressure plasma irradiation time, applied power, and frequency were changed in the atmospheric pressure plasma processing apparatus. Got. The processing conditions are an irradiation time of 0.02 s, an applied power of 20 W, and a frequency of 13.56 MHz.
The peak area (S ₁ / S ₀ : peak area ratio before and after modification) derived from the C—C bond seen in the binding energy of the valence band spectrum at a depth of 4 nm from the film surface (Binding Energy) 11 to 17 eV is After modification, S ₁ / S ₀ was 0.69.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)
FIG. 1 shows a valence band spectrum having a depth of 4 nm from the untreated PET film surface. In FIG. 1, the broken line waveform shows an integral curve for obtaining the peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. reforming before the peak area S ₀ is obtained.
FIG. 2 shows a valence band spectrum having a depth of 4 nm from the surface of the PET film of Example 2. The broken line waveform in FIG. 2 shows an integral curve for determining the peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. peak area S ₁ after the modification is obtained.

  Next, using the resin film obtained in Example 2, adhesive strength with a commercially available air corona-treated linear low density polyethylene (L-LDPE) resin film under the same conditions as in Example 1 was obtained. It was measured. The measurement result of the peel strength of the laminated film was 840 gf / inch.

(Comparative Example 1)
The surface-modified polyethylene terephthalate (PET) of Comparative Example 1 was subjected to the same operation as in Example 1 except that the atmospheric pressure plasma irradiation time, applied power, and frequency were changed in a weak direction in the atmospheric pressure plasma processing apparatus. ) A resin film was obtained. The processing conditions are an irradiation time of 0.01 s, an applied power of 10 W, and a frequency of 13.56 MHz.
The peak area (S ₁ / S ₀ : peak area ratio before and after modification) derived from the C—C bond seen in the binding energy of the valence band spectrum at a depth of 4 nm from the film surface (Binding Energy) 11 to 17 eV is After modification, S ₁ / S ₀ was 0.80.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)
FIG. 3 shows a valence band spectrum having a depth of 4 nm from the surface of the PET film of Comparative Example 1. In FIG. 3, the broken line waveform shows an integral curve for obtaining a peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. peak area S ₁ after the modification is obtained.

  Next, using the resin film obtained in Comparative Example 1, adhesive strength with a commercially available air corona-treated linear low density polyethylene (L-LDPE) resin film under the same conditions as in Example 1 was obtained. It was measured. The measurement result of the peel strength of the laminated film was 400 gf / inch.

(Comparative Example 2)
As the surface-modified polyethylene terephthalate (PET) resin film of Comparative Example 2, a commercially available air corona-treated PET that was commercially available in a state where it was previously treated with an air corona was used.
The peak area (S ₁ / S ₀ : peak area ratio before and after modification) derived from the C—C bond seen in the binding energy of the valence band spectrum at a depth of 4 nm from the film surface (Binding Energy) 11 to 17 eV is After modification, S ₁ / S ₀ was 0.82.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)

  Next, the adhesive force with a commercially available air corona-treated linear low density polyethylene (L-LDPE) resin film was measured using the resin film of Comparative Example 2 under the same conditions as in Example 1. . The measurement result of the peel strength of the laminated film was 250 gf / inch.

(Example 3)
The surface of the nylon (NY) resin film was modified using an atmospheric pressure plasma treatment apparatus, and the surface-modified nylon (NY) resin film of the present invention was produced. The processing conditions are an irradiation time of 0.12 s, an applied power of 1.0 kW, and a frequency of 20 kHz.
A surface-modified surface of a nylon (NY) resin film having a thickness of 15 μm (biaxially stretched nylon film manufactured by Kojin Co., Ltd., trade name: Bonil RX) subjected to a surface modification treatment using an atmospheric pressure plasma treatment apparatus. Was observed with an X-ray photoelectron spectrometer (XPS), and it was confirmed that a heat-adhesive modified layer was formed at a depth of about 10 nm or less from the surface of the resin film. A nylon (NY) resin film was obtained.
The peak area (S ₁ / S ₀ : peak area ratio before and after modification) derived from the C—C bond seen in the binding energy of the valence band spectrum at a depth of 4 nm from the film surface (Binding Energy) 11 to 17 eV is After modification, S ₁ / S ₀ was 0.86.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)
FIG. 4 shows a valence band spectrum having a depth of 4 nm from the surface of the NY film of Example 3. The broken line waveform in FIG. 4 shows an integral curve for obtaining the peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. peak area S ₁ after the modification is obtained.

  Next, the surface of the resin film of Example 3 on which the heat adhesion modified layer was formed, and a commercially available air corona-treated linear low density polyethylene (L-LDPE) resin film (manufactured by Tamapoly Co., Ltd.) Hold the air-corona-treated surface of the stretched linear low-density polyethylene film (trade name: SK615P) for 10 seconds at a temperature of 160 ° C. and a pressure of 0.4 MPa without applying an adhesive and an anchor agent. The adhesive strength at the time of thermocompression bonding is the strength when peeled at a speed of 5 mm / min by the measurement method specified in JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 degree peeling”. It was measured. The measurement result of the peel strength of the laminated film was 2300 gf / inch.

(Comparative Example 3)
As the surface-modified nylon (NY) resin film of Comparative Example 3, commercially available air corona-treated NY, which was commercially available after being subjected to air corona treatment, was used.
The peak area (S ₁ / S ₀ : peak area ratio before and after modification) derived from the C—C bond seen in the binding energy of the valence band spectrum at a depth of 4 nm from the film surface (Binding Energy) 11 to 17 eV is After modification, S ₁ / S ₀ was 0.89.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)
FIG. 5 shows a valence band spectrum having a depth of 4 nm from the surface of the NY film of Comparative Example 3. The broken line waveform in FIG. 5 shows an integral curve for obtaining the peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. peak area S ₁ after the modification is obtained.

  Next, the adhesive force with a commercially available air corona-treated linear low density polyethylene (L-LDPE) resin film was measured using the resin film of Comparative Example 3 under the same conditions as in Example 3. . The measurement result of the peel strength of the laminated film was 500 gf / inch.

Example 4
The surface of the linear low density polyethylene (L-LDPE) resin film is modified using an atmospheric pressure plasma treatment apparatus, and the surface modified linear low density polyethylene (L-LDPE) resin film of the present invention is obtained. Produced. The processing conditions are an irradiation time of 0.05 s, an applied power of 10 W, and a frequency of 13.56 MHz.
Surface modification treatment of 100 μm thick linear low density polyethylene (L-LDPE) resin film (unstretched linear low density polyethylene film, trade name: SK615P, manufactured by Tamapoly Co., Ltd.) using an atmospheric pressure plasma treatment apparatus The surface modified surface is observed with an X-ray photoelectron spectrometer (XPS), and a heat adhesion modified layer is formed to a depth of about 10 nm or less from the surface of the resin film. After confirmation, the surface-modified linear low density polyethylene (L-LDPE) resin film of Example 4 was obtained.
The peak area (S ₁ / S ₀ : peak area ratio before and after modification) derived from the C—C bond seen in the binding energy of the valence band spectrum at a depth of 4 nm from the film surface (Binding Energy) 11 to 17 eV is After modification, S ₁ / S ₀ was 0.84.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)
FIG. 6 shows a valence band spectrum having a depth of 4 nm from the film surface of untreated L-LDPE. The broken line waveform in FIG. 6 shows an integral curve for obtaining the peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. reforming before the peak area S ₀ is obtained.
FIG. 7 shows a valence band spectrum having a depth of 4 nm from the film surface of the L-LDPE of Example 4. In FIG. 7, the broken line waveform shows an integral curve for obtaining the peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. peak area S ₁ after the modification is obtained.

  Next, the surface of the resin film of Example 4 on which the heat adhesion modified layer was formed, and a commercially available air corona-treated polyethylene terephthalate (PET) resin film (biaxially stretched polyethylene terephthalate film manufactured by Toyobo Co., Ltd.) The adhesive strength when thermocompression bonding was carried out by holding the product for 10 seconds at a temperature of 160 ° C. and a pressure of 0.4 MPa without applying an adhesive and an anchoring agent with the air corona treated surface of the product name; E5102) facing each other. , Measured by the strength when peeled at a speed of 5 mm / min by the measurement method defined in JIS K 6854-1, “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 ° Peeling”. The measurement result of the peel strength of the laminated film was 820 gf / inch.

(Comparative Example 4)
The same operation as in Example 4 was performed except that the atmospheric pressure plasma irradiation time, applied power, and frequency in the atmospheric pressure plasma processing apparatus were changed in a weak direction. A density polyethylene (L-LDPE) resin film was obtained. The processing conditions are an irradiation time of 0.005 s, an applied power of 20 W, and a frequency of 13.56 MHz.
The peak area (S ₁ / S ₀ : peak area ratio before and after modification) derived from the C—C bond seen in the binding energy of the valence band spectrum at a depth of 4 nm from the film surface (Binding Energy) 11 to 17 eV is After modification, S ₁ / S ₀ was 0.92.
(S ₁ : Peak area after modification, S ₀ : Peak area before modification)
In addition, the valence band spectrum of the depth of 4 nm from the film surface of the L-LDPE of the comparative example 4 is shown in FIG. In FIG. 8, the broken line waveform shows an integral curve for obtaining the peak area derived from the C—C bond when the binding energy of the valence band spectrum at a depth of 4 nm from the film surface is 11 to 17 eV. peak area S ₁ after the modification is obtained.

  Next, using the resin film obtained in Comparative Example 4, adhesive strength with a commercially available air corona-treated linear low density polyethylene (L-LDPE) resin film under the same conditions as in Example 4 was obtained. It was measured. The measurement result of the peel strength of the laminated film was 250 gf / inch.

  The measurement results for Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1.

(Resin film lamination test 1)
The surface-modified resin films according to the present invention were laminated only by thermocompression bonding without using an adhesive or an anchor coating agent to produce a laminated film.
As the resin film, the surface-modified polyethylene terephthalate (PET) of Example 1 and the surface-modified linear low density polyethylene (L-LDPE) of Example 4 were used.
The surface of the surface modified polyethylene terephthalate (PET) resin film of Example 1 on which the heat adhesion modified layer was formed, and the surface modified linear low density polyethylene (L-LDPE) of Example 4 When the surface of the resin film on which the heat-adhesive property-modified layer is formed is opposed to the surface, and without being applied with an adhesive and an anchor agent, it is held at a temperature of 160 ° C. and a pressure of 0.4 MPa for 10 seconds and thermocompression bonded. Was measured by the strength when peeled at a speed of 5 mm / min by the measurement method defined in JIS K 6854-1, “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 ° Peeling”. The measurement result of the peel strength of the laminated film was 650 gf / inch.

(Resin film lamination test 2)
The surface-modified resin films according to the present invention were laminated only by thermocompression bonding without using an adhesive or an anchor coating agent to produce a laminated film.
As the resin film, the surface-modified nylon (NY) of Example 3 and the surface-modified linear low density polyethylene (L-LDPE) of Example 4 were used.
The surface of the surface modified nylon (NY) resin film of Example 3 on which the heat adhesion modified layer was formed, and the surface modified linear low density polyethylene (L-LDPE) resin of Example 4 When the surface of the film on which the heat-adhesive property-modified layer is formed is opposed to the film, without applying an adhesive and an anchor agent, the film is held at a temperature of 160 ° C. and a pressure of 0.4 MPa for 10 seconds and thermocompression bonded. The adhesive strength was measured by the strength when peeled at a speed of 5 mm / min by the measurement method defined in JIS K 6854-1 “Adhesive peel adhesion strength test method Part 1: 90 degree peel”. The measurement result of the peel strength of the laminated film was 2400 gf / inch.

  The obtained results are shown in Table 2.

INDUSTRIAL APPLICABILITY The present invention can be used as a surface-modified resin film suitable for manufacturing a packaging container used for packaging foods, beverages, electronic device parts, pharmaceuticals, and the like, and a method for surface modification of a resin film. it can.
In addition, if the surface-modified resin film according to the present invention is used, a laminated film and a packaging container for producing a packaging container are produced without using an adhesive or an anchor coating agent, that is, without using any organic solvent. It becomes possible to do.
By using the present invention, it is possible to reduce the amount of the organic solvent used in the manufacturing process of the packaging container, which is effective as an environmental measure.

It is a graph which shows the valence band spectrum of the depth of 4 nm from the film surface of un-processed PET. It is a graph which shows the valence band spectrum of the depth of 4 nm from the film surface of PET of Example 2. FIG. It is a graph which shows the valence band spectrum of the depth of 4 nm from the film surface of PET of the comparative example 1. 4 is a graph showing a valence band spectrum having a depth of 4 nm from the surface of the NY film of Example 3. FIG. It is a graph which shows the valence band spectrum of the depth of 4 nm from the NY film surface of the comparative example 3. It is a graph which shows the valence band spectrum of a depth of 4 nm from the film surface of untreated L-LDPE. It is a graph which shows the valence band spectrum of the depth of 4 nm from the film surface of L-LDPE of Example 4. FIG. It is a graph which shows the valence band spectrum of the depth of 4 nm from the film surface of L-LDPE of the comparative example 4.

Claims (5)

A surface modification method performed on a resin film made of a thermoplastic resin having a thickness of 10 to 500 μm, wherein the thermoplastic resin constituting the resin film is polyethylene terephthalate (PET), nylon (NY) or linear It is one of low density polyethylene (L-LDPE), is subjected to atmospheric pressure plasma treatment under the following operating conditions (1) to (3), and is thermally bonded to a depth of about 10 nm or less from the surface of the resin film. A method for modifying a surface of a resin film, comprising forming a modified layer.
(1) The atmospheric pressure plasma treatment is a corona discharge treatment in a nitrogen gas atmosphere or an atmospheric pressure glow plasma treatment in a rare gas atmosphere such as helium or argon.
(2) The reaction gas is based on nitrogen gas or oxygen gas, and one or more of H ₂ , NH ₃ , CH ₄ , CO ₂ , and N ₂ O may be added or not added.
(3) Peak area derived from C—C bonds found in binding energy of 11 to 17 eV in the valence band spectrum at a depth of 4 nm from the film surface as observed by an X-ray photoelectron spectrometer (XPS) Is measured before and after reforming, and the ratio of the peak area before and after reforming (S ₁ / S ₀ ), which is the ratio of the peak area before reforming (S ₀ ) and the peak area after reforming (S ₁ ). ) is, _S 1 _{/ S} 0 in the polyethylene terephthalate (PET) <0.8, nylon (NY) in _S 1 _{/ S} 0 <0.89, linear low density polyethylene (L-LDPE) in _S 1 / S The irradiation time, applied power, and frequency of atmospheric pressure plasma are adjusted so as to suppress the formation of the thermal adhesion modified layer in a range where ₀ <0.9. A resin film made of a thermoplastic resin having a thickness of 10 to 500 μm, wherein at least one surface of the substrate is surface-modified by an atmospheric pressure plasma apparatus, and the thermoplastic resin constituting the resin film is polyethylene terephthalate (PET), nylon (NY) or linear low-density polyethylene (L-LDPE), a thermal adhesive modified layer is formed at a depth of about 10 nm or less from the surface of the resin film, By observation with an X-ray photoelectron spectrometer (XPS), a peak area derived from a C—C bond (S ₁ ) found in binding energies 11 to 17 eV of a valence band spectrum at a depth of 4 nm from the film surface. : peak area after modification, _{S 0:} before modification of the peak _area, S 1 / _{S 0:} reforming around the peak area ratio), Po Ethylene terephthalate (PET) in _S 1 _{/ S} 0 <0.8, Nylon in _{(NY) S 1 / S 0} <0.89, the linear low density polyethylene _{(L-LDPE) S 1 /} S 0 <0 A surface-modified resin film characterized in that it is .9.   3. The resin film according to claim 2, wherein the thermoplastic resin constituting the resin film is polyethylene terephthalate (PET), the surface of the resin film on which the heat-adhesive modified layer is formed, and an air corona treatment. A linear low density polyethylene (L-LDPE) resin film (unstretched linear low density polyethylene film manufactured by Tamapoly Co., Ltd., trade name: SK615P) facing the air corona treated surface, Adhesive strength when heated and pressure-bonded by holding at a temperature of 160 ° C. and a pressure of 0.4 MPa for 10 seconds without application is JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 degree peeling The strength when it is peeled off at a speed of 5 mm / min by the measurement method specified in “4” is 600 gf / inch or more. A surface modified polyethylene terephthalate (PET) resin film.   3. The resin film according to claim 2, wherein the thermoplastic resin constituting the resin film is nylon (NY), and the surface of the resin film on which the heat adhesion modified layer is formed is subjected to an air corona treatment. Apply an adhesive and an anchoring agent so that the air corona-treated surface of a linear low density polyethylene (L-LDPE) resin film (unstretched linear low density polyethylene film, trade name: SK615P, manufactured by Tamapoly Co., Ltd.) is opposed. The adhesive strength when heated and pressure-bonded by holding at a temperature of 160 ° C. and a pressure of 0.4 MPa for 10 seconds is JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 degree peeling” The surface modification is characterized by having a strength of 1000 gf / inch or more as a strength when peeled at a speed of 5 mm / min by the measurement method defined in 1. Nylon (NY) resin film was.   It is the resin film of Claim 2, Comprising: The thermoplastic resin which comprises the said resin film is a linear low density polyethylene (L-LDPE), The thermal-adhesion property modification layer of the said resin film was formed. The surface and an air corona-treated surface of a polyethylene terephthalate (PET) resin film (Toyobo Co., Ltd., biaxially stretched polyethylene terephthalate film, trade name: E5102) treated with an air corona are opposed to each other, and an adhesive and an anchor agent are applied. Without any change, the adhesive strength when heated and pressure-bonded for 10 seconds at a temperature of 160 ° C. and a pressure of 0.4 MPa is JIS K 6854-1 “Adhesive Peeling Adhesive Strength Test Method Part 1: 90 degree peeling” The strength when peeled at a speed of 5 mm / min with the specified measurement method is 600 gf / inch or more. Surface-modified linear low density polyethylene and symptoms (L-LDPE) resin film.

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