JP2001316489A - Polyolefin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin film which has a smooth surface and is used for producing a gas-barrier film having a low gas permeability and an enhanced capability for storing food, medicines, electronic parts, mechanical parts, a metal powder, etc. SOLUTION: At least one surface of the polyolefin film is so smooth that the average surface roughness SRa measured about an area of at least 200 μm×200 μm is 20 nm or lower. Preferably, the number of projections having heights of 100 nm or higher and/or the number of pits having depths of 100 nm or deeper on the film surface is 2/0.1 mm2 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-based film used as a base material of a gas barrier film used for food packaging, pharmaceutical packaging, electronic component packaging, protective film, mechanical component packaging, metal powder packaging and the like.

[0002]

BACKGROUND OF THE INVENTION Hitherto, polyolefin-based films have been widely used for packaging because of their excellent film-forming properties, transparency, moldability and moisture-proof properties. Among them, polyolefin-based unstretched films are excellent in heat sealability, so they are laminated with a heat-resistant base material such as a biaxially oriented polypropylene film or a biaxially oriented polyethylene terephthalate film and used as a heat seal layer of a packaging material. I have.

In order to improve the gas barrier properties of such packaging materials, vinylidene chloride (P) is coated on the surface of a heat-resistant substrate.
Attempts have been made to form a (VDC) coat layer or a deposited layer of silicon oxide, aluminum oxide, aluminum (Al), or the like. More specifically, PVD is applied to the surface of the heat-resistant substrate.
A film in which a layer C is provided, a film in which a vapor-deposited layer, an adhesive layer, and a polyolefin film are laminated on the surface of a heat-resistant substrate, a film in which a printed layer, an adhesive layer, and PVDC are laminated on the surface of a heat-resistant substrate, and one of the heat-resistant substrates. A film in which an aluminum vapor-deposited layer is formed on one surface and an adhesive layer / polyolefin-based film is laminated on the other surface is known.

[0004] However, PVDC is harmful to the environment due to the generation of chlorine-based gas during incineration of waste. Further, in the heat-resistant base material provided with the aluminum vapor-deposited layer, there is a problem that the configuration becomes complicated and the cost increases because the print layer is provided on the vapor-deposited layer.

Therefore, in order to simplify the structure of the film and reduce the cost, silicon oxide, aluminum and aluminum oxide are directly deposited on the polyolefin film without using a heat-resistant base material. It has been tried to form a gas barrier film by forming a vapor-deposited layer. However, many polyolefin films have low Young's modulus and are easily stretched, and many have poor thermal dimensional stability.Therefore, when laminating, cracks may be formed in the deposited layer, During the bag making process, there is a problem that fine cracks occur in the vapor-deposited layer of the heat-sealed portion, and the appearance and gas barrier properties are deteriorated.

For the purpose of remedying such a problem, Japanese Patent Publication No. 5-55299 and Japanese Patent Publication No. 8-18404 disclose a method of using a laminated film composed of two types of polypropylene layers having different melting points to form a film. There has been proposed a gas barrier film in which dimensional stability is improved and an aluminum vapor-deposited layer is formed on a polypropylene layer having a higher melting point, thereby suppressing the occurrence of cracks in the vapor-deposited layer during heat sealing.

Japanese Patent Application Laid-Open No. Hei 10-237188 proposes a gas barrier film using a non-stretched polypropylene film having improved surface properties and small dimensional change. Specifically, Japanese Patent Application Laid-Open No. Hei 10-23718
No. 8 discloses that the absolute value of the dimensional change in the longitudinal direction after heating at 120 ° C. for 15 minutes is 2% or less, and the number of protrusions having a height of 100 nm or more is 10% when the surface is observed with an atomic force microscope.
A gas barrier film in which an inorganic thin film is formed on the surface of a non-stretched film using a polyolefin-based unstretched film having a particle size of 250 μm ² or less has been proposed.

Japanese Patent Application Laid-Open No. H11-140199 proposes a gas barrier film using an unstretched polyolefin film having a small amount of additives, a small amount of volatile components generated during heating, and a small dimensional change. .
JP-A-11-140199 exemplifies a polyolefin-based unstretched film in which two high-melting-point polyolefin-based resin layers and two low-melting-point polyolefin-based resin layers are laminated.

However, the gas barrier films described in these publications do not always have sufficient gas barrier properties. It has also been proposed to provide a carbon-based deposition film instead of a conventionally formed metal deposition film or metal oxide deposition film.

For example, Japanese Patent Application Laid-Open No. 9-272567 proposes a gas barrier film in which a hard carbon coating film is formed on the surface of a polyethylene film or a polypropylene film. In addition, the applicant has
JP-A-10-249986 and JP-A-11-0
Japanese Patent No. 70152 proposes a film having improved gas barrier properties by forming a diamond-like carbon film having a hydrogen concentration of 50 atomic% or less and an oxygen concentration of 2 to 20 atomic% on the surface of a plastic film. are doing.

However, even with these gas barrier films, the gas barrier properties have not always been satisfactory. Furthermore, in order to improve the adhesion between the polypropylene film and the vapor-deposited thin film, a gas barrier film (see JP-A-10-235777) in which an anchor coating agent such as a ester resin or a urethane resin is anchor-coated on the polypropylene film surface is used.
A gas barrier film in which A resin or the like is provided as a protective layer of an inorganic oxide thin film (see Japanese Patent Application Laid-Open No. 10-329286) has also been proposed, but the production cost is high and the properties of the obtained film are also high. It was not always satisfactory.

Under these circumstances, the present inventors have conducted intensive studies on a gas barrier film having excellent characteristics. As a result, if the surface of the film on which the inorganic compound thin film is formed is made as smooth as possible, the gas barrier film can be obtained. It has been found that a film having excellent barrier properties can be obtained. In the case of a film having a low surface smoothness, when a gas barrier film is formed, for example, if there is a projection, a projection forms a shadow, so that a defect such as a pinhole occurs. Cannot form a gas barrier film, so that a defect such as a pinhole may also occur, and the gas barrier property may be reduced.

Further, as a result of further study, 200
By using a polyolefin-based film having a smooth surface having an average surface roughness SRa of 20 nm or less measured for an area of at least 200 μm × 200 μm, if an inorganic compound thin film is formed on the surface of the polyolefin-based film, extremely gas barrier properties can be obtained. The present inventors have found that a film having a high particle size can be obtained, and have completed the present invention.

As a polyester-based gas barrier film, a gas barrier film having a vapor-deposited layer made of an inorganic compound such as aluminum oxide on the surface of a film having a specific surface smoothness has been proposed. For example, Japanese Patent Application Laid-Open No. H11-320794 discloses that the center plane average roughness (SRa) is in the range of 0.1 nm ≦ SRa ≦ 80 nm, and the number of peaks (SPc) on the film surface is 2 / 0.1 mm.
² ≦ SPc ≦ 150 pieces / 0.1mm ² , SRa
A gas barrier film is described in which a vapor deposited layer is provided on the surface of a biaxially oriented polyester film satisfying /SPc≧0.23 nm / piece. However, a polyester film as disclosed in JP-A-11-320794 does not always have good heat sealing properties,
For use as a packaging material, it may be necessary to laminate a heat seal layer. In some cases, lamination is performed for the purpose of protecting the inorganic compound layer. The polyester-based film and the inorganic compound layer formed on the surface have a poor heat-adhesive property to the heat-sealing layer, and thus have a disadvantage that they are easily peeled off by a method such as melt extrusion lamination. For this reason, dry lamination using a solution or the like in which an isocyanate-based, polyester-based, polyamide-based, or polyimide-based adhesive is dispersed in an organic solvent such as ethyl acetate is mainly performed. However, in the technique described above, the organic solvent remains in the film and migrates to the liquid content during use or storage. Therefore, it cannot be used in a packaging form such as an infusion bag for storing a drug solution to be directly administered to a human body. In food packaging, the taste of the contents may be impaired.
In addition, since the polyester-based film is generally hard, pinholes such as vibration during transportation are easily generated, and the holding stability of the contents is not sufficient.

[0015]

An object of the present invention is to provide a polyolefin-based film having a low gas permeability and having a smooth surface which is used for producing a gas barrier film having improved preservability of foods, pharmaceuticals, electronic parts, mechanical parts, metal powders and the like. It is intended to provide.

[0016]

SUMMARY OF THE INVENTION A polyolefin film according to the present invention has a smooth surface having an average surface roughness SRa of 20 nm or less measured on an area of 200 μm × 200 μm or more.
It is characterized by having it on one side or both sides.

The projections and / or 100 nm or more present on the surface of such a polyolefin film.
It is preferable that the number of depressions having a depth of at least nm is less than 2 / 0.1 mm ² .

The polyolefin-based film is not necessarily required to be transparent. However, when the film is used for protecting a container, a liquid crystal display, a solar cell, or the like for which the quantity and color of the contents are to be confirmed, such as an infusion bag, the transparent film is used. It is preferable that the film is a transparent film. Here, the transparent film preferably has a light transmittance of 80% or more, and more preferably 90% or more. By using such a transparent film as the base film, a gas barrier film having a light transmittance of 80% or more after forming the gas barrier film can be provided.

As the polyolefin film, a polyethylene film, a polypropylene film or a cyclic olefin copolymer film is preferred. In addition, a film having a multilayer structure in which two or more types of polyolefin-based films are laminated is also preferably used.

The total amount of additives contained in the polyolefin film is preferably 0.5% by weight or less. The amount of the antiblocking agent contained in the polyolefin film is preferably 0.01% by weight or less.

The above-mentioned polyolefin film is
The polyolefin constituting the film was melted and molded into a sheet, which was immediately wrapped around a metal roll and quenched, and the molding conditions were:
The molding temperature is Tb (° C), and the temperature of the metal roll surface is Tr
When (° C.), Tb and Tr preferably satisfy the following relational expression.

Tr ≦ Tb−150 [° C.] The polyolefin-based film according to the present invention has a temperature of 120 ° C.
The dimensional change when heated under the condition of 15 minutes is preferably 4% or less, particularly preferably 2% or less.

In the polyolefin film according to the present invention, the amount of volatile components generated when heated at 130 ° C. for 5 minutes is preferably 300 μg / g or less.

[0024]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the polyolefin film according to the present invention will be specifically described. The polyolefin-based film according to the present invention is 200 μm × 200 μm
The average surface roughness SRa measured for the above area is 20 n
It has a smooth surface of not more than m on one or both sides.

The numerical value of the average roughness varies depending on the measuring method and range. If the measurement area is small, a small number of protrusions will not be measured, and the roughness may be underestimated. Also, even when measuring roughness in a linear range of a certain length, such as the center line average roughness, if the protrusion is measured, the roughness will be largely estimated, but if not, it will still be Roughness is underestimated. Further, the amount such as the maximum height difference is not preferable because the roughness is overestimated when measured over a large area.
Therefore, it is preferable to use the average surface roughness measured in a certain area or more. The average surface roughness is JIS B0
The center line average roughness Ra defined by 601 is extended so as to be applicable to the measurement surface. That is, SRa
Can be expressed as “a value obtained by averaging the absolute values of the deviations from the reference plane to the designated plane”, and is given by the following equation.

SRa = (1 / S ₀ ) ∫∫ | F (X, Y)
−Z ₀ | dXdY (where S ₀ represents the measured area, and F (X, Y) is:
The height of the measurement plane at the position (X, Y) is shown, and Z ₀ is the height of the reference plane.

In the polyolefin-based film of the present invention, the average surface roughness measured in a range of at least 200 μm × 200 μm is preferably 20 nm or less, more preferably 15 nm or less, and particularly preferably 1 nm or less.
It is desirable to use a polymer film having a thickness of 0 nm or less. In addition, such a surface roughness is usually measured using a stylus type microscope.

In the polyolefin film according to the present invention, the number of protrusions having a height of 100 nm or more and / or depressions having a depth of 100 nm or more on the surface is 2 /
It is preferably less than 0.1 mm ² (when both protrusions and depressions are present, it refers to the total number). The protrusion on the surface has a gradient of 0.01 or more (height of the protrusion / horizontal distance from the base of the protrusion to the peak). The surface depression has a gradient of 0.01 or more (depth of the depression / horizontal distance from the base of the depression to the deepest part). Such protrusions and depressions may cause deterioration of the gas barrier properties of the gas barrier film.

The measurement of the number of protrusions and / or depressions is usually performed by an atomic force microscope (AFM). The surface of the polyolefin-based film having the above characteristics is extremely smooth. In the polyolefin-based film according to the present invention, such a smooth surface may be formed on one side, or may be formed on both sides. When the polyolefin-based film according to the present invention is used as a gas barrier film, the smooth surface is desirably formed on the surface on which the gas barrier layer (inorganic compound layer) is formed.

Such a polyolefin film is
It is not necessary to be transparent, but when it is used for protection of a packaging container, a liquid crystal display, a solar cell, or the like, such as an infusion bag or the like, whose contents are desired to be confirmed, a transparent film is preferable. Here, the transparent film preferably has a light transmittance of 80% or more, and more preferably 90% or more. By using such a transparent film as the base film, a gas barrier film having a light transmittance of 80% or more after forming the gas barrier film can be provided.

Examples of the polyolefin-based film include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, poly-3-
Ethyl-1-pentene, poly 4-methyl-1-pentene, poly 4-
Methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1
-Hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-
A polymer composed of a polymer of α-olefin such as eicosene is used. Particularly, in the present invention, a polyethylene film or a polypropylene film is preferable.

As the polyolefin-based film according to the present invention, a cyclic olefin (co) polymer film is also suitable. Examples of the cyclic olefin include cyclopentene, cycloheptene, norbornene, 5-methyl-2-norbornene, tetracyclododecene, vinylcyclohexane, and the like. Even if the cyclic olefin-based (co) polymer is a homopolymer of these cyclic olefins,
It may be a copolymer with the above-mentioned α-olefin.

The polyolefin-based film may be a film having a multilayer structure in which two or more of the above-mentioned polyolefin-based films are laminated. Preferred 2
As combinations of more than one kind, high melting point polypropylene / low melting point polypropylene, polypropylene / polyethylene, cyclic olefin (co) polymer / polypropylene,
Cyclic olefin (co) polymer / polyethylene and the like.

The polymer used in the polyolefin film used in the present invention has a melt flow rate (MF)
R) is preferably relatively large. This is because it is necessary to form a film at a low temperature because the amount of additives is reduced as described later. For this reason, the polymer used for the polyolefin-based film preferably has a low melting point and a low density.

For example, when polypropylene is used, the MFR (ASTM D1238, 230 ° C., 2.
16 kg) is preferably in the range of 3 to 40 g / 10 minutes. The density of polypropylene is 0.900
0.920 g / cm ³ , preferably 0.910 to 0.920 g
It is preferably in the range of / cm ³ . Further, the melting point of polypropylene is 140-170 ° C., preferably 145-1 ° C.
It is desirable to be in the range of 65 ° C.

When polyethylene is used, since the film can be formed at a low temperature, the value of MFR is not limited.
FR (ASTM D1238, 230 ° C, 2.16k
g) is preferably in the range of 0.5 to 5 g / 10 minutes. The density of polyethylene is 0.910 to 0.9.
50 g / cm ^3, preferably is desirably in the range of 0.910~0.940g / cm ^3. Further, the melting point of polyethylene is desirably in the range of 100 to 130 ° C, preferably 110 to 130 ° C.

In the polyolefin film according to the present invention, it is desirable to reduce the total amount of additives contained, and it is desirable that the total amount be 0.5% by weight or less, preferably 0.2% by weight or less. If the amount of the additive is more than the above range, the amount of bleeding out to the surface increases, and the smoothness of the surface may be hindered.

Examples of the additives that may be contained in the polyolefin-based film according to the present invention include an antiblocking agent, a heat stabilizer, an antioxidant, and a chlorine scavenger.

Examples of the antiblocking agent include liquid or solid paraffin, synthetic wax, polyethylene wax, waxes such as natural wax, organic antiblocking agents such as silicone and fatty acid amide, and talc (talc), diatomaceous earth, and kaolin (porcelain clay). And inorganic blocking inhibitors such as silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zinc oxide, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate and zeolite. These may be used as a mixture.

Such an antiblocking agent is preferably in the form of spherical particles, and the particle diameter is preferably in the range of 1 to 6 μm. Further, the amount of the antiblocking agent contained in the polyolefin-based film is desirably 0.01% by weight or less, preferably 0.005% by weight or less.

If the content of the blocking agent is larger than the above range, the surface of the film becomes uneven, and the smoothness of the surface may be hindered. When the polyolefin-based film is a laminated film, the polyolefin-based film layer which does not form a gas barrier layer on the polyolefin-based film may contain an anti-blocking agent. Even if the anti-blocking agent is added to the polyolefin-based film that does not form a gas barrier layer, after the formed film is wound into a roll, the anti-blocking agent is applied to the film on which the gas barrier layer is formed. In some cases, traces of irregularities on the film surface where the gas barrier layer is not formed are transferred to the resin surface of the gas barrier layer. For this reason, even in a polyolefin film layer on which a gas barrier layer is not formed, the amount of the contained antiblocking agent is desirably 0.01% by weight or less.

Examples of the heat stabilizer include 2,6-di-tert-butyl-4-methylphenol (BHT). The amount of the heat stabilizer contained in the polyolefin film is 0.1% by weight in the polyolefin film.
It is desirable that:

Examples of the antioxidant include tetrakis- {methylene- (3,5-di-3-butyl-4-hydrocinnamate)} butane (“Irganox 1010”). The amount of the antioxidant contained in the polyolefin film is desirably 0.1% by weight or less.

Examples of the chlorine scavenger include calcium stearate. The amount of the chlorine scavenger contained in the polyolefin film is desirably 0.1% by weight or less.

The polyolefin film according to the present invention is preferably produced by the following method. Specifically, a polyolefin-based resin and additives as needed are supplied to an extruder in which the extrusion hopper is set to a nitrogen atmosphere, and the polyolefin constituting the film is melted. And quench.

At this time, when the forming temperature is Tb (° C.) and the temperature of the metal roll surface is Tr (° C.), Tb and Tb
It is preferable that r satisfies the following relational expression. Tr ≦ Tb−150 [° C.] The temperature at which the polyolefin is melted and mixed is 180 to 250.
It is desirably in the range of ° C. The melt-blended polyolefin may be filtered with a filtration filter. Molding is
This is usually performed using a T-die. The molding temperature at this time is preferably in the range of 180 ° C to 250 ° C.
It is desirable that the temperature of the metal roll surface be in the range of 0 to 35 ° C.

According to such a method, a polyolefin-based unstretched film having a smooth surface as described above is produced. In particular, a film obtained by the above-described method in which the amount of an additive is reduced and the film is rapidly cooled has extremely excellent surface smoothness. Although the reason for this is not clear, it is thought that quenching of the film obtained under the condition with a small amount of additives suppresses crystallization of polyolefin in the film, thereby maintaining the surface smoothness. Can be

When the polyolefin film is a polypropylene film, it may be stretched to improve heat resistance and Young's modulus. When a laminated film is produced, a method such as coextrusion or melt extrusion lamination is used.

The thickness of the polyolefin film according to the present invention is preferably from 10 to 500 μm. If the film is too thin, the gas barrier layer may be damaged by internal stress. If the thickness is too large, cooling becomes insufficient, and the surface may be roughened due to coarsening of spherulites or bleed-out of additives.

In the polyolefin film according to the present invention, the dimensional change of the film due to heating is 120 ° C., 15 ° C.
Dimensional change rate of 4% or less when heated under
% Is preferable. In the case where the gas barrier layer formed on the surface of the polyolefin-based film according to the present invention is a silicon oxide film containing carbon or a diamond-like carbon film, these films are excellent in flexibility, so that the dimensions of the polyolefin-based film by heating are reduced. Changes are not particularly limited, but when a silicon oxide film containing carbon, an aluminum oxide film, or a silicon nitride film is formed as a gas barrier layer, these gas barrier layers have low flexibility. Therefore, cracks are likely to occur due to the elongation of the film, and therefore, it is desirable that the dimensional change of the film due to heating at 120 ° C. for 15 minutes is within the above range.

The polyolefin-based film according to the present invention has a volatile component amount of 300 μg / g or less, particularly 100 μg / g when heated at 130 ° C. for 5 minutes.
The following is preferred. The amount of volatile components is 300 μg /
If it exceeds g, the adhesive strength of the gas barrier layer tends to decrease, and the gas barrier property tends to deteriorate.

When producing a polyolefin-based film, it is desirable that the surface of the roll surface be a mirror surface. However, if the surface smoothness is too good,
The film may stick to the roll, and conversely, it may be preferable to roughen the surface of the roll.

When producing a polyolefin-based film, if the film is formed in the presence of oxygen, a part of the polyolefin-based resin may be oxidized and decomposed to produce a low-molecular-weight compound, which may adhere to the film surface. In addition, when the film is formed in the presence of oxygen, the additives added to the polyolefin resin easily bleed out and easily adhere to the film surface. Moreover, the deposit becomes a volatile gas due to the heat at the time of vapor deposition, and tends to affect the formation of the gas barrier layer. For this reason,
It is preferable to form a film in an oxygen-free state.

When the polyolefin-based film according to the present invention is used as a gas barrier film, a gas barrier layer usually made of an inorganic compound is formed on the surface of the polyolefin-based film.

The inorganic compound used as the gas barrier layer is a carbon compound, an oxygen compound, a nitrogen compound, or the like. Carbon compounds include diamond-like carbon, diamond, silicon carbide and other metal carbides. In addition, examples of the oxygen compound include silicon oxide, aluminum oxide, and other metal compounds.
Examples of the nitrogen compound include silicon nitride and other metal nitrides. Silicon oxide may contain carbon.

The gas barrier layer made of these inorganic compounds can be formed by using a physical vapor deposition method such as a CVD method, a sputtering method and a vapor deposition method. Of these inorganic compounds, silicon oxide, aluminum oxide, silicon nitride,
It is preferably used in view of the price of raw materials and ease of procurement.

The gas barrier layer made of diamond-like carbon can be formed at a low temperature, and is particularly preferably used because the obtained film has excellent flexibility. The diamond-like carbon is amorphous diamond-like carbon, and contains diamond, graphite, and polymer components. The properties of the gas barrier layer made of diamond-like carbon differ depending on the mixing ratio of these components.
Even a diamond-like carbon film having high hardness does not necessarily function as a gas barrier layer for water vapor, oxygen, and the like. The diamond-like carbon film functioning as a barrier layer such as water vapor or oxygen preferably contains hydrogen at a concentration of 50 atomic% or less, more preferably 45 atomic% or less, and still more preferably 40 atomic% or less. is there. Further, oxygen is preferably contained in the diamond-like carbon film at a concentration of 20 atomic% or less, more preferably 15 atomic% or less, and still more preferably 10 atomic% or less. (The remainder is carbon.) When such a diamond-like carbon film is formed on the surface of the polyolefin film, an ion plating method using a raw material gas and an ion beam sputtering method using a solid carbon source are used. By the physical vapor deposition method of
Can be formed.

In these methods, a plasma is generated in a film forming apparatus to ionize or excite a gas. Examples of the method include a method of applying a DC voltage to a plasma to decompose the gas, a method of decomposing a gas, , Plasma decomposition by microwave discharge, plasma decomposition by electron cyclotron resonance, and thermal decomposition by heating with a hot filament.

However, when a method of applying a DC voltage using the above film as the base film is adopted, the polyolefin film itself mounted on the electrode surface is an insulator, and no voltage is applied between the electrodes. This method is not always preferable because no plasma is generated in the film forming apparatus. Further, when the hot filament method is used, the filament must be heated to a high temperature of 500 ° C. or more, which is not preferable in consideration of the heat resistance of the base film.

On the other hand, the plasma decomposition method using the microwave plasma method or the electron cyclotron resonance can increase the film forming speed and lower the film forming temperature. Also,
In the case of forming a film on a large area film, it is preferable to use a high frequency plasma method.

The source gas for forming the thin film of the diamond-like carbon film contains carbon and hydrogen. For example, alkane-based gases such as methane, ethane, propane, butane, pentane and hexane; alkene-based gases such as ethylene, propylene, butene and pentene; alkadiene-based gases such as pentadiene and butadiene; acetylene and methylacetylene; Alkyne gases: benzene, toluene, xylene, indene, naphthalene,
Aromatic hydrocarbon gases such as phenanthrene; cycloalkane gases such as cyclopropane and cyclohexane;
Examples include alcohol-based gases such as methanol and ethanol; ketone-based gases such as acetone and methyl ethyl ketone; and aldehyde-based gases such as methanal and ethanal. The above gases can be used alone or in combination of two or more.

Other source gases include a mixed gas of the above gas and hydrogen gas, a mixed gas of the above gas and an oxygen-containing gas such as a carbon monoxide gas and a carbon dioxide gas, and a hydrogen gas.
A mixed gas of an oxygen-containing gas such as a carbon monoxide gas and a carbon dioxide gas, and a mixed gas of an oxygen gas, water vapor, and an oxygen-containing gas such as a carbon monoxide gas and a carbon dioxide gas may be used.

Further, as another raw material gas, a mixed gas of the above raw material gas and a rare gas may be used. For example, helium, argon, neon, xenon and the like can be mentioned, and these can be used alone or in combination of two or more.

The mixing amounts of hydrogen gas, oxygen gas (oxygen-containing gas), and rare gas in these mixed gases vary depending on the type of film forming apparatus to be used, the type of mixed gas, the film forming pressure, and the like. Specifically, the concentration of hydrogen contained in the formed diamond-like carbon film is 50 atomic%, preferably 45 atomic% or less, more preferably 40 atomic% or less, and oxygen atoms are 20 atomic%, preferably 15 atomic%. %, More preferably 1
It is preferable to adjust so as to be 0 atomic%.

The carbon source used for forming the diamond-like carbon film by the ion beam sputtering method includes a carbon allotrope solid such as graphite and diamond. The carbon source is installed and used at a predetermined position in the film forming apparatus. As a gas in the film formation apparatus, a rare gas, a hydrogen gas, an oxygen-containing gas, or the like can be used. However, as an oxygen source, a small amount of O ₂ or H ₂ O remaining in the film formation apparatus is sufficient. The concentration can be adjusted by the background pressure.

The diamond-like carbon film formed as described above can be confirmed by Raman spectroscopy.
The hydrogen atom concentration of this film can be confirmed by SIMS (secondary ion mass spectrometry).

The thickness of the diamond-like carbon film is determined as necessary. As the thickness increases, the adhesion to the polyolefin-based film deteriorates, or the diamond formed by the internal stress of the film is formed. 500 nm or less, more preferably 100 nm or less, since the carbon-like carbon film may peel off or the transparency of the film itself may deteriorate.
nm or less, more preferably 50 nm or less.

In order to enhance the adhesion between the surface of the polyolefin film and the gas barrier layer, if necessary,
A known treatment such as cleaning treatment such as cleaning for degreasing and dehydrating the substrate surface, and plasma treatment with an inert gas such as He or an active gas such as oxygen gas in a vacuum vessel is performed on the substrate surface. Is also good. However, it is important not to impair the surface smoothness. <Method for Producing Diamond-like Carbon Film> The apparatus used in the present invention will be described below with reference to the drawings. FIG.
It is a schematic diagram which shows an example of the apparatus which produces | generates the diamond-like carbon film of this invention. In FIG. 1, reference numeral 1 denotes a vacuum container. 2 is a magnet, 3 is an electrode with a target. Reference numeral 4 denotes a shutter mechanism, 5 denotes a gas introduction pipe, 6 denotes a high-frequency power source, 7 denotes an automatic matching device, and 8 denotes a base film (polyolefin-based film) attached to a holder.

The temperature of the substrate film is controlled by a method such as a liquid or gas circulation method.
It is preferable that the temperature is maintained at not more than 0 ° C., and therefore, a liquid circulation system having a large heat capacity is preferable. At this time, the liquid to be circulated may be a liquid heated or cooled to a predetermined temperature, and the liquid to be circulated may be water, ethylene glycol (antifreeze), alcohols. Liquid nitrogen, liquid helium and the like are preferably used.

It is preferable to use a magnet in order to improve the plasma density and the film forming speed. In FIG. 1, a permanent magnet is installed behind the electrode with the target. As a target, graphite, stainless steel, Si or the like is used.

It is preferable to apply a DC bias to the substrate in order to widen the range of the composition of the source gas that can be used or to improve the quality of the film.
100V is preferred, more preferably -400 to 10V
It is.

First, a plastic film substrate attached to a holder is placed on a cooling plate in the vacuum vessel 1. As the material of the cooling plate, stainless steel, oxygen-free copper plated with Ni, aluminum, or the like is used. The surface of the cooling plate is preferably a mirror surface from the viewpoint of cooling efficiency. However, it may be preferable to moderately roughen the film so that it does not stick to the cooling plate. Next, the inside of the vacuum vessel is made high vacuum. At this time, the degree of vacuum is set to 1 × 10 ⁻⁴ Torr (1 × 10 ⁻² P) in order to eliminate the influence of the remaining impurity gas on the film formation.
a) The following are preferred.

Next, a raw material gas is introduced from a gas introduction pipe and maintained at a predetermined pressure. The pressure at this time is 1 × 10 ⁻³ to 1
Torr (0.1 Pa to 100 Pa) is preferable. Thus, a gas barrier film having a gas barrier layer formed on the surface of a polyolefin-based film is obtained. This gas barrier film has excellent long-term storage stability and is therefore suitable as a protective film for various packaging containers.

[0074]

Since the polyolefin film of the present invention has a smooth surface, it can be used as a base material of a gas barrier film having high gas barrier properties.

[0075]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The dimensional change, the amount of volatile components, and the total light transmittance of the films in Examples and Comparative Examples were evaluated as follows. (1) Dimensional change rate The dimensional change rate is determined by taking the longitudinal direction of the film as the machine direction.
Sampling into strips 260 mm long and 10 mm wide,
Make a mark at 30mm from both ends and make it the actual size (L ₀ )
Is set to 200 mm. A load of 3 g was applied to the lower end of the sample, and the sample was suspended in an oven maintained at 120 ° C. for 15 minutes.
Heat for a minute. Take out the film, measure the length (L ₁ ) between the previously attached marks, and calculate the dimensional change rate (R) according to the following equation.
I asked.

Dimensional change rate (R) (%) = {(L ₁ −L ₀ ) / L ₀ } × 100 (2) Amount of volatile component The amount of volatile component is measured by a gas chromatograph mass spectrometer manufactured by Hewlett-Packard Company. Apparatus (GC / MS) (58
90/5972) and a film sample weighed to 15 mg were sealed in a glass tube using a TCT device manufactured by Chrompack, and heated at 130 ° C. for 5 minutes in a helium gas stream to trap and trap volatile components at −120 ° C. Next, the mixture was heated from -120 ° C. to 280 ° C. at a heating temperature of 600 ° C./min, and was subjected to a CPC type separation column (CPC: HP-1 × 30 m × 0.32 mm) under a helium gas pressure of 0.8 kg / cm ^2. ×
0.25 μm) into a gas chromatograph mass spectrometer equipped with a total ion chromatogram (TI
Obtain C). The sum of each volatile component was determined from the obtained total ion chromatogram and defined as the volatile component amount. (3) Total light transmittance The total light transmittance (%) was measured using a fully automatic haze meter (TC-H111DPK) manufactured by Tokyo Denshoku Technical Center. As a light source, a halogen lamp (condition C light) was used.

[0078]

Example 1 Production density of polypropylene film : 0.910 g / cm ³ , MFR (ASTM D12
38, 230 ° C, load 2.16 kg) 19 g / 10 mi
n, a polypropylene resin having a melting point of 148 ° C. was used. Further, as a heat stabilizer, 2,6-di-tert-butyl-4-methylphenol (BHT) is added to polypropylene,
0.1% by weight was added. Further, as an antioxidant, tetrakis- {methylene- (3,5-di-3-butyl-4-hydrocinnamate)} butane (“Irganox 101”)
0 ″) was added to polypropylene at 0.05% by weight. As a chlorine scavenger, calcium stearate was added at 0.05% by weight. No antiblocking agent was added. After a film was formed at a molding temperature of 230 ° C. using the attached melt extrusion molding machine, the film was quenched by a cooling roll having a surface temperature set at 10 ° C. to produce a film.

The surface roughness of the obtained polypropylene film and the number of projections and depressions of 100 nm or more were measured. The surface roughness was 12 nm, and the number of projections and depressions was 0.8 / 0.1 mm ² . The surface roughness was measured using a Nanop stylus probe manufactured by Seiko Instruments Inc.
Using ics1000, the surface shape was measured in a measurement range of 200 μm × 200 μm, and the average surface roughness was calculated. The number of protrusions and depressions was determined by using an atomic force microscope (AF).
M).

The polypropylene film 12
The dimensional change when heated at 0 ° C. for 15 minutes is 2.5
%, And the amount of volatile components generated when heated at 130 ° C. for 5 minutes was 118 μg / g.

Formation of Gas Barrier Layer After the thus obtained unstretched polypropylene film having a thickness of about 40 μm was attached to a substrate holder,
Is placed on the stainless steel cooling plate 7 in the vacuum vessel 1 shown in FIG. 1 and the inside of the vacuum vessel is 1.5 × 10 ⁻⁶ Torr (2 × 10 ^−4).
The pressure was reduced to Pa).

Then, acetylene gas (99.999)
%) From the inlet tube 8 to 85 cubic centimeters per minute (s
ccm). After the pressure of the source gas in the vacuum vessel 1 was set to 10 × 10 ⁻³ Torr (1 Pa), a high-frequency power of 13.56 MHz and 50 W was applied to form a film for 10 seconds to form a gas barrier layer. .

As a result of evaluating the obtained gas barrier layer by Raman spectroscopy, it was confirmed that this film was a diamond-like carbon film. When the composition of the film was determined using Rutherford forward and back scattering, the diamond-like carbon film contained 47 at% of hydrogen and 1 at% of oxygen.

About the obtained gas barrier film,
Oxygen permeability and total light transmittance were measured. Table 1 shows the results. The oxygen permeability was measured using a differential pressure gas permeability measuring system (GTR-30A) manufactured by Yanaco Analytical Industry Co., Ltd.
M) using an oxygen atmosphere at 40 ° C.

[0085]

Example 2 Production of polyethylene film : 0.918 g / cm ³ , MFR (ASTM D123)
8, 190 ° C, load 2.16 kg) 1.0 g / 10 mi
n, a linear low density polyethylene resin having a melting point of 117 ° C. was used. No additives were added to the linear low-density polyethylene resin.

The linear low-density polyethylene resin was supplied to a single-screw extruder in which the extrusion hopper was set to a nitrogen atmosphere, and 230 ° C.
After passing through a filtration filter, the mixture was extruded through a T die, wound around a metal roll cooled to 10 ° C., and cooled to obtain a polyethylene film having a thickness of 50 μm.

About the obtained polyethylene film,
When the surface roughness and the number of protrusions and depressions of 100 nm or more were measured in the same manner as in Example 1, the surface roughness was 14 nm, and the number of protrusions and depressions was 0.5 / 0.1 mm ² . Further, the temperature of the polyethylene film at 120 ° C. and 15 ° C.
The dimensional change when heated under the conditions of 1 minute was 26.0%, and the amount of volatile components generated when heated under the conditions of 130 ° C. and 5 minutes was 235 μg / g.

On the polyethylene film thus obtained, a diamond-like carbon film was formed in the same manner as in Example 1, and the oxygen transmittance and the total light transmittance were measured. Table 1 shows the results.

[0089]

Comparative Example 1 A biaxially stretched polypropylene film having a thickness of 20 μm (“OP-Z102” manufactured by Tosero Corporation) was used.

The surface roughness and the number of protrusions and depressions of 100 nm or more were measured for this biaxially oriented polypropylene film in the same manner as in Example 1.
nm, and the number of protrusions and depressions was 31 / 0.1 mm ² . Also, at 120 ° C. of the polyethylene film,
The dimensional change when heated for 15 minutes was 0.5%, and the amount of volatile components generated when heated at 130 ° C. for 5 minutes was 739 μg / g.

The biaxially stretched polypropylene film has
A diamond-like carbon film was formed in the same manner as in Example 1, and the oxygen transmittance and the total light transmittance were measured. Table 1 shows the results.

[0092]

[Comparative Example 2] A density of 0.930 g / cm ³ , MFR (AS
3. TM D1238, 190 ° C, load 2.16 kg)
Silica (A) as a blocking inhibitor in a linear low density polyethylene resin having a melting point of 121 ° C. and 0 g / 10 min.
One without addition and one with (B) 0.5% by weight added were prepared. Each resin was supplied to two single-screw extruders in which the extrusion hopper was in a nitrogen atmosphere, melted at a temperature of 230 ° C., passed through respective filtration filters, and then subjected to A layer / B layer with a two-layer forming die. Then, they were joined together in a die and extruded, wound around a metal roll cooled to 10 ° C., and cooled to obtain a polyethylene film having a thickness of 50 μm.

The surface roughness and the number of protrusions of 100 nm or more of the obtained laminated polyethylene film were measured in the same manner as in Example 1. The surface roughness was 61 nm, and the number of protrusions was 13 / 0.1 mm ² . there were. The dimensional change of this polyethylene film when heated at 120 ° C. for 15 minutes was 4.8%, and the amount of volatile components generated when heated at 130 ° C. for 5 minutes was 156 μg / g. there were.

On this polyethylene film, a diamond-like carbon film was formed on the layer A side in the same manner as in Example 1.
Oxygen permeability and total light transmittance were measured. Table 1 shows the results.

[0095]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a schematic view of a film forming apparatus for forming a gas barrier layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Magnet 3 Target electrode 4 Shutter mechanism 5 Gas introduction pipe 6 High frequency power supply 7 Automatic matching device 8 Base film attached to holder

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C08L 23/04 C08L 23/04 23/10 23/10 45/00 45/00 F term (reference) 4F071 AA14 AA15 AA20 AA39 AA83 AE22 AF07 AF30Y AF61Y BC01 BC13 BC14 BC15 BC16 4F100 AK02A AK03A AK04A AK07A BA01 BA16 DD07A GB15 GB23 JK15A JL04 JN01A JN30A YY00 YY00A 4J002 AE032 EB051 BB01 EB051

Claims (11)

[Claims] 1. A polyolefin-based film having a smooth surface having an average surface roughness SRa of 20 nm or less on one or both surfaces, measured on an area of 200 μm × 200 μm or more. 2. The method according to claim 1, wherein the number of protrusions having a height of 100 nm or more and / or depressions having a depth of 100 nm or more on the surface of the polyolefin film is less than 2 / 0.1 mm ^2. Polyolefin film. 3. The polyolefin film according to claim 1, wherein the polyolefin film is a transparent film. 4. The polyolefin film according to claim 3, wherein the light transmittance of the transparent film is 80% or more. 5. The polyolefin-based film according to claim 1, wherein the polyolefin-based film is at least one selected from the group consisting of a polyethylene film, a polypropylene film, and a cyclic olefin copolymer film. the film. 6. The polyolefin film according to claim 1, wherein the polyolefin film is a film having a multilayer structure in which two or more kinds of polyolefin films are laminated. 7. The polyolefin film according to claim 1, wherein the total amount of additives contained in the polyolefin film is 0.5% by weight or less. 8. The polyolefin film according to claim 1, wherein the amount of the antiblocking agent contained in the polyolefin film is 0.01% by weight or less. 9. The polyolefin-based film is obtained by melting a polyolefin constituting the film and forming it into a sheet, immediately wrapping it around a metal roll and quenching it, and setting the forming temperature to Tb (° C.). ), And when the temperature of the metal roll surface is Tr (° C.), Tb and T
The polyolefin film according to any one of claims 1 to 8, wherein r satisfies the following relational expression. Tr ≦ Tb-150 [° C] 10. The dimensional change when heated at 120 ° C. for 15 minutes is 4% or less.
10. The polyolefin-based film according to any one of items 1 to 9. 11. The polyolefin film according to claim 1, wherein the amount of volatile components generated when heated at 130 ° C. for 5 minutes is 300 μg / g or less.