JP2003073490A - Surface treatment method for thermoplastic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin film having suitability for melt thermal transfer printing and offset printing, and further having a printed matter having excellent water resistance. SOLUTION: The surface treatment method of the thermoplastic resin film (i) comprises a step of applying a surface modifier (A) after oxidizing the surface of the thermoplastic resin film (i) and then stretching the same. The surface modifier (A) converts the olefin copolymer (a) to which the unsaturated carboxylic acid or its anhydride is bonded with a nonionic surfactant, a nonionic water-soluble polymer, a cationic surfactant, And an aqueous dispersion obtained by dispersing in water using at least one selected from the group consisting of a cationic water-soluble polymer and a dispersant (b), wherein (a) / (b) weight per solid content Is 1
00/1 to 100/30, wherein the surface modifier (A)
Wherein the average particle diameter of the resin particles contained in the resin is 5 μm or less.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to performing a specific oxidation treatment on the surface of a thermoplastic resin film, applying a specific surface modifier to form a film, and then stretching the film in at least one direction. The present invention relates to a method for obtaining a thermoplastic resin film having good offset printing suitability and melt heat transfer printer suitability and excellent printed matter water resistance.

[0002]

2. Description of the Related Art Conventionally, as a sticker for outdoor advertisement or a label attached to a container for frozen foods, the water resistance of the sticker or the label paper, which is label paper, is poor. Coated paper was used in which the surface of the paper was further covered with a polyester film. recent years,
As such a label paper, a thermoplastic resin film having good water resistance, especially a polyolefin-based synthetic paper, is attracting attention as a promising material to substitute for the polyester film-coated paper. Such resin films are known, and the details thereof are described, for example, in Japanese Examined Patent Publication No. 46-4079.
4, JP-B-49-1782, JP-A-56-1184.
37, JP-A-57-12642 and JP-A-57-
It is described in each publication of No. 56224.

However, in such polyolefin synthetic paper, since the raw material polyolefin is non-polar, printability such as offset printing, gravure printing, letterpress printing, flexographic printing, melt heat transfer printer and sublimation heat transfer printer are available. The printer suitability is not necessarily satisfactory. Therefore, it is usually used after suitable surface treatment.

As one of such surface treatments, a corona discharge treatment oxidation treatment is applied to a film surface before stretching during the production of a polyolefin synthetic paper, a coating liquid is further applied to the surface, and then stretched. There is known a method of performing an oxidation treatment such as a corona discharge treatment. For example, JP-A-7-
Japanese Patent No. 266417 discloses that a longitudinally stretched film is
A corona treatment of 100 w · min / m ² was performed, a coating solution of an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 45 mol% was coated on the treated surface, and after drying, it was stretched in a transverse direction with a tenter, Further, there is disclosed a method for producing a laminated resin film, which comprises performing a corona treatment of 30 to 100 w · min / m ² . However, the laminated resin film produced by this method lacks melt heat transfer suitability and offset print suitability, and therefore improvement has been desired.

JP-A-11-323267 discloses, on a polymer film, an adhesive layer containing a copolymer of ethylene having an ethylene content within a specific range and an ethylenically unsaturated compound containing a functional group imparting easy adhesion. An easily-adhesive film having excellent suitability for letterpress printing is disclosed. However, this easy-adhesive film also lacks both printability for offset printing and melt heat transfer suitability, and improvement has been desired.

The inventors of the present invention have prepared an olefin copolymer (a) having an unsaturated carboxylic acid or its anhydride bonded on a thermoplastic resin film by using a nonionic surfactant, a nonionic water-soluble polymer, An aqueous dispersion prepared by dispersing at least one selected from the group consisting of a cationic surfactant and a cationic water-soluble polymer as a dispersant (b) in water, wherein the aqueous dispersion comprises (a) / (b): The weight ratio per solid content is 100/1 to 100/30, and the average particle size is 5μ.
An image-receiving film for thermal transfer obtained by applying an aqueous resin dispersion having a thickness of m or less and drying it has been proposed (Japanese Patent Application No.
000-365265). However, this thermal transfer image-receiving film also has good melt thermal transfer suitability,
There is a problem in offset printing suitability, especially in water resistance of offset printed matter, and there is room for improvement.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermoplastic resin film which is excellent in melt heat transfer suitability and offset print suitability and is also excellent in water resistance of printed matter.

[0008]

Means for Solving the Problems As a result of intensive investigations by the present inventors, excellent properties can be obtained by subjecting a thermoplastic resin film to a surface oxidation treatment, applying a specific surface modifier, and stretching. The present invention has been achieved and the present invention has been achieved. That is, the present invention provides a surface treatment method for a thermoplastic resin film (i), which comprises a step of applying a surface modifier (A) after oxidizing the surface of the thermoplastic resin film (i), and then stretching. The surface modifier (A) is an olefin copolymer (a) to which an unsaturated carboxylic acid or an anhydride thereof is bound, a nonionic surfactant, a nonionic water-soluble polymer, a cationic surfactant. , At least one selected from the group consisting of cationic water-soluble polymers (b)
Used as, an aqueous dispersion dispersed in water,
(A) / (b) weight ratio per solid content is 100 /
1 to 100/30, and the surface modifier (A)
The present invention provides a surface treatment method characterized in that the resin contained in (1) has an average particle diameter of 5 μm or less.

Preferred thermoplastic resin film (i)
As a multi-layer resin film in which a base material layer (ii) made of a thermoplastic resin is longitudinally stretched, and then a surface layer (iii) made of a thermoplastic resin is laminated on at least one surface of the base material layer (ii), A multilayer resin film in which the stretching is transverse stretching, and a base resin layer (ii) made of a thermoplastic resin and a surface layer (iii) made of a thermoplastic resin laminated on at least one surface of the substrate layer, wherein the stretching is longitudinal stretching. Can be mentioned. Further, a base material layer (ii) containing 40 to 100% by weight of a thermoplastic resin, 60 to 0% by weight of an inorganic fine powder and / or an organic filler, and 25 to 100% by weight of a thermoplastic resin, an inorganic fine powder and / or Organic filler 75-0
A multilayer resin film comprising the surface layer (iii) containing wt% is also preferable. The thermoplastic resin film (i) after the surface treatment method of the present invention has a porosity of 10 as represented by the following formula.
It is preferably -60%.

[Equation 2]

In the present invention, the thermoplastic resin film (i) is preferably made of a polyolefin resin, particularly preferably a propylene resin. The oxidation treatment in the present invention is preferably at least one treatment selected from corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, and ozone treatment. Especially 10-200W / min /
Corona treatment performed at m ² or 8,000 to 20
The frame processing is preferably performed at 10,000 J / m ² . The dispersant (b) used in the present invention is preferably a cationic water-soluble polymer. Further, the coating amount of the surface modifier (A) after drying is 0.005 g / m ²
The above is preferable.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the following, after the surface of a thermoplastic resin film (i) is subjected to an oxidation treatment, a surface modifier (A) is used.
The method of the present invention in which is applied and then stretching is described in detail. In addition, in this specification, "-" means the range which includes the numerical value described before and behind that as a minimum value and a maximum value, respectively.

[Thermoplastic resin film (i)] The thermoplastic resin used in the thermoplastic resin film (i) to which the method of the present invention is applied is an ethylene resin such as high density polyethylene or medium density polyethylene, or Polypropylene resin such as propylene resin, polymethyl-1-pentene, ethylene-cyclic olefin copolymer, polyamide resin such as nylon-6, nylon-6,6, nylon-6,10, nylon-6,12, Polyethylene terephthalate and its copolymers, polyethylene naphthalate, thermoplastic polyester resins such as aliphatic polyester, polycarbonate, atactic polystyrene,
Examples include thermoplastic resins such as syndiotactic polystyrene and polyphenylene sulfide. These may be used as a mixture of two or more.

Among these thermoplastic resins, it is preferable to use a non-polar polyolefin resin in order to further exert the effects of the present invention. Further, among the polyolefin resins, the propylene resin is preferable from the viewpoint of chemical resistance and cost. Examples of the propylene-based resin include polypropylene, which is a homopolymer of propylene and has isotactic or syndiotactic and various degrees of stereoregularity, and propylene as a main component, and ethylene, butene-1, and hexene-1. , And copolymers with α-olefins such as heptene-1,4-methylpentene-1 are used. This copolymer may be a binary system, a ternary system or a quaternary system, and may be a random copolymer or a block copolymer. When a propylene homopolymer is used, it is preferable to add 2 to 25% by weight of a resin having a melting point lower than that of a propylene homopolymer such as polyethylene or ethylene / vinyl acetate copolymer in order to improve stretchability. .

Whether the thermoplastic resin film (i) is a single layer or has a two-layer structure of a base material layer (ii) and a surface layer (iii), the thermoplastic resin film (i) is formed on the front and back surfaces of the base material layer (ii). Even with a three-layer structure in which the surface layer (iii) is present, the base material layer (ii) and the surface layer (ii
It may have a multi-layer structure in which another resin film layer is present between i), and may or may not contain the inorganic fine powder or the organic filler.

When the thermoplastic resin film (i) is a polyolefin resin film and (i) is a single layer and contains an inorganic fine powder and / or an organic filler, the polyolefin resin 40 to 99. 5% by weight,
Inorganic fine powder and / or organic filler 60-0.5
% By weight, preferably a polyolefin resin 50
˜97 wt%, inorganic fine powder and / or 50 to 3 wt% organic filler. When the thermoplastic resin film (i) has a multilayer structure and the base material layer (ii) and the surface layer (iii) contain an inorganic fine powder and / or an organic filler, the base material layer (ii) is usually a polyolefin-based material. Resin 40 to 100% by weight, inorganic fine powder and / or organic filler 60 to 0% by weight, and surface layer (iii)
Contains 25 to 100% by weight of a polyolefin resin and 75 to 0% by weight of an inorganic fine powder and / or an organic filler, preferably the base material layer (ii) is a polyolefin resin 5
0 to 97% by weight, inorganic fine powder and / or organic filler 50 to 3% by weight, and the surface layer (iii) is 30 to 97% by weight of polyolefin resin, inorganic fine powder and / or organic filler 70 to 3% by weight. %.

A base layer having a single-layer structure or a multi-layer structure (ii)
When the content of the inorganic fine powder and / or the organic filler contained in the above is more than 60% by weight, the stretched resin film tends to be broken during the lateral stretching performed after the longitudinal stretching. Surface layer (ii
If the inorganic fine powder and / or the organic filler contained in i) exceeds 75% by weight, the surface strength of the surface layer after transverse stretching is low and paper peeling tends to occur.

As the inorganic fine powder, calcium carbonate,
Examples include calcined clay, silica, diatomaceous earth, talc, titanium oxide, barium sulfate, alumina and the like, and those having an average particle size of preferably 0.01 to 15 μm, more preferably 0.2 to 7 μm are used. . Average particle size 0.0
If it is less than 1 μm, problems such as classification and aggregation are likely to occur during mixing with the thermoplastic resin, and if it exceeds 15 μm, color unevenness tends to occur.

When the thermoplastic resin film is a polyolefin resin film, the organic filler is
Polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-
6,6, a polymer of cyclic olefin, a copolymer of cyclic olefin and ethylene, or the like, having a melting point (for example, 120 to 300 ° C.) or a glass transition temperature (for example, 120 to 280 ° C.) higher than that of the polyolefin resin. Those that have are used.

Further, if necessary, stabilizers, light stabilizers, dispersants, lubricants and the like may be added. As a stabilizer, 0.001 to 1% by weight of sterically hindered phenols, phosphorus, amines, etc., as a light stabilizer, 0.001 to 1% by weight of sterically hindered amines, benzotriazoles, benzophenones, etc. A fine powder dispersant, for example, a silane coupling agent, a higher fatty acid such as oleic acid or stearic acid, a metal soap, polyacrylic acid, polymethacrylic acid, or a salt thereof may be added in an amount of 0.01 to 4% by weight. Good.

[Molding of Resin Film] The method for molding the thermoplastic resin film is not particularly limited, and various conventionally known methods can be used. As a specific example, a single layer or multiple layers connected to a screw type extruder can be used. Casting, calendering, rolling, inflation, extruding molten resin into a sheet using a T-die or an I-die, casting of a mixture of thermoplastic resin and organic solvent or oil, or solvent or oil after calendering Of the thermoplastic resin, molding from the solution of the thermoplastic resin and removal of the solvent. In the case of stretching, various known methods can be used, but as a specific example, longitudinal stretching utilizing the peripheral speed difference of rolls,
Examples include lateral stretching using a tenter oven.

[Resin Film] The thermoplastic resin film (i) to which the method of the present invention is applied uses a thermoplastic resin,
Although it may be stretched or unstretched, it is necessary that it can be stretched after the surface treatment. Further, it may contain no inorganic fine powder or organic filler, or may contain it. In addition, a resin layer which is not stretched may be provided on at least one surface of the stretched base layer.

When the thermoplastic resin film (i) is a polyolefin resin film and is a single layer and contains an inorganic fine powder and / or an organic filler, for example, the polyolefin resin is 40 to 99.5% by weight. A resin film comprising a resin composition containing 60 to 0.5% by weight of an inorganic fine powder and / or an organic filler at a temperature lower than the melting point of the above-mentioned polyolefin resin, preferably 3 to 60 ° C., uniaxially. Or by stretching in the biaxial direction, a microporous stretched resin film having fine cracks on the film surface and fine pores (voids) inside the film can be obtained.

When the thermoplastic resin film (i) has a multi-layer structure, for example, the polyolefin resin 40-
A resin film made of a resin composition containing 100% by weight and inorganic fine powder and / or 60 to 0% by weight of an organic filler is longitudinally formed at a temperature lower than the melting point of the polyolefin resin, preferably 3 to 60 ° C. lower. The base material layer (ii) is stretched, and then the polyolefin resin 25 to
A surface layer (iii) is laminated on at least one side of the base layer (ii) with a resin film made of a resin composition containing 100% by weight and an inorganic fine powder and / or 75 to 0% by weight of an organic filler. Can be used for processing.

Among the above films, more preferred is a uniaxially stretched polyolefin resin film containing 5 to 60% by weight of inorganic fine powder such as calcined clay, heavy or light calcium carbonate, titanium oxide and talc. A film in which numerous fine cracks are formed around the fine inorganic powder particles to make it semitransparent or opaque, a film in which a resin composition further containing the fine powder is further laminated and formed on the surface, and Japanese Patent Publication No. -60411, JP-A-61
Unstretched original sheet used for producing a synthetic paper, which is a laminate having a surface layer formed with a polyolefin resin film layer containing substantially no inorganic fine powder as described in JP-A-3748, etc. Examples include a sheet and a sheet after longitudinal stretching of successive biaxial stretching.

The thickness of the resin film used in the surface treatment of the first stage used in the present invention can be appropriately selected in accordance with the stretching ratio and the thickness of the film required after stretching,
Generally from 20 to 4000 μm, preferably from 100 to 300
Those having a range of 0 μm are used.

[Surface Oxidation Treatment] As the surface oxidation treatment of the substrate, it is preferable to use at least one treatment method selected from corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment and ozone treatment. More preferred are corona treatment and frame treatment. The treatment amount is 600 to 12,000 J / m ² (10 to ^{2 in} the case of corona treatment).
00 W · min / m ² ), preferably 1,200 to 9000
It is 0 J / m ² (20 to 150 W · min / m ² ). 600
If it is less than J / m ² (10 W · min / m ² ), the effect of corona discharge treatment is insufficient, and cissing occurs during subsequent coating of the surface modifier, resulting in 12,000 J / m ² (200 W · min / m ² ). m ² )
If it is over, the effect of the treatment will reach the ceiling, so 12,000J /
m ² (200 W · min / m ² ) or less is sufficient. For flame treatment, 8,000~200,000J / m ^2, preferably 20,000~100,000J / m ² is used. If it is less than 8,000 J / m ² , the effect of the flame treatment is insufficient, and cissing occurs at the subsequent coating of the surface modifier, and if it exceeds 200,000 J / m ² , the effect of the treatment reaches the ceiling. 000 J / m ² or less is sufficient.

[Surface modifier (A)] The surface modifier (A) used in the present invention comprises an olefin copolymer (a) to which an unsaturated carboxylic acid or an anhydride thereof is bound, and a nonionic interface. An aqueous dispersion prepared by dispersing at least one selected from the group consisting of an active agent, a nonionic water-soluble polymer, a cationic surfactant and a cationic water-soluble polymer as a dispersant (b) in water. Then, the weight ratio of (a) / (b) per solid content is 100/1 to 100/30, and the average particle diameter of the resin contained in the surface modifier (A) is 5
It is characterized by being less than or equal to μm.

Although not wishing to be bound by any theory, it is believed that the olefin copolymer (a) having an unsaturated carboxylic acid or its anhydride bonded thereto imparts adhesion to the substrate and melt heat transfer. Furthermore, nonionic surfactants, nonionic water-soluble polymers, cationic surfactants,
It is considered that the dispersant (b) composed of at least one selected from the group consisting of and a cationic water-soluble polymer improves offset printability.

The olefin copolymer (a) to which the unsaturated carboxylic acid or its anhydride is bound, which constitutes the surface modifier (A), is an ethylene- (meth) acrylic acid copolymer,
Alkaline (earth) metal salt of ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester-
Maleic anhydride copolymer, (meth) acrylic acid graft polyethylene, maleic anhydride graft polyethylene,
Maleic anhydride grafted ethylene-vinyl acetate copolymer, maleic anhydride grafted (meth) acrylic acid ester-ethylene copolymer, maleic anhydride grafted polypropylene, maleic anhydride grafted ethylene-propylene copolymer, maleic anhydride grafted ethylene -Propylene-butene copolymer, maleic anhydride grafted ethylene-butene copolymer, maleic anhydride grafted propylene-butene copolymer and the like.

Among these, the melting point or softening point is 13
0 ° C or less ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester-maleic anhydride copolymer, maleic anhydride graft ethylene-vinyl acetate copolymer, maleic anhydride graft (meth) Acrylic ester-ethylene copolymer, maleic anhydride-grafted ethylene-propylene-butene copolymer, maleic anhydride-grafted ethylene-butene copolymer, maleic anhydride-grafted propylene-butene copolymer are points of ink acceptability. Are particularly preferred.

The content of unsaturated carboxylic acid or its anhydride in the olefin copolymer (a) to which unsaturated carboxylic acid or its anhydride is bonded is preferably 2 to 40% by weight, more preferably 3 to 20% by weight. Preferably 4 to 15% by weight
Is particularly preferable.

In the olefin copolymer to which an unsaturated carboxylic acid or an anhydride thereof is bound, an aqueous dispersion (hereinafter referred to as an aqueous dispersion having dispersibility in water by further converting the carboxylic acid into an ammonium salt or an alkylamine salt). , Abbreviated as self-emulsification type aqueous dispersion) is not preferable because of insufficient offset printing suitability.

In the present invention, as the dispersant (b) for dispersing the above-mentioned unsaturated carboxylic acid or anhydride-bonded olefin copolymer in water, a nonionic surfactant, a nonionic water-soluble polymer, It is necessary to use at least one selected from the group consisting of cationic surfactants and cationic water-soluble polymers. Anionic surfactants, such as polysulfonic acid sodium salts, which are widely used as dispersants, are not preferable because they may reduce offset printability.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oxypropylene block polymer, polyethylene glycol fatty acid ester, and polyoxyethylene sorbitan fatty acid ester. it can. Further, examples of the nonionic water-soluble polymer include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and modified products thereof, and hydroxyethyl cellulose.

Examples of the cationic surfactant include stearylamine hydrochloride, lauryltrimethylammonium chloride, trimethyloctadecylammonium chloride and the like. Further, as the cationic water-soluble polymer, a polymer having a quaternary ammonium salt structure or a phosphonium salt structure, a nitrogen-containing (meth) acrylic polymer, and a nitrogen having a quaternary ammonium salt structure (meth)
An acrylic polymer can be illustrated.

Among these, from the viewpoints of adhesion to a thermoplastic resin film and suitability for offset printing, a nitrogen-containing (meth) acrylic polymer or a nitrogen-containing (meth) acrylic polymer having a quaternary ammonium salt structure is used. It is particularly preferable to use a cationic water-soluble polymer such as

To disperse the olefin copolymer (a) having an unsaturated carboxylic acid or its anhydride bonded thereto in water using the dispersant (b), the weight per solid content of (a) / (b) is used. The ratio should be 100/1 to 100/30, preferably 100/2 to 100/20, and more preferably 100/5 to 100/15. 100 / 1-
When the amount of the dispersant used is less than the range of 100/30, the olefin copolymer to which the unsaturated carboxylic acid or its anhydride is bound cannot be dispersed in water. On the contrary, when the amount of the dispersant used is large, the effect of improving the poor adhesion of the melted thermal transfer ink under high temperature and high humidity is adversely affected.

The average particle diameter of the resin particles in the component (A) in the present invention must be 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less. When it exceeds 5 μm, not only the static stability of the aqueous dispersion is deteriorated, but also the adhesion of the thermoplastic resin film to the support is deteriorated.

An olefin copolymer (a) to which an unsaturated carboxylic acid or an anhydride thereof is bound by using the dispersant (b).
Is dispersed in water by, for example, heating and dissolving the olefin-based copolymer in an aromatic hydrocarbon solvent, mixing and stirring the dispersant (b), and then phase-transforming while adding water, A method for obtaining an aqueous dispersion by distilling off an aromatic hydrocarbon solvent, or, as disclosed in JP-B-62-29447, supplying the olefin copolymer to a hopper of a twin-screw extruder. Then, an aqueous solution of the dispersant (b) is added to the state of being heated and melted, melted and kneaded, and then water is added to obtain a dispersion liquid. Among these, when the dispersant (b) is a cationic water-soluble polymer such as a nitrogen-containing (meth) acrylic polymer or a (meth) acrylic polymer having nitrogen having a quaternary ammonium salt structure, From the viewpoint of the average particle diameter of the resin particles in the obtained aqueous dispersion, it is preferable to use a twin-screw extruder. If necessary, an auxiliary agent such as a defoaming agent, a wetting agent or an anti-blocking agent may be added to the surface modifier of the present invention within a range that does not impair the suitability for melt thermal transfer and the suitability for offset printing.

[Formation of Surface Modification Layer] Each component of the above surface modification agent is used as it is or after being diluted and dissolved in a hydrophilic solvent such as water, methyl alcohol, ethyl alcohol, isopropyl alcohol or the like. However, it is preferable to use it in the form of an aqueous solution. The solution concentration is usually 0.
It is about 05 to 60% by weight, preferably about 0.1 to 40% by weight. If it is less than 0.05% by weight, it is necessary to take measures such as a drying process of water and extension of drying time, and if it exceeds 60% by weight, coating unevenness tends to occur.

The coating method is a roll coater, blade coater, bar coater, air knife coater, size press coater, gravure coater, reverse coater, die coater, lip coater, spray coater, etc. ,
Excess water and hydrophilic solvent are removed through a drying process.

The coating amount is 0.005 as the solid content after drying.
Preferably to 10 g / m ^2, more preferably ^{0.01~1g / m 2, 0.01~0.6g / m} 2 is particularly preferred.
If it is less than 0.005 g / m ² , the improvement effect is insufficient,
If it exceeds 10 g / m ² , the effect tends to be saturated.

[Stretching] In the present invention, the thermoplastic resin film is surface-oxidized, and then a surface modifier is applied, and the resin film is stretched simultaneously with drying the surface modifier. Although not wishing to be bound by any theory, it is believed that by drying the surface treatment agent during stretching, the base material and the surface modifier are firmly fixed, resulting in an increase in the water resistance of the printed matter. .

For the stretching, various conventionally known methods can be used. Specific examples include, in the case of an amorphous resin, the glass transition temperature of the thermoplastic resin to be used or higher, and in the case of a crystalline resin, an amorphous state. In the range of not less than the glass transition temperature of the portion and not more than the melting point of the crystal portion, it can be carried out in a known temperature range suitable for each thermoplastic resin, and longitudinal stretching utilizing the peripheral speed difference of the roll group, a tenter oven. The transverse stretching used, rolling, and simultaneous biaxial stretching using a combination of a tenter oven and a linear motor can be performed.

The stretching temperature is 2 to 60 ° C. lower than the melting point of the thermoplastic resin used, and 110 to 164 when the resin is a propylene homopolymer (melting point 155 to 167 ° C.).
C., 110 to 120.degree. C. for high-density polyethylene (melting point 121 to 134.degree. C.) and 104 to 115.degree. C. for polyethylene terephthalate (melting point 246 to 252.degree. C.), which are appropriately selected depending on the stretching process and conditions.

The stretch ratio is not particularly limited and is appropriately selected depending on the purpose and the characteristics of the thermoplastic resin used. For example, when a propylene homopolymer or a copolymer thereof is used as the thermoplastic resin, it is about 1.2 to 12 times, preferably 2 to 10 times, when it is stretched in one direction.
In the case of biaxial stretching, the area magnification is 1.5 to 60 times, preferably 10 to 50 times. When using other thermoplastic resins, it is 1.2 to 10 times, preferably 2 to 5 times in the case of stretching in one direction, and 1.5 to 20 times in area magnification in the case of biaxial stretching, preferably Is 4 to 12 times. Further, heat treatment at a high temperature is performed if necessary. The stretching speed is preferably 20 to 350 m / min.

When the thermoplastic resin film contains inorganic fine powder or organic filler, fine cracks are formed on the surface of the film and fine voids are formed inside the film. The thickness of the stretched thermoplastic resin film (i) is 20 to 5
00 μm is preferable, and 35 to 300 μm is more preferable. In the present invention, the surface oxidation treatment may be performed again on the stretched film for the purpose of preventing the film from being charged.

The stretched thermoplastic resin film has, for example, a porosity of 10 to 60% represented by the above formula of the base material portion,
Density 0.650 to 1.20 g / cm ³ , opacity 75%
As described above, it has preferable physical properties that the Bekk smoothness is 50 to 25,000 seconds.

[0049]

EXAMPLES Examples 1 to 4 below show examples of producing a thermoplastic resin sheet and a surface modifier, and various surface treatment methods using these materials in Examples 1 to 9 and Comparative Examples 1 to 6. And the evaluation after these surface treatments was performed in Test Examples 1 and 2. Details of the materials used in the examples are shown in Table 1. In addition, the materials shown in the following examples, the amount used, the ratio,
The processing content, processing procedure, and the like can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the following specific examples.

[0050]

[Table 1]

<Production Example 1> Thermoplastic resin sheet (P
1) Production PP1 85% by weight, inorganic fine powder (a) 15% by weight
The compounded composition (c ′) was kneaded by an extruder set at 240 ° C., extruded into a sheet, and cooled by a cooling device to obtain an unstretched sheet. In addition, the composition extruded in the above-mentioned sheet shape and the composition used for the following extrusion and lamination include 3-methyl-2,6 with respect to 100 parts by weight of the total amount of the propylene homopolymer and calcium carbonate used.
-0.05 parts by weight of di-t-butylphenol and 0.05 parts by weight of phenolic stabilizer (Ciba-Gaiki, trade name: Irganox 1010), phosphorus stabilizer (Borg Warner Co., Ltd., trade name: West) 618) 0.05
Parts by weight were compounded. This sheet was heated to a temperature of 140 ° C. and stretched 5 times in the machine direction. Composition (a ') in which 50% by weight of PP2 and 50% by weight of inorganic fine powder (a) are mixed
Melt-kneaded with an extruder set at 250 ° C., 55% by weight of PP2 and 45% of inorganic fine powder (a)
The composition (b ') mixed by weight% was melt-kneaded by another extruder set at 250 ° C and laminated in a die to obtain the above laminate so that (a') was on the outside. The thermoplastic resin sheet (P1), which is a five-layer laminate (a '/ b' / c '/ b' / a '), was obtained by coextruding the obtained 5-fold lengthwise stretched sheet on both sides.

<Production Example 2> Thermoplastic resin sheet (P
Production of 2) A five-layer laminate was obtained in the same manner as in Production Example 1 except that PP2 in the composition of a ′ in Production Example 1 of the resin sheet before transverse stretching was changed to PP3, and this was a thermoplastic resin sheet. (P
2).

<Production Example 3> Production of surface modifier (A1) N, N-dimethylaminoethyl methacrylate 62.9
Parts by weight, 71 parts by weight of butyl methacrylate, 25.4 parts by weight of lauryl methacrylate and 200 parts by weight of isopropyl alcohol were placed in a four-necked flask equipped with a stirrer, a dry distillation condenser, a thermometer, and a dropping funnel, and after nitrogen gas replacement, 2,2'-azobisisobutyronitrile 0.9
Part by weight was added as a polymerization initiator, and a polymerization reaction was carried out at 80 ° C. for 4 hours. Then, after neutralizing with 24 parts by weight of acetic acid, water was added while distilling off isopropyl alcohol to finally obtain a viscous dispersant aqueous solution having a solid content of 35%.

Twin-screw extruder in the same direction (made by Ikegai Co., Ltd.,
Product name: PCM45φ), ethylene-methacrylic acid copolymer (methacrylic acid content 10%, MFR35g / 10
Min) was continuously fed at a rate of 100 parts by weight / hour.
Further, the aqueous solution of the dispersant prepared above the first inlet of the extruder was continuously supplied at a rate of 22.9 parts by weight / hour (as a solid content of the dispersing agent, 8 parts by weight / hour). Then
Further, while continuously supplying water at a rate of 70 parts by weight / hour from the second inlet of the extruder, it was continuously extruded at a heating temperature (cylinder temperature) of 130 ° C. to obtain a milky white resin aqueous dispersion. . This aqueous resin dispersion was filtered through a 250-mesh stainless wire net, and water was added so that the solid content was 45% to obtain a surface modifier (A1) containing a cationic water-soluble (meth) acrylic resin. It was The average particle diameter of this resin aqueous dispersion was measured by a laser particle size distribution measuring device (manufactured by Shimadzu Corporation,
It was 0.74 μm as measured by SALD-2000).

<Production Example 4> Preparation of surface modifier (B1) A self-emulsifying aqueous liquid of ethylene-ammonium acrylate copolymer, Saixen A (manufactured by Sumitomo Seika Co., Ltd., dispersant-free product) ) Was prepared, and this was used as a surface modifier (B1).

<Example 1> (1) Oxidation treatment Corona discharge treatment was performed on the front surface of the thermoplastic resin sheet (P1) using a corona discharge treatment machine (HFS400F, manufactured by Kasuga Denki KK). At this time, a silicone-coated roll was used as the aluminum electrode and the treater roll, the gap between the electrode and the roll was set to 2 mm, and the line speed was about 30 m / min.
The treatment was performed at an applied energy density of 100 W · min / m ² . (2) Application of surface modifier The surface modifier (A) was applied to the surface subjected to the corona discharge treatment so that the coating amount when dried was about 0.15 g / m ^2, and Led to the tenter oven. (3)
Stretching The thermoplastic resin sheet that has been subjected to the above-mentioned oxidation treatment and coating is heated to 155 ° C. in a tenter oven, and then stretched 8.5 times in the transverse direction to form a 5-layer laminated film (each layer having a thickness of 110 μm). Thickness of 6μm / 23μm / 52μm / 23
μm / 6 μm) was obtained.

Comparative Example 1 A film was prepared in the same manner as in Example 1 except that the surface modifier was not applied.

Comparative Example 2 A film was produced in the same manner as in Example 1 except that the surface modifier (A1) was applied without performing corona discharge treatment before stretching. A cissing occurred when the surface modifier (A1) was applied. The evaluation was stopped because a uniform coated surface could not be obtained.

Comparative Example 3 A film was produced in the same manner as in Example 1 except that the surface modifier (A1) was changed to the surface modifier (B1).

<Examples 2 to 3> Films were produced in the same manner as in Example 1 except that the coating amount was changed to the amount shown in Table 2.

<Examples 4 to 5> Films were prepared in the same manner as in Example 1 except that the corona treatment amount before stretching was changed to the amount shown in Table 2.

<Comparative Example 4> The corona treatment amount before stretching was 5 W.
A film was produced by the same operation as in Example 1 except that the film was changed to min / m ² . The evaluation was stopped because flicker occurred during application of the surface modifier (A1) and a uniform application surface could not be obtained.

<Example 6> Five-layer laminate (P1) before stretching
Both surfaces of each of the above were treated with a direct flame plasma processing machine (Flynn F3000 made by FLYNN BURNER) using propane as a combustion gas, a line speed of 40 m / min, an applied energy of 37,70.
Example 1 except that frame processing was performed at 0 J / m ² .
A film was produced by the same operation as described above.

Example 7 A film was produced in the same manner as in Example 6 except that the applied energy in the frame treatment before stretching was 28000 J / m ² .

Example 8 A film was produced in the same manner as in Example 6 except that the applied energy in the frame treatment was 60600 J / m ² and the line speed was 70 m / min.

<Example 9> Thermoplastic resin sheet (P2)
A film was produced by the same operation as in Example 1 except that was used.

<Comparative Example 5> Thermoplastic resin sheet (P1)
Example 1 without the oxidation treatment and the application of the surface modifier.
Stretching treatment was carried out in the same manner as in, and thereafter, oxidation treatment and coating of the surface modifier (A) were carried out in the same manner as in Example 1. Then, it is dried at a drying temperature of 60 ° C. to a thickness of 11
5-layer laminated film of 0 μm (thickness of each layer 6 μm / 23 μ
m / 52 μm / 23 μm / 6 μm).

<Comparative Example 6> A film was produced in the same manner as in Comparative Example 5 except that the drying temperature after coating the surface modifier (A) was changed to 155 ° C. The evaluation was stopped because most of the dried film contracted.

<Test Example 1> Examples 1 to 9 and Comparative Example 1
The suitability for melt heat transfer of the films prepared in Examples 1 to 6 was evaluated as follows. In addition, a bar code printer (manufactured by Tech Co., Ltd., trade name: B-30-S5) and a melt-type resin ink ribbon (manufactured by Ricoh Co., Ltd., trade name: B) are used for printing.
110C) was used.

[Evaluation of Ink Transferability] On one side of the film,
Using the above printer and ink ribbon,
A bar code was printed under conditions of ° C and relative humidity of 85%, and the ink transferability was evaluated according to the following 5 grades. 5: Good (clear image can be obtained) 4: Possible (Slight blurring is seen in barcode printing etc., but it is at a practical level.) 3: Not possible (line breaks in barcode printing etc. occur. ) 2: Not possible (hard to read printed characters) 1: Not possible (almost no ink is transferred)

[Ink Adhesion Evaluation] On one surface of the film,
Using the above printer and ink ribbon, 23
A bar code was printed under conditions of ° C and 50% relative humidity. Print the printed matter under the conditions of 35 ° C and relative humidity of 85%.
After adjusting the condition for a period of time or longer, a cellophane tape was attached to the surface, and after sufficiently adhering, the cellophane tape was slowly peeled off, and the ink adhesion was evaluated according to the following 5 grades. 5: Good (No ink is peeled off at all) 4: Yes (Ink is peeled off at a small portion, but it remains at a practical level) 3: Not possible (Peeled portion is less than 25%) 2: Not possible ( The peeled portion was 25% to 75%) 1: No (the peeled portion was more than 75%)

Test Example 2 Offset Printing Suitability Test The offset printing suitability of the films prepared in Examples 1 to 9 and Comparative Examples 1 to 6 was evaluated as follows. For evaluation, a printing machine (manufactured by Akira Seisakusho Co., Ltd., product name: R
I-III type printability tester) and printing ink (T Co., Ltd.)
& K TOKA, product name: Best Cure 161
(Ink)) was used.

[Ink Transferability] After the film was stored in an atmosphere of 23 ° C. and a relative humidity of 50% for 3 days, the thickness of the ink was 1.5 g / m ^{2 on} the coating surface of the film in the printing machine. Printed on the printed surface and the printed surface is a light reflection densitometer
Made by Kolmogen (USA), product name: Macbeth Densitometer)
The Macbeth concentration was measured at.

[Ink Adhesion] After the film was stored for 3 days in an atmosphere of 23 ° C. and a relative humidity of 50%, the thickness of the ink was 1.5 g / m ^{2 on} the coating surface of the film in the printing machine. After printing and irradiating by passing once at 10 cm under a single metal halide lamp (80 W / cm) manufactured by Eye Graphic Co., Ltd. at a speed of 10 m / min,
The adhesion strength was measured with an adhesion strength measuring instrument (trade name: Internal Bond Tester, manufactured by Kumagai Riki Kogyo Co., Ltd.).
The above adhesion strength is measured by sticking an aluminum angle on the upper surface of the sample with cellophane tape on the printed surface, setting the lower surface in the same holder and swinging the hammer down at an angle of 90 degrees, and then impacting the aluminum angle. Is added and the peeling energy at that time is measured. Adhesion strength of 1.2 kg / cm or more is passed.

[Water resistance] The film was placed at 23 ° C. and a relative humidity of 5
After storing in a 0% atmosphere for 3 days, the above ink was printed on the coated surface of the film by the above printing machine so as to have a thickness of 1.5 g / m ² , and a metal halide lamp (80 W / After irradiating 10 cm under one lamp at a speed of 10 m / min once, the printed matter was immersed in water at 23 ° C. for 3 hours. Thereafter, the printing surfaces were rubbed together 30 times in 30 seconds while bending the printing surfaces in water to evaluate the scratchability of the printing surface in water. The evaluation criteria are as follows. 5: Good (No ink is peeled off at all) 4: Yes (Ink is peeled off at a small portion, but it remains at a practical level) 3: Not possible (Peeled portion is less than 25%) 2: Not possible ( The peeled portion was 25% to 75%) 1: No (the peeled portion was more than 75%)

The processing conditions at the time of film production and the test results are summarized in Tables 2-3. The porosity of the film is also shown in the table.

[0077]

[Table 2]

[0078]

[Table 3]

[0079]

INDUSTRIAL APPLICABILITY According to the present invention, in melt heat transfer printing, ink transferability, adhesion and water resistance are excellent under high temperature and high humidity environment, and in offset printing, ink transferability, adhesion and water resistance are excellent. It was possible to provide a thermoplastic resin film.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 101/00 C08L 101/00 // B29L 7:00 B29L 7:00 9:00 9:00 F term ( reference) 4F006 AA12 AB13 AB24 BA01 CA07 EA01 EA03 4F074 AA16 AA24 AA25 AA97 AC26 AC37 AD12 AE01 AG01 AG03 CA01 CA03 DA02 DA20 DA52 4F210 AA11 AB11 AB16 AC03 AG03 AH81 QA02 QC03 QD08 QG01 QG15 QG18 4J002 BB03W BB05W BB10W BB12W BB14W BB15W BB17W BC03W BK00X CF03W CF06W CF06X CF07X CG00W CG00X CL01W CL01X CL03W CL03X CN01W DE136 DE146 DE236 DF016 DG046 DJ006 DJ036 FD01X FD016 FD310 GF00 GK03

Claims (11)

[Claims] 1. A surface treatment method for a thermoplastic resin film (i), comprising the steps of applying a surface modifier (A) after oxidizing the surface of the thermoplastic resin film (i), and then stretching. The surface modifier (A) is an olefin copolymer (a) to which an unsaturated carboxylic acid or an anhydride thereof is bound, a nonionic surfactant, a nonionic water-soluble polymer, a cationic surfactant. And at least one selected from the group consisting of cationic water-soluble polymers as a dispersant (b), which is an aqueous dispersion liquid dispersed in water, wherein (a) / (b) per solid content Weight ratio is 100 /
1 to 100/30, wherein the average particle diameter of the resin particles contained in the surface modifier (A) is 5 μm or less. 2. The thermoplastic resin film (i) is obtained by longitudinally stretching a base material layer (ii) made of a thermoplastic resin, and then at least one surface of the base material layer (ii) is a surface layer made of a thermoplastic resin. It is a multilayer resin film which laminated | stacked (iii), Comprising: The said extending | stretching is lateral extending | stretching, The surface treatment method of Claim 1. 3. A multilayer resin film, wherein the thermoplastic resin film (i) is a substrate layer (ii) made of a thermoplastic resin, and a surface layer (iii) made of a thermoplastic resin laminated on at least one surface of the base material layer (ii). The surface treatment method according to claim 1, wherein the stretching is longitudinal stretching. 4. The thermoplastic resin film (i) comprises 40 to 100% by weight of a thermoplastic resin, an inorganic fine powder and //
Alternatively, a base material layer (ii) containing 60 to 0% by weight of an organic filler, and a surface layer (iii) containing 25 to 100% by weight of a thermoplastic resin, 75 to 0% by weight of an inorganic fine powder and / or an organic filler. The surface treatment method according to claim 2, wherein the surface treatment method is a multi-layer resin film comprising 5. The thermoplastic resin film (i) after the surface treatment method has a porosity of 10 to 6 represented by the following formula.
It is 0%, The surface treatment method in any one of Claims 1-4. [Equation 1] 6. The thermoplastic resin film (i) is made of a polyolefin resin.
5. The surface treatment method according to any one of to 5. 7. The surface treatment method according to claim 6, wherein the polyolefin resin is a propylene resin. 8. The oxidation treatment is at least one treatment selected from corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, and ozone treatment. The surface treatment method described in. 9. The oxidation treatment is 10 to 200 W · min /
Corona treatment performed at m ² or 8,000 to 20
The surface treatment method according to claim 8, wherein the surface treatment is performed at a rate of 10,000 J / m ² . 10. The surface treatment method according to claim 1, wherein the dispersant (b) is a cationic water-soluble polymer. 11. The surface treatment method according to claim 1, wherein a coating amount of the surface modifier (A) after drying is 0.005 g / m ² or more.