JP5448944B2 - Antistatic white polyester film - Google Patents

Description

  The present invention relates to an antistatic single-layer white polyester film, which is excellent in adhesion to ink, matteness, curl resistance, and transportability, and has particularly high concealability and whiteness, as a core sheet of an IC card. The present invention relates to an antistatic white film preferably used.

  Since IC cards are superior to conventional magnetic cards such as credit cards and cash cards in terms of large recording capacity and multi-functionality, they are being put to practical use as an alternative to them. The IC card has a configuration in which a built-in module including an integrated circuit (IC chip) and an antenna coil is embedded in a plastic card, like a conventional magnetic card. Although there are several types of this configuration, the configuration is basically a three-layer configuration in which a built-in module is sandwiched between core sheets, and oversheets are provided as protective layers on both sides of the core sheet. At that time, like a prepaid card or a credit card, a pattern is printed on one side or both sides of the core sheet, or a magnetic recording layer is provided if necessary. Conventionally, a metal, an epoxy resin, or a hard vinyl chloride resin is used as the core sheet, and recently, a polyimide resin may also be used. However, when these are used as a core sheet, the structure in which the built-in module is sandwiched between the core sheets requires high concealability and whiteness so that the internal IC chip or circuit cannot be seen through.

  Conventionally, as a polyester film for a magnetic card, for example, a concealing film shown in Patent Document 1, Japanese Patent Laid-Open No. 8-138231, etc. is known. The module cannot be sufficiently hidden. As an improvement measure, the film has a laminated structure, and the white pigment concentration in the core layer is increased to about 50% by weight, so that the film satisfies the concealing property. There is a problem that becomes difficult.

  On the other hand, in the case of a white / black multilayer film as shown in Patent Document 2, the black pigment contained in the black layer is 2% by weight or more, which raises a problem of cost increase required for pigment addition.

  Furthermore, when a film is printed and bonded in a process of passing between rolls, the film tends to be charged with static electricity, and the occurrence of sparks in a solvent-using atmosphere may lead to an explosion. Also, if foreign matter is attracted by charging, printing and coating may be lost, which is a big problem in the quality of the processed product.

JP-A-8-108458 JP 2001-26087 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is excellent adhesion, matting, curl resistance, and transportability with respect to ink. An object of the present invention is to provide an antistatic single-layer white film suitably used as a core sheet of a card.

  As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be easily solved by a film having a specific configuration, and has completed the present invention.

That is, the gist of the present invention is that a coating layer having a surface resistivity of 1 × 10 ⁶ to 1 × 10 ¹² Ω is formed on at least one surface of a white polyester film composed of a single layer containing 10 to 100 ppm of a black pigment. A polyurethane resin containing as a constituent component a polycarbonate polyol and a compound obtained by quaternizing a tertiary amino group of a chain extender having a tertiary amino group in the molecule, and a cationic polymer antistatic An antistatic white polyester film characterized in that the film has a transmission density OD of 0.9 or more and a hue L * value of 91 or more.

  According to the present invention, it has excellent adhesion to mats, matte properties, curl resistance, and transportability, and particularly has high concealment and whiteness, and is suitable for use as an IC card core sheet. A single layer white film can be provided, and the industrial value of the present invention is high.

  Hereinafter, the present invention will be described in more detail.

  As the polyester constituting the polyester film of the present invention, typically, for example, polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, and 80 mol% or more of the structural unit is ethylene-2,6-naphthalate. Specific polyethylene-2,6-naphthalate and poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of the structural unit is 1,4-cyclohexanedimethylene terephthalate. Other examples include polyethylene isophthalate and polybutylene terephthalate.

  Examples of copolymer components other than the above-described dominant components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, and polytetramethylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid, and 5-sodium dicarboxylic acid. Ester-forming derivatives such as diasulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and oxymonocarboxylic acid can be used. Further, as the polyester, in addition to a homopolymer or a copolymer, a small proportion of a blend with another resin can also be used.

  In this invention, it consists of a white polyester film which consists of a single layer, and usually contains a white pigment in a film. As the white pigment, conventionally known pigments can be used. For example, titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, zinc sulfide and the like can be used. In particular, titanium oxide is preferably used because it has a high refractive index and can impart high concealability to a film with a relatively small amount.

  The average particle diameter of the white pigment used in the present invention is usually in the range of 0.1 to 1.0 μm, and the content is usually 5 to 35% by weight. If the average particle size is less than 0.1 μm, the film concealing property tends to be inferior, whereas if it exceeds 1.0 μm, the film forming continuity tends to be inferior. On the other hand, if the content is less than 5% by weight, the whiteness and hiding property of the film tend to be inferior, whereas if it exceeds 35% by weight, the film forming continuity tends to be inferior.

  The monolayer film of the present invention needs to have a hue L * value of 91 or more from the viewpoint of whiteness, and is preferably in the range of 92 to 98. When the L * value is less than 91, the design properties as a white film (IC card) are inferior. On the other hand, the upper limit of the L * value is not limited, but it is 100 or less by definition. In order to set the L * value to 91 or more, for example, the average particle diameter and the addition amount of the white pigment may be adjusted. In particular, when the addition amount is increased, the L * value tends to be improved, and it is preferable to adjust the addition amount within the above range. Moreover, it becomes possible to make L * value into a desired range by suppressing the addition amount of the black pigment used together.

  In the present invention, a black pigment typified by carbon black is contained in a polyester film composed of a single layer at a low concentration of 10 to 100 ppm. Here, the black pigment preferably has an average primary particle diameter of 0.2 μm or less. If the average particle size of the primary particles exceeds 0.2 μm, the higher-order aggregated particle size in the polyester film tends to increase, and density unevenness tends to occur. If the content is less than 10 ppm, the concealability is insufficient. On the other hand, when the content exceeds 100 ppm, the whiteness becomes insufficient.

  The single-layer film of the present invention needs to have a transmission density OD of 0.9 or more from the viewpoint of concealability, and is preferably in the range of 0.9 to 1.2. When the OD is less than 0.9, the concealability is insufficient when an IC card is produced, the internal IC chip can be seen through, and the design of the pattern printing on the card surface layer is deteriorated. On the other hand, the upper limit of OD is not defined, but if it exceeds 1.2, the quality becomes excessive and the cost increases, which is not preferable.

  In the present invention, in order to achieve both high concealability and whiteness, which are the main characteristics of an IC card film, it is important to limit the black pigment content in the single layer film to a very small amount. .

  The polyester film of the present invention preferably further contains 0.01 to 1.0% by weight of amorphous silica particles having an average particle size of 0.1 to 1.0 μm. When the average particle size is less than 0.1 μm or the content is less than 0.01% by weight, the film transportability tends to be inferior. On the other hand, if the average particle diameter exceeds 1.0 μm or the content exceeds 1.0% by weight, the film-forming continuity is lowered and the cost is increased due to excessive quality.

  In addition to the pigment and silica particles described above, the polyester film of the present invention may include conventionally known antioxidants, heat stabilizers, lubricants, fluorescent brighteners, dyes, ultraviolet absorbers, and near infrared absorption as necessary. Additives such as agents can be added.

The white polyester film of the present invention may have a coating layer having a surface resistivity (measured at 23 ° C., 50% RH) in the range of 1 × 10 ⁷ to 1 × 10 ¹² Ω on at least one surface. is necessary. When the surface specific resistance value exceeds 1 × 10 ¹² Ω, there is a problem in attracting foreign matters to the film surface due to static electricity when the film is processed by passing between rolls. The surface specific resistance value is preferably 1 × 10 ¹¹ Ω or less, more preferably 1 × 10 ¹⁰ Ω or less. On the other hand, when the surface specific resistance value is less than 1 × 10 ⁷ Ω, the antistatic effect is saturated and a large amount of antistatic agent is required, and the uniformity of the coated surface tends to be impaired. The surface specific resistance value is preferably 1 × 10 ⁸ Ω or more, more preferably 1 × 10 ⁹ Ω or more.

  The polyester film of the present invention may have a coating layer containing a polyurethane resin (A) containing the following components a1 and a2 as structural units and a cationic polymer antistatic agent (B) on at least one surface. is necessary.

a1: Polycarbonate polyol a2: Compound obtained by quaternizing a tertiary amino group of a chain extender having a tertiary amino group in the molecule The polyurethane resin (A) of the present invention needs to contain a polycarbonate unit as a polyol. . By using a polyurethane resin containing a polycarbonate polyol, the printability (ink adhesion) is highly improved.

  The a1 used in the polyurethane resin (A) of the present invention is, for example, a transesterification reaction between a lower dialkylene carbonate such as diethyl carbonate or a carbonate such as diphenyl carbonate and a diol, or directly reacting phosgene with the diol. Can be obtained. In the present invention, as the diol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Polycarbonate polyols using diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be used. Moreover, said polycarbonate diol is the number average molecular weight of polystyrene conversion by gel permeation chromatography (GPC), and it is preferable that it is 300-4000. Furthermore, the addition amount of these polycarbonate polyols can be selected in the range of 40 to 80% by weight with respect to the polyurethane resin (A).

  In the present invention, examples of the polyisocyanate used in the polyurethane resin (A) include known aliphatic, alicyclic and aromatic polyisocyanates.

  Specific examples of the aliphatic polyisocyanate include, for example, tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene. Examples thereof include diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate.

  Specific examples of the alicyclic polyisocyanate include, for example, isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4′-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis (isocyanate). And methyl) cyclohexane and 1,4-bis (isocyanatomethyl) cyclohexane.

  Specific examples of the aromatic polyisocyanate include, for example, tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate and the like can be mentioned. These polyisocyanates may be used alone or in combination of two or more.

  The polyurethane resin (A) used in the present invention can coexist with polyoxyalkylene glycol as a polyol component together with the a1 (polycarbonate polyol) in order to improve adhesiveness. Specific examples of the polyoxyalkylene glycol to be contained in the polyurethane (A) include polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutanediol, polyoxyethylene glycol-polyoxypropylene glycol block copolymer, and the like. it can.

  In addition, the molecular weight of these polyoxyalkylene glycols is preferably a number average molecular weight in terms of polyoxyethylene glycol by gel permeation chromatography (GPC) and is 200 to 3000. Furthermore, the addition amount of these polyoxyalkylene glycols can be selected in the range of 3 to 10% by weight with respect to the polyurethane resin (A).

  In the present invention, the polyurethane resin (A) needs to contain a2 (a compound obtained by quaternizing the tertiary amino group of the chain extender having a tertiary amino group in the molecule) as a structural unit. Thereby, the polyurethane resin (A) becomes self-emulsifying, and it is possible to make a stable dispersion in a medium mainly composed of water without adding an emulsifier. Moreover, since the polyurethane resin (A) is the same cationic polymer as the cationic polymer antistatic agent (B) described later, even when both are mixed, intermolecular ionic aggregation does not occur.

  As the chain extender used in the polyurethane resin (A) of the present invention, N-alkyl dialkanolamines such as N-methyldiethanolamine and N-ethyldiethanolamine, N-methyldiaminoethylamines, N-ethyldiaminoethylamines and the like N- Examples thereof include alkyldiaminoalkylamine and triethanolamine. These chain extenders having a tertiary amino group can be used alone or in combination of two or more. Moreover, the addition amount of these chain extenders can be chosen from the range of 5 to 15 weight% with respect to a polyurethane resin (A).

  In the present invention, the chain extender having the tertiary amino group introduced into the polyurethane resin is neutralized with an acid or a cationic polyurethane resin containing a compound quaternized with a quaternizing agent. There is a need. When the tertiary amino group is neutralized with an acid, the acid is an organic acid such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, malic acid, malonic acid or adipic acid, and inorganic such as hydrochloric acid, phosphoric acid or nitric acid. Mention may be made of acids. These acids can be used alone or in combination of two or more. When the tertiary amino group is quaternized with a quaternizing agent, examples of the quaternizing agent include alkyl halides such as benzyl chloride and methyl chloride, and sulfate esters such as dimethyl sulfate and diethyl sulfate. Can do. These quaternizing agents can be used alone or in combination of two or more.

  The polyurethane resin (A) used in the present invention can be obtained by adding and reacting a polyisocyanate, a polycarbonate polyol, and a chain extender having a tertiary amino group in the molecule, followed by quaternization. Quaternized compounds can also be reacted as chain extenders.

  The polyester film of this invention needs to contain a cationic polymer antistatic agent (B) in the coating layer which has at least one side. Since the polyurethane resin (A) and the cationic polymer antistatic agent (B) are the same cationic polymer, intermolecular ionic aggregation does not occur in the coating agent in which both are mixed. In addition, since a cationic polymer is used as the antistatic agent, it is preferable in terms of better antistatic performance and better transparency of the coating film after stretching than the anionic or nonionic antistatic agent. Moreover, the transfer phenomenon which often becomes a problem with the low molecular weight antistatic agent does not occur.

  The cationic polymer antistatic agent (B) used in the present invention is preferably a polymer containing a quaternized nitrogen-containing unit as a repeating unit, and particularly represented by the following formula (I) or (II): A cationic polymer containing a unit having a pyrrolidinium ring in the main chain as a main repeating unit is preferable in that excellent antistatic performance can be obtained.

上記（Ｉ）式あるいは（II）式の構造において、Ｒ^１、Ｒ^２は、炭素数が１〜４のアルキル基もしくは水素であることが好ましく、これらは同一基でもよいし異なっていてもよい。またＲ^１、Ｒ^２のアルキル基は、ヒドロキシル基、アミド基、アミノ基、エーテル基で置換されていてもよい。さらに、Ｒ^１とＲ^２とが化学的に結合していて、環構造を有するものであってもよい。また、（Ｉ）式あるいは（II）式のＸ⁻は、ハロゲンイオン、硝酸イオン、メタンスルホン酸イオン、エタンスルホン酸イオン、モノメチル硫酸イオン、モノエチル硫酸イオン、トリフルオロ酢酸イオン、トリクロロ酢酸イオンの何れかである。

In the structure of the above formula (I) or (II), R ¹ and R ² are preferably an alkyl group having 1 to 4 carbon atoms or hydrogen, and these may be the same group or different. . Moreover, the alkyl group of R ¹ and R ² may be substituted with a hydroxyl group, an amide group, an amino group, or an ether group. Further, R ¹ and R ² may be chemically bonded and have a ring structure. In the formula (I) or (II), X ⁻ represents any one of a halogen ion, a nitrate ion, a methanesulfonate ion, an ethanesulfonate ion, a monomethyl sulfate ion, a monoethyl sulfate ion, a trifluoroacetate ion, and a trichloroacetate ion. It is.

Among the above-mentioned cationic polymers containing a unit having a pyrrolidinium ring in the main chain as a main repeating unit, particularly when the structure of formula (I) and X ⁻ is a chloride ion, the antistatic performance is excellent. In addition, the humidity dependency of the antistatic performance is small, which is preferable in that the decrease in the antistatic performance is reduced even under a low humidity. In addition, in the case where halogen ions cannot be used for easily chargeable adhesion, antistatic performance close to that of chlorine ions can be obtained by using methanesulfonic acid or monomethylsulfuric acid ions instead of chlorine ions. The polymer having the unit of the formula (I) as a repeating unit is polymerized by using the diallylammonium salt represented by the following formula (III) as a monomer and ring-closing by radical polymerization in a medium mainly containing water. It is obtained by. The polymer having the unit of the formula (II) as a repeating unit can be obtained by cyclopolymerizing the monomer of the formula (III) in a system using sulfur dioxide as a medium.

  In addition, when the polymer having the unit represented by the formula (I) or (II) as a repeating unit is a homopolymer composed of a single unit, better antistatic performance can be obtained. As will be described later, in order to improve the transparency of the coating layer when the polyester film is further stretched after the coating solution containing the cationic polymer is applied to the polyester film, it is expressed by the formula (I) or (II). 0.1 to 50 mol% of the unit to be prepared may be replaced with other copolymerizable components.

As the monomer component used as the copolymer component, one or more compounds having a carbon-carbon unsaturated bond copolymerizable with the diallylammonium salt of the formula (III) can be selected.

  These are specifically acrylic acid and its salts, methacrylic acid and its salts, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) Acrylamide, N-methylol (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, maleic acid and its salt or maleic anhydride, fumaric acid and its salt or fumaric anhydride, monoallylamine And quaternized products thereof, acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylidene chloride, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, dihydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, (meth) A Liloyloxyethyldialkylamine and its quaternary product, (meth) acryloyloxypropyldialkylamine and its quaternary product, (meth) acryloylaminoethyldialkylamine and its quaternary product, (meth) acryloylaminopropyldialkylamine and its quaternary product A quaternized product can be exemplified, but is not limited thereto.

  The cationic polymer antistatic agent (B) in the coating layer of the present invention is, for example, instead of a cationic polymer containing a pyrrolidinium ring as a repeating unit in the main chain represented by the above formula (I) or (II), for example ( It may be a cationic polymer having a unit represented by the formula (IV) or (V) as a repeating unit.

（IV）式あるいは（Ｖ）式の構造において、Ｒ^３、Ｒ^８はそれぞれ水素またはメチル基であり、Ｒ^４、Ｒ^９は、それぞれが炭素数２〜６のアルキル基であることが好ましく、またＲ^５、Ｒ^６、Ｒ^７、Ｒ^１０、Ｒ^１１、Ｒ^１２はメチル基あるいはヒドロキシエチル基もしくは水素であり、これらは同一基でもよいし異なっていてもよい。さらに（IV）式あるいは（Ｖ）式のＸ⁻は、ハロゲンイオン、硝酸イオン、メタンスルホン酸イオン、エタンスルホン酸イオン、モノメチル硫酸イオン、モノエチル硫酸イオン、トリフルオロ酢酸イオン、トリクロロ酢酸イオンの何れかである。

In the structure of formula (IV) or formula (V), R ³ and R ⁸ are each preferably hydrogen or a methyl group, and R ⁴ and R ⁹ are each preferably an alkyl group having 2 to 6 carbon atoms, R ⁵ , R ⁶ , R ⁷ , R ¹⁰ , R ¹¹ and R ¹² are a methyl group, a hydroxyethyl group or hydrogen, and these may be the same group or different. Further, X ⁻ in the formula (IV) or (V) is any one of a halogen ion, a nitrate ion, a methanesulfonate ion, an ethanesulfonate ion, a monomethyl sulfate ion, a monoethyl sulfate ion, a trifluoroacetate ion, and a trichloroacetate ion. It is.

  The cationic polymer having a unit represented by the formula (IV) or (V) as a repeating unit, for example, radically polymerizes an acrylic acid monomer or a methacrylic acid monomer corresponding to each unit in a medium mainly containing water. However, the present invention is not limited to this.

  The average molecular weight (number average molecular weight) of the cationic polymer used in the present invention is usually in the range of 1,000 to 500,000, more preferably 5,000 to 100,000. If the average molecular weight is less than 1000, it may cause the cationic polymer to transfer or block on the overlapping surface when the film is wound, and conversely if the average molecular weight exceeds 500,000, the coating solution containing this The viscosity of the film becomes high, and it may be difficult to uniformly apply to the film surface.

  The coating layer of the biaxially stretched polyester film in the present invention needs to contain the polyurethane resin (A) and the cationic polymer antistatic agent (B), but the weight ratio (A) / (B) is preferably in the range of 40/60 to 90/10, more preferably in the range of 50/50 to 80/20. When the weight ratio (A) / (B) is smaller than 40/60, the antistatic effect of the coating layer is sufficient, but the adhesiveness of the ink layer or the like tends to be insufficient. On the other hand, when it is larger than 90/10, the adhesion of the coating layer is sufficient, but the antistatic effect tends to be insufficient.

  The total weight of the polyurethane resin (A) and the cationic polymer antistatic agent (B) in the coating layer is usually 50% by weight or more, preferably 70% by weight or more, and is 100% at maximum. Also good.

  In addition to the polyurethane resin (A) and the cationic polymer antistatic agent (B), the coating layer of the biaxially stretched polyester film in the present invention is improved in heat resistance, moisture resistance, and blocking resistance of the coating film. For the purpose, a crosslinking agent can be added. In addition to melamine compounds, benzoguanamine compounds, urea compounds, acrylamide compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, oxazoline compounds, silanes in addition to methylolated or alkoxymethylolated compounds, urea compounds, or acrylamide compounds. It is preferable to contain at least one selected from coupling agent compounds, titanium coupling agent compounds, and the like. The amount of these crosslinking agents added is usually 1 to 50% by weight, preferably 3 to 40% by weight, based on the entire coating layer.

  In the biaxially stretched polyester film of the present invention, inorganic or organic fine particles can be added for the purpose of imparting slipperiness on the surface of the coating layer and improving blocking resistance. The fine particles include silica, alumina, titanium oxide, silica-alumina composite, silica-titanium oxide composite, cross-linked acrylic resin, cross-linked polystyrene resin and the like, or tin oxide, indium-tin composite oxide fine particles, antimony- It is preferable to contain at least one selected from conductive fine particles such as tin composite oxide fine particles. The fine particles to be added preferably have an average particle diameter of 5 to 200 nm, and the addition amount is also preferably 10% by weight or less based on the entire coating layer.

  A surfactant can be added to the coating layer of the biaxially stretched polyester film in the present invention. As this surfactant, a nonionic surfactant such as an acetyleglycol derivative substituted with an alkylene oxide addition polymer can be preferably used for the purpose of improving the wettability of the coating solution. Further, for the purpose of maintaining the transparency of the coating layer in the step of stretching the coating layer together with the film, a polyalkylene oxide adduct of glycerin or a polyalkylene oxide adduct of polyglycerin can be used.

  In addition to the above-described components, for example, an antifoaming agent, a thickening agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, and a pigment can be added to the coating layer as necessary. These additives may be used alone or in combination of two or more as necessary.

  Further, the coated layer of the laminated polyester film of the present invention needs to contain a polyurethane resin (A), but as a binder resin other than this, for example, a polyester resin, an acrylic resin, a polyurethane resin other than (A), etc. It is possible to coexist as long as the effects of the invention are not impaired.

The coated layer of the laminated polyester film in the present invention has a coating amount of 0.005 as a final dry film after being dried and solidified, or after being biaxially stretched or heat-set. to 1.0 g / ^{m 2,} more preferably in the range of 0.01 to 0.5 g / ^{m 2.} If the coating amount is less than 0.005 g / m ² , the antistatic performance and adhesiveness may be insufficient. If it exceeds 1.0 g / m ² , the antistatic performance and adhesiveness are no longer saturated. On the contrary, there is a tendency that harmful effects such as blocking are likely to occur.

  The coating layer of the laminated polyester film in the present invention is usually applied on the polyester film as a coating solution mainly containing water. The polyester film to be coated may be biaxially stretched in advance, but it is preferable to use a so-called in-line coating method in which the polyester film is stretched in at least one direction after coating and further heat-set. According to the in-line coating method, since the polyester film and the coating layer are usually heat-set at a high temperature of 200 ° C. or higher at the same time, the thermal crosslinking reaction of the coating layer proceeds sufficiently and the adhesion to the polyester film is further improved. .

  The coating solution is one of organic solvents compatible with water in an amount of usually 10% by weight or less, in addition to water, for the purpose of improving storage stability or improving coating properties and coating film properties. Two or more can be added. Examples of the organic solvent include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin, ethyl cellosolve, t-butyl cellosolve, ethers such as propylene glycol monomethyl ether and tetrahydrofuran, ketones such as acetone and methyl ethyl ketone, Examples include amines such as dimethylethanolamine and trimethanolamine, and amides such as N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

  As a method for applying the coating solution to the polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

  In addition, in order to improve the applicability | paintability to the film of a coating agent and adhesiveness, you may give a chemical process, a corona discharge process, a plasma process, etc. to a film before application | coating.

  Although the thickness of the polyester film of the present invention is not particularly limited, it is preferable that the film has suitability for processing as a film, and is usually in the range of 25 to 150 μm, preferably in the range of 38 to 125 μm. Is within. If the thickness is less than 25 μm, the card may not be elastic and desired concealment may not be ensured. On the other hand, when the thickness exceeds 150 μm, the cost per area increases.

  Next, although an example at the time of using biaxial stretching is demonstrated in detail, unless the summary of this invention is exceeded, this invention is not limited to the following examples.

  First, the raw material which comprises a polyester film is supplied to an extruder, and is extruded after melt-kneading. Next, the molten sheet extruded from the die is rapidly cooled and solidified on the rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature, thereby obtaining a substantially amorphous unoriented sheet. In this case, in order to improve the planar uniformity and cooling effect of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and in the present invention, an electrostatic application adhesion method is preferably employed. Next, the obtained sheet is stretched in a biaxial direction to form a film. First, the unstretched sheet is stretched under the conditions of a stretching temperature of usually 70 to 150 ° C., preferably 75 to 130 ° C., usually 2.0 to 6.0 times, preferably 2.5 to 5.0 times. Stretch in one direction (longitudinal direction). A roll and tenter type stretching machine can be used for such stretching. Here, as described above, it is preferable to provide a coating layer on the film after longitudinal stretching. Next, at a stretching temperature of usually 75 to 150 ° C., preferably 80 to 140 ° C., orthogonal to the first stage under the conditions of a stretching ratio of usually 2.0 to 6.0 times, preferably 2.5 to 5.0 times. The film is stretched in the direction (lateral direction) to obtain a biaxially oriented film. For such stretching, a tenter type stretching machine can be used.

  A method of performing the above-mentioned unidirectional stretching in two or more stages can also be adopted, but in this case as well, it is preferable that the final stretching ratio falls within the above-described range. Next, heat treatment in the tenter is usually performed at 180 to 240 ° C., preferably 200 to 235 ° C., for 1 second to 2 minutes. In this heat treatment step, relaxation of 0.1 to 20% in the transverse direction and / or the longitudinal direction is performed in the zone of the highest temperature of the heat treatment and / or the cooling zone immediately before the heat treatment outlet, in order to impart thermal dimensional stability. Is preferable.

  In the above, it is preferable to provide a coating layer on the film after longitudinal stretching. As a method of providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. However, in general, the post-coating process is performed at 70 to 280 ° C. for 3 to 200 seconds. It is preferable to perform heat treatment.

  Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. The laminated polyester film of the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples, unless the summary is exceeded. In addition, the various physical property in this invention, its measuring method, and a definition are as follows.

(1) Average particle size of white pigment (μm)
Using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation, the particle size was measured by a sedimentation method based on Stokes' resistance law. The average particle diameter was determined by using a value of 50% of integration (volume basis) in the equivalent spherical distribution of particles obtained by measurement.

(2) Intrinsic viscosity (dl / g)
A mixed solvent of phenol / tetrachloroethane: 50/50 (weight ratio) was added to 1 g of polyester at a ratio of 100 ml, and the mixture was measured at 30 ° C.

(3) Transmission density OD
A single film was measured using a Macbeth densitometer TD-904 type. (The higher this value, the higher the concealment.)

(4) Color tone (L *, a *, b *)
Using the Minolta spectrophotometer CM-3700d type, the film surface was measured by the reflection method. A C light source and a 2 ° field of view were used, and the color system was L * a * b * (CIE 1976).

(5) Surface resistivity (Ω)
A sample film was placed in a concentric circular electrode “16008A (trade name)” (inner electrode 50 mm, outer electrode 70 mm diameter) of Yokogawa Hewlett-Packard Co. in an atmosphere of 23 ° C. and 50% RH, and a voltage of 100 V was applied. The surface resistance of the film surface (the coated layer surface in the case of a coated film) was measured using a high resistance meter “4329A (trade name)” manufactured by the same company.
(6) Printability (ink adhesion) of the film surface (coated layer surface for coated film)
Using indigo-colored serocolor printing ink (“CCST39” manufactured by Toyo Ink Manufacturing Co., Ltd.), apply to the surface of the X layer so that the coating thickness after printing is 1.5 μm, and dry with hot air at 80 ° C. for 1 minute. A film for evaluation is used. Make a cross cut (100 squares of 4 mm ² ) on the surface of the printing ink, and apply Nichiban cello tape (registered trademark) 24 mm wide on the surface of the ink surface to make it 7 cm long so that no air bubbles enter. Then, 3 kg of a manual load roll is reciprocated to make it adhere to the top. Next, the evaluation film is fixed on the substrate arranged in the vertical direction, and a weight of 500 g is tied to the upper end of the tape with a 45 cm thread. Then, the weight is dropped from the same height as the upper end of the tape. After the weight naturally falls by a distance of 45 cm, a peel test in the 180 ° direction is started.
Evaluation 5: Ink does not peel at all Evaluation 4: Less than 10% of ink peels to the tape side Evaluation 3: 10 to 50% of ink peels to the tape side Evaluation 2: More than 50% of ink peels to the tape side Evaluating 1: All ink peels to the tape side. In the above evaluation, 5 and 4 were determined to be acceptable.

Comparative Example 1:
The main raw material is polyethylene terephthalate having IV = 0.66 and no particles, 15% by weight of anatase-type titanium dioxide having a particle size of 0.3 μm, 30 ppm of carbon black having a primary particle size of 0.01 μm, and an average particle size of 4.2 μm Polyethylene terephthalate raw material (A) mixed with 0.4% by weight of amorphous silica was added to a twin screw extruder with a vent, melted and kneaded at 270 ° C., and the resulting melt was extruded into a slit shape. An unstretched sheet was obtained by closely contacting and cooling on a cooling drum at 30 ° C. by an electrostatic application method. Next, the unstretched sheet was stretched 3.0 times at 85 ° C. in the longitudinal direction, and further stretched 4.5 times at 115 ° C. in the transverse direction, and the temperature was raised stepwise, followed by heat treatment at 230 ° C. for 5 seconds. Next, under a 190 ° C. atmosphere, 1% relaxation treatment (to narrow the tenter rail width) was performed in the width direction. Finally, a biaxially oriented film having a film thickness of 45 μm was obtained. Since the film has a high surface resistivity, the film is easily charged with static electricity and easily adsorbs foreign substances in the environment.

Examples 1, 2, 3 and Comparative Examples 2, 3, 4
In Comparative Example 1, the aqueous coating solution shown in the attached table was applied to the surface of the film after longitudinal stretching by the bar coating method. Other than that was carried out similarly, and the biaxially oriented film with a film thickness of 45 micrometers was finally obtained.

Comparative Example 5
In Example 1, the coating liquid was blended using an anionic aqueous polyurethane having a polycarbonate polyol structure (trade name Takelac W-6010, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) instead of the polyurethane resin A1. The coating solution was precipitated immediately after preparation, and could not be applied to the film.

Example 4
A biaxially oriented film having a film thickness of 45 μm was finally obtained in the same manner as in Example 1 except that the amount of carbon black added was 15 ppm.

Example 5
A biaxially oriented film having a film thickness of 45 μm was finally obtained in the same manner as in Example 1, except that the amount of carbon black added was 60 ppm.

Comparative Example 6:
A biaxially oriented film having a film thickness of 45 μm was finally obtained in the same manner as in Example 1 except that carbon black was not added.

Comparative Example 7:
A biaxially oriented film having a film thickness of 45 μm was finally obtained in the same manner as in Example 1 except that the amount of carbon black added was 120 ppm.

  Tables 1 and 2 below show the film composition, the composition of the coating layer, and the evaluation results of the polyester film (having the coating layer).

The compounds constituting each coating layer are as follows.
-Polyurethane resin A1:
76.7 parts by weight of a polycarbonate polyol (number average molecular weight of about 1,000 in GPC) obtained by reaction of 1,6-hexanediol with diethyl carbonate, polyethylene glycol (trade name PEG600, molecular weight 600, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 6.4 parts by weight, 2.0 parts by weight of trimethylolpropane, 19.9 parts by weight of N-methyl-N, N-diethanolamine, 86.7 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, 87 parts by weight of MEK was placed in a reaction vessel and reacted at 70 to 75 ° C. to obtain a urethane prepolymer. To this urethane prepolymer, 16.8 parts by weight of dimethyl sulfate was added and reacted at 50 to 60 ° C. to obtain a cationic urethane polymer. After 623 parts by weight of water was added and emulsified, MEK was recovered to obtain an aqueous dispersion of polyurethane resin A1.

-Polyurethane resin A2:
300 parts by weight of polytetramethylene glycol (Mitsubishi Chemical Co., Ltd., trade name PTMG1000, molecular weight 1000), 6.0 parts by weight of polyethylene glycol (Daiichi Kogyo Seiyaku Co., Ltd., trade name PEG600, molecular weight 600), trimethylolpropane 2.5 parts by weight, 16.0 parts by weight of N-methyl-N, N-diethanolamine, 71.7 parts by weight of isophorone diisocyanate, and 89 parts by weight of MEK are placed in a reaction vessel and reacted at 70 to 75 ° C. A urethane prepolymer was obtained. To this urethane prepolymer, 13.4 parts by weight of dimethyl sulfate was added and reacted at 50-60 ° C. to obtain a cationic urethane polymer. After adding 457 weight part of water to this and emulsifying, MEK was collect | recovered and the water dispersion of polyurethane resin A2 was obtained.

Cationic polymer antistatic agent B: quaternary ammonium salt-containing cationic polymer using diallyldimethylammonium chloride (pyrrolidinium ring-containing polymer of formula (I)) average molecular weight of about 30,000

-Crosslinking agent C: Copolymer-type crosslinking agent aqueous solution of 2-isopropenyl-2-oxazoline and acrylic monomer (trade name Epocros WS-500, manufactured by Nippon Shokubai Co., Ltd.), oxazoline group amount = 4.5 mmol / g

Fine particles D: colloidal silica fine particles (average particle size 0.07 μm)
In the comparative example 2, since the polyurethane resin which does not contain polycarbonate polyol is used for the application layer, adhesiveness with an ink layer was inadequate. In Comparative Example 3, since the polyurethane resin (A) was not present in the coating layer, adhesion with the ink layer was not exhibited. In Comparative Example 4, since the coating layer did not contain the cationic polymer antistatic agent (B), the antistatic performance was insufficient. In Comparative Example 5, since the polyurethane resin used does not contain a compound obtained by quaternizing the tertiary amino group of the chain extender having a tertiary amino group in the molecule, the cationic polymer antistatic agent and A precipitate was formed by ion agglomeration.

  In Table 1, the ratio (A) / (B) represents the polyurethane resin (A) / cationic polymer antistatic agent (B) (weight ratio) in the coating layer.

  The polyester film of the present invention can be suitably used as, for example, a film for an IC card sheet.

Claims (1)

At least one surface of a white polyester film composed of a single layer containing 10 to 100 ppm of black pigment has a coating layer having a surface resistivity of 1 × 10 ⁶ to 1 × 10 ¹² Ω, and the coating layer is A polyurethane resin containing as a constituent component a compound obtained by quaternizing a tertiary amino group of a chain extender having a tertiary amino group in the molecule and a polycarbonate polyol, and a cationic polymer antistatic agent, An antistatic white polyester film having a transmission density OD of 0.9 or more and a hue L * value of 91 or more.