AU712807B2

AU712807B2 - Biaxially oriented adhesive polyester film and production process therefor

Info

Publication number: AU712807B2
Application number: AU67965/96A
Authority: AU
Inventors: Masayuki Fukuda; Shinichiro Okada
Original assignee: Teijin Ltd
Current assignee: Teijin Ltd
Priority date: 1995-12-19
Filing date: 1996-10-02
Publication date: 1999-11-18
Anticipated expiration: 2016-10-02
Also published as: AU6796596A; KR100232386B1; JPH09169857A; JP3286139B2

Description

AUSTRALIA

Patent Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: Names(s) of Applicant(s): TEIJIN LIMITED Actual Inventor(s): Shinichiro Okada Masayuki Fukuda Address for service is: a 9 9 999.

9 PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Victoria 3000, Australia Complete Specification for the invention entitled: BIAXIALLY ORIENTED ADHESIVE POLYESTER FILM AND PRODUCTION PROCESS

THEREFOR

Our Ref: 466757 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 2210x 1A BIAXIALLY ORIENTED ADHESIVE POLYESTER FILM AND PRODUCTION PROCESS THEREFOR Detailed Description of the Invention This invention relates to a biaxially oriented adhesive polyester film and a production process therefor.

More specifically, it relates to a biaxially oriented adhesive polyester film having excellent adhesive and antistatic properties and non-transfer property of a magnetic layer; and to a process for the production thereof.

Although a white film of an aromatic polyester containing a white pigment such as titanium oxide is widely used in a magnetic card, printing material, etc., it has such defects that it easily generates static electricity, is liable to cause various problems in film formation and fabricating steps and at the time of using its products and has poor adhesion to a magnetic coating and printing ink, all of which are common problems to plastic films.

A white polyester thick film is used particularly in magnetic cards such as telephone cards, prepaid cards, etc., but it has drawbacks in its production and fabricating steps and a problem with its antistatic 25 property and adhesion to UV ink and magnetic coatings as a final product, and hence, application of a primer has been also proposed.

Heretofore, there have been proposed methods for forming in advance a primer layer (coating layer) of a synthetic resin on the surface of a film in order to improve the adhesion of a polyester film.

oo JP-A 6-124651 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a magnetic recording material which comprises .35 a polyester film formed by coating at least one side of a polyester film mainly composed of polyethylene terephthalate with a water-soluble or -dispersible polyester resin having a sulfonate group and a watersoluble or -dispersible acrylic resin and a magnetic layer formed on the coated surface of the film.

JP-A 5-41655 discloses a biaxially oriented polyester film prepared by coating at least one side of a polyester film with a coating agent containing a vinyl resin composed of styrene sulfonic acid or a salt thereof and stretching the film.

JP-A 6-157790 discloses an adhesive white polyester film having an adhesive coating film having a thickness (dry) of 0.01 to 5 pm and formed by coating at least one side of a white aromatic polyester film containing a white pigment and having a thickness of not less than 20 pm with a coating solution containing a composition which mainly comprises 5 to 80 by weight of an aromatic polyester resin having a secondary transition point of 60 to 2000C, 5 to 80 by weight of an acrylic copolymer and 1 to 30 by weight of a substance having a sulfonate group in the molecule.

This publication teaches that the above white polyester film is excellent in adhesion, blocking resistance and antistatic properties. However, the publication is silent about the physical conditions in the coating solution of the constituents of the coating solution.

t 25 JP-A 7-132581 teaches an antistatic adhesive film for a magnetic card, which comprises a white polyester film having a coating film of 0.5 to 2 pm in thickness formed on at least one side thereof, the coating film being formed by coating a stretchable white polyester film 30 with an aqueous solution comprising as main components (A) 20 to 60 by weight of a polyester having a secondary transition point of 40 to 95 0 C, 10 to 60 by weight of a self-crosslinking acrylic resin and 10 to 50 by ."weight of a polymer of an unsaturated monomer containing 35 30 mol% or more of a polymer unit represented by the following formula: 3

R

1

R

2 S03x wherein R1 and R2 are each H or CH3 and X is an alkali metal, in the molecule, drying, stretching and heat setting.

This publication teaches that this film is excellent in antistatic properties and adhesion to a magnetic coating and printing ink. However, the publication is silent about the physical conditions in the coating solution of the constituents of the coating solution.

When a primer layer formed by these methods is coated on one side with a magnetic coating in the fabricating step of a magnetic card and aged in a rolled state, however, a transfer or blocking of part of a magnetic layer (magnetic recording layer) to the primer layer on the opposite side occurs, thereby deteriorating production efficiency frequently. Therefore, it is difficult to achieve both adhesion to a magnetic layer and 20 blocking resistance at the same time. Further, generally speaking, the film is easily charged with static electricity and is liable to cause various troubles in Po film formation and fabricating steps and at the time of using as a product.

It is therefore an object of the invention to provide a process for producing a biaxially oriented a. adhesive polyester film which has excellent adhesive and antistatic properties and a non-transfer property of the magnetic layer.

It is another object of the invention to provide a biaxially oriented adhesive polyester film having excellent adhesive and antistatic properties and a nontransfer property of the magnetic layer, which is produced by the above process of the present invention.

It is still another object of the invention to provide a polyester film having an information function, which has a magnetic layer formed on the biaxially oriented adhesive polyester film of the invention.

It is a further object of the invention to provide a base film for use in the biaxially oriented adhesive polyester film of the invention.

The above and other objects and advantages of the present invention will become apparent from the following description.

According to the present invention, the above objects and advantages can attained, firstly, by a process for producing a biaxially oriented adhesive polyester film which comprises the steps of: forming a thin film (coating film) of an aqueous dispersion by applying onto both surfaces of an unoriented or stretched film of an aromatic polyester containing 5 to 20 by weight of a white pigment the aqueous dispersion containing 5 to 70 by weight of fine particles having an average particle diameter of not more than 100 nm of an aromatic copolyester having a secondary transition point of 50 to 120 0 C, 5 to 70 by weight of fine particles 25 having an average particle diameter of not more than 150 "nm of an acrylic copolymer having a secondary transition point of 50 to 1200C, and 3 to 50 by weight of a watersoluble organic sulfonate; and while or after the thin film of the aqueous 30 dispersion is dried, stretching the film biaxially or monoaxially to form a biaxially oriented film having an adhesive coating film.

The base film used in the present invention oe oI S" comprises an aromatic polyester containing 5 to 20 by 35 weight of a white pigment. Therefore, the base film may ooo be referred to as "white film" or "white polyester film" hereinafter.

In the present invention, the aromatic polyester constituting the white film is a crystalline linear saturated polyester produced from an aromatic dibasic acid or an ester forming derivative thereof and a diol or an ester forming derivative thereof. Specific examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly(1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalene dicarboxylate, copolymers containing as a main component (not less than 50 mol%) ethylene terephthalate, ethylene isophthalate, butylene terephthalate, 1,4-cyclohexylenedimethylene terephthalate or ethylene-2,6-naphthalene dicarboxylate, and homopolymers, copolymers and blends thereof containing a small amount of other resin.

Of these, polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate are particularly preferred.

Preferred examples of the white pigment contained in these aromatic polyesters include titanium oxide and barium sulfate. They may be used alone or in combination.

The white pigment is contained in an amount of 5 to 20 by weight, preferably 6 to 15 by weight based on the total weight of the aromatic polyester and the white 25 pigment.

The aromatic polyester may contain an inorganic afiller such as silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin and talc; an organic filler such as a crosslinked polystyrene resin, 30 crosslinked acrylic resin, urea resin and melamine resin; other resin such as polyethylene, polypropylene, ethylene*propylene copolymer and olefinic ionomer; antioxidant, ultraviolet absorber, fluorescent brightener and the like as required.

S 35 The above aromatic polyester containing the white pigment preferably exhibits a light transmittance of not more than 10 more preferably not more than 5 In the present invention, the base film formed from an aromatic polyester containing a white pigment is an unoriented film or monoaxially oriented film. The unoriented film preferably has a thickness of at least 200 pm and the monoaxially oriented film preferably has a thickness of at least 70 pm.

In the step of the present invention, the aqueous dispersion containing a polymer composition is applied onto the surface of the base film to form a thin film of the dispersion.

The polymer composition constituting the aqueous dispersion contains an aromatic copolyester having a secondary transition point of 50 to 120 0 C, an acrylic copolymer having a secondary transition point of 50 to 120 0 C and a water-soluble organic sulfonate.

The aromatic copolyester having a secondary transition point of 50 to 1200C preferably contains an aromatic dicarboxylic acid in an amount of at least mol%, more preferably at least 65 mol%, particularly preferably at least 80 mol% of the whole acid component.

The acid components constituting the aromatic copolyester include, for example, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 25 adipic acid, sebacic acid, phenylindanedicarboxylic acid, dimer acid and the like. These components may be used alone or in combination of two or more. Of these, terephthalic acid, isophthalic acid and 2,6naphthalenedicarboxylic acid are particularly preferred.

:30 Further, a small amount of an unsaturated polybasic acid such as maleic acid, fumaric acid and itaconic acid or a hydroxycarboxylic acid such as p-hydroxybenzoic acid and p-(P-hydroxyethoxy)benzoic acid may be used in combination with these components. The proportion of the unsaturated 35 polybasic acid component or the hydroxycarboxylic acid component is 10 mol% at the most, preferably not more than mol%, of the whole component.

The polyol components constituting the aromatic copolyester include, for example, ethylene glycol, 1,4butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4cyclohexanedimethanol, xylylene glycol, dimethylolpropionic acid, glycerine, trimethylolpropane, poly(ethyleneoxy)glycol, poly(tetramethyleneoxy)glycol and an adduct of bisphenol A with ethylene oxide and an adduct of bisphenol A with propylene oxide, which are represented by the following formulas: H3 H (OCH 2

CH

2 )n-O-ph- -ph-O- (CHCH 20) m-H H(O HCH 2 )n-O-ph -ph-O-(CH 2 HO )-H CH3 CH3 CH3 wherein n m is 2 to 10 and ph is a phenylene group.

They may be used alone or in combination of two or more.

.l Of these polyol components, ethylene glycol, an adduct of bisphenol A with ethylene oxide, an adduct of bisphenol A with propylene oxide, and 1,4-butanediol are 20 preferred, and ethylene glycol and an adduct of bisphenol A with ethylene oxide and an adduct of bisphenol A with propylene oxide are more preferred.

Further, the aromatic copolyester is preferably copolymerized with a small amount of a compound having a 25 sulfonate group or a compound having a carboxylate group to improve dispersibility.

Illustrative examples of the compound having a sulfonate group include sulfonic acid alkali metal saltand sulfonic acid amine salt-based compounds such as sodium sulfoisophthalic acid, 5-ammonium sulfoisophthalic acid, 4-sodium sulfoisophthalic acid, 4-methylammonium sulfoisophthalic acid, 2-sodium sulfoisophthalic acid, pottasium sulfoisophthalic acid, 4-pottasium sulfoisophthalic acid, 2-pottasium sulfoisophthalic acid and sodium sulfosuccinic acid.

Illustrative examples of the compound which provides a carboxylate group to the aromatic copolyester include trimellitic anhydride, trimellitic acid, pyromellitic anhydride, pyromellitic acid, trimesic acid, cyclobutane tetracarboxylic acid, dimethylolpropionic acid and monoalkali metal salts thereof. A free carboxyl group formed in the polymer chain is allowed to react with an alkali metal compound or an amine compound to be converted into a carboxylate group.

As the aromatic copolyester may be used a modified polyester copolymer such as a block polymer or graft polymer prepared by modifying the above aromatic copolyester with an acrylic, polyurethane, silicone, epoxy or phenolic resin.

The aromatic copolyester used in the present invention preferably contains an aromatic dicarboxylic acid component having a sulfonate group in an amount of 0.05 to 6 mol% of the whole component.

The aromatic copolyester in the present invention can be produced by a polyester production technique which 25 has been used or known conventionally. For instance, the aromatic copolyester can be produced by forming a monomer or oligomer by allowing 2,6-naphthalenedicarboxylic acid or an ester forming derivative thereof (particularly dimethyl ester), isophthalic acid or an ester forming 30 derivative thereof (particularly dimethyl ester) and trimellitic anhydride to react with ethylene glycol and an adduct of bisphenol A with propylene oxide, and then polycondensing the monomer or oligomer in vacuo to produce a. a polyester having a predetermined intrinsic viscosity 35 (preferably 0.2 to 0.8, measured at 35 0 C in ochlorophenol). At this time, a catalyst for promoting the reaction, such as an esterification, ester exchange reaction or polycondensation catalyst, is preferably used and various additives such as a stabilizer may be added.

The aromatic copolyester has a secondary transition point (Tg) of 50 to 120 0 C. When Tg is lower than 50 0

C,

the transfer of the magnetic layer is liable to occur.

The preferred Tg is in the range of 60 to 120 0

C.

In the present invention, the aromatic copolyester is dispersed in the aqueous dispersion as fine particles having an average particle diameter of not more than 100 nm. When the average particle diameter is more than 100 nm, the transfer of the magnetic layer is liable to occur.

The preferred average particle diameter is 5 to 80 nm.

The term "average particle diameter" as used herein denotes a measurement value obtained by measuring the aqueous dispersion using a fine particle analyzer (NICOMP MODEL 270 manufactured by Pacific Scientific Co.).

The acrylic copolymer having a secondary transition point of 50 to 1200C may contain, as an acrylic component, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, soda acrylate, ammonium acrylate, 2-hydroxyethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, soda methacrylate, ammonium methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, acryl methacrylate, sodium 25 methallyl sulfonate, acrylamide, methacrylamide or Nmethylolmethacrylamide.

The acrylic copolymer may be used in combination with other unsaturated monomer such as styrene, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl chloride, 30 vinylidene chloride, divinyl benzene, sodium vinyl sulfonate or sodium styrene sulfonate.

Of these, the acrylic copolymer containing a polymer unit of a Cl C 4 alkyl(meth)acrylate as a constituent is preferred. Preferably, the acrylic copolymer does not 35 contain a polymer unit having a sulfonate group.

As the acrylic copolymer may be also used a modified acrylic copolymer such as a block polymer or graft polymer prepared by modifying the above acrylic copolymer with a polyester, polyurethane, silicone, epoxy or phenolic resin, or the like.

This acrylic copolymer has a Tg of 50 to 120 0

C.

When Tg is lower than 500C, the transfer of the magnetic layer is liable to occur. The preferred Tg is in the range of 60 to 120 0

C.

In the present invention, the acrylic copolymer is dispersed in the aqueous dispersion as fine particles having an average particle diameter of not more than 150 nm. When the average particle diameter is more than 150 nm, disadvantageously, the transfer of the magnetic layer is liable to occur. The average particle diameter is measured by the same manner as described above.

The fine particles of the acrylic copolymer preferably has an average particle diameter of 5 to 120 nm.

The organic sulfonate which is another component contained in the aqueous dispersion is water-soluble.

Illustrative examples of the organic sulfonate include low-molecular weight compounds such as metal salts of alkyl sulfonic acid, alkyl benzene sulfonic acid and alkyl diphenyl ether disulfonic acid; polymers such as polyester copolymers having a sulfonic acid metal salt group, acryl copolymers and vinyl copolymers; and the like. They may be used alone or in combination of two or more.

Of these, polymers having a sulfonic acid salt group and a number average molecular weight of 1,000 to 1,000,000 are preferred and particularly polymers comprising polymer units having a sulfonate group in an 30 amount of 30 to 100 mol% and a number average molecular weight of 1,000 to 1,000,000 are advantageously used.

In the present invention, the above aqueous dispersion comprises 5 to 70 by weight, preferably 10 to 60 by weight, of aromatic copolyester fine particles, 35 to 70 by weight, preferably 10 to 60 by weight, of acrylic copolymer fine particles and 3 to 50 by weight, preferably 10 to 40 by weight of a water-soluble organic 11 sulfonate based on the total weight of the aromatic copolyester fine particles, acrylic copolymer fine particles and water-soluble organic sulfonate.

When the amount of the aromatic copolyester fine particles is more than 70 by weight, the adhesion of the thin film to printing ink will be insufficient, whereas when the amount is less than 5 by weight, the adhesion of the formed adhesive thin film to the base film will be insufficient disadvantageously. When the proportion of the water-soluble organic sulfonate is less than 3 by weight, the antistatic properties will be unsatisfactory, whereas when the proportion is more than 50 the adhesion of the formed adhesive thin film to the base film will be insufficient, which are disadvantageously.

In the present invention, the above aqueous dispersion may contain a wetting agent to improve its wettability to the base film. The wetting agent is preferably selected from anionic surfactants, betaine type surfactants and nonionic surfactants. Illustrative examples of the wetting agent include polyethylene oxide*polypropylene oxide block copolymer, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, Spolyoxyethylene aliphatic acid ester, sorbitan aliphatic acid ester, glycerine aliphatic acid ester, aliphatic acid 25 metal soap, alkyl sulfonate, alkyl sulfate, alkyl benzene sulfonate, alkyldiphenyl ether disulfonate, alkyl sulfosuccinate and the like.

The wetting agent is preferably contained in an amount of 2 to 30 by weight, more preferably 3 to 20 by weight, of the total weight of the solid contents. The proportion is desirably such that the surface tension of the aqueous dispersion be preferably be not more than J: dyne/cm, more preferably not more than 40 dyne/cm.

To improve stability and applicability, the aqueous 35 dispersion may contain a water-miscible solvent such as methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, methanol, ethanol, n-propanol, isopropanol and the like. They may be used alone or in combination of two or more.

The aqueous dispersion may also contain an antistatic agent within limits not prejudicial to the object of the present invention. Illustrative examples of the antistatic agent include ion conductive compounds such as acrylic polymers having a quaternary ammonium salt group, phosphate compounds and phosphoric ester compounds; metal oxides such as tin oxide and antimony oxide; metal alkoxides such as alkoxysilane, alkoxytitanium and alkoxyzirconium and derivatives thereof; coated carbon; and coated silica. They may be used alone or in combination of two or more.

Further, the aqueous dispersion may contain other additives such as an ultraviolet absorber, antioxidant, pigment, organic filler, inorganic filler, lubricant, anti-blocking agent and crosslinking agent such as melamine, epoxy or aziridine within limits not prejudicial to the object of the present invention.

The solid content concentration of the above aqueous dispersion in the present invention is preferably 3 to by weight.

a boe In the first step of the present invention, the .above aqueous dispersion is applied onto both surfaces of 25 a base film whose crystal orientation is not completed yet, that is, an unoriented base film or monoaxially oriented base film to form a thin film of the aqueous dispersion on the film.

As a method for applying the aqueous dispersion to 30 the base film may be used roll coating, gravure coating, microgravure coating, reverse coating, roll brush coating, spray coating, air knife coating, impregnation and curtain coating, which may be used alone or in combination.

The amount of the aqueous dispersion to be applied 35 is preferably 0.5 to 50 g, more preferably 5 to 40 g, per m 2 of the traveling film. The thickness of the final dried thin film (coating film) is preferably 0.02 to 2 ym, more preferably 0.05 to 1 pm. When the thickness of the coating film is less than 0.02 pm, sufficient antistatic properties can hardly be obtained, whereas when the thickness is more than 2 pm, slipperiness deteriorates disadvantageously.

In the second step of the present invention, the base film having a drying or dried thin film obtained during or after drying of the thin film of the aqueous dispersion formed on the base film is oriented biaxially or monoaxially to form a biaxially oriented film having a dried adhesive coating film.

The step is carried out advantageously by preheating a film having the thin film of the aqueous dispersion and thermally stretching the film in succession.

The preheating is preferably carried out at a temperature of about 60 to 130*C. The stretching is preferably carried out in a temperature range of from 5 0

C

higher than the secondary transition temperature of the aromatic polyester of the base film to 70 0 C higher than that of the aromatic polyester of the base film.

This stretching is advantageously carried out to achieve a final area stretch ratio of 7.8 to 13.5 times and each of stretch ratios in biaxial directions of at least 2.8 times.

25 After the step the film is preferably thermally set at a range from a temperature 70 0 C higher than the C secondary transition temperature of the aromatic polyester containing the white pigment to a temperature lower than the melting point.

Thus, according to the present invention, a biaxially oriented adhesive polyester film can be obtained by the above process of the present invention. The base film of the biaxially oriented adhesive polyester film of a the present invention is a biaxially oriented base film which satisfies the following expression: C C M I 0.15 I(l110)/(100) 2 0.08 wherein I(110) is an X-ray diffraction strength in a surface (110) in parallel to the film surface and I(100) is an X-ray diffraction strength in a surface (100) in parallel to the film surface.

The base film and the biaxially oriented adhesive polyester film having the base film of the present invention have excellent folding endurance and are hardly broken or cracked.

When the X-ray diffraction strength ratio is less than 0.08, folding endurance will be insufficient as a magnetic card during the fabrication of a magnetic card with the result that the produced magnetic card may be broken or cracked. Therefore, the film is unsatisfactory in terms of shelf stability and durability as a magnetic card. On the other hand, when the X-ray diffraction strength ratio is more than 0.15, the film will be insufficient in rigidity and so may be deformed during fabricating or give an adverse effect on a reader/writer for a magnetic card.

Therefore, according to the present invention, there is also provided a biaxially oriented aromatic polyester film formed from an aromatic polyester containing 5 to 2 20 by weight of a white pigment and having a thickness 25 of 20 to 500 ym and an X-ray diffraction strength ratio that satisfies the following expression: 0.15 Z I(l10)/I(100) 2 0.08 1.

wherein I(110) is an X-ray diffraction strength in a surface (110) in parallel to the film surface and 30 I(100) is an X-ray diffraction strength in a surface (100) in parallel to the film surface.

*44 *A magnetic recording layer and a printing ink layer may be formed on the adhesive coating film on both P •surfaces of the biaxially oriented adhesive polyester film 35 of the present invention.

S" Therefore, according to the present invention, there are further provided a polyester film having an information function which comprises at least one of a magnetic recording layer and a printing ink layer present on at least part of either one of the adhesive coating films on both surfaces of the biaxially oriented adhesive polyester film of the present invention and a polyester film having an information function which comprises a magnetic recording layer present mainly on one adhesive coating film surface and a printing ink layer present mainly on the other adhesive coating film surface on both surfaces of the biaxially oriented adhesive polyester film of the present invention.

The magnetic recording layer contains, for example, magnetic powders such as y-Fe 2 0 3 Cr02, Co-y-Fe203, Fe30 4 BaO'6FeO 3 or metal magnetic powders, a binder such as vinyl acetate, polyvinylidene chloride, vinyl resin such as PVC, acrylic resin, rubber-based resin such as acrylonitrile/butadiene copolymer, fibrin such as nitrocellulose, epoxy resin, phenolic resin or polyurethane resin, and as required, a dispersant, lubricant, stabilizer, antistatic agent such as carbon, a plasticizer and the like.

The printing ink layer is not particularly limited, but preferably formed from ultraviolet curing printing ink, electron beam curing ink, thermosensitive recording ink or 25 the like.

i Examples are given to further illustrate the present invention. Characteristic properties in these examples were obtained by the following methods.

30 1. Transfer property of magnetic layer *4*O The following coating for evaluation is applied to a sample film with a Meyer rod so as to have a thickness 4 5* after drying of about 5 pm, and dried at 1000C for 3 4.

9 0 minutes. This magnetic surface is laid upon a primer 35 coated surface of another sample and the resulting s o r S: laminate is aged for 17 hours under the conditions of a pressure of 50 kg/cm 2 and a temperature of 50C. The

I

coloring of the primer coated surface when it is separated is evaluated visually. The surface without change is evaluated as O, slightly colored as A, and completely colored as X.

[Coating for evaluation] parts by weight of an urethane resin (Nipollan 2304 manufactured by Nippon Polyurethane Industry Co.Ltd.), parts by weight of a vinyl chloride-vinyl acetate resin (Slec A manufactured by Sekisui Plastic Co. Ltd.), 1 part by weight of a dispersant (Recion P manufactured by Riken Vitamin KK) and 500 parts by weight of a magnetizing agent (CTX-860 manufactured by Toda Chemical Co.Ltd.), all in terms of solid content, are dissolved in a methyl ethyl ketone/toluene/cyclohexanone mixture solvent to prepare a solution having a solid content of 40 and dispersed by a sand grinder for 2 hours. Thereafter, 25 parts by weight (as solid content) of a crosslinking agent (Colonate L manufactured by Nippon Polyurethane Industry Co., Ltd.) is added to the resulting dispersion and stirred well to produce a magnetic coating.

2. Adhesive force of magnetic coating The above coating for evaluation is applied to a sample film with a Meyer rod to a thickness after drying of about 5 pm and dried at 100 0 C for 3 minutes.

0 25 Thereafter, the coating film is aged at 60 0 C for 24 hours and a 12.7 mm wide, 15 cm long piece of Scotch Tape No.

V.

o 600 (manufactured by 3M) is affixed to the sample film so that there is no air bubbles between the tape and the film.

This tape was rolled with a manual load roll described in 30 JIS C2701 (1975) to be firmly affixed to the film, and is cut out to a tape width. This sample is measured for its strength when it is peeled off at 1800 3. Adhesive force of UV ink a Ultraviolet curing ink (Flash Dry FD Carton P 35 Magenta manufactured by Toyo Ink Manufacturing Co.Ltd.) is printed on a sample film by an RI tester (manufactured by KK Akira Seisakusho) and is cured by an moderatepressure mercury lamp (80 W/cm, single lamp type, manufactured by Japan Storage Battery Co. Ltd.) UV curing device to form an 4 pm thick UV ink layer. A 15 cm long piece of Cellotape (18 mm wide, manufactured by Nichiban Company Limited) is affixed to this UV ink layer and a 2 kg manual load roll is rolled over this tape to provide a certain load. One end of the tape is peeled off at an angle of 900 while the film is fixed to evaluate its peel adhesive force. The adhesion is evaluated based on the following five grades.

The ink layer is not peeled off at all.

4: Less than 3 of the ink layer is peeled off.

3: 3 to 10 of the ink layer is peeled off.

2: 10 to 30 of the ink layer is peeled off.

1: More than 30 of the ink layer is peeled off.

4. Antistatic properties The antistatic properties are obtained by measuring the surface resistivity (Q/square) of a sample film 1 minute after it is applied with a voltage of 500 V at a measurement temperature of 23 0 C and humidity of 65 using a resistivity measuring instrument manufactured by Takeda Riken Co. The surface resistivity is preferably not more than 1 x 1011 Q/square.

5. Blocking resistance 25 A laminate prepared by laminating together the primer coated surface and another primer coated surface of o a polyester film is cut into a 5 cm x 10 cm square piece which is then applied with a pressure of 6 kg/cm 2 in an atmosphere of 50 0 C and 70 RH for 17 hours. Then, this ;30 cm-wide piece is measured for its peel strength (peel rate of 100 mm/min.). The peel strength is evaluated as follows.

not more than 4 g/5 cm: 0 4 to 10 g/5 cm: A 35 more than 10 g/5 cm: X 6. X-ray diffraction strength ratio 18 Using CuK-a as an X-ray source, the X-ray diffraction strength ratio is measured at a divergence slit of 1/20, a diffusion slit of 1/20, a light receiving slit of 0.15 mm, and a scan speed of 1,000 0 /min. The ratio I(110)/I(100) [I(110): X-ray diffraction strength in a surface (110) in parallel to the film surface, I(100): X-ray diffraction strength in a surface (100) in parallel to the film surface] is measured in accordance with a multiplex peel separation method using a Pseudo Voight peel model.

7. Impact strength In accordance with JIS x6311, a film is placed on a horizontal plate and a 500 g rigid ball is dropped onto the film from a height of 30 cm to check the existence of breakage or cracks. (absence: 0 presence: X) 8. Secondary transition point The secondary transition point is measured using the SSC/580DS type DSC of Seiko Instruments Inc. An about mg sample is sealed in an aluminum holder, heated up to 2000C by DSC, then cooled gradually to 0°C, and thereafter started a measurement for its secondary transition point.

The temperature is elevated to 200 0 C at a rate of 10 0 C/min.

and Tg is obtained by a change in an amount of heat.

9. Average particle diameter 25 An aqueous solution having a particle concentration of 200 ppm is used as a sample, and a particle diameter of particles which account for 50 by weight of the total is obtained from equivalent spherical diameters of all the particles obtained by an optical diffusion method using the Nicomp Model 270 fine particle analyzer of Pacific Scientific Co., and it is taken as an average particle S* diameter.

o

S

35 Example 1 An aqueous dispersion having a 10 solid content concentration of an acrylic polymer (Tg: 530C, average particle diameter: 79 nm, number average molecular weight: 244,000) synthesized from methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate and Nmethylolmethacrylamide was prepared as an aqueous solution

A.

An aqueous dispersion having a 10 solid content concentration of a copolyester (Tg: 740C, average particle diameter: 51 nm) having an intrinsic viscosity of 0.54 synthesized from terephthalic acid, isophthalic aid, sodium sulfoisophthalic acid, ethylene glycol and an adduct of bisphenol A with propylene oxide represented by the following structural formula was prepared as an aqueous solution B.

H3

H(OCHCH

2 n-O-ph- -ph-O-(CH 2 HO)m-H

H

3 H3 CH 3 wherein n m 4 and ph is a phenylene group.

Separately, an unoriented film was prepared by melt extruding a composition comprising 90 by weight of polyethylene terephthalate (intrinsic viscosity: 0.63) and 10 by weight of titanium oxide over a rotary cooling drum maintained at 20°C and then stretched to 3.6 times at 80 0 C in a machine direction. Thereafter, a primer aqueous .o coating solution comprising 40 by weight of the above aqueous solution A, 30 by weight of the aqueous solution B, 20 by weight of an aqueous solution of sodium polystyrene sulfonate (concentration: 10 by wight) as an antistatic agent and 10 by weight of an aqueous solution of polyoxyethylene nonylphenyl ether (concentration: 10 30 by weight) as a surfactant was applied onto both surfaces of a film in an amount of 20 g/m 2 (wet) by a kiss-roll coating method. Subsequently, the film was stretched to 3.6 times at 140 0 C in a transverse direction to obtain a

S

188 pm thick biaxially oriented adhesive polyester film.

The adhesive force of the magnetic coating on the treated surface of this film, the transfer property of the magnetic layer, and the adhesive force of UV ink, antistatic properties and blocking resistance are shown in Table 1.

Example 2 A biaxially oriented adhesive polyester film was obtained by applying onto both surfaces of a film in an amount of 10 g/m 2 (wet) a coating having the same composition as that of Example 1 except that the antistatic agent used in Example 1 was changed to sodium alkyl diphenyletherdisulfonate.

Comparative Example 1 A biaxially oriented adhesive polyester film was obtained by applying onto both surfaces of a film in an amount of 20 g/m 2 (wet) a coating having the same composition as that of Example 1 except that the acrylic polymer used in Example 1 was changed to an acrylic polymer (Tg: 25 0 C, average particle diameter: 72 nm, 25 number average molecular weight: 261,000) which was synthesized from methyl methacrylate, ethyl acrylate, 2hydroxyethyl methacrylate and N-methylolmethacrylamide.

The adhesive force of the magnetic coating on the treated surface of this film, the transfer property of the 30 magnetic layer, and the adhesive force of UV ink, antistatic properties and blocking resistance are shown in Table 1.

:Comparative Example 2 A biaxially oriented adhesive polyester film was 35 obtained by applying onto both surfaces of a film in an amount of 20 g/m 2 (wet) a coating having the same composition as that of Example 1 except that the copolyester used in Example 1 was changed to a copolyester (Tg: 210C, average particle diameter: 65 nm) having an intrinsic viscosity of 0.52 synthesized from terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, 1,4-butanediol and diethylene glycol.

Comparative Example 3 A biaxially oriented adhesive polyester film was obtained by applying onto both surfaces of a film in an amount of 20 g/m 2 (wet) a coating having the same composition as that of Example 1 except that the acrylic polymer used in Example 1 was changed to an acrylic polymer (Tg: 55 0 C, average particle diameter: 208 nm, number average molecular weight: 274,000) which was synthesized from methyl methacrylate, ethyl acrylate, 2hydroxyethyl methacrylate and N-methylolmethacrylamide and the copolyester was changed to a copolyester (Tg: 750C, average particle diameter: 146 nm) having an intrinsic viscosity of 0.54, which was synthesized from terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, 25 ethylene glycol and an adduct of bisphenol A with propylene oxide.

The adhesive force of the magnetic coating on the treated surface of this film, the transfer property of the magnetic layer, and the adhesive force of UV ink, 30 antistatic properties and blocking resistance are shown in Table 1.

Comparative Example 4 A biaxially oriented adhesive polyester film was obtained by applying onto both surfaces of a film in an 35 amount of 20 g/m 2 (wet) a coating having the same composition as that of Example 1 except that the primer coating solution used in Example 1 was changed to a primer aqueous coating solution comprising 45 by weight of the aqueous solution A of an acrylic polymer, 45 by weight of the aqueous solution B of a copolyester and 10 by weight of an aqueous solution of polyoxyethylene nonylphenyl ether (concentration: 10 by weight) as a surfactant.

Comparative Example The adhesive force of the magnetic coating, the transfer property of the magnetic layer, the adhesive force of the UV ink, antistatic property and blocking resistance of a biaxially oriented polyester film obtained without applying primer coating are shown in Table 1.

S S *r t4 *p I I I I I I I 9 VII 9. II V.

I

0 00 pp* Table 1 Transfer property Adhesive force of Adhesive force Surface blocking of magnetic layer magnetic coating of UV ink resistivity resistance width) Examplel1 0 46 5 5 x10' 0 0 Example 2 0 42 5 1 x10 10 0 Comparative Examplel1 45 5 4 x10' 0 Comparative Example 2 X 48 5 7 x 10'0 Comparative Example 3 X 48 4 5 x 1010 0 Comparative Example 4 0 47 5 >10110 0 Comparative Example 5 0 5 1 >1010 0 Since the biaxially oriented adhesive polyester film of the present invention is excellent in the non-transfer property, adhesive force of the magnetic layer and blocking resistance and is satisfactory in terms of antistatic properties compared with the biaxially oriented adhesive polyester film of the prior art, it is useful as a magnetic card, magnetic disk, printing material, etc.

Example 3 An aqueous dispersion having a 10 solid content concentration of an acrylic copolymer (Tg: 53"C, average particle diameter: 79 nm, number average molecular weight: 244,000) which was synthesized from methyl methacrylate, ethyl acrylate, 2-hydroxyethyl methacrylate and Nmethylolmethacrylamide was prepared as an aqueous solution

C.

An aqueous dispersion having a 10 solid content concentration of a copolyester (Tg: 740C, average particle diameter: 51 nm) having an intrinsic viscosity of 0.54, which was synthesized from terephthalic acid, isophthalic aid, 5-sodium sulfoisophthalic acid, ethylene glycol and an adduct of bisphenol A with propylene oxide represented by the following structural formula was prepared as an aqueous solution D.

a a 3 H 3

CH

3 wherein n m 4.

Separately, an unoriented film was prepared by melt extruding a composition comprising 90 by weight of polyester (intrinsic viscosity: 0.63) produced from terephthalic acid and ethylene glycol and 10 by weight of titanium oxide over a rotary cooling drum maintained at 20°C and stretched to 1.5 times and then 2.0 times at in a machine direction. Thereafter, an aqueous coating solution comprising 40 by weight of the above aqueous solution C, 30 by weight of the aqueous solution D, 20 by weight of an aqueous solution of sodium polystyrene sulfonate (concentration: 10 by wight) as an antistatic agent and 10 by weight of an aqueous solution of polyoxyethylene nonylphenyl ether (concentration: 10 by weight) as a surfactant was applied onto both surfaces of a film in an amount of 20 g/m 2 (wet) by a kiss-roll coating method. Subsequently, the film was stretched to 3.2 times at 140 0 C in a transverse direction to obtain a 188 pm thick biaxially oriented white polyester film coated with an adhesive and antistatic coating.

The X-ray diffraction strength ratio, impact strength of this film, the adhesion of the magnetic coating to the coated surface and the peel adhesive force of UV ink, antistatic properties and blocking resistance are shown in Table 2.

Example 4 A biaxially oriented white polyester film coated with an adhesive and antistatic coating was obtained by applying onto both surfaces of a film in an amount of g/m 2 (wet) a coating having the same composition as that of Example 3 except that the copolyester used in Example 3 was changed to a copolyester (Tg: 85 0 C, average particle diameter: 48 nm) having an intrinsic viscosity of 0.56 i: 25 produced from 2,6-naphthalenedicarboxylic acid, :isophthalic acid, 5-Na sulfoisophthalic acid, ethylene glycol and an adduct of bisphenol A with ethylene oxide represented by the following structural formula: 30 3

H

3 H--fOCH 2

CH

2 CH0 2

CH

2 0---H

H

3 o a wherein n m 4.

Example A biaxially oriented white polyester film coated with an adhesive and antistatic coating was obtained by applying onto both surfaces of a film in an amount of g/m 2 (wet) a coating having the same composition as that of Example 3 except that the antistatic agent used in Example 3 was changed to an acrylic polymer produced from methyl methacrylate, ethyl acrylate, acrylonitrile and sodium methacryl sulfonate.

Example 6 A biaxially oriented white polyester film coated with an adhesive and antistatic coating was obtained by applying onto both surfaces of a film in an amount of g/m 2 (wet) a coating having the same composition as that of Example 3 except that the antistatic agent used in .Example 3 was changed to sodium alkyldiphenyl ether 25 disulfonate.

The X-ray diffraction strength ratio, impact strength of this film, the adhesion of the magnetic S. coating to the coated surface and the peel adhesive force of UV ink, antistatic properties and blocking resistance are shown in Table 2.

Example 7

S

A biaxially oriented white polyester film coated with an adhesive and antistatic coating was obtained by •stretching the unoriented film made from the composition 35 comprising a polyester and titanium oxide used in Example 3 to 3.2 times in a machine direction and 3.4 times in a transverse direction after a coating solution is applied.

0 a a. a a *a* a a *aQ 9. 9 .9 .9 9.

9* 9 99 9 .9 9 9 9 0* 9999 9 99@9 9 9 9 9 9 9* 9 99 99* 99 9* .999 96 99 9.99 9. 9 9 9 99* 9 9*9* 9 9 9 99 S. 9 0* 9 99 *9 *9 Table 2 Adhesive force Adhesive Surface Blocking X-ray Impact of magnetic force resistivity resistance diffraction strength coating of UIV ink [fl/squarej strength (peel) ratio width] Example 3 45 5 4 x10 10 0 0.10 0 Example 4 46 5 6 x10 10 0 0.10 0 .Example 5 48 5 9 x10 10 0 0.11 0 .Example 6 47 5 5 x lO'* 0 0.09 0 Example 7 1 -1 1A U 14 Jt0 Biaxially oriented white polyester films obtained in Examples 3 to 7 are excellent in fabricability to a magnetic card and as a substrate for a magnetic card and has excellent levels in the adhesion of a magnetic coating and the peel adhesive force of UV ink, antistatic properties and blocking resistance.

a.

a *ao a.*

Claims

1. A process for producing a biaxially oriented adhesive polyester film comprising the steps of: forming a thin film of an aqueous dispersion by applying onto both surfaces of an unoriented or monoaxialy oriented base film of an aromatic polyester containing to 20 by weight of a white pigment, the aqueous dispersion containing 5 to 70 by weight of fine particles having an average particle diameter of not more than 100 nm of an aromatic copolyester having a secondary transition point of 50 to 120 0 C, 5 to 70 by weight of fine particles having an average particle diameter of not more than 150 nm of an acrylic copolymer having a secondary transition point of 50 to 120 0 C, and 3 to 50 by weight of a water-soluble organic sulfonic acid salt; and, while or after the thin film of the aqueous dispersion is dried, stretching the film biaxially or monoaxially to form a biaxially oriented film having an adhesive coating film.

2. The process of claim 1, wherein the aromatic copolyester contained in the aqueous dispersion comprises an aromatic dicarboxylic acid component in an amount of at least 50 mol% of the whole acid component. 25

3. The process of claim 1, wherein the aromatic copolyester contained in the aqueous dispersion contains an aromatic dicarboxylic acid component having a sulfonate group in an amount of 0.05 to 6 mol% of the whole component.

4. The process of claim 1, wherein the fine particles of the aromatic copolyester contained in the aqueous dispersion have an average particle diameter of 5 to 80 nm.

The process of claim 1, wherein the acrylic copolymer contained in the aqueous dispersion contains a e 35 polymer unit of a Ci C 4 alkyl(meth)acrylate.

6. The process of claim 1, wherein the fine particles of the acrylic copolymer contained in the aqueous 31 dispersion have an average particle diameter of 5 to 120 nm.

7. The process of claim 1, wherein the organic sulfonate contained in the aqueous dispersion is a polymer having a sulfonate group and a number average molecular weight of 1,000 to 1,000,000.

8. The process of claim 1, wherein the aromatic polyester containing a white pigment has a light transmittance of not more than 10

9. The process of claim 1, wherein the aromatic polyester base film containing a white pigment is an unoriented film having a thickness of at least 200 pm or a monoaxially oriented film having a thickness of at least pm.

10. The process of claim i, wherein the aqueous dispersion further contains a wetting agent selected from the group consisting of anionic surfactants, betaine surfactants and nonionic surfactants in an amount of 2 to by weight of the total weight of the solid content.

11. The process of claim 1, wherein the aqueous dispersion has a solid content concentration of 3 to 30 by weight.

12. The process of claim 1, wherein the aqueous dispersion is applied so as to allow a coating film after ea the step of stretching to have a thickness of 0.02 to 2 pm.

13. The process of claim 1, wherein the step is carried out by preheating a film having the thin film of the aqueous dispersion and thermally stretching the film in succession.

14. The process of claim 1, wherein the stretching of the step is carried out to achieve a final area c Sstretch ratio of 7.8 to 13.5 times and each of stretch *ratios in biaxial directions of at least 2.8 times. 59,5 35

15. The process of claim 1 which further comprises the step of heat setting at a range from a temperature 70 0 C higher than the secondary transition temperature of the 32 aromatic polyester containing a white pigment to a temperature below the melting point after the step

16. The process of claim 1 for obtaining a biaxially oriented adhesive polyester film comprising a biaxially oriented base film which satisfies the following expression: 0.15 I(110)/I(100) 2 0.08 wherein 1(110) is an X ray diffraction strength at a plane (110) in parallel to the film surface and I(100) is an X- ray diffraction strength at a plane (100) in parallel to the film surface.

17. A biaxially oriented adhesive polyester film obtained by the process of claim 1.

18. A polyester film having an information function, 15 comprising at least one of a magnetic recording layer and a printing ink layer present on at least part of either one surface of the adhesive coating films on both surfaces of the film of claim 17.

19. A polyester film having an information function, S 20 comprising a magnetic recording layer present mainlyon one adhesive coating film surface and a printing ink layer present mainly on the other adhesive coating film surface on both surfaces of the film of claim 17. °0* DATED: 13 September 1999 PHILLIPS ORMONDE FITZPATRICK Attorneys for: 30 TEIJIN LIMITED T.. f U^ ii If t-