JPH05320393A - Easily adhesive white polyester film - Google Patents

Abstract

PURPOSE:To provide an easily adhesive white polyester film good in the adhesiveness and blocking resistance and useful for magnetic cards, etc., by coating a coating material containing a specific easily adhesive aromatic polyester resin and an antistatic agent on the surface of a white polyester film containing a white pigment. CONSTITUTION:The objective film is produced by melt-extruding a composition comprising 90wt.% of a polyester produced from terephthalic acid and ethylene glycol and 10wt.% of a white pigment such as titanium dioxide on a rotating cooling drum maintained at 20 deg.C, stretching the produced unoriented white polyester into a length of 3.6 times in the mechanical axis direction, coating a composition comprising (A) 60-100wt.% of an easily adhesive aromatic polyester resin having a secondary transition temperature of 20-200 deg.C and (B) 0-40wt.% of an antistatic agent such as diphenyl ether disulfonic acid to form an easily adhesive coating film having a dry coating film thickness of 0.01-5mum, and subsequently stretching the coated film into a length of 3.9 times in the transverse direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily-adhesive white polyester film, and more specifically, it exhibits excellent adhesiveness to magnetic paints, printing inks, etc., and has excellent blocking resistance and antistatic property. White polyester film.

[0002]

Aromatic polyester white films mixed with white pigments such as titanium oxide are widely used for magnetic recording materials, printing materials, etc., but these films are poor in adhesiveness of magnetic paints and printing inks. I have a problem.

A thick white polyester film is used especially for magnetic cards such as telephone cards and prepaid cards, but it has problems in adhesion to magnetic paints and UV ink, and antistatic property. For example, UV ink has a large stress strain during curing and causes interfacial destruction on the surface of the polyester film. Also, as a practical property, durability against shear stress such as scratching of nails is important.

Conventionally, formation of an easily-adhesive primer layer on the surface of such a white polyester film has been studied, and it has been proposed and used to use an acrylic resin, a melamine resin or the like as a primer. But,
Although these resins have excellent adhesion to the ink layer, they have the drawback of being easily peeled off at the interface with the polyester film. Therefore, there is a demand for the development of a primer resin having a high adhesive force at the two interfaces of the ink layer and the polyester film, but a practically satisfactory one has not been obtained yet. In particular, the white polyester film contains a large amount of white pigment and has a large uneven surface structure.
This uneven surface is better than the adhesive strength improvement due to the anchor effect
It is more effective to reduce the adhesiveness due to the reduction of the adhesion area, and it is necessary to solve this point.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to improve such a point, and in particular, it has a high adhesive force at the two interfaces of the ink layer or magnetic coating layer and the polyester film, and also has antistatic property and resistance. An object is to provide an easily adhering white polyester film having a blocking property and the like.

[0006]

The object of the present invention is to:
At least one surface of a white polyester film containing a white pigment and having a thickness of 20 μm or more has (1) a secondary transition point of 20.
-200 ° C easily adhesive aromatic polyester resin 60-1
A dry coating having a thickness of 0.01 using a coating composition containing a composition of 0.
It is achieved by an easily-adhesive white polyester film formed by forming an easily-adhesive coating having a thickness of ˜5 μm.

The polyester constituting the white polyester film as the base in the present invention is a crystallographically oriented linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. is there. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isoterephthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), polyethylene-2,6-naphthalene dicarboxylate, and the like. A combination or a blend of these with a small proportion of another resin is also included. Among these, polyethylene terephthalate, polyethylene
2,6-naphthalenedicarboxylate is particularly preferred.

These polyesters are white pigments,
In particular, it contains titanium oxide and / or barium sulfate.
In addition, inorganic fillers such as silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, etc., organic fillers such as polystyrene resin, acrylic resin, urea resin, melamine resin, polyethylene, polypropylene, ethylene-propylene. Other resins such as terpolymers and olefinic ionomers, antioxidants, ultraviolet absorbers, optical brighteners, and the like may be contained as required.

The white polyester film in the present invention contains 5 to 20% by weight of a white pigment such as titanium oxide and barium sulfate, and the surface glossiness thereof can be arbitrarily selected.

In the present invention, the white polyester film is preferably a biaxially stretched film, and the thickness thereof is 20 μm or more, preferably 50 to 500 μm, particularly preferably 75 to 300 μm. If the thickness is less than 20 μm, the film has a weak stiffness and is unsuitable.
If it exceeds μm, the film-forming property tends to be poor.

In the present invention, the thin layer (coating) provided on at least one side of the white polyester film is (1) 60 to 100% by weight of an easily adhesive aromatic polyester resin having a secondary transition point of 20 to 200 ° C. and (2) Antistatic agent 0-40
It can be formed by applying a coating liquid containing a composition of wt% to the required surface of the white polyester film and drying.

In the present invention, the acid component forming the easily adhesive aromatic polyester resin (1) constituting the coating liquid is terephthalic acid, isophthalic acid, phthalic acid, 1,4-
Examples thereof include cyclohexanedicarboxylic acid, adipic acid, sebacic acid, phenylindanedicarboxylic acid and dimer acid. Two or more kinds of these components can be used. In addition, unsaturated polybasic acids such as maleic acid, fumaric acid and itaconic acid, and hydroxycarboxylic acids such as p-hydroxybenzoic acid and p- (β-hydroxyethoxy) benzoic acid may be used in small proportions with these components. it can. The ratio of the unsaturated polybasic acid component and the hydroxycarboxylic acid component is at most 10 mol%, preferably 5 mol% or less.

As the polyol component forming the aromatic polyester resin (1), ethylene glycol,
1,4-butanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,6
-Hexanediol, 1,4-cyclohexanedimethanol, xylylene glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) glycol, and propylene oxide of bisphenol A represented by the following formula Adducts and ethylene oxide adducts

[0014]

[Chemical 1]

[0015]

[Chemical 2]

The following can be exemplified. These can use 2 or more types.

Among such polyol components, ethylene glycol, ethylene oxide adduct of bisphenol A and propylene oxide adduct, and 1,4-butanediol are preferable, and ethylene glycol is more preferable.
Ethylene oxide adducts and propylene oxide adducts of bisphenol A are preferred.

Further, it is possible and preferable to copolymerize a compound containing a small amount of a sulfonate group or a compound containing a carboxylic acid group in order to facilitate the liquefaction of the aqueous solution.

Examples of such sulfonate group-containing compounds include 5-Na sulfoisophthalic acid, 5-ammonium sulfoisophthalic acid, 4-Na sulfoisophthalic acid, 4-methylammonium sulfoisophthalic acid, 2-
Na sulfoisophthalic acid, 5-K sulfoisophthalic acid,
Examples thereof include 4-K sulfoisophthalic acid, 2-K sulfoisophthalic acid, Na sulfosuccinic acid, and other sulfonic acid alkali metal salt-based compounds or sulfonic acid amine salt-based compounds.

Examples of the carboxylic acid group-containing compound include trimellitic anhydride, trimellitic acid, pyromellitic dianhydride, pyromellitic acid, trimesic acid, cyclobutanetetracarboxylic acid, dimethylolpropionic acid and the like, or monoalkalis thereof. Examples include metal salts.

The aromatic polyester resin (1) in the present invention can be produced by a conventional polyester solution or melt production technique. For example 2,6-
Naphthalenedicarboxylic acid or its ester-forming derivative, isophthalic acid or its ester-forming derivative, and trimellitic anhydride or its ester-forming derivative are reacted with propylene oxide adducts of ethylene glycol and bisphenol A, and then the resulting monomer Alternatively, it is produced by a method of producing a polyester having a predetermined intrinsic viscosity (the viscosity measured at 35 ° C. using o-chlorophenol is preferably 0.2 to 0.8) by polycondensing an oligomer under vacuum. You can At this time, a catalyst that accelerates the reaction, such as an esterification or transesterification catalyst or a polycondensation catalyst, can be used, and various additives such as a stabilizer can be added.

The secondary transition point (Tg) of the aromatic polyester resin (1) is required to be 20 to 200 ° C, preferably 40 to 160 ° C. If this Tg is less than 20 ° C, the heat resistance is insufficient, and blocking occurs when the film roll is stored for a long period of time.

Further, as the antistatic agent (2) constituting the coating liquid in the present invention, a conventionally known low molecular weight substance or high molecular weight substance, for example, a vinyl copolymer having a sulfonic acid metal salt in the molecule, Alkyl sulfonic acid metal salt, alkyl benzene sulfonic acid metal salt, betaine, acrylic polymer having quaternary ammonium salt group, ion conductive polymer such as ionene polymer, phosphate, phosphate, tin oxide-antimony oxide, etc. The metal oxides, metal alkoxides such as alkoxysilane, alkoxytitanium, and alkoxyzirconium, and their derivatives, coated carbon, coated silica, and the like can be used alone or in combination.

The proportion of the antistatic agent in the primer layer comprising the aromatic polyester resin (1) and the antistatic agent (2) is 0 to 40% by weight, preferably 5 to 30% by weight. If this proportion exceeds 40% by weight, the adhesiveness of the primer layer becomes insufficient, which is not preferable.

As a method for producing an aqueous liquid containing the aromatic polyester resin (1), (a) the aromatic polyester resin is dissolved in water or a medium containing water as a main component; Alternatively, an emulsion or suspension is prepared by using an emulsifier, a dispersant, a suspension stabilizer and the like together with a medium containing water as a main component; (c) water after dissolving the aromatic polyester resin in a medium other than water To form an emulsion or suspension, and remove the medium as necessary; (d)
After the aromatic polyester resin is melted by heating and dispersed by contact with water or another medium, the unnecessary medium is removed as necessary. (E) Fine particles of the aromatic polyester resin are prepared in advance, and these particles are mixed with water. Alternatively, it is possible to exemplify dispersion by stabilizing in a medium containing water as a main component.

The production example is shown below. Water is added to an organic solution in which an aromatic polyester resin is dissolved with stirring, preferably with high-speed heating and stirring to obtain an aqueous liquid. Alternatively, an aqueous solution can be prepared by dropping the organic solution into water with stirring. By further distilling the obtained aqueous liquid under atmospheric pressure, preferably under reduced pressure, and distilling off the hydrophilic organic solvent, an aqueous liquid of the aqueous polyester resin containing only the aqueous medium can be obtained. When the aromatic polyester resin is dissolved in a hydrophilic organic solvent that is azeotropic with water, water is azeotroped when the organic solvent is distilled off, so the amount of water loss (azeotrope) should be taken into consideration. It is desirable to add water. The solid content concentration after distillation is preferably 40% by weight or less, and 40% by weight
If it exceeds, the re-aggregation of the aromatic polyester resin dissolved or dispersed in water is likely to occur, and the stability of the aqueous liquid decreases.
Furthermore, the solid content concentration of the aqueous liquid is 30% by weight or less, and further 1
It is preferably 0% by weight or less. On the other hand, the lower limit of the solid content concentration is not particularly limited, but it is preferably 0.1% by weight or more. The average particle size of the polyester resin is usually 1 μm or less, preferably 0.8 μm or less.

The primer aqueous solution in the present invention preferably contains a wetting agent in order to improve the wettability to the white polyester film as the base. As the wetting agent, a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant that makes the surface tension of the aromatic polyester resin aqueous liquid 50 dyne / cm or less, preferably 40 dyne / cm or less. Preferred are, for example, polyethylene oxide / polypropylene oxide block copolymer, polyoxyethylene alkylphenyl ether, polyoxyethylene-fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkane sulfonate, alkyl sulfate,
Examples thereof include alkylbenzene sulfonates, alkyl sulfonates, alkyl diphenyl ether disulfonates, alkyl sulfosuccinates, quaternary ammonium chloride salts and alkyl amine hydrochloric acid. The amount of wetting agent is 2 to 30% by weight of the total solid content of the primer.
Is preferable, and more preferably 3 to 20% by weight.

The primer layer in the present invention can be coated with an organic solvent as a solvent. As the solvent, methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-
One or more selected from hexane, toluene, xylene, methanol, ethanol, n-propanol, isopropanol and the like can be used in combination.

Further, for example, ultraviolet absorbers, pigments, organic fillers, inorganic fillers, lubricants, antiblocking agents, melamine, etc., within the range that does not impair the effects of the present invention.
Other additives such as crosslinking agents such as epoxies, aziridines and the like can be mixed.

The solid content concentration of the aqueous coating liquid is usually 30% by weight.
It is below, and more preferably 10% by weight or less.

In the present invention, the primer coating liquid containing the above-mentioned components is applied to at least one side of the white polyester film, and the white polyester film before the crystal orientation is completed is preferable as the film.

The white polyester film before completion of the crystal orientation is an unstretched film obtained by heat-melting a polyester containing a white pigment into a film as it is;
A uniaxially stretched film obtained by orienting an unstretched film in either the longitudinal direction or the transverse direction; and a low-stretch-oriented film in both the longitudinal and transverse directions (finally reoriented in the longitudinal or transverse direction). It includes a biaxially stretched film before being stretched to complete the oriented crystallization.

As a method of applying the aqueous primer solution to the film, any known coating method can be applied. For example,
A roll coating method, a gravure coating method, a reverse coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method or the like may be applied alone or in combination. The aqueous coating liquid may contain a small amount of an organic solvent for the purpose of assisting stability of the coating liquid or coatability of the coating liquid.

The coating amount is preferably 0.5 to 20 g, more preferably 1 to 10 g per 1 m ² of the running film. The final dry coating film preferably has a thickness of 0.01 to 5 μm, more preferably 0.02 to 0.5 μm.

The coating can be carried out on one side only or on both sides depending on the intended use of the film. After coating, it is dried to form a uniform coating film.

[0036]

EXAMPLES The present invention will be further described below with reference to examples. The properties in the examples were obtained by the following methods.

1. Adhesive Strength of Magnetic Paint The following evaluation paint was applied to the sample film with a Meyer bar so that the thickness after drying was about 4 μm, and dried at 100 ° C. for 3 minutes. After that, aging was performed at 60 ° C. for 24 hours, and then Scotch tape No. A 600 (manufactured by 3M) width of 12.7 mm and a length of 15 cm is adhered so that air bubbles do not enter, and this is leveled with a manual load roll described in JIS C2701 (1975) to make close contact and cut into a tape width. The strength when peeled 180 degrees is measured.

[Evaluation paint] 25 parts by weight of urethane resin Nipporan 2304 (manufactured by Nippon Polyurethane) in terms of solid content, vinyl chloride / vinyl acetate resin S-REC A (Sekisui Chemical Co., Ltd.) 50
Parts by weight, 1 part by weight of the dispersion agent Resion P (manufactured by Riken Vitamin) and 500 parts by weight of the magnetic agent CTX-860 (manufactured by Toda Kagaku Co., Ltd.) are dissolved in a mixed solvent of methyl ethyl ketone / toluene / cyclohexanone to make a 40% solution, which is then 2 with a sand grinder. Disperse in time. After that, 25 parts by weight (corresponding to solid content) of Coronate L as a cross-linking agent is added and well stirred to obtain a magnetic coating material.

2. Adhesive strength of UV ink UV curable printing ink (Flash Dry FDO Red APN made by Toyo Ink) was printed on the sample film by RI tester (Ming Seisakusho) and then medium pressure mercury lamp (80W
/ Cm, single light type; made by Nippon Battery) Curing is performed by a UV curing device to form a UV ink layer having a thickness of 7.0 μm. The UV ink layer is scratched with a nail, and the degree of lack thereof is displayed in 5 levels (good; 5 ... 1; bad).

3. Antistatic property As for the antistatic property, the surface resistivity of the sample film is measured at a temperature of 23 using a resistivity measuring instrument manufactured by Takeda Riken.
The surface resistivity (Ω / □) is measured after 1 minute at an applied voltage of 500 V under conditions of ° C and a measured humidity of 65%. 1 x 10 ¹¹
Ω / □ or less is preferable.

4. Blocking property After overlapping the primer-coated surface and the primer-uncoated surface of the polyester film, cut into 5 cm x 10 cm squares, and in this at 50 ° C and 70% RH for 17 hours, 6 kg /
A pressure of cm ² is applied, and then the peel force of this 5 cm width is measured (peel speed 100 mm / min). The peeling force at that time is displayed as follows. ◯: 4 g / 5 cm or less Δ: 4 to 10 g / 5 cm x: 10 g / 5 cm or more

[0042]

Example 1 A copolyester having an intrinsic viscosity of 0.58 (Tg = Tere) prepared from terephthalic acid, isophthalic acid, 5-Nasulfoisophthalic acid, ethylene glycol and a propylene oxide adduct of bisphenol A represented by the following structural formula. 68 ° C.) in tetrahydrofuran,
Water was added to this and stirred to prepare an aqueous dispersion having a solid content concentration of 4%, which was designated as an aqueous liquid A.

[0043]

[Chemical 3]

On the other hand, polyester made from terephthalic acid and ethylene glycol (intrinsic viscosity 0.63) 9
20% by weight of a composition consisting of 0% by weight and 10% by weight of titanium oxide
The composition was melt-extruded on a rotary cooling drum maintained at 0 ° C. to obtain an unstretched film, and then stretched 3.6 times in the machine axis direction, and then 70% by weight of the above aqueous coating liquid A and an aqueous solution of diphenyletherdisulfonic acid (an antistatic agent) ( A primer coating liquid consisting of 20% by weight of a concentration of 4% by weight and 10% by weight of an aqueous solution of polyoxyethylene nonylphenyl ether as a surfactant (concentration of 4% by weight) was applied to the kiss coating method in an amount of 4 g / m ² (wet). Applied to both sides of the film. Subsequently, the film was stretched 3.9 times in the transverse direction to obtain a film having a thickness of 188 μm.

Table 1 shows the adhesion, antistatic property and blocking resistance of the treated surface of this film.

[0046]

Comparative Example 1 The copolyester used in Example 1 was
Except for Example 1 except that the copolymerized polyester (Tg = 5 ° C.) having an intrinsic viscosity of 0.55 made from terephthalic acid, isophthalic acid, 5-Nasulfoisophthalic acid, 1,4-butanediol and diethylene glycol was used. Similarly, a biaxially stretched primer-coated polyester film was obtained.

Table 1 shows the adhesiveness, antistatic property and blocking resistance of the treated surface of this film.

[0048]

Comparative Example 2 Table 1 shows the adhesion, antistatic property and blocking resistance of the surface of the biaxially oriented polyester film obtained in Example 1 without the primer coating.

[0049]

[Table 1]

As is clear from Table 1, the examples have excellent adhesiveness, antistatic property and blocking resistance.

[0051]

The easily-adhesive white polyester film according to the present invention is particularly excellent in adhesiveness and blocking resistance as compared with the conventional ones, and can be imparted with antistatic property if necessary. Therefore, for example, magnetic cards, magnetic tapes, magnetic It is useful for disks, printing materials, graphic materials, photosensitive materials and the like.

Claims (5)

[Claims] 1. A white polyester film containing a white pigment and having a thickness of 20 μm or more, wherein (1) is provided on at least one side.
A secondary transition point of 20 to 200 ° C. 60 to 100% by weight of an easily adhesive aromatic polyester resin and (2) an antistatic agent 0 to
An easily-adhesive white polyester film obtained by forming an easily-adhesive coating having a dry coating thickness of 0.01 to 5 μm using a coating agent containing a composition of 40% by weight. 2. The easily adhesive white polyester film according to claim 1, wherein the composition comprises 70 to 95% by weight of an easily adhesive aromatic polyester resin and 5 to 30% by weight of an antistatic agent. 3. The easily adhesive white polyester film according to claim 1, wherein the coating agent is an aqueous coating agent. 4. A magnetic recording medium in which a magnetic recording layer is provided on at least a part of the coated surface of the easily adhesive white polyester film according to claim 1. 5. A printing film in which a printing ink layer is provided on at least a part of the coating surface of the easily-adhesive white polyester film according to claim 1.