JP3068955B2 - Easy-adhesive white polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easy-adhesion white polyester film, and more particularly to an easy-adhesion adhesive having excellent adhesion to magnetic paints, printing inks, etc., and also having excellent blocking resistance and antistatic properties. White polyester film.

[0002]

2. Description of the Related Art Aromatic polyester white films mixed with white pigments such as titanium oxide are widely used for magnetic recording materials and printing materials, but said films have poor adhesion to magnetic paints and printing inks. I have a problem.

[0003] In particular, thick white polyester films are used for magnetic cards such as telephone cards and prepaid cards, but they have problems in adhesion to magnetic paints and UV inks, antistatic properties, and the like. For example, UV ink has a large stress strain at the time of curing, and causes interface destruction on the polyester film surface. As practical characteristics, durability against shear stress such as nail scratching is important.

Conventionally, formation of an easily-adhesive primer layer on the surface of such a white polyester film has been studied, and use of an acrylic resin, a melamine resin, or the like as a primer has been proposed and used. But,
These resins have excellent adhesion to the ink layer, but have the disadvantage that they are 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 between the ink layer and the polyester film, but no practically satisfactory primer resin has yet been obtained. In particular, white polyester film contains a large amount of white pigment, and the surface forms a large uneven structure,
This uneven surface is better than the adhesion effect by the anchor effect,
The effect of lowering the adhesion due to the lowering of the bonding area is greater, and a solution in this respect is also necessary.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned point, in particular, to have a high adhesive strength at two interfaces between an ink layer or a magnetic paint layer and a polyester film, and to have an antistatic property and an anti-static property. An object of the present invention is to provide an easily adhesive white polyester film having a blocking property and the like.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
At least one side 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
-Adhesive aromatic polyester resin of 60 to 200 ° C
A dry coating having a thickness of 0.01% by using a coating composition containing a composition comprising 00% by weight and (2) an antistatic agent of 0 to 40% by weight.
This is achieved by an easily-adhesive white polyester film formed with an easily-adhesive film having a thickness of about 5 μm.

The polyester constituting the base white polyester film of the present invention is a linear saturated polyester having crystal orientation synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. is there. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isoterephthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), polyethylene 2,6-naphthalenedicarboxylate, and the like. A coalescence 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, etc., polyethylene, polypropylene, ethylene-propylene Other resins such as terpolymers, olefinic ionomers and the like, antioxidants, ultraviolet absorbers, fluorescent brighteners, and the like can be contained as necessary.

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

In the present invention, the white polyester film is preferably a biaxially stretched film, and has a thickness of 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 is unsuitable because the stiffness of the film is weak.
If it exceeds μm, the film-forming properties tend to be poor.

In the present invention, the thin layer (coating) provided on at least one side of the white polyester film comprises (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 the composition consisting of% by weight 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 includes 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 of these components can be used. Furthermore, it is also possible to use a small proportion of unsaturated polybasic acids such as maleic acid, fumaric acid, itaconic acid and hydroxycarboxylic acids such as p-hydroxybenzoic acid and p- (β-hydroxyethoxy) benzoic acid together with these components. it can. The proportion of the unsaturated polybasic acid component or hydroxycarboxylic acid component is at most 10 mol%, preferably 5 mol% or less.

The polyol component forming the aromatic polyester resin (1) includes 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 of the following formula Adducts and ethylene oxide adducts

[0014]

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[0015]

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And the like. Two or more of these can be used.

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

Further, in order to facilitate aqueous liquefaction, it is possible to copolymerize a compound containing a small amount of a sulfonate group or a compound containing a carboxylate group, which is more preferable.

Such sulfonic acid group-containing compounds include, for example, 5-Na sulfoisophthalic acid, 5-ammonium sulfoisophthalic acid, 4-Na sulfoisophthalic acid, 4-methylammonium sulfoisophthalic acid,
Na sulfoisophthalic acid, 5-K sulfoisophthalic acid,
Examples thereof include alkali metal salts of sulfonic acid such as 4-K sulfoisophthalic acid, 2-K sulfoisophthalic acid, and sodium sulfosuccinic acid, and amine salt compounds of sulfonic acid.

Examples of such a carboxylic acid group-containing compound include trimellitic anhydride, trimellitic acid, pyromellitic anhydride, pyromellitic acid, trimesic acid, cyclobutanetetracarboxylic acid, dimethylolpropionic acid, etc. Metal salts and the like.

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-
Reacting naphthalenedicarboxylic acid or an ester-forming derivative thereof, isophthalic acid or an ester-forming derivative thereof, and trimellitic anhydride or an ester-forming derivative thereof with ethylene glycol and a propylene oxide adduct of bisphenol A; Alternatively, the oligomer is subjected to polycondensation under vacuum to obtain a polyester having a predetermined intrinsic viscosity (viscosity measured at 35 ° C. using o-chlorophenol is preferably 0.2 to 0.8). Can be. At that time, a catalyst for accelerating the reaction, for example, an esterification or transesterification catalyst, a polycondensation catalyst can be used, and various additives, for example, a stabilizer and the like can be added.

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

As the antistatic agent (2) constituting the coating liquid in the present invention, conventionally known low-molecular substances and high-molecular substances, 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 base, ionene polymer, ion-conductive one such as phosphate, phosphate ester, tin oxide-antimony oxide, etc. And one or more selected from metal alkoxides and derivatives thereof, such as metal oxides, alkoxysilanes, alkoxytitaniums, and alkoxyzirconiums, coated carbon, and coated silica.

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 the proportion exceeds 40% by weight, the adhesion of the primer layer becomes insufficient, which is not preferable.

The aqueous liquid containing the aromatic polyester resin (1) can be prepared by (a) dissolving the aromatic polyester resin in water or a medium containing water as a main component; (b) dissolving the aromatic polyester resin in water. Alternatively, an emulsifier, dispersant, suspension stabilizer, or the like is used together with a medium containing water as a main component to form an emulsion or suspension; (c) water is used 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 heating and dissolving the aromatic polyester resin and dispersing it in contact with water or another medium, an unnecessary medium is removed if necessary; (e) preparing fine particles of the aromatic polyester resin in advance, Alternatively, dispersion and stabilization in a medium containing water as a main component can be exemplified.

An example of the production is shown below. Water is added to the organic solution in which the aromatic polyester resin is dissolved under stirring, preferably under high-speed stirring with heating, to obtain an aqueous solution. An aqueous liquid can also be obtained by dropping the organic solution into water under stirring. The resulting aqueous liquid is further distilled under normal pressure, preferably under reduced pressure, to distill off the hydrophilic organic solvent, whereby an aqueous liquid of an aqueous polyester resin containing only an aqueous medium is obtained. When an aromatic polyester resin is dissolved in a hydrophilic organic solvent azeotropic with water, water is azeotropic when the organic solvent is distilled off. It is desirable to add water. The solid concentration after distillation is desirably 40% by weight or less, and is preferably 40% by weight.
When the value exceeds the above range, re-agglomeration of the aromatic polyester resin dissolved or dispersed in water is apt to occur, and the stability of the aqueous liquid is reduced.
Further, the solid concentration of the aqueous liquid is 30% by weight or less,
The content is preferably 0% by weight or less. On the other hand, the lower limit of the solid content concentration is not particularly limited, but 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 aqueous primer solution of the present invention preferably contains a wetting agent in order to improve the wettability of the base white polyester film. As the wetting agent, a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant which makes the surface tension of the aqueous aromatic polyester resin liquid 50 dyne / cm or less, preferably 40 dyne / cm or less. Are preferred, 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 alkyl benzene sulfonate, alkyl sulfonate, alkyl diphenyl ether disulfonate, alkyl sulfosuccinate, quaternary ammonium chloride salt, and alkylamine hydrochloride. The amount of the wetting agent is 2 to 30% by weight of the total solids of the primer.
Is more preferable, and more preferably 3 to 20% by weight.

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

As long as the effects of the present invention are not lost, for example, ultraviolet absorbers, pigments, organic fillers, inorganic fillers, lubricants, antiblocking agents, melamine,
Other additives such as crosslinking agents such as epoxy, aziridine and the like can be mixed.

The solid content of the aqueous coating solution is usually 30% by weight.
Or less, and more preferably 10% by weight or less.

In the present invention, a primer coating solution containing each of the above-mentioned components is applied to at least one surface of a white polyester film, and the film is preferably a white polyester film before crystal orientation is completed.

The white polyester film before the completion of the crystal orientation is an unstretched film obtained by hot-melting a white pigment-containing polyester to form a film as it is;
A uniaxially stretched film in which an unstretched film is oriented in either the machine direction or the transverse direction; a film which is stretched and oriented in two directions, a machine direction and a transverse direction (finally in the machine direction or transverse direction). (A biaxially stretched film) before stretching 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 the stability of the coating liquid or the coatability of the coating liquid.

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

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

[0036]

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

1. Adhesive force of magnetic paint The following paint for evaluation is applied to a sample film using a Meyer bar so as to have a thickness of about 4 μm after drying, and dried at 100 ° C. for 3 minutes. Thereafter, aging was performed at 60 ° C. for 24 hours. A 600 (manufactured by 3M) width of 12.7 mm and a length of 15 cm are adhered so as to prevent air bubbles from entering. A manual load roll described in JIS C2701 (1975) is used to adhere the adhesive, and cut into a tape width. The strength at the time of 180 degree peeling is measured.

[Evaluation coating material] 25 parts by weight of urethane resin Nipporan 2304 (manufactured by Nippon Polyurethane) in terms of solid content, PVC / vinyl acetate resin Esrec A (Sekisui Chemical) 50
Parts by weight, 1 part by weight of a dispersing agent Ratio P (manufactured by RIKEN Vitamin) and 500 parts by weight of a magnetic agent CTX-860 (manufactured by Toda Chemical) are dissolved in a mixed solvent of methyl ethyl ketone / toluene / cyclohexanone to obtain a 40% solution. Spread over time. Thereafter, 25 parts by weight of coronate L (in terms of solid content) of a cross-linking agent is added and stirred well to obtain a magnetic paint.

2. Adhesive force of UV ink After printing a UV curable printing ink (flash dry FDO red APN manufactured by Toyo Ink) on a sample film using an RI tester (manufactured by Meiji Seisakusho), a medium pressure mercury lamp (80 W
/ Cm, single-lamp type; manufactured by Nippon Battery) Curing is performed with a UV curing apparatus to form a 7.0 μm thick UV ink layer. The UV ink layer is scratched with a nail, and the degree of the lack is displayed in five levels (good; 5 ... 1; bad).

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

4. Blocking properties The primer coated surface of the polyester film and the primer-uncoated surface were overlapped, cut into 5 cm × 10 cm squares, and placed in a 50 ° C., 70% RH atmosphere for 17 hours at 6 kg / cm 2.
A pressure of ² cm ² is applied and then the 5 cm wide peel force is measured (peel speed 100 mm / min). The peeling force at that time is indicated as follows. ：: 4 g / 5 cm or less △: 4 to 10 g / 5 cm ×: 10 g / 5 cm or more

[0042]

Example 1 A copolymerized polyester (Tg = 0.58) made from terephthalic acid, isophthalic acid, 5-Na sulfoisophthalic 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 the mixture and stirred to prepare an aqueous dispersion having a solid concentration of 4%.

[0043]

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On the other hand, polyester made from terephthalic acid and ethylene glycol (intrinsic viscosity 0.63) 9
A composition comprising 0% by weight and 10% by weight of titanium oxide
A non-stretched film was melt-extruded on a rotating cooling drum maintained at a temperature of about 0 ° C., and then stretched 3.6 times in the machine axis direction. Then, 70% by weight of the aqueous coating solution A and an aqueous solution of diphenyl ether disulfonic acid as an antistatic agent ( A primer coating solution consisting of 20% by weight (concentration 4% by weight) and 10% by weight of an aqueous solution (concentration 4% by weight) of polyoxyethylene nonyl phenyl ether as a surfactant was applied in an amount of 4 g / m ² (wet) by the kiss coating method. And 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 summarizes the adhesiveness, antistatic property and blocking resistance of the treated surface of this film.

[0046]

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

Table 1 summarizes the adhesion, antistatic properties and blocking resistance of the treated surface of this film.

[0048]

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

[0049]

[Table 1]

As is clear from Table 1, those of the examples secure excellent levels of adhesiveness, antistatic property and blocking resistance.

[0051]

The easily adherent white polyester film according to the present invention is particularly excellent in adhesiveness and blocking resistance as compared with conventional ones, and can be provided with antistatic properties as required. Useful for discs, printing materials, graphic materials, photosensitive materials, etc.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-17135 (JP, A) JP-A-1-208132 (JP, A) JP-A-62-241928 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C08J ^7/ 04-7/06 B32B 27/00-27/42

Claims (5)

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