JPH0745234B2 - Polyester composite film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a polyester composite film having excellent easy adhesion.

[Prior Art] As a method for facilitating adhesion, a surface activation method such as corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, or flame treatment of the film surface (for example, USP 3,018,189, 4,072,
769, 3,364,056), a surface etching method using a chemical such as acid, alkali, amine aqueous solution, trichloroacetic acid, etc. (for example, USP3,186,883), a method for providing a polyester layer, acrylic resin, polyurethane or the like as a primer layer on the film surface (for example, USP4, 224,270, 3,136,655) and the like are known.

[Problems to be Solved by the Invention] In many cases, the existing easy-adhesion treatment methods described above have insufficient adhesive strength. In addition, even if it shows a fairly strong adhesive force for adhesion with the same or similar chemical structure, it can be easily peeled from the adhesion interface by immersing the adhered film in ammonia water or warm water. It had a defect such as being rusty or clouding.

An object of the present invention is to provide an easily adhesive polyester composite film having excellent alkali resistance.

Another object of the present invention is to provide an easily adhesive polyester composite film which is excellent in transparency, antistatic property and water resistance.

[Means for Solving the Problems] The present invention is characterized in that a polymer having a sulfonic acid and / or a salt thereof having an orientation degree in the range of 5 to 100 is laminated on the surface layer of a polyester film substrate. The present invention relates to a polyester composite film.

For laminating a polymer having an oriented sulfonic acid and / or its salt on the surface layer of a polyester film substrate, the polymer having a sulfonic acid and / or its salt (hereinafter referred to as polymer (B)) alone or with another compound is used. This can be achieved by coating the mixed composition on a polyester film and then stretching it under specific conditions.

The polyester in the present invention is a polymer compound having an ester bond in the molecular main chain, which is obtained by polycondensation of a dicarboxylic acid and a diol. Typical polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene α, β-bis (2-chlorophenoxy) ethane 4,
Examples thereof include 4'-dicarboxylate and the like, copolymers thereof with other comonomers, and those having an ether bond in the main chain. In the case of the present invention, in many cases, the effect of the present invention becomes more remarkable when it is a homopolymer. The polyester of the present invention is particularly preferably biaxially stretched and heat-treated to be oriented and crystallized, but may be uniaxially stretched and heat-treated if necessary. Of course, in polyester, known additives as a polymer, such as a stabilizer, a viscosity modifier, an antioxidant, a filler,
You may include a slip agent, an antistatic agent, an antiblocking agent, etc.

Next, the polymer (B) having a sulfonic acid and / or a salt thereof means a polymer having a sulfonic acid having a —SO ₃ X group and / or a salt thereof, which is a typical example. Copolymerized with acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, or styrene in the form of Examples thereof include polymers made of only.

Sulfonated polystyrene and / or salts thereof are preferred from the viewpoint of water resistance and alkali resistance for the purpose of the present invention.

However, X here is selected from cationic ions such as H ⁺ , Na ⁺ , Li ⁺ , NH ₄ ⁺ and K ⁺ , and among them, in the case of the present invention, NH ₄ ⁺ and H ⁺ are particularly preferable. .

In the case of a copolymer with acrylic acid, etc., the polymer (B)
The copolymerization ratio of the monomer having a sulfonic acid and / or its salt therein is preferably 40 to 100 mol% in order to obtain water-resistant, alkali-resistant and easily adhesive property. The weight average molecular weight of the polymer having sulfonic acid and / or its salt is about 10 to 5,000,000, preferably about 2000 to 1,000,000.

The polymer (B) can be coated on a polyester film alone, but in the case of the present invention, it is particularly preferably used in a mixture with another polymer (A). In particular, when coating on a polyester film, the polymer (A) is a water-soluble or water-dispersible polymer such as polyester resin, acrylic resin, polyamide resin, urethane resin, vinyl resin, butadiene resin, Epoxy resins, silicone resins, or mixtures thereof are preferred.

Among the water-soluble or water-dispersible resins, it is particularly preferable to use polyurethane, polyester or acrylic resin from the viewpoint of adhesiveness and transparency.

Specific examples of suitable polyurethanes include those in which the polyurethane has at least one of a carboxylic acid group, a sulfonic acid group, and a sulfuric acid half ester base, and among them, an ammonium salt.

Specific examples of suitable polyesters include polyesters obtained by copolymerizing 0.5 to 20 mol% of 5-sulfosodium isophthalic acid and those obtained by copolymerizing 1 to 30 mol% of polyethylene glycol, ethylene oxide or propylene oxide. be able to. Among them, at least one of terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and adipic acid is used as the acid component, and ethylene glycol or hexane glycol, 1,4-butanediol is used as the alcohol component,
When using a polyester that contains at least one of diethylene glycol, neopentyl glycol, tetramethylene glycol, and polyethylene glycol and has a viscosity of 3 to 6 cps when diluted with an aqueous solution of 5% by weight. In particular, the composite layer surface is smooth and the film gloss is excellent, which is particularly preferable.

Next, examples of the acrylic resin include those containing an alkyl acrylate or an alkyl methacrylate as a main component, and 30 to 99.9 mol% of the component, and a vinyl monomer having a functional group which is copolymerizable therewith. Body composition
A water-soluble or water-dispersible resin containing 70 to 0.1 mol% and having a number average molecular weight of 200,000 to 1,000,000 is preferable.

The reason why the alkyl acrylate or alkyl methacrylate in the acrylic resin is preferably 30 mol% or more is that the coating formability, the strength of the coating film, and the blocking resistance are improved. 99.9 mol% of alkyl acrylate or alkyl methacrylate in acrylic resin
It is preferable that the following is introduced by introducing a compound having a specific functional group as a copolymerization component into the acrylic resin to facilitate water solubilization and water dispersion and to stabilize the state for a long period of time. , Furthermore, the improvement of the adhesiveness between the coating layer and the polyester film layer, the strength of the coating layer due to the reaction in the coating layer, the improvement of the water resistance, the chemical resistance,
Further, it is possible to improve the adhesion between the film of the present invention and other materials.

Examples of the alkyl group of alkyl acrylate or alkyl methacrylate include methyl group, ethyl group, n-
Examples thereof include propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group and cyclohexyl group.

Vinyl monomers copolymerizable with alkyl acrylate or alkyl methacrylate and having a functional group impart hydrophilicity to the resin to improve the water dispersibility of the resin,
Alternatively, a resin and a polyester film, or those having a functional group that improves the adhesiveness between the coating layer and the other coating layer provided on the composite layer are preferable, and the preferable functional group is a carboxyl group and / or a salt thereof, an acid anhydride group. , Sulfonic acid groups, and /
Or a salt thereof, an amide group or an alkylolated amide group, an amino group (including a substituted amino group) or an alkylolated amino group, and / or a salt thereof, a hydroxyl group, an epoxy group or the like. Particularly preferred for adhesion, water solubility, and water dispersibility are carboxyl groups and / or salts thereof,
Examples thereof include acid anhydride groups and epoxy groups. Two or more kinds of these groups may be contained in the resin.

As the vinyl-based monomer having a functional group copolymerizable with alkyl acrylate or alkyl methacrylate, the following compounds having a functional group such as a reactive functional group, a self-crosslinking functional group, a hydrophilic group can be used.

Examples of the compound having a carboxyl group and / or a salt thereof or an acid anhydride group include acrylic acid, methacrylic acid,
Examples thereof include itaconic acid, maleic acid, fumaric acid, crotonic acid, metal salts of these carboxylic acids with sodium, ammonium salts and maleic anhydride.

Examples of the compound having a sulfonic acid group and / or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid, metal salts of these sulfonic acids with sodium, ammonium salts and the like.

Examples of the compound having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylolacrylamide, methylolmethacrylamide, ureido vinyl ether, β-ureidoisobutyl vinyl ether, and ureidoethyl acrylate. Can be mentioned.

Amino group or alkylated amino group and /
Or, as the compound having a salt thereof, diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether, dimethylaminoethyl methacrylate, dimethylaminoethyl vinyl ether, and those obtained by methylating those amino groups. , Alkyl halides, dimethyl sulfate, sultone, and the like, which are quaternized with quaternary salts.

Examples of the compound having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate,
β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxy vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, etc. Can be mentioned.

Examples of the compound having an epoxy group include glycidyl acrylate and glycidyl methacrylate.

In addition to the above compounds, the following compounds may be used in combination. That is, acrylonitrile, methacrylonitrile, styrenes, butyl vinyl ether, maleic acid mono- or dialkyl esters, fumaric acid mono- or dialkyl esters, itaconic acid mono- or dialkyl esters, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, Vinylpyrrolidone,
Examples thereof include, but are not limited to, biyltrimethoxysilane.

The acrylic resin as the polymer (A) may contain a surfactant, but the low molecular weight surfactant contained in the acrylic resin is condensed in the film formation process and accumulated at the interface of the polymer particles. When the coating layer is applied or moves to the interface of the coating layer, problems may occur in the mechanical strength of the coating layer, water resistance, and adhesiveness with the laminate. In such a case, a so-called soap-free polymerized product containing no surfactant can be used.

However the copolymer of 35 / 65-65 / 35 methyl methacrylate and methyl acrylate among them (molar ratio) and trunk polymer, respectively. 1 to -COOH, a monomer having a -CH ₂ OH
Water-dispersible acrylics introduced at 5% by weight are particularly suitable.

The standard of the weight mixing ratio of the polymer (B) having sulfonic acid and / or its salt to all other polymers (A) is 10 to
The range of 95% is often preferable for the present invention.
If it is less than 10% by weight, it is not preferable because the effect of improving the adhesiveness and the antistatic property are insufficient, while 95% by weight.
If the amount is larger, the toughness of the coating film becomes poor, which is not preferable. Particularly, when it is 15% by weight to 30% by weight, the balance between alkali resistance, water resistance, adhesiveness, coating toughness and antistatic property is good, which is preferable.

Methylol- or alkylol-based urea-based, melamine-based, acrylamide-based, polyamide-based resins and epoxies as cross-linking agents to improve the adhesion (blocking), heat resistance, solvent resistance, and mechanical strength of the coating layer Compound, aziridine compound, blocked polyisocyanate,
A reactive compound such as a vinyl compound may be contained in the coating layer. The coating layer of the present invention, if necessary, an antifoaming agent,
Coatability improver, thickener, organic lubricant, inorganic fine particles,
An antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment and the like may be contained.

To improve the coatability and adhesiveness of the coating agent to the film,
The film may be subjected to chemical treatment or electric discharge treatment before coating and stretching, but it is not particularly necessary in the present invention because the affinity with the base film is improved.

The polymer (B) having sulfonic acid and / or its salt is mixed with another polymer (A) and applied to a polyester film, or the polymer (B) is blended with polyester to form a surface layer. Only by obtaining a polyester film having a sulfonic acid group, the easy adhesiveness excellent in alkali resistance and water resistance, which is the object of the present invention, cannot be obtained. For example, JP-A-54-86,526 and JP-A-
As disclosed in JP-A-54-93,025, a mixture of 0.5 to 15 parts by weight of a conductive polymer electrolyte (B) having a sulfonate or the like and 100 parts by weight of an acrylic copolymer (A) is used as a plastic coating material. However, even if the properties such as the antistatic property and the heat seal property are improved, it is not possible to improve the easy adhesion property. That is, the sulfonic acid and / or its salt on the surface layer must be properly oriented.
Orientation of the sulfonic acid and / or its salt in the surface layer not only significantly improves the adhesiveness, especially the adhesiveness with diazo paints, UV inks, gelatin compositions, etc., but also after water-resistant treatment and alkali-resistant treatment. Even if it does, the decrease in adhesive strength is hardly recognized.

That is, the degree of orientation of sulfonic acid and / or its salt is 5 to
When it is in the range of 100, preferably in the range of 10 to 80, it becomes a polyester film having a strong adhesive force which is excellent in ammonia resistance and water resistance. If the degree of orientation is less than 5, and further less than 10, the adhesive strength is significantly reduced by post-processing such as hot water treatment or alkali treatment,
No practical adhesive strength. On the other hand, when the degree of orientation exceeds 100, preferably 80, small cracks are generated in the surface layer, and projections and dents are generated, which not only lowers transparency and antistatic ability but also improves adhesive strength by hot water treatment or alkali treatment. Is drastically reduced and is not practically used. That is, unless it is a polyester having a sulfonic acid and / or a salt thereof in the surface layer with a degree of orientation of 5 to 100, preferably 10 to 80, strong adhesiveness to water resistance and alkali resistance cannot be obtained. Of course, the proper orientation of the sulfonic acid and / or its salt cannot be achieved under arbitrary stretching conditions, but can be achieved by stretching under certain specific conditions. The orientation of the sulfonic acid and / or its salt is such that the main chain to which the sulfonic acid and / or its salt is bonded, such as a vinyl polymer, is oriented parallel to the film surface in the plane of the base film by stretching, and the Since the acid and / or its salt is densely coordinated with the main chain, the sulfonic acid and / or its salt also becomes in-plane oriented. Moreover, at this time, if the stretching conditions are not specified, the sulfonic acid and / or its salt is not only in-plane, but also in the thickness direction, that is, the sulfonic acid and / or its salt is oriented in the direction perpendicular to the film surface. I don't.

In order to bring out the effect of the present invention, it is preferable to stretch a liquid containing sulfonic acid and / or a salt thereof in a state where water is not present in the coating film in the process of stretching after coating. It is effective to increase the concentration of the agent, take the preheating time sufficiently long, increase the stretching temperature in the range where defects such as film tearing and necking stretching do not occur, and increase the stretching speed. . Specifically, the coating agent concentration is 3 to 20% by weight, preferably 5 to 10% by weight, and the stretching temperature is 98 to 180 ° C, preferably 110 to 150 ° C. It is necessary to appropriately select the stretching speed depending on the stretching temperature, and for example, about 10,000% / min to 400,000% / min is preferable.

Furthermore, it is also important that water is present in the drawing process atmosphere. Specifically, it can be achieved by stretching during the stretching step in pressurized water or in the presence of pressurized steam. The humidity at that time must be 10% RH or more, preferably 25% RH or more, as a value in the surface layer of the stretched film. That is, there is no water in the coating film, but the water is present only in the surface layer of the coating film during stretching, so that the sulfonic acid and / or its salt is selectively and strongly oriented.

Next, a typical production method for coating a layer having the polymer (B) on a polyester film will be described, but the production method is not limited thereto. First, after sufficiently drying the polyester pellets, the extruder is fed to a known extruder, preferably a melt extruder having a compression ratio of 3.8 or more, and the pellets are melted at a temperature higher than the temperature at which the polymer decomposes from a slit-shaped die. An unstretched sheet is produced by melt-extruding into a sheet and cooling and solidifying. 80-180 the unstretched sheet
After a coating layer containing a predetermined sulfonic acid group is provided on a film stretched 3 to 8 times at ℃, it is dehydrated by a sufficient preheating process.
Stretching in the transverse direction by 3 to 6 times while humidifying with pressurized steam of 180 ° C. If necessary, 0 to 10% at 150 to 250 ° C
Heat treatment for 0.1 to 10 seconds while giving relaxation.

If necessary, the film may be stretched again 1.1 to 1.7 times in the machine direction.

In the above example, the polyester film substrate to which the polymer (B) is applied may also contain sulfonic acid and / or its salt. In this case, there is an advantage that the adhesive force between the coating layer and the base film becomes strong.
When the polyester base film contains a composition containing sulfonic acid and / or a salt thereof, the addition amount is preferably 5 ppm or more and less than 20% by weight from the viewpoint of improving the adhesiveness and smoothness. Needless to say, it may be a coating composition provided on a substrate. As an example thereof, as the compound having a sulfonic acid and / or a sulfonate contained in the polyester film of the base film, a metal such as sulfoisophthalic acid, sulfoterephthalic acid, sulfonaphthalenedicarboxylic acid, or an ester-forming derivative thereof can be used. Salt and metals such as Li and N
Preferred are a, Mg, Zn, Mn and the like. Of these, particularly preferred compounds include 5-sodium sulfoisophthalic acid,
A polyester compound composed of a dicarboxylic acid containing 5-sodium sulfodimethylisophthalic acid as one component and a diol such as ethylene glycol, butanediol, polyethylene glycol or polytetramethylene glycol. A range of less than 20% by weight is preferable because both thermal stability and adhesiveness can be achieved.

If necessary, corona discharge treatment may be performed in air or other various atmospheres before coating on the film. The anchor treatment may be performed using a known anchor treatment agent such as urethane resin or epoxy resin, but it is not particularly necessary.

The coating method is not particularly limited, and an extrusion laminating method or a melt coating method may be used. However, since it is possible to coat a thin film at a high speed, a paint dispersed in water or various solvents is gravure coated or reverse coated. Spray coating, kiss coating, die coating, or metalling bar coating is preferable.

The thickness of the laminated film after stretching is not particularly limited, but is usually 0.
It is 001 to 5 μm. It is preferably 0.01 to 0.4 μm, and more preferably 0.04 to 0.2 μm from the viewpoint of adhesiveness and antistatic property.

Since the biaxially stretched polyester film obtained by the method of the present invention has the above-mentioned excellent effects, it is used as a packaging material for ICs, photosensitive materials such as microfilms, magnetic recording bases, various plate making applications, tracing films, and electrophotography. It is particularly preferably used for films, films for overhead projectors, inks for offset printing, ultraviolet curable inks, base films for easy adhesion such as cellophane ink, and the like.

If necessary, inorganic particles may be added to the layer containing the sulfonic acid and / or salt thereof, and representative examples thereof include average particle diameter of 1 μm or less, more preferably 0.5 μm or less, and particularly preferably. It is 0.2 μm or less, and specific examples thereof include, but are not limited to, kaolin, silica, silica sol, calcium carbonate, titanium oxide, barium salt, alumina, molybdenum sulfide, carbon black and zirconium.

However, among them, when using a layered silicate showing swelling property, it is suitable from the viewpoint of slipperiness and coating film toughness, and as the layered silicate showing swelling property, montmorillonite, vermiculite, hectorite, teniolite. , Tetrasilicic mica, etc., but teniolite, hectorite, and tetrasilicic mica synthesized from the viewpoint of transparency are preferable.

Further, it is apparent that the sulfonic acid and / or salt-containing layer may contain any additive such as a heat stabilizer, a slip agent, a weather resistance agent, a colorant, an anti-coloring agent, an anti-blocking agent and the like. .

[Effects of the Invention] The polyester composite film according to the present invention is provided with a polymer having appropriately oriented sulfonic acid and / or a salt thereof in the surface layer thereof, and thus achieves easy adhesion, particularly excellent alkali resistance. did it. Further, it has been possible to obtain a film excellent in transparency, antistatic property and water resistance.

[Evaluation Method] The characteristic value of the present invention is based on the following measuring method and evaluation criteria.

(1) Adhesiveness The adhesive strength is as follows: After applying the following coating material, put a cross-cut (100 pieces / cm ² ) on the coating film and cellophane tape: CT-24 (manufactured by Nichiban Co., Ltd.) on the cross-cut surface. Was applied, a load of about 5 kg was applied using a hand roller, and reciprocating was repeated 10 times for pressure bonding. The cellophane tape was peeled by hand and the degree of peeling was observed and evaluated. Judgment criteria are ◯: good (peeling area less than 5%),
Δ: Slightly inferior (peeling area 5% or more and less than 20%), ×: Poor (thin margin area 20% or more).

a) Ultraviolet curable ink (UV ink) ... FDO (black ink) manufactured by Toyo Ink Co., Ltd. was applied by a gravure coater to a thickness of about 5 μm, and treated at an irradiation output of 80 W / cm and an irradiation distance of 10 cm for 8 seconds.

b) Polyvinyl alcohol (PVA) having a degree of polymerization of 1500 and a degree of saponification of 90 mol% was dissolved in water and applied so that the coating film thickness after drying was 5 μm. After coating, it was dried at 130 ° C. for 2 minutes.

c) Cellulose for diazo binder CAB381-05 as commercially available cellulose for diazo binder
(Nagase Sangyo Co., Ltd.) was dissolved in ethyl acetate to obtain a concentration of 10
After the content was adjusted to wt%, bar coating was performed and drying was performed at 110 ° C. for 1.5 minutes to form a coating layer having a thickness of 5.0 μm.

(2) Transparency SEP-H-2 type turbidimeter (Japan Precision Optical Co., Ltd.)
-Haze value (%) determined based on K-6714-58.

(3) Antistatic super insulation resistance meter MODEL-VE-40 (Kawaguchi Electric Industry Co., Ltd.)
The surface resistivity was measured at 20 ° C. and 60% RH at an applied voltage of 100 V.

(4) Water resistance After immersing the laminated film in warm water at 50 ° C. for 30 minutes, a cross cut (100 pieces / cm ² ) was added to the laminated film, and evaluation was made in the same manner as in (1) above. In addition, when the surface state was visually observed to be abnormal (whitening rate), the cellophane evaluation was good (◯) but was poor (x).

(5) Alkali resistance The film () on which the cellulose layer for the diazo binder was formed in the above (1) was immersed in ammonia water having a concentration of 30% by weight for 20 hours at room temperature, and then a cellophane tape was attached to the CAB layer. It evaluated by the same method and judged.

(6) Solvent resistance On the surface of the laminated film, ethyl acetate, toluene as an organic solvent,
Rubbing each of methyl ethyl ketone, acetone, and isopropanol with a cotton swab that is appropriately impregnated with the solvent 5 times (reciprocating times), and observing the change of the surface state with the naked eye and a magnifying glass / or differential interference microscope, and the change is untreated. Relative comparison was made with the following judgment.

A: No change

◯: Slightly dissolved.

Δ: There is a laminated film although it is in a considerably dissolved state.

X: Almost completely dissolved and removed.

(7) As the degree of orientation of sulfonic acid and / or its salt, a value obtained by the following measuring method is used.

The composite layer in the plane of the film was measured by the FT-IR-ATR method in two directions at right angles to the longitudinal direction and the width direction, and the value obtained by multiplying the absolute value of the absorbance attributed to the sulfonic acid group of the difference spectrum by 1000 times To use.

The actual measurement method is shown below.

Cut films of the composite polyester film in two directions at right angles to the longitudinal direction and the width direction are collected.

For the composite layer, the incident direction of infrared light is aligned with the longitudinal direction of the film, and polarized ATR measurement is performed at an incident angle of 45 degrees using polarized light having an electric field spectrum perpendicular to the incident surface.

Next, the incident direction is made to coincide with the width direction of the film and the same measurement is performed.

The difference spectrum is obtained from the spectra obtained in and. At this time, 1450 cm that is not affected by the measuring direction
^The difference spectrum is calculated so that the absorbance at ^-1 becomes 0.

The absolute value of the absorbance of 1155 cm ^-1 attributable to it drawn straight between 1450 cm ^-1 and 1000 cm ^-1 in the difference spectrum to sulfonic acid groups as a baseline.

 The value obtained by multiplying this absorbance by 1000 is defined as the degree of orientation.

That is, if absorption is observed at 1155 cm ^-1 in the difference spectrum of polarization spectra measured in two directions (longitudinal and width), it means that the sulfonic acid group is coordinated in either longitudinal or width direction. To do.

On the other hand, when they are arranged irregularly in the longitudinal direction / width direction, the same degree of absorption appears in the polarization spectra in both the longitudinal direction and the width direction, so the difference spectrum takes a value close to zero.

The range of the degree of orientation 5 to 100 of the present invention is defined by a value in which the sulfonic acid groups are arranged in any of the longitudinal direction and the width direction and the absolute value of the absorbance is multiplied by 1000. And / or a salt thereof is an index indicating the degree of arrangement in a specific direction.

The FT-IR-ATR measurement conditions are as follows: Instrument: IFS-85 (FT-IR made by Bruker) Light source: Clover (SiC) Detector: DTGS (Deutrium Triglycine Sulfate) Beam splitter: Ge coat / KBr Measurement conditions Resolution : 4cm ^-1 , Accumulation number: 1024, Apodization: Triangle, Phase correction: Mertz method Zero filling: 2 Auxiliary device ATR measurement auxiliary device (Model-9, Wilks) IRE Ge (52.5 × 20 × 2mm) Polarizer wire Grid type (manufactured by Specac) [Example] Next, an embodiment of the present invention will be described based on examples.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.62 was added at about 280 ° C.
It was melted in, and electrostatically applied, and cast on a cooling drum at about 35 ° C. Further, it was stretched 3.5 times by roll stretching in the longitudinal direction at about 90 ° C., subjected to corona discharge treatment in air, and then coated with the following water-soluble coating agent.

Acrylic polymer (A): An acrylic polymer (average molecular weight of 500,000) was used in which 2.5 parts by weight of each of a carboxyl group and a methylol group as a functional group were introduced into methyl methacrylate / ethyl acrylate (50/50) mol%. .

Sulfonated polystyrene and / or a salt thereof (B): SO ₂ O ^-
Sulfonated polystyrene having H ⁺ as the X ⁺ ion of the X ⁺ group and having a molecular weight of about 70,000 was used.

The weight ratio of (A) / (B) was set to 80/20, diluted to 6 wt% with water, and colloidal silica having an average particle diameter of 0.12 μm was used as inorganic fine particles in a weight ratio of 0.3 to the solid content in the coating material. What was added in part was used as a coating material.

The coating thickness is 0.07 after biaxially stretching the coating with a gravure coater.
After coating so as to have a thickness of μm, sufficiently dry the water in a preheating process at 110 ° C, and then use steam to raise the ambient temperature to 145 ° C.
Heated and humidified and stretched 4.5 times in the tenter in the width direction, followed by heat treatment at 210 ° C, coating thickness 0.07μ
A film having a base thickness of 50 μm was obtained.

Comparative Examples 1 and 2 A biaxially stretched polyester film was prepared in the same manner as in Example 1 except that the widthwise stretching conditions used in Example 1 were changed to obtain a sample of Comparative Example 1. That is,
A biaxially stretched film was prepared by stretching the coating agent in the width direction before the coating agent was sufficiently dried in the preheating step.

Further, a sample of Comparative Example 2 was prepared in the same manner as in Example 1 except that after the coating agent was applied, it was sufficiently dried in the preheating step, and then stretched in the width direction without being humidified.

Thus, if the sulfonic acid is not properly oriented in the surface layer, the adhesiveness, especially the adhesion after alkali-resistant treatment, becomes weak,
It turns out to be impractical.

Comparative Example 3 The commercially available biaxially stretched polyester film was coated with the 6 wt% water coating agent used in Example 1 and dried to a thickness of 0.07 μm.
A film coated on m was obtained.

The coated surface of the film was evaluated in the same manner as in Example 1, but no excellent effect such as easy adhesion was observed.

Example 2 A film having a thickness of 50 μm was obtained in exactly the same manner as in Example 1, except that the polyethylene terephthalate used in Example 1 was replaced by a mixture with a polyester containing sodium sulfonate. That is, 85 mol% of terephthalic acid and 5-sodium sulfoisophthalic acid as acid components
15 mol% and 10 wt% of a polyester composed of ethylene glycol as a diol were mixed with the polyester and used. The adhesion of the film thus obtained was evaluated.

Thus, it can be seen that the base layer having a sulfonate has better adhesiveness, transparency, and the like.

Claims (3)

[Claims] 1. A polyester composite film comprising a polyester film substrate and a surface layer on which a polymer having a sulfonic acid and / or a salt thereof having an orientation degree of 5 to 100 is laminated. 2. The polyester composite film according to claim 1, wherein the polyester film substrate contains a composition containing sulfonic acid and / or a salt thereof in an amount of 5 ppm or more and less than 20% by weight. 3. The polyester composite film according to claim 1, wherein the polyester film substrate comprises a mixture of a polymer in which isophthalic acid having sulfonic acid and / or a salt thereof is copolymerized, and polyester.