JPH0624765B2 - Laminated polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a laminated polyester film. More specifically, the present invention relates to a laminated polyester film having a modified layer excellent in easy adhesion, solvent resistance, alkali resistance and water resistance.

[Prior Art] Since a polyester biaxially stretched film has excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and heat resistance, a magnetic recording material, a packaging material, an electrical insulating material, It is widely used as a base film for many applications such as various photographic materials and graphic arts materials. However, since the polyester film surface generally has high cohesiveness and poor adhesiveness, various coatings on the surface, for example, magnetic paint, chemical mat paint, diazo paint, gelatin composition, heat seal imparting composition When coating ink, etc., physical properties such as corona discharge treatment on the film surface, corona discharge treatment under various gas atmospheres, plasma treatment, ultraviolet irradiation treatment, etc. are made in order to make the adhesiveness of the coating layer strong. Known treatment methods, chemical etching methods using alkali, trichloroacetic acid, amines, phenols, etc., chemical treatment methods such as primer treatment, or treatment methods using these in combination. Above all, it is widely used to give easy adhesion by primer treatment on the surface of polyester film because of the advantages of treatment process / work safety and high quality fibers of film processed products. The method of performing the primer treatment all at once is considered promising in terms of process simplification and manufacturing cost, and is being actively implemented. On the other hand, as a primer treatment agent, a number of water-solvent compositions have been proposed, among which water-soluble or water-dispersible materials having excellent coating properties on polyester substrates, adhesion of coating layers, abrasion resistance, etc. Various studies have been made to form a coating layer composed of a composition containing a polyester resin as a main component or an acrylic resin. (JP-B-47-40873, JP-B-49-10243, JP-B-56-5476, JP-A-52-19786, JP-A-52-19787
No. 54-43017, No. 56-8845, No. 61-8543
No. 6). It has also been proposed to use a mixture of a polyester resin and an acrylic resin to improve the drawbacks of both. (JP-A-58-124651).

Further, a polyester film provided with an aqueous polyester resin layer grafted with an acrylic polymer has been proposed for the purpose of improving the adhesion to various coating layers and the adhesiveness of the primer layer (JP-A-63-37937). .

[Problems to be Solved by the Invention] However, the above-described conventional technique has the following problems.
That is, when a water-soluble or water-dispersible polyester resin is laminated on a polyester film, the water resistance and hot water resistance of the laminated coating are inferior even if the desired easy adhesion is obtained. Blocking of the films may occur, and depending on the processed product, the adhesive strength may be significantly reduced when subjected to hot water treatment during the manufacturing process. Furthermore, since it is difficult to sufficiently crosslink the polyester resin, the laminated film has poor solvent resistance when an organic solvent-based paint is applied on the surface, so that in some cases partial dissolution of the laminated film occurs and the film is not formed. In some cases, it may become cloudy, or the interface with the property imparting layer formed on the laminated film may be disturbed, resulting in non-uniformity and deterioration of properties.

Further, when an acrylic polymer is laminated, there is a drawback that adhesion to a base polyester film and mechanical strength of a coating film are inferior, although a blockig improving effect is recognized. Providing a coating film in which the polyester resin and the acrylic polymer are mixed for the purpose of improving the defects of both,
The improvement effect is not sufficient. Further, the one in which the aqueous polyester resin grafted with the acrylic polymer is coated on the base polyester film, the adhesion to the base material,
Although the blocking resistance is improved, it is insufficient in terms of organic solvent resistance, warm water resistance and alkali resistance.

The present invention eliminates these drawbacks of the prior art, and provides a laminated polyester film having excellent adhesion and easy adhesion to a substrate and solvent resistance, water resistance, warm water resistance, and alkali resistance. Is.

[Means for Solving the Problems] The present invention provides a copolymer (B) in which a hydrophilic group-containing polyester resin is grafted with at least one acrylic compound (A) on at least one surface of a polyester film.
And a laminated polyester film having a crosslinked modified layer containing a crosslinker as a main component, wherein the crosslinked modified layer is molecularly oriented.

The polyester of the polyester film in the present invention is a general term for polymers having an ester bond as the main bonding chain of the main chain, and particularly preferred polyesters are polyethylene terephthalate, polyethylene 2,6-naphthalate, polyethylene α, β-bis (2-chlorophenoxy) ethane 4,4′-dicarboxylate, polybutylene terephthalate, and the like. Among these, polyethylene terephthalate is most preferable in view of quality, economy, and the like. Therefore, hereinafter, polyethylene terephthalate will be described as a representative of polyester.

In the present invention, polyethylene terephthalate (hereinafter PET)
80 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more has ethylene terephthalate as a repeating unit. Within the limited amount range, the acid component and / or Alternatively, a part of the glycol component may be replaced with the following third component.

-Acid component-Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,
5-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,
4'-diphenyl sulfone dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, p-β-hydroxyethoxybenzoic acid, adipic acid, azelaic acid, sebacic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, ε-oxycaproic acid , Trimellitic acid proposal, trimesic acid, pyromellitic acid, α, β-bisphenoxyethane-4,4′-dicarboxylic acid, α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylic acid, 5 −
Sodium sulfoisophthalic acid-glycol component-propylene glycol, butylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene glycol, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2-bis (4 -Β-hydroxyethoxyphenyl) propane,
Bis) 4-β-hydroxyethoxyphenyl) sulfone, diethylene glycol, triethylene glycol,
Pentaerythritol, trimethylolpropane, polyethylene glycol, etc.

In addition, known additives in this PET, for example, heat stabilizers, oxidation stabilizers, weather stabilizers, ultraviolet rays, absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, A release agent, antistatic agent, nucleating agent, etc. may be added. The intrinsic viscosity of PET as described above (measured in orthochlorophenol at 25 ° C) is 0.40 to 1.2.
Those in the range of 0, preferably 0.50 to 0.80, and more preferably 0.55 to 0.75 d1 / g are suitable for the present invention.

The polyester film using the polyester is preferably a biaxially oriented biaxially oriented polyester film, the biaxially oriented polyester film, a non-stretched polyester sheet or film, in the longitudinal direction and the width direction, so-called It is made by stretching each in a biaxial direction by about 2.5 to 5 times, and shows a biaxially oriented pattern in wide-angle X-ray diffraction.

The thickness of the polyester film is not particularly limited, but is preferably 2 to 500 μm, more preferably 5 to 300 μm, and excellent in handleability in practical use as a base material.

Crosslinked modified layer in the present invention (hereinafter abbreviated as modified layer)
The term "comprises" a composition containing a hydrophilic group-containing polyester resin as a graph and at least one acrylic compound (A) as a copolymer (B), and a cross-linking agent as a main component. The main component means that itself occupies 80% or more in the modified layer.

The hydrophilic group-containing polyester resin in the present invention means a hydrophilic group or hydrophilic group component in the molecule, for example, a hydroxyl group, a carboxyl group, a carbonyl group, a cyano group, an amino group, a methylcarbonyl group, a polyethylene glycol, a carboxylate salt. , A phosphate copolymer, a quaternary ammonium salt, a sulfate ester salt, a sulfonate salt, and the like. Among them, typical polyester copolymers having the following compositions are useful. That is, a polycondensate of an aromatic dicarboxylic acid and / or a non-aromatic dicarboxylic acid, an ester-forming sulfonic acid alkali metal salt compound and a glycol can be used. Specifically, examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and 1,2-bis (phenoxy). ) Ethane-
There are p, p'-dicarboxylic acids and their ester-forming derivatives, and non-aromatic dicarboxylic acids include, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid,
There are sebacic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid and their ester-forming derivatives. Of these, it is preferable that the aromatic dicarboxylic acid and / or its ester-forming derivative accounts for 40 mol% or more based on the total dicarboxylic acid component from the viewpoint of the heat resistance, film strength and water resistance of the resin, and within the range of 1 You may use together 1 or more types of dicarboxylic acid.

As the ester-forming sulfonic acid alkali metal salt compound, for example, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene acid-2,7-dicarboxylic acid, sulfo-p-xylylene glycol, Examples thereof include alkali metal salts (alkali metal salts of sulfonic acid) such as 2-sulfo-1,4-bis (hydroxyethoxy) benzene and ester-forming derivatives thereof, sodium 5-sulfoisophthalic acid, sodium sulfoisophthalic acid and These ester-forming derivatives are more preferably used.

Next, the glycol component is an aliphatic having 2 to 8 carbon atoms or an alicyclic glycol having 6 to 12 carbon atoms,
For example ethylene glycol, 1,3-propanediol, 1,
4-butanediol, 1,2-propylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol,
1,6-hexanediol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, p-xylylene glycol, diethylene glycol, triethylene glycol and the like are preferably used.

In some cases, polyether may be copolymerized.
The polyether referred to here is a hydrophilic polymer having an ether bond as a main bonding chain, and particularly preferred is an aliphatic polyether, for example, polyethylene glycol, polypropylene glycol, glycerin ether,
Polyethylene glycol ether and the like are preferably used.

The hydrophilic group-containing polyester resin may be water-soluble or water-dispersible, and its solubility depends on the type of copolymer composition component,
Depending on the mixing ratio or the presence or absence of addition of the hydrophilic organic compound portion used as the dispersion stability-imparting agent, its type, the amount to be mixed, etc., the hydrophilic organic compound should be added in a small amount as long as it does not impair the dispersion stability. Preferably.
The hydrophilic organic compounds are aliphatic and alicyclic alcohols, esters, ethers and ketones, for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, glycols such as ethylene glycol and propylene glycol. And its derivatives include methyl cellosolve, ethyl cellosolve, n-
Butyl cellosolve, ethyl acetate as an ester, dioxane, tetrahydrofuran as an ether, and methyl ethyl ketone as a ketone. The hydrophilic organic compounds may be used alone or in combination of two or more as required. Among the hydrophilic organic compounds, butyl cellosolve and ethyl cellosolve are particularly preferable in terms of dispersion performance, dispersion stability, coatability and the like. Further, in the hydrophilic group-containing polyester resin, the amount of components such as the ester-forming alkali metal sulfonate compound of the copolymer composition, which particularly contributes to hydrophilicity, is small unless the solubility, dispersion stability, etc. are impaired. Is preferred.

The glass transition temperature (Tg) of the hydrophilic group-containing polyester resin in the present invention is 30 to 80 ° C., preferably 50 to 75.
C. is preferable from the viewpoints of water resistance, alkali resistance, heat resistance of the modified layer, dispersion stability in a coating agent, grafting with an alkali compound, and the like.

The hydrophilic group-containing polyester resin can be produced by a conventional polyester production technique. That is, the above-mentioned acid component and glycol component are esterified or melt-polycondensed using a reaction catalyst such as a transesterification catalyst and a polymerization catalyst to obtain a desired polymer. Furthermore, solution polycondensation can also be applied. At this time, in any case, various modifiers, stabilizers and the like may be added within a range that does not adversely affect the grafting reaction.

Further, the presence of the hydrophilic organic compound is required to obtain an aqueous dispersion of a hydrophilic group-containing polyester resin having poor water solubility. That is, a hydrophilic group-containing polyester resin and a hydrophilic organic compound are mixed, and water is added under stirring, preferably under heating and stirring, or a method of adding the above mixture to water under stirring. When the solid concentration of the obtained aqueous dispersion is high, it is difficult to obtain a uniform dispersion system and the grafting reaction becomes difficult. Therefore, the solid concentration is 40% by weight or less, preferably 30% by weight or less. desirable.

The acrylic compound (A) in the present invention (hereinafter abbreviated as compound (A)) is a compound that is grafted onto a hydrophilic group-containing polyester resin, and specific compounds include alkyl acrylate and alkyl methacrylate ( As the alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group,
t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, cyclohexyl group, phenyl group, benzyl group, etc.), and a reactive functional group copolymerizable with the above unsaturated carboxylic acid ester, self Compounds having a functional group such as a crosslinkable functional group and a hydrophilic group can be used. As the functional group, a carboxyl group and / or a salt thereof, an acid anhydride group, a sulfonic acid group and / or a salt thereof, an amide group or an alkylolated amide group, an amino group (including a substituted amino group) or an alkylol group The amino group and / or a salt thereof, a hydroxyl group, an epoxy group and the like can be exemplified. The following can be illustrated as a compound which has such a functional group.

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, ammonia 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, and ammonia salts.

Examples of the compound having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylol acrylamide, metalol methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, and ureido ethyl acrylate. Can be mentioned.

Amino group or alkylated amino group and /
Alternatively, 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 their amino groups are methyl-rolled. And those obtained by quaternary chlorination with alkyl halides, dimethylsulfate, sultone and the like.

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 vinyltrisalkoxysilane, but are not limited thereto.

These compounds may be grafted alone, or two or more kinds may be graft-copolymerized. Further, a copolymer of two or more compounds having an unsaturated bond may be grafted.

Among these compounds, it is preferable to use a compound having a functional group capable of reacting with a crosslinking binder from the viewpoints of water resistance of coating film, hot water resistance, alkali resistance, solvent resistance, etc., and a hydroxyl group, an amide group, and a methylol group. Those having a functional group such as a carboxyl group and an epoxy group are particularly preferable.

Grafting of the acrylic compound (A) onto the hydrophilic group-containing polyester resin is carried out by a conventional graft polymerization method and is not particularly limited.

As an example of grafting, an acrylic compound (A) is added to an aqueous solution or dispersion of a hydrophilic group-containing polyester resin in the presence of a water-soluble or water-dispersible polymerization initiator to carry out a reaction. As the polymerization initiator, for example, ceric ammonium nitrate, potassium persulfate, ammonium persulfate, cesium ammonium sulfate, ammonium persulfate, cesium ammonium sulfate, hydrogen peroxide, azobisisobutyronitrile, benzoyl peroxide, etc. are used. From the viewpoint of graft polymerizability, it is preferable to use an organic peroxide such as benzoyl peroxide. The graft polymerization reaction is usually carried out under cooling or heating, and the reaction temperature is the reaction rate, the stability of the polymerization system and the graft copolymer (B).
It is desirable that the temperature is 5 to 100 ° C., preferably 10 to 85 ° C.

The graft ratio of the acrylic compound (A) onto the hydrophilic polyester resin is not particularly limited, but is usually 0.5 to 600.
%, Preferably 5 to 300%, more preferably 10 to 1
A range of 00% is desirable from the viewpoint of solvent resistance, water resistance, coatability of the modified layer. The grafting ratio is a value represented by the following formula.

The cross-linking agent as used in the present invention is subjected to a thermal cross-linking reaction with a functional group present in the polymer (B), for example, a hydroxyl group, a carboxyl group, a glycidyl group, an amide group, etc., and finally has a three-dimensional network structure. It is a cross-linking agent for forming a modified layer. In the present invention, when a melamine-based crosslinking agent, a urea-based crosslinking agent or an epoxy-based crosslinking agent is used as a crosslinking binder, a modified layer having a particularly large crosslinking effect and excellent water resistance and solvent resistance is preferable. Specific examples of the epoxy-based cross-linking agent include polyepoxy compounds, diepoxy compounds, and monoepoxy compounds. Examples of the polyepoxy compound include sorbitol polyglycidyl ether,
Examples of the polyglycerol polyglycidyl ether, petaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, and diepoxy compound include, for example, neopentyl glycol. Diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether,
Examples of propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, and monoepoxy compounds include allyl glycidyl ether, 2
-Ethylhexyl glycidyl ether, phenyl glycidyl ether, etc. are mentioned. Examples of the urea-based cross-linking agent include dimethylol urea, dimethylol ethylene urea, dimethylol propylene urea, tetramethylol acetylene urea, and 4methoxy-5 dimethyl propylene urea dimethylol. The melamine-based cross-linking agent is preferably a compound obtained by reacting a methylol melamine derivative obtained by condensing melamine and formaldehyde with a lower alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol or the like, and a mixture thereof. Examples of the methylolmelamine derivative include monomethylolmelamine, dimethylolmelamine, trimethylolmelamine, tetramethylolmelamine, pentamethylolmelamine, and hexamethylolmelamine. These cross-linking agents may be used alone or in combination of two or more depending on the case. The addition amount of the crosslinking agent is 0.001 to 60 parts by weight, preferably 0.01 to 2 parts by weight based on 100 parts by weight of the solid content of the polymer (B).
0 part by weight is desirable in terms of solvent resistance, alkali resistance, and uniform coating property due to crosslinking of the modified layer.

In the present invention, the graft polymer (B) and the cross-linking agent are the main components of the modified layer, but if necessary, other resins such as polyester resins may be used as long as the effects of the present invention are not impaired. A water-soluble or water-dispersible resin such as acrylic resin, urethane resin, epoxy resin, or amide resin may be mixed. In particular, addition of a polyester-based resin or a urethane-based resin is preferable because the adhesion with the base polyester film is improved.

Further, the modified layer may contain a known cross-linking catalyst, specifically, a salt, an inorganic substance, an organic substance, an acid substance, an alkaline substance or the like and a known adhesion promoter to increase the advantage in post-processing. it can. Further, if necessary, known additives such as defoaming agents, coating improvers, thickeners, antistatic agents, antioxidants, ultraviolet absorbers, dyes, pigments in amounts that do not impair the effects of the present invention. Etc. may be included. Fine particles of an inorganic or organic compound may be contained as a lubricant. The laminated thickness of the modified layer is not particularly limited, but is usually 0.0
It is desirable that the thickness is in the range of 2 to 1.0 μm, preferably 0.05 to 0.5 μm.

In the present invention, the crosslinked modified layer needs to be molecularly oriented. The molecular orientation means that the degree of molecular orientation obtained by the method described later is 0.01 or more. By the molecular orientation of the cross-linked modified layer, solvent resistance, water resistance, warm water resistance and alkali resistance are improved, and the degree of molecular orientation is 0.02 to 0.40, preferably 0.03. ~
0.30, more preferably 0.05 to 0.20,
It is particularly desirable in that the effect of improving the adhesiveness is large and the cleavage hardly occurs inside the crosslinked modified layer.

Also, within 100 Å from the surface layer of the crosslinked modified layer, ES
When the presence of the hydrophilic group-containing polyester resin measured by the CA method is below the detection limit, that is, when the resin layer constituting the surface layer is composed of an acrylic compound and a crosslinking agent, the effect of the present invention is more remarkably exhibited. Particularly preferred.

It is difficult to obtain such a modified layer by a general method of coating a biaxially stretched polyester film and drying, and it is effective to carry out the method described below, but the method is not particularly limited.

After sufficiently drying the polyester pellets polymerized by a conventional method, the pellets are fed to a known melt extruder and melted, melt-extruded into a sheet form from a slit die, and cooled and solidified to prepare an unstretched sheet. Next, the unstretched sheet or the unstretched sheet is placed in the longitudinal direction of the film at 75 ° C to 130 ° C.
After subjecting the uniaxially stretched film stretched 2.0 to 5.0 times at 0 ° C. to corona discharge treatment, etc., as necessary, an aqueous solution or water dispersion containing the graft polymer (B) and a crosslinking binder as main components. Apply liquid. The coating method is not particularly limited, and any method such as a gravure coating method, a reverse coating method, a kiss coating method, a die coating method, and a bar coating method can be applied.
The composite film thus obtained is simultaneously biaxially stretched 2.0 to 5.0 times in the longitudinal and transverse directions when an unstretched film is used, and uniaxially when a uniaxially stretched film is used. Stretching is 2.0 to 5.0 times in the direction perpendicular to the stretching direction of the eyes.
In this stretching process, the conditions for stretching are not particularly limited, but it is desirable to select conditions under which water does not exist in the coating film during stretching and crosslinking does not proceed. To achieve such conditions, increase the concentration of the coating liquid and decrease the coating amount,
It is effective to increase the preheating temperature, decrease the stretching temperature, and increase the stretching speed. Further, the coating film after stretching needs to be quickly crosslinked, and for that purpose, there are methods such as increasing the heat treatment temperature and prolonging the heat treatment time. Further, in order to bring the molecular orientation of the crosslinked modified layer into a specific range, relaxation treatment may be carried out in the range of 1 to 20% in the heat treatment step, if necessary.

The method of measuring the characteristic value and the method of evaluating the effect of the present invention are as follows.

(1) Molecular orientation degree The device used for infrared polarization ATR method is Bruker F
A T-IR (IFS-113V) equipped with a polarization ATR measurement accessory device (manufactured by Bio-Rad Digilab) is used. This ATR device has a square Interna with symmetrical edges and a thickness of 3 mm and a side of 25 mm.
l Reflection Element is attached and absorption measurements are made in two directions, parallel and perpendicular to the stretching method.

The incident direction of light is taken as the film flow direction, and the spectra of the coated surface and the uncoated surface are measured using polarized light perpendicular to the incident surface, and they are S _MC and S _MP , respectively.

Also, the incident direction of light is taken in the film width direction, and the spectrum of the coated surface and the uncoated surface is measured using polarized light perpendicular to the incident surface, and they are S _TC and S _TP , respectively.

However, when there is no non-coated surface, the coated surface is wiped with various solvents, water, etc., and then the substrate surface is measured.

The difference spectrum between the coated layer and the non-coated layer is obtained by the following procedure. As the internal reference band when calculating the difference spectrum, the absorption band of the base film observed in the wave number region close to the absorption band of the coat layer required for analysis is selected.

The coefficient is set so that the absorbance of the internal reference absorption band is 0, and the difference spectrum obtained by subtracting the spectrum of the uncoated surface from the spectrum of the coated surface is obtained for each polarization component, and S _⊥
And (S _MC -S _MP) S _‖ (S _TC -S _TP).

The points at two predetermined wave numbers on the difference spectrum thus obtained are connected to form a baseline, and the height from the baseline to the peak of the absorption band is the absorbance A _⊥ (for S _⊥ ) of the coating layer absorption band, Let A _‖ (for S _‖ ).

The absorbance (A _⊥ ) of the coating layer thus obtained,
The degree of orientation (P) is calculated from (A / _| ).

(2) Identification of hydrophilic group-containing polyester by ESCA method.

The measurement by the ESCA method (X-ray photoelectron spectroscopy) was performed under the following conditions.

Device: ESCA750 manufactured by Shimadzu Corporation Excited X-ray: Mg, Kα1.2 ray (1253.6 eV) Energy correction: The binding energy value of C _IS main peak was adjusted to 284.6 eV.

Photoelectron escape angle (θ): 90 degrees Identification was carried out at a depth within 100Å from the surface of the crosslinked modified layer by the above method, and S _2P / C attributed to the hydrophilic group was identified.
_The atomic number ratio is calculated from the _IS peak area ratio and the value is 0.001.
The cases below were defined as below the detection limit.

In addition, the presence or absence of polyester was identified by the proportion of C _IS and O _IS peak components and the peak shape based on the chemical state of the detected element, and in particular the presence or absence of π-π * satellite due to the presence of benzene ring due to polyester. As a result, the S _2P / C _IS atomic ratio and the case where the polyester was not detected were marked with “◯”, and the case where both or one of them was detected was marked with “x”.

(3) Adhesion with the base material The adhesion of the crosslinked modified layer to the base material film is such that a crosscut (100 pieces / cm ² ) is put on the modified layer and the crosscut surface is cut with 45 ° Cello tape (CT- 24 (manufactured by Nichiban Co., Ltd.)
Affix, apply a load of about 5 kg using a hand roller,
The tape was reciprocated 10 times, and the cellophane tape was manually peeled in the direction of 90 ° to determine the degree of peeling or cleavage of the modified layer according to the following criteria.

⊚: Excellent (peeled or cleaved area is less than 1%) ◯: Good (peeled or cleaved area is 1% or more and less than 5%) Δ: Slightly inferior (peeled or cleaved area is 5% or more 2
(Less than 0%) x: Inferior (peeled or cleaved area: 20% or more) (4) Solvent resistance 25 ° C in each of ethyl acetate, toluene, methyl ethyl ketone, acetone, and isopropanol as an organic solvent on the surface of the crosslinked reformed layer. After being soaked for 24 hours at 25 ° C, a rubbing swab excessively impregnated with the solvent was rubbed 5 times (reciprocating times), and the change in the surface condition was observed with the naked eye and a magnifying glass / or a differential interference microscope, and the change was compared with the untreated product. Then, the judgment was made as follows.

A: No change

◯: Slightly dissolved.

Δ: There is a modified layer although it is in a considerably dissolved state.

X: Almost completely dissolved and removed.

(5) Easy adhesion After forming a coating layer using the following coating agent on the cross-linking modified layer of the laminated film, cross-cut (100 pieces /
cm ² ), and the same method as the above (3) was evaluated and judged.

Gravure printing ink Commercially available gravure ink for cellophane printing; Cellocolor ST
(Toyo Ink Mfg. Co., Ltd.) is replaced with toluene / ethyl acetate /
After diluting with a mixed solvent of methyl ethyl ketone (2: 1: 1) to a concentration of 10% by weight, bar coating was performed and the temperature was 100 ° C.
It was dried for 1.5 minutes to form a coating layer having a thickness of 1.5 μm.

Cellulose for diazo binder CAB38 as commercially available cellulose for diazo binder
1-05 (manufactured by Nagase Sangyo Co., Ltd.) was dissolved in ethyl acetate to a concentration of 10% by weight and then bar-coated at 110 ° C.
It was dried for 1.5 minutes to form a coating layer having a thickness of 5.0 μm.

UV curable ink After applying UV Ace (black ink) from Kuboi Ink Co., Ltd. and Flash Dry 161 (black ink) from Toka Dye Co., Ltd. to 2 μm, 3 under one UV lamp with a height of 10 cm and 80 W / cm.
It was cured for a second.

(6) Water resistance, warm water resistance The laminated film is placed in 20 ° C water and 70 ° C warm water for 24 hours.
After soaking for a period of time and taking out, evaluation was made and judgment was made in the same manner as in the above (1). In addition, all the abnormalities (white turbidity, cracks, etc.) observed in the crosslinked modified layer were visually evaluated as (x).

(7) Alkali resistance The film () on which the cellulose layer for the diazo binder was formed in (2) above 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 to form (3) above. It evaluated by the same method and judged.

[Examples] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

Example 1 (1) Production of hydrophilic group-containing polyester resin 100 parts by weight of dimethyl terephthalate, 75 parts by weight of dimethyl isophthalate, 10 parts by weight of dimethyl 5-sodium sulfone isophthalate, 95 parts by weight of ethylene glycol,
85 parts by weight of neopentyl glycol, 0.106 parts by weight of manganese acetate tetrahydrate and 0.07 parts by weight of calcium acetate dihydrate were mixed, and methanol was distilled off at 140 to 220 ° C. under a nitrogen stream to carry out a transesterification reaction. Then, 0.09 parts by weight of trimethyl phosphate, and antimony trioxide of 0.
Add 06 parts by weight from 240 ° C to 280 ° C for 1 hour 30
Temperature rises gradually from normal pressure to 0.5mm
Hg was lowered, excess diol component was removed to the outside of the system, and the polycondensation reaction was carried out by maintaining this state for 40 minutes, and a polyester having a hydrophilic group having a glass transition temperature of 62 ° C. and an intrinsic viscosity “η” = 0.60 was used. A polymer was obtained. Next, this copolymer 25
1 part by weight of a mixture of 0 parts by weight and butyl cellosolve 110 parts by weight
The solution was stirred at 50 ° C. for 4 hours to obtain a uniform solution. To the resulting solution, 480 parts by weight of water was gradually added dropwise under high speed stirring to obtain a uniform dispersion of milky white opaque solid content concentration of 25% by weight.

(2) Production of graft polymer (B) 100 parts by weight of water was added to 70 parts by weight of the dispersion obtained in the above (1), and further 30 parts by weight of water, 1.5 parts by weight of benzoyl peroxide, and methyl methacrylate. A dispersion containing a polymerization initiator consisting of 12 parts by weight and 2.5 parts by weight of polyoxyethylene alkyl ether phosphate was added, and the mixture was stirred for 1 hour under a nitrogen gas flow, and then heated to 75 ° C. Then, a mixture of 40 parts by weight of methyl methacrylate, 30 parts by weight of ethyl acrylate, and 15 parts by weight of glycidyl methacrylate as an acrylic compound to be grafted next is stirred under 8
The mixture was added dropwise to the above-prepared solution kept at 5 ° C over 60 minutes, and stirring was continued at 85 ° C for 120 minutes under a nitrogen flow to obtain a solid concentration of 27
A weight% aqueous dispersion graft copolymer was obtained. The grafting ratio of the graft copolymer was 44%.

(3) Manufacture of laminated polyester film A polyethylene terephthalate homopolymer chip (intrinsic viscosity = 0.62) manufactured by a conventional method is sufficiently vacuum-dried, then supplied to an extruder and melt-extruded at 280 ° C. and cut by 10 μm. After passing through the metal sintered filter of No. 3, the sheet was extruded from the T-shaped die and wound around a cooling drum having a surface temperature of 50 ° C. to be cooled and solidified. In order to improve the adhesion between the sheet and the surface of the cooling drum in the meantime, a wire electrode is arranged on the sheet side and 6000V
DC voltage was applied. Unstretched PET thus obtained
2. Roll the film heated to 95 ° C in the longitudinal direction.
It was stretched 5 times to obtain a uniaxially stretched film. A corona discharge treatment was applied to one side of this film in a carbon dioxide gas atmosphere.
Aqueous dispersion of the graft polymer produced in (2) and melamine-based cross-linking agent "Nikalac" MW12LF as a cross-linking agent.
(Manufactured by Sanwa Chemical Co., Ltd.) was mixed with 5 parts by weight of a cross-linking agent based on 100 parts by weight of the solid content of the graft polymer, and further diluted with water to have a solid concentration of 2% by weight. The coating material was applied to the discharge treated surface using a rod coater so that the coating film thickness after biaxial stretching would be 0.08 μm. As a lubricant, 0.5 part by weight of colloidal silica having an average particle size of 0.10 μm was added to 100 parts by weight of the resin solid content in the coating material.

After the coating, the uniaxially stretched film is introduced into a tenter, and the coating film is dried while gradually dehumidifying the section from the inlet temperature of 150 ° C to the stretching step, and the stretching start point is set to 90 ° C in the direction perpendicular to the longitudinal direction. It was laterally stretched 3.5 times. While further relaxing by 2%, heat treatment was performed at 240 ° C. for 5 seconds to give a modified layer thickness of 0.
A laminated polyester film having a thickness of 50 μm in which 08 μm was laminated was obtained. The crosslinked modified layer thus obtained was molecularly oriented, and the presence of the hydrophilic group-containing polyester at a depth of 100 Å from the surface layer of the crosslinked modified layer was below the detection limit in the ESCA method. This laminated film was excellent in all properties as shown in Table 1.

Comparative Example 1 A laminated polyester film was prepared in the same manner as in Example 1 except that the hydrophilic group-containing polyester resin of Example 1 was used instead of the graft copolymer (B) as the coating material component.
The crosslinked modified layer of this laminated film was inferior in solvent resistance, water resistance, warm water resistance, and alkali resistance because the acrylic compound was not grafted. In addition, the presence of the hydrophilic group-containing polyester was recognized in the crosslinked modified layer.

Comparative Example 2 A laminated polyester film was obtained in the same manner as in Example 1 except that the crosslinking agent was not used. The characteristics are shown in Table 1. Since no cross-linking agent was used, this laminated coating film had remarkably poor solvent resistance, and was insufficient in water resistance, warm water resistance and alkali resistance.

Comparative Example 3 A biaxially stretched polyethylene terephthalate film obtained by subjecting the coating material of Example 1 to a corona discharge treatment had a thickness of 0.
It is coated with a gravure coater so that it will be 08 μm, and 140 ℃
And dried for 1 minute to obtain a laminated polyester film. Since the crosslinked modified layer of the laminated polyester film was not molecularly oriented at all, it was inferior in adhesion to various inks and binders, solvent resistance, water resistance, warm water resistance and alkali resistance.

Examples 2 to 4 Using the coating material of Example 1, the laminated polyester films having different degrees of molecular orientation were prepared by changing the drying conditions during the transverse stretching, the stretching conditions, and the relaxation conditions during the heat treatment. The crosslinked modified layer of these laminated films had the molecular orientation defined in the present invention, and the presence of the hydrophilic group-containing polyester at a depth of 100 Å or less from the surface layer of the crosslinked modified layer was below the detection limit. These all showed good results in all the characteristic evaluations as shown in Table 1, and Example 3 in which the degree of molecular orientation was 0.13 was particularly excellent.

EFFECTS OF THE INVENTION The present invention provides a molecularly oriented crosslinked modified layer containing a hydrophilic group-containing polyester copolymer grafted with an acrylic compound and a crosslinking agent as main components on a polyester film to produce the following: It was possible to obtain such excellent effects.

(1) Excellent adhesion to various overcoat layers.

(2) The crosslinked modified layer is tough and has excellent solvent resistance, water resistance, warm water resistance and alkali resistance.

In particular, when the degree of molecular orientation is within a specific range and when the hydrophilic group-containing polyester is not present in the surface layer of the crosslinking improvement layer, the effects (1) and (2) above become more remarkable.

The laminated polyester film of the present invention is a base film for magnetic recording, a base film for electrical insulation, a base film for capacitors, a packaging base film, various photographic base films, optical base films, graphic arts base films, vinyl chloride films, etc. It is preferably used as an agricultural base film by laminating.

Claims (3)

[Claims] 1. A cross-link comprising a copolymer (B) obtained by grafting at least one acrylic compound (A) onto a polyester resin containing a hydrophilic group on at least one side of a polyester film, and a cross-linking agent as a main component. A laminated polyester film having a modified layer, wherein the crosslinked modified layer is molecularly oriented. 2. The laminated polyester film according to claim 1, wherein the presence of the hydrophilic group-containing polyester resin by the ESCA method is below the detection limit within 100 Å from the surface layer of the crosslinked modified layer. 3. The degree of molecular orientation of the crosslinked modified layer is 0.02 to 0.
40. The laminated polyester film according to claim 1, which is 40.