JP2586664B2 - Laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a low-density cushioning property, a folding property, and a white property having a modified layer having excellent adhesion, solvent resistance, alkali resistance, and water resistance. The present invention relates to a laminated film having excellent properties. For more information, see paper substitutes: cards, labels, stickers,
Courier slips, video printer receiving paper, bar code printer receiving paper, poster, map, dust-free paper, display plate,
White plate, photographic paper, copy paper and various printing papers, such as UV
The present invention relates to a laminated film used as a base material for ink printing paper, flexographic printing paper, and the like.

[Prior Art] Conventionally, as a polyester film used as a substitute for paper for the above-mentioned applications, a polyester film obtained by adding a large amount of titanium dioxide or calcium carbonate to polyester to impart whiteness is known.

However, a film obtained by adding a large amount of an inorganic substance such as titanium dioxide or calcium carbonate to a polyester can impart whiteness but cannot reduce the specific gravity, and the film itself becomes hard and rough, resulting in a problem depending on the application. It may be. Also, when polypropylene is added, the hardness of the film itself is somewhat relaxed as compared with the case where an inorganic substance is added, but not only the thermal dimensional stability is poor but also the sost properties, flexibility and There is a disadvantage that the whiteness is poor. That is, a polyester film having a low specific gravity and excellent thermal dimensional properties has not been obtained.

Generally, the surface of the polyester film is subjected to various treatments because the surface of the polyester film has high cohesiveness and poor adhesion. Above all, the application of easy adhesion by the primer treatment is widely performed due to the advantages of the treatment process, the safety of the workplace, and the maintenance of high quality of the film-processed product.

Numerous aqueous solvent compositions have been proposed as primer treatment agents, and among them, a water-soluble or water-dispersible polyester resin having excellent coatability to a polyester substrate, adhesion of a coating layer, abrasion resistance and the like. Various studies have been made to form a coating layer composed of a resin-based composition or an acrylic resin. It has also been proposed to improve the disadvantages of both by using a mixture of a polyester-based resin and an acrylic-based resin (Japanese Patent Application Laid-Open No. 58-124651).
issue).

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 tackiness of the primer layer (JP-A-63-37937). .

However, the conventional technique described above has the following problems. In other words, when a water-soluble or water-dispersible polyester resin is laminated on a polyester film, even if the desired easy-adhesion property is obtained, the water resistance and body temperature of the laminated film are inferior. Underneath, blocking between the films may occur, or depending on the processed product, when subjected to hot water treatment during the manufacturing process, the adhesive strength may be significantly reduced. Further, since it is difficult for the polyester resin to be sufficiently cross-linked, the laminated film is poor in solvent resistance upon application of the organic solvent-based paint on the surface, and in some cases, the laminated film partially dissolves and the film is formed. In some cases, the film may become cloudy, or the interface with the property-imparting layer formed on the laminated film may be disturbed, resulting in non-uniformity, leading to a deterioration in properties.

In addition, when an acrylic polymer is laminated, although the blocking improving effect is recognized, there is a drawback that the adhesion to the base polyester film, the mechanical strength of the coating film, and the like are poor. Even if a coating film in which the above-mentioned polyester-based resin and acrylic polymer are mixed is provided for the purpose of improving both disadvantages, the effect of the improvement is not sufficient. Further, the adhesion and blocking resistance of the aqueous polyester resin grafted with the acrylic polymer to the substrate are improved, but are insufficient in terms of organic solvent resistance, hot water resistance and alkali resistance.

[Problems to be Solved by the Invention] Accordingly, an object of the present invention is to eliminate these disadvantages of the prior art, and to provide adhesion and easy adhesion to a substrate, solvent resistance,
An object of the present invention is to provide a laminated polyester film having excellent water resistance and alkali resistance, and also having excellent thermal dimensional stability, whiteness, softness and flexibility.

[Means for Solving the Problems] As a result of intensive studies, the present inventors have obtained a low specific gravity obtained by adding a non-stratified polymer and a low specific gravity agent to polyester, and have excellent thermal dimensional stability and whiteness. By providing a crosslinked modified layer mainly composed of a copolymer obtained by grafting a hydrophilic group-containing polyester resin with at least one kind of acrylic compound and a crosslinker on a white polyester film, The present inventors have found that a white polyester laminated film having excellent solvent resistance, water resistance and alkali resistance can be obtained, and completed the present invention.

That is, the present invention provides a copolymer (B) obtained by grafting at least one type of acrylic compound (A) on a hydrophilic group-containing polyester resin and a cross-linking agent on at least one surface of the film support (I). A laminated film having a crosslinked modified layer as a main component, wherein the film support (I) is a polyester film having a heat shrinkage of less than 2% at 150 ° C. and a specific gravity of 0.95 or less, Provided is a laminated film characterized in that the S _{2 P} / C _{1 S} atomic ratio measured by X-ray photoelectron spectroscopy is 0.001 or less within 100 ° in a depth direction from the surface of the modified layer.

[Effect of the Invention] According to the present invention, a polyester film having excellent thermal dimensional stability and reduced specific gravity is provided. Further, the following effects can be obtained when the shape of the incompatible polymer dispersed in the polyester has a shape close to a spherical shape.

(1) Although the specific gravity is as low as 0.95 or less, a film having excellent thermal dimensional stability, high cushioning property and high whiteness can be obtained.

(2) If necessary, a film having excellent thermal dimensional stability can be obtained even with a specific gravity as small as 0.6 to 0.7.

(3) Whiteness is high and color tone b value is small, giving a high quality image.

Further, on the polyester film, provided a crosslinked modified layer containing a hydrophilic group-containing polyester copolymer grafted with an acrylic compound and a crosslinking agent as main components, and in a depth direction from the surface of the crosslinked modified layer. Within 100 °, the following excellent effects can be obtained by setting the atomic ratio of S _2P / C _1S measured by X-ray photoelectron spectroscopy to 0.001 or less.

(4) Excellent adhesion with various overcoat layers.

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

[Specific description of the invention] The laminated film of the present invention is a laminated film comprising a film support (I) and a crosslinked modified layer.

In the present invention, the support (I) is a polyester film having a heat shrinkage at 150 ° C. of less than 2% and a specific gravity of 0.95 or less.

In the present invention, the specific gravity of the polyester film is 0.95
Or less, preferably 0.90 or less, more preferably 0.80 or less. If it is larger than 0.95, the film does not have a soft feeling and flexibility. Flexibility is a necessary item, for example, in that a clear image can be transferred even when the pressure of the thermal recording head is reduced when used as receiving paper for a video printer or the like. Of course, the feel when touching the hand is also an important factor.

In the present invention, the heat shrinkage of the polyester film is
It is less than 2%, preferably less than 1% at 150 ° C. in both the longitudinal and width directions. When the heat shrinkage is 2% or more, the thermal dimensional stability of the film is deteriorated, and the film is easily deformed in a process to which heat is applied such as thermal transfer, printing, and drying.
In particular, the heat shrinkage at 150 ° C. is often important.

The polyester in the present invention is a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid, and examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, and sebacic acid. The diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimethanol and the like. Specifically, for example, polyethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate and the like can be mentioned. In the case of the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferred. The polyethylene terephthalate film is excellent in water resistance, durability, chemical resistance and the like.

Of course, these polyesters may be homopolyesters or copolyesters. Examples of the copolymer component include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, and dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 5-sodium sulfoisophthalic acid. Can be.

Further, various known additives such as an antioxidant and an antistatic agent may be added to the polyester.

The immiscible polymer used in the present invention is poly-3
-Methylbutene-1, poly-4-methylpentene-1,
Polyvinyl-t-butane, 1,4-trans-poly-2,3-
Dimethylbutadiene, polyvinylcyclohexane, polystyrene, polymethylstyrene, polydimethylstyrene, polyfluorostyrene, poly-2-methyl-4-fluorostyrene, polyvinyl-t-butyl ether, cellulose triacetate, cellulose tripropionate, polyvinyl fluoride, poly It is a polymer having a melting point of 200 ° C. or higher selected from chlorotrifluoroethylene and the like. In the case of the present invention, poly-4-methylpentene-1, cellulose triacetate, and modified products thereof are particularly preferable in terms of price, heat stability, dispersibility with polyester, and the like. Of course, the melting point of the incompatible polymer is 200 ° C. or higher,
Preferably, it is 210 ° C. or higher, more preferably 220 ° C. or higher. When the melting point is less than 200 ° C., the dispersed shape of the incompatible polymer in the polyester film does not take a spherical shape, often takes a flat, laminar shape, and a high-cushioning polyester film cannot be obtained. . Further, the melting point of the incompatible polymer is preferably 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 260 ° C. or lower. This is because the incompatible polymer does not dissolve unless the temperature is lower than the melt extrusion temperature of the polyester.

The addition amount of the incompatible polymer is preferably 3 to
The content is 30% by weight, more preferably 5 to 20% by weight. If the addition amount is less than 3% by weight, not only is it difficult to obtain a polyester film of the present invention having a specific gravity of 0.95 or less, but also it is difficult to obtain a white polyester film having a whiteness of 80% or more. % Or more, it is difficult to obtain a polyester film excellent in cushioning property. Conversely, the amount of the immiscible polymer added is 30% by weight.
When it exceeds, not only the mechanical properties of the polyester film of the present invention are inferior, but also the thermal dimensional stability is inferior.
Problems such as an increase in the heat shrinkage at 150 ° C. of 5% or more occur.

Next, the specific gravity reducing agent used in the present invention is a compound having an effect of reducing specific gravity by adding to polyester, and the effect is recognized only for a specific compound. For example, polyalkylene glycols such as polyethylene glycol, methoxypolyethylene glycol, polytetramethylene glycol, and polypropylene glycol, ethylene oxide / propylene oxide copolymers, sodium dodecylbenzenesulfonate, sodium alkylsulfonate, glycerin monostearate, Butylphosphonium para-aminobenzenesulfonate and the like. In the case of the present invention, polyethylene glycol is particularly preferred. By adding the specific gravity reducing agent, the specific gravity of the polyester film can be reduced by 0.1 g / cc or more. Further, the addition of the low specific gravity agent has the effects of improving the whiteness of the polyester film, smoothing the surface, improving the cleavage resistance, and greatly improving the stretchability of the polyester.

The amount of the low specific gravity agent added in the present invention is preferably 0.1 to 5% by weight, and more preferably 0.5 to 3% by weight. When the addition amount is less than 0.1% by weight, the specific gravity of the polyester film does not become low, the film does not become a soft film, and the specific gravity of the polyester film does not easily become 0.95 or less. Conversely, if the addition amount exceeds 5% by weight, not only the effect of lowering the specific gravity is not recognized, but also the whiteness of the film decreases, and the b value becomes a large positive value.

Next, in the present invention, it is preferable that the immiscible polymer has a nearly spherical shape in the polyester film, that is, the shape factor is in the range of 1 to 4. Significant differences occur in the properties of the obtained film, particularly the correlation between the specific gravity of the film and the cushion rate, thermal dimensional stability, surface roughness, whiteness, etc., depending on the properties of the incompatible polymer in the polyester film. That is, when the shape of the immiscible polymer is close to spherical, not only can the specific gravity be reduced as compared to the case where the incompatible polymer is dispersed in a layer, but also a whiteness, a cushion rate and a film having good thermal dimensional stability can be obtained. it can. Dispersing the polymer in a shape close to a sphere is due to the fact that the shape of the polymer is not
It depends strongly on the compatibility parameter, melting point, and the type and amount of the low specific gravity agent. The shape close to a sphere means that the shape factor of the incompatible polymer dispersed in the film, that is, the ratio of the major axis to the minor axis is from 1 to 4, preferably from 1 to 2.

The cushion ratio of the polyester film in the present invention is preferably 10% or more, more preferably 15% or more. If the cushion ratio is less than 10%, for example, when the pressure of the thermal recording head is reduced when used as a receiving paper for a video printer or the like, it becomes difficult to clearly transfer an image, and when the hand is touched. The feel is also poor.

The whiteness of the polyester film in the present invention is preferably 80% or more, more preferably 90% or more. Further, the color tone b value obtained by the color difference meter is preferably -3 or less,
More preferably, it is -4 or less and -20 or more. The smaller the b value is, the higher the apparent whiteness of the film is, and the higher the grade gives an image.

Although the color tone changes with the addition of the above-mentioned incompatible polymer or low specific gravity agent, a fluorescent whitening agent may be added as necessary. As optical brighteners, trade names "Ubitek" OB, M
D (manufactured by Ciba-Geigy), "OB-1" (manufactured by Eastman) and the like.

The optical density of the polyester film in the present invention,
Preferably 0.7 or more and 1.6 or less, more preferably 0.8 or more
1.6 or less. When the optical density is less than 0.7, the concealing property of the film becomes insufficient and the back side becomes transparent, which is not preferable. On the other hand, if the optical density exceeds 1.6, a large amount of fine bubbles must be contained, and the film strength is undesirably reduced.

Fine particles such as calcium carbonate, amorphous zeolite particles, anatase type titanium dioxide, calcium phosphate, silica, kaolin, talc and clay may be used in combination with the polyester film of the present invention. The amount of these additives is preferably 0.005 to 25 parts by weight based on 100 parts by weight of the polyester composition. In addition to such fine particles, fine particles precipitated by the reaction between a catalyst residue and a phosphorus compound in a polyester polycondensation reaction system can be used in combination. Examples of the precipitated fine particles include those composed of calcium, lithium and phosphorus compounds, and those composed of calcium, magnesium and phosphorus compounds. The content of these particles in the polyester is 100% polyester.
It is preferably 0.05 to 1.0 part by weight based on part by weight.

The crosslinked modified layer in the present invention is composed of a polymer (B) obtained by grafting at least one or more acrylic compounds (A) onto a hydrophilic group-containing polyester resin and a composition mainly containing a crosslinking agent. Things. The main component means that it occupies 80% or more in the modified layer.

The hydrophilic group-containing polyester resin in the present invention is a hydrophilic group or a hydrophilic component in a 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, It is a polyester copolymer into which at least one or more of a phosphate ester salt, a quaternary ammonium salt, a sulfate ester salt, a sulfonate and the like are introduced. Among them, those having the following compositions are useful as typical polyester copolymers. That is, a polycondensate of an aromatic dicarboxylic acid and an ester-forming sulfonic acid alkali metal salt compound with a glycol may be used. Specifically, examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p'-dicarboxylic acid, and esters thereof. There are formed derivatives, and non-aromatic dicarboxylic acids include, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 3−
There are cyclohexanedicarboxylic acids, 1,3-cyclopentanedicarboxylic acids and their ester-forming derivatives. Among them, the aromatic dicarboxylic acid and / or its ester-forming derivative accounts for 40 mol% of the total dicarboxylic acid component.
It is preferable to occupy the above in view of heat resistance, coating strength and water resistance of the resin, and within the range, one or more dicarboxylic acids may be used in combination.

Examples of the ester-forming sulfonic acid alkali metal salt compound include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, and 4-sulfonaphthalene-
Alkali metal salts (alkali metal salts of sulfonic acids) such as 2,7-dicarboxylic acid, sulfo-p-xylene glycol, 2-sulfo-1,4-bis (hydroxyethoxy) benzene, and ester-forming derivatives thereof are listed. 5
-Sulfoisophthalic acid, sodium sulfoisophthalic acid and their 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-xylene glycol , Diethylene glycol, triethylene glycol and the like are preferably used.

In some cases, a 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, such as polyethylene glycol, polypropylene glycol, glycerin ether, or polyethylene glycol ether. It is preferably used.

The hydrophilic group-containing polyester resin may be water-soluble or water-dispersible, the solubility of which is the type of the copolymer composition, the mixing ratio or the addition of a hydrophilic organic compound used as a dispersion stability imparting agent. Although it depends on the presence / absence, type, blending amount, and the like, it is preferable that the amount of the hydrophilic organic compound be small as long as the dispersion stability is not impaired. The hydrophilic organic compound is an aliphatic or alicyclic alcohol, ester, ether, ketone,
For example, alcohols such as methanol, ethanol, isolopanol, n-butanol, glycols such as ethylene glycol and propylene glycol, and derivatives thereof such as methylcellosolve, ethylcellosolve,
n-butyl cellosolve, ethyl acetate as S-Ls,
Examples of ethers include dioxane and tetrahydrofuran, and examples of ketones include methyl ethyl ketone. The hydrophilic organic compounds may be used alone or in combination of two or more as needed. Among the hydrophilic organic compounds, butyl cellosolve and ethyl cellosolve are particularly preferable from the viewpoint of dispersion performance, dispersion stability, and applicability. Further, in the hydrophilic group-containing polyester resin, the amount of the component which particularly contributes to hydrophilicity, such as the ester-forming sulfonic acid alkali metal salt compound of the copolymer composition, should be 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. The water resistance, alkali resistance, heat resistance, and It is preferable in terms of dispersion stability, grafting with an acrylic compound, and the like.

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

Further, in order to obtain an aqueous dispersion of a hydrophilic group-containing polyester resin having poor water solubility, the presence of the hydrophilic organic compound is necessary. That is, it is produced by mixing a hydrophilic group-containing polyester resin and a hydrophilic organic compound, and adding water under stirring, preferably under heating and stirring, or by adding the above mixture to water under stirring. . Incidentally, when the obtained aqueous dispersion has a high solid content concentration, it is difficult to obtain a uniform dispersion system, and the grafting reaction becomes difficult.
It is desirably at most 30% by weight, preferably at most 30% by weight.

The acrylic compound (A) (hereinafter, abbreviated as compound (A)) referred to in the present invention is a compound that is grafted to 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, a t-butyl group,
A 2-ethylhexyl group, a lauryl group, a stearyl group, a cyclohexyl group, a phenyl group, a benzyl group, etc.), and a reactive functional group capable of copolymerizing with the unsaturated carboxylic acid ester, a self-crosslinking functional group, Compounds having a functional group such as a hydrophilic group can be used. Examples of the functional group include 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 amino group and / or a salt thereof, a hydroxyl group, and an epoxy group. can do. Examples of the compound having such a functional group include the following.

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

Examples of the compound having an amide group or an alkylolated amino group and / or a salt thereof include diethylaminoethyl ether, 3-aminopropyl vinyl ether,
Examples thereof include 2-aminobutyl vinyl ether, dimethylethyl vinyl ether, those in which the amino group is methylolated, those quaternized with an alkyl halide, dimethyl sulfate, sultone, and the like.

Examples of the compound having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxyvinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, pyroethylene glycol monoacrylate, and polyethylene glycol. Examples include monomethacrylate, polypropylene glycol monoacrylate, and polypropylene glycol monomethacrylate.

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

Further, other than the above compounds, the following compounds may be used in combination. That is, acrylonitrile, methacrylonitrile, styrenes, butyl vinyl ether, mono or dialkyl maleate, mono or dialkyl fumarate, mono or dialkyl itaconate. Examples include, but are not limited to, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, vinyl trisalkoxysilane, and the like.

These compounds may be grafted alone, or 2
More than one species 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 agent from the viewpoints of water resistance, warm water resistance, alkali resistance, solvent resistance, etc. of the coating film, and a hydroxyl group, an amide group, a methylol group, Those having a functional group such as a carboxyl group and an epoxy group are particularly preferred.

The grafting of the acrylic compound (A) to the hydrophilic group-containing polyester resin is performed 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 aqueous dispersion of a hydrophilic group-containing polyester resin in the presence of an aqueous solution or a water-dispersible polymerization initiator to cause a reaction. Examples of the polymerization initiator include ceric ammonium nitrate, potassium persulfate, ammonium persulfate, cesium ammonium sulfate, ammonium persulfate, cesium ammonium sulfate, hydrogen peroxide, azobisisobutyronitrile, and benzoyl peroxide. However, use of an organic peroxide such as benzoyl peroxide is preferred from the viewpoint of graft polymerizability. The graft polymerization reaction is usually
The reaction is carried out under cooling or heating, but the reaction temperature is desirably 5 to 100 ° C, preferably 10 to 85 ° C, in view of the reaction rate, the stability of the polymerization system and the characteristics of the graft copolymer (B).

Acrylic compound (A) for hydrophilic polyester resin
Although the grafting ratio of is not particularly limited, usually 0.5 to 600%,
The range of preferably 5 to 300%, more preferably 10 to 100% is preferable in view of the solvent resistance, water resistance, coating property and the like of the modified layer. The grafting ratio is a value represented by the following equation.

The cross-linking agent referred to in the present invention is a functional group present in the polymer (B), for example, a hydroxyl group, a carboxyl group, a glycidyl group, an amide group, etc., undergoes a thermal cross-linking reaction and finally has a three-dimensional network structure. It is a crosslinking agent for forming a porous 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 the crosslinking agent, a modified layer having a particularly large crosslinking effect and excellent water resistance and solvent resistance is preferably obtained. Specific examples of the epoxy crosslinking agent include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and the like.
For example, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidiether, norimethylolpropane polyglycidyl ether, diepoxy compound As, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether , Polytetramethylene glycol diglycidide Ether, as a monoepoxy compound, e.g., allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether. Examples of the urea-based crosslinking agent include dimethylol urea, dimethylol ethylene urea, dimethylol propylene urea, tetramethylol acetylene urea, 4-methoxy-5-dimethylpropylene urea dimethylol, and the like. As the melamine-based cross-linking agent, a compound obtained by reacting a methylol melamine derivative obtained by condensing melamine and formaldehyde with methyl alcohol, ethyl alcohol, isopropyl alcohol or the like as a lower alcohol, and a mixture thereof are preferable. As methylol melamine derivatives,
For example, monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine and the like can be mentioned. These crosslinking agents may be used alone or in combination of two or more in some cases. The amount of the crosslinking agent added was 0.001 to 100 parts by weight of the solid content of the polymer (B).
From 60 to 60 parts by weight, preferably from 0.01 to 20 parts by weight, is desirable from the viewpoint 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 used as main components of the modified layer. However, if necessary, another resin such as a polyester resin may be used as long as the effects of the present invention are not impaired. A water-soluble or water-dispersible resin such as a resin, an acrylic resin, a urethane resin, an epoxy resin, or an amide resin may be mixed. Especially polyester resin,
The addition of a urethane-based resin is preferable because the adhesion to the base polyester film is improved.

Further, a known crosslinking catalyst, specifically, salts,
By including an inorganic substance, an organic substance, an acid substance, an alkali substance, or a known adhesion promoter, advantages in post-processing can be increased. Further, if necessary, known additives in an amount that does not impair the effects of the present invention, for example, an antifoaming agent, a coating improver, a thickener, an antistatic agent, an antioxidant, an ultraviolet absorber, a dye , A pigment or the like, or fine particles made of an inorganic or organic compound as a lubricant. The lamination thickness of the modified layer is not particularly limited, but is usually 0.1.
It is desirably in the range of 02 to 1.0 μm, preferably 0.05 to 0.5 μm.

In the present invention, the crosslinked modified layer is preferably molecularly oriented. The term “molecularly oriented” means that the degree of molecular orientation determined by the method described below is 0.01 or more. Water resistance, warm water resistance and alkali resistance are improved by the molecular orientation of the crosslinked modified layer. In particular, the degree of molecular orientation is preferably 0.02 to 0.40, and more preferably 0.03 to 0.3.
A value of 0, particularly preferably 0.05 to 0.20, is particularly desirable in that the effect of improving easy adhesion is large and cleavage within the crosslinked modified layer is unlikely to occur.

Further, in order to achieve the effects of the present invention, particularly, hot water resistance and alkali resistance, the S _2P / C _1S atomic ratio measured by X-ray photoelectron spectroscopy within 100 ° in the depth direction from the surface of the crosslinked modified layer is It must be less than 0.001.

In order to make such an S _2P / C _1S atomic ratio of 0.001 or less, after coating, no water is present in the coating film in the process from stretching start to completion in the process of stretching in the width direction, and It is important to select conditions under which crosslinking is unlikely to proceed. To select such conditions, increase the coating concentration, or reduce the amount of water to dry by reducing the coating thickness,
A method of increasing the drying temperature after application and lowering the stretching temperature,
There are methods of increasing the stretching speed, and the like, which can be achieved by appropriately combining these. Specifically, it is effective to raise the drying temperature (for example, 150 ° C.), and then gradually lower the temperature, and lower the temperature at the stretching start point (for example, 90 ° C.).

Next, a method for producing the laminated film of the present invention will be described, but the present invention is not limited to such an example.

First, a sheet of the support (I) of the present invention is formed.
4 as an incompatible polymer in polyethylene terephthalate
-Methylpentene-1 polymer and polyalkylene glycol as a low specific gravity agent are added, sufficiently mixed and dried, and then supplied to an extruder A heated to 270 to 300 ° C and formed into a sheet shape from a T die. Can be. In addition, a polyethylene terephthalate containing an additive such as inorganic particles is supplied to the extruder B by a conventional method, and the three layers of the B / A / B in which the polymer of the extruder B layer is formed on both surfaces by a T-die three-layer die. It can also be laminated into a structure and formed into a sheet.

The sheet-like film obtained as described above has a temperature of
An unstretched film can be obtained by tightly cooling and solidifying by electrostatic force on a cooling drum at 10 to 60 ° C. Next, the unstretched film or unstretched film is guided to a group of rolls heated to 80 to 120 ° C., and longitudinally stretched to 2.5 to 5.0 times in the longitudinal direction to 20 to
After applying a corona discharge treatment or the like as necessary on a uniaxially stretched film obtained by cooling with a group of rolls at 30 ° C., an aqueous solution or aqueous dispersion containing the graft polymer (B) and a crosslinking agent as main components is applied. I do. 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. Such a composite film, in the case of using an unstretched film, is simultaneously biaxially stretched 2 to 5 times vertically and horizontally, and in the case of using a uniaxially stretched film, in a direction perpendicular to the stretching direction of the first axis. Stretch 2-5 times. In this stretching process, the stretching ratio is 2 to 5 times in the vertical and horizontal directions, and the area ratio (longitudinal stretching ratio × lateral stretching ratio) is preferably 6 to 20 times. When the area magnification is less than 6 times, the whiteness of the obtained film becomes poor, and when it exceeds 20 times, the film tends to be broken at the time of stretching and the film forming property tends to be poor. In the stretching, it is desirable to select a condition in which no moisture is present in the coating film and the crosslinking does not proceed. In order to achieve such conditions, it is effective to increase the concentration of the coating liquid, reduce the amount of coating, increase the preheating temperature, or decrease the stretching temperature to increase the stretching speed.

The biaxially stretched film and coating film thus obtained are heat-set at 150 to 240 ° C. in a tenter in order to quickly crosslink the film and to impart flatness and dimensional stability to the film. In order to obtain a heat shrinkage in the range of the present invention, the polyester film needs to be heat-treated at 200 ° C., preferably 220 ° C. or higher. In order to keep the molecular orientation of the crosslinked modified layer in a specific range, it is necessary to perform one or more
The relaxation treatment may be performed in the range of up to 20%. After the heat treatment, the film is uniformly gradually cooled, cooled to room temperature, and wound up to obtain the film of the present invention.

[Measurement of physical properties and evaluation method of effect] (1) Surface roughness According to JIS B0601-1976, cutoff 0.25mm, measurement length 4
Center line average roughness R _a (μm) and maximum roughness R _t (μm) in mm
Ask for.

(2) Equivalent sphere equivalent diameter of voids A cross section cut in the machine direction or its vertical direction in the film forming process is taken at a magnification of 1000 to 5000 times with a scanning electron microscope, and at least the specified thickness range Ten
Zero or more voids are applied to an image analyzer to determine the distribution of the diameter of a circle corresponding to the void area. The volume average diameter of this distribution is defined as the average sphere equivalent diameter of the voids.

(3) Specific gravity 25 using a carbon tetrachloride-n-heptane density gradient tube.
Use the value at ° C.

(4) Heat shrinkage The film is cut into 10mm width and 300mm length in the longitudinal or width direction, marked at 200mm intervals, and fixed tension (5
g) After fixing below, measure the original length a (mm) of the marking interval. Next, apply a load using a 3g clip and apply 150
Treat for 30 minutes while rotating in a hot air oven at ℃, and measure the marking interval b (mm) in the same manner as the original length measurement. The heat shrinkage is determined by the following equation, and the average value of five pieces is used.

Heat shrinkage (%) = (ab) / a (5) Optical density The films are stacked so as to have a thickness of about 150 μm, and the transmission density is measured using an optical densitometer (TR927, manufactured by Macbeth). The thickness of the film and the optical density are plotted, and the optical density corresponding to a thickness of 150 μm is determined.

(6) Whiteness According to JIS-L-1015, Shimadzu Corporation UV-260
When the reflectance at wavelengths of 450 nm and 550 nm is B% and G%, respectively, whiteness (%) is expressed by 4B-3G.

(7) Color Tone The surface color of the film was measured using a color difference meter # 80 manufactured by Nippon Denshoku Industries Co., Ltd.
And the determination is made based on the obtained L value, a value, and b value.

(8) Stretchability When a film is continuously formed for 24 hours, a film having no film tear is defined as “good”, and a film having two or more breaks is defined as “breakable”.

(9) Slit chips When the film of the present invention was cut with a single-edged razor for 24 hours,
The case where the white powder is attached to the leather is referred to as “occurrence”.

(10) Cushion ratio (%) Standard gauge 90930 is used for dial gauge No.2109-10 of Mitoyo Seisakusho Co., Ltd.
o.Load 5 on the dial gauge holding part using 7001DGS-M.
Thickness of each film when 0g and 500g are applied
It is obtained from d ₅₀ and d ₅₀₀ by the following equation.

(11) Shape Factor In the same manner as when determining the average diameter of voids, the shape of the immiscible polymer in the cross section of the film is measured by an image analyzer and expressed as a ratio of 100 average major axis / minor axis.

(12) Molecular orientation The infrared polarization ATR method is used. The device is Bruker FT-IR
(IFS-113V) attached to a polarized ATR measurement device (Bio-Rad Dig)
ilab) is used. This ATR device has a square Int with a thickness of 3 mm and a side of 25 mm with symmetrical edges.
Attach an ernal Reflection Element and measure absorption in two directions parallel and perpendicular to the stretching direction.

Taking the incident direction of light to the film flow direction, coated surface with a polarization perpendicular to the plane of incidence, the spectrum of the non-coated surface was measured, each S _MC, and S _MP.

Further, the light incident direction is taken in the film width direction, and the spectrum of the coated surface and the spectrum of the uncoated surface are measured using polarized light perpendicular to the incident surface, and are respectively _designated as _STC and _STP .

However, when there is no uncoated surface, the coated surface is wiped with various solvents, water and the like, and then the substrate surface is measured.

 The difference spectrum between the coated layer and the uncoated layer is determined by the following procedure.
Confuse. As the internal reference band when calculating the difference spectrum
In the wavenumber region close to the absorption band of the coat layer necessary for analysis.
The absorbance of the base internal absorption band of the base film measured is
Determine the coefficient so that it becomes 0, and determine the spectrum of the coated surface.
The difference spectrum obtained by subtracting the spectrum of the uncoated surface from
For the light component, S_⊥(S_MC−S_MP), S (S_TC−S
_TP). On the difference spectrum obtained in this way,
The point at the two determined wave numbers is taken as the baseline,
The height from the baseline to the peak of the absorption band is the coat layer
Absorbance A of absorption band_⊥(S_⊥), A (S To
).

 The absorbance (A) of the coat layer thus obtained was_⊥)
And (A )) To calculate the degree of orientation (P).

(13) as measured by S _2P / C _1S atomic ratio measuring ESCA method (X-ray photoelectron spectroscopy) by ESCA method is performed under the following conditions.

Device :( Shimadzu Corporation) ESCA750 excited X-ray: M _g, Kα1,2 line (1253.6 eV) Energy correction: Binding energy value of C _IS main peak
Adjust to 284.6 eV Photoelectron escape angle (θ): 90 degrees Identification at a depth of 100 ° or less from the surface of the cross-linked modified layer by the above-mentioned method, and S _2P / C _1S attributed to the hydrophilic group
The ratio of the number of atoms is determined from the peak area, and when the value is 0.001 or less, the result is indicated by “」 ”.

(14) Adhesion to substrate The adhesion of the cross-linked modified layer to the substrate film is measured by inserting a cross cut (100 / cm ² )
Stick cellotape (CT-24 (Nichiban)) on 5）,
Using a hand roller, apply a load of about 5 kg, reciprocate 10 times, press and adhere, and peel off the cellophane tape by 90 ° by hand, and determine the degree of separation or cleavage of the modified layer based on 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%) △: Slightly poor (peeled or cleaved area is 5% or more 20)
%: ×: Inferior (exfoliated or cleaved area is 20% or more) (15) Solvent resistance Each of ethyl acetate, toluene, methyl ethyl ketone, acetone, and isopropanol is used as an organic solvent on the surface of the crosslinked modified layer at 25 ° C. After immersion for 24 hours, rub 5 times (reciprocating times) with a cotton swab moderately impregnated with the solvent, observe changes in the surface state with the naked eye and a magnifying glass and / or a differential interference microscope, and compare the change with the untreated product. Then, determination is made as follows.

A: No change at all.

：: Slightly dissolved.

Δ: Remarkably dissolved, but modified layer is present.

×: Almost completely dissolved and removed.

(16) Easy adhesion After forming a coating layer using the following coating material on the crosslinked modified layer of the laminated film, cross cut (100 / cm
² ) is added, and evaluation and judgment are made in the same manner as in the above (14).

Gravure printing ink Commercial gravure ink for cellophane printing: Cellophane ST
(Toyo Ink Manufacturing Co., Ltd.)
After diluting with a mixed solvent of methyl ethyl ketone (2: 1: 1) to a concentration of 10% by weight, bar coating and drying at 100 ° C. for 1.5 minutes to form a coating layer having a thickness of 1.5 μm.

Cellulose for diazo binder CAB381- is commercially available cellulose for diazo binder.
05 (made by Nagase Sangyo Co., Ltd.)
After adjusting to 10% by weight, bar coating is performed and dried at 100 ° C. for 1.5 minutes to form a coating layer having a thickness of 1.5 μm.

UV curable ink After applying 2 μm of UV Ace (ink) of Kuboy Ink Co., Ltd. and Flash Dry 161 (ink) of Toka Pigment Co., Ltd.
Curing is performed for 3 seconds under one UV lamp having a height of 10 cm and 80 W / cm.

(17) Water resistance and warm water resistance The laminated film is immersed in water at 20 ° C. and warm water at 70 ° C. for 24 hours, taken out, and evaluated in the same manner as in the above (15). In addition, all (x) are those in which abnormalities (white turbidity, cracks, etc.) are visually observed in the crosslinked modified layer.

(18) Alkali resistance The film () on which the cellulose layer for diazo binder was formed in (15) was immersed in a 30% by weight aqueous ammonia at room temperature for 20 hours. Evaluate and determine in the same way.

[Examples] Hereinafter, the present invention will be described based on examples, but examples of the present invention are 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 sulfoisophthalate, 95 parts by weight of ethylene glycol, 85 parts by weight of neopentyl glycol Then, 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 at 140 to 220 ° C. under a nitrogen stream to carry out a transesterification reaction, followed by 0.09 parts by weight of trimethyl phosphate. ,
0.06 parts by weight of antimony trioxide was added, and the temperature was raised from 240 ° C to 280 ° C over 1 hour and 30 minutes, and the pressure was gradually increased from normal pressure.
Reduce to 0.5 mmHg, remove excess diol component out of the system, keep this state for further 40 minutes to perform polycondensation reaction, glass point transfer temperature 62 ° C, hydrophilic group-containing polyester copolymer with intrinsic viscosity [η] = 0.60 I got Next, a mixture of 250 parts by weight of the copolymer and 110 parts by weight of butyl cellosolve was added at 150 ° C. for 4 hours.
After stirring for an hour, a homogeneous solution was obtained. 480 parts by weight of water was gradually added dropwise to the resulting solution under high-speed stirring to obtain a uniform milky white opaque dispersion having a solid 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, 12 parts by weight of methyl methacrylate And a dispersion containing a polymerization initiator consisting of 2.5 parts by weight of a 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. Next, methyl methacrylate 40 is used as an acrylic compound to be grafted.
Parts by weight, a mixture of 30 parts by weight of ethyl acrylate, and 15 parts by weight of glycidyl methacrylate was added dropwise to the above-prepared solution kept at 85 ° C. with stirring over 60 minutes, and stirring was continued at 85 ° C. for 120 minutes under nitrogen flow. An aqueous dispersion graft copolymer having a solid content of 27% by weight was obtained. The grafting ratio of the graft copolymer is
44%.

(3) Production of laminated polyester film polyethylene terephthalate (intrinsic viscosity [η] = 0.6
5) Raw material obtained by mixing 88% by weight of poly (4-methylpentene-1) (10% by weight of Mitsui Petrochemical Co., Ltd. TPX-D820) and 2% by weight of polyethylene glycol having a molecular weight of 4000 is supplied to the extruder A. And melted at 285 ° C according to a conventional method.
It was introduced into the central layer of the layer composite die.

On the other hand, the polyethylene terephthalate 90% by weight,
A raw material to which 10% by weight of calcium carbonate (average particle size: 0.8 μm) and 0.01% by weight of an optical brightener OB-1 are added is supplied to an extruder B and melted at 285 ° C. by a conventional method to form a T-die three-layer composite. The melt sheet was laminated on both surfaces of the die and the surface temperature was changed to 25.
On a cooling drum maintained at a temperature of 0 ° C., the mixture was tightly cooled and solidified by an electrostatic method. The unstretched film thus obtained was stretched 3.5 times using a group of rolls heated to 98 ° C. in the longitudinal direction according to a conventional method, and cooled to 25 ° C. to obtain a uniaxially stretched film. One side of this film is subjected to corona discharge treatment in a carbon dioxide atmosphere,
Aqueous dispersion of the graft polymer prepared in the above (2) and a melamine-based crosslinker Nicalac MW12LF as a crosslinker
A coating agent was prepared by mixing 5 parts by weight of a crosslinking agent with 100 parts by weight of a graft polymer (manufactured by Sanwa Chemical Co., Ltd.) at a solids weight ratio and further diluting with water to a solids concentration of 5.0% by weight. It was applied to the discharge-treated surface using a rod coater so that the thickness of the coating film after biaxial stretching was 0.08 μm. In the coating material, colloidal silica having an average particle size of 0.10 μm was used as a lubricant, with a resin solid content of 10%.
0.5 parts by weight was added to 0 parts by weight.

The uniaxially stretched film after application is guided 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. It was stretched 3.5 times. Further, heat fixing was performed at 225 ° C. to obtain a laminated film having a thickness of 75 μm.

The physical properties of the obtained film are shown in the table. It can be seen that the film thus obtained is a polyester film having excellent thermal dimensional properties, high cushioning properties and high whiteness and a low specific gravity. The crosslinked modified layer is molecularly oriented and has excellent adhesiveness, solvent resistance and the like.

Comparative Examples 1-2 When the same procedure was performed as in Example 1 except that polypropylene (Noblen J4H manufactured by Mitsui Toatsu Co., Ltd.) was used instead of the incompatible polymer poly-4-methylpentene-1 used in Example 1. Comparative Example 1 and Comparative Example 2 where no heat treatment was performed in Comparative Example 1.

The properties of the obtained film are shown in the table. It can be seen that when polypropylene is used, a low specific gravity film having excellent dimensional stability cannot be obtained.

Examples 2 to 3 Comparative examples 3 to 4 Films were obtained in exactly the same manner as in Example 1 except that the amount of the low specific gravity agent polyethylene glycol (PEG) used in Example 1 was changed.

The properties of the obtained film are shown in the table. It can be seen that a film having low specific gravity and excellent thermal dimensional stability can be obtained by adding the low specific gravity polyethylene glycol.

Comparative Example 5 A laminated film was produced 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 a coating component. The properties of the obtained film are shown in the table. The crosslinked modified layer of this laminated film was inferior in solvent resistance, water resistance, hot water resistance, and alkali resistance because no acrylic compound was grafted.

Comparative Example 6 A laminated film was obtained in the same manner as in Example 1 except that no crosslinking agent was used. The properties of the obtained film are shown in the table. Since no cross-linking agent was used, this laminated coating film had extremely poor solvent resistance, and was insufficient in water resistance, warm water resistance and alkali resistance.

Examples 4 to 6 Using the coating composition of Example 1, laminated films having different degrees of molecular orientation were produced by changing the drying conditions and the stretching conditions during the transverse stretching and the relaxation conditions during the heat treatment. The characteristics of the obtained films are shown in the table, and it is understood that the crosslinked modified layers of these laminated films are excellent.

Claims (8)

(57) [Claims] 1. A copolymer (B) obtained by grafting at least one kind of acrylic compound (A) to a hydrophilic group-containing polyester resin on at least one surface of a film support (I) and a cross-linking agent. A laminated film provided with a crosslinked modified layer as a component, wherein the film support (I) comprises 15
A polyester film having a heat shrinkage at 0 ° C of less than 2% and a specific gravity of 0.95 or less, and S _2P / S measured by X-ray photoelectron spectroscopy within 100 ° in the depth direction from the surface of the crosslinked modified layer. A laminated film having a C _1S atomic ratio of 0.001 or less. 2. The laminated film according to claim 1, wherein the incompatible polymer is dispersed and mixed in the polyester film, and the shape factor of the incompatible polymer in the film is from 1 to 4. 3. The incompatible polymer is a methylbutene polymer,
The laminated film according to claim 2, wherein the laminated film is a polymer having a melting point of 200C or more selected from methylpentene polymer, styrene-based polymer, fluorine-based polymer, cellulose acetate, and cellulose propionate polymer. 4. The laminated film according to claim 1, wherein a color tone b value of the polyester film determined by a color difference meter is -3 or less. 5. The laminated film according to claim 1, wherein the polyester film is obtained by adding a low specific gravity agent to polyester. 6. A polyalkylene glycol as the low specific gravity agent,
Ethylene oxide / propylene oxide copolymer,
The laminated film according to claim 5, wherein the film is selected from an alkylbenzene sulfonate, an alkyl sulfonate, and a modified product thereof. 7. The laminated film according to claim 1, wherein the crosslinked modified layer has a molecular orientation. 8. The laminated film according to claim 1, wherein the degree of molecular orientation of the crosslinked modified layer is 0.02 to 0.40.