JP2001213985A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film which has excellent adhesion to a functional layer even in use under severe conditions and, simultaneously, excellent dimension stability, and has excellent adhesion to an ink layer and dimension stability of a substrate upon printing, particularly when used in heat-sensitive transfer recording materials and can obtain transferred images having excellent gradation. SOLUTION: The polyester film has a surface orientation of 0.176-0.300 and a coating layer obtained by coating a coating fluid containing a thermoplastic resin on at least one side of the polyester film, drying the coated film, stretching it, and further subjecting the stretched film to heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polyester film. More specifically, the present invention is a polyester film having a specific degree of plane orientation and a specific coating layer,
The present invention relates to a polyester film which has excellent adhesion to various functional layers when heated to a high temperature and has a small dimensional change.

[0002]

2. Description of the Related Art Polyester films have excellent properties such as mechanical properties, dimensional stability, and heat resistance. Therefore, they are used for magnetic recording materials such as magnetic cards and magnetic tapes, and for packaging materials, photographic materials, printing materials and the like. Widely used for general industrial materials.

In these applications, a polyester film is provided on its surface with, for example, a thermal transfer layer of a thermal transfer recording material,
A functional layer such as an ink layer of a printing material, a photosensitive layer of a photographic film, a magnetic layer of a magnetic card, a magnetic tape, or a magnetic disk is laminated and used.

The surface of a polyester film is highly oriented and crystallized and has poor adhesion. For example, even if the above-mentioned functional layer is directly applied, it hardly adheres. In order to improve this, the surface of the polyester film is usually subjected to a primer treatment in which a resin such as polyester, acrylic or urethane is applied as an easy-adhesion layer. Used for

[0005] In recent years, polyester films having a functional layer laminated thereon are often used under severer conditions than in the past, and the required characteristics have become higher. For example, the thickness of the film is required to be thinner, and the dimensional change is required to be stable even at a higher temperature than before.

One of the uses of the polyester film is as a base film of a thermal transfer recording material. Thermal transfer recording includes a fusion type thermal transfer recording system and a sublimation type thermal transfer recording system. The former thermal transfer recording method is mainly used for bar codes and faxes, and uses a thermal transfer sheet having an ink layer made of a heat-fusible material containing a colorant. The latter sublimation type thermal transfer recording system is in great demand as a recording system capable of easily outputting a high-quality full-color image, and a thermal transfer sheet having an ink layer containing a thermosublimable dye is used.

However, in recent years, high-speed printing has been promoted in thermal transfer recording, and higher temperatures and tensions are instantaneously applied to a transfer recording material than in the past. At this time,
The following problems occur in the thermal transfer sheet using the base film of the related art.

That is, when forming an image, the thermal transfer sheet is heated to melt the ink layer in the case of the fusion type, and is heated to sublimate the sublimable dye in the case of the sublimation type. At this time, if the adhesiveness between the ink layer and the base film is poor, in the case of the melt type, extra transfer is performed to portions other than the portion to be transferred, and in the case of the sublimation type, the entire ink binder is transferred. This lack of adhesion is caused by insufficient heat resistance of the easy-adhesion layer, but also caused by minute dimensional changes due to elongation, shrinkage, and wrinkles of the polyester film as a substrate. Further, deformation of the polyester film when heated not only causes poor adhesion to the ink layer, but also causes insufficient color density and gradation of the printed image receiving body.

[0009]

SUMMARY OF THE INVENTION The present invention solves these problems and has excellent adhesion to a functional layer and excellent dimensional stability even when used under severer conditions than in the past. When used as a recording material, the adhesiveness between the ink layer and the film for melting and sublimation type thermal transfer printing is good, the dimensional stability of the substrate during printing is excellent, and the gradation is excellent. It is intended to provide a polyester film from which a transfer image can be obtained.

[0010]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventor has found that a polyester film having specific physical properties and provided with a specific coating layer is used as a base material. And found that the problem could be solved, and completed the invention.

An object of the present invention is to apply a coating liquid containing a thermoplastic resin to at least one side of a polyester film,
It can be achieved by a polyester film provided with a coating layer obtained by performing drying, stretching and further heat treatment and having a degree of plane orientation in the range of 0.176 to 0.300.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

(Polyester) The polyester constituting the polyester film of the present invention is a linear saturated polyester comprising an aromatic dibasic acid component and a diol component.

Examples of the aromatic dibasic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, and 4,4'-diphenyldicarboxylic acid. Of these, terephthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferred because the polyester film has excellent mechanical and thermal properties.

Examples of the diol component include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, and 1,6-hexanediol. , Cyclohexanedimethanol, polyethylene glycol, polytetramethylene glycol and the like. Among these, ethylene glycol is particularly preferred because the mechanical properties of the polyester film are excellent.

As specific examples of the polyester in the present invention, polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4
-Cyclohexylene dimethylene terephthalate), polyethylene-2,6-naphthalate and the like. Among them, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferred because the properties of the polyester film are excellent. These polyesters are preferably homopolymers, but may be copolymers. Resins other than polyester can also be mixed in a small proportion.

The polyester used in the present invention contains an inorganic or organic lubricant such as silicon dioxide, calcium carbonate, kaolin, or silicone particles having a particle size of 0.1 to 5 μm.
It is preferable to add 3 to 3.0% by weight. The upper limit of the lubricant compounding ratio is more preferably 1.0% by weight, and the lower limit is preferably 0.1% by weight. By adding these lubricants, the center line roughness of the surface of the coating layer is reduced to 0.
A polyester film having a thickness of from 0.01 to 0.3 μm can be obtained. If the center line roughness of the surface of the coating layer is less than 0.01 μm, the film may have insufficient slipperiness. For example, when used for thermal transfer, the film may be wrinkled, or the thermal head may be stuck. It is not preferable because it may occur. In addition, the center line roughness of the surface is 0.
When it is larger than 3 μm, thermal conductivity during printing may be deteriorated, and a sufficient image may not be obtained.

The polyester used in the present invention may contain a stabilizer, a colorant, an antioxidant, and other additives as needed, so long as the original performance is not impaired.

(Polyester Film) The polyester film of the present invention has a degree of plane orientation (ΔP) of from 0.176 to 0.176.
It must be in the range of 0.300. For example, in thermal transfer printing, at the time of printing, a polyester film as a substrate receives printing heat while receiving tension in the vertical direction. Therefore, in order to increase the printing speed, a higher tension is applied, and the substrate receives an even higher energy of printing heat. If the degree of plane orientation is less than 0.176, the substrate cannot withstand a large tension, and the size of the substrate changes due to high-energy printing heat, making it difficult to print an excellent image. When the degree of plane orientation exceeds 0.300, the mechanical strength of the base material is increased, but the shrinkage of the base material is remarkable due to high-energy printing heat, and the excellent dimensions cannot be maintained, and an excellent image is printed. It becomes difficult.

In the case where the polyester is mainly composed of polyethylene terephthalate, the lower limit of the degree of plane orientation is preferably 0.170, more preferably 0.180. Further, the upper limit is preferably 0.250,
More preferably, it is 0.220. When the polyester is a substrate mainly composed of polyethylene-2,6-naphthalate, the lower limit of the degree of plane orientation is preferably 0.200, and more preferably 0.221. The upper limit is preferably 0.290, and more preferably 0.280.

The polyester film having the degree of plane orientation of the present invention can be obtained, for example, by forming a film as follows. The aforementioned polyester is melt-extruded into a film,
It is wound around a casting drum, cooled and solidified to form an unstretched film. This unstretched film is taken from Tg to (+6
0) The film is heated at 1 ° C. (Tg is the glass transition temperature of the polyester) and stretched once or twice or more in the longitudinal direction so that the total magnification becomes 3 to 7 times. Then Tg ~ (T
g + 60) ° C. and stretched so that the width direction becomes 3 to 5 times,
Next, heat treatment is performed at 200 to 250 ° C. for 0.1 to 10 seconds, and 0 to 20 ° C. lower than the heat treatment temperature in the width direction.
Re-heat treatment is performed while contracting by ~ 20% or elongating by ~ 10%.

The orientation state of the film is determined by the degree of polymerization of the polymer,
It can be arbitrarily controlled by the conditions of the stretching ratio, the stretching temperature, the stretching speed, the heat setting temperature, and the heat setting time, and from these conditions, the plane orientation degree (ΔP) of the polyester film is 0.17.
Select the one that is between 6 and 0.300. A polyester film having a degree of plane orientation (ΔP) in this range can be obtained, for example, by increasing the degree of polymerization of the polyester polymer to be used, increasing the stretching speed, or increasing the stretching ratio to the maximum.

The average refractive index (nav) of the polyester film is in the range of 1.600 to 1.610 for a substrate mainly composed of polyethylene terephthalate, and 1 for a substrate composed mainly of polyethylene-2,6-naphthalate. .6
It is preferably in the range of 60 to 1.680.

The polyester film birefringence (Δ
n) is in the range of 0.000 to 0.100 for a substrate mainly composed of polyethylene terephthalate,
0.100 for a substrate mainly composed of 2,6-naphthalate
The range is preferably from 0.300 to 0.300, which can be obtained by appropriately controlling the film forming conditions.

Further, the polyester film of the present invention comprises:
The degree of plane orientation is preferably in the range of 0.176 to 0.300, and the crystallinity (Xc) of the film is preferably 30% or more. Crystallinity of this polyester film (%)
Is a numerical value obtained from the density of the film, and is defined by the following formula (3) when the polyester is polyethylene terephthalate, and is defined by the following formula (4) when the polyester is polyethylene-2,6-naphthalate. . This value of Xc indicates that the lubricant content in the film is 3.
If it is 0% by weight or less, the value may be that of a film containing a lubricant, and if the thickness of the coating layer is 1 μm or less, it may be that of a film that contains a coating layer.

[0026]

Xc = 100 × (ρf-1.335) /0.120 (3) (In the equation (3), ρf represents the density (g / cm ³ ) of the film.)

[0027]

Xc = 100 × (ρf-1.325) /0.082 (4) (In the equation (3), ρf represents the density (g / cm ³ ) of the film.)

When the polyester is polyethylene terephthalate, the lower limit of the crystallinity (%) of the polyester film is preferably 40%, particularly preferably 50%, since the image of the thermal transfer printing becomes clear. When the polyester is polyethylene-2,6-naphthalate, the lower limit of the crystallinity (%) of the film is 35%.
%, And particularly preferably 40%, because the image of the thermal transfer printing becomes clear.

The polyester film of the present invention preferably has a thickness of 0.5 to 10 μm. The upper limit of the thickness is more preferably 5 μm, and the lower limit is more preferably 1 μm. In recent years, there has been a demand for thinner films due to downsizing of printing equipment and speeding up of printing. When the thickness of the film is more than 10 μm, the thermal conductivity at the time of printing deteriorates, and high-speed printing cannot be performed.

The polyester film used in the present invention preferably has a thickness unevenness in the longitudinal direction and the width direction of 0 to 10%. When the thickness unevenness is more than 10%, the back layer and the ink layer cannot be uniformly applied, and the running property at the time of printing and the resolution of printing deteriorate.

(Thermoplastic resin) In the present invention, the thermoplastic resin forming the coating layer is dispersible in water (water-dispersible).
Alternatively, it is a thermoplastic resin soluble in water (water-soluble) or a thermoplastic resin soluble in a solvent. Examples of such a thermoplastic resin include, for example, an acrylic resin, a polyester resin, an acryl-modified polyester resin, a polyurethane resin, a polysiloxane resin, an epoxy resin, a polyether resin, a vinyl resin, a cellulose resin, Examples thereof include polyolefin-based resins, antistatic resins, and gelatins. One or more of these resins can be used. Among these resins, a water-dispersible or water-soluble (hereinafter, sometimes referred to as "aqueous") thermoplastic resin is particularly preferable because the coating layer can be coated with an aqueous coating solution.

(Acrylic Resin) In the present invention, the acrylic resin is a polymer or a copolymer containing an acrylic monomer as a main component. Acrylic resins include, for example, ethyl acrylate, methyl acrylate, acrylic acid, butyl acrylate, sodium acrylate, ammonium acrylate, ethyl methacrylate, methyl methacrylate, methacrylic acid, butyl methacrylate, glycidyl methacrylate, Hydroxyethyl acrylate, acrylamide, methacrylamide, N-methoxymethyl acrylamide, N-methylol acrylamide and other polymers or copolymers containing an acrylic monomer as a main component and having a number average molecular weight of 5,000 to Preferred is 250,000.

The acrylic monomers include alkyl acrylates and alkyl methacrylates (the alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl,
-Ethylhexyl group, cyclohexyl group, etc.); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2
Hydroxy-containing monomers such as hydroxypropyl methacrylate; epoxy-containing monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether; acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, crotonic acid and salts thereof (sodium salt, Monomers containing a carboxy group or a salt thereof such as potassium salt, ammonium salt, tertiary amine salt, etc .; acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N, N-dialkylacrylamide, N, N-dialkyl methacrylate (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-
Butyl, isobutyl, t-butyl, 2-ethylhexyl, cyclohexyl, etc.), N-alkoxyacrylamide, N-alkoxymethacrylamide, N, N
-Dialkoxyacrylamide, N, N-dialkoxymethacrylamide (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), acryloylmorpholine, N-methylolacrylamide, N-methylolmethacrylamide, N-phenyl Examples include monomers containing an amide group such as acrylamide and N-phenylmethacrylamide. Copolymerization can be carried out using two or more of these monomers.

The monomers which can be used as a copolymer component of the acrylic resin include vinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, sodium styrene sulfonate, vinyl methyl ether, vinyl ethyl ether, and vinyl trialkoxy. Examples include monomers such as silane, vinylidene chloride, ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ether, sodium vinyl sulfonate, butadiene, and sodium methacrylate.

The acrylic resin is preferably a resin containing alkyl acrylate or alkyl methacrylate as a main component. The component is 30 to 90 mol%, and is a copolymerizable vinyl monomer component 70 having a functional group. It is preferably a water-soluble or water-dispersible resin containing from 10 to 10 mol%. Vinyl monomers having a functional group copolymerizable with an alkyl acrylate or an alkyl methacrylate have a carboxyl group or a salt thereof, an acid anhydride group, a sulfonic acid group or a salt thereof, an amide group or an alkylol group as a functional group. It is a vinyl monomer having an amide group, an amino group (including a substituted amino group) or an alkylolated amino group or a salt thereof, a hydroxyl group, an epoxy group and the like. Of these, particularly preferred are a carboxyl group or a salt thereof, an acid anhydride group, an epoxy group and the like. Two or more of these groups may be contained in the resin. Examples of the alkyl group of the alkyl acrylate and the alkyl methacrylate include a methyl group, an ethyl group, an n-propyl group, an isopropyl group,
-Butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, cyclohexyl group and the like.

(Polyester Resin) In the present invention,
The polyester resin is a linear polyester comprising a polybasic acid component and a polyol component, and has a number average molecular weight of 5,0.
The thing of 00-25,000 is preferable.

The polybasic acid component includes terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,
4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid,
-Sodium sulfoisophthalic acid, dodecanedicarboxylic acid, hexahydroterephthalic acid and the like. Two or more of these acid components can be used. It is also possible to use a small amount of an unsaturated polybasic acid component such as maleic acid, itaconic acid or the like and hydroxycarboxylic acid such as p-hydroxybenzoic acid.

The polyol components include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6 -Hexanediol, dipropylene glycol, triethylene glycol, bisphenol A-alkylene oxide adduct, hydrogenated bisphenol A-alkylene oxide adduct, 1,
Examples thereof include 4-cyclohexanedimethanol, polyethylene glycol, and polytetramethylene glycol.

A component having a sulfonate group can be copolymerized with the polyester resin in order to impart hydrophilicity. It is preferable to impart hydrophilicity to the polyester-based resin because the dispersibility in the aqueous coating liquid is improved when a thin film is laminated using the aqueous coating liquid. Such components include, for example, 5-Na sulfoisophthalic acid, 5-K sulfoisophthalic acid, and the like.

The polyester resin may be obtained by copolymerizing a small amount (for example, 5 mol% or less) of a trifunctional or higher polyvalent carboxylic acid component and a polyol component within a range in which a substantially linear polymer is obtained. Examples of such trifunctional or higher polyvalent carboxylic acids include trimellitic acid, pyromellitic acid, and dimethylolpropionic acid, and examples of polyols include glycerin and trimethylolpropane.

(Acrylic-modified polyester-based resin) The acrylic-modified polyester-based resin is prepared by mixing ethyl acrylate, methyl acrylate, acrylic acid, butyl acrylate, sodium acrylate, ammonium acrylate, and ethyl methacrylate in the presence of the polyester resin. , Methyl methacrylate, methacrylic acid, butyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate,
It is a copolymer made by polymerizing acrylic monomers represented by acrylamide, methacrylamide, N-methoxymethylacrylamide, N-methylolacrylamide, etc., and has a number average molecular weight of 5,000 to 250,000.
0 is preferred.

The acrylic-modified polyester resin is styrene, α-methylstyrene, sodium styrenesulfonate,
It may contain a monomer such as vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ether, sodium vinyl sulfonate and sodium methacrylate as a copolymer component.

(Polyurethane Resin) The polyurethane resin is a polymer or copolymer obtained from a polyvalent isocyanate compound and a polyvalent hydroxy compound, and preferably has a number average molecular weight of 5,000 to 25,000. .

Examples of components constituting the urethane resin include the following polyvalent hydroxy compounds, polyvalent isocyanate compounds, chain extenders, crosslinking agents, and the like. That is, as the polyvalent hydroxy compound, polyoxyethylene glycol, polyoxypropylene glycol, polyethers such as polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polyesters such as polycaprolactone, polycarbonates, Acrylic polyols, castor oil, and the like can be used. As the polyvalent isocyanate compound, tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and the like can be used. Examples of the chain extender or crosslinking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, ethylenediamine-sodium acrylate adduct, 4,4'-diaminodiphenylmethane, and 4,4'-
Diaminodicyclohexylmethane, water and the like can be used. From these compounds, one or more can be appropriately selected, and a polyurethane resin can be synthesized by a usual polycondensation-crosslinking reaction. Among these, for example, diisocyanates, polyethers, polyesters,
A urethane-based resin in the form of an emulsion or an aqueous solution, which is obtained by using glycol, diamine, dimethylolpropionate, or the like, is particularly preferable.

(Polysiloxane Resin) The polysiloxane resin is a condensate of a silane coupling agent or a polymer having a linear or network structure having a siloxane bond in a molecule such as dimethylpolysiloxane.

(Epoxy resin) Epoxy resin is
It is a polymer or a copolymer obtained from a compound having an epoxy group, and preferably has a number average molecular weight of 150 to 30,000. As the compound having an epoxy group,
For example, bisphenol glycidyl ether, glycerin polyglycidyl ether, aminoglycidyl ether and the like can be mentioned.

(Polyether-based resin) The polyether-based resin is a polymer or a copolymer having an ether bond (—CO—C—) in the skeleton, such as polyethylene oxide, polypropylene oxide, and phenoxy resin. And the like, and the number average molecular weight is 800 to
Particularly preferred is 400,000.

(Vinyl Resin) A vinyl resin is a polymer or a copolymer obtained by addition polymerization of a monomer having an unsaturated bond in the molecule (vinyl compound). Aqueous polymers or copolymers such as butyral and polyvinyl acetate can be mentioned as preferred examples.

(Cellulose-based resin) Cellulose-based resin is a resin having a cellulose structure in the molecule. For example, aqueous polymers such as cellulose ethers such as methyl cellulose and cellulose esters such as cellulose acetate and nitrocellulose. Alternatively, a copolymer can be mentioned as a preferable example.

(Gelatins) Gelatins are high molecular weight polypeptides, and preferred examples include those obtained from protein raw materials such as collagen.

(Polyolefin resin) Examples of the polyolefin resin include polyethylene, polypropylene, and polybutadiene. Among them, water-dispersible polybutadiene and a copolymer thereof are preferable.

(Antistatic Resin) Antistatic resins include antistatic resins such as a polymer having a quaternary amine salt cation in a molecule, a polymer having a sulfonate in a molecule or a polymer having a phosphate in a molecule. Is a polymer having Examples of such a polymer include sodium polystyrene sulfonate, sodium polyisoprene sulfonate, a polyacrylate polymer having an alkyl phosphate Na base in the molecule, and a quaternary polyalkylamine / alkyl sulfate base-substituted acrylamide / ethylene copolymer. And the like, and the number average molecular weight is 2,000 to 70,
000 is preferred.

These resins can be used alone or in combination.

The thermoplastic resin of the present invention is particularly preferable because the acrylic resin and the polyester resin are excellent in the adhesiveness to the polyester film and the adhesiveness to the functional layer.

(Crosslinking Agent) It is preferable that a crosslinking agent is added to the coating layer in the present invention together with the above-mentioned thermoplastic resin, because the cohesive force of the coating layer is improved and the heat resistance during printing is improved. Examples of the crosslinking agent include an isocyanate compound, an epoxy compound, an oxazoline compound, and a melamine compound. One or more of these crosslinking agents can be added.

(Isocyanate compound) Examples of the isocyanate compound used as a crosslinking agent include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6-diisocyanate, and 1,6-diisocyanate. Hexane, adduct of tolylene diisocyanate and hexanetriol, adduct of tolylene diisocyanate and trimethylolpropane, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 5-naphthalenediisocyanate, 3,3'-vitrilen-4,4
'-Diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, metaphenylene diisocyanate and the like.

(Epoxy Compound) Examples of the epoxy compound used as a crosslinking agent include polyepoxy compounds,
Examples include diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like.Examples of polyepoxy compounds include sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, and triglyceride. Glycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, etc., and as the diepoxy compound, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcindi Glycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, Pyrene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, etc., as monoepoxy compounds, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidylamine compounds as N , N, N ', N',-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like.

(Oxazoline Compound) As the oxazoline compound used as the crosslinking agent, a polymer containing an oxazoline group is preferable, and these can be prepared by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with another monomer. Examples of the addition-polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isopropenyl-2-oxazoline. , 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is easily available industrially and is preferable. The other monomer is not limited as long as it is a monomer copolymerizable with an addition-polymerizable oxazoline group-containing monomer, and examples thereof include an alkyl acrylate and an alkyl methacrylate (as the alkyl group, a methyl group,
A (meth) acrylic acid esters such as ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itacone Unsaturated carboxylic acids such as acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated carboxylic acids such as acrylonitrile and methacrylonitrile Nitriles; acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,
N-dialkylacrylamide, N, N-dialkyl methacrylate (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,
Isobutyl group, t-butyl group, 2-ethylhexyl group,
Unsaturated amides such as cyclohexyl group); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene;
Halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene; One or more monomers can be used.

(Melamine Compound) Examples of the melamine compound used as a crosslinking agent include compounds obtained by reacting a methylol melamine derivative obtained by condensing melamine and formaldehyde with lower alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, etc. Mixtures thereof are preferred. As methylol melamine derivatives, for example, monomethylol melamine,
Examples include dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine.

(Coating Layer) The coating layer in the present invention is obtained by applying a coating liquid containing a thermoplastic resin to at least one surface of a polyester film, followed by drying, stretching and heat treatment. This coating layer is necessary for improving the adhesion between the functional layer such as the ink layer and the polyester film. In order to improve the adhesiveness to the ink layer, particularly to the ink layer for thermal transfer, the mixture composition ratio of the acrylic resin (A) and the polyester resin (B) in the coating layer is expressed by the formula (1). , (2). Acrylic resin (A) and polyester resin (B)
Is particularly preferably an aqueous resin.

[0061]

10% by weight <A <90% by weight Formula (1) 10% by weight <B <90% by weight Formula (2)

When the acrylic resin in the coating layer is less than 10% by weight, or when the polyester resin in the coating layer is less than 90% by weight.
If the content exceeds the weight percentage, the adhesion between the ink layer and the coating layer may be insufficient. When the amount of the polyester resin in the coating layer is less than 10% by weight or when the amount of the acrylic resin in the coating layer exceeds 90% by weight, the adhesiveness between the substrate and the coating layer may be insufficient. The flexibility of the coating layer may be insufficient. In any case, when the polyester film of the present invention is used for thermal transfer, excellent images may not be obtained.

The thickness of the coating layer in the present invention is 0.00
A range of 1 to 1 μm is preferred. The lower limit of the thickness is 0.01
μm is more preferable, and the upper limit is more preferably 0.5 μm. The thickness of the coating layer is 0.001 to
When the thickness is in the range of 1 μm, the adhesion between the coating layer and the polyester film is improved, and blocking is less likely to occur when the film coated with the coating layer is rolled.

The center line average roughness of the coating layer surface in the present invention is preferably in the range of 0.01 to 0.3 μm. The center line average roughness of the coating layer surface is 0.01 to
By setting the range of 0.3 μm, it is possible to improve the slipperiness of the film provided with the coating layer, and when the polyester film of the present invention is used for thermal transfer, excellent images can be obtained. Obtainable.

(Coating liquid) In the present invention, the coating liquid used for coating the coating layer may be a thermoplastic resin such as an aqueous solution or a solvent solution in which the thermoplastic resin is dissolved or an aqueous dispersion in which the thermoplastic resin is dispersed. Any material may be used as long as it can be uniformly applied to the surface of the polyester film, but is preferably an aqueous solution or an aqueous dispersion (aqueous coating liquid).

When the coating liquid is an aqueous coating liquid, it may contain some organic solvent as long as it does not affect other additives. This aqueous coating liquid can be used by adding a required amount of a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant.

As such surfactants, those which can lower the surface tension of the aqueous coating liquid to 40 mN / m or less and promote the wetting of the polyester film are preferable. For example, polyoxyethylene-fatty acid esters, sorbitan fatty acid esters, glycerin fatty acid Esters, fatty acid metal soaps, alkyl sulfates, alkyl sulfonates, alkyl sulfosuccinates, quaternary ammonium chloride salts, alkylamine hydrochlorides, betaine surfactants and the like can be mentioned. Further, other additives such as an antistatic agent, an ultraviolet absorber, a pigment, an organic filler, an inorganic filler, a lubricant, and an anti-blocking agent can be used together within a range that does not cause the effects of the present invention to be eliminated.

(Coating of Coating Layer) In the present invention, a coating liquid containing a thermoplastic resin is applied to at least one side of the polyester film, and dried, stretched, and further subjected to heat treatment to form a coating layer. This coating liquid is preferably applied to one or both sides of the polyester film before the crystal orientation is completed in the polyester film production process. Coating may be performed separately from the polyester film manufacturing process, but in this case, dust, dust, etc. are easily entangled, the portion becomes a defect at the time of printing, a clean atmosphere is desirable, and a suitable film is relatively inexpensive. From these points, coating during the manufacturing process is preferred. At that time, the solid content concentration of the coating solution is usually 0.1 to 30% by weight, more preferably 1 to 30% by weight.
-10% by weight. Coating amount is 1m ^{2 of} running film
0.5 to 50 g per unit is preferred.

A known method can be applied as a coating method. For example, roll coating, gravure coating, roll brushing, spray coating, air knife,
An impregnation method, a curtain coating method, or the like may be applied alone or in combination.

[0070]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Each characteristic value was measured by the following method.

1. Plane orientation degree (ΔP) Using an Abbe refractometer, the maximum value nx of the refractive index in the film plane, the refractive index ny in a direction perpendicular thereto, and the refractive index nz in the thickness direction of the film were measured, and the following formula ( 5) Calculate the degree of plane orientation from: The refractive index was measured using sodium D
Line (589 nm), using methylene iodide or a mixture of methylene iodide and sulfur as the mounting solution,
Measured at 3 ° C. and 65% RH.

[0072]

ΔP = [(nx + ny) / 2] −nz (5)

2. Birefringence (Δn) As in the case of the degree of plane orientation, the maximum value nx of the refractive index in the film plane, the refractive index ny in the direction perpendicular thereto, and the refractive index nz in the thickness direction of the film were measured, and (6) The birefringence is calculated from the above.

[0074]

Δn = nx−nz (6)

3. Average refractive index (nav) As in the case of the plane orientation degree, the maximum value nx of the refractive index in the film plane, the refractive index ny in the direction perpendicular thereto, and the refractive index nz in the thickness direction of the film are measured, and the following formula is obtained. The average refractive index is calculated from (7).

[0076]

[Mathematical formula-see original document] nav = (nx + ny + nz) / 3 (7)

4. Density The density was measured by a floatation / sedimentation method at 25 ° C. in a density gradient tube using an aqueous solution of calcium nitrate.

5. Glass transition temperature (Tg) It was measured using a DSC (differential scanning calorimeter) manufactured by PerkinElmer. The measuring method is as follows. Sample 10m
g was set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then quenched in liquid nitrogen. This quenched sample is
The temperature was raised at a rate of ° C./min, and the temperature at the center of the region where the discontinuity appeared in the baseline was defined as Tg.

6. Film Thickness The film is cut into a length and width of 10 cm, its weight is measured and calculated from the density of the polyester.

7. The thickness of the coating layer is calculated from the coating amount per 1 m ^{2 of the} coating solution and the solid content concentration.

8. Centerline Surface Roughness (Ra) Measurement is performed according to the method described in JIS B0601-1976, and the measurement is performed using a surface roughness meter SE- manufactured by Kosaka Laboratory Co., Ltd.
3F was used. Under the conditions of a stylus diameter of 2 μm, a stylus weight of 30 mg, a cut-off value of 0.08 mm, and a measurement length of 2.5 mm, a center line average roughness was obtained, and this was performed at 12 measurement points.
Among these, the maximum value and the minimum value are respectively cut, and the average value of 10 points is obtained and set as Ra.

9. Adhesiveness and clarity A "back layer" is formed on the opposite side of the film
Thereafter, an “ink layer” was formed on the surface of the easily adhesive layer to prepare a thermal transfer material. Using the thermal transfer material, a fusion / sublimation thermal transfer type full-color printer (“ColorPoint 1820PS” manufactured by Seiko Instruments Inc.)
J "), solid printing with a width of 15 cm and a length of 25 cm was performed at the center of A4 size image receiving paper. The state of abnormal transfer of the ink layer and the sharpness of the image were visually observed and evaluated as follows. (9-1) Adhesion ；: Abnormal transfer of ink layer not at all △: Abnormal transfer of ink layer is less than 1% ×: Abnormal transfer of ink layer is 1% or more and less than 10% XX; Abnormal transfer of ink layer 10% or more (9-2) Sharpness A: Image is extremely clear O: Image is clear Δ: Image is partially unclear X: Image is half or more unclear

"Back Layer" Coating solution for back layer 3% by weight of amino-modified silicone, 2% by weight of epoxy-modified silicone, 95% by weight of solvent (ethanol / isopropyl alcohol = 1/1) Coating conditions: 0.5 g / dry m ² and dried at 80 ° C. for 1 minute.

"Ink layer" Coating solution for ink layer for fusion-type thermal transfer 35% by weight of phthalocyanine blue, 25% by weight of α-olein / maleic anhydride copolymer wax (melting point 72 ° C.), 35% by weight of paraffin wax (melting point 70 ° C.) %, Ethylene / vinyl acetate copolymer (softening point 78 ° C)
5% by weight Coating conditions: Coating was carried out by a hot melt method to 0.6 g / m ² . -Sublimation type thermal transfer ink layer coating solution KST-B-136 (sublimation dye Nippon Kayaku Co., Ltd. product name) 4% by weight, polyvinyl acetoacetal Sekisui Chemical Co., Ltd. product name 6% by weight, solvent ( (Methyl ethyl ketone / toluene = 1/1) 90% by weight Coating conditions: Coating in dry state to 1 g / m ² , 8
Dry at 0 ° C. for 1 minute.

[Examples 1 and 2] o- at 25 ° C.
Intrinsic viscosity measured in chlorophenol 0.61 dl /
g of polyethylene terephthalate (containing lubricant, Tg = 7)
8 ° C.) was extruded from a T-die and rapidly cooled while applying static electricity on a rotating cooling drum maintained at about 40 ° C. to obtain an unstretched film. Then, the unstretched film is heated at 115 ° C.
And stretched 4.2 times in the longitudinal direction to obtain a uniaxially stretched film. One side of the uniaxially stretched film was selected from the coating solutions shown in Table 1 and coated with a coating solution having a solid content of 4% by weight by a kiss coating method at 2 g / m ² . Then 115
Biaxially oriented polyester with a thickness of 4.5 μm, stretched 3.8 times in the width direction at 200 ° C., subjected to a tension heat treatment at 220 ° C. with a fixed length, and reheated at 210 ° C. while elongating 2% in the width direction. A film was obtained. Table 2 shows the physical properties of the film and the evaluation results.

Example 3 Polyethylene-2 having an intrinsic viscosity of 0.63 measured in o-chlorophenol at 25 ° C.
6-Naphthalate (containing a lubricant, Tg = 121 ° C.) was extruded from a T-die and quenched while applying static electricity on a rotating cooling drum maintained at about 40 ° C. to obtain an unstretched film. Next, the unstretched film was stretched 4.5 times in the longitudinal direction at 135 ° C. to obtain a uniaxially stretched film. One side of the uniaxially stretched film was selected from the coating solutions shown in Table 1 and coated with a coating solution having a solid content of 4% by weight by a kiss coating method at 2 g / m ² . Next, the film is stretched 4.0 times in the width direction at 140 ° C., subjected to a tension heat treatment at 235 ° C. with a fixed length, and re-heat treated at 230 ° C. while being stretched by 2% in the width direction, to obtain a 4.5 μm-thick double An axially oriented polyester film was obtained. Table 2 shows the physical properties of the film and the evaluation results.

[Comparative Example 1 and Comparative Example 2]
Polystyrene with intrinsic viscosity of 0.61 measured in chlorophenol
Ethylene terephthalate (containing lubricant, Tg = 78 ° C)
Extrude from a T-die and rotate at about 40 ° C
Unstretched film quenched while applying static electricity on a cooling drum
I got Next, the unstretched film is stretched at 115 ° C.
The film was stretched 4.2 times in the same direction to obtain a uniaxially stretched film. This one
On one side of the axially stretched film, the coating solution shown in
And apply the coating solution with a solid content of 4% by weight to Kisco.
2 g / m by the plate method ^TwoCoated. Next, at 120 ° C in the width direction
Stretched 3.8 times and subjected to a tension heat treatment at 220 ° C with a fixed length.
Heat treatment at 215 ° C while shrinking 6% in the width direction.
A 4.5 μm thick biaxially oriented polyester film
Got Lum. Table 2 shows the physical properties of the film and the evaluation results.
You.

Comparative Example 3 A biaxially oriented polyester film was obtained in the same manner as in Example 1, except that the easy adhesion layer was not applied. Table 2 shows the physical properties of the film and the evaluation results.

[0089]

[Table 1]

The compositions of the resins in Table 1 are as follows. Acrylic resin: composed of 75 mol% of methyl methacrylate / 15 mol% of ethyl acrylate / 5 mol% of N-methylolacrylamide / 5 mol% of methacrylic acid. Polyester resin: 35 mol% of terephthalic acid / 9 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid / 46 mol% of ethylene glycol / 4 mol% of diethylene glycol. Crosslinking agent: 1,3-bis (N, N-diglycidylamine)
Cyclohexane Wetting agent: polyoxyethylene (n = 7) lauryl ether

[0091]

[Table 2]

[0092]

The polyester film of the present invention, when used as a substrate for thermal transfer, has good adhesiveness between the melt type and the ink layer for sublimation type thermal transfer printing, and has dimensional stability during printing. Because of good properties, an excellent image can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 201/00 C09D 201/00 (72) Inventor Satoshi Kitazawa 3-37-19 Koyama, Koyama Sagamihara-shi, Kanagawa 4F006 AA35 AB03 AB13 AB23 AB24 AB33 AB34 AB35 AB37 AB39 AB55 AB64 AB65 BA01 CA01 CA02 CA03 CA07 CA10 4F071 AA09 AA14 AA28 AA31 AA42 AA43 AA51 AA53 AA67 AA70 AA80 AAB AF BC16 BC17 4J002 AB02W AB03W AC11W AD01W BB03W BB12W BC12W BE02W BE06W BG04W BG04X BG07W BG12W BL01W BQ003 CD01W CD013 CD05W CD13W CF04W CF061 CF07W CF08W CF27W CH02W CH08W CK02W CP03W EL026 EN036 ER006 EU186 FD143 FD146 GG02 GP03 GS01 HA04 4J038 BA021 BA181 CB001 CD001 CG001 CG002 DA162 DB001 DB002 DD001 DD002 DF001 DG001 DG262 DL031 KA03 MA08 MA10 NA12 PB11 PC 08

Claims (10)

[Claims] 1. A coating film obtained by applying a coating liquid containing a thermoplastic resin on at least one surface of a polyester film, and performing drying, stretching, and further heat treatment, wherein the degree of plane orientation is 0.176 to 0.1. A polyester film having a range of 300. 2. The polyester film according to claim 1, wherein the polyester has a crystallinity of 30% or more. 3. The thermoplastic resin is an acrylic resin, a polyester resin, an acryl-modified polyester resin, a polyurethane resin, a polysiloxane resin, an epoxy resin, a polyether resin, a vinyl resin, a cellulose resin, gelatin. The polyester film according to claim 1, wherein the polyester film is at least one resin selected from the group consisting of a polyolefin resin, a polyolefin resin, and an antistatic resin. 4. The polyester film according to claim 1, wherein the thermoplastic resin is a water-soluble or water-dispersible resin, and the coating liquid is an aqueous coating liquid. 5. The polyester film according to claim 1, wherein the composition ratio of the resin in the coating layer is in the range of the following formulas (1) and (2). 10% by weight <A <90% by weight Formula (1) 10% by weight <B <90% by weight Formula (2) (wherein A is the weight% of the acrylic resin in the coating layer,
In the formula (2), B is% by weight of the polyester resin in the coating layer.
Represents ) 6. The polyester film according to claim 1, wherein the coating liquid contains a thermoplastic resin and a crosslinking agent. 7. The polyester film according to claim 6, wherein the crosslinking agent is at least one selected from the group consisting of an isocyanate compound, an epoxy compound, an oxazoline compound, and a melamine compound. 8. The polyester film according to claim 1, wherein the thickness of the coating layer is in the range of 0.001 to 1 μm. 9. The coating layer surface has a center line average roughness of 0.01.
The polyester film according to any one of claims 1 to 8, wherein the polyester film has a thickness of from 0.3 to 0.3 µm. 10. The polyester film according to claim 1, which is used as a base film of a thermal transfer recording material.