JP2002127621A - Laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated film for thermal transfer, excellent in bonding property to an ink layer as well as stability in dimension even when the film is used under a severe condition and good in the bonding property to the ink layer of either one of melting type or sublimation type. SOLUTION: The laminated film is constituted of a biaxially oriented polyester film having a surface orientation degree within 0.178-0.300 and an easily adhesive layer formed on at least one side of the biaxially oriented polyester film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laminated film for thermal transfer and its use as a base film for a thermal transfer recording medium. More specifically, in a thermal recording medium,
The present invention relates to a laminated base film for thermal transfer, which has good adhesion to an ink layer, has excellent dimensional stability at the time of printing, and gives a transferred image having excellent gradation.

[0002]

2. Description of the Related Art 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.

[0003] Japanese Patent Application Laid-Open No. Hei 8-104064 discloses that an aqueous solution or a water-dispersible resin of urethane, polyester and acrylic is applied to at least one surface of a film before completion of orientation crystallization, and then dried, stretched and heat-set. A biaxially oriented polyester film for sublimation type thermal transfer having a degree of plane orientation of 0.150 to 0.175, which has an applied coating layer, is disclosed.

[0004] According to the same publication, even if this film is printed in a large area exceeding the A4 size, wrinkles are hardly generated on the ink ribbon, and print defects are caused to deteriorate the quality of a printed image. And that the adhesiveness with the sublimable ink is improved.

In recent years, high-speed printing has been promoted in thermal transfer recording, and a higher temperature and tension are instantaneously applied to a transfer recording material as compared with the related art. At this time, the following problem occurs in the thermal transfer sheet using the conventional base film.

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.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laminated film for thermal transfer capable of providing a thermal transfer recording medium having good adhesion between an ink layer and a film.

Another object of the present invention is to provide an ink layer having excellent adhesiveness and dimensional stability even when used under severer conditions than before, and to provide the above-mentioned adhesive property to both the melt type and sublimation type ink layers. Is to provide a good laminated film for thermal transfer.

Still another object of the present invention is to provide a laminated film for a heat-sensitive transfer recording medium which has excellent dimensional stability at the time of printing and gives a transferred image having excellent gradation.

[0010] Still other objects and advantages of the present invention will become apparent from the following description.

[0011]

According to the present invention, the above objects and advantages of the present invention are as follows. First, the degree of plane orientation is 0.17.
A biaxially oriented polyester film having a thickness in the range of 8 to 0.300, and a laminated film for thermal transfer comprising an easily adhesive layer formed on at least one surface of the biaxially oriented polyester film (hereinafter, simply referred to as a laminated film). Is achieved by

According to the present invention, the above objects and advantages of the present invention are secondly achieved by using the above-mentioned laminated film of the present invention as a base film of a thermal transfer recording medium.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

(Polyester) The polyester constituting the biaxially oriented polyester film of the present invention is preferably 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 they give polyester films having 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 and polytetramethylene glycol. Among them, ethylene glycol is particularly preferable because it gives a polyester film having excellent mechanical properties.

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-naphthalenedicarboxylate and the like. Among them, polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are preferable because they give a polyester film having excellent characteristics. 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 has a particle size of 0.1.
1-5 μm of silicon dioxide, calcium carbonate, kaolin,
0.03 ~ inorganic or organic lubricant such as silicone particles
It is preferred to contain 3.0% by weight. The upper limit of the lubricant content is more preferably 1.0% by weight, and the lower limit is preferably 0.1% by weight. By containing these lubricants, a polyester film having a center line surface roughness of 0.01 to 0.3 μm on the surface of the coating layer can be obtained. The center line surface roughness of the coating layer surface is 0.01μ
If it is smaller than m, the film may have insufficient slipperiness. For example, when the film is used for thermal transfer, the film may be wrinkled or sticking of the thermal head may occur. On the other hand, when the center line surface roughness is larger than 0.3 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 coloring agent, an antioxidant, and other additives as needed, so long as the original performance is not impaired.

(Biaxially Oriented Polyester Film) The biaxially oriented polyester film has a degree of plane orientation (ΔP) of 0.1
It must be in the range of 78 to 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. For this reason, a higher tension is applied to increase the printing speed, and the substrate receives an even higher energy of printing heat. If the degree of plane orientation is less than 0.178, 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.

The preferred degree of plane orientation (ΔP) is 0.180.
０．３0.300.

In the case where the polyester is made of polyethylene terephthalate, the lower limit of the degree of plane orientation is preferably 0.180. Further, the upper limit is preferably 0.250, and more preferably 0.220. In the case where the polyester is made of polyethylene-2,6-naphthalenedicarboxylate, the lower limit of the degree of plane orientation is 0.2.
It is preferably 00, 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 and solidified by cooling to obtain an unstretched film. This unstretched film is taken from Tg to (Tg +
60) Heating to 1 ° C. (Tg is the glass transition temperature of the polyester) and stretching once or more times in the longitudinal direction so that the total magnification becomes 3 to 7 times. Then Tg ~
The film is stretched at (Tg + 60) ° C. so that the width direction becomes 3 to 5 times, and then heat-treated at 200 to 250 ° C. for 0.1 to 10 seconds, and then heat-treated at a temperature lower by 10 to 20 ° C. than the heat treatment temperature. Re-heat treatment is performed while contracting 0-20% or elongating 0-10%.

At the time of stretching, as described later, it is possible to provide an easily adhesive layer by applying a coating solution for forming an easily adhesive layer to an unstretched film or a uniaxially stretched film of a polyester film and then stretching. it can.

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. By the combination of these conditions, the degree of plane orientation of the polyester film (Δ
P) can be 0.178 to 0.300. A polyester film having a degree of plane orientation (ΔP) in this range:
For example, it can be obtained 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 (na) of the polyester film
v) is in the range of 1.600 to 1.610 for a substrate made of polyethylene terephthalate, and polyethylene-2,6
-For a substrate comprising naphthalene dicarboxylate:
It is preferably in the range of 660 to 1.680.

The birefringence of the polyester film (Δ
n) is in the range of 0.000 to 0.100 for a substrate made of polyethylene terephthalate, and polyethylene-2,6
-For a substrate comprising naphthalene dicarboxylate,
The range of 100 to 0.300 is preferred. Such a value of Δn can be obtained by appropriately controlling the film forming conditions.

Further, the biaxially oriented polyester film of the present invention has a degree of plane orientation in the range of 0.178 to 0.300 and a crystallinity (Xc) of the film of 30%.
It is preferable that it is above. The crystallinity (%) of this polyester film is a numerical value obtained from the density of the film. When the polyester is polyethylene terephthalate, the following formula (1) is used, and
In the case of 2,6-naphthalenedicarboxylate, it is defined by the following formula (2). This value of Xc is applied to a film containing a lubricant if the content of the lubricant in the film is 3.0% by weight or less, and a film containing the coating layer if the thickness of the coating layer is 1 μm or less. Also applies.

[0029]

Xc = 100 × (ρf-1.335) /0.120 (1) (In the formula (1), ρf represents the density (g / cm ³ ) of the film.)

[0030]

Xc = 100 × (ρf-1.325) /0.082 (2) (where ρf represents the density (g / cm ³ ) of the film in the equation (2)) When the polyester is polyethylene terephthalate, the lower limit of the crystallinity (%) of the oriented polyester film is preferably 40%, particularly preferably 50%, because the image of thermal transfer printing becomes clear. When the polyester is polyethylene-2,6-naphthalenedicarboxylate, the lower limit of the crystallinity (%) of the film is preferably 35%, particularly preferably 40%, because the image of the thermal transfer printing becomes clear.

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

The biaxially oriented polyester film used in the present invention preferably has uneven thickness in the longitudinal direction and the width direction in the range 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.

(Easy Adhesion Layer) The easy adhesion layer formed on at least one side of the biaxially oriented polyester film is preferably formed by applying a coating liquid containing a thermoplastic resin on at least one side of the biaxially oriented polyester film. Then, it can be obtained by performing drying, stretching and heat treatment.

In the present invention, the thermoplastic resin is preferably a water-dispersible (water-dispersible) or water-soluble (water-soluble) thermoplastic resin, or a thermoplastic resin soluble in a solvent. is there. Examples of such thermoplastic resins include acrylic resins, polyester resins, acrylic-modified polyester resins, polyurethane resins, polysiloxane resins, epoxy resins, polyether resins, vinyl resins, modified cellulose resins, polyolefin resins, and gelatins. Can be. These resins can be used alone or in combination of two or more. Among these resins, a water-dispersible or water-soluble (hereinafter, also 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 copolymer containing an acrylic monomer as a main component.

Examples of the acrylic monomer include alkyl acrylate and alkyl methacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl,
-Ethylhexyl group, lauryl group, stearyl group, cyclohexyl group, etc.); hydroxy-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; glycidyl acrylate, glycidyl methacrylate, Epoxy group-containing monomers such as allyl glycidyl ether;
Acrylic acid, methacrylic acid, maleic acid, itaconic acid,
Fumaric acid, crotonic acid and its salts (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, n
-Propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxyacrylamide, N-
Alkoxy methacrylamide, N, N-dialkoxyacrylamide, N, N-dialkoxymethacrylamide (methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), acryloylmorpholine, N-methylolacrylamide, N- Examples include monomers containing an amide group such as methylol methacrylamide, N-phenylacrylamide, and N-phenylmethacrylamide. Copolymerization can be carried out using two or more of these monomers.

Among these acrylic monomers, 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 are preferred.

As the acrylic resin, those using an alkyl acrylate or alkyl methacrylate as an acrylic monomer are particularly preferable. The content of the component is 30 to 90 mol%, and the other copolymerizable vinyl monomer component 70 to 1 is used.
It is preferably a water-soluble or water-dispersible resin containing 0 mol%.

Other vinyl monomers include, for example, vinyl isocyanate, allyl isocyanate, styrene, α
-Methylstyrene, sodium styrenesulfonate, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, vinylidene chloride, ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ether, sodium vinyl sulfonate, butadiene, sodium methacrylate And the like.

Other vinyl monomers include carboxyl groups or salts thereof, acid anhydride groups, sulfonic acid groups or salts thereof, amide groups or alkylolated amide groups, amino groups (substituted amino groups) as functional groups. Or a vinyl monomer having an alkylolated amino group or a salt thereof, a hydroxyl group, an epoxy group, or 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. The number average molecular weight of the acrylic resin is preferably from 5,000 to 250,000.

(Polyester Resin) In the present invention, the polyester resin is preferably a linear polyester comprising a polybasic acid component and a polyol component, and more preferably has a number average molecular weight of 5,000 to 25,000.

Examples of the polybasic acid component include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,
Examples thereof include 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid, 5-sodium sulfoisophthalic acid, dodecanedicarboxylic acid, and hexahydroterephthalic acid. Two or more of these acid components can be used. In addition, unsaturated polybasic acids such as maleic acid and itaconic acid and hydroxycarboxylic acids such as p-hydroxybenzoic acid can be used in a small amount.

Examples of the polyol component include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 6-hexanediol, dipropylene glycol, triethylene glycol, bisphenol A-alkylene oxide adduct, hydrogenated bisphenol A-alkylene oxide adduct, 1,4-cyclohexanedimethanol, polyethylene glycol, polytetramethylene glycol, and the like. Can be.

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 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 can be mentioned.

The polyester resin may be obtained by copolymerizing a trifunctional or higher polyvalent carboxylic acid component and a polyol component in a small amount (for example, 5 mol% or less) as long as the polymer becomes a substantially linear polymer. Such trifunctional or higher polycarboxylic acids include, for example, trimellitic acid, pyromellitic acid,
Dimethylolpropionic acid and the like. Examples of the polyol include glycerin and trimethylolpropane.

(Acrylic-Modified Polyester Resin) The acrylic-modified polyester resin is a copolymer produced by polymerizing an acrylic monomer or another monomer in the presence of a polyester. As the polyester, the same polyester as the polyester resin can be used.

Examples of the acrylic monomer include ethyl acrylate, methyl acrylate, acrylic acid, butyl acrylate, sodium acrylate, ammonium acrylate, ethyl methacrylate, methyl methacrylate, methacrylic acid, and methacrylic acid. Examples thereof include butyl, glycidyl methacrylate, 2-hydroxyethyl acrylate, acrylamide, methacrylamide, N-methoxymethylacrylamide, and N-methylolacrylamide.

Examples of other monomers include α-methylstyrene, sodium styrenesulfonate, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ether, sodium vinylsulfonate, sodium methacrylate and the like.

As the acrylic-modified polyester resin,
Those having a number average molecular weight of 5,000 to 250,000 are preferred.

(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 the components constituting the urethane resin include the following polyvalent hydroxy compounds, polyvalent isocyanate compounds, chain extenders, crosslinking agents, and the like. Examples of the polyhydroxy compound include polyethers such as polyoxyethylene glycol, polyoxypropylene glycol, and polyoxytetramethylene glycol; polyesters such as polyethylene adipate, polyethylene-butylene adipate, and polycaprolactone; polycarbonates; A system polyol and castor oil can be used. Examples of the polyvalent isocyanate compound include tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and isophorone diisocyanate. Examples of the chain extender or the crosslinking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, ethylenediamine-sodium acrylate adduct, 4,4′-diaminodiphenylmethane,
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. Of these, urethane resins in the form of an emulsion or an aqueous solution obtained by using, for example, diisocyanate, polyether, polyester, glycol, diamine, dimethylolpropionate, and the like are particularly preferable.

(Polysiloxane Resin) The polysiloxane resin is preferably 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) The epoxy resin is a polymer or copolymer obtained from a compound having an epoxy group, and preferably has a number average molecular weight of 150 to 30,000. Examples of the compound having an epoxy group include bisphenol glycidyl ether, glycerin polyglycidyl ether, and aminoglycidyl ether.

(Polyether Resin) The polyether resin is a polymer or a copolymer having an ether bond (—C—O—C—) in the skeleton. For example, polyethylene oxide, polypropylene oxide, phenoxy resin and the like are preferable. Can be mentioned. Number average molecular weight is 800 ~
Particularly preferred is 400,000.

(Vinyl resin) The vinyl resin is a polymer or copolymer obtained by addition polymerization of a monomer having an unsaturated bond in the molecule (vinyl compound). Examples of the vinyl resin include polyvinyl alcohol, polyvinyl butyral, and polyvinyl alcohol. A preferred example is an aqueous polymer or copolymer such as vinyl acetate.

(Cellulose Resin) Cellulose resin is a resin having a cellulose structure in the molecule, for example, an aqueous polymer such as cellulose ethers such as ethylcellulose, and cellulose esters such as triacetylcellulose and nitrocellulose. A polymer can be mentioned as a preferred example.

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

(Polyolefin resin) Examples of the polyolefin resin include polyethylene, polypropylene and polybutadiene. Of these, water-dispersed polybutadiene or a copolymer thereof is preferred.

These resins can be used alone or in combination.

(Thermoplastic resin) The thermoplastic resin in the present invention is particularly preferable because, among the above resins, an acrylic resin and a polyester resin are excellent in adhesion to a polyester film and adhesion to an ink layer. .

The proportion of the acrylic resin and the polyester resin is preferably 10 to 90% by weight of the acrylic resin and 90 to 10% by weight of the total weight of the acrylic resin and the polyester resin.

(Crosslinking Agent) In the easily adhesive layer in the present invention, it is preferable to use a crosslinking agent together with the above-mentioned thermoplastic resin. Thereby, 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. These crosslinking agents can be used alone or in combination of two or more.

(Isocyanate Compound) Examples of the isocyanate compound used as a crosslinking agent include tolylene diisocyanate and diphenylmethane-4,4'-
Diisocyanate, meta-xylylene diisocyanate,
Hexamethylene-1,6-diisocyanate, 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'-bitrylene-
4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, metaphenylene diisocyanate and the like can be mentioned.

(Epoxy Compound) Examples of the epoxy compound used as a crosslinking agent include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds. Examples of the polyepoxy compound include sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylol And propane polyglycidyl ether.
Examples of the diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. Glycidyl ether, polytetramethylene glycol diglycidyl ether and the like can be mentioned.
Examples of the monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether,
Phenylglycidyl ether and glycidylamine compounds include 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 a crosslinking agent, a polymer containing an oxazoline group is preferable, and these can be produced 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, 2
-Isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like. These can be used alone or in combination of two or more. Among these, 2-isopropenyl-2
-Oxazoline is easily available industrially and is preferred.
The other monomer is not limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline group-containing monomer. Specific examples thereof include an alkyl acrylate and an alkyl methacrylate (as the alkyl group, a methyl group, an ethyl group, n
-(Meth) acrylic esters such as -propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid And unsaturated carboxylic acids such as fumaric acid, crotonic acid, styrene sulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylamide , Methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N, N-dialkylacrylamide, N, N-dialkylmethacrylate (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 Unsaturated amides such as 2-ethylhexyl group and 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; vinyl chloride ,
Halogen-containing α, β- such as vinylidene chloride and vinyl fluoride
Unsaturated monomers; α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene; These other monomers can be used alone or in combination of two or more.

(Melamine compound) As the melamine compound used as a crosslinking agent, for example, a methylol melamine derivative obtained by condensing melamine and formaldehyde is etherified by reacting a lower alcohol such as methyl alcohol, ethyl alcohol, or isopropyl alcohol. Compounds and mixtures thereof are preferred. Examples of the methylol melamine derivative include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine and the like.

(Properties of Easy-Adhesion Layer) The easy-adhesion layer in the present invention is preferably prepared by applying a coating liquid containing the above-mentioned thermoplastic resin on at least one surface of a biaxially oriented polyester film, drying, stretching, It is obtained by further performing a heat treatment. This easily-adhesive layer is necessary for improving the adhesion between the ink layer and the polyester film. In order to improve the adhesiveness with the ink layer, particularly the ink layer for thermal transfer, it is necessary to use an acrylic resin and a polyester resin in combination, especially as described above.
It is preferable to use 0% by weight and 10 to 90% by weight of the polyester resin in combination.

10% by weight of acrylic resin in the easily adhesive layer
If it is less than 90%, or if the polyester resin in the easily adhesive layer exceeds 90% by weight, the adhesion between the ink layer and the easily adhesive layer may be insufficient. When the polyester resin in the easy-adhesion layer is less than 10% by weight or when the acrylic resin in the easy-adhesion layer exceeds 90% by weight, the adhesion between the base material and the easy-adhesion layer may be insufficient. And the flexibility of the easily adhesive layer may be insufficient. In any case, an excellent image may not be obtained.

In the present invention, the thickness of the easy-adhesion layer is 0.1.
The range of 001 to 1 μm is preferred. The lower limit of the thickness is 0.
More preferably, the upper limit is 0.5 μm.
More preferably, it is μm. By setting the thickness of the easily-adhesive layer to the range of 0.001 to 1 μm, the adhesion between the easily-adhesive layer and the polyester film is improved, and the film coated with the easily-adhesive layer is rolled. Blocking is less likely to occur.

In the present invention, the center line average surface roughness of the surface of the easily adhesive layer is preferably in the range of 0.01 to 0.3 μm. By setting the center line average surface roughness of the surface of the easily adhesive layer to a range of 0.01 to 0.3 μm,
It is possible to improve the slipperiness of the film provided with the easy-adhesive layer, and to obtain excellent images when the laminated film of the present invention is used for thermal transfer.

(Coating Liquid) In the present invention, the coating liquid used for coating the easily adhesive layer may be an aqueous solution or a solvent solution in which a thermoplastic resin is dissolved, or an aqueous dispersion in which the thermoplastic resin is dispersed. As long as the plastic resin can be uniformly applied to the surface of the polyester film, an aqueous solution or an aqueous dispersion (aqueous coating liquid) is preferable.

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 solution to 40 mN / m or less and promote the wetting of the polyester film are preferred. For example, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate, alkyl sulfonate, alkyl sulfosuccinate, quaternary ammonium chloride salt, alkylamine hydrochloride, betaine surfactant, etc. 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 Easy Adhesive Layer) In the present invention,
Preferably on at least one side of the polyester film,
A coating liquid containing a thermoplastic resin is applied, dried, stretched, and further subjected to a heat treatment to form an easily adhesive 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. The coating may be performed separately from the polyester film manufacturing process, but in this case, dust, dust and the like are easily entangled, and the portion becomes a defect at the time of printing, and a clean atmosphere is desirable. From these points, coating during the manufacturing process is preferred.
At that time, the solid content concentration of the coating solution is preferably 0.1 to 30.
%, More preferably 1 to 10% by weight. Film 1 m ² per in coating amounts running from 0.5 to 50
g 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.

(Use of Laminated Film) In the present invention, as understood from the above description, the laminated film of the present invention can be advantageously used as a base film of a thermal transfer recording medium. At that time, an ink layer is provided on the easily adhesive layer of the laminated film.

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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 of the present invention. Each characteristic value was measured by the following method.

1. Plane orientation degree (ΔP) (1-1) Plane orientation degree of laminated film Using Abbe refractometer, the maximum value nx of the refractive index in the plane of the laminated film, the refractive index ny in a direction perpendicular thereto, and the thickness of the film The refractive index nz in the direction is measured, and the degree of plane orientation is calculated from the following equation (3). The refractive index is measured at 23 ° C. and 65% RH using sodium D line (589 nm) and using methylene iodide or a mixture of methylene iodide and sulfur as the mounting liquid.

ΔP = [(nx + ny) / 2] −nz (3) (1-2) Surface Orientation of Single-Layer Film Except for not laminating the easily adhesive layer, the film-forming conditions of the laminated film and The degree of plane orientation of the single-layer film formed under the same conditions is measured by the same method as in the above (1-1).

2. Birefringence (Δn) As in the case of the degree of plane orientation, the maximum value nx of the refractive index in the plane of the laminated film or the single-layer film, the refractive index ny in the direction perpendicular thereto, and the refractive index nz in the thickness direction of the film. It measures and calculates a birefringence from the following formula (4).

(4) Δn = nx−nz (4) Average refractive index (nav) As in the case of the degree of plane orientation, the maximum value nx of the refractive index in the plane of the laminated film or the single-layer film, the refractive index ny in a direction perpendicular thereto, and the refractive index nz in the thickness direction of the film are calculated. The average refractive index is calculated from the following equation (5).

Nav = (nx + ny + nz) / 3 (5) Density The density was measured in a density gradient tube using an aqueous solution of calcium nitrate at 25 ° C. by a floatation method.

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 is raised at a rate of ° C./min, and the temperature at the midpoint of the region where the discontinuity appears in the baseline is 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 easily adhesive layer is calculated from the coating amount per 1 m ^{2 of the} coating solution and the solid content concentration.

8. Center line average surface roughness (Ra) Measurement was performed according to the method described in JIS B0601-1976, and the measurement was 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" was formed on the surface of the film opposite to the easily adhesive layer, and then an "ink layer" was formed on the easily adhesive layer surface to prepare a thermal transfer material. Using the heat-sensitive transfer material,
Sublimation type thermal transfer type full-color printer (ColorPoint 1820P manufactured by Seiko Instruments Inc.)
SJ "), solid printing of 15 cm in width and 25 cm in length 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 ○: No abnormal transfer of ink layer at all △: Abnormal transfer of ink layer less than 1% ×: Abnormal transfer of ink layer 1% or more and less than 10% XX: Ink layer Abnormal transfer of 10% or more (9-2) Sharpness ◎; Image is extremely clear ○; Image is clear △; Image is partially unclear ×; Image is half or more unclear “Back layer” ・ Back layer coating liquid Amino-modified silicone 3% by weight, 2% by weight of epoxy-modified silicone, 95% by weight of solvent (ethanol / isopropyl alcohol = 1/1) Coating conditions: Apply to dryness to 0.5 g / m ² and dry at 80 ° C. for 1 minute Let it.

"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 to 3 Polyethylene terephthalate (containing a lubricant, Tg = 78 ° C.) having an intrinsic viscosity of 0.61 dl / g measured in o-chlorophenol at 25 ° C.
It was extruded from a die and quenched while applying static electricity on a rotating cooling drum maintained at about 40 ° C. to obtain an unstretched film. Next, this unstretched film was stretched 4.2 times in the longitudinal direction at 115 ° 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 3.8 times in the width direction at 115 ° C., subjected to a tension heat treatment at a fixed length at 220 ° C., and re-heat treated while being stretched 2% in the width direction at 210 ° C., to have a thickness of 4.5 μm. A biaxially oriented polyester film was obtained. Table 2 shows the physical properties of the film and the evaluation results.

Example 4 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 2% in the width direction, to a thickness of 4.5 μm. A biaxially 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 a 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.
And heat-treated again at 215 ° C while shrinking 6% in the width direction
To a biaxially oriented polyester film having a thickness of 4.5 μm.
I got a film. 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 application of the easily adhesive layer was not performed. Table 2 shows the physical properties of the film and the evaluation results.

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[Table 1]

The compositions of the resins in Table 1 are as follows.

Acrylic resin: methyl methacrylate 75
An acrylic copolymer obtained by polymerizing mol% / ethyl acrylate 15 mol% / N-methylolacrylamide 5 mol% / 5 methacrylic acid 5 mol%.

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
Polyester copolymer.

Acrylic-modified polyester resin: 70% by mole of methyl methacrylate / 20% by mole of isobutyl methacrylate / 5% by mole of acrylic acid / 5% by mole of glycidyl methacrylate; polyester component: 40% by mole of terephthalic acid / isophthalic acid 4 as an acid component An acrylic-modified polyester copolymer of mol% / 5-sodium sulfoisophthalic acid 6 mol% / ethylene glycol 45 mol% / diethylene glycol 5 mol% as a glycol component.

Crosslinking agent: 1,3-bis (N, N-diglycidylamine) cyclohexane Wetting agent: polyoxyethylene (n = 7) lauryl ether

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[Table 2]

The evaluation results of the adhesiveness and the sharpness are the same for the fusion type and sublimation type thermal transfer inks.

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When the laminated film of the present invention is used as a base film of a thermal transfer recording medium, the adhesiveness between the ink layer for the thermal transfer type printing of the fusion type and the sublimation type is good, and Is excellent in dimensional stability, so that an excellent image can be obtained.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Kitazawa 3-37-19 Koyama, Sagamihara-shi, Kanagawa F-term in Sagamihara Research Center, Teijin Limited (Reference) 2H111 BA07 BA17 BB06 BB08 4F100 AK01B AK25B AK36H AK41A AK41B AK51H AK53H AL05B AR00B AR00C BA02 BA03 BA07 BA10A BA10C CA02B DD07B EH46 EJ37 EJ38A EJ86 GB90 JA11A JA20A JB09B JB16B JD14C JL04 JL11 JL12B JM01B

Claims (16)

[Claims] 1. A biaxially oriented polyester film having a degree of planar orientation in the range of 0.178 to 0.300, and an easily adhesive layer formed on at least one surface of the biaxially oriented polyester film for thermal transfer. Laminated film. 2. The laminated film according to claim 1, wherein the degree of plane orientation of the biaxially oriented polyester film is in the range of 0.180 to 0.300. 3. The laminated film according to claim 1, wherein the polyester of the biaxially oriented polyester film has a crystallinity of 30% or more. 4. The easily adhesive layer contains a thermoplastic resin, and the thermoplastic resin is an acrylic resin, a polyester resin,
Acrylic-modified polyester resin, polyurethane resin, polysiloxane resin, epoxy resin, polyether resin,
At least one selected from the group consisting of vinyl resins, modified cellulose resins, gelatins and polyolefin resins
The laminated film according to claim 1, which is a seed. 5. The laminated film according to claim 4, wherein the thermoplastic resin is water-soluble or water-dispersible. 6. The laminated film according to claim 4, wherein the thermoplastic resin contains an acrylic resin and a polyester resin. 7. The laminated film according to claim 6, wherein the acrylic resin is 10 to 90% by weight and the polyester resin is 90 to 10% by weight based on the total weight of the acrylic resin and the polyester resin. 8. The laminated film according to claim 1, wherein the easily adhesive layer is a reaction product of a thermoplastic resin and a crosslinking agent. 9. The laminated film according to claim 8, wherein the crosslinking agent is at least one selected from the group consisting of isocyanate, epoxy, oxazoline and melamine. 10. The easy-adhesive layer is formed by applying a coating liquid for forming an easy-adhesive layer to at least one surface of a stretchable polyester film, drying, stretching, and heat-treating. 3. The laminated film according to 1. 11. The coating liquid for forming an easily adhesive layer is an aqueous coating liquid containing a water-soluble or water-dispersible thermoplastic resin.
The laminated film according to 0. 12. The thickness of the easily adhesive layer is 0.001 to 1 μm.
The laminated film according to claim 1, which is in a range of m. 13. The laminated film according to claim 1, wherein the center line average surface roughness of the easily adhesive layer is in the range of 0.01 to 0.3 μm. 14. The laminated film according to claim 1, wherein the degree of plane orientation is in the range of 0.178 to 0.300. 15. Use of the laminated film according to claim 1 as a base film of a thermal transfer recording medium. 16. The use according to claim 15, for providing an ink layer on the easily adhesive layer of the laminated film.