JP2000108200A - Biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent productivity in the case of using as a ribbon for a thermal transfer printer and to improve a printing performance by preventing occurrence of a wrinkle of the ribbon caused by rubbing with a head without thinning of an ink even by printing at a high speed. SOLUTION: The biaxially oriented polyester film has a centerline mean roughness of 10 to 4 nm, and an AC volume resistivity of the molten biaxially oriented polyester film of 6×108 Ω.cm or less. A difference (thickness difference) between heights of adjacent ridge and trough in a continuous thickness chart of the film is 8% or less of the mean thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biaxially oriented polyester film. More specifically, when used as a ribbon for a thermal transfer printer, a biaxially oriented polyester with excellent productivity, excellent printing performance, with no loss of ink even when printing at high speed, and no wrinkling of the ribbon due to rubbing with the head. About the film.

[0002]

2. Description of the Related Art As a base film of a ribbon for a thermal transfer printer, a film having a specified surface roughness (Japanese Patent Laid-Open No. Sho 62-62).
No. 299389) is known.

[0003] Among the thermal transfer recording systems, the sublimation transfer recording system has been greatly expanded as a recording system capable of easily outputting a high-quality full-color image. The sublimation type thermal transfer system is a system in which a heat sublimable dye is contained in a binder, and only the dye sublimates by heat and is absorbed by an image receiving layer of a transfer receiving paper to form a gradation image. In recent years, as the printing speed has been required to be increased, the temperature of the thermal head at the time of printing has increased, and as a result, the amount of heat received by the thermal transfer printer ribbon has increased. For this reason, the deformation of the film used for the base material of the ribbon becomes large, and the printing becomes unclear at the time of printing, or wrinkles are generated on the ribbon, and in an extreme case, printing becomes impossible at all. A trouble occurred and this improvement was necessary.

Further, in the sublimation type thermal transfer system, a heat sublimable dye is contained in a binder, and only the dye sublimates by heat and is absorbed by an image receiving layer of a transfer receiving paper to form a gradation image. In order to sublimate only the dye, high adhesion between the binder and the base film is required, and further, it is essential that the adhesion does not decrease due to environmental changes or aging.
If the adhesion is insufficient, the binder layer migrates to the transfer receiving paper, significantly impairing the gradation, and a phenomenon called overtransfer occurs. Generally, a polyester film is highly crystallographically oriented, and therefore has poor adhesion and does not adhere at all even when an ink layer is directly applied. For this reason, the film surface is physically and chemically treated in order to increase the adhesiveness with the ink layer, but sufficient adhesiveness cannot be obtained.

In order to provide a film at low cost,
It is desirable to reduce breakage during film formation and stably form a film to increase film productivity. Polyethylene terephthalate (hereinafter sometimes abbreviated as PET) or polyethylene-
A polyester film containing 2,6-naphthalate (hereinafter may be abbreviated as PEN) is usually formed by quenching a film-like melt extruded from an extrusion die on the surface of a rotary cooling drum, and then biaxially and vertically. It is manufactured by stretching.
In this case, in order to eliminate the surface defects of the film and increase the uniformity of the thickness, it is necessary to increase the adhesion between the film-like melt and the surface of the rotary cooling drum. As a method of increasing this adhesion, a wire-shaped electrode is provided on the surface of the extrusion die and the rotary cooling drum to precipitate an electrostatic charge on the surface of the film-like molten material, and the surface of the film-like molten material is cooled and adhered to the surface of the rotary cooling drum. There is known a method of quenching while cooling (hereinafter referred to as an electrostatic casting method). However, the melt electric resistance of polyester is large, and the undrawn film for forming a thin film such as a transfer ribbon film is thin, so the unit area electrostatic charge on the surface of the film-like material is small,
The adhesion between the film and the drum surface decreases, causing pin-like defects on the film surface, reducing the uniformity of the film thickness, and causing breakage when forming thin films such as transfer ribbon films. Becomes

[0006]

SUMMARY OF THE INVENTION The present invention solves these problems. When used as a thermal transfer ribbon, the film deforms little when heated, has excellent adhesion to the thermal transfer ink layer, and has excellent gradation. It is an object of the present invention to provide a biaxially oriented polyester film capable of obtaining a transferred image having excellent property and having excellent productivity with less breakage and excellent flatness.

[0007]

The present invention is directed to a biaxially oriented polyester film having a center line average roughness of 10 to 40 nm, wherein the molten biaxially oriented polyester film has an AC volume resistivity of 6 × 10 ^8. A biaxially oriented polyester film having a Ω · cm or less, and a difference in height (thickness difference) between adjacent peaks and valleys in the continuous thickness chart of the film is within 8% of an average thickness. .

[Polyester] The biaxially oriented polyester film of the present invention is made of polyester, especially PET or PEN.
And a quaternary phosphonium sulfonic acid salt having an ester-forming functional group in an amount of 0.1 to 40 mmol% based on the bifunctional carboxylic acid component. As the sulfonic acid quaternary phosphonium salt having an ester-forming functional group, for example, a compound represented by the following formula (1) is preferably used.

[0009]

Embedded image

In the above formula, n is an integer of 1 or 2,
A is n + 2, for example, trivalent (when n = 1) or 4
Valent or (when n = 2) an aliphatic or aromatic group having 2 to 18 carbon atoms. As the aliphatic group, for example, a linear or branched, saturated or unsaturated hydrocarbon group having 2 to 10 carbon atoms is more preferable. As the aromatic group,
An aromatic group having 6 to 18 carbon atoms is preferable, and for example, a trivalent or tetravalent benzene skeleton, a naphthalene skeleton or a biphenyl skeleton can be mentioned as a more preferable one.
Such an aromatic group may be substituted with, for example, an alkyl group having 1 to 12 carbon atoms in addition to X ¹ , X ² and a quaternary phosphonium sulfonic acid base.

X ¹ and X ² can be the same or different and are hydrogen or an ester-forming functional group. If X ¹ and X ² are simultaneously hydrogen, it will lack a group to be copolymerized in the polyester chain. X ¹ and X ² are not simultaneously hydrogen atoms and at least one must be an ester-forming functional group.

The ester-forming functional groups include, for example,
^{-OOCR 5, -COOH, -COOR 6,} -C m H 2m O
_{H, - (OC p H 2p} ) q OH, -CH 2 - (OC r H 2r) s
OH and the like can be mentioned. In these groups, R ⁵ and R ⁶ are each a lower alkyl group having 1 to 4 carbon atoms or a phenyl group, m is an integer of 2 to 10, p and r are each an integer of 2 to 4, Then, q and s are each an integer of 1 or more, for example, an integer of 1 to 100.

The lower alkyl group for R ⁵ and R ⁶ may be linear or branched, for example, methyl,
Preferred examples include ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl and the like.

The groups R ¹ , R ² , R ³ and R ⁴ constituting the phosphonium sulfonate group are the same or different from each other and are an alkyl group having 1 to 18 carbon atoms, a benzyl group or a group having 6 to 12 carbon atoms. Is an aryl group. Carbon number 1
The alkyl group 18 may be linear or branched. For example, methyl, ethyl, propyl, butyl, dodecyl, stearyl and the like can be mentioned.
Preferred examples of the aryl group having 6 to 12 carbon atoms include phenyl, naphthyl, biphenyl and the like. The phenyl moiety of these aryl groups or benzyl groups may be substituted with, for example, a halogen atom, a nitro group or a lower alkyl group having 1 to 4 carbon atoms.

Preferred examples of the quaternary phosphonium sulfonic acid salt include tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate, ethyltributylphosphonium 3,5-dicarboxybenzenesulfonate and 3,5-dicarboxybenzenesulfonate. Benzyltributylphosphonium carboxybenzenesulfonate, phenyltributylphosphonium 3,5-dicarboxybenzenesulfonate,
3,5-dicarboxybenzenesulfonic acid tetraphenylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid ethyltriphenylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid butyltriphenylphosphonium salt, 3,5-dicarboxy Benzenesulfonic acid benzyltriphenylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid tetrabutylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid ethyltributylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid benzyl Tributylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid phenyltributylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid tetraphenylphosphonium salt, 3,5-dica Ethyl triphenyl phosphonium salt of bomethoxybenzene sulfonic acid, butyl triphenyl phosphonium salt of 3,5-dicarbomethoxy benzene sulfonic acid, benzyl triphenyl phosphonium salt of 3,5-dicarbomethoxy benzene sulfonic acid, tetra carboxybenzene sulfonic acid Butylphosphonium salt, 3-carboxybenzenesulfonic acid tetraphenylphosphonium salt, 3-carbomethoxybenzenesulfonic acid tetrabutylphosphonium salt, 3-carbomethoxybenzenesulfonic acid tetraphenylphosphonium salt, 3,5-di (β
-Hydroxyethoxycarbonyl) benzenesulfonic acid tetrabutylphosphonium salt, 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonic acid tetraphenylphosphonium salt, 3- (β-hydroxyethoxycarbonyl) benzenesulfonic acid tetrabutylphosphonium salt, 3- (β-hydroxyethoxycarbonyl) benzenesulfonic acid tetraphenylphosphonium salt, 4-
Hydroxyethoxybenzenesulfonic acid tetrabutylphosphonium salt, bisphenol A-3,3'-di (sulfonic acid tetrabutylphosphonium salt), 2,6-dicarboxynaphthalene-4-sulfonic acid tetrabutylphosphonium salt, α-tetrabutylphosphonium Sulfosuccinic acid and the like can be mentioned. The above quaternary phosphonium salts of sulfonic acid may be used alone or in combination of two or more.

Such quaternary phosphonium salts of sulfonic acid are generally prepared by a reaction known per se between the corresponding sulfonic acid and phosphines or a reaction known per se between the corresponding metal salt of sulfonic acid and quaternary phosphonium halides. Can be easily manufactured.

The polyester film of the present invention is prepared by adding the above quaternary phosphonium sulfonic acid salt to the bifunctional carboxylic acid component constituting the polyester in an amount of 0.1 to 40.
mmol%, preferably 0.1-20 mmol%, more preferably 0.2-10 mmol%.
That is, the technical concept of the polyester targeted in the present invention is different from the modified polyester containing, for example, a quaternary phosphonium salt of sulfonic acid in an amount sufficient to be used as a dyeing seat for a cationic dye. The decrease in the physical properties of the polyester due to the inclusion of the phosphonium salt, for example, the decrease in the softening point, is substantially negligible, and shows physical properties almost equivalent to those of the polyester not containing the quaternary phosphonium sulfonic acid salt.

In the present invention, any known method can be used as a method for incorporating a quaternary phosphonium sulfonic acid salt into a polyester film. For example, a method in which the compound is added during the polymerization of a polyester polymer and copolymerized. Examples include a method of adding the compound to the polyester polymer before forming the film, a method of preparing a polymer composition (master chip) containing the compound at a high concentration, and mixing a predetermined amount of the polymer before melting the polyester polymer. In any case, if the quaternary phosphonium sulfonic acid salt is finally contained in the polyester film in a predetermined amount, the effect is exhibited.

As the components other than the above components and the components constituting the repeating units of the polyester, copolymers in which at least 80 mol% of all the components are the components constituting the repeating units of the polyester are preferably used. With such a composition, a film having a small dimensional change at high temperature can be obtained without extremely losing the inherent properties of the polyester.

Suitable copolymerizable components include compounds having two ester-forming functional groups, such as oxalic acid, adipic acid, phthalic acid, sebacic acid, dodecanedicarboxylic acid,
Succinic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, terephthalic acid, 2-potassium sulfoterephthalic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, phenylindane Dicarboxylic acids, diphenyl ether dicarboxylic acids and their lower alkyl esters;
Oxycarboxylic acids such as p-oxyethoxybenzoic acid and lower alkyl esters thereof; propylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, , 6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, p-xylylene glycol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol S , Triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol, neopentyl glycol and the like.

The polyester may be one in which a terminal hydroxyl group and / or a carboxyl group is partially or entirely blocked with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. May be modified with a trifunctional or higher functional ester-forming compound such as glycerin or pentaerythritol as long as a substantially linear polymer can be obtained.

[Additives] The biaxially oriented polyester film of the present invention may optionally contain additives such as stabilizers, dyes, lubricants, ultraviolet absorbers, and flame retardants.

In order to provide the film with a preferable lubricating property, it is preferable to contain a small amount of inert particles.
Such inert particles include, for example, spherical silica, porous silica, calcium carbonate, silica alumina, alumina,
Examples include inorganic particles such as titanium dioxide, kaolin clay, barium sulfate, and zeolite, or organic particles such as silicon resin particles and cross-linked polystyrene particles. The inorganic particles are preferably synthetic products rather than natural products for reasons such as uniform particle size, and inorganic particles of any crystal form, hardness, specific gravity, and color can be used.

The above-mentioned inert fine particles have an average particle size of 0.05.
Μ3.0 μm, preferably 0.1-3.0 μm.
More preferably, it is 1.8 μm. Further, the content of the inert fine particles is preferably from 0.001 to 1.0% by weight, and more preferably from 0.03 to 0.5% by weight. The inert particles to be added to the film may be a single component selected from those exemplified above, or a multi-component containing two or more components. The timing of adding the inert particles is not particularly limited as long as it is a stage until a polyester film is formed, and may be added at a polymerization stage, for example.
Also, it may be added at the time of film formation.

By adding a lubricant as described above, a biaxially oriented polyester film having an average surface roughness of 10 to 40 nm can be obtained. If the average surface roughness of the film is less than 10 nm, sufficient slip properties cannot be obtained, and it becomes difficult to wind the film. Moreover, the average surface roughness is 40 nm.
If it is larger than that, when high-speed printing is performed by a thermal transfer printer, heat conduction deteriorates and the printing becomes unclear. If the particle size of the inorganic or organic lubricant to be added is smaller than 0.05 μm, sufficient surface roughness cannot be obtained, so that the winding property is reduced and the productivity is reduced. When it is larger than 3.0 μm, the film is likely to be broken in the stretching step.

[Volume resistivity] The AC volume resistivity in the molten state of the film of the present invention shows a closer relationship with the amount of charge that can be applied to the surface of the melt of the polyester film than the DC volume resistivity. An aromatic polyester having a film having a value of AC volume resistivity of 6.0 × 10 ⁸ Ω · cm or less can provide a sufficient amount of electric charge to adhere to a relatively rapidly rotating cooling drum.

In the biaxially oriented polyester film of the present invention, the value of the AC volume resistivity of the molten film is preferably in the range of 0.07 × 10 ^{8 to} 6.0 × 10 ⁸ Ω · cm.

The method for producing the biaxially oriented polyester film of the present invention is as follows.
This is done by extruding to a thickness of 0 μm, then uniformly adhering the film on the cooling drum and cooling the film on the cooling drum. The molten film extruded on the rotating cooling drum is brought into contact (for example, 3 mm) from the film surface in the vicinity (immediately before) reaching the drum.
Charges are forcibly applied from electrodes provided in a space separated by 10 to 10 mm. The polyester targeted in the present invention,
As described above, the quaternary phosphonium salt of sulfonic acid is used in an amount of 0.1 to
Shows the AC volume resistivity of a molten film containing 40 mmol% and 6.0 × 10 ⁸ Ω · cm or less, and even with a thin film-like material given such charge, it uniformly adheres to the rotating cooling drum.

[Endothermic Sub-Peak Temperature] The biaxially oriented polyester film of the present invention is obtained by using a DSC (differential thermal scanning calorimeter).
It is preferable that the endothermic sub-peak temperature due to heat fixation during film formation other than the melting point measured at 225 ° C. or more exists. This temperature is preferably 230 ° C. or higher, particularly 235 ° C. or higher, and most preferably 240 ° C. or higher. However,
When the endothermic sub-peak temperature is around 240 ° C, the peak due to heat fixation during film formation may overlap with the peak of the melting point and may become a shoulder peak. In this case, it is observed when the background of the melting point peak is subtracted. The peak obtained is referred to as an endothermic sub-peak.

The biaxially oriented polyester film can stably withstand heat up to the processing temperature due to the heat setting treatment in the manufacturing process, and the dimensional stability is improved. When heat above the processing temperature is applied to the film, the thermal dimensional stability deteriorates. Although the upper limit of the endothermic subpeak is not particularly defined,
248 ° C. or lower is preferred. If the temperature is higher than this, the flatness is reduced. Furthermore, the amount of relaxation of highly oriented molecular chains is increased by stretching, and the strength is reduced. When used as a thermal transfer ribbon, it may not be able to withstand the tension of the printer and may be broken.

[Space Factor] The biaxially oriented polyester film of the present invention has a space factor of 1
It is preferably about 23%. If this value is less than 1%, the slipperiness and workability (handling properties) of the film are somewhat insufficient, while if it exceeds 23%, the surface becomes too rough, which may cause breakage.

[Refractive Index] The biaxially oriented polyester film of the present invention preferably has a refractive index (nMD) in the longitudinal direction of 1.77 or more. 1.77 longitudinal refractive index
If it is smaller, the thermal transfer ribbon cannot withstand the tension of the printer when the film is heated during printing, causing wrinkles or breaking in some cases, causing undesired jamming.

[Thickness] The thickness of the biaxially oriented polyester film of the present invention is preferably 0.5 to 10 μm. Thickness 1
If it exceeds 0 μm, heat conduction takes time, which is not suitable for high-speed printing. Conversely, if the thickness is less than 0.5 μm, the strength is low and the workability is poor. Further, the strength required as a ribbon is inferior and is not preferred.

[Thickness unevenness] In the biaxially oriented polyester film of the present invention, when a continuous thickness chart is obtained by continuously measuring the thickness, the difference in height (thickness) between adjacent peaks and valleys in the continuous thickness chart is obtained. Difference) is within 8%, preferably within 5%, more preferably within 3% of the average thickness in both the longitudinal and width directions. In addition, the interval between the peak and the valley is 10 cm.
It is preferable that there is the above.

Further, the thickness unevenness in the entire width direction is within 13%,
It is preferably within 10%, and the thickness unevenness per 5 m length in the longitudinal direction is within 15%, preferably 12%.
It is desirable to be within. A film that satisfies these conditions is a film having a very uniform thickness, and achieves an excellent effect that no coating unevenness occurs when the easy-adhesion layer is applied, and that no coating unevenness occurs when a dye is applied. it can.

In the continuous thickness chart, the difference between the heights of adjacent peaks and valleys (thickness difference), the distance between the peaks and valleys, and the thickness unevenness are values obtained by measurement by the following methods.

Using an electronic micrometer, the thickness was continuously measured over the length of 5 m and 1 m in the longitudinal direction and the width direction of the film, and a continuous thickness chart (thickness against position) was obtained. And the minimum thickness as well as the difference in thickness and spacing between adjacent peaks and valleys, and the average calculated from the film width (cm), length (cm), weight (g) and density (g / cm ³ ) It is calculated from the thickness and the following formula. The thickness unevenness is calculated and calculated for each of the longitudinal direction and the width direction of the film. Average thickness (μm) = [weight / (width × length × density)] × 1
0000 Uneven thickness (%) = [(maximum thickness−minimum thickness) / average thickness]
× 100 Difference in thickness between adjacent peaks and valleys = [(thickness of peaks-thickness of valleys) /
Average thickness] x 100

[Easy Adhesive Layer] On the surface of the biaxially oriented polyester film of the present invention on which the ink layer is to be applied, at least one water-soluble polyester selected from the group consisting of urethane, polyester, acrylic and vinyl resin-modified polyester. Alternatively, it is necessary to have a coating layer made of a water-dispersible resin. This coating layer is necessary to enhance the adhesion between the ink layer composed of the sublimable dye and the resin binder and the film. Examples of the water-soluble or water-dispersible resin that can be used as the coating layer of the film of the present invention include the following urethane, polyester, acryl, and vinyl resin-modified polyesters.

The urethane-based resin used for the coating layer is a polyvalent hydroxy compound as a component constituting the urethane-based resin as follows:
Examples thereof include a polyvalent isocyanate compound, a chain extender, and a crosslinking agent. 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.
Examples of the polyvalent isocyanate compound include tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and 4,4 ′
-Dicyclohexylmethane diisocyanate, isophorone diisocyanate and the like can be used. 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, and 4,4′- Diaminodicyclohexylmethane, water and the like. One or more of these compounds are appropriately selected, and a polyurethane resin is synthesized by a usual polycondensation-crosslinking reaction.

The polyester used in the coating layer can be exemplified by the following polyvalent carboxylic acids and polyvalent hydroxy compounds as constituents thereof. That is, as the polycarboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5
-Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid , Succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, monopotassium trimellitic acid, and ester-forming derivatives thereof, and the like. As the compound, ethylene glycol, 1,2-propylene glycol, 1,
3-propylene glycol, 1,4-butanediol,
1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol,
Bisphenol A-ethylene glycol adduct, bisphenol A-1,2-propylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin,
Trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate and the like can be used. From these compounds, one or more polyvalent carboxylic acids and one or more polyvalent hydroxy compounds are selected, and a polyester is synthesized by a conventional polycondensation reaction. In addition to the above, a composite polymer having a polyester component such as a polyester polyurethane obtained by chain-extending a polyester polyol with an isocyanate is also included in the polyester-based resin referred to in the present invention.

The acrylic resin used in the coating layer is preferably one containing alkyl acrylate or alkyl methacrylate as a main component, and the component is 30 to 90 mol%, and is a copolymerizable vinyl monomer having a functional group. A water-soluble or water-dispersible resin containing 70 to 10 mol% of a component. 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,
Examples include ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, and cyclohexyl group.

As the vinyl monomer having a functional group copolymerizable with an alkyl acrylate or an alkyl methacrylate, the following compounds having a functional group such as a reactive functional group, a self-crosslinkable functional group, and a hydrophilic group can be used. . Examples of the compound having a carboxyl group or a salt thereof, and an acid anhydride group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, metal salts of these carboxylic acids with sodium, ammonium salts, maleic anhydride, and the like. . Examples of the compound having a sulfonic acid group or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid, metal salts of these sulfonic acids with sodium and the like, and ammonium salts. Examples of the compound having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylolated acrylamide, methylolated methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, ureido ethyl acrylate, and the like. No. Examples of the compound having an amino group or an alkylolated amino group or a salt thereof include diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether, dimethylaminoethyl methacrylate, and dimethylaminoethyl. Vinyl ethers, those whose amino groups are methylolated,
Examples thereof include those quaternized with an alkyl halide, dimethyl sulfate, sultone, or the like. As the compound having a hydroxyl group, β-hydroxyethyl acrylate, β
-Hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxyethyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, Examples of the compound having an epoxy group, such as polypropylene glycol monomethacrylate, include glycidyl acrylate and glycidyl methacrylate. Other compounds having a functional group include vinyl isocyanate and allyl isocyanate.
Further, olefins such as ethylene, propylene, methylpentene, butadiene, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, acrylonitrile,
Methacrylonitrile, vinylidene chloride, vinyl chloride, vinylidene fluoride, ethylene tetrafluoride, vinyl acetate, and the like are also examples of the vinyl monomer compound.

The water-soluble or water-dispersible resin of the vinyl resin-modified polyester resin used for the coating layer can be synthesized by copolymerizing the vinyl resin in the water-soluble or water-dispersible resin of the polyester. Examples of the components constituting the polyester include the following polybasic acids or their ester-forming derivatives and polyols or their ester-forming derivatives. That is, as the polybasic acid component, terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid,
Trimellitic acid, pyromellitic acid, dimer acid and the like. A copolymerized polyester resin is synthesized using two or more of these acid components. In addition, a small amount of an unsaturated polybasic acid component such as maleic acid, itaconic acid, and hydroxycarboxylic acid such as p-hydroxybenzoic acid can be used. Examples of the polyol component include ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, and poly (ethylene oxide) glycol. And poly (tetramethylene oxide) glycol. Two or more of these can be used. Further, vinyl-based monomers such as those exemplified below are exemplified. Examples of the vinyl monomer include alkyl acrylates and alkyl methacrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, Cyclohexyl group, etc.); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-
Hydroxy-containing monomers such as hydroxypropyl acrylate and 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N, N-dialkylacrylamide, N, N-dialkylmethacrylate (as the alkyl group, Methyl group, ethyl group, n-
Propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, cyclohexyl, etc.), N-alkoxyacrylamide, N-alkoxymethacrylamide, N, N-dialkoxyacrylamide, N, Amides such as N-dialkoxy methacrylamide (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), N-methylolacrylamide, N-methylolmethacrylamide, N-phenylacrylamide, N-phenylmethacrylamide, etc. Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid Monomers containing a galboxyl group or a salt thereof, such as a salt thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); monomers of an acid anhydride, such as maleic anhydride or itaconic anhydride; vinyl isocyanate, allyl Isocyanate, styrene,
α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxy silane, alkyl maleate monoester, alkyl fumarate monoester, alkyl itaconate monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, chloride Examples include monomers such as vinyl, vinyl acetate, and butadiene. In addition, these monomers are exemplified, but not limited thereto. These monomers can be copolymerized using one kind or two or more kinds.

The coating solution for forming the easily adhesive layer of the present invention may contain a small amount of organic solvent as long as it does not affect the water-soluble or water-dispersible resin of the above resin or other additives.
This 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 capable of lowering the surface tension of the aqueous coating solution to 40 dyne / cm or less and promoting wetting on a polyester film are preferable. For example, polyoxyethylene alkylphenyl ether, polyoxyethylene-fatty acid ester, 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-type surfactants and the like can be mentioned.

In the coating layer of the biaxially oriented polyester film of the present invention, an isocyanate-based compound, an epoxy-based compound, or a crosslinking agent is used as a cross-linking agent in order to improve adhesion (blocking properties), water resistance, solvent resistance, and mechanical strength. An oxazoline-based compound, an aziridine compound, a melamine-based compound, a silane coupling agent, a titanium coupling agent, a zirco-aluminate-based coupling agent, and the like may be contained. Also,
If the resin component has a crosslinking reaction point, a reaction initiator such as a peroxide or an amine, or a sensitizer may be contained in a photosensitive resin or the like. In addition, for the purpose of improving the adhesion and sliding properties, silica, silica sol, alumina, as inorganic fine particles in the coating layer,
Alumina sol, zirconium sol, kaolin, talc,
Calcium carbonate, calcium phosphate, titanium oxide, barium sulfate, carbon black, molybdenum sulfide, antimony oxide sol, etc., as organic fine particles, polystyrene, polyethylene, polyamide, polyester, polyacrylate, epoxy resin, silicone resin, fluorine resin, etc. May be contained. If necessary,
It may contain an antifoaming agent, a coating improver, a thickener, an antistatic agent, an organic lubricant, an antioxidant, a foaming agent, a dye, a pigment, and the like.

This coating solution is preferably applied to one or both sides of the biaxially oriented polyester film before the completion of the crystal orientation in the process of producing the biaxially oriented polyester film. It may be coated separately from the film manufacturing process,
In this case, dust and dirt are easily entangled, and that portion becomes a defect during printing, so a clean atmosphere is desirable.
Further, a suitable film can be produced at relatively low cost, and from these points, coating during the production 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 10% by weight. The coating amount is preferably 0.5 to 50 g per 1 m ^{2 of the} running film.

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.

[Production Method of Film] The biaxially oriented polyester film of the present invention can be produced by biaxially stretching an unstretched film obtained by a usual method and heat-setting, and after heat setting, a relaxation treatment is carried out. By doing so, it can be produced more advantageously. For example, the unstretched film is biaxially stretched at a temperature of Tg to (Tg + 60) ° C in the longitudinal and transverse directions at a magnification of 2.0 to 6.0 times, and is 225 ° C or more, preferably 1 to 235 to 250 ° C. Heat set for 100 seconds. In the heat setting, it is desirable that the zone is divided into two or more, preferably four or more, since the temperature can be controlled for each zone. By setting the temperature of the heat setting zone to the highest temperature of 225 ° C. or higher, preferably 235 ° C. or higher, the structure formed by heat setting is stabilized. Stretching can be performed by a commonly used method, for example, a method using an IR heater, a method using a roll, or a method using a tenter, and may be simultaneously stretched in the vertical and horizontal directions, or may be sequentially performed in the vertical and horizontal directions. You may.

In the case of further performing a relaxation treatment, the relaxation treatment is performed until the film is wound around a roll after the heat setting. The relaxation treatment is performed by reducing the tenter width in the middle of the heat fixing zone and reducing the width of the tenter from 0 to 3 in the film width direction. %, A method in which both ends of the film are cut off, and a method in which the take-off speed is reduced with respect to the supply speed of the film under a temperature condition not lower than the melting point of the film and not higher than the melting temperature. A method of heating with an IR heater, a method of transporting a film on a heating transport roll and reducing the speed of the transport roll after the heating transport roll, and a method of transporting the film over a nozzle that blows out hot air after heat fixing, while controlling the supply speed. After the film is wound on a film-forming machine, the film is transported on a heated transport roll, There is a method of reducing the temperature, or a method of reducing the roll speed after the heating zone from the roll speed before the heating zone while transporting the heating zone in the heating oven or the IR heater, and any method may be used. The relaxation process is performed by setting the deceleration rate of the take-up side speed to 0.1 to 3% of the take-up side speed. Further, in order to keep the heat shrinkage ratio within the range of the present invention, in addition to the relaxation treatment, the width of the tenter may be increased in the middle of the heat setting zone, and a tension treatment of 0 to 3% may be performed in the film width direction. Such a treatment is not limited to these methods as long as the heat yield falls within the scope of the present invention. Further, it is preferable that the processing is performed in the final heat setting zone where the temperature is the highest, in order to form a dimensionally stable structure.

The biaxially oriented polyester film of the present invention is useful as a thermal transfer ribbon. Hereinafter, the configuration of the thermal transfer ribbon will be described.

[Thermal Transfer Ink Layer] When an easily adhesive layer is provided on one surface of the biaxially oriented polyester film of the present invention, a thermal transfer ink layer is provided on the easily adhesive layer surface to prepare a thermal transfer ribbon.

The thermal transfer ink layer is not particularly limited, and a known one can be used. That is,
It is composed of a binder component, a coloring component, and the like as main components, and an appropriate amount of a softener, a plasticizer, a dispersant, and the like, as necessary. Specific examples of the main component include, as binder components, known waxes such as carnauba wax and paraffin wax, celluloses, polyvinyl alcohols, polyvinyl alcohol partially acetalized products, polyamides, and various high-melting polymer materials. As the coloring agent, carbon black is mainly used, and other various dyes or organic or inorganic pigments are used. Further, the thermal transfer ink layer may contain a sublimable dye. Various disperse dyes and basic dyes can be used as the sublimable dye.

As a method for providing the thermal transfer ink layer on the surface of the easy-adhesion layer of the base material layer, there are known methods, for example, hot melt coating, a solution coating method such as gravure, reverse or slit die method with a solvent added, and the like. Can be used.

[Fusion-preventing layer] In order to prevent sticking of the thermal head portion, on the side where the thermal transfer ink layer is not provided, it is preferably formed of a polyol, for example, a polyalcohol, a polyisocyanate compound and a phosphate polyester compound. . Examples of such a polyalcohol include a polyvinyl butyral resin having a hydroxyl group, a polyester resin, a polyether resin, a polybutadiene resin,
Acrylic polyols, nitrocellulose resins, cellulose acetate resins, cellulose acetate resins, urethane and epoxy prepolymers can be preferably used. Further, the anti-fusing layer may be provided after unstretching or longitudinal stretching, or may be performed after the film is once wound as a biaxial film. By doing this,
After processing into the transfer ribbon, the thermal history applied to the base from the thermal head can be reduced, which is preferable.

[0055]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples. The method for measuring and evaluating the characteristic values will be described below.

(1) Film-forming property When a voltage of 7000 V is applied between the polymer and the cooling drum by an electrode placed near the die for extruding the polymer into a film and above the extruded film, casting is performed. , No pinner bubble,
A stable film can be formed without reducing the uniformity of the thickness. At this time, the film forming property of the film was observed and evaluated according to the following criteria. Rank A: Breakage does not occur, and a film can be formed extremely stably. Rank B: Breakage hardly occurs, and stable film formation is possible. Rank C: Breakage sometimes occurs, and film formation is unstable. Rank D: Breakage occurs frequently, and substantially stable film formation is impossible.

(2) AC Volume Resistivity The AC volume resistivity was measured using the apparatus shown in FIG. The films are stacked so that the measurement sample has a thickness of about 150 μm. On the upper surface of the cylindrical lower electrode 2 having a diameter of 20 cm, a diameter of 5.6 cm and a thickness of 0.2 cm capable of holding a parallel gap of 150 μm.
The upper electrode 3 is disposed, and a measurement sample is inserted so as to be in close contact with the electrode.

The lower electrode has a built-in power supply device 4 and a temperature detecting end 5. The variation in the surface temperature of the lower electrode on the surface to be measured is within 1 ° C., and the temperature difference between the lower end and the detecting end is 8 ° C./min. Construct so as to be within 2 ° C. The detected temperature is measured by the reading thermometer 7. The whole of the electrode is placed in the heat insulation box 11.

The power supply 8 applies the generated voltage between the two electrodes via the standard resistor 9. The power supply is a power supply for generating a DC of 100 V when measuring the DC volume resistivity of the film. Is a power source that generates 100 V and 50 Hz when the AC volume resistivity is measured. As for the current flowing through this circuit, the voltage generated across the standard resistor 9 is read by an electron meter 10 having an internal impedance of 100 MΩ or more.

In the present invention, the measurement of the AC volume resistivity of the film at the time of melting is carried out by measuring the temperature of the lower electrode at a rate of 8 ° C./min. (290 ° C. for polyethylene-2,6-naphthalate), and the AC volume resistivity Z
Is obtained from the following equation from the applied voltage E, the current I, the electrode area S, and the electrode interval d. Z = (E / I) × (S / d)

(3) Refractive index (nMD) Measured using an Abbe refractometer with a NaD line (589 nm) as a light source. nMD represents the refractive index in the longitudinal direction of the film.

(4) Density This is a value measured by a floating sedimentation method at 25 ° C. in a density gradient tube using an aqueous solution of calcium nitrate.

(5) Film thickness and thickness unevenness An electronic micrometer (K-312A) manufactured by Anritsu Corporation
The film thickness was measured over a length of 5 m and 1 m in the vertical and horizontal directions of the film at a stylus pressure of 30 g and a running speed of 25 mm / sec, respectively, to obtain a continuous thickness chart. From this chart, the maximum thickness and the minimum thickness, and the difference between the thicknesses of adjacent peaks and valleys were read. Next, for the same sample, the width (c
m), length (cm), weight (g), density (g / cm ³ )
Was measured, and the average thickness (μm) was calculated by the following equation. Then, the ratio of the difference between the above maximum thickness and the minimum thickness to the average thickness was calculated by the following equation to obtain a thickness unevenness, and the ratio of the difference between the thickness of the adjacent peak and valley to the average thickness was calculated by the following equation. Average thickness (μm) = [weight / (width × length × density)] × 1
0000 Uneven thickness (%) = [(maximum thickness−minimum thickness) / average thickness]
× 100 Ratio of thickness difference between adjacent peaks and valleys to average thickness =
[(Mountain thickness-valley thickness) / average thickness] × 100

(6) Center Line Average Roughness (Ra) Both the front and back surfaces of the film were measured with a surface roughness meter (Surfcom 111A, Tokyo Seimitsu Co., Ltd.), and the average value was calculated to determine the surface roughness.

(7) Space Factor (SF) Film weight w (g) and density d (g) of 100 cm ² sample
/ Cm ³ ) and the thickness by gravimetric method, t ¹ (μm), 10c
Ten sample films of m-square are stacked, and the thickness of one sample film determined using a micrometer is t ² (μm).
Was calculated from the following equation. SF (%) = 100−t ¹ / t ² × 100

(8) Endothermic sub-peak temperature (° C.) A thermal analysis system (differential thermal scanning calorimeter, DSC) SSC5200 manufactured by Seiko Denshi Kogyo Co., Ltd.
The film was heated in a nitrogen stream at a rate of 20 ° C./min.
Analysis is performed by the next derivative to determine a temperature at which a peak is exhibited, and this is defined as an endothermic sub-peak temperature. At this time, the endothermic sub-peak is not a peak of the melting point but a peak resulting from partial melting of the structure formed by heat setting.

(9) Adhesiveness A mending tape 810 manufactured by Sumitomo 3M Co., Ltd. was adhered to the ink layer surface of the produced thermal transfer ribbon to perform rapid peeling, and the adhesiveness was determined as follows depending on the degree of peeling of the ink layer. evaluate. 5: no ink layer peeling 4; ink layer peeling area less than 10% 3: ink layer peeling area 10% to less than 30% 2: ink layer peeling area 30% to less than 80% 1: ink layer peeling area Is 80% or more

(10) Printability A printer Hitachi VY · 200 was added to the image receiving sheet VY · 200 (standard paper product name, manufactured by Hitachi, Ltd.).
(Product name, manufactured by Hitachi, Ltd.) was printed so that the optical density became maximum. With respect to the produced thermal transfer ribbon, printability and wrinkles generated on the ribbon were evaluated according to the following criteria. ：: Clear printing Δ: Printing density is not uniform. X: The ribbon is wrinkled and the print is disturbed.

Examples 1-4 and Comparative Examples 1-2 0.024 parts of manganese acetate tetrahydrate was added to a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts of ethylene glycol.
The transesterification reaction was performed while gradually raising the temperature from 150 ° C to 240 ° C. During the reaction, when the reaction temperature reached 170 ° C., 0.019 parts of antimony trioxide was added, and further 0.3 parts by weight of spherical silica particles having an average particle diameter of 1.2 μm were added, and then, when the temperature reached 220 ° C. The quaternary phosphonium sulfonic acid salt shown in Table 1 was added to ethylene glycol in an amount corresponding to the content shown in Table 1, and this mixture was added as a solution heated to 40 ° C. (In Comparative Example 2, the quaternary phosphonium sulfonic acid salt was not added.)

Subsequently, a transesterification reaction was carried out, and after the transesterification reaction was completed, trimethyl phosphate was dissolved in ethylene glycol at 135 ° C. for 5 hours at 1.1 to 1.6 kg / c.
A solution heat-treated under a pressure of m ² (0.018 part in terms of trimethyl phosphate) was added. Thereafter, the reaction product was transferred to a polymerization reactor, and the temperature was raised to 290 ° C.
g under a high vacuum of 25 ° C.
-A copolymerized PET polymer having an intrinsic viscosity of 0.62 measured in chlorophenol was obtained.

The copolymerized PET polymer was melt-extruded into a sheet by an extruder and a T-die, and closely adhered to a water-cooled casting drum at a speed of 37.5 m / min to be cooled and solidified to obtain an unstretched sheet. The unstretched film is stretched by a high-speed roll 150 in the machine direction (machine direction) by roll stretching.
The film was stretched at 105 ° C. at a rate shown in Table 1 at m / min.

On the side of the longitudinally stretched film not coated with the ink layer, a coating having the following composition was applied as a fusion preventing layer by a gravure coater so that the coating thickness after drying was 0.5 μm. On the side to which the ink layer was applied, a coating agent having the following composition was applied as an easy-adhesion layer using a gravure coater so that the coating film thickness after drying was 0.1 μm. Then, it is biaxially stretched sequentially at 110 ° C. in the transverse direction (width direction) at the magnifications shown in Table 1 and heat-fixed in the first, second, and third heat-fixing zones at the temperatures shown in Table 1 for 2 seconds each. Relaxation (tension) treatment in the width direction was performed in the heat setting zone under the conditions shown in Table 1 to obtain a biaxially oriented film having the thickness shown in Table 1.

<Coating composition for anti-fusion layer> Acrylic ester 14.0% by weight Amino-modified silicone 5.9% by weight Isocyanate 0.1% by weight Water 80.0% by weight <Coating composition for easy adhesion layer> (Acrylic + Polyester + Epoxy)> Acrylic resin 42 solid weight% (Methyl methacrylate 65 mol% / ethyl acrylate 28 mol% / 2-hydroxyethyl methacrylate 2 mol% / N-methylol acrylamide 5 mol%) Polyester resin 42 solid % By weight (acid component: terephthalic acid 35 mol% / isophthalic acid 13)
Mole% / 5-sodium sulfoisophthalic acid 2 mole%,
Glycol component: ethylene glycol 45 mol% / diethylene glycol 5 mol%) Epoxy crosslinking agent 6 solid content% (N, N, N ', N'-tetraglycidyl-m-xylylenediamine) wetting agent 10 solid content weight% (Lauryl polyoxyethylene) For the obtained biaxially oriented film, the AC volume resistivity,
The refractive index, thickness (average thickness, height difference between peaks and valleys, interval, thickness unevenness), endothermic subpeak temperature, centerline average roughness, density and space factor in the longitudinal direction were measured and evaluated.

Next, a thermal transfer ink having the following composition was applied to the surface opposite to the anti-fusing layer by a gravure coater so that the coating thickness became 1.0 μm, thereby producing a thermal transfer ribbon. <Thermal transfer ink composition> Magenta dye (MSRedG) 3.5% by weight Polyvinyl acetoacetal resin 3.5% by weight Methyl ethyl ketone 46.5% by weight Toluene 46.5% by weight The adhesiveness and printability of the ink for the produced thermal transfer ribbon were evaluated. evaluated. Table 1 shows the evaluation results.

Examples 5 and 6, Comparative Example 3 o- at 25 ° C.
0.62 intrinsic viscosity measured by chlorofinol melting
The quaternary phosphonium salt of sulfonic acid shown in Table 1 was contained in an amount corresponding to the content shown in Table 1, and Comparative Example 3 contained no quaternary phosphonium salt of sulfonic acid.
A biaxially oriented film was prepared in the same manner as in Example 1 under the film-forming conditions shown in Table 1, using polyethylene-2,6-naphthalate containing 0.4% by weight of spherical silica particles of μm. Next, a thermal transfer ribbon was produced and evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

[0076]

[Table 1]

[0077]

According to the present invention, when used as a ribbon for a thermal transfer printer, the printing performance is excellent, there is no blurring of the ink even when printing at high speed, and there is no wrinkling of the ribbon due to rubbing with the head. A biaxially oriented polyester film excellent in the above can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an AC volume resistivity meter.

[Explanation of symbols]

 1: Measurement sample 2: Column-shaped lower electrode (diameter: 20 cm) 3: Upper electrode (diameter: 5.6 cm, thickness: 0.2 cm) 4: Power supply device 5: Temperature detection end 6: Power supply 7: Temperature display section 8: Power supply 9: Standard resistance 10: Electron meter 11: Heat insulation box

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08J 7/00 CFD C08J 7/00 301 4F210 301 7/04 CFDB 7/04 CFD C08K 5/19 C08K 5/19 5 / 49 5/49 C08L 67/02 C08L 67/02 B32B 27/36 // B32B 27/36 B41M 5/26 B B29K 67:00 B29L 7:00 9:00 F term (reference) 2H111 AA01 AA15 AA27 AA33 BA07 BA62 BB06 BB08 DA01 DA04 4F006 AA35 AA56 AB20 AB24 AB35 AB37 BA01 4F071 AA43 AA80 AF06 AF37 AH16 BB08 BC01 4F073 AA01 BA23 BA24 BB01 BB09 EA65 GA01 GA05 4F100 GB90 JL02 4F210 AA21 AA03 AB13 AA03 AA03 AB13 QG18 QW12

Claims (8)

[Claims] 1. A biaxially oriented polyester film having a center line average roughness of 10 to 40 nm, wherein the molten biaxially oriented polyester film has an AC volume resistivity of 6 × 10 ^8.
A biaxially oriented polyester film having a Ω · cm or less and a difference in height (thickness difference) between adjacent peaks and valleys in a continuous thickness chart of the film is within 8% of an average thickness. 2. The biaxially oriented polyester film contains a quaternary phosphonium sulfonic acid salt having an ester-forming functional group in an amount of 0.1 to 40 mmol% based on a bifunctional carboxylic acid component, and has a melting point measured by DSC. The peak difference between adjacent peaks and valleys (thickness difference) in the continuous thickness chart of the film is within 5% of the average thickness and the interval between the peaks and valleys is 10c.
The biaxially oriented polyester film according to claim 1, which has a space factor of 1 to 23%. 3. The biaxially oriented polyester film according to claim 1, wherein the refractive index in the longitudinal direction is 1.77 or more. 4. At least one resin selected from the group consisting of water-soluble or water-dispersible resins of urethane, polyester, acrylic and vinyl resin-modified polyester is applied to at least one surface of the film before completion of the orientation crystallization. The biaxially oriented polyester film according to claim 1, further comprising a coating layer that has been subjected to drying, stretching, and heat setting after the application. 5. The biaxially oriented polyester film according to claim 1, wherein the quaternary phosphonium sulfonic acid salt having an ester-forming functional group is a compound represented by the following formula (1). Embedded image (In the formula (1), n is 1 or 2, A is an n + 2 divalent aliphatic group or aromatic group having 2 to 18 carbon atoms, and X ¹ and X ² are each a hydrogen atom or an ester-forming group. R ¹ , R ² , R ³ and R ⁴ each represent an alkyl group having 1 to 18 carbon atoms, a benzyl group or a 6-1
2 aryl groups. X ¹ and X ² may be the same or different from each other, but they are not both hydrogen atoms. R ¹ , R ² , R ³ and R ⁴ may be the same or different. ) 6. The biaxially oriented polyester film according to claim 1, wherein the main component constituting the biaxially oriented polyester film is polyethylene terephthalate. 7. The biaxially oriented polyester film according to claim 1, wherein the main component constituting the biaxially oriented polyester film is polyethylene-2,6-naphthalate. 8. The biaxially oriented polyester film according to claim 1, which is used as a base film for a thermal transfer ribbon.