JP2000103874A - Biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a biaxially oriented polyester film suitable for thermal transfer ribbons as can give transfer pictures with excellent gradation and as has excellent productivity with few breaks and excellent flatness. SOLUTION: This film has the following characteristics: (a) the containing of two kinds of fine particles as follows; A: calcium carbonate with an average particle dia. of 0.5-4 μm, in a content 0.1-2 wt.%. B: aluminum silicate with an average particle dia. of 0.1-2.0 μm, in a content of 0.05-1 wt.%. (b) an average roughness along center line (Ra), 10-40 nm. (c) a space factor, 1-19%. (d) projections with heights of more than 1.5 μm, 300-700/cm2 (e) a height difference between a crest and a bottom adjacent each other (a thickness difference) in a continuous thickness chart, within 8% of the average thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film, and more particularly, it is suitably used for a thermal transfer printer ribbon. The present invention relates to a biaxially oriented polyester film having no transfer unevenness and excellent in printing performance.

[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.
-299389).

[0003] Among the thermal transfer recording systems, the sublimation type thermal transfer system has 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, a higher printing speed has been required, and as a measure against this, a thinner base film has been required in order to efficiently transmit heat from a thermal head during printing.

[0004] Although there is a demand for such a thin film, simply reducing the thickness of a conventional stretched film causes a problem that workability in a dye ink coating process and a slit process is deteriorated.

[0005] The above workability depends on the slipperiness of the film surface, and in general, a method of giving fine irregularities to the film surface of a thermoplastic resin film in order to improve the slipperiness is known. Examples of such a method include adding inert particles during or after polymerization of a thermoplastic polymer that is a raw material of a film (external particle addition method), or a part of a catalyst or the like used at the time of polymerization of a thermoplastic polymer. Alternatively, a technique of precipitating the whole in a polymer in a reaction step (internal particle precipitation method) is known.

However, in the method for producing an ultra-thin film as in the present invention, when the polymer to which the inert inorganic fine particles are added at the same concentration is thinned, the number of inert inorganic fine particles per unit area decreases, The distance between the fine particles on the surface is widened, the film surface tends to be too flat, and the slipperiness tends to decrease. Therefore, in order to compensate for the decrease in slipperiness due to thinning, it is necessary to increase the concentration of the added inert inorganic fine particles or increase the particle size as the film thickness becomes thinner.

In this case, voids are formed around the interface, that is, around the inert inorganic fine particles due to poor affinity between the inert inorganic fine particles and the thermoplastic polymer, particularly during melt extrusion or drawing at a high draft ratio. The mechanical properties (for example, mechanical strength) of the obtained film are remarkably reduced, and the film is liable to be broken during the production of the film, thereby lowering the productivity.

[0008]

SUMMARY OF THE INVENTION The present invention solves these problems and provides a thermal transfer ribbon which is capable of obtaining a transferred image excellent in gradation, excellent in productivity with little breakage, and excellent in flatness. An object is to provide a suitable biaxially oriented polyester film.

[0009]

According to the present invention, calcium carbonate having an average particle size of 0.5 to 4 μm is contained in an amount of 0.1 to 2% by weight,
And a biaxially oriented polyester film containing 0.05 to 1% by weight of aluminum silicate having an average particle size of 0.1 to 2.0 μm, and having a center line average roughness of 10%.
４０40 nm, space factor is 1-19%,
The projections having a height of 1.5 μm or more on the film surface are 300 to
A biaxially oriented polyester film having a thickness of 700 / cm ² 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. It is.

[Polyester] The biaxially oriented polyester film of the present invention mainly comprises polyester, for example, polyethylene terephthalate or polyethylene-2,6-naphthalate. In addition to the above components, components other than the random polymer component having ethylene terephthalate or ethylene-2,6-naphthalate as a repeating unit are also preferably used as the main ester-forming component. However, from the viewpoint of versatility and cost, ethylene terephthalate or ethylene- A 2,6-naphthalate component is preferably used. In addition, the amount of the third
Components may be introduced. When the content is 20 mol% or less, the film does not extremely impair the essential properties of the main component.

Suitable copolymerizable components are 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, phenylindanedicarboxylic acid, diphenyletherdicarboxylic acid and lower alkyl esters thereof An oxycarboxylic acid such as p-oxyethoxybenzoic acid and a lower alkyl ester thereof; propylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol; 1,6-hexa Diol, 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 can be mentioned.

Polyesters containing polyethylene terephthalate or polyethylene-2,6-naphthalate as a main component are partially or partially substituted with hydroxyl groups and / or carboxyl groups at the terminals by monofunctional compounds such as benzoic acid and methoxypolyalkylene glycol. It may be entirely blocked or modified with a very small amount of a trifunctional or higher functional ester-forming compound such as glycerin or pentaerythritol within a range where a substantially linear polymer can be obtained. You may. These polyesters may be blended instead of copolymerized.

[Additional fine particles] The biaxially oriented polyester film of the present invention has many fine projections on its surface. These numerous fine projections are derived according to the invention from calcium carbonate and aluminum silicate, which are contained dispersed in the polyester.

In the present invention, the calcium carbonate contained in the polyester has an average particle size of 0.5 to 4.0 μm.
m, preferably 0.5 to 2.0 μm.

Here, the "average particle diameter" means the "equivalent spherical diameter" of the particle at a point of 50% by weight of the total particles measured. "Equivalent spherical diameter" means the diameter of an imaginary sphere (ideal sphere) having the same volume as a particle, and can be calculated from an electron micrograph of the particle or measurement by a normal sedimentation method.

If the average particle size of the calcium carbonate is less than 0.5 μm, wrinkles are liable to occur because the air squeezing property is poor (the entrapped air is hard to escape) when the film is wound on a master roll or a product roll. Unsatisfactory, the workability in the processing step is reduced, which is not preferable.
On the other hand, if the average particle size exceeds 4.0 μm, the film surface becomes too rough, the space factor increases, and furthermore, the dielectric breakdown voltage is reduced, and the number of insulation defects is increased. The average particle size of calcium carbonate may be larger than the film thickness.

In the present invention, the amount of calcium carbonate added must be 0.1 to 2% by weight in the polyester, and preferably 0.1 to 1% by weight. If the amount of calcium carbonate added is less than 0.1% by weight, the air squeezing property at the time of winding the film becomes poor, while 2% by weight
If it exceeds, the surface of the film is too rough, leading to a decrease in dielectric breakdown voltage and the like.

The calcium carbonate used in the present invention includes:
Any material can be used. Naturally calculated coal stone, chalk (chalk), calcite crystals such as precipitated calcium carbonate generated by chemical method from coal stone, and coal milk are reacted with carbon dioxide at high temperature. Examples thereof include argonite crystals, vaterite crystals, and combinations thereof. Heavy calcium carbonate (calcite crystal) obtained by mechanically grinding coal stone can also be used.

In the present invention, the aluminum silicate contained in the polyester has an average particle size of 0.1 to 2.0.
μm, preferably 0.3 to 1.2 μm, and the content is 0.05 to 1% by weight.

The average particle size of aluminum silicate is 0.1 μm
If it is less than 2.0 μm, the slipperiness of the film will be impaired and the workability will deteriorate, and if it exceeds 2.0 μm, the film surface will be too rough and the space factor will increase, which is not preferred.

When the content of aluminum silicate is 0.05
If the amount is less than 1% by weight, the air squeezing property at the time of winding the film becomes poor. On the other hand, if the amount is more than 1% by weight, the film surface becomes too rough and the space factor increases.

In the present invention, the aluminum silicate refers to a plate-like aluminosilicate, and any one of them can be used, and examples thereof include kaolin clay made of naturally occurring kaolin mineral. In addition, kaolin clay
It may have been subjected to a purification treatment such as washing with water.

In the present invention, the polyester film contains calcium carbonate having an average particle size of 0.5 to 4 μm and aluminum silicate having an average particle size of 0.1 to 2.0 μm. If the workability of the film is to be ensured only with calcium carbonate, the space factor of the film is undesirably too large. On the other hand, with aluminum silicate alone, large projections cannot be formed, and workability and space factor cannot be compatible.

The calcium carbonate and aluminum silicate contained in the polyester film of the present invention may be added before the polymerization of the polyester polymer, during the polymerization reaction, or may be kneaded in an extruder when pelletizing after the polymerization. Further, it may be added at the time of melt extrusion into a sheet form, dispersed in an extruder and extruded, but is preferably added before polymerization.

To add calcium carbonate and aluminum silicate to the polyester, any known method may be employed.
When the addition is performed before the polymerization of 2,6-naphthalate, it is preferable that calcium carbonate and aluminum silicate are added to ethylene glycol and dispersed in the polymer by performing ultrasonic vibration or the like.

By adding two kinds of calcium carbonate and aluminum silicate fine particles, a biaxially oriented polyester film having an average surface roughness of 10 to 40 nm can be obtained. The average surface roughness of the film is 10
If it is smaller than nm, sufficient slip properties cannot be obtained, and it becomes difficult to wind up. On the other hand, when the average surface roughness is larger than 40 nm, when high-speed printing is performed by a thermal transfer printer, heat conduction is deteriorated and the printing becomes unclear.

Further, in addition to these two kinds of fine particles, a lubricant smaller than the particle diameter of the above two kinds of fine particles may be further added as a third component so as to fall within the above range of roughness.

[Coarse protrusions] The surface of the biaxially oriented polyester film used in the present invention has a large number of protrusions derived from the above-mentioned calcium carbonate and aluminum silicate.
The protrusions having a height of 1.5 μm or more are 300 to 70.
It has to be 0 / cm ² . When the number of protrusions having a height of 1.5 μm or more is less than 300 / cm ² , the distance between the protrusions is widened, the film surface is flattened, and the slipperiness is reduced. On the other hand, when the number of protrusions having a height of 1.5 μm or more exceeds 700 / cm ² , the surface of the film becomes rough, and in some cases, voids generated around the contained fine particles may cause breakage during film formation or stretching during film formation. Breakage increases, which is not preferable.

[Additives] The biaxially oriented polyester film of the present invention may contain additives such as a stabilizer, a dye, an ultraviolet absorber, and a flame retardant, if desired, in addition to the silica fine particles described above.

[Space Factor] The biaxially oriented polyester film of the present invention has a space factor of 1
Must be ~ 19%. 1% space factor
If it is less than 19%, the slipperiness and workability (handling property) of the film will be insufficient, while if it exceeds 19%, the surface will be too coarse, possibly causing breakage, which is not preferable.

The space factor (SF) is calculated based on the film weight w (g) of the film 100 cm ² and the density d.
(G / cm ³ ) to determine the thickness t ₁ (μm) by the gravimetric method.
When the thickness of one sample film determined using a micrometer is defined as t ₂ (μm), ten films of cm square are stacked, and the thickness is calculated by the following equation. SF (%) = 100−t ₁ / t ₂ × 100

[Thickness] The thickness of the biaxially oriented polyester film of the present invention is preferably 0.5 to 10 μm. Thickness 1
When the thickness exceeds 0 μm, it takes time for heat conduction during printing, which is not suitable for high-speed printing. On the other hand, when the thickness is less than 0.5 μm, the tension 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 a length of 5 m and 1 m in the longitudinal direction and the width direction of the film, and a continuous thickness chart (thickness versus 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 Adhesion Layer] A thermal transfer ribbon can be produced by providing a thermal transfer ink layer on at least one surface of the biaxially oriented polyester film of the present invention. At that time, from the group of urethane-based resin, polyester-based resin, acrylic-based resin, and vinyl-based resin-modified polyester, on the surface of the film to which the ink layer is applied, for the purpose of improving the adhesion between the film and the thermal transfer ink layer. It is preferable to have a coating layer made of at least one water-soluble or water-dispersible resin selected.

The urethane resin used as the coating layer can be exemplified by the following polyvalent hydroxy compound, polyvalent isocyanate compound, chain extender, cross-linking agent, and the like. That is, as the polyvalent hydroxy compound, polyoxyethylene glycol, polyoxypropylene glycol, polyethers such as polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polyesters such as polycaprolactone, polycarbonates,
Acrylic polyols, castor oil, and the like can be used. As polyvalent isocyanate compounds, tolylene diisocyanate, phenylene diisocyanate, 4,
4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate,
4,4′-dicyclohexylmethane diisocyanate,
For example, isophorone diisocyanate can be used. Examples of the chain extender or the crosslinking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, and ethylenediamine.
Sodium acrylate adduct, 4,4'-diaminodiphenylmethane, 4,4'-diaminodicyclohexylmethane, water and the like can be used. One or more of these compounds are appropriately selected, and a polyurethane resin is synthesized by a usual polycondensation-crosslinking reaction.

The polyester-based resin used as the coating layer can be exemplified by the following polyvalent carboxylic acids and polyvalent hydroxy compounds as constituents thereof. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, phthalic 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 trimellitate, and ester-forming derivatives thereof, and the like. Examples of the polyvalent hydroxy compound include 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, poly Tetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate and the like can be used. One or more of these compounds are appropriately selected, and a polyester resin 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 as the coating layer preferably contains alkyl acrylate or alkyl methacrylate as a main component.
It is a water-soluble or water-dispersible resin containing 0 to 10 mol% of a copolymerizable vinyl monomer component having a functional group. Vinyl monomers having a functional group copolymerizable with an alkyl acrylate or an alkyl methacrylate have a carboxyl group or a salt thereof, an acid anhydride group, a sulfonic acid group or a salt thereof, an amide group or an alkylol group as a functional group. It is a vinyl monomer having an amide group, an amino group (including a substituted amino group) or an alkylolated amino group or a salt thereof, a hydroxyl group, an epoxy group and the like. Of these, particularly preferred are a carboxyl group or a salt thereof, an acid anhydride group, an epoxy group and the like. Two or more of these groups may be contained in the resin. Examples of the alkyl group of the alkyl acrylate and the alkyl methacrylate include a methyl group, an ethyl group, an n-propyl group, an isopropyl group,
-Butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, cyclohexyl group and the like.

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 as the coating layer can be synthesized by polymerizing the vinyl resin in the water-soluble or water-dispersible resin of polyester. Examples of components constituting the polyester include the following polybasic acids or their ester-forming derivatives and polyols or their ester-forming derivatives. That is, polybasic acid components include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, and pyromellitic acid And dimer acid. A copolymerized polyester resin is synthesized using two or more of these acid components. Also, it is possible to use a small amount of an unsaturated polybasic acid component such as maleic acid, itaconic acid and the like, and hydroxycarboxylic acids such as p-hydroxybenzoic acid and the like. 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. , Poly (tetramethylene oxide)
Glycol and the like. Two or more of these can be used. Examples of the vinyl resin component include vinyl monomers as exemplified below. For example, alkyl acrylate, alkyl methacrylate (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, and the like); 2-hydroxyethyl acrylate, 2-
Hydroxy-containing monomers such as hydroxyethyl methacrylate, 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate; 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, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, etc.),
N-alkoxyacrylamide, N-alkoxymethacrylamide, N, N-dialkoxyacrylamide,
N, N-dialkoxymethacrylamide (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), N-methylolacrylamide, N-
Amide group-containing monomers such as methylol methacrylamide, N-phenylacrylamide and N-phenylmethacrylamide; epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; acrylic acid, methacrylic acid, itaconic acid,
Monomers containing a carboxy group or a salt thereof such as maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); maleic anhydride, itacone anhydride Monomers of acid anhydrides such as acids; vinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether,
Vinyl trialkoxy silane, alkyl maleic acid monoester, alkyl fumaric acid monoester, alkyl itaconic acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene,
Examples include monomers such as vinyl chloride, vinyl acetate, and butadiene. Further, other than these monomers can be used. These monomers can be copolymerized using one kind or two or more kinds.

The coating solution of the coating layer of the present invention may contain some organic solvent as long as it does not affect the water-soluble or water-dispersible resin of the above resin and 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,
Examples thereof include alkylamine hydrochloride and betaine-type surfactant.

The easy-adhesion layer according to the present invention contains an isocyanate-based compound, an epoxy-based compound, an oxazoline-based compound, and an aziridine as a cross-linking agent in order to improve sticking property (blocking property), water resistance, solvent resistance and mechanical strength. It may contain a compound, a melamine compound, a silane coupling agent, a titanium coupling agent, a zirco-aluminate coupling agent, and the like. If the resin component of the intermediate adhesive layer 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.
Further, in order to improve the sticking property and the sliding property, silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide, barium sulfate, carbon black, sulfide are used as inorganic fine particles in the coating layer. Molybdenum, antimony oxide sol, and the like may be contained as organic fine particles, such as polystyrene, polyethylene, polyamide, polyester, polyacrylate, epoxy resin, silicone resin, and fluorine resin. Further, if necessary, 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 may be contained.

This coating solution is preferably applied to one or both sides of the polyester film before the completion of the crystal orientation in the polyester film production process. Coating may be performed separately from the polyester film manufacturing process, but in this case, dust and dirt are likely to be involved, and the portion becomes a defect during printing, so a clean atmosphere is desirable. From these points, coating during the manufacturing process is preferred from these points. 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.

[Film Production Method] 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 the film. It can be produced more advantageously by performing a tensioning treatment. For example, the unstretched film is biaxially stretched at a temperature of Tg to (Tg + 60) ° C. (Tg: glass transition temperature of polyester) in the longitudinal direction and the transverse direction at a magnification of 2.0 to 6.0 times, preferably at 225 ° C. or more. Heat set at 235-250 ° C for 1-100 seconds. In the heat setting, it is desirable that the zone is divided into two or more, preferably four or more, because the temperature can be controlled for each zone. 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 the relaxation treatment, the relaxation treatment is performed until the film is wound around a roll after heat setting. The relaxation treatment method is to reduce the tenter width in the middle of the heat fixing zone and reduce 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-up speed is reduced with respect to the supply speed of the film under a temperature condition not lower than the glass transition temperature of the film and not higher than the melting temperature. In the meantime, a method of heating with an IR heater, a method of transporting the film on a heating transport roll and reducing the speed of the transport roll after the heating transport roll, and a method of feeding the film while transporting the film over a nozzle that blows out hot air after heat fixing. How to slow down the take-up speed over the speed,
Alternatively, the film is wound on a film forming machine, and then the film is conveyed onto a heated conveying roll to reduce the speed of the conveying roll, or the roll speed after the heating zone is heated while being conveyed in a heating oven or a heating zone by an IR heater. There is a method in which the speed is reduced from the roll speed before the zone, and any method may be used. The relaxation process is performed by setting the deceleration rate of the take-up side speed to the supply side speed to 0.1 to 3%. preferable.

In particular, in the present invention, in order to keep the heat shrinkage of the film within a range suitable for the thermal transfer ribbon, in addition to the relaxation treatment, the width of the tenter is expanded in the middle of the heat fixing zone, and the tension treatment in the film width direction is performed. You may give 0-3%.
Such a treatment is not limited to any method as long as the heat shrinkage falls within an appropriate range of the film of the present invention. Further, it is preferable that the processing is performed in the heat fixing zone where the temperature is the highest, in order to form the dimensionally stable structure.

If necessary, a cooling zone can be provided to cool the film to a temperature around Tg ± 40 ° C. Thereby, it becomes a flat film with little unevenness of thickness, which is preferable.

[Thermal Transfer Ink Layer] A thermal transfer ribbon can be produced by providing a thermal transfer ink layer on at least one surface, particularly one surface of the biaxially oriented polyester film of the present invention. Such a thermal transfer ink layer is not particularly limited, and a known one can be used. That is, a binder component, a coloring component, and the like are used as main components, and a softener, a plasticizer, a dispersant, and the like are added in appropriate amounts as needed. 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 Prevention Layer] The biaxially oriented polyester film of the present invention is particularly preferably used as a thermal transfer ribbon in which the above-mentioned easy-adhesion layer is provided on one side of the film, and the thermal transfer ink layer is provided thereon. And a laminate in which an anti-fusing layer is provided on the opposite film surface.

The anti-fusing layer is provided to prevent sticking of the thermal head portion, and specifically, a layer formed of a polyol, for example, a polyalcohol, a polyisocyanate compound and a polyester phosphate compound is provided. .

The polyalcohol is preferably a polyvinyl butyral resin having a hydroxyl group, a polyester resin, a polyether resin, a polybutadiene resin, an acrylic polyol, a nitrocellulose resin, a cellulose acetate resin, a cellulose acetate resin, or a prepolymer of urethane or epoxy. No.

Further, as a method for forming the anti-fusing layer, a known method can be used, and even if it is provided on an unstretched film or on a film after longitudinal stretching in the film production process,
It may be provided after it is once wound as a biaxial film. This is preferable because the thermal history applied to the base from the thermal head after processing into the transfer ribbon can be reduced.

[0057]

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 specified in the present invention will be described below.

1. Particle size of particles (1.1) Particle size of powder Measured using a Shimadzu CP-50 type centrifugal particle size analyzer. The particle size corresponding to 50% by mass was read from the cumulative curve of particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, and this value was taken as an average value (“particle size measurement technology”, (See Nikkan Kogyo Shimbun, 1975, pp. 242 to 247) (1.2) Particle Size of Film In Film A small piece of the sample film is fixed on a sample stage for a scanning electron microscope and sputtered by JEOL Ltd. Equipment (JIS-11
The surface of the film was subjected to 0.25 kV under a vacuum of 1 × 10 ⁻³ torr using a 00 type ion sputtering apparatus).
Ion etching was performed for 10 minutes under the condition of 1.25 mA. Further, gold sputtering was performed using the same apparatus, observed at a magnification of 1 to 30,000 times with a scanning electron microscope, and at least 1 × with Luzex 500 manufactured by Nippon Regulator Co., Ltd.
The area equivalent particle size (Di) of 00 particles was determined. The number average value of the area equivalent (Di) represented by the following formula is calculated as the average particle diameter (D).
And

[0059]

(Equation 1)

2. Density This is a value measured by a flotation method at 25 ° C. in a density gradient tube using an aqueous solution of calcium nitrate.

3. Film thickness and thickness irregularity 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

4. Surface Roughness (Center Line Surface 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 obtain the surface roughness.

5. Space factor (SF) Film weight w (g) and density d (g) of a sample 100 cm ²
/ 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

6. Number of protrusions with a height of 1.5 μm or more NIKON two-beam microscope OPTIPHOTO (wavelength λ =
Using 546 nm), the projection height was calculated using the fact that the interference fringes were 2 / λ, and the projections having a height of 1.5 μm or more per 1 cm ² were counted.

7. Winding property The degree of wrinkles entering when the formed base film was slit into a predetermined width was observed and evaluated according to the following criteria. Rank A: Wrinkles do not occur, and winding can be performed extremely stably. Rank B: Wrinkles hardly occur, and stable winding is possible. Rank C: Wrinkles sometimes occur, and stable winding cannot be performed. Rank D: Large wrinkles occur frequently, and substantially stable winding is impossible.

8. Adhesiveness A mending tape 810 manufactured by Sumitomo 3M Co., Ltd. is attached to the ink layer surface of the produced thermal transfer ribbon and rapidly peeled off, and the adhesiveness is evaluated as follows according to the degree of peeling of the ink layer. 5: no ink layer peeling at all 4: ink layer peeling area less than 10% 3: ink layer peeling area 10 to 30% 2: ink layer peeling area 31 to 80% 1: ink layer peeling area exceeds 80%

9. Printability Image receiving sheet VY-200 (standard paper, trade name, manufactured by Hitachi, Ltd.) and printer Hitachi VY-200
(Hitachi, Ltd., trade name) was printed so as to have the maximum optical density. With respect to the produced thermal transfer ribbon, printability and wrinkles generated on the ribbon were evaluated according to the following criteria. ：: The image is printed clearly. Δ: Printing density is not uniform. X: The ribbon is wrinkled and the print is disturbed.

[Example 1] Dimethyl terephthalate 100
0.024 parts of manganese acetate tetrahydrate is added to a mixture of 60 parts by weight of ethylene glycol and
The transesterification reaction was performed while gradually raising the temperature to 0 ° C. On the way, when the reaction temperature reached 170 ° C., 0.019 parts of antimony trioxide was added, and further, calcium carbonate and aluminum silicate having the average particle size shown in Table 1 were added in the amounts shown in Table 1. Subsequently, a transesterification reaction is performed, and after the transesterification reaction is completed, trimethyl phosphate is dissolved in ethylene glycol at 135 ° C. for 5 hours for 1.1 to 1.1 hours.
A solution heat-treated under a pressure of 1.6 kg / cm ² (0.018 part in terms of trimethyl phosphate) was added. Thereafter, the reaction product was transferred to a polymerization reactor, the temperature was raised to 290 ° C., and a polycondensation reaction was carried out under a high vacuum of 0.2 mmHg or less, so that the intrinsic viscosity measured with an o-chlorofinol solution at 25 ° C. was 0%. .62 polyester was obtained.

This polymer was melted and extruded into a sheet by an extruder and a T-die, and the melt was extruded into a water-cooled casting drum.
It was adhered at a speed of 7.5 m / min and solidified by cooling to obtain an unstretched sheet. The unstretched film is stretched by a high-speed roll at 150 m / min.
Stretched 4.6 times at 5 ° C. On the side of the film after longitudinal stretching where the ink layer was not applied, the following composition 1 was used as a fusion preventing layer.
Is applied with a gravure coater so that the coating thickness after drying becomes 0.5 μm, and the coating thickness after drying the coating composition of the following composition 2 as an easy adhesion layer on the side to which the ink layer is applied is 0.
Coating was performed with a gravure coater so that the thickness became 1 μm. Thereafter, the film is successively biaxially stretched 3.8 times at 110 ° C. in the transverse direction (width direction), and heat-set at 220, 238, 180, and 90 ° C. for 2 seconds in the first, second, and third heat fixing and cooling zones, respectively. After cooling, 2% of tension treatment in the width direction in the second heat setting zone
Then, a biaxially oriented film having a thickness of 3.0 μm was obtained.

<Coating composition 1> 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 2 (acrylic + polyester + epoxy)
Acrylic resin 42% by weight solid content (65% by mole of methyl methacrylate / 28% by mole of ethyl acrylate)
2-hydroxyethyl methacrylate 2 mol% / N-methylol acrylamide 5 mol%) Polyester resin 42% by weight in solid content (35 mol% of terephthalic acid / 13 mol% of isophthalic acid as an acid component / 5-sodium sulfoisophthalic acid 2) Mol%, ethylene glycol 45 mol% / diethylene glycol 5 mol% as glycol component) Epoxy crosslinking agent 6% by weight of solid content (N, N, N
N ', N'-tetraglycidyl-m-xylylenediamine) Wetting agent 10% by weight of solid content (lauryl polyoxyethylene) Regarding the obtained biaxially oriented polyester film, the number of protrusions, unevenness of thickness, and valley of thickness are obtained. , Thickness, and space factor were determined.

Next, a transfer ink having the following composition was applied to the surface opposite to the anti-fusing layer using a gravure coater so that the thickness of the coating film 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 Evaluation of ink adhesion and printability of prepared thermal transfer ribbon did. Table 1 shows the evaluation results.

Examples 2-3 and Comparative Examples 1-3 Biaxially oriented films and thermal transfer ribbons comprising the same in the same manner as in Example 1 except that the type and amount of the lubricant to be added are changed to the values shown in Table 1. It was created. Table 1 shows the evaluation results of the biaxially oriented film and the thermal transfer ribbon.

Example 4 Polyethylene having an intrinsic viscosity of 0.62 measured with an o-chlorofinol solution at 25 ° C.
3. Using 2,6-naphthalate, at 144 ° C. in the longitudinal direction.
Lateral stretching at 137 ° C. and 4.0 times in a tenter oven was performed five times. Next, a biaxially oriented film was prepared in the same manner as in Example 1 except that heat treatment, relaxation treatment and cooling treatment were performed at the heat setting temperatures shown in Table 1, and a thermal transfer ribbon was prepared therefrom. Table 1 shows the evaluation results of the biaxially oriented film and the thermal transfer ribbon.

Comparative Examples 4 and 5 A biaxially oriented film and a thermal transfer ribbon comprising the same were prepared in the same manner as in Example 4 except that the type and amount of the lubricant to be added and the stretching conditions were changed to the values shown in Table 1. . Table 1 shows the evaluation results of the biaxially oriented film and the thermal transfer ribbon.

[0075]

[Table 1]

[0076]

According to the present invention, a biaxially oriented polyester having a moderately roughened surface, excellent workability during film forming, less breakage, and excellent flatness, particularly suitable for a thermal transfer ribbon. A film can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08K 3/34 C08L 67/02 C08L 67/02 B41M 5/26 B // B29K 67:00 105: 16 B29L 7:00 F-term (reference) 2H111 AA01 AA26 AA27 AA31 AA50 AB05 AB07 CA03 CA04 CA23 CA30 CA41 CA44 4F071 AA45 AA46 AB21 AB26 AH16 BB08 BC01 BC12 BC14 BC15 BC16 4F210 AA24 AA26 AB16 AE01 AG01 AH81 QA08 Q08 Q06 Q08 CFQ DE236 DJ007 FD016 FD017 GS00

Claims (5)

[Claims] 1. A calcium carbonate having an average particle size of 0.5 to 4 μm is 0.1 to 2% by weight, and an average particle size is 0.1 to 2%.
A biaxially oriented polyester film containing 0.05 to 1% by weight of 2.0 μm aluminum silicate, wherein the film has a center line average roughness of 10 to 40 nm, a space factor of 1 to 19%, and Surface height
The number of protrusions of 5 μm or more is 300 to 700 / cm ² or less, and the difference in height (thickness difference) between adjacent peaks and valleys in the continuous thickness chart of the film is within 8% of the average thickness. Biaxially oriented polyester film. 2. The biaxial orientation according to claim 1, wherein the difference in height (thickness difference) between adjacent peaks and valleys is within 5% of the average thickness, and the distance between adjacent peaks and valleys is 10 cm or more. Polyester film. 3. The biaxially oriented polyester film according to claim 1, wherein the biaxially oriented polyester film mainly comprises polyethylene terephthalate. 4. The biaxially oriented polyester film according to claim 1, wherein the biaxially oriented polyester film mainly comprises polyethylene-2,6-naphthalate. 5. The biaxially oriented polyester film according to claim 1, which is used as a base film for a thermal transfer ribbon.