JPH11321127A - Polyester film for thermal transfer printer ribbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the thermal dimension property of a film or a ribbon, make the back face coat layer extremely thin while suppressing the thermal deformation to a level wherein there is no problem, and thus, improve the printing quality. SOLUTION: On one of the faces of a biaxially drawn polyester film with a thickness of 1.5-13 μm, a back face coat layer is provided, and on the other face, a heat-melting ink layer is provided for a thermal transfer film, and for such a thermal transfer film, there is a point where the gradient of a temperature dimension change curve in the longitudinal direction of the film, changes from negative to positive, and a temperature at the point (Tinf) is 220 deg.C or higher, and also, a dimensional change rate to the original length of the film at the point is -5-+1%, and also, the back face coat layer is provided by a ratio of 0.001-0.01 g/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a thermal transfer printer ribbon for a color printer or the like based on a biaxially oriented polyester film, and more particularly to a thermal transfer printer ribbon capable of improving the image quality of an image. It relates to a polyester film.

[0002]

2. Description of the Related Art In recent years, a full-color printer capable of obtaining a high-definition and clear image comparable to a color photograph has been realized, particularly in a variable dot type color thermal transfer printer and a sublimation type printer.
There is a demand for further improvement in image quality.

In order to achieve higher image quality in such a color printer, it is important that the thermal transfer printer ribbon can be brought into uniform contact with the thermal head. If the contact with the thermal head is uneven, the printed matter becomes rough and the image quality deteriorates. Further, if a part of the back coat layer of the thermal transfer printer ribbon adheres to the thermal head, it causes image quality to deteriorate.

[0004] In order to suppress the adhesion of the back coat layer to the thermal head, it is conceivable to make the back coat layer thin. However, simply reducing the thickness reduces the printing sensitivity when the ribbon is thermally deformed. Image quality decreases.

[0005]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to improve the thermal dimensional characteristics of films and ribbons and to reduce the thermal deformation of the films and ribbons to a level that does not cause a problem. An object of the present invention is to make a coat layer extremely thin, thereby improving print quality.

[0006]

In order to solve the above-mentioned problems, a polyester film for a thermal transfer printer ribbon of the present invention comprises a back coat layer on one surface of a biaxially stretched polyester film having a thickness of 1.5 to 13 μm. A heat-transferable film provided with a heat-fusible ink layer on the other surface, wherein there is a point where the gradient of the temperature dimension change curve in the longitudinal direction of the film changes from negative to positive. ) Is 220 ° C. or higher, and the dimensional change rate of the film at the point with respect to the original length is −5 to + 1%;
And the said back coat layer is 0.001-0.01 g / m
It is characterized by being provided in the ratio of ² .

That is, in the present invention, in order to solve the above problems, the thickness of the biaxially stretched polyester film, which is the base film for the ribbon, is set to an optimum range, and the deformation of the thermal head due to heat is suppressed. The thermal dimensional change rate in the vertical direction is controlled within a specific range so that the ribbon is less likely to be thermally deformed, and the back coat layer is formed as an extremely thin layer so that print quality can be improved.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail together with preferred embodiments. Polyester film for thermal transfer printer ribbon according to the present invention,
It consists of a biaxially stretched polyester film. Unstretched films and uniaxially stretched films do not provide desired high mechanical properties in both the longitudinal and transverse directions.

In the present invention, the polyester is a polyester comprising dibasic acid and glycol as constituent components,
As the aromatic dibasic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenylsulfondicarboxylic acid, diphenylether dicarboxylic acid, diphenoxyethanedicarboxylic acid, cyclohexanedicarboxylic acid, diphenylketonedicarboxylic acid, phenylindanedicarboxylic acid, Sodium sulfoisophthalic acid, dibromoterephthalic acid and the like can be used.
As the alicyclic dibasic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, hexahydroterephthalic acid and the like can be used. Further, as the aliphatic dibasic acid, oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid and the like can be used. As the glycol, ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, or the like can be used as an aliphatic diol, and naphthalene diol,
2,2-bis (4-hydroxydiphenyl) propane,
2,2-bis (4-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, hydroquinone, tetrabromobisphenol A, and the like can be used. Examples of alicyclic diols include cyclohexanedimethanol, cyclohexanediol, and the like. Can be used.

Further, a polyfunctional compound having three or more functional groups within a range in which the polyester is substantially linear, such as glycerin, trimethylolpropane, pentaerythritol,
Trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, gallic acid or the like may be copolymerized, or a monofunctional compound such as o-benzoylbenzoic acid or naphthoic acid may be added and reacted. Polyethers such as polyethylene glycol and polytetramethylene glycol and aliphatic polyesters represented by polycaprolactone may be copolymerized.

As the polyester, two or more polyesters may be blended. For example, if 50% or more of the polyester is used, a polyester other than the polyester may be blended.

The thickness of the biaxially stretched polyester film constituting the polyester film for a thermal transfer color printer ribbon according to the present invention is in the range of 1.5 to 13 μm, and preferably in the range of 2 to 6 μm. The thickness is 1.
If the thickness is less than 5 μm, the ribbon is deformed by heat, and the image quality is deteriorated. On the other hand, if the thickness is larger than 13 μm, the energy of the thermal head must be increased, so that the life of the thermal head is shortened and the printing time is prolonged.

Further, the biaxially stretched polyester film according to the present invention is required to have specific longitudinal and transverse temperature dimensional change characteristics, particularly, vertical dimensional temperature change characteristics.
That is, there is a point where the gradient of the temperature dimension change curve in the longitudinal direction of the biaxially stretched polyester film changes from negative to positive, and the temperature at this point (Tinf) is 220 ° C. or more (preferably 225 ° C. or more). It is necessary that the dimensional change rate relative to the original length of the film at this point is -5% to + 1% (preferably -4.5% to -1%).

If Tinf is less than 220 ° C. or the dimensional change rate is smaller than the above range, that is, if the shrinkage rate is large, the ribbon undergoes thermal deformation at the time of printing, resulting in an eye-shaped defect on the printed matter or transfer of wrinkles. Or the distance between the thermal head and the ribbon changes, and the gradation expression in printing becomes insufficient.

Conversely, if the dimensional change rate is large, that is, if the film is easily stretched, the ribbon will be stretched at the time of printing, and similarly, the ribbon will be wrinkled, the wrinkles will be transferred to the printed matter, and the winding of the ribbon after printing will be poor. Therefore, the tension fluctuates and causes new wrinkles.

In the transverse direction, the rate of change of the temperature dimension in the transverse direction of the biaxially stretched polyester film is -3 to + 3% (preferably, at the point (Tinf) where the gradient of the temperature dimension change curve changes from negative to positive. , -1 to + 3%). By controlling within this range, substantially the same operation and effect as in the vertical direction can be obtained.

In the present invention, after defining the temperature dimensional change characteristics in the longitudinal direction of the biaxially stretched polyester film as described above, the back coat layer is formed in an amount of 0.001 to 0.
It is provided as an ultra-thin layer at a rate of 01 g / m ² . Desirably, the ratio is 0.004 to 0.008 g / m ² .
If the back coat layer is thinner than 0.001 g / m ² , there is a risk of sticking to the thermal head. If the back coat layer is thicker than 0.01 g / m ² , components of the back coat layer adhere to the thermal head, which may hinder printing.

As described above, in the present invention, the thickness of the biaxially stretched polyester film is set to a specific optimum range, and the temperature dimensional change characteristics in the longitudinal direction of the biaxially stretched polyester film are specified as the optimum characteristics. By making the back coat layer a specific ultra-thin layer, there is little change due to heat from the thermal head, the back coat layer component does not adhere to the thermal head, and a thermal transfer printer ribbon capable of high quality printing is obtained. Can be

The polyester film for a thermal transfer printer ribbon according to the present invention preferably further has the following characteristics.

That is, the three-dimensional center plane average roughness SRa of the surface of the biaxially stretched polyester film on the side of the hot-melt ink layer is in the range of 15 to 35 nm, preferably 20 to 3 nm.
It is preferably in the range of 0 nm. If the surface roughness SRa is less than 15 nm, peeling failure from the ink may occur during printing, and the printing may be blurred, the ribbon may be cut, or noise due to peeling may cause printing noise. If the surface roughness SRa is larger than 35 nm, the printed screen becomes rough and the sharpness is reduced.

As described above, in order to control the roughness of the surface on the side of the heat-fusible ink layer relative to the surface on the side of the back coat layer to a specific range, or to optimize each surface, it is necessary to simply perform Although a layer film is possible, it is preferable to use a biaxially stretched polyester film having at least a two-layer structure, whereby each surface can be more easily optimized.

The back coat layer can function as a stick prevention layer for the thermal head. Since this back coat layer has a good stick preventing effect even in a thin film, an alkoxysilane hydrolyzate or a silicone polymer,
A silicone graft polymer, a melamine resin, a silicon-functional silyl isocyanate, a solvent-soluble polyimide polymer, a solvent-soluble polyparabanic acid polymer, or the like can be used. These are provided as a coating film or a dried film, and two or more of these may be used in combination.

In order to control the surface properties of the back coat layer to desired properties, a layer containing particles may be coated as the back coat layer. Also, the back coat layer is
It is also preferable to form a layer containing a wax-based composition as a main component.

As the wax composition, various commercially available waxes such as petroleum wax, vegetable wax, mineral wax, animal wax, and low molecular weight polyolefins can be used. However, in the present invention, the use of petroleum wax or vegetable wax is preferred from the viewpoint of stick resistance.

As the petroleum-based wax, use of paraffin wax, microcrystalline wax and oxidized wax is particularly preferable from the viewpoint of forming surface projections. As the vegetable wax, candelilla wax, carnauba wax, wood wax, oligury wax, sugar cane wax, rosin-modified wax, etc. can be used,
In the present invention, a composition comprising the following compounds is particularly preferred. That is, rosin or disproportionated rosin, or hydrogenated rosin α, β-substituted ethylene (α substituent: carboxyl,
β-substituent: hydrogen or methyl or carboxyl) adduct｝ · alkyl or alkenyl (each having 1 to 8 carbon atoms) poly (repeating unit: 1 to 6) It is more preferable to use a mixed system with the above oxidized wax. That is, it is preferable to form fine elongated projections by stretching in one direction after application of the composition, and dissolve, emulsify, suspend in water from the viewpoint of projection moldability, explosion-proof properties, and environmental pollution prevention. Clouded waxes are particularly preferred.

The mixing weight ratio of petroleum wax / vegetable wax is 10/90 to 90/10, preferably 20/8.
0-80 / 20, more preferably 30 / 70-70 / 3
It is preferably 0. The use of the vegetable wax in an amount of 10% by weight or more is intended to impart easy lubricity at high temperatures and release properties, and to obtain a uniform coating film having good uniform dispersibility when emulsified or suspended in water. It is preferred. The reason why the content of the petroleum wax is set to 10% by weight or more is that the lubricity due to the formation of the projections of the coating film is good and the running property at the time of high-speed printing is good.

In the present invention, when a mixture of the above-mentioned wax composition and an oily substance is further added, the printing traveling property in a high pulse width region can be particularly excellent. Here, the oily substance is a liquid or paste-like oil at normal temperature, and vegetable oil, resin, mineral oil, synthetic lubricating oil and the like can be used. Vegetable oils include linseed oil, oyster oil, saffler oil, soybean oil, cinnamon oil, sesame oil, corn oil, rapeseed oil, nuka oil, cottonseed oil, olive oil, sasanqua oil, camellia oil, castor oil, peanut oil,
Balm oil, coconut oil and the like can be used. Oils and fats include beef tallow, pork oil, sheep oil, cocoa oil, and the like, and mineral oils include machine oil, insulating oil, turbine oil, motor oil, gear oil, cutting oil, liquid paraffin, and the like. Any synthetic lubricating oil that satisfies the requirements described in the Chemical Dictionary (Kyoritsu Shuppan) can be used arbitrarily. For example, olefin polymerized oil, diester oil, polyalkylene glycol oil, silicone oil, etc. can be used. . Among these, mineral oils and synthetic lubricating oils having good running properties in a high pulse width region are preferable. Further, a mixture of these may be used.

The oily substance is used in an amount of 1 to 100 parts by weight, preferably 3 to 100 parts by weight, based on 100 parts by weight of the wax composition.
It is preferable to add 50 parts by weight. When the amount of the oily substance is less than 1 part by weight, the running property in a high pulse width region such as a sublimation type printer tends to decrease, and when the amount exceeds 100 parts by weight, the running in a low pulse width region is reversed. Properties tend to decrease. The above range is particularly preferable because sticking does not occur in a printer having a wide range of pulse widths and running properties are good.

Various additives can be used in the above composition within a range not to impair the effects of the present invention. For example, an antistatic agent, a heat-resistant agent, an antioxidant, organic and inorganic particles, a pigment, and the like can be used.

Further, various additives such as a dispersing aid, a surfactant, a preservative, and an antifoaming agent may be added to the paint for the purpose of improving dispersibility in water and improving coatability. Good.

Further, in the polyester film for a thermal transfer printer ribbon according to the present invention, good adhesion between a high-quality color ink and a polyester base film is imparted in order to obtain a smooth gradation expression. For this purpose, it is desirable to apply an easily adhesive coating to at least one surface of the biaxially stretched polyester film. For example, it is preferable to provide a coating layer selected from a group of urethane-based, polyester-based, and acrylic-based water-soluble or water-dispersible resins, and it is particularly preferable that at least two of these are applied.

Among the above, the urethane-based resin used as the coating layer can use the following polyol, polyisocyanate, chain extender, cross-linking agent, and the like as components constituting the urethane-based resin. As the polyol, for example, polyethers such as polyoxyethylene glycol, polyoxypropylene glycol, and polyoxytetramethylene glycol, polyesters such as polyethylene adipate, polyethylene-butylene adipate, and polycaprolactone, acrylic polyols, castor oil, and the like are used. be able to. As a polyisocyanate,
For example, tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and the like can be used. Examples of the chain extender or crosslinking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, 4,4′-diaminodiphenylmethane, and 4,4 ′.
-Diaminodicyclohexylmethane, water and the like can be used.

As the polyester resin used for the coating layer, the following polyvalent carboxylic acids and polyvalent hydroxy compounds can be used as the constituent components. Examples of polyvalent carboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid 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 can be used. Examples of the polyvalent hydroxy compound include ethylene glycol,
-Propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-
Pentanediol, neopentyl glycol, 1,4-
Cyclohexane dimethanol, p-xylylene glycol, bisphenol A-ethylene 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. 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 so-called acrylic graft polyester or a polyester polyurethane obtained by chain-extending a polyester polyol with an isocyanate can also be used.

Further, as the acrylic resin used for the coating layer, a resin containing alkyl acrylate or alkyl methacrylate as a main component is preferable. The component is 30 to 90 mol%, is copolymerizable and has a functional group. It is a water-soluble or water-dispersible resin containing 70 to 10 mol% of a vinyl monomer 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. Particularly preferred among these are carboxyl groups or salts 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 n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a 2-ethylhexyl group, a lauryl group, a stearyl group, and a cyclohexyl group. it can.

Next, a method for producing a polyester film according to the present invention will be described, but the present invention is not limited to such an example. The dried polymer chips are supplied to an extruder, and are heated and melted to a temperature equal to or higher than the melting point of the polymer. Next, the molten polymer is extruded from a T-die having a slit-shaped discharge port, and is tightly adhered to a cooling roll to obtain a cast film. In order to improve the adhesion between the molten sheet and the cooling roll, it is usually preferable to employ an electrostatic application adhesion method and / or a liquid surface application adhesion method. The cast film is further biaxially stretched. Preferably, it is stretched 2.3 to 7 times in the longitudinal direction (longitudinal direction) by a roll group heated to a temperature equal to or higher than the glass transition temperature of the polymer, for example, 40 to 130 ° C., and then preferably 45 to 130 times in the width direction (lateral direction).
Stretch 3 to 7 times at ° C. In addition, a method of performing unidirectional stretching in two or more stages can be used, but in such a case, it is preferable that the final stretching ratio falls within the above range. It is also preferable that the cast film is simultaneously biaxially stretched so that the area magnification becomes 6 to 30 times.

The film thus obtained is subjected to a heat treatment. If necessary, before or after the heat treatment, the film is again vertically and / or vertically heated.
Alternatively, it may be stretched in the transverse direction. Heat treatment temperature is 150 ~
The temperature is 250 ° C., preferably 200 to 235 ° C., and the heat treatment time is usually 1 second to 5 minutes. The heat shrinkage characteristics can be adjusted under these heat treatment conditions. The cooling rate of the film after the heat treatment also affects the heat shrinkage characteristics. For example, after the heat treatment, the heat shrinkage stress can be adjusted by rapidly or slowly cooling the film or providing an intermediate cooling zone. In addition, in order to impart a specific heat shrinkage property, the film may be relaxed in the longitudinal direction and / or the transverse direction during the heat treatment or in the subsequent slow cooling zone.

The film can be coated if necessary. In the case of the present invention, by providing a coating layer on the film, the adhesiveness with the ink layer can be particularly improved. As the coating solution, a solution dissolved, emulsified or suspended in water is used in terms of explosion-proof property and environmental pollution. The coating layer may be applied to a biaxially stretched film after the completion of the crystal orientation or may be applied to the film before the completion of the crystal orientation and then stretched.However, the latter method is used in order to more remarkably exert the effects of the present invention. Is particularly preferred. The method of applying is not particularly limited,
It is preferable to apply using a roll coater, a gravure coater, a reverse coater, a kiss coater, a bar coater or the like. Before application, the surface to be applied may be subjected to corona discharge treatment in air or other various atmospheres, if necessary.

In the coating layer of the present invention, as described above, an antifoaming agent, a coating crosslinker, a thickener, an organic lubricant, an inorganic particle, an antioxidant, an ultraviolet absorber, It may contain a foaming agent, a dye, a pigment, and the like.

A polyester film for a thermal transfer printer ribbon is formed by providing a back coat layer on one surface of the biaxially stretched polyester film thus manufactured and a heat-fusible ink layer on the other surface. .

[Measurement method of physical properties]
A method for measuring physical properties used for the evaluation will be described. (1) Temperature dimension curve Measured using a TMA (thermal mechanical analyzer) manufactured by PERKIN ELMER. However, the heating rate was 10 ° C./min, the length of the measurement sample was 14 mm, the width was 5 mm, and the tension was 50 mN.

(2) Three-dimensional surface center plane average roughness SRa Fine shape measuring instrument (model: ET-3) manufactured by Kosaka Laboratory Co., Ltd.
0HK), the stylus diameter was 2 μR, the cutoff was 0.25 mm, the measurement length (X direction) was 0.5 μm, the feed pitch in the Y direction was 5 μm, and the number of recording lines was 80.

(3) Back coat layer thickness: Determined by X-ray photoelectron spectroscopy. The device is ESCALABiX
L (VG in the UK), as excitation X-rays, monochromatic Al
Kα1,2 line (1486 eV), X-ray diameter 1 mm, photoelectron escape angle 90 °. As a reference material, an uncoated film having a film thickness of 4.5 μm and a coating component were used. The thickness d of the coat layer was determined from the relationship of the equation [1] assuming a two-layer model. I ₁ / I ₂ = n ₁ · (1-exp (-d / (r ₁ · sin θ))) / [n ₂ · exp (-d / (r ₂ · sin θ))] [1] , I _1: C ₁ ratio of coating ingredients in s peak I _2: C ₁ ratio of the polyester component in s peak n _1: number of carbon atoms in the coating layer density n _2: carbon in the polyester film in Atomic number density r ₁ : mean free path of C ₁ s photoelectrons in the coating layer [nm] r ₂ : mean free path of C ₁ s photoelectrons in the polyester film [nm] θ: photoemission angle. θ = 90 degrees, n ₁ = n ₂ , and r ₁ = r ₂ = 3.

The characteristics of the transfer material were evaluated by using a film as a tape slit having a width of 10 cm to form a heat-sensitive transfer ribbon and using a thermal printer.

(4) Print wrinkle The presence or absence of fusion between the heat-sensitive transfer ribbon and the heating head was judged according to the following criteria. ×: Ribbon conveyance failure is observed, and 10 or more wrinkles are generated per 20 cm of ribbon, which is a practical problem. Δ: 3 to 10 wrinkles are generated per 20 cm of ribbon, but practically possible.・ 1 to 3 wrinkles are generated per 20 cm of ribbon, good ◎ ・ ・ ・ Good without any problem

(5) Image Quality / Gradation The image was printed on a thermal printer, and the density and bleeding of the printed image were evaluated based on the following criteria. ×: There are shading in the image, and the blur is too strong to be practical. △: There is a slight difference in shading, and there is also a blur, but it is practical. ○: There is a slight blur, but the shading is ◎ Excellent without shading or bleeding

[0046]

EXAMPLE 1 0.3% by weight of calcium carbonate particles having an average particle diameter of 0.8 μm
And 0.04 of silicon dioxide particles having an average particle size of 1.5 μm.
A polyethylene terephthalate having an intrinsic viscosity of 0.65 (measured at 25 ° C. in orthochlorophenol) containing 0.6% by weight is melted using an extruder, melt-extruded from a die into a sheet, and then cooled and solidified by being brought into close contact with a rotary cooling drum. Thus, an amorphous sheet was obtained.

Using a heated roll, this amorphous sheet was stretched twice in the longitudinal direction at 120 ° C. and then 2.1 times at 115 ° C. to obtain a uniaxially stretched film. One surface of this film was subjected to corona discharge treatment in an air atmosphere, and the treated surface was coated with a water-dispersed paint having the following composition by a gravure coat method so that the applied thickness after biaxial stretching was 0.007 g / m ² . .

[Coating Composition] (a) 100 parts by weight of vegetable wax {hydrogenated rosin / αβ-substituted ethylene (α-substituent: carboxyl, β-substituent: methyl) impossible} alkyl (carbon number: 6) poly ( Repeating unit: 5) Ester compound of alcohol A nonionic surfactant, a phosphoric acid ester (butoxyethylated), ammonium oleate, and 2-amino-2-methylpropanol are used to make the above (a) into an aqueous dispersion. 1 part by weight of each was added, the mixture was vigorously stirred in water, and an aqueous dispersion having a total solid content ratio of 0.4% by weight was prepared using an ultrasonic disperser.

After drying the uniaxially stretched film coated with the water-dispersed coating material at 110 ° C. in a stenter,
The film was stretched 4 times in the transverse direction at 115 ° C., and then heat-set at 232 ° C., and relaxed 5% in the width direction to obtain a biaxially stretched film having a thickness of 4.5 μm.

Example 2 The same amount of vegetable wax as 100 in the paint composition of Example 1
One part by weight of an oxidized wax and 1 part by weight of spherical silica particles having an average particle diameter of 0.2 μm were added to prepare a coating material having a total solid content ratio of 0.4% by weight. Example 1 using this paint
In the same manner as in the above, a biaxially stretched film having a thickness of 4.5 μm was obtained.

Comparative Example 1 A biaxially stretched film was obtained in the same manner as in Example 1 except that the same coating material as in Example 1 was used as an aqueous dispersion having a total solid content ratio of 1.5% by weight. The coating thickness was 0.029 g / m ² .

Comparative Example 2 0.3% by weight of silicon dioxide particles having an average particle size of 1.4 μm
Intrinsic viscosity (25% in orthochlorophenol)
Melt 0.65 polyethylene terephthalate using an extruder, melt extruded from a die into a sheet,
It was cooled and solidified by being in close contact with a rotating cooling drum to obtain an amorphous sheet.

Using a heated roll, the amorphous sheet was stretched twice at 120 ° C. in the longitudinal direction and then 2.1 times at 115 ° C. to obtain a uniaxially stretched film. One side of this film is subjected to a corona discharge treatment in an air atmosphere, and the treated surface is coated with the same water-dispersed paint as in Example 1 by gravure coating so that the applied thickness after biaxial stretching is 0.007 g / m ^2. Was applied. After drying the applied uniaxially stretched film at 110 ° C. in a stenter, the film is stretched 4 times at 115 ° C. in the transverse direction, and then heat-fixed at 232 ° C., and relaxed 5% in the width direction. A biaxially stretched film having a thickness of 4.5 μm was obtained.

Comparative Example 3 0.3% by weight of calcium carbonate particles having an average particle size of 0.8 μm and 0.1% of silicon dioxide particles having an average particle size of 1.5 μm were added.
A polyethylene terephthalate having an intrinsic viscosity of 0.65 (measured in orthochlorophenol at 25 ° C.) containing 0.6% by weight is melted by using an extruder, melt-extruded from a die into a sheet, and brought into close contact with a rotary cooling drum and cooled. Solidification yielded an amorphous sheet.

Using a heated roll, this amorphous sheet was stretched twice at 120 ° C. in the longitudinal direction and then 2.1 times at 115 ° C. to obtain a uniaxially stretched film. One side of this film is subjected to a corona discharge treatment in an air atmosphere, and the treated surface is coated with the same water-dispersed paint as in Example 1 by gravure coating so that the applied thickness after biaxial stretching is 0.007 g / m ^2. Was applied. After drying the applied uniaxially stretched film at 110 ° C. in a stenter, the film is stretched 4.3 times at 115 ° C. in the transverse direction, and then heat-set at 220 ° C., and then 3.5 times in the width direction. % To give a biaxially stretched film having a thickness of 4.5 μm.

Example 3 The same polymer as in Example 1 was used. The amorphous sheet was subjected to corona discharge treatment, and then applied using the same paint as in Example 1, and then a simultaneous biaxial stretching apparatus was used. , 110 ° C
After drying the water at 4.5 ° C in the longitudinal direction at 120 ° C,
Simultaneous biaxial stretching 4.5 times in the horizontal direction, heat-setting at 230 ° C, then relax 3.5% in the width direction and 3% in the vertical direction, then 4.5μm thick biaxial stretching I got a film. The coating thickness was 0.003 g / m ² .

The surface of the obtained film (the surface not coated with an easy adhesive) was coated with a coating liquid in which an acrylic silicone coat and a silicone oil were mixed at a ratio of 80/20, and on the other side, carnauba wax was applied. : 30% by weight Ester wax: 35% by weight Carbon black: 12% by weight Polytetrahydrofuran: 10% by weight Silicone oil: 3% by weight A transfer ink layer consisting of 3% by weight is applied to a thickness of 5 µm by a hot melt coating method using a heating roll. Then, a transfer material was obtained.

Tables 1 and 2 show the characteristics of the film and the transfer material in each of the examples and comparative examples. In Comparative Example 1, as compared with each Example, the back coat layer component adhered to the thermal head, and the image quality deteriorated. In Comparative Example 2, roughness was observed on the entire printed image. In Comparative Example 3, print wrinkles occurred on the ribbon, and transfer of wrinkles was also observed on the printed surface.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

As described above, according to the polyester film for a thermal transfer printer ribbon of the present invention, the thickness of the biaxially stretched polyester film, which is the base of the transfer material, is specified within a specific range, and particularly in the longitudinal direction. Since the temperature dimensional change characteristics are specified in a specific range and the back coat layer is a specific ultrathin layer, excellent image quality can be secured.

Claims (7)

[Claims] 1. A heat-sensitive transfer film comprising a biaxially stretched polyester film having a thickness of 1.5 to 13 μm and a back coat layer provided on one surface and a heat-meltable ink layer provided on the other surface. There is a point where the gradient of the vertical temperature dimension change curve changes from negative to positive, the temperature at this point (Tinf) is 220 ° C. or more, and the dimensional change rate with respect to the original length of the film at this point is -5% to + 1%, and the back coat layer is 0.001 to 0.01 g.
/ M ^2, a polyester film for a thermal transfer printer ribbon, characterized by being provided at a ratio of / m ² . 2. The transverse dimensional change rate of the biaxially stretched polyester film is −3 to + 3% at a point (Tinf) where the gradient of the temperature dimensional change curve changes from negative to positive. The polyester film for a thermal transfer printer ribbon described in the above. 3. The three-dimensional center plane average roughness SRa of the surface of the biaxially stretched polyester film on the side of the hot-melt ink layer.
3. The polyester film for a thermal transfer printer ribbon according to claim 1, wherein n is in the range of 15 to 35 nm. 4. The polyester film for a thermal transfer printer ribbon according to claim 1, wherein the biaxially stretched polyester film has at least a two-layer structure. 5. The polyester film for a thermal transfer printer ribbon according to claim 1, wherein a layer containing particles is coated as a back coat layer. 6. The polyester film for a thermal transfer printer ribbon according to claim 1, wherein the back coat layer is mainly composed of a wax-based composition. 7. The biaxially stretched polyester film is manufactured by simultaneous biaxial stretching.
7. The polyester film for a thermal transfer printer ribbon according to any one of 6.