KR20040034917A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE: Provided is a biaxially oriented polyester film, which has excellent magnetic tolerance suitable for a heat-sensitive transfer ribbon film and good processing capability free from wrinkling and coating defects. CONSTITUTION: The biaxially oriented polyester film comprises a polyester composition containing 0.01-1.0 wt% of plate-like particles, wherein the plate-like particles have an average thickness of 0.1-1.0 micrometers, a center line roughness(SRa) of 20-35 nm, a ten-point average roughness of 0.6-1.5 micrometers, and a thickness variation in the machine direction of 15% or less. Alternatively, the biaxially oriented polyester film comprises 0.01-3.0 wt% of at least one type of mono-disperse particles having an average particle diameter of 0.05-1.0 micrometers, instead of the plate-like particles.

Description

Biaxially Oriented Polyester Film {BIAXIALLY ORIENTED POLYESTER FILM}

The present invention relates to a biaxially oriented polyester film, in particular, very excellent in printability and flammability characteristics, and furthermore, in the biaxially oriented polyester film having excellent workability due to no defects such as wrinkles and coating defects when processing with a ribbon. It is about.

Since biaxially oriented polyester films are excellent in mechanical properties, electrical properties, dimensional stability, transparency, heat resistance, and the like, they are widely used as base films in many applications such as magnetic recording materials, electrical insulating materials, various photographic materials, and graphic arts. In particular, in recent years, as a base film for thermal transfer ribbons such as office automation, factory automation, etc., its use is expanding rapidly.

The thermal transfer ribbon is a melting type in which various pigments are added to a binder such as wax, and the ink layer is melted by heat to be transferred to the transferee, and a sublimation dye in the binder is added to contact the transferee by heat. There is a sublimation type in which only the dye is transferred to the aqueous layer of the transfer object in the state.

In recent years, the increased demand for thermal transfer ribbons for barcodes due to increased volume of shipments, the increased demand for high-factor / highly flammable thermal transfer ribbons due to the expansion of digital cameras, etc. The demand for thermal transfer ribbons and thermal transfer ribbon films is on the rise due to the generation of new demands for thermal transfer ribbons and the steady demand for thermal transfer ribbons for special small printing such as receipts.

In addition, in order to realize cost reduction, thermal transfer ribbon processors reduce the thickness of the heat-resistant coating layer or the ink layer, and thus the surface structure of the thermal transfer ribbon film has a great influence on the surface structure of the coating layer. Technology for controlling the surface structure of ribbon films has become more important.

As the film constituting the thermal transfer ribbon, a polyester film that can be thinned industrially and has excellent mechanical properties and the like has been used. Polyester films used for thermal transfer ribbons have mechanical properties (US Pat. Nos. 6197430, 4675233 and 6306496), thermal properties (Japanese Patent Laid-Open Nos. 10-264337 and 11-321127), surface roughness characteristics (Japanese Patent Laid-Open No. 10-86543 and Japanese Patent Laid-Open No. 2000-108374) and the like are known. These films improve the slip resistance or heat resistance at the time of printing.

However, the thermal transfer ribbon made of the conventional film has the following problems.

First, ribbon shaving occurs on the guide roll or the thermal head of the driving system due to the increase in the transmission speed and the printing energy in the traveling system inside the transfer printer, and foreign matters generated by the cutting are deposited on the thermal head and printed. The quality is degraded.

Second, in the case of a ribbon whose surface is proposed to solve the above problem, the surface roughness of the film is excessively flat, so that the processing suitability decreases and wrinkles or poor coating occur in the transfer ink coating process of the ribbon manufacturing process. There is a problem.

Recently, in the use of automotive labels or thermal transfer ribbons for electronic resident ID printing, it is required to have more sharp printing quality and less cutting in the traveling system inside the thermal printer as the printing speed increases. It has come to the stage of satisfying the mutually opposing characteristics such as this should be good, and therefore it is necessary to solve this problem urgently.

The present invention has been made in consideration of the above-mentioned conventional problems, and when used for thermal transfer, the printing properties are very excellent, and there are no defects such as wrinkles or poor coating in the process of producing thermal transfer ribbon films or processing processes. It is an object of the present invention to provide a good biaxially oriented polyester film.

In order to achieve the above object, the present invention is a biaxially oriented polyester film composed of a polyester composition containing 0.01 to 1.0% by weight of the plate-shaped particles: the average thickness of the plate-shaped particles is 0.1 to 1.0㎛, centerline roughness ( SRa) is 20-35 nm, 10-point average roughness SRz is 0.6-1.5 micrometers, and it is characterized by the fluctuation rate of 15% or less after a longitudinal direction. This biaxially oriented polyester film has excellent processability, and the printing quality is very good when the thermal transfer ribbon is made.

The polyester composition in this invention is used by the meaning containing what blended not only a polyester resin single body but another kind of polymer. The blended polyester composition preferably contains at least 50% by weight of polyester resin.

The polyester resin used for this invention is a polymer containing the ester group obtained by condensation polymerization of dicarboxylic acid and diol. As dicarboxylic acid, for example, terephthalic acid, isophthalic acid, adipic acid, sebacic acid, 2.6-naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, bis- (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid Aliphatic and aromatic dicarboxylic acids, such as these, can be used. As the diol, for example, ethylene glycol, 1,4-butanediol, diethylene glycol, polyethylene glycol, neopentyl glycol, cyclohexanemethanol and the like can be used. Two or more types may be used for the said dicarboxylic acid and diol, respectively. As for the intrinsic viscosity of such polyester, the value measured in 25 degreeC orthochlor phenol is preferable 0.4-2, More preferably, it is 0.5-1.

In the polyester resin used for this invention, if it is less than 10 mol% other than the said dicarboxylic acid and diol, another monomer and polymer may be copolymerized. Moreover, two or more types of polyester resins may be melt-mixed. Moreover, you may contain additives, such as another kind of polymer, a ultraviolet absorber, a lubricating agent, a pigment, antioxidant, a heat stabilizer, a flame retardant, an antistatic agent, in the range which does not impair the objective of this invention.

On the other hand, particularly preferred polyester resins used in the present invention are polyethylene terephthalate, polyethylene-2,6-naphthalate, and polyethylene- (2, chlorophenoxy) ethane-4,4'-dicarboxylate.

In this invention, a film is shape | molded using polyester resin as above. Next, the film of this invention needs to be extended | stretched at least biaxially or more. That is, the thickness of the film according to the present invention is not particularly limited, but is usually in the range of 2.0 to 8.0 mu m, preferably 2.5 to 7.0 mu m, more preferably 3.0 to 6.0 mu m for the thermal transfer ribbon. If the thickness exceeds 8.0 μm, it takes time for heat conduction and is not suitable for high speed factor. On the contrary, when it is less than 2.0 µm, the strength is lowered, resulting in poor workability, and the strength characteristics as a ribbon are insufficient, which is not preferable.

The biaxially-oriented polyester film of this invention needs to contain the plate-shaped particle whose average thickness is 0.1-1.0 micrometer. By containing the plate-shaped particles having an average thickness of 0.1 to 1.0 mu m, preferably 0.2 to 0.8 mu m, it is possible to satisfy the aptitude during processing and the wear resistance in the running system. If the average thickness is less than 0.1 μm, agglomeration between particles is aggravated and dispersibility is deteriorated. As a result, the number of coarse particles increases, so that many fractures occur during film production, or after thermal transfer ribbon is manufactured. Coarse particles are scraped out from the running system of the thermal thermal printer, and the printing condition is poor, and the surface roughness is not enough, so that wrinkles or poor coating occur when processing the thermal transfer ribbon. In addition, when the average thickness exceeds 1.0 µm, the inherent characteristics of the plate-like feature decreases, and the property of the plate-shaped particles being oriented in the stretching direction of the film during stretching decreases, and thus the surface roughness of the film is greatly increased. Increasing the surface roughness decreases the contact area with the thermal head, which is not preferable because of the problem that the sharp printing becomes difficult. The particle size in the direction perpendicular to the thickness direction of the plate-shaped particles is preferably 2.0 to 5.0 µm, more preferably 2.5 to 4.0 µm. If the particle size is smaller than the above range, the surface roughness of the film is too low, and thus the aptitude at the time of processing with the thermal transfer ribbon decreases, which is undesirable. If the particle size is larger than the above range, the surface roughness is too high, and the number of coarse particles is increased, resulting in thermal transfer. The chipping in the traveling system inside the printer is increased, and the fracture is increased in the stretching process during film production. Moreover, the addition amount of plate-shaped particle | grains is 0.01-1.0 weight%, More preferably, it is 0.05-0.8 weight%. If the content is less than the above range, the winding property at the time of film production is lowered, and the aptitude at the time of processing with the thermal transfer ribbon is poor, which is not preferable. If the content is more than the above range, the wear resistance inside the traveling system is lowered. As the kind of plate-shaped particles, for example, mica particles, titanium coated mica particles, kaolin particles and the like are preferable.

It is preferable that the biaxially-oriented polyester film of this invention contains at least 1 type or more non-plate-shaped monodisperse particle other than the said plate-shaped particle | grains. Although it does not specifically limit as monodisperse particle, For example, calcium carbonate particle, organic particle, colloidal silica particle, titanium oxide particle, alumina particle is preferable, Especially at least selected from organic particle, calcium carbonate particle, colloidal silica particle, alumina particle One or more kinds of particles are preferable.

The crystal form of the calcium carbonate particles is not particularly limited, but a calcitic type, a vaterite type, and the like may be applied. The organic particles are also not particularly limited, but divinylbenzene particles and silicon particles are preferable. Divinylbenzene particle means that it mainly uses divinylbenzene as a crosslinking component. Divinylbenzene is preferably 51% or more, preferably 60% or more, more preferably 75% or more of the particle component. The degree of crosslinking here is the weight percent of the crosslinkable component in the organic particle composition. In addition, a silicon particle has organopolysiloxane (CH3-SiO3 / 2) as a main component.

Although the particle diameter of the above-mentioned monodisperse particle is not specifically limited, Average particle diameter is 0.05-1.0 micrometer, Preferably it is 0.08-0.8 micrometer. The average particle diameter of monodisperse particle | grains is 0.05-1.0 micrometer, Preferably it is 0.08-0.8 micrometer. If the average particle diameter of the mono-dispersed particles is less than 0.05 µm, the ability to form protrusions is insufficient, and the wear resistance decreases due to an increase in the contact area with the guide rolls in the traveling system inside the thermal transfer printer. When the average particle diameter of a dispersed particle exceeds 1.0 micrometer, the number of coarse particles will increase and conversely, abrasion resistance falls and it is unpreferable. Moreover, as for content of monodisperse particle | grains, 0.01 to 3.0 weight% is preferable, More preferably, when it is 0.05 to 2.0 weight%, it becomes excellent in abrasion resistance. If the content of the monodisperse particles is less than 0.01% by weight, it is not preferable because the effect of improving the wear resistance by the monodisperse particles is not sufficiently expressed. On the contrary, if the content of the monodisperse particles exceeds 3.0% by weight, the effect of increasing the wear resistance exceeds the saturation point, which is uneconomical. Not desirable

The biaxially oriented polyester film according to the present invention may contain agglomerated particles in addition to the plate-shaped particles and monodisperse particles described above in terms of printability, wear resistance, aptitude during thermal transfer ribbon processing, and the like. The aggregated particles are not particularly limited, but alumina, zirconia, silica, etc., in which the crystalline form is a mold, a mold, a mold, or a mold, are preferable. Furthermore, a plurality of such particles may be used in combination. In terms of wear resistance, the primary particle diameter of the aggregated particles is not particularly limited, but is 5 to 100 nm, preferably 10 to 80 nm, and the aggregated secondary particle diameter is not particularly limited, but is 0.1 to 4.0 nm, preferably 0.3 to 3.0 nm. Although content is not specifically limited, 0.005 to 2.0 weight%, Preferably it is 0.01 to 1.5 weight%.

Biaxially oriented polyester film according to the present invention is a film for biaxially oriented composition. As a uniaxial or non-oriented film, since abrasion resistance becomes poor, it is not preferable. The degree of such orientation is not particularly limited, but biaxial orientation is preferable because the wear resistance is better when the elastic modulus, which is a measure of molecular orientation of the polymer, is 350 kgf / mm 2 or more in both the longitudinal and the width directions. As for the elasticity modulus which is a measure of molecular orientation, about 1,500 kgf / mm <2> is a manufacturing limit normally.

According to the biaxially oriented polyester film according to the present invention, even if the modulus of elasticity is within the above range, a part of the thickness direction of the film, for example, the orientation of the polymer molecules near the surface layer is not oriented or unidirectional, that is, the whole part in the thickness direction. When the molecular orientation of is biaxially oriented, wear resistance is further improved.

In the biaxially oriented polyester film of the present invention, the surface centerline roughness SRa is 20 to 30 nm, and the ten-point average roughness SRz needs to be in the range of 0.6 to 1.5 µm. If the center line roughness SRa is 20 nm or less, or the 10-point average roughness SRz is less than 0.6 µm, it is not preferable because the sticking phenomenon of fusion to the thermal head during printing occurs, resulting in a problem of uneven printing. In addition, when the center line roughness SRa exceeds 30 nm or the 10-point average roughness SRz exceeds 1.5 μm, the number of coarse particles increases, leading to poor wear resistance in the traveling system inside the thermal printer, and poor thermal conductivity from the thermal head. Is not desirable because it becomes unclear.

In order to make center line roughness SRa and 10-point average roughness SRz into the said range, it can achieve by adjusting the average thickness, average particle diameter, and addition amount of the inert particle added to a polyester resin.

In the biaxially oriented polyester film according to the present invention, the thickness variation in the longitudinal direction needs to be 15% or less, more preferably 10% or less. If the thickness variation exceeds 15%, it is not preferable because wrinkles or coating defects are likely to occur when processing the thermal transfer ribbon. In order to make the thickness variation rate of a longitudinal direction into the said range, it can achieve by adjusting shaping | molding conditions at the time of manufacturing an unstretched film, extending | stretching temperature in a longitudinal stretch process, and a draw ratio. Among them, molding conditions are particularly important when producing an unstretched film, and it is important to set the distance between the polymer sheet discharged from the die on the slit and the wire electrode applying voltage to an appropriate range. That is, when the distance is too long with respect to the distance between the wire electrode and the cooling drum surface, the potential gradient formed between the wire electrode and the cooling drum is lowered, so that sufficient charge is not emitted from the wire electrode, so that the electrostatic force applied to the polymer sheet is reduced. As a result, sufficient adhesion cannot be obtained on the cooling drum, which increases the rate of change even afterwards. On the contrary, if the distance is too short, the potential gradient becomes excessive, which leads to insulation breakdown of the polymer sheet, resulting in a problem of discharge. In addition, with respect to the position in the direction in which the polymer sheet of the wire electrode is drawn, if the wire electrode is provided upstream than the point where the molten polymer sheet discharged from the die lands on the cooling drum surface, it acts between the polymer sheet and the wire electrode. The coulomb repulsion and the vibration of the peripheral device are combined to cause a problem that the polymer sheet is shaken. On the contrary, if it is provided downstream from the landing point, the cooling drum side surface of the polymer sheet is already cooled to some extent, and the polymer sheet is not sufficiently adhered to the cooling drum.

Next, the manufacturing method of the biaxially-oriented polyester film which concerns on this invention comprised as mentioned above is demonstrated.

First, as a method of containing particles in polyester, it may be added at any stage of the polyester manufacturing process or molding process, but a relatively low molecular weight intermediate may be used to obtain a polymer polymer having a film forming ability in a reduced pressure or inert air stream. It is preferable from the point of dispersibility with respect to the polyester resin obtained and the prevention of the coloring of a polymer that it adds immediately before or an initial stage. The addition is preferably carried out as a slurry in ethylene glycol of the diol component, and the ethylene glycol is preferably polymerized with a predetermined dicarboxylic acid component. Of course, the water slurry of the particles is directly mixed with a predetermined polyester pellet and kneaded in a polyester using a twin-screw kneading extruder in the form of a vent to prepare a master batch, and diluted with other polyester to reduce the content of the film. It may be adjusted.

Subsequently, the pellet containing a predetermined amount of particles is dried as needed, and then extruded into a sheet form from a known slit-like die to be solidified on a casting roll to produce an unstretched film.

Subsequently, the non-oriented film is biaxially stretched in the longitudinal direction and the transverse direction to be biaxially oriented. As the stretching method, it is possible to use a sequential biaxial stretching method or a simultaneous biaxial stretching method. However, the longitudinal stretching is divided into three or more stages using the sequential biaxial stretching method in which the stretching in the width direction is performed after the first longitudinal direction, and the longitudinal stretching temperature is 80 to 150 ° C, the total longitudinal stretching ratio is 3.0 to 6.5 times, and the longitudinal stretching speed The range of 5,000-50,000% / min is preferable. As the stretching method in the width direction, a method using a stenter is preferable, the stretching temperature is 80 to 160 ° C, the stretching ratio in the width direction is 3.5 to 6.0 times, and the stretching speed in the width direction is preferably in the range of 1,000 to 20,000% / min. Do.

Subsequently, the stretched film is heat treated. In this case, the heat treatment temperature is 190 to 250 ° C, particularly 200 to 240 ° C, and the time is preferably in the range of 0.5 to 30 seconds.

In the case of the relaxation treatment, the treatment is performed from the heat treatment zone until it is wound on the roll. As a lateral relaxation treatment method, the width of the stenter is reduced between the heat treatment zone and the cooling zone in the horizontal direction, and 0 to 10 in the width direction of the film. Preference is given to a method of relaxation of%. In addition, as a longitudinal relaxation method, the both ends of a film are cut out and the taking-out speed is lower than the feed rate of a film under temperature conditions more than Tg of a film and below a melting temperature. Infrared heater between two conveying rolls with different speeds. Furnace, or a roll speed after the heating zone is lower than a roll speed before the heating zone while passing through a heating zone by a heating oven or an infrared heater, and any of these methods may be used. The reduction ratio of the take-out speed is 0 to 5% of the speed, and the relaxation process is performed.

In addition, the polyester composition which comprises the biaxially-oriented polyester film of this invention may contain some recycled and recovered composition, and may contain all. The recycled recovered composition refers to a polyester composition composed of trimming parts, quality non-conforming products or waste products generated in the manufacturing process of the film.

In particular, when the biaxially oriented polyester film according to the present invention is used as a film for thermal transfer ribbon, a transfer ink layer of a molten or sublimation type is coated on one side of the biaxially oriented polyester film made of a polyester composition. Such a transfer ink layer can be provided with a transfer ink layer on a biaxially oriented polyester film by applying or hot-melting a well-known composition mainly composed of a pigment or dye colorant and a binder made of a polymer compound. have.

The thickness of the transfer ink layer is not particularly limited, but is preferably 2 μm or less. If it exceeds 2 μm, a problem of lack of adaptability may occur. By setting the thickness of the transfer ink layer to 2 µm or less, for example, four or more sets of modified expressions can be easily performed. In addition, a heat resistant layer is applied to the opposite side of the transfer ink layer. This heat resistant layer is provided for the purpose of preventing the sticking phenomenon by heat when it contacts with a heat sensitive head, The well-known well-known thing can be used here. As typical heat-resistant coating layers, various waxes, cellulose resins, modified acrylic resins such as acrylic silicone, butyral resins, silicone resins, amide resins, silicone oils, various minerals, phosphoric acid compounds and the like can be used. In addition, various organic particles and inorganic particles may be added to the heat-resistant coating layer. Although the thickness of this heat-resistant coating layer is not specifically limited, It is preferable that it is 0.01-1.0 micrometer from the point of contamination of a thermal head and heat resistance, More preferably, it is the range of 0.02-0.3 micrometer. In addition, the method of applying the heat-resistant coating layer is not particularly limited, but may be dried or stretched after a predetermined coating is applied to a uniaxial stretched or unstretched film, stretched biaxially or more, and then to a film subjected to necessary heat treatment. It may be applied and dried. Representative coating methods include gravure method, reverse method, metering bar method, die coating method, cap coating method and the like.

<Example>

The present invention will be described in more detail with reference to the following Examples.

In the present invention, the characteristic values were defined as the following measurement methods and evaluation criteria.

1. Average particle diameter of monodisperse particles and aggregated particles

The sample film is subjected to a plasma low temperature ignition treatment at 0.25 kV and 1.25 mA under a 1 x 10-3 torr vacuum using a sputtering apparatus to remove the resin from the surface of the sample film to expose the particles. In addition, gold sputtering was performed with the same apparatus.

The treated sample film was photographed by observing at 5,000 times magnification using an electron microscope. Measure more than 500 views while moving the location. The primary particle diameter of agglomerated particles is the particle size unit of which the agglomerated particles cannot be divided, and the agglomerated secondary particles are the average particle diameters measured using an image analyzer to measure the diameter corresponding to the original area of each particle. Was taken as the average particle diameter.

2. Thickness and Size of Plate Particles

The average particle diameter of the monodispersed particles was measured, and since the size of the plate-shaped particles was anisotropic, the size and thickness of the particles were obtained by observing the film in the plane direction and the direction perpendicular to the film plane, respectively.

3. Surface Roughness SRa, SRz

It measured according to DIN-4768. Using a 5 micrometer R needle, it measured by measuring length 2.5mm, the number of scanning scans, and cutoff value 0.25mm. Four repeated measurements of the same sample were made as the average of the remaining three data except for the largest one.

4. Post-change rate

The film thus prepared was sampled at a width of 5 cm in the longitudinal direction, set in a film traveling device, and then continuously run over 5 m, and the film thickness was measured using an Anritsu film thickness gauge KG601A, and the value was continuously recorded. From the recording chart, (maximum thickness-minimum thickness) / average thickness x 100 (%) is expressed as the rate of change in the longitudinal back direction.

5. Factor

Using a high-precision printer manufactured by Seiko Electronics Co., Ltd. as a thermal transfer printer, the sharpness of the print was observed by visual observation and 100 times with a stereomicroscope. As shown in Table 1, the case where the printed characters had no defects such as scratching, sagging and deformation, and there were no unnecessary factors in the parts other than the printing was defined as?.

6. Aptitude during thermal ribbon processing

After applying the following coating liquid as a heat-resistant layer on one side of the biaxially oriented polyester film using a metering bar method so that the coating thickness after drying was 0.2 μm, under the conditions of a film tension of 20 MPa, a heating temperature of 130 ° C., and a heating time of 15 seconds. The solvent was dried and crosslinked.

(Composition of Heat Resistant Layer)

Polyacrylic acid ester: 13.4 wt%

Amino modified silicone: 6.5 wt%

Isocyanate: 0.1 wt%

Toluene: 35.0 wt%

Methyl ethyl ketone: 45.0 wt%

Subsequently, the transfer ink of the following composition was applied to the opposite side of the heat resistant layer using a gravure coater so that the coating thickness was 1.5 μm, and then the tension applied to the film was 20 MPa, the heating temperature was 110 ° C., and the heating time was 12 seconds. Drying was performed.

(Composition of Transfer Ink)

Ethylene Vinyl Acetate Copolymer: 28% by weight

Water based rosin wax: 7% by weight

Carbon black: 15 wt%

Toluene: 47 wt%

Ethylene Glycol Monomethyl Ether: 3 wt%

In processing the thermal transfer ribbon, whether or not normal processing is possible was observed in the process, or the processed thermal transfer ribbon was visually examined and classified as follows.

(Double-circle): No wrinkles generate | occur | produce in a process and coating defect does not arise either.

(Triangle | delta): Fine wrinkles generate | occur | produce in a process, but it does not lead to a coating defect.

X: Wrinkles generate | occur | produce severely in a process, and coating defect also arises.

7. Wear resistance of film

Fixed guide pin (surface roughness) made of stainless steel using a tape running tester (TBT300D / H manufactured by Yokohama Systems) under a temperature of 20 ° C and a relative humidity of 60%. Ra: 0.1 m) Run and rub the stomach (driving speed 50mpm, guide pin contact angle 50 °, unwinding tension 50g).

After passing the film ten times, the state of the wear powder attached to the fixed guide pin was evaluated based on the following criteria.

(Double-circle): No abrasion powder is seen at all.

(Triangle | delta): When the area of abrasion adhered is less than 1/10 of the apparent contact area of a pin and a film.

X: the area of abrasion adhered is 1/10 or more of the apparent contact area between the pin and the film

? Is preferable, but? Can be used practically.

<Example 1>

(1) Preparation of Polyester Resin Composition

10% by weight of mica particles having an average particle diameter of 3.1 mu m and an average thickness of 0.4 mu m and 90% by weight of ethylene glycol were mixed and stirred at high temperature for 3 hours at room temperature to obtain a mica particle / ethylene glycol slurry (a).

Meanwhile, after adding 0.06% by weight of magnesium acetate as a catalyst to 100% by weight of dimethyl terephthalate and 64% by weight of ethylene glycol, and performing a transesterification reaction while gradually warming the temperature from 150 ° C to 240 ° C, the slurry prepared before the reaction product (a ) Was added to the addition amount shown in Table 2, and then 0.03% by weight of antimony trioxide as a polycondensation catalyst and 0.04% by weight of trimethyl phosphate were added, and a polycondensation reaction was carried out to obtain a polyethylene terephthalate composition having an intrinsic viscosity of 0.620.

(2) Preparation of Biaxially Oriented Polyester Film

The obtained polyester resin was vacuum-dried at 160 degreeC and 3 torr for 5 hours. The polymer was fed to an extruder, melted and extruded at 285 ° C. to form a sheet from a slit die onto a cooling drum whose surface temperature was controlled at 28 ° C. At this time, the gap between the die and the cooling drum is set to 27 mm while the sheet is brought into close contact with the surface of the cooling drum by the electrostatic application method. The vertical distance between the cooling drum and the wire electrode is 4 mm and the horizontal distance between the wire electrodes from the die vertical direction is 52 mm. The applied DC voltage was 8.5 kV and cooled and solidified at a rate of 45 m / min to obtain an unstretched sheet. The unstretched sheet was stretched 1.7 times at 121 ° C., 1.4 times at 120 ° C. and 2.1 times at 115 ° C. in the longitudinal direction, and the resulting uniaxially stretched film was sent to the stent, and stretched in the transverse direction at 125 ° C. and 3.9 times. Heat treatment was performed at 230 ° C. and 3.8% relaxation treatment was performed in the transverse direction. As a result, a biaxially oriented polyester film having a thickness of 4.6 µm was obtained.

About the obtained biaxially-oriented polyester film, surface roughness (center line roughness (SRa), 10-point average roughness (SRz)), the back-varying variation, and abrasion resistance were evaluated, and the result is shown in Table 2.

Subsequently, a heat-resistant agent layer and a transfer ink layer were applied to one side and the opposite side of the obtained biaxially oriented polyester film as described above to prepare a thermal transfer ribbon, and then the printability and aptitude during processing of the thermal transfer ribbon were evaluated. The results are shown in Table 2.

<Examples 2-7>

In the same manner as in Example 1, the biaxially oriented polyester film and the thermal transfer ribbon using the same were prepared by changing the type, particle diameter, thickness, and amount of the plate-shaped particles, mono-dispersed particles, and aggregated particles under the conditions shown in Table 2. It is shown in Table 2 to evaluate.

<Comparative Examples 1-4>

As in Example 1, the biaxially oriented polyester film and the thermal transfer ribbon using the same were manufactured by changing the type, particle diameter, thickness, and amount of the plate-shaped particles, mono-dispersed particles, and aggregated particles under the conditions shown in Table 3. It is shown in Table 3 to evaluate.

Comparative Example 5

In the same manner as in Example 2, the conditions were changed under the conditions shown in Table 3, and the distance between the die and the cooling drum was 18 mm, and the distance between the wire electrodes was 42 mm from the straight line parallel to the die discharge part, thereby bringing the polymer closer to the discharged polymer. A biaxially oriented polyester film and a thermal transfer ribbon using the same were prepared, and their performances were evaluated and shown in Table 3 below.

As can be seen in Table 2 and Table 3, the film of the embodiments falling within the scope of the present invention has a good printability, wear resistance, aptitude during ribbon processing, the outside of this range of printability, abrasion resistance, ribbon processing It was impossible to balance aptitude. In addition, as can be seen from Table 3, in particular, in the case of Comparative Example 5, the rate of change increased even after the aptitude during ribbon processing was poor.

In the biaxially oriented polyester film according to the present invention configured as described above, by adding specific inert particles to the polyester resin composition to define the surface roughness in a specific range and at the same time define the rearward variation in the longitudinal direction in a specific range. A biaxially oriented polyester film having excellent printability and processability can be provided, thereby providing a high performance thermal transfer ribbon.

Claims (4)

In a biaxially oriented polyester film composed of a polyester composition containing 0.01 to 1.0% by weight of plate-shaped particles: The average thickness of the plate-shaped particles is 0.1-1.0 μm, the center line roughness SRa is 20-35 nm, the 10-point average roughness SRz is 0.6-1.5 μm, and the variation after the longitudinal direction is 15% or less. Biaxially oriented polyester film. It consists of polyester composition containing 0.01-3.0 weight% of 1 or more types of monodisperse particle whose average particle diameter is 0.05-1.0 micrometer, center line roughness (SRa) is 20-35 nm, and 10-point average roughness (SRz) is 0.6 It is -1.5 micrometers, and the biaxially-oriented polyester film characterized by the fluctuation rate of 15% or less after the longitudinal direction. The method according to any one of claims 1 and 2, The polyester composition is a biaxially oriented polyester film, characterized in that the composition containing some or all of the composition recovered by recycling. The method according to any one of claims 1 and 2, A biaxially oriented polyester film, wherein a transfer ink layer is laminated on one side of the film with a thickness of 2.0 μm or less.