JP2008100386A - Polyester film for sublimation type thermotransfer ribbon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for a sublimation type thermotransfer ribbon excellent in glossiness of a film surface whose strength can be enhanced and whose winding property (so called handleability) of a film can be kept. <P>SOLUTION: The polyester film for the sublimation type thermotransfer ribbon is characterized in that its film thickness is 6 μm or less, 20°glossiness (Gs20°) of the film surface is 180% or more, the strength at 5% extension (F-5) in a film longitudinal direction (MD) is 115 MPa or more, the maximum crosssection height roughness (St) of the film surface is 2,000 nm or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polyester film. Specifically, the present invention relates to a polyester film for a sublimation type thermal transfer ribbon suitable for printing at a high speed and transferring a protective layer.

  Biaxially oriented polyester film has various properties such as mechanical properties, heat resistance, electrical properties, chemical resistance, etc. in a highly balanced manner and is excellent in cost performance. It is widely used as industrial materials such as industrial use. In recent years, in particular, the demand for materials for various printing media has increased. In particular, as a film for a thin film, it is widely used as a film for a thermal transfer ribbon. In recent years, with regard to thermal transfer ribbons, various types of high strength base films have been proposed to prevent defects in the final screen due to the elongation of the ribbon, regardless of whether the type is fused or sublimated. (Patent Document 1).

  In recent years, the surface of the base surface that holds the overcoat layer before the overcoat layer is transferred in order to obtain the same glossiness as that of a conventional silver salt photograph, as represented by the use of the sublimation type thermal transfer system. It has been proposed to keep the surface smooth (Patent Document 2).

  However, according to the inventor's experience, when the stretching ratio in the machine direction (MD) is increased in the film forming process in order to increase the strength, the added particles are flattened, and the protrusion height on the final surface is increased. It will be significantly reduced. In addition, since the amount of particles is limited to achieve high gloss (smoothness), the frequency of particles is low, so that the winding characteristics of the film surface are lowered, and the yield of non-defective products is remarkably lowered.

On the other hand, it can be easily analogized to adopt a laminated structure in which the opposite surface in contact with the overcoat layer is roughened to improve the winding characteristics as a countermeasure, but there is a possibility that it is disadvantageous in terms of equipment, In addition, problems due to transfer of the surface shape may occur. Thus, it is difficult to satisfy the smoothness and high strength of the base film and the handling at the same time economically, and such a film is required.
Japanese Patent Laid-Open No. 11-263077 JP 2003-341239 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is to achieve high gloss and high strength of the surface while keeping the equipment cost low, and to maintain the winding characteristics (handling property). Another object of the present invention is to provide a polyester film for a sublimation type thermal transfer ribbon that can be used.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved at the same time by employing particles having a specific surface, and have completed the present invention.

  That is, the gist of the present invention is that the film thickness is 6 μm or less, the film surface 20 ° glossiness (Gs20 °) is 180% or more, and the film longitudinal direction (MD) 5% elongation strength (F-5). ) Is 115 MPa or more, and the maximum cross-sectional height roughness (St) of the film surface is 2000 nm or more.

The present invention will be described in detail below.
The polyester constituting the film of the present invention refers to a polyester having 80% or more of repeating units having an ethylene terephthalate unit or an ethylene-2,6-naphthalate unit. Such a polyester usually has (1) a polycondensation reaction via a transesterification reaction using a lower alkyl ester of an aromatic dicarboxylic acid and a glycol as main starting materials, or (2) an aromatic dicarboxylic acid and It can be obtained by conducting a polycondensation reaction via an esterification reaction using glycol as a main starting material. In order to perform these reactions, a method of adding a metal compound as a catalyst is usually used. For example, compounds such as Ca, Mg, Mn, and Li are generally used as transesterification reaction catalysts, and compounds such as Sb, Ti, Ge, Sn, and Co are used as polycondensation reaction catalysts.

  Further, the polyester of the present invention may contain other third component without departing from the scope of the present invention.

  As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid, etc.) ) Etc. can be used. As the glycol component, in addition to ethylene glycol, for example, one or more of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like can be used.

  The intrinsic viscosity of the polyester used in the present invention is usually 0.45 or more, preferably 0.50 to 1.0, more preferably 0.52 to 0.80. When the intrinsic viscosity is less than 0.45, there may be a problem that the productivity at the time of film production is lowered or the mechanical strength of the film is lowered. On the other hand, it is preferable that the intrinsic viscosity does not exceed 1.0 from the viewpoint of the melt extrusion stability of the polymer.

  The polyester film of the present invention has a thickness of 6 μm or less. 5 μm or less is preferable from the viewpoint of capacity as a final product, and 3 μm or more is more preferable from the viewpoint of winding yield during film production.

The polyester film of the present invention needs to have a 20 ° gloss (Gs20 °) (MD / TD average value) of 180% or more, preferably 200% or more, as measured by a method described later (20-degree mirror method). It is. In the present invention, MD means the longitudinal stretching direction (longitudinal direction) in the film forming process, and TD means the transverse stretching direction (width direction) in the film forming process. When the 20 ° glossiness is less than 180%, the glossiness of the final screen is inferior and is inappropriate.
Further, in order to maintain the winding characteristics as described later within a range satisfying the above glossiness, in order to limit the longitudinal stretching (MD) magnification, the MD glossiness (Gs20 ° (MD)) and the TD glossiness (Gs20 (TD (TD)) is preferably in a relationship of Gs20 ° (MD) ≦ Gs20 ° (TD) +5, and more preferably in a relationship of Gs20 ° (MD) ≦ Gs20 ° (TD).

  The polyester film of the present invention is required to have a 5% elongation strength (F-5) of 115 MPa or more in the film longitudinal direction (MD) in order not to cause defects on the final screen due to elongation of the ribbon, preferably 120 MPa or more. If the 5% elongation strength (F-5) in the longitudinal direction (MD) is less than 115 MPa, uneven printing tends to occur during high-speed printing, which is inappropriate.

  The polyester film of the present invention needs to have a maximum cross-sectional height roughness (St) of 2000 nm or more, preferably 2300 nm or more, for the purpose of winding properties, measured by a non-contact method as described later. When St is less than 2000 nm, the winding property is inferior and is inappropriate.

  Suitable applications of the film of the present invention include, for example, a sublimation type thermal transfer system, particularly applications that print at a high speed and require uniform and high gloss.

  Examples of particles present in the polyester to obtain the winding characteristics of the present invention include calcium carbonate, silica, talc, kaolin, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide and the like. Inorganic particles, crosslinked polymer particles, organic particles such as calcium oxalate, and precipitated particles formed at the time of polyester polymerization can be mentioned. Preferred are calcium carbonate, silica, and precipitated particles containing calcium and phosphorus.

  For calcium carbonate, the particle size distribution is sharpened, coarse particles (particles significantly larger than the average particle size) can be easily cut, slipperiness and wear resistance are easily obtained after film formation, and a film that does not become a product is unnecessary. The reason is that, when the part is remelted and extruded, the particles are not easily broken and the particle size is easily maintained. The reason why silica is preferable is that it can be obtained relatively cheaply than other particles. For precipitated particles containing calcium and phosphorus, there is no need to add particles again, it is inexpensive, deformation of the particles during stretching during film formation is small, protrusion height can be maintained, and good winding characteristics This is why it is preferable. In order to express the effect of the present invention, it is of course possible to employ a plurality of types of particles represented above.

  The greatest feature for exhibiting the maximum surface characteristics in the present invention is to suppress the deformation of particles as much as possible by stretching during film formation. In other words, the amount of particles is limited to maintain the glossiness, and the winding properties can be maintained when the surfaces of the final film contact each other even after the protrusion height is reduced by stretching and heat setting. In order to achieve this, it is necessary to select particle characteristics that can prevent deformation of the protrusion height by stretching.

  Although appropriate hardness exists depending on the above-mentioned particle type, for example, in the case of silica, it is necessary to pay attention to the hardness of the particle expressed by pore volume (surface area) (unit: ml / g) or average pore diameter There is. When the pore volume is reduced, that is, when the average pore diameter is reduced and the primary particles of silica are densely aggregated, deformation at the time of stretching is reduced, and the reduction in protrusion height is small. In addition, by appropriately selecting the amount of particles, glossiness and winding characteristics can be maintained at a high level. According to the knowledge found by the present inventors, the preferred pore volume (surface area) is in the range of 1.00-1.50 ml / g. When the pore volume is larger than 1.50 ml / g, the deformation during stretching is large, so that the protrusion height of the particles tends to be small and the winding characteristics tend to be impaired. When the pore volume is smaller than 1.00 ml / g, deformation during stretching becomes extremely small, the height of the protrusion of the particle becomes extremely large, and the glossiness may be impaired.

  In the production of the polyester containing the additive particles, the particles may be added during the polyester synthesis reaction or directly to the polyester. When added during the synthesis reaction, a method in which the particles are dispersed in ethylene glycol or the like as a slurry and added at any stage of the polyester synthesis is preferable. On the other hand, when added directly to the polyester, a method of adding and mixing to the polyester using a twin-screw kneading extruder as dry particles or as a slurry dispersed in water or an organic solvent having a boiling point of 200 ° C. or less is preferable. . The particles to be added may be subjected to a treatment such as crushing, dispersing, classification, and filtration in advance as necessary.

  As a method for adjusting the content of particles, a master raw material containing particles at a high concentration is prepared by the above-described method, and at the time of film formation, it is diluted with a raw material that does not substantially contain particles, and the particle content is reduced. It is effective to adjust this.

  Further, as additives other than the above-described protrusion forming agent, an antistatic agent, a stabilizer, a lubricant, a crosslinking agent, an antiblocking agent, an antioxidant, a colorant, a light blocking agent, an ultraviolet absorber, etc. May be contained within a range not impairing the effects of the present invention.

Next, the manufacturing method of the film of this invention is demonstrated concretely.
First, a polyester raw material is supplied to an extrusion apparatus. That is, it extrudes as a molten sheet from a slit-shaped die. Next, the molten sheet is rapidly cooled and solidified on the rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature to obtain a substantially amorphous non-oriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing the biaxial stretching conditions, the unstretched sheet is stretched in the first axial direction. The stretching temperature range is usually from 70 to 150 ° C., the stretching ratio is usually from 2.5 to 6 times, preferably from 3.8 to 4.8 times, and the stretching can be performed in one step or two or more steps. Next, in the second axis direction, that is, in the direction perpendicular to the first axis direction, the uniaxially oriented film is once cooled below the glass transition point, or pre-heated to a temperature range of, for example, 80 to 150 ° C. without cooling, Further, the film is stretched 2.5 to 5 times, preferably 4.0 to 4.7 times at substantially the same temperature to obtain a biaxially oriented film. In addition, it is preferable to perform the stretching in the first axial direction in two or more stages because good thickness uniformity can be achieved. In addition, a method of re-stretching in the longitudinal direction after transverse stretching is also possible. Also, so-called simultaneous biaxial stretching, in which stretching in the first axial direction and the direction perpendicular thereto, is simultaneously possible.

  The film thus obtained is heat-treated for 1 second to 5 minutes under elongation, limited shrinkage, or constant length within 30%. At this time, restretching may be performed in the longitudinal direction, the transverse direction, or both directions in or after the heat treatment step.

  By appropriately selecting the above-described stretching conditions and heat treatment conditions, it is necessary that the 20 ° gloss and the maximum cross-sectional height roughness (St) are within the scope of the present invention.

  In particular, in order to exhibit the winding characteristics of the film of the present invention, it is important to keep the frictional force acting in the longitudinal direction between the film surfaces low when the film is wound, and the protrusion shape of the MD direction particle Must be kept high. Therefore, in order to suppress flattening of the MD direction of the particles due to stretching, it is most preferable that the stretching ratio in the MD direction is suppressed to the necessary minimum, and as a result, the glossiness of MD is set to TD or less. The glossiness of MD means that the direction of incidence / reception of light when measuring glossiness is the same as the MD direction of the film, and the glossiness of TD is the incidence / reception of light when measuring glossiness. Means to match the TD direction of the film.

  In addition, in the range which does not inhibit the effect of this invention, according to various end uses, in order to provide adhesiveness with the layer which contacts, a coating layer can be provided in the film surface. In order to impart this adhesion, a polymer (binder polymer) comprising at least one selected from the group consisting of an aqueous polyester polymer and an aqueous acrylic polymer is particularly useful.

  In addition, urea, melamine, guanamine, and acrylamide that are methylolated or alkylolized as a crosslinkable polymer to improve adhesion resistance (blocking resistance), water resistance, solvent resistance, and mechanical strength of the coating layer Compounds, polyamide compounds, epoxy compounds, aziridine compounds, block polyisocyanates, silane coupling agents, titanium coupling agents, zircoaluminate coupling agents, peroxides, thermal and photoreactive vinyl compounds Or a photosensitive resin.

  Further, if necessary, it may contain an antifoaming agent, a coating property improver, a thickener, an antistatic agent, an organic lubricant, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, and the like. .

  As a method of applying the above-mentioned coating liquid to a polyester film, Yuji Harasaki, Tsuji Shoten, published in 1979, reverse roll coater, gravure coater, rod coater, air doctor coater or other coating apparatus shown in "Coating system" Can be used.

  In the present invention, from the viewpoint of cost, in order to provide a coating layer, a so-called in-line coating method in which coating is performed in the film manufacturing process is recommended.

  As a method of coating within the film production process, a coating solution is applied to an unstretched polyester film, and a method of biaxially stretching sequentially or simultaneously, coating to a uniaxially stretched polyester film, and further perpendicular to the previous uniaxially stretched direction. There is a method of stretching in the direction of the above, or a method of applying to a biaxially stretched polyester film and then stretching in the transverse and / or longitudinal direction.

  Since the film of the present invention has a smooth surface and specific characteristics, it can provide high functionality and its industrial value is high.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited by a following example, unless the summary is exceeded. In addition, the evaluation method in an Example is as follows. In Examples and Comparative Examples, “part” means “part by weight”, “%” means “wt%”, and “ppm” means “weight ppm”.

(1) Intrinsic viscosity of polymer [η] (dl / g)
1 g of the polymer was dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) and measured at 30 ° C.

(2) Average particle diameter of added particles (d50) (μm)
In an equivalent spherical distribution measured with a centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type) manufactured by Shimadzu Corporation, the particle size of 50% of the integrated volume fraction integrated from the large particle side was taken as the average particle size (d50) of the added particles. .

(3) Surface area (pore volume) of silica particles (ml / g)
Samples 0.10 to 0.15 g were weighed and measured with a SA-1100 type rapid surface area measuring device manufactured by Shibata Kagaku. Measurement method = BET single point method

(4) 20 ° gloss (film) (Gs 20 °)
A test piece was cut out from the central portion in the width direction of the film, and a 20 ° gloss (Gs of 20 °) was obtained by using the VGS-1001DP manufactured by Nippon Denshoku Industries Co., Ltd. by the following method (20-degree mirror method, JIS Z-8741). Was measured and calculated. Set the incident angle to 20 ° and the light receiving angle to 20 °, and set the test piece to keep flatness (so that the film does not bend), then cover the test piece with a zero cap, and the direction of incidence and reception Was measured at three points according to the longitudinal direction (MD) of the film and at three points according to the width direction (TD), and the average of the three points was taken as the value in that direction. When attaching the sample to the window to be set, apply a proper tension so that no wrinkle is generated. The MD average value (Gs20 ° (MD)) and the TD average value (Gs20 ° (TD)) were added and divided by 2 to obtain the 20 ° glossiness (Gs20 °) of the film.

(5) Maximum section height roughness St (nm)
A test piece is cut out from the center in the width direction of the film, and a non-contact roughness image is measured using a three-dimensional non-contact surface shape measurement system (MM537N-M100) manufactured by Ryoka System Co., Ltd. The maximum cross-sectional height roughness St (nm) was calculated. The evaluation area is a rectangle of 0.428 mm in the MD direction and 0.320 mm in the TD direction.

St = | Zs (x, y) max | + | Zs (x, y) min |
In the above formula, Zs (x, y) max is the maximum value of the roughness image (maximum peak height from the average surface in the evaluation region), and Zs (x, y) min is the minimum value of the roughness image ( It is the maximum valley depth from the average plane in the evaluation region.

(6) 5% elongation strength in the longitudinal direction (F-5 value)
Ten test pieces were cut out in the longitudinal direction (longitudinal direction) from the center in the width direction of the film. The width of the test piece was 15 mm. A mark with an interval of 50 mm is attached to the center in the longitudinal direction of each test piece, and a tensile test is performed using a tensile tester at a test piece gripping interval of 50 mm and a tensile speed of 200 mm / min. Measure the load and find it using the following formula. The average value of 10 points was defined as 5% elongation strength in the longitudinal direction.
F-5 (MPa) = 5% elongation load / original cross-sectional area of specimen

(8) Winding characteristics The following is the non-defective product ratio (ratio of rolls that could be wound without defects such as wrinkles) from a master roll produced by the method described in the examples to a roll of 500 mm width and 35000 m length. Judged by the criteria of.
◎: Good product rate is high and economic efficiency is good ○: Slightly good product rate is lowered, but is economically satisfactory level, good ×: Good product rate is low, economically harmful level, poor

(9) Production of sublimation-type thermal transfer ribbon Unrolled a good roll produced by the method described in (8) above, and coated a back coat layer coating on one side by a gravure coating method. Thereafter, it was stored in an oven at 55 ° C. for 5 days and cured to form a backcoat layer. The coating material for the backcoat layer is 5.0 parts by weight of Denkabutyral # 3000K (manufactured by Denki Kagaku Kogyo Co., Ltd.) as the polyvinyl acetal resin and 0.5 of Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.) as the isocyanate. Parts by weight, 20 parts by weight of phosphanol GB520 (manufactured by Toho Chemical Co., Ltd.) as the phosphate ester, 0.5 parts by weight of Nipsil E-200A (manufactured by Nippon Silica Industry Co., Ltd.) as the silica, and methyl ethyl ketone It was prepared by mixing 37 parts by weight and 37 parts by weight of toluene. Subsequently, the roll-shaped film after the backcoat layer is cured is rewound again, and yellow, yellow, magenta (red), cyan (blue) dyes and images are sequentially formed on the opposite surface of the backcoat layer. The protective layer (overcoat) coating was repeated, applied by gravure coating, and dried. About yellow (yellow) dye, it apply | coated so that it may become final thickness of 1.0 micrometer, and the coating material is 2.0 parts of macrolex yellow 6G (made by Bayer), and polyvinyl acetoacetal KS-5D (made by Sekisui Chemical Co., Ltd.). Was prepared by mixing 47.5 parts of methyl ethyl ketone and 47.5 parts of toluene. About magenta (red) dye, it apply | coats so that it may become final thickness of 1.0 micrometer, and the coating material is 3.0 parts of bimicron VPSN2670 (made by Bayer) and polyvinyl acetoacetal KS-5D (made by Sekisui Chemical Co., Ltd.). It was prepared by mixing 4.0 parts, 46.5 parts of methyl ethyl ketone and 46.5 parts of toluene. The cyan (blue) dye was applied to a final thickness of 1.0 μm, and the paint was Kayaset Blue 714 (Nippon Kayaku Co., Ltd.) and polyvinyl acetoacetal KS-5D (Sekisui Chemical Co., Ltd.) Prepared by mixing 4.0 parts of methyl ethyl ketone, 46.0 parts of methyl ethyl ketone, and 46.0 parts of toluene. About the coating material for screen protective layers, it apply | coated so that it might become final thickness 2.0micrometer, and a coating material is 20.0 weight part of CAB500-0.5 (made by Eastman Chemical Co.) as cellulose acetate butyrate resin, It was prepared by mixing 40.0 parts by weight of methyl ethyl ketone and 40.0 parts by weight of toluene.

(10) Image production (transfer of each color and transfer of protective layer)
For printing and thermal transfer on the dye receiving layer of photographic paper, a portion of the SVM-25LS ink ribbon, a sublimation type Digital Photo Printer DPP-SV series genuine media manufactured by Sony Corporation, was cut and described in (9) above. The ribbon produced by the method was used by joining together. A digital photo printer manufactured by Sony Corporation was used as a print for evaluation.

(10-1) Production of print unevenness determination image (solid black image) Specifically, first, a black solid image is created using the Adobe software Adope Photo Shop, and the data is printed on the printer. Transfer to DPP-SVM77, use an ink ribbon that replaces the thermal transfer film of the present invention as a part of the SVM-25LS ink ribbon, transfer a black solid image on photographic paper with the thermal transfer head of the printer, The protective layer was solid-transferred onto the image to obtain a black solid final image.

(10-2) Preparation of Glossiness and Glossiness Anisotropy Determination Image (White Solid Image) After a white solid image is transferred and printed on photographic paper in the same manner as (10-1) above The solid image of the protective layer was transferred onto the image to obtain a solid white final image.

(11) Print unevenness (defects)
Defects on the surface of the final image produced by the method described in (10-1) above were visually observed. In other words, when the ribbon is wrinkled during the transfer of each color, the color of the wrinkle portion is not transferred, and the final color is not black (= combination of yellow + red + blue), but becomes another color. Can be judged. The print unevenness was determined according to the following criteria.
: Printing unevenness is not recognized at all. excellence.
: Print unevenness is slightly recognized, but at a level that is practically acceptable. Good.

×: The level of uneven printing is not practical. Bad.

(12) Glossiness of image and anisotropy of glossiness Gloss Meter VG2000 (manufactured by NIPPON DENSHOKU) is used for the glossiness of the surface of the final image (solid white) produced by the method described in (10-2) above. 20 ° Gloss was measured in the direction corresponding to the longitudinal direction of the transferred ribbon, and the glossiness was determined according to the following criteria.
◎: Gloss is sufficient and excellent ○: Slightly lower gloss, but at a level that is not problematic for practical use, Good ×: Gloss is insufficient, unusable for practical use, poor Anisotropy of glossiness The surface of this final image was visually confirmed in the direction corresponding to the longitudinal direction and the width direction of the ribbon, and judged according to the following criteria.
◎: Glossiness anisotropy is not recognized and excellent ○: Glossiness anisotropy is slightly recognized, but is practically satisfactory level, and good ×: Glossiness anisotropy is large Unusable for practical use

The raw materials used in the following examples were prepared as follows.
(Polyester raw material a)
86 parts of terephthalic acid and 70 parts of ethylene glycol were placed in a reactor, and an esterification reaction was carried out at about 250 ° C. under a pressure of 0.5 kg / mm ² for 4 hours. Next, 0.015 parts of antimony trioxide, silica particles having an average particle diameter of 2.5 μm, a surface area of 1.25 ml / g, and 0.01 part of phosphoric acid were added. While gradually raising the temperature from 250 ° C. to 285 ° C., the pressure was gradually reduced from normal pressure to 0.5 mmHg. After 4 hours, the polycondensation reaction was stopped to obtain a polyester (a) having an intrinsic viscosity of 0.66. This polyester (a) contained 0.50% by weight of silica particles.

(Polyester raw material b)
Polyester (b) having an intrinsic viscosity of 0.66 is the same as polyester a except that silica particles having an average particle diameter of 2.5 μm and a surface area of 1.60 ml / g are added in place of silica particles in polyester raw material a. Obtained. This polyester (b) contained 0.50% by weight of silica particles.

(Polyester raw material c)
A polyester for dilution (c) having an intrinsic viscosity of 0.66 was obtained in the same manner as for the polyester a except that no silica particles were added to the polyester raw material a.

(Polyester raw material d)
A polyester (d) having an intrinsic viscosity of 0.66 is obtained in exactly the same manner as polyester a except that silica particles having an average particle size of 2.2 μm and a surface area of 1.60 ml / g are added in place of silica particles in the polyester raw material a. Obtained. This polyester (d) contained 0.50% by weight of silica particles.

(Polyester raw material e)
A polyester (e) having an intrinsic viscosity of 0.66 is obtained in exactly the same manner as the polyester a except that silica particles having an average particle diameter of 2.5 μm and a surface area of 0.90 ml / g are added in place of the silica particles in the polyester raw material a. Obtained. This polyester (e) contained 0.50% by weight of silica particles.

Example 1:
Polyester (a) and polyester (c) were mixed to obtain a raw material containing 0.06% silica particles having an average particle diameter of 2.5 μm and a surface area of 1.25 ml / g. The mixed raw material was dried by a conventional method, supplied to an extruder, melted at 290 ° C., extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method to obtain an amorphous sheet. The obtained sheet was stretched by 2.70 times at 90 ° C. in the longitudinal direction using a roll stretching method, and further stretched by 1.60 times at 75 ° C. Then, it led to the tenter, stretched 4.40 times at 110 ° C. in the transverse direction, and heat treated at 228 ° C. to obtain a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Example 2:
Polyester (a) and polyester (c) were mixed to obtain a raw material containing 0.06% silica particles having an average particle diameter of 2.5 μm and a surface area of 1.25 ml / g. The mixed raw material was dried by a conventional method, supplied to an extruder, melted at 290 ° C., extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method to obtain an amorphous sheet. The obtained sheet was stretched 2.70 times at 90 ° C. in the longitudinal direction using a roll stretching method, and further stretched 1.67 times at 75 ° C. Then, it led to the tenter, stretched 4.40 times at 110 ° C. in the transverse direction, and heat treated at 228 ° C. to obtain a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Example 3:
Polyester (a) and polyester (c) were mixed to obtain a raw material containing 0.10% of silica particles having an average particle diameter of 2.5 μm and a surface area of 1.25 ml / g. This mixed raw material was dried by a conventional method and supplied to an extruder, and a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm was obtained in exactly the same manner as in Example 1. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Example 4:
Polyester (a) and polyester (c) were mixed to obtain a raw material containing 0.06% silica particles having an average particle diameter of 2.5 μm and a surface area of 1.25 ml / g. The mixed raw material was dried by a conventional method, supplied to an extruder, melted at 290 ° C., extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method to obtain an amorphous sheet. The obtained sheet was stretched 2.70 times at 90 ° C. in the longitudinal direction using a roll stretching method, and further stretched 1.56 times at 75 ° C. Then, it led to the tenter, stretched 4.40 times at 110 ° C. in the transverse direction, and heat treated at 228 ° C. to obtain a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Example 5:
Polyester (a) and polyester (c) were mixed to obtain a raw material containing 0.08% silica particles having an average particle diameter of 2.5 μm and a surface area of 1.25 ml / g. The mixed raw material was dried by a conventional method, supplied to an extruder, melted at 290 ° C., extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method to obtain an amorphous sheet. The obtained sheet was stretched by 2.70 times at 90 ° C. in the longitudinal direction using a roll stretching method, and further stretched by 1.70 times at 75 ° C. Then, it led to the tenter, stretched 4.40 times at 110 ° C. in the transverse direction, and heat treated at 228 ° C. to obtain a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Comparative Example 1:
Polyester (b) and polyester (c) were mixed to obtain a raw material containing 0.06% of silica particles having an average particle diameter of 2.5 μm and a surface area of 1.60 ml / g. This mixed raw material was dried by a conventional method and supplied to an extruder, and a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm was obtained in exactly the same manner as in Example 1. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Comparative Example 2:
Polyester (a) and polyester (c) were mixed to obtain a raw material containing 0.06% silica particles having an average particle diameter of 2.5 μm and a surface area of 1.25 ml / g. The mixed raw material was dried by a conventional method, supplied to an extruder, melted at 290 ° C., extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method to obtain an amorphous sheet. The obtained sheet was stretched 2.70 times at 90 ° C. in the longitudinal direction using a roll stretching method, and further stretched 1.47 times at 75 ° C. Then, it led to the tenter, stretched 4.40 times at 110 ° C. in the transverse direction, and heat treated at 228 ° C. to obtain a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Comparative Example 3:
Polyester (d) and polyester (c) were mixed to obtain a raw material containing 0.12% of silica particles having an average particle size of 2.2 μm and a surface area of 1.60 ml / g. This mixed raw material was dried by a conventional method and supplied to an extruder, and a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm was obtained in exactly the same manner as in Example 1. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

Comparative Example 4:
Polyester (e) and polyester (c) were mixed to obtain a raw material containing 0.06% silica particles having an average particle size of 2.5 μm and a surface area of 0.90 ml / g. This mixed raw material was dried by a conventional method and supplied to an extruder, and a biaxially stretched polyester film (master roll) having a thickness of 4.5 μm was obtained in exactly the same manner as in Example 1. While being trimmed to a width of 500 mm from this master roll, the film was wound into a roll at a total length of 35000 m and a speed of 250 m / min on a 6-inch inner diameter core to obtain a roll film.

  The results obtained for Examples 1 to 5 and Comparative Examples 1 to 4 are summarized in Table 1 and Table 2 below.

  The film of the present invention can be suitably used, for example, as a polyester film for a sublimation type thermal transfer ribbon.

Claims (1)

The film thickness is 6 μm or less, the 20 ° glossiness (Gs20 °) of the film surface is 180% or more, the 5% elongation strength (F-5) in the film longitudinal direction (MD) is 115 MPa or more, and the film A polyester film for a sublimation thermal transfer ribbon, wherein the surface has a maximum cross-sectional height roughness (St) of 2000 nm or more.