JPH0437092B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a biaxially oriented polyester film containing fine particles and a specific compound and having improved surface flatness, slipperiness, and adhesiveness. [Prior Art] In recent years, biaxially oriented polyester films have made remarkable progress in fields such as magnetic recording media such as magnetic tapes and magnetic disks, capacitors, photographs, microfilms, and packaging. In each application of these biaxially oriented polyester films, strict control of the surface is required. In other words, it is used for magnetic recording media such as magnetic tapes and magnetic disks to prevent recording disturbances, for capacitors to prevent insulation defects, and for photographs and microfilms to prevent disturbances in image quality. For packaging purposes, the surface of biaxially oriented polyester film must be flat in order not to impair transparency or aesthetics. In addition, common to all of these applications, workability and quality must be maintained both during unwinding, processing, winding, and slitting when producing a product for that application, as well as during use after production. The surface of the polyester film must be smooth on both sides. In addition, lubricity is an important property when forming a biaxially oriented polyester film from the viewpoint of stable and economical production with less tearing. However, the long-awaited flatness and smoothness of the top
These are originally contradictory surface properties. In other words, it is extremely difficult to satisfy both properties at the same time; if priority is given to flatness, smoothness must be sacrificed to some extent; on the other hand, if priority is given to smoothness, flatness must be sacrificed to some extent. Conventionally, the following technologies have been proposed for the purpose of achieving both flatness and smoothness. A method in which part or all of the catalyst and color inhibitor used during polyester synthesis are precipitated during the reaction process and present in the film as fine particles (internal particles) (hereinafter referred to as internal particle generation method). A method of adding inert particles to the polyester synthesis reaction system such as titanium dioxide, talc, kaolinite, calcium carbonate, and silicon oxide (hereinafter referred to as external particle addition method). Used in conjunction with. A method of adding a neutral or partially neutralized montan wax metal salt or montan wax ester metal salt (Japanese Patent Application Laid-Open No. 139551/1983) or an ester product consisting of a polyol having three or more hydroxyl groups. How to
Publication No. 195143). (hereinafter referred to as organic lubricant addition method). However, in the biaxially oriented polyester film produced by such conventionally proposed technology, the internal particle generation method is likely due to the strong cohesive force between the particles, and because there are many coarse particles mixed in, the coarse particles form on the surface of the film. This has the disadvantage of worsening flatness and insufficient lubricity.The external particle addition method inevitably causes secondary agglomeration of particles, roughness of the average particle size, and inclusion of coarse particles, so flatness and lubricity cannot be improved. There is a drawback that they cannot be compatible, and even if the internal particle generation method and the external particle addition method are used together, the drawbacks of each cannot be overcome.
The technique disclosed in the publication has the disadvantage that it lacks lubricity because the organic melt bleeds out onto the film surface.The technique disclosed in Japanese Patent Application Laid-open No. 195143/1983 does not form a gel when an organic solvent is added during polymerization. Also, if it is added by rolling (adding it to the raw material after polymerization), the viscosity will drop rapidly during melt extrusion, so in both cases, it is difficult to obtain satisfactory surface properties (flat and smooth). sex)
However, even if any of these films were used to make a magnetic tape, the running properties of the magnetic tape and the electromagnetic conversion characteristics could not be achieved at the same time. [Object of the Invention] The object of the present invention is to provide a biaxially oriented polyester film that does not have the above-mentioned drawbacks, that is, is excellent in all three properties of surface flatness, lubricity, and adhesiveness. [Structure of the Invention] The present invention is characterized in that 100 parts by weight of polyester are mixed with 0.005 to 2 fine particles having an average particle size of 0.05 to 3 μm.
parts by weight of B, and 0.005 to 2 parts by weight of at least one compound whose main component is a higher aliphatic monocarboxylic acid having 10 to 33 carbon atoms or an ester thereof, and has a surface roughness of Ra. is 0.001~
0.025 μm, static friction coefficient μs 0.3 to 1, in-plane birefringence △
n is 0 to 0.15, thickness direction refractive index ratio is 0.935 to 0.980
It is characterized by a biaxially oriented polyester film. The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component. Specific examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, Examples include anthracene dicarboxylic acid and α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid. Among these, terephthalic acid is particularly desirable. Specific examples of alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, hexylene glycol, and the like. Among these, ethylene glycol is particularly desirable. Of course, these polyesters may be homopolyesters or copolyesters (copolymerized polyesters), and copolymerizable components include, for example, diethylene glycol, propylene glycol, neopentyl glycol, polyalkylene glycol, p- Xylylene glycol, 1,4-cyclohexanedimethanol, 5-
Diol components such as sodium sulforesorcin, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acids such as trimellitic acid, pyromellitic acid, etc. component, and oxycarboxylic acid components such as p-oxyethoxybenzoic acid. It should be noted that, of course, known additives such as antistatic agents, heat stabilizers, ultraviolet fabric absorbers, etc. may be added to the polyester in amounts that do not impair the effects of the present invention. The fine particles in the present invention are at least one type selected from well-known internal particles, inert particles, and organic particles insoluble in polyester. Internal particles are particles that are produced by combining a metal compound added during polyester synthesis, such as at least one compound such as a calcium compound, a magnesium compound, a lithium compound, or a phosphorus compound, with components constituting the polyester. Inert particles are chemically inert particles selected from oxides or inorganic salts of elements in Group 1 of the Periodic Table of the Elements, such as synthetic or natural calcium carbonate, wet silica, etc. (silicon dioxide), dry silica (silicon dioxide), aluminum silicate (kaolinite),
Examples include barium sulfate, calcium phosphate, talc, titanium dioxide, aluminum oxide, aluminum hydroxide, calcium terephthalate, calcium silicate, and the like. The organic particles insoluble in polyester are not particularly limited in type, and include, for example, fluorine-containing fine particle polymers and crosslinked polymer fine powders. The average particle size of the above-mentioned fine particles needs to be 0.05 to 3 μm, preferably 0.1 to 2 μm.
If it is less than 0.1 μm, the film will have insufficient lubricity, and if it exceeds 3 μm, the film will have poor flatness.
In addition, the content of the above fine particles is
It needs to be 0.005 to 2 parts by weight, preferably 0.005 to 1 part by weight, and more preferably 0.01 to 0.5 parts by weight, per 100 parts by weight. If the content is less than the lower limit of the above range, the coefficient of friction between films or between films and metal will increase, resulting in poor activity.On the other hand, if the content exceeds the upper limit of the above range, coarse The generation of particles increases, the surface roughness increases, and the flatness deteriorates. If a magnetic tape is made using a film with a content outside the appropriate range as described above, running properties and electromagnetic conversion characteristics will not be compatible. In the present invention, compounds whose main component is a higher aliphatic monocarboxylic acid having 10 to 33 carbon atoms include, as specific examples, capric acid, lauric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, and melisinic acid. acids, lignoceric acid, cerotic acid, montanic acid, hentriacontanoic acid, petroselic acid,
Examples include oleic acid, erucic acid, linoleic acid, and acid mixtures containing these. Among these, higher aliphatic monocarboxylic acids preferably have 18 to 33 carbon atoms, more preferably 20 to 32 carbon atoms,
It has the characteristic of greatly improving slipperiness. The higher aliphatic monocarboxylic acid ester in the present invention refers to the above-mentioned higher aliphatic monocarboxylic acid,
It is obtained by partially or completely esterifying it with a monohydric or dihydric alcohol having 2 to 33 carbon atoms. Specifically, montanic acid ethylene glycol ester, montanic acid ethyl ester, ceryl montanate, octacosyl lignocerate, mericyl lignocerate, seryl lignocerate, myricyl cerotate, seryl cerotate, etc. Also preferably used are tucus, carnauba wax, bees wax, candelilla wax, wax wax, and prickly wax. In the present invention, the main component refers to a compound containing 50% by weight or more of the compound. In the present invention, if the higher aliphatic monocarboxylic acid has less than 10 carbon atoms, it will bleed out to the film surface severely, resulting in significantly poor adhesion, and if the higher aliphatic monocarboxylic acid has more than 33 carbon atoms, lubricity cannot be obtained. . In the present invention, the ester consisting of a higher aliphatic carboxylic acid and an alcohol is obtained in a combination in which the number of carbon atoms of the acid and alcohol forming the structure is preferably 18 to 33, more preferably 20 to 32. Esters are desirable because they can impart good lubricity. In the present invention, higher aliphatic monocarboxylic acids,
The content of at least one compound consisting of the ester is based on 100 parts by weight of the polyester.
It should be 0.005 to 2 parts by weight, preferably
0.01 to 1 part by weight, more preferably 0.05 to 0.5 part by weight, and most preferably greater than 0.1 part by weight and 0.5 part by weight. If the above content is less than 0.005 parts by weight, the film will hardly have flatness or smoothness, and if it exceeds 2 parts by weight, bleed-out to the film surface will be severe and the adhesiveness will be extremely poor. As described above, in the present invention, both A. fine particles and B. a compound consisting of a higher aliphatic monocarboxylic acid and its ester (hereinafter abbreviated as "higher fatty acid compound") must be contained. is necessary. Inclusion of only A or only B does not produce the effects of the present invention. The reason why it is necessary to contain both is that B is more important than A in the polyester.
This is because there is a synergistic effect of finely dispersing the. The surface roughness (Ra) in the present invention is measured by the method described below, and the range thereof must be 0.001 to 0.025 μm, preferably 0.001 to 0.023 μm, More preferably 0.001 to 0.018μm, most preferably 0.001 to 0.018μm
It is 0.014μm. If the surface roughness (Ra) is less than 0.001 μm, it will be too flat and scratches will easily occur.
On the other hand, when Ra exceeds 0.025μ, flatness is poor. And when Ra goes out of the preferred range like this,
A magnetic tape using this film has incompatible electromagnetic conversion characteristics and runnability. The static friction coefficient (μs) in the present invention is measured by the method described below, and its range needs to be 0.3 to 1, preferably 0.4
-0.9, more preferably 0.4-0.8. If the static friction coefficient (μs) is less than 0.3, loose winding occurs during operation. On the other hand, if it exceeds 1, the lubricity will be insufficient and high-speed running properties during processing will deteriorate. In the present invention, the film must be biaxially oriented. If it is not a biaxially oriented film, it will be difficult to keep the surface roughness, coefficient of static friction, in-plane birefringence, and refractive index ratio in the thickness direction within the above ranges, and thickness unevenness, rigidity, and dimensional stability will be fatal. The degree of biaxial orientation is such that the in-plane birefringence Δn is 0 to
0.15, preferably 0 to 0.10, the refractive index ratio in the thickness direction is
It needs to be between 0.935 and 0.980, and furthermore, it is desirable that the sum of the in-plane refractive indices is between 3.2 and 3.42. The in-plane birefringence Δn here refers to the refractive index in the vertical direction, horizontal direction, and thickness direction of the film measured at 25°C and 65% RH with an Atsube refractometer using sodium D line. It is the absolute value of the difference between the refractive index in the direction and the horizontal direction, and the sum of the in-plane refractive index is the sum of the refractive index in the vertical direction and the refractive index in the horizontal direction, and
The refractive index ratio in the thickness direction is the ratio of the refractive index P in the thickness direction of the film to the refractive index Q in the thickness direction of an amorphous film obtained by melt-pressing the film and quenching it in 10°C water, that is, P/Q. It is. If the degree of biaxial orientation deviates from the above-mentioned preferred range, it becomes difficult to achieve both flatness and slipperiness of the film, and it becomes difficult to achieve both running performance and electromagnetic conversion characteristics of a magnetic tape using the film, which is not desirable. The thickness of the film of the present invention is preferably 3 to 125 μm, preferably 4 to 80 μm, and more preferably 4 to 75 μm. It is desirable to provide a magnetic layer on at least one side of the film of the present invention to form a magnetic recording medium. This magnetic layer is a well-known magnetic layer in which a powdered magnetic material such as γ-Fe ₂ O ₃ , Co-doped γ-Fe ₂ O ₃ , CrO ₂ , or a ferromagnetic alloy is dispersed in an organic binder. , a magnetic layer formed by a method of coating with a thickness of 0.3 to 5 μm, or a magnetic layer formed by coating a ferromagnetic metal such as Fe, Co, Ni, or other ferromagnetic metal or a magnetic alloy containing them, for example, by vacuum evaporation, sputtering, ion plating, electroplating, etc. The magnetic layer may be formed with a thickness of 10 to 1000 nm depending on the method, but
It is desirable to provide the latter magnetic layer in order to advantageously exhibit the effects of the present invention and improve the accuracy of the magnetic recording medium. Next, the outline of the method for manufacturing the biaxially oriented film and magnetic recording medium of the present invention will be described. However, it is not limited to this. (1) Method for producing biaxially oriented film: First, fine particles and a higher fatty acid compound are added to polyester. The addition method may be before the reaction, during the reaction, after the reaction, or during melt extrusion of the polyester polymerization. Also preferably employed is a method in which a master containing fine particles and a higher fatty acid compound separately or together at a high concentration in polyester is diluted and mixed with polyester. In this way, a polyester containing a specific particle source A and a specific amount of a higher fatty acid compound B is melt-extruded in an extruder, cast into a sheet, and stretched and oriented using a well-known method. The stretching method is not particularly limited, but for example, simultaneous biaxial stretching, or an appropriate combination of vertical stretching in one direction using rolls and horizontal stretching in one direction using clips,
Vertical → horizontal, vertical → horizontal → vertical, horizontal → vertical, 2
Examples include vertical → horizontal, 2 vertical → horizontal → vertical, 2 vertical → horizontal → 2 axes at the same time. Then, if necessary, heat treatment is performed while providing appropriate relaxation. Then, if necessary, at least one side is subjected to well-known corona discharge treatment, plasma treatment, etc., and then wound up. (2) Method of manufacturing a magnetic recording medium: The above-described magnetic layer is formed on one side of the biaxially oriented film obtained as described above, and then, for example,
Make magnetic tape. [Effects and Applications of the Invention] The biaxially oriented polyester film of the present invention contains specific amounts of fine particles having a specific diameter and a specific higher fatty acid compound, and has excellent surface roughness, static friction coefficient, and in-plane complex Since the refraction Δn and the refractive index ratio in the thickness direction are within a specific range,
It has the advantage of being both flat and slippery, and also has excellent adhesion to metals such as aluminum and printing ink. Moreover, it has the effect of being excellent in the durability of lubricity and abrasion resistance. Furthermore, since the surface roughness is small, there is also the effect of good transparency (small film haze). Furthermore, since it has a good coefficient of friction, it has the effect of good running properties and ease of handling in the film forming/slitting winding/unwinding process and the post-product processing process, and has the effect of eliminating winding irregularities, scratches, and projection transfer. . Because of the above effects, the polyester film of the present invention is suitable for use as a base film for magnetic recording media such as magnetic tapes and floppy disks, optical base films, condenser base films, graphic base films, and packaging base films. In particular, it is suitable for use as a base for magnetic recording media such as video tape recorders and magnetic recording disks, which have recently been required to be smaller and lighter, and as a base for vapor-deposited foil-wound capacitors. Furthermore, it is especially suitable for magnetic recording media, such as metal tapes that require higher density, tapes and disks made by vapor deposition or sputtering, and the most suitable ones are those with thin magnetic layers. This is a vapor-deposited tape application where runnability is important. In addition, when used as a magnetic recording medium, since the film of the present invention has both flatness and slipperiness, it has the effect of being superior in both electromagnetic conversion characteristics and runnability compared to conventionally known magnetic recording media. Obtainable. The effective magnetic recording medium using the film of the present invention can be used as a magnetic tape, magnetic card, or magnetic disk for computers, audio, video, and measurement applications, and is particularly preferably used for video applications. . [Method for Measuring Properties and Criteria for Evaluation] The methods for measuring properties and evaluation criteria in the present invention are as follows. (1) Average particle diameter φ (μm) of fine particles: Determined from the equivalent spherical diameter of particles at the 50% weight point measured by optical microscopy or electron microscopy. Equivalent spherical diameter is the diameter of a sphere with the same volume as the particle. (2) Surface roughness Ra (μm): Indicates the value measured by a stylus type surface roughness meter (value at cutoff 0.25 mm, measured value 4 mm. However, JIS-B
-0601). (3) Static friction coefficient μm: Measured using a slip tester in accordance with ASTM-D-1894B-63. (4) Film haze Measured according to ASTM-D-1003-52.
Transparency is good if it is 3.5% or less in terms of a 15 μm thick film. (5) Adhesion (5)-A Aluminum deposition strength Belgear type high vacuum deposition equipment (manufactured by Japan Vacuum Technology Co., Ltd.)
EBH-6 model) was used to deposit Al to a thickness of approximately 100 nm at a vacuum level of approximately 1 × 10 ^-5 mmHg, and a commercially available cellophane adhesive tape manufactured by Nichiban Co., Ltd. was attached to the Al-deposited surface and peeled off at 90°. Evaluation was made based on the remaining Al adhesion area. The criteria for evaluation are as follows.

[The friction member was made of SUS with a diameter of 5 mm, and the winding angle of the film was 180 degrees so that the side surfaces of the continuous layer were in contact with each other. ]

For magnetic tapes, μk is preferably 0.35 or less, more preferably 0.30 or less, and still more preferably 0.26 or less. (7) Durability of slipperiness: The surface of the tape-shaped film is made of metal (SUS).
After repeatedly running in contact with a fixed guide (5 mmφ) 500 times, μs as described in (3) above was measured. If the difference is within 0.1 of μs at the start of running, the durability is evaluated as good (○), and if the difference exceeds 0.1, the durability is evaluated as poor (×). (8) Abrasion resistance: The surface of the tape-shaped film is made of metal (SUS).
After repeatedly running in contact with a fixed guide (5 mmφ) 500 times, the amount of scratches adhering to the film was observed, and the number of scratches was evaluated as follows.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on Examples. Example 1 An ester conversion reaction was carried out in a conventional manner using 100 parts by weight of dimethyl terephthalate, 62 parts by weight of ethylene glycol and 0.06 parts by weight of calcium acetate as a catalyst, and the product was mixed with 0.04 parts by weight of antimony trioxide,
0.07 parts by weight of lithium acetate and calcium acetate
After adding 0.04 parts by weight, 0.02 parts by weight of phosphorous acid and 0.10 parts by weight of trimethyl phosphate, polycondensation was performed to obtain a solution with an intrinsic viscosity of 0.618 and an internal particle amount (average particle size 1.0 μm) of 0.35 parts by weight. (100 parts by weight based on polyester) was obtained. Internal particles contain 1.2% by weight of calcium element and lithium element.
It contained 1.9% by weight and 4.9% by weight of phosphorus element (polyester: A). 100 parts by weight of terephthalic acid and ethylene glycol
A slurry was prepared by kneading 43 parts by weight. into the reactor
The slurry is continuously added at a constant rate to a reactant of 50 parts by weight of terephthalic acid and 21.5 parts by weight of erylene glycol stored at 245°C, and the esterification reaction is carried out at 245°C under normal pressure, and the resulting water is collected in a rectifying column. It was continuously distilled out of the system. The supply time of the slurry was completed in 3 hours and 30 minutes, and the esterification reaction was completed in 4 hours. From the obtained reaction product, an esterification reaction product equivalent to 100 parts by weight of terephthalic acid was transferred to a polymerization apparatus, and 0.045 parts by weight of phosphoric acid, 0.023 parts by weight of antimony trioxide, and 2.3 parts by weight of calcium carbonate having an average particle size of 1.5 μm were added. It was added as an ethylene glycol slurry and subjected to polycondensation reaction according to a conventional method. The obtained polymer had an intrinsic viscosity of 0.615, contained no internal particles defined by the present invention, and contained 2 parts by weight of calcium carbonate (polyester: B). Polyester: A polymer having an intrinsic viscosity of 0.62 without the addition of inert particles was obtained in the same manner as in B (polyester: C). Polyester: Polycondensation was carried out in the same manner as B without adding inert particles, and after the reaction, 2.3 parts by weight of carnauba wax was added and kneaded for about 10 minutes to obtain a polymer with an intrinsic viscosity of 0.610. (Polyester: D). Polyester thus obtained: A, B,
Blend C and D and dry under reduced pressure (170℃, 2 hours)
After that, the internal particles were added to 100 parts by weight of polyester.
A polymer composition consisting of 0.17 parts by weight, 0.1 parts by weight of calcium carbonate, and 0.05 parts by weight of carnauba wax was obtained. The composition was melt-pressed at 285°C and cast on a cooling drum at 60°C to form a non-stretched sheet.
By a conventional sequential biaxial stretching method, the film was first stretched 3.3 times in the longitudinal direction at 90°C between a pair of rolls with different circumferential speeds. The refractive index is 1.64 and 1.54 in the vertical and horizontal directions, respectively, and the in-plane birefringence Δn is
It was 0.10. Next, it was folded into a tenter, held at both ends with clips, and stretched 3.5 times in the transverse (width) direction at 95°C, and heat-treated at 218°C for 5 seconds while being relaxed by 5% in the width direction in the same tenter.
The biaxially oriented film that came out of the tenter was then subjected to Cotona discharge treatment on both sides with an energy of 50 W·min/m ² , and then wound up to obtain a polyethylene terephthalate biaxially oriented film having a thickness of 15 μm. The windability of these films was very good.
The refractive index of this film in the vertical direction, horizontal direction, and thickness direction was 1.63, 1.66, and 1.50 (P), respectively. Moreover, the refractive index (Q) was 1.57. Therefore, the in-plane birefringence Δn was 0.03, the sum of the internal refractive indices was 3.29, and the refractive index ratio in the thickness direction was 0.95. Table 1 shows the results of measuring and evaluating the properties of these films. The film properties showed the same values and results on both sides. From Table 1, the film of Example 1 has flatness (Ra), slipperiness (μs), transparency (haze), adhesiveness (Al vapor deposition strength, printing ink adhesive strength),
It can be seen that it has excellent running performance (μs), durability of slipperiness, and abrasion resistance. Next, a magnetic paint was applied to one side of the film of the example by the following method to prepare a magnetic tape.
That is, ferromagnetic alloy powder (Fe-Co) 300 parts by weight Zinc powder (average particle size 2 μm) 25 parts by weight Cellulose acetate butyrate 30 parts by weight Epoxy resin 25 parts by weight Silicone oil 4 parts by weight Lecithin 5 parts by weight Toluene (solvent) A composition consisting of 200 parts by weight of lythyl ethyl ketone (solvent), 200 parts by weight of ethyl acetate (solvent), and 100 parts by weight of ethyl acetate (solvent) was placed in a ball mill and thoroughly kneaded, and then 180 parts by weight of a polyisocyanate compound (Desmodeur L-75) was added. After stirring and mixing for 30 minutes, the mixture was coated on one side of the above polyethylene terephthalate film to a dry thickness of 4 μm while applying a magnetic field, and dried. After that, it was hardened and mirror-finished, and then slit into 1/2-inch pieces to make a videotape. Table 1 also shows the results of evaluating the magnetic tape properties of the films thus obtained. From the measurement evaluation results of magnetic tape characteristics in Table 1,
It can be seen that the magnetic tape using the film of Example 1 has good magnetic film adhesion, magnetic tape running properties, and electromagnetic conversion characteristics. Examples 2 to 7 Comparative Examples 1 to 11 Polyester of Example 1: In the same manner as B, instead of calcium carbonate, dry silica (SIO ₂ ) with an average particle size of 0.3 μm (Nippon Aerosil Co., Ltd.) was added to 100 parts by weight of polyethylene terephthalate. A polyester containing 1.0 part by weight of "Aerosil" R-972 (manufactured by Co., Ltd.) was obtained (polyester: E). Polyester: Similar to D, a polymer containing 2.3 parts by weight of montanic acid was obtained (Polyester: F). Polyester thus obtained: A, B, C, D,
Appropriate amounts of E and F were selected and combined and blended. The stretching conditions in Examples 2 and 3 are the same as in Example 1. Examples 4 and 5 were stretched 3.3 times in the vertical direction at 90°C and then 4.2 times in the horizontal direction at 100°C.
A biaxially stretched film with a thickness of 15 μm was obtained by heat treatment at ℃ for 5 seconds. In addition, Examples 6 and 7 were stretched 3.4 times in the vertical direction at 85°C, and then stretched in the horizontal direction at 100°C.
Stretched 4.0 times and heat treated at 215℃ for 5 seconds.
A 15 μm biaxially stretched film was obtained. Comparative Examples 1 to 10 were carried out under the same stretching conditions as in Example 1. In addition, in Comparative Example 11, appropriate amounts of polyesters A, B, and C of Example 1 were selected and combined,
The film was stretched 3.5 times in the vertical direction at 80°C and 3.6 times in the horizontal direction at 110°C, and then heat treated at 200°C for 5 seconds to obtain a biaxially oriented polyethylene terephthalate film with a thickness of 15 μm. The properties of these films are shown in Table 1. Examples 2 to 7 fall within the scope of the claims of the present invention, and include flatness, lubricity, transparency (Al vapor deposition strength, printing ink adhesion strength), runnability (μk), durability of lubricity,
It can be seen that it is excellent in both abrasion resistance. On the other hand, each of the films of Comparative Examples 1 to 11 did not meet any of the requirements of the claims of the present invention, and therefore had poor characteristics of the film. Next, a Co-Ni alloy (Co/Ni alloy) was applied as a magnetic layer on one side of each film of Examples 2 to 7 and Comparative Examples 1 to 11.
Ni = 80/20 weight ratio) was vacuum deposited to a thickness of 100 nm, and slit into 1/2 inch width to obtain a deposited magnetic tape. As a result of measurement and evaluation of these magnetic tapes, all of the examples were excellent in terms of adhesion of the magnetic layer to the film, magnetic tape running properties, and electromagnetic conversion characteristics. On the other hand, all of the comparative examples that did not meet any of the requirements of the claims of the present invention had defects in some of the magnetic tape characteristics.

【table】

[Table] (Note) In the above composition table, the marks 〓-〓 mean 〓No〓.

Claims (1)

[Claims] 1. 100 parts by weight of polyester, A. 0.005 to 2 fine particles with an average particle size of 0.05 to 3 μm.
B contains 0.005 to 2 parts by weight of at least one compound consisting of a higher aliphatic monocarboxylic acid having 10 to 33 carbon atoms or an ester thereof as a main component, and has a surface roughness Ra of 0.001 to 2.
0.025μm, static friction coefficient 0.3~1, in-plane birefringence Δn
A biaxially oriented polyester film having a refractive index ratio of 0 to 0.15 and a refractive index ratio in the thickness direction of 0.935 to 0.980.