JPH0512374B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a biaxially oriented polyester film, more specifically, it contains specific spherical silica particles and other inert inorganic fine particles having a smaller particle size,
This invention relates to a biaxially oriented polyester film with excellent slip properties and abrasion resistance. Polyester films, typified by polyethylene terephthalate films, are used in a wide range of applications because of their excellent physical and chemical properties. For example, it is used for magnetic tape, capacitors, photography, packaging, OHP, etc. In a polyester film, its slipperiness and abrasion resistance are major factors that determine the workability of the film manufacturing process and the processing process in each application, as well as the quality of the product.
If these are insufficient, for example, when a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, there will be severe friction between the coating roll and the film surface during application of the magnetic layer, and this will also cause severe abrasion of the film surface. In extreme cases, wrinkles, scratches, etc. may occur on the film surface. Furthermore, even after slitting the film coated with the magnetic layer and processing it into audio, video, or computer tape, there are many guide parts, playback heads, etc. when pulling it out from a reel or cassette, winding it, or other operations. Significant wear occurs between the polyester film, causing scratches and distortion, and furthermore, the surface of the polyester film is scratched and a white powdery substance is deposited, which is often a major cause of missing magnetic recording signals, that is, dropouts. Generally, to improve the slipperiness of a film, a method is adopted in which the contact area between the film and guide rolls etc. is reduced by adding irregularities to the film surface. A method of precipitating inert fine particles from the catalyst residue and (ii) a method of adding inert inorganic fine particles are used. A method of adding these raw material fine particles is used. Generally speaking, the larger the size of the fine particles in these raw polymers, the greater the effect of improving slipperiness. Since this itself can cause defects such as dropout, it is necessary that the irregularities on the film surface be as fine as possible, and there is currently a demand to satisfy these contradictory characteristics at the same time. Further, in a film made of polyester containing the above-mentioned inert fine particles, peeling occurs at the boundary between the fine particles and the polyester due to biaxial stretching, and voids are formed around the fine particles. These voids form as the fine particles become larger, as their shape changes from a plate-like shape to a grain-like or block-like shape, as a single particle becomes more difficult to deform, and as the stretching area magnification increases when stretching an unstretched film. Also, the lower the temperature, the larger the size. As these voids get larger, the shape of the protrusions becomes gentler, increasing the wear coefficient, and particles also tend to fall off due to small scratches on the voids of the biaxially oriented polyester film that occur during repeated use. This reduces durability and causes the generation of shavings. One or two of calcium carbonate, titanium oxide, kaolin, etc. as inert fine particles
Adding seeds or more (a combination of large particles and small particles) has traditionally been commonly done (Japanese Patent Application Laid-Open No. 1973-
34272, 52-78953, 52-78954, 53-41355, 53-
No. 71154), however, these fine particles form large voids and therefore have the above-mentioned problem, and an improvement in this problem is also desired. [Purpose of the Invention] The present inventor has solved these disadvantages, and has improved the slipperiness and abrasion resistance of the film by reducing the voids around the inert particles and making the film surface moderately rough. The present invention was developed as a result of intensive studies to obtain a biaxially oriented polyester film with surface properties suitable for various uses. Therefore, an object of the present invention is to provide a biaxially oriented polyester film with small voids and excellent slipperiness and abrasion resistance. [Configuration/Effects of the Invention] According to the present invention, an object of the present invention is that the first component in the polyester has an average particle size of 0.4 to 2 μm and a particle size ratio (major axis/breadth axis) of 1.0 to 1.2. and contains 0.005 to 0.5% by weight of spherical silica particles with a relative standard deviation of 0.5 or less, and as a second component, other inert particles having an average particle size smaller than that of the first component but in the range of 0.05 to 0.6 μm. This is achieved by a biaxially oriented polyester film characterized by containing 0.005 to 0.5% by weight of inorganic fine particles. Here, the major axis, minor axis, and area-circle-equivalent diameter of spherical silica particles are determined from an image magnified 10,000 to 30,000 times with an electron microscope after metal is deposited on the particle surface, and the average particle diameter and particle size ratio are is calculated using the following formula. Average particle diameter = sum of area circle-equivalent diameters of measured particles / ratio of several particle diameters of measured particles = average major axis of silica particles / average minor axis of the particles The polyester in the present invention has an aromatic dicarboxylic acid as the main acid component, It is a polyester whose main glycol component is aliphatic glycol. Such polyester is substantially linear;
It also has film-forming properties, particularly film-forming properties by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, naphthalene dicarboxylic acid, isophthalic acid, diphenylethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenylketone dicarboxylic acid, and anthracene dicarboxylic acid. Examples include acids. Examples of aliphatic glycols include alkylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, polyethylene glycol, and fats such as cyclohexanedimethanol. Examples include cyclic diols. In the present invention, polyesters containing, for example, alkylene terephthalate and/or alkylene naphthalate as main constituents are preferably used. Among such polyesters, for example, polyethylene terephthalate, polyethylene-2,6-
Not only naphthalate but also terephthalic acid and/or terephthalic acid and/or
or 2,6-naphthalene dicarboxylic acid, and a copolymer in which 80 mol% or more of the total glycol component is ethylene glycol is preferred. In this case, up to 20 mol% of the total acid component can be the above aromatic dicarboxylic acids other than terephthalic acid and/or naphthalene dicarboxylic acid; for example, aliphatic dicarboxylic acids such as adipic acid and sebacic acid; cyclohexane-1, It can be an alicyclic dicarboxylic acid such as 4-dicarboxylic acid. In addition, up to 20 mol% of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or aromatic diols such as hydroquinone, resorcinol, 2,2-bis(4-hydroxyphenyl)propane; , 4-dihydroxymethylbenzene; and polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. In addition, the polyester used in the present invention includes, for example, an aromatic oxyacid such as hydroxybenzoic acid;
-It also includes those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydrocosicaproic acid is copolymerized or combined in an amount of 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component. . Furthermore, the polyester in the present invention has a substantially linear amount, e.g.
Also included are copolymerized polycarboxylic acids or polyhydroxy compounds of trifunctional or higher functionality, such as trimellitic acid and pentaerythritol, in an amount of mol % or less. The above polyester is known per se, and can be produced by a method known per se. The polyester preferably has an intrinsic viscosity of about 0.4 to about 0.9 as measured as a solution in o-chlorophenol at 35°C. The biaxially oriented polyester film of the present invention has many fine protrusions on its surface.
According to the present invention, those many fine protrusions are comprised of a large number of spherical silica particles (first component) dispersed and contained in the polyester and other inert inorganic fine particles having a smaller particle size (second component). It originates from Polyesters containing dispersed inert particles are usually used during the reaction to form polyesters.
For example, spherical silica particles and other inert inorganic fine particles may be added individually or together (preferably (as a slurry in glycol) into the reaction system. Preferably, these inert particles are added to the reaction system at the beginning of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3. In the present invention, the spherical silica particles as the first component dispersed in the polyester have an average particle size of
0.4 to 2μm and particle size ratio (major axis/minor axis) is 1.0
~1.2 silica particles. These spherical silica particles have individual shapes that are extremely close to true spheres, and the silica particles conventionally known as lubricants are either ultra-fine lump particles of about 10 mμ or aggregates of about 0.5 μm. It is distinctive in that it is significantly different from forming particles (agglomerated particles). The average particle size of the spherical silica particles is preferably 0.5 to 1.7 μm,
More preferably, it is 0.6 to 1.5 μm. If the average particle size is less than 0.4 μm, the effect of improving slipperiness and abrasion resistance is insufficient, which is not preferable. Moreover, if the average particle diameter exceeds 2 μm, the film surface becomes too rough, which is not preferable. Further, the particle size ratio of the spherical silica particles is preferably 1.0 to 1.15, more preferably 1.0 to 1.1. Further, the spherical silica particles preferably have a sharp particle size distribution, and the relative standard deviation representing the steepness of the distribution is preferably 0.5 or less, more preferably 0.3 or less, and particularly preferably 0.12 or less. This relative standard deviation is expressed by the following formula. Here, Di: diameter equivalent to area circle of individual particle (μ
m) n: represents the number of particles measured. When spherical silica particles with a relative standard deviation of 0.5 or less are used, the heights of the large protrusions on the film surface are extremely uniform because the particles are spherical and have an extremely steep particle size distribution. Furthermore, the individual large protrusions on the film surface have a very sharp protrusion shape because the voids around the lubricant are small, so even if the number of large protrusions is the same, it will slip more easily than other lubricants. The properties are extremely good. The spherical silica particles are not limited in any way, including the manufacturing method, as long as the above-mentioned conditions are satisfied. For example, spherical silica particles are made of ethyl orthosilicate [Si
(OC ₂ H ₅ ) ₄ ] to hydrolyzed silica [Si
(OH) ₄ ] Monodisperse spheres are made, and the hydrated silica monodisperse spheres are further dehydrated to form silica bonds [≡Si−
It can be manufactured by growing O-Si≡] three-dimensionally (Japanese Chemical Journal '81, No. 9, P1503). Si(OC ₂ H ₅ ) ₄ +4H ₂ O→Si(OH) ₄ +4C ₂ H ₅ OH≡Si−OH+HO−Si≡ →≡Si−O−Si≡+H ₂ O Spherical silica as the first component in the present invention The amount of particles added is from 0.005 to polyester.
Must be 0.5% by weight, preferably 0.01~
It is 0.45% by weight, more preferably 0.02-0.4% by weight. If the amount added is less than 0.005% by weight, the effect of improving slipperiness and abrasion resistance will be insufficient, while if it exceeds 0.5% by weight, surface flatness will deteriorate, which is not preferable. In the present invention, the other inert inorganic fine particles as the second component to be dispersed and contained in the polyester are not particularly limited as long as they have an average particle size smaller than that of the first component but within the range of 0.05 to 0.6 μm. Other inert inorganic fine particles include inert inorganic fine particles precipitated into polymers from catalyst residues, such as calcium carbonate, magnesium carbonate, kaolin, clay, bentonite, titanium oxide, porous silica, and barium sulfate. , calcium titanate, barium titanate, fluorite, barium chromate, glass beads and the like. These can be used alone or in combination of two or more. The average particle size of such inert inorganic fine particles is 0.1 to 0.5μ,
Furthermore, it is preferably 0.15 to 0.4μ. In order to obtain particles with a predetermined average particle size, conventionally known particle preparation methods can be used. For example, it is preferable to perform a pulverization treatment, classification operation, etc. to obtain a predetermined average particle size and particle size distribution. . In the present invention, the content of inert inorganic fine particles as the second component is 0.005 to
Must be 0.5% by weight, preferably 0.01~
It is 0.45% by weight, more preferably 0.02-0.4% by weight. If this content is less than 0.005% by weight, the effect of improving slipperiness and abrasion resistance will be insufficient, while if it exceeds 0.5% by weight, surface flatness will deteriorate, which is not preferable. The biaxially oriented polyester film of the present invention can be produced according to conventional methods for producing biaxially oriented films. For example, a polyester containing spherical silica particles and other inert inorganic particles is melt-formed to form an amorphous unstretched film, and then the unstretched film is biaxially stretched and heat-set.
If necessary, it is produced by a relaxation heat treatment. At that time, the film surface characteristics depend on the particle size, amount, etc. of spherical silica particles and other inert fine particles.
Also, since it changes depending on the stretching conditions, it is selected appropriately from conventional stretching conditions. Furthermore, since the density, thermal shrinkage rate, etc. change depending on the temperature, magnification, speed, etc. during stretching and heat treatment, conditions are determined to satisfy these characteristics at the same time. For example, the stretching temperature ranges from (Tg− ₁₀ ) to (Tg
+45)°C (however, Tg: glass transition temperature of polyester), the second-stage stretching temperature (for example, transverse stretching temperature: T ₂ ) is from (T ₁ +15) to (T ₁ +40)
It is recommended to select from the range of ℃. Further, the stretching ratio is preferably selected from a range in which the uniaxial stretching ratio is 2.5 or more, particularly 3 times or more, and the area magnification is 8 times or more, especially 10 times or more. Furthermore, the heat fixing temperature is
It is preferable to select from the range of 180 to 250°C, more preferably 200 to 230°C. The biaxially oriented polyester film of the present invention has smaller voids than conventional films, and is particularly characterized by smaller voids around the spherical silica particles. The reason why the voids around the spherical silica particles are small is because the spherical silica particles have a good affinity for polyester, and because the particles themselves are very close to true spheres, the stress around the lubricant propagates evenly during stretching, allowing the polyester to bond with the polyester. It is presumed that this is because stress is not concentrated on a part of the lubricant interface. In the present invention, the distribution of large protrusions formed on the surface of the polyester film is extremely uniform due to the addition of spherical silica particles whose particle size distribution is extremely sharp, and a polyester film with uniform protrusion heights can be obtained. It will be done. By further containing inert inorganic fine particles in this film, it is possible to further improve the slipperiness while maintaining the abrasion resistance. The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness and abrasion resistance, and is characterized by significantly less generation of scratches, white powder, etc. This biaxially oriented polyester film can be widely used in various applications by taking advantage of these properties. For example, when used as a base film for magnetic recording, such as video, audio, and computer applications, excellent electromagnetic conversion characteristics, slipperiness, running durability, etc. can be obtained. Furthermore, when used in capacitor applications, low coefficient of friction, excellent windability, low crushing load, high transparency, etc. can be obtained. As mentioned above, this biaxially oriented polyester film is preferably used as a base film for magnetic recording media, especially as a base film for magnetic tapes, but it is not limited thereto, and can be used for electrical applications, packaging applications, deposition films, etc. It can be widely applied to other fields as well. [Examples] The present invention will be further explained below with reference to Examples.
Note that various physical property values and characteristics in the present invention were measured as follows. (1) Particle size (1-1) Regarding spherical silica particles There are the following conditions for measuring particle size. 1) When calculating the average particle size, particle size ratio, etc. from powder 2) When calculating the average particle size, particle size ratio, etc. of particles in the film 1) From powder Place the powder on the white of the electron microscope material. The individual particles are scattered so that they do not overlap as much as possible, and a thin gold film is deposited on the surface using a gold sputtering device to a thickness of 200 Å to 300 Å.
10,000~ under a scanning electron microscope.
Observe at a magnification of 30,000 times, and determine the major axis (Dli), minor axis (Dsi), and area circle equivalent (Di) of at least 100 particles using Luzetx 500 manufactured by Nippon Regulator Co., Ltd. Then, with the number average value expressed by these following formulas, the major axis (Dl), minor axis (Ds),
Represents the average particle size (). Dl = ( _o 〓 ^l=1 Dli) / n, Ds = ( _o 〓 ^{l = 1} Dsi) / n = ( _o 〓 ^{l = 1} Di) / n 2) For particles in a film A small piece of sample film is scanned The film was fixed on a sample stage for an electron microscope, and the surface of the film was subjected to ion etching treatment under the following conditions using a sputtering device (JFC-1100 type ion etching device) manufactured by JEOL Ltd. The conditions were to place the sample in a bell jar, increase the vacuum level to approximately 10 ^-3 Torr, and
Ion etching was performed for about 10 minutes at a voltage of 0.25 KV and a current of 12.5 mA. Furthermore, gold sputtering was applied to the surface of the film using the same equipment, and the film was observed using a scanning electron microscope at a magnification of 10,000 to 30,000 times. Determine the diameter (Dsi) and area circle equivalent diameter (Di). The following steps are carried out in the same manner as in 1) above. (1-2) Regarding other inert inorganic fine particles 1) Average particle size Shimadzu CP-50 type Centrifugal Particle Size Analyzer (Centrifugal
Particle Size Analyzer). From the cumulative curve of particles of each particle size and their abundance calculated based on the obtained centrifugal sedimentation curve, read the particle size corresponding to 50 mass percent,
This value is taken as the above average particle size ("Particle Size Measurement Technology")
Published by Nikkan Kogyo Shimbun, 1975, pp. 242-247). 2) Particle size ratio A small piece of film is fixed and molded into a rod shape of about 5 mmφ using epoxy resin, and an ultra-thin section with a thickness of about 600 Å is created using a microtome. This sample was examined using a Hitachi transmission electron microscope model H-800 at an accelerating voltage.
Observe the inert inorganic particles present in the cross section of the film at 100kV. The long axis and short axis of this particle are determined, and the particle size ratio is calculated. The number of particles to be observed is 20, the particle size ratio of each particle is determined, and the average value thereof is shown as the particle size ratio. 3) Relative standard deviation Obtain the differential particle size distribution from the cumulative curve in section 1), and calculate the relative standard deviation based on the following definition formula for relative standard deviation. Here, each particle size (μ
m); average diameter (μm) determined in section 1); n; number of divisions when determining the cumulative curve in section 1); φi; represents the existence probability (mass percent) of particles of each particle size. (2) Film surface roughness (Ra) This is the value defined in JIS-Bo601 as the center line average roughness (Ra). 30C). The measurement conditions are as follows. (a) Stylus tip radius: 2μm (b) Measuring pressure: 30mg (c) Cutoff: 0.25mm (d) Measuring length: 2.5mm (e) How to summarize data Measure the same sample 5 times and find the highest value Exclude one, round off the average value of the remaining four data to the fourth decimal place, and display up to the third decimal place. (3) Void ratio According to the method (1)-2) above, expose the area around the lubricant in the film (surface), measure the long axis of at least 50 solid particles and the long axis of the void, and calculate the following formula: Void ratio = It is expressed as the number average value of the void ratio determined by the long axis of voids/long axis of solid fine particles. (4) Coefficient of friction of film (μk) In an environment with a temperature of 20℃ and humidity of 60%, a film cut to a width of 1/2 inch was held with a fixed rod (surface roughness 0.3μm).
It is brought into contact with the object at an angle θ = 152/180π radians (152°) and moved (friction) at a speed of 200 cm/min. When the tension controller is adjusted so that the inlet tension T ₁ is 35 g, the exit tension (T ₂ : g) is detected by the exit tension detector after the film has traveled 90 m, and the running friction coefficient μk is calculated using the following formula. calculate. μk = (2.303/θ) log (T ₂ / T ₁ ) = 0.868 log (T ₂ /35) (5) Abrasion resistance The abrasion resistance of the running surface of the base film was evaluated using a 5-stage mini super calendar. . The calendar is a 5-stage calendar with nylon rolls and steel rolls, the processing temperature is 80℃, the linear pressure applied to the film is 200Kg/cm, and the film speed is 50℃.
It was run at m/min. The total length of the running film is 2000m.
The abrasion resistance of the base film was evaluated based on the dirt that adhered to the top roller of the calendar during running. <Four-level judgment> ◎ No stains on the nylon roll 〇 Almost no stains on the nylon roll × Very dirty nylon roll × × Severely dirty nylon roll (6) Haze (cloudiness) According to JIS-K674, Japan Precision Optics The haze of the film was determined using an integrating sphere HTR meter manufactured by Co., Ltd. Comparative Examples 1 to 6 Dimethyl terephthalate and ethylene glycol were transesterified, manganese acetate was used as a transesterification catalyst,
Polyethylene terephthalate with an intrinsic viscosity (orthochlorophenol, 35°C) of 0.62 was obtained by polymerization in a conventional manner using antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and inorganic fine particles shown in Table 1 as a lubricant. Ta. This polyethylene terephthalate (hereinafter referred to as PET)
After drying at 170℃ for 3 hours, the pellets are fed to the extruder hopper and melted at a melting temperature of 280 to 300℃.The molten polymer is passed through a 1mm slit die with a surface finish of about 0.3S and a surface temperature of 20℃. It was molded and extruded on a rotating cooling drum at 0.degree. C. to obtain an unstretched film of 200 .mu.m. The unstretched film thus obtained was heated at 75°C.
The material was preheated at , then heated with a single IR heater with a surface temperature of 900°C from 15 mm above between low-speed and high-speed rolls, stretched to 3.6 times, rapidly cooled, and then fed to a stenter at 105°C. It was stretched 3.7 times in the transverse direction.
The obtained biaxially stretched film was heat set at a temperature of 205° C. for 5 seconds to obtain a heat set biaxially stretched film having a thickness of 15 μm. The properties of these films are shown in Table 1. Examples 1 to 8 Instead of kaolin, spherical silica (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) as the first component shown in Table 2 and the second component were used instead of kaolin.
A biaxially oriented polyester film was obtained in the same manner as in Comparative Example 1 except for using other inert inorganic fine particles as a component. The properties of these films are shown in Table 2.

【table】

【table】

[Table] From Table 2, the examples using spherical silica particles and other inert inorganic fine particles have a small coefficient of friction after 200 passes, a good evaluation of the abrasion resistance, and good runnability and abrasion resistance. It can be seen that it is excellent. Comparative Example 7 A biaxially oriented polyester film was obtained in the same manner as in Comparative Example 1, except that bentonite shown in Table 3 was used instead of kaolin. The properties of this film are shown in Table 3.

[Table] Example 9 Instead of kaolin, spherical silica (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) as the first component shown in Table 4 and the second component were used instead of kaolin.
A biaxially oriented polyester film was obtained in the same manner as in Comparative Example 1 except for using kaolin as a component. The properties of this film are shown in Table 4.

【table】

[Table] From Table 4, it can be seen that the sample of Example 9 had an extremely flat surface while having excellent running properties, and was particularly excellent in abrasion resistance. Comparative Example 8 A biaxially oriented polyester film was obtained in the same manner as in Example 6, except that spherical tungsten oxide having the characteristics shown in Table 5 was used in place of the spherical silica in Example 6. The properties of this film are shown in Table 5.

[Table] From the comparison between Comparative Example 8 and Example 6, it can be seen that the particles according to the present invention have small voids around the particles and are excellent in abrasion properties. Furthermore, the reason why the coefficient of friction after 200 passes in Comparative Example 8 is extremely high is that the protrusions on the film surface formed by the additive particles are scraped or fallen off during repeated running. That is, it can be seen that it is important that the additive particles have a spherical shape and have good affinity with polyester.

Claims (1)

[Claims] 1. In the polyester, the first component has an average particle size of 0.4 to 2 μm and a particle size ratio (major axis/minor axis) of 1.0.
~1.2 and contains 0.005 to 0.5% by weight of spherical silica particles whose relative standard deviation expressed by the following formula is 0.5 or less, and as a second component, the average particle size is the first.
A biaxially oriented polyester film characterized in that it contains 0.005 to 0.5% by weight of other inert inorganic fine particles smaller than the components but in the range of 0.05 to 0.6 μm. Here, Di: Area circle equivalent diameter of individual particles (μm) n: represents the number of particles. 2. The biaxially oriented polyester film according to claim 1, wherein the other inert inorganic fine particles are at least one selected from the group consisting of kaolin, bentonite, titanium oxide, calcium carbonate, and porous silica.