JPH054415B2 - - 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 spherical silica particles with different average particle diameters, is flat, and has properties such as smoothness, abrasion resistance, scratch resistance, and rollability. This invention relates to a biaxially oriented polyester film with excellent properties. [Prior Art] Polyester films, represented by polyethylene terephthalate films, are used in a wide range of applications due to their excellent physical and chemical properties, such as magnetic tapes, capacitors, photographs, packaging, and OHP applications. It is used in 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 applying a magnetic layer to the surface of a polyester film and using it 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, resulting in extreme In some 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 in which inert fine particles are precipitated from the residue and a method in which inert inorganic fine particles are added are 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 dropouts, the unevenness on the film surface needs to be as fine as possible, and the current situation is that there is 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 are formed when the fine particles are larger, when the shape is more spherical than plate-like, when the fine particles are single particles and are less likely to deform, and when the unstretched film is stretched, the larger the stretching area magnification is, and the lower the temperature is. The larger it becomes. As these voids get larger, the shape of the protrusions becomes gentler, increasing the coefficient of friction, and even small scratches on the voids of the biaxially oriented polyester film that occur during repeated use can prevent particles from falling off. This reduces durability and causes the generation of shavings.
It has traditionally been common practice to add one or more types (a combination of large particles and small particles) of calcium carbonate, titanium oxide, kaolin, colloidal silica, etc. as inert particles. The above-mentioned problem is inherent due to the formation of voids, and improvement of this problem is desired. [Objective of the Invention] The present inventor has solved these disadvantages, reduced the voids around the particles, and roughened the film surface to an appropriate degree, thereby improving the slipperiness and abrasion resistance of the film, and making it suitable for various uses. As a result of extensive research in order to obtain a biaxially oriented polyester film with surface properties suitable for this purpose, the present invention was achieved. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a biaxially oriented polyester film that has few voids, is flat, and has excellent slip properties, abrasion resistance, scratch resistance, and winding properties. [Configuration and Effects of the Invention] According to the present invention, an object of the present invention is to provide polyester with an average particle size of 0.3 μm or more as a first component.
Less than 0.6μm, particle size ratio (major axis/minor axis) is 1.0
~1.2 and the relative standard deviation expressed by the following formula is 0.5 or less in a range of more than 0.5% by weight and 2.5% by weight or less, and the second
As a component, spherical silica particles having an average particle diameter of 0.6 to 3.0 μm, a particle size ratio (major axis/breadth axis) of 1.0 to 1.2, and a relative standard deviation expressed by the following formula of 0.5 to 2. This is achieved by a biaxially oriented polyester film characterized in that it contains within the range of % by weight and below the amount of the first component. Here, Di: Equivalent area circle diameter of each particle (μm): Average value of area circle equivalent diameter (= _o 〓 ⁱ⁼¹ Di/n) (μm) n: Represents the number of particles. The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. 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, naphthalenedicarboxylic acid, isophthalic acid, diphenylethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid, and anthracenedicarboxylic acid. Examples include acids. Examples of aliphatic glycols include polymethylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, and alicyclic glycols such as cyclohexanedimethanol. Diols and the like can be mentioned. 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 dicarboxylic acid of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and/or 2,6-naphthalene dicarboxylic acid, and also fatty acids such as adipic acid, sebacic acid, etc. group dicarboxylic acids; alicyclic dicarboxylic acids such as cyclohexane-1,4-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, etc.; Aliphatic diols containing aromatics such as 1,4-dihydroxymethylbenzene; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. can also be used. In addition, the polyester used in the present invention includes, for example, an aromatic oxyacid such as hydroxybenzoic acid;
Also included are those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as -hydroxycaproic 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 those copolymerized with a trifunctional or higher functional polycarboxylic acid or polyhydroxy compound, such as trimellitic acid, pentaerythritol, etc., 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. In the present invention, these many fine protrusions are derived from many spherical silica particles dispersed and contained in the polyester. The polyester containing such spherical silica particles dispersed therein is usually prepared at any time during the reaction to form the polyester, for example, during the transesterification reaction using the transesterification method, or during the polycondensation reaction.
Alternatively, it can be produced by adding spherical silica particles (preferably as a glycol slurry) to the reaction system at any time when using a direct polymerization method. Preferably, spherical silica 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 dispersed in polyester have a particle size ratio (major axis/minor axis) of 1.0.
-1.2, preferably 1.0-1.15, more preferably 1.0
~1.1, and the individual shapes are extremely close to perfect spheres. The spherical silica particles have an average particle size of 0.3 μm or more and less than 0.6 μm, preferably 0.3 to 0.55 μm, more preferably 0.3 to 0.5 μm (first component), and 0.6 to 3.0 μm average particle size. Preferably 0.7 to 2.0 μm, more preferably 0.8 to 1.5 μm
There are two types: m (second component). These spherical silica particles are conventionally known as lubricants, which are either ultra-fine lumpy particles of about 10 mμm, or aggregates of these particles to form aggregates (agglomerated particles) of about 0.5 μm. They are characterized by significant differences. If the average particle size of the spherical silica particles as the first component is less than 0.3 μm, the effect of improving slipperiness will be insufficient, while if it is 0.6 μm or more, the surface flatness will be insufficient, which is not preferable. Moreover, if the average particle diameter of the spherical silica particles as the second component exceeds 3.0 μm, the surface flatness will be insufficient, which is not preferable. Here, the major axis, minor axis, and area-equivalent diameter of the spherical silica particles are determined from an image magnified, for example, 10,000 to 30,000 times with an electron microscope after metal is deposited on the particle surface. The ratio is calculated using the following formula. Average particle diameter = sum of area circle equivalent diameters of measured particles /
Particle size ratio of measured particles = Average major axis of silica particles / Average minor axis of the particles In addition, spherical silica particles must have a sharp particle size distribution, and the relative standard deviation representing the steepness of the distribution is 0.5 or less. Further, it is preferably 0.3 or less, particularly 0.12 or less. This relative standard deviation is expressed by the following formula. Here, Di: Diameter equivalent to a circle of area of each particle (μm): Average value of equivalent circle diameter of area (= _o 〓 ⁱ⁼¹ Di/n) (μm) n: Represents the measured number of particles. When spherical silica particles with a relative standard deviation of 0.5 or less are used, the particles are truly spherical and have an extremely steep particle size distribution, so the distribution of protrusions formed on the film surface is extremely uniform, and the protrusion height is A polyester film with uniform smoothness and excellent slip properties can be obtained. It is preferable that the average particle size of the first component and the average particle size of the second component have a difference of 0.1 μm or more, more preferably 0.2 μm or more. Further, it is preferable that the particle size distributions of the first component and the second component do not substantially overlap each other. 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
_{Hydrous silica} [ _Si
(OH) ₄ ] Monodisperse spheres are made, and the hydrated silica monodisperse spheres are further dehydrated to form silica bonds [≡Si−
O-Si≡] can be produced by three-dimensional growth (Journal of the Chemical Society of Japan '81, No. 9, P. 1503). 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 Addition amount of particles is 0.5% by weight based on polyester
More preferably within the range of 2.5% by weight or less, preferably 0.55 to 2.0% by weight, more preferably 0.55 to 1.5% by weight.
Weight%. In addition, the amount of spherical silica particles added as the second component is 0.005~
It is within the range of 2% by weight, preferably 0.01 to 1% by weight, more preferably 0.02 to 0.7% by weight, and less than the amount of the first component. If the amount of the first component added is less than 0.5% by weight, it is not preferable because when several thousand meters of film are wound onto a roll, small abnormal protrusions and wrinkles will occur on the roll surface, resulting in a high proportion of downgraded products. On the other hand, if the amount added exceeds 2.5% by weight, the film surface flatness will become insufficient, which is not preferable. In addition, the amount of the second component added is 0.005
If it is less than 2% by weight, the effect of improving slipperiness and abrasion resistance will be insufficient, while if it is more than 2% by weight, the surface flatness of the film will be insufficient, which is not preferable. Further, the total amount of the first component and the second component is 0.01 to 4.0% by weight, preferably 0.02 to 3.0% by weight, and more preferably 0.04 to 2.0% by weight. If the total amount added exceeds 4.0% 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, polyester containing a predetermined amount of spherical silica particles is melt-formed to form an amorphous unstretched film, then the unstretched film is stretched biaxially, heat-set, and if necessary, subjected to relaxation heat treatment. Manufactured by At this time, since the film surface characteristics change depending on the particle size, amount, etc. of the spherical silica particles, and also depending on the stretching conditions, conventional stretching conditions are selected as appropriate. 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 is such that the first stage stretching temperature (e.g. longitudinal stretching temperature: T ₁ ) is (Tg-
10) - (Tg + 45) °C (however, Tg: glass transition temperature of polyester), the second-stage stretching temperature (for example, transverse direction stretching temperature: T ₂ ) is (T ₁ + 5) -
It is recommended to select from the range of (T ₁ +40)°C. Also,
The stretching ratio is preferably selected from a range in which the uniaxial stretching ratio is 2.5 times or more, particularly 3 times or more, and the area magnification is 8 times or more, especially 10 times or more. Furthermore, the heat setting temperature is preferably selected from the range of 180 to 250°C, more preferably 200 to 230°C. The biaxially oriented polyester film of the present invention has an extremely small number of voids compared to conventional films. The reason why the voids around these spherical silica particles are small is that the particles have a good affinity for polyester, and the particles themselves are very close to true spheres, so the stress around the particles propagates evenly during stretching, and the polyester This is presumed to be due to the fact that stress is not concentrated on a part of the particle interface. In the present invention, by adding spherical silica particles whose particle size distribution is extremely sharp, the distribution of protrusions formed on the surface of the polyester film is extremely uniform, and the polyester film has large and small protrusions with uniform heights. is obtained. The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness, excellent abrasion resistance, etc., and is characterized in that, for example, the amount of scratches, white powder, etc. generated is extremely small. This biaxially oriented polyester film can be widely used in various applications by taking advantage of these properties. For example, for magnetic recording such as video, audio, etc.
When used as a base film for computers, etc., excellent electromagnetic conversion characteristics, slipperiness, running durability, etc. can be obtained. Also, when used in capacitor applications,
Low friction coefficient, 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, particularly as a base film for magnetic tapes, but is not limited thereto, and can be used for electrical applications, packaging applications, films for vapor deposition, 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 of 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 a film (i) From powder On the electron microscope sample stage The powder is scattered so that the individual particles do not overlap as much as possible, and a thin gold film (200 Å to 300 Å thick) is deposited on the surface using a gold sputtering device.
Formed and observed with a scanning electron microscope at a magnification of, for example, 10,000 to 30,000 times.
Manufactured by Luzex 500, at least
Find the major axis (Dli), minor axis (Dsi), and area equivalent diameter (Di) of 100 particles. Then, the major axis (Di), minor axis (Ds), and average particle diameter ( ) of the silica particles are expressed by the number average values expressed by the following equations. Dl = ( _o 〓 ⁱ⁼¹ Dli) / n, Ds = ( _o 〓 ⁱ⁼¹ Dsi) / n, = ( _o 〓 ⁱ⁼¹ Di) / n (ii) For particles in a film A small piece of the sample film The film was fixed on a sample stage for a scanning electron microscope, and the surface of the film was subjected to ion etching using a JEOL sputtering device (JFC-1100 type ion sputtering device) under the following conditions. The conditions were to place the sample in a bell gear, increase the vacuum level to approximately 10 ^-3 Torr, and
Ion etching is 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 it was observed using a scanning electron microscope at a magnification of 10,000 to 30,000 times.
The major axis (Dli), minor axis (Dsi) and area circle equivalent diameter (Di) of at least 100 particles in Luzetx 500
seek. The following steps are performed in the same manner as in (i) above. (2) Particle size, etc. of particles other than spherical silica particles (1) Average particle size Measured using a Centrifugal Particle Size Analyzer Model CP-50 manufactured by Shimadzu Corporation. From the integrated curve of particles of each particle size and their abundance calculated based on the obtained centrifugal sedimentation curve,
The particle size corresponding to 50 mass percent is read and this value is taken as the above-mentioned average particle size (see Book "Particle Size Measurement Technique", published by Nikkan Kogyo Shimbun, 1975, pp. 242-247). (2) Particle size ratio Fixed molding of small film pieces with epoxy resin,
Create ultra-thin sections (cut parallel to the film flow direction) with a thickness of approximately 600 Å using a microtome. The cross-sectional shape of the inorganic particles in the film was observed using a transmission electron microscope (model H-800, manufactured by Hitachi, Ltd.), and was expressed as the ratio of the long axis to the short axis of the inorganic particles. (3) Relative standard deviation Measurement was carried out in the same manner as for spherical silica,
For particles other than spherical, the volume is calculated from the particle size ratio in the film thickness direction, the particle size is determined by the diameter of an equivalent sphere, and the relative standard deviation is calculated. (3) Film surface roughness (Ra) This is the value defined in JIS-B0601 as the centerline 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 digit after the decimal point, and display it to the third digit after the decimal point. (4) Film friction coefficient (μk) In an environment with a temperature of 20℃ and a humidity of 60%, a film cut to a width of 1/2 inch was held with a fixed rod (surface roughness 0.3μ
m) angle θ = (152/180) π radian (152°)
make contact with each other and move (friction) at a speed of 200 cm/min. When the tension controller is adjusted so that the entrance tension T ₁ is 30 g, the exit tension (T ₂ : g) is detected by the exit tension detector after the film has traveled 100 m, and the running friction coefficient μk is calculated using the following formula. calculate. μk=(2.303/θ)log(T ₂ /T ₁ ) =0.868log(T ₂ /30) (5) Abrasion resistance Evaluate the abrasion resistance of the running surface of the base film using a 5-stage mini super calendar. . The calendar is a 5-stage calendar made of nylon rolls and steel rolls, the processing temperature is 80℃, the linear pressure applied to the film is 180Kg/cm, and the film speed is 45.
Run at m/min. The total length of the running film is 2500m.
The abrasion resistance of the base film is evaluated based on the dirt that adheres to the top roller of the calendar during running. <Four-level judgment> ◎ No stains on the nylon roll ○ Almost no stains on the nylon roll × × Nylon roll gets dirty ×× Nylon roll gets very dirty (6) Scratch Judgment A film cut to a width of 1/2 inch was scratched using the above (4) )
The surface of the 1/2 inch wide base film was measured using a friction coefficient measuring device of The thickness, depth, and number of the scratches entered are taken into account and judged in the following five stages. <5-level judgment> ◎ No scratches are observed on the 1/2 inch wide base film ○ Almost no scratches are observed on the 1/2 inch wide base film △ Scratches are observed on the 1/2 inch wide base film (no scratches are observed on the 1/2 inch wide base film) × Several thick scratches are observed on the 1/2 inch wide base film × × Many thick and deep scratches are observed all over the 1/2 inch wide base film (7) Windability Biaxially oriented polyester film In the manufacturing process, the film is rolled up into a 4000m roll with a width of 500mm, the appearance of this roll is inspected in detail, the number of bump-like protrusions with a major diameter of 2mm or more is counted, and the film is graded as follows. 0-2: ○ 3-5: △ 6 or more: × Examples 1-3 and Comparative Examples 1-4 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, stabilizer Using phosphorous acid as a lubricant and inorganic particles shown in Table 1 as a lubricant, polymerization was carried out in a conventional manner to obtain polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35°C) of 0.62. This polyethylene terephthalate pellet
After drying at 170℃ for 3 hours, feed it to the extruder hopper.
The molten polymer is melted at a melting temperature of 280 to 300°C and passed through a slit die with a spacing of 1 mm for surface finishing.
The film was formed and extruded on a rotating cooling drum at a temperature of about 0.3S and a surface temperature of 20°C to obtain an unstretched film of 180 μm. The unstretched film thus obtained was heated at 75°C.
The material is then preheated with a single IR heater with a surface temperature of 900°C from 15 mm above between low and high speed rolls, stretched 3.7 times in the longitudinal direction due to the difference in surface speed between the low and high speed rolls, and then rapidly cooled. Then, it was supplied to a stenter and stretched 4.0 times in the transverse direction at 105°C. The obtained biaxially stretched film was heat set at a temperature of 210° C. for 5 seconds to obtain a heat set biaxially oriented film having a thickness of 12 μm. The properties of this film are shown in Table 1.

【table】

[Table] From Table 1, Comparative Example 1 is unsatisfactory in scrapability and rollability, Comparative Example 2 is unsatisfactory in slipperiness, scratchability, and rollability, and Comparative Example 3 is unsatisfactory in slipperiness and scratchability. It is clear that Comparative Example 4 was unsatisfactory in slip properties, abrasion properties, and scratch properties, and Examples 1, 2, and 3 all produced films of satisfactory quality. Example 4 A biaxially oriented film was obtained in the same manner as in Comparative Example 1 except that the lubricant listed in Table 2 was used. This film had good surface flatness and runnability, and was particularly excellent in abrasion resistance, scratch resistance, and rollability. The properties of this film are shown in Table 2.

【table】

【table】

Claims (1)

[Claims] 1. In the polyester, as a first component, the average particle size is 0.3 μm or more and less than 0.6 μm, and the particle size ratio (longer diameter /
Spherical silica particles with a short axis) of 1.0 to 1.2 and a relative standard deviation of 0.5 or less expressed by the following formula are used.
Contains in a range of more than 0.5% by weight and 2.5% by weight or less, and has an average particle size of 0.6 to 3.0 μm as a second component
The first component contains spherical silica particles having a particle diameter ratio (major axis/minor axis) of 1.0 to 1.2 and a relative standard deviation of 0.5 or less expressed by the following formula in a range of 0.005 to 2% by weight. A biaxially oriented polyester film characterized in that it contains an amount of not more than . Here, Di: Area circle equivalent diameter of each particle (μm): Average value of area circle equivalent diameter (= _o 〓 ⁱ⁼¹ Di/n) (μm) n: Represents the number of particles.