JPS63221133A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented polyester film which is flat and excels in lubricity, chipping resistance, etc., by dispersing two kinds of spherical silica particles each of which is specified in the average particle diameter, particle diameter ratio and amount of addition in a polyester. CONSTITUTION:First spherical silica particles having an average particle diameter of 0.6-3mum and a particle diameter ratio (major diameter/minor diameter) of 1-1.2 and second spherical silica particles having an average particle diameter of 0.7-3.1mum and a particle diameter ratio of 1-1.2 are prepared. 0.001-2.5wt.% first spherical silica particles and 0.001-2wt.% second spherical silica particles are dispersed in a polyester (e.g., polyethylene terephthalate). This polyester is formed into a film, which is biaxially oriented to obtain a biaxially oriented polyester film. This film can be suitably used as a base film for videotapes, computer tapes, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a biaxially oriented polyester film, and more specifically, the present invention relates to a biaxially oriented polyester film, which contains spherical silica particles with different average particle diameters, is flat, and has excellent sliding properties, abrasion resistance, etc. Concerning an excellent biaxially oriented polyester film.

[Prior Art] Polyester films, represented by polyethylene terephthalate films, have excellent physical properties.

Because of its chemical and chemical properties, it is used in a wide range of applications, such as magnetic tape, capacitors, photography, and packaging.

01-11) etc.

In polyester films, their slipperiness and abrasion resistance are major factors that determine the workability of the film manufacturing process and processing process for each application, as well as the quality of the product.

In particular, when a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, the friction and abrasion between the coating roll and the film surface during application of the magnetic layer is extremely severe, causing wrinkles and scratches on the film surface. It's easy to do. In addition, audio can be produced by slitting the film after applying the magnetic layer.

Even after processing video or computer tape, there are many guide parts that can be used to pull out reels, cassettes, etc., and to wind up the tape.

Significant wear occurs between the playback head, etc., resulting in scratches.

The occurrence of distortion and the precipitation of white powdery substances due to scratches on the surface of the polyester film are often a major cause of missing magnetic recording signals, that is, dropouts.

In general, to improve the slipperiness and abrasion resistance of films, methods are used to reduce the contact area between guide rolls, etc. by adding irregularities to the film surface. Two methods are used: one is to precipitate inactive particles from the catalyst residue of the polymer used, and the other is (ii) to add inactive inorganic particles. The larger the fine particles in these raw material polymers, the more
Generally, it has a great effect on improving slipperiness, but for precision applications such as magnetic tape, especially video, the large particles themselves 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 are demands to satisfy contradictory characteristics at the same time.

[Purpose of the Invention] The present inventor has solved these disadvantages, reduced the voids around the particles, and roughened the film surface appropriately, thereby improving the slipperiness and abrasion resistance of the film. 1 biaxially oriented polyester film with suitable surface properties.
Especially for videotapes, audiotapes,
As a result of intensive research in order to obtain a polyester film for magnetic tapes such as computer tapes, we found that by sharpening the shape of the protrusions on the film surface and using a specific combination of large particles and small particles, even if the film surface is flat, it can improve slipperiness. The abrasion resistance is greatly improved, and in order to sharpen the shape of the protrusions, it is most preferable that the particles present in the film be spherical.There are many particles that are close to spherical, including glass peas. It is difficult to obtain a film that satisfies the surface properties for magnetic tapes, but if specific spherical silica particles are used in combination with large particles and small particles, it is possible to produce a film that satisfies the above properties. The present invention has been achieved based on the discovery that the present invention can be obtained.

Therefore, 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, and the like.

[Configuration/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 0.6 to 3 μm as a first component and a particle diameter (longer axis/breadth axis) of 1.0 μm. Contains o, ooi ~ 2.5% by weight of spherical silica particles having a particle size of 0 to 1.2, and has an average particle size of 0.7 to 3.1 μm as a second component, and has a particle size ratio (major axis/breadth axis ) or 1.0 to 1.2% by weight of spherical silica particles.

The poly-1 stell in the present invention is a poly-1 stell having aromatic dicarphonic acid as the main acid component and aliphatic glycol as the main glycol component.

Such polyesters are substantially linear and have film forming properties, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid,
Naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid.

Diphenyl dicarboxylic acid, Schiff T'yl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid.

Examples include diphenylketone dicarboxylic acid and the like. Examples of aliphatic glycols include polysaccharides having 2 to 10 carbon atoms such as ethylene glycol, 1-rimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol. Examples include alicyclic diols such as methylene glycol and cyclo l-xane dimetatool.

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 and polyethylene-2,6-naphthalate are of course b, and for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and/or 2,6-naphthalene dicarboxylic acid. Therefore, a copolymer in which 80 mol% or more of the total glycol component is ethylene glycol is preferred. In this case, 20-syl% or less dicarboxylic acid in the aromatic acid component may be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and/or 2,6-naphthalene dicarboxylic acid, such as adipic acid, cepatic acid, etc. Aliphatic dicarboxylic acids; alicyclic hx dicarboxylic acids such as cyclohexane-1,4-dicarboxylic acid; and the like. In addition, 20 mol% or less of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or, for example, hydroquinone, resorcinol, 2,2-his(4
-Aromatic groups such as (hydroxyphenyl)propane etc.
Aromatic compounds such as 1,4-dihydroxymebupensen
Aliphatic diols containing t; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. can also be used.

Furthermore, in the polyester used in the present invention, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid, an aliphatic oxyacid such as ω-hydroxycaproic acid, a cycarphonic acid component and an oxycarphonic acid component, Those copolymerized or combined in an amount of 20 mol % or less based on the total amount of components are included.

Furthermore, the polyester of the present invention contains a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound, such as trimellitic acid, pentamellitic acid, etc. It also includes those copolymerized with erythritol.

The polyesters mentioned above are known per se and can be prepared in a manner known per se.

The polyester has an intrinsic viscosity of approximately 0, measured as a solution in 0-chlorophenol at 35°C.
．． 4 to about 0.9 is preferred.

The biaxially oriented polyester film of the present invention has many fine protrusions on its surface.

According to the present invention, each of the large number of fine protrusions is derived from a large number of spherical silica particles dispersed and contained in the polyester.

Polyester containing such spherical silica particles dispersed therein is
Usually, spherical silica particles (preferably (as a slurry in glycol) into the reaction system. Preferably, the 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 the polyester have a particle size ratio (major axis/minor axis) of 1.0 to 1.2, preferably 1.0 to 1.15, more preferably 1.0 to 1.
．． 1, and its individual shape is extremely similar to that of a pearl. The spherical silica particles have an average particle diameter of 0.6 to 3 μm, preferably 0.6 to 2 μm, and more preferably 0.6 to 1.5 μm. 7-3.1 μm, preferably 0.7-2.1
μm1 More preferably 0.7 to 1.6 μm (second
There are two types.

Such spherical silica particles are made of silica particles conventionally known as lubricants, which are ultrafine lumpy particles of Ion μm culm, or aggregated to form aggregates (agglomerated particles) of about 0.5 μm. It is characterized by a remarkable difference.

If the average particle diameter of the spherical silica particles as the first component exceeds 3 μm, the surface flatness will be insufficient, which is not preferable.

Furthermore, the average particle diameter of the spherical silica particles as the second component is 3.
．． If it exceeds 1 μm, the surface flatness will be insufficient, which is not preferable.

Here, the major axis and minor axis of the spherical silica particles are determined using an electron microscope, for example, after depositing metal on the particle surface.
It is determined from an image magnified 30,000 to 30,000 times, and the average particle size/particle size ratio is determined by the following formula.

Average particle diameter = Sum of area circle-equivalent diameters of measured particles / Number of particle diameter ratio of measured particles - Average major axis of silica particles / Average minor axis of the particles Also, do these spherical silica particles have a sharp particle size distribution? Preferably, the relative standard m difference representing the steepness of the distribution is 0.5 or less, more preferably 0.4 or less, particularly preferably 0.3 or less.

This relative standard deviation is expressed by the following formula.

Here, Di is the surface circle equivalent diameter of each individual particle (U), and B is the average value of the area circle equivalent diameter Σ Di (= i·1 ) (μTl1) n: represents the number of particles.

When spherical silica particles with a relative standard deviation of 0.5 or less are used, the distribution of protrusions formed on the surface of the film is extremely uniform because the particles are truly spherical and the particle size is extremely steep. A polyester film with high and uniform protrusion height and excellent slip properties can be obtained. It is preferable that there is a difference of at least 0.1 μm between the average particle size of the first component and the average particle size of the second component. Further, it is preferable that the particle sizes of the first component and the second component do not substantially overlap each other.

The spherical silica particles are not limited in any way in terms of their manufacturing method, etc., as long as they satisfy the above-mentioned conditions. For example, the spherical silica particles are made of ethyl aorthosilicate [Si (OCzHs) 4
] from hydrolysis of hydrated silica [Si(OH)4]
It is possible to make monodisperse spheres and further dehydrate these monodisperse hydrated silica spheres to grow silica bonds [=Si-Q-8i=] three-dimensionally (Journal of the Japanese Society of Science).
81. No, 9. P1503).

Si (OC2tls) 4 +4! lzo→Si (
Of-1> 4+402HsOH=Si-OH-+-IQ-8i=→ =Si-0-8i=+HzO In the present invention, the amount of spherical silica particles added as the first component in J3 is o, based on the polyester. ooi to 2.5% by weight, preferably 0.005 to 1.5% by weight, more preferably 0.01 to 0.8% by weight. Also the second
The amount of the spherical silica particles added as a component is o, ooi to 2 percent relative to the polyester, preferably 0.00.
5 to 1.5 mm%, more preferably 0.01 to 0.8φ
The amount is within the range of %. It is also preferable that the amount of the second component be less than the amount of the first component.

If the amount of the first component and the second component added is less than 0% by weight, the effect of improving slipperiness and scratch resistance will be insufficient. In addition, the total amount of the first component and the second component added is 0.01 to 2.6% by weight, more preferably 0.02 to 1.3% by weight.
It is preferably 0.04 to 0.8% by weight, particularly 0.04 to 0.8% by weight. If the total amount added is too large, the surface flatness will be poor.
Undesirable.

The biaxially oriented polyester film of the present invention can be produced in accordance with conventional methods for producing two-wheel stretched films. For example, a polyester containing a predetermined amount of spherical silica particles is melt-cast to form an amorphous unstretched film, and then the unstretched film is biaxially stretched and heat-set.
If necessary, it is manufactured by performing a relaxation heat treatment.

At that time, the film surface characteristics are determined by the particle size of the spherical silica particles,
Since the stretching conditions vary depending on the amount and the stretching strip '1, the stretching conditions are appropriately selected 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 is such that the first stage stretching temperature (e.g. longitudinal stretching temperature: T1) is (T(J-10)~(To+45>
' C range (however, Tg = glass transition temperature of polyester) to second-stage stretching g degree (for example, transverse direction stretching temperature: T
2) is preferably selected from the range of (T++5) to ('L+40)°C. 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 818 or more, particularly 10 times or more. Furthermore, the heat setting temperature is 180 to 250'C, and even 200'C.
It is preferable to select from the range of ~230'C.

The biaxially oriented polyester film of the present invention is characterized by having extremely few 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 stress not being concentrated on a part of the particle interface.

In the present invention, by adding two types of spherical silica particles, large and small, which have extremely sharp particle size distributions, the distribution of protrusions formed on the polyester film surface is extremely uniform, and the height of each large and small protrusion is A uniform polyester film is obtained.

The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness, excellent scratch 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., it provides excellent electromagnetic conversion properties, slipperiness, running durability, etc. Also, when used in capacitor applications, it has a 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, particularly as a base film for magnetic tapes, but is not limited thereto, and can be used for electrical applications, packaging applications, vapor deposition films, etc. It can be widely applied to other fields as well.

Furthermore, one or both sides of the film may be subjected to a surface treatment such as an easy-adhesion layer coating, a corona treatment, etc., and the film may also be coated with a third component such as an antistatic agent, an ultraviolet absorber, or a coloring agent. It may be included.

[Example] 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 particle size measurement.

(i) When determining the average particle size 9 particle size ratio etc. from powder (ii)
) When calculating the average particle size of particles in a film (i) When using powder, place the powder on an electron microscope sample stage so that the individual particles do not overlap as much as possible (scatter them), and use a gold sputtering device to A thin gold film vapor deposited layer (layer thickness 200 to 300 layers) is formed on the surface,
Observe with a scanning electron microscope at a magnification of 10,000 to 30,000 times, and use a Japanese regulator (Luzex).
At least 100 particles have a long diameter (Di!i
), the short axis (DSi), and the area circle equivalent diameter (Di). Then, the major axis (DI) and the minor axis (r) of the silica particles are determined by the number average value expressed by the following formula.

It represents the average particle size (?5).

D1=(ΣDli)/n.

i=1 DS=(Σ[)si)/n.

i=1 "1 σ=(Σ Di)/n i=1 (ii) For particles in a film A small piece of sample film was fixed on a scanning electron microscope sample stage and sputtered using a JEOL II sputtering device (JFC- 11
The surface of the film is subjected to ion etching using an ion sputtering device (Model 00) under the following conditions. Article A1
Place the sample in a Pelger and apply a pressure of approximately 10' Torr.
The degree of vacuum is increased to a vacuum state of 1, 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 is applied to the surface of the film using the same equipment, and the film is observed using a scanning electron microscope at a magnification of, for example, 10,000 to 30,000 times, and the long diameter of at least 100 particles ( DJ!i).

Determine the short axis (DSi) and the area circle equivalent diameter (Di).

The following steps are performed in the same manner as in (j) above.

(2) Particle size of particles other than silica particles 1) Average particle size Centrifugal Particle Size Analyzer CP-50 model manufactured by Shimadzu Corporation (Centrifugal Particle 5)
ize Analyser)
The particle size corresponding to 50 mass percent is read from the stacking curve of particles of each particle size and their abundance based on the centrifugal sedimentation curve obtained, and this value is defined as the above average particle size (B
Ookr Particle Size Measurement Technology Published by JElIIJi Industry Newspaper.

1975, pp. 2, 242-247).

2) Particle size ratio A small piece of the film is fixed and molded using an epoxy resin, and an ultra-thin section (cut parallel to the flow direction of the film) of approximately 60 OA in size I7 is prepared using a microtome. The cross-sectional shape of the lubricant in the film was observed using a transmission electron microscope (Model H-800, manufactured by El Ritsu Seisakusho) and expressed as the ratio of the long axis to the short axis of the lubricant.

3) Relative standard deviation value Measurement is performed in the same manner as for spherical silica, and for particles other than spherical, the volume is calculated from the particle size ratio of the particles in the film thickness direction, and the particle size is determined by the diameter when equivalent spheres are obtained. , yield the relative standard deviation.

(3) The film surface roughness (Ra) is the value defined in JIS-80601 as the center line average roughness (Ra).
-30C). The measurement conditions are as follows.

(a) Stylus tip radius: 2 μm (b) Measurement pressure: 30 mg (C) Cutoff: 0.25 mm (d) Measurement length
: 2.5 mm ((3) How to summarize data - Measure the data repeatedly 5 times, and take the largest value as 1.
The average value of the remaining four data is rounded off to the fourth decimal place and displayed to the third decimal place.

(4) Film friction coefficient (μk) In an environment with a temperature of 20°C and a humidity of 60%, a film cut to a width of 172 inches was brought into contact with a fixed rod (surface roughness 0.2 μm) at an angle θ = π radian. Move (friction) at a speed of 1100 C/min. When the tension controller is adjusted so that the inlet tension T1 is 30 (J), the outlet tension (T2 2 g) is detected by the outlet tension detector after the film has traveled 90 m, and the running friction is calculated using the following formula.
9. Calculate the coefficient μk.

μk = (2,303/θ)10(1(T2/TI>
=0.73310(] (T2/30) (5) Abrasion resistance The abrasion resistance of the running surface of the film was determined by πF (i) using a 5-stage mini super calender. Yes, the processing temperature is 80℃, and the linear pressure applied to the film is 200K (
]/cm, and the film speed was 50 m/min. After running the running film for a total length of 2000 m, the abrasion resistance of the film was evaluated based on the dirt that adhered to the top roller of the calendar.

4-level judgment> ◎Nylon roll is not stained at all O Nylon roll is almost not stained × Nylon roll is stained × × Nylon roll is severely stained (6) Scratch Judgment Magnetic coating tape (172 inch liJ) was tested in (4) above. Using a friction coefficient measuring device, make sure that the base film surface of the tape is in contact with the fixed rod at an angle of 180°. Thickness of scratches on the surface of the IJ base film.

Depth and eIl are combined to determine the following five levels.

<5-level judgment> ◎ There are no scraps observed on the 172-inch wide base film. 01/2-inch “1” There are almost no scratches observed on the base film. △ Scratches are observed on the 1/2-inch wide base film (how many pieces? ) × Some thick scratches are observed on the 172 inch rlJ base film XX Many thick and deep scratches are observed on the entire surface of the 1/2 inch 1” base film Examples 1 to 3 and Comparative Examples 1 to 3 Dimethyl terephthalate and Ethylene glycol was polymerized by a conventional method using manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and inorganic particles shown in Table 1 as a lubricant, and the intrinsic viscosity ( 71 Russochlorophenol, 35°C) 0.
62 polyethylene prephthalate was obtained.

This polyethylene terephthalate pellet is 170'
C, 3 hours drying and feeding to the extruder hopper, melting temperature 2
Melt at 80-300℃ and spread the molten polymer at intervals of 1 m.
The product was formed and extruded through a 1Il slit die onto a rotating cooling drum with a surface finish of about 0.3S and a surface temperature of 20'C to obtain an unstretched film of 210 μm.

The unstretched film thus obtained was preheated at 75°C, and further heated with one IR heater with a surface temperature of 900°C from 15 mm above between the low and high speed rolls. It was stretched 3.6 times in the machine direction due to the difference in surface speed, rapidly cooled, and then fed to a stenter and stretched 3.9 times in the cross direction at 105°C. The obtained biaxially oriented film was heat set at a temperature of 210° C. for 10 seconds to obtain a heat set biaxially oriented film having a thickness of 15 μm.

The properties of this film are shown in Table 1.

From Table 1, it can be seen that the film of Comparative Example 1 has a high friction coefficient during running and poor scratch resistance, which is unsatisfactory, while the film of Comparative Example 2 has a high friction coefficient during running and produces white powder in one calendering process. In addition, the film of Comparative Example 3 had a high coefficient of friction during running, white powder was generated in one calendering process, and the scratch resistance was also unsatisfactory. As shown in Examples 1 to 3, the combination of spherical silica has a flat surface but has excellent slipperiness, abrasion resistance, and scratch resistance compared to the conventional products shown in Comparative Examples 1 to 3. It can be seen that it is an axially oriented polyester film.

Claims (1)

[Claims] 1. In the polyester, as the first component, the average particle size is 0.
6 to 3 μm and a particle size ratio (major axis/breadth axis) of 1.0 to
Contains 0.001 to 2.5% by weight of spherical silica particles having an average diameter of 1.2% and an average particle diameter of 0.7 to 3.0% as a second component.
1 μm and a particle size ratio (major axis/breadth axis) of 1.0 to 1.
A biaxially oriented polyester film containing 0.001 to 2% by weight of spherical silica particles. 2. The biaxially oriented polyester film according to claim 1, wherein the spherical silica particles have a relative standard deviation expressed by the following formula of 0.5 or less. Relative standard deviation = ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Where, Di: Area circle equivalent diameter of individual particles (μm) @D
@: Average value of area circle equivalent diameter ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ (μm) n: Represents the number of particles.