JPH02129232A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented polyester film with excellent scratch resistance and shaving resistance of the film surface by using a specified amt. of rutile titanium dioxide particles with a specified particle shape. CONSTITUTION:This biaxially oriented polyester film contains 0.05-5wt.% rutile titanium dioxide particle with an average particle diameter of 0.05-2mum and a sphericity coefficient of 0.8-1. It is pref. that the degree of flatness of the surface projection of said polyester film is 7-16, because the scratch resistance and shaving resistance are improved thereby. It is pref. that ethylene terephthalate is a main constituting component as the polyester film, because the slipperiness, scratch resistance and shaving resistance of the film are further improved thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to biaxially oriented polyester films.

[Prior Art] As a biaxially oriented polyester film, a film in which anatase type titanium dioxide is contained in polyester is known (for example, JP-A-59-178224).

[Problem H to be solved by the invention] However, the above conventional biaxially oriented polyester film has the following problems:
As the speed of film processing processes, such as the printing process for packaging applications and the magnetic layer coating/calendering process for magnetic media applications, increases, (1) the surface of the film is easily scratched by contacting rolls, etc. (2) Recently, there has been a problem in that the surface of the film is scraped and powder is deposited on the roll, which causes problems in the processing process and product performance.

The present invention solves these problems, namely, (1) the film surface is easily scratched due to contact as the process speed increases, and (2) powder is deposited on the roll due to the film surface being scraped. The purpose is to solve this problem and provide a film with excellent surface scratch resistance and abrasion resistance.

[Means for Solving the Problems] The present invention provides 0.05 to 5% by weight of rutile titanium dioxide.
A polyester film containing titanium dioxide having an average particle size of 0.05 to 2 μm and a sphericity coefficient of 0.05 to 2 μm.
8 to 1.

The polyester in the present invention includes ethylene terephthalate, ethylene α, β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylate, ethylene 2.6
- Contains at least one structural unit selected from naphthalate units as a main constituent. However, other components may be copolymerized within a range that does not impede the present invention, preferably within 15 mol%.

In addition, polyester containing ethylene terephthalate as a main component is particularly desirable because it has even better slip properties, scratch resistance, and abrasion resistance.

The titanium dioxide particles (hereinafter abbreviated as particles) in the present invention need to be of rutile type.

The anatase type is not preferred because it cannot satisfy the high level of abrasion resistance that is the objective of the present invention.

The content of particles in the present invention is 0.05 to 5% by weight, preferably 0.1 to 3% by weight. If the content is less than the above range, the scratch resistance of the film will be poor, which is not preferable. On the other hand, if the content is more than the above range, the abrasion resistance of the film will be poor, which is not preferable.

The average particle diameter of the particles in the present invention is in the range of 0.05 to 2 μm, preferably 0.1 to 1 μm.

If the average particle size is smaller than the above range, the scratch resistance of the film will be poor, which is not preferable. If the average particle size is larger than the above range, the abrasion resistance will be poor, which is not preferable.

It is necessary that the sphericity coefficient of the particles in the present invention is 0.8 to 1. If the sphericity coefficient is smaller than the above range, the scratch resistance will be poor, which is not preferable. The upper limit of the sphericity coefficient is 1, in which case the particle is a true sphere.

The surface protrusion flatness of the film in the present invention is 7 to 16
This is desirable because scratch resistance and abrasion resistance become good.

In the present invention, within the scope that does not impede the purpose of the present invention,
Inorganic particles or internally precipitated particles other than rutile titanium dioxide particles may be used in combination.

The film of the present invention has the above-mentioned composition as a main component, but other polymers may be blended within the range that does not impede the purpose of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. Inorganic or organic additives such as agents, nucleating agents, etc. may be added to the extent that they are normally added.

The film of the present invention is a film in which the above composition is biaxially oriented. An unstretched film or a -axis oriented film is not preferred because it has poor scratch resistance and abrasion resistance.

In addition, the plane orientation index representing the degree of biaxial orientation is not particularly limited, but is 0.935 to 0.975, particularly 0.94
Scratch resistance when in the range of 0 to 0.970;
This is particularly desirable because the abrasion resistance becomes even better.

It is particularly desirable for the density index of the film of the present invention to be in the range of 0.02 to 0.05, since this provides even better scratch resistance and abrasion resistance.

Further, the film of the present invention has an average surface roughness Ra in the width direction of 0.005 to 0.030 μm, particularly 0°007 to 0.0 μm.
A thickness in the range of 25 μm is particularly desirable because the scratch resistance becomes even better.

The friction coefficient μk of the film in the present invention is 0°20 to 0
．． A value in the range of 35 is particularly desirable because the scratch resistance becomes even better.

Furthermore, the surface resistivity of the film of the present invention is 1×11014
It is particularly desirable that the resistance is Ω or less because scratch resistance and abrasion resistance become even better.

Next, a method for producing the film of the present invention will be explained.

First, to add rutile titanium dioxide to a given polyester, it can be added before, during, or after polymerization, but it can be added in the form of a slurry to ethylene glycol, which is the diol component of polyester. A method of adding after dispersing is effective. Furthermore, as a method for adjusting the content of particles, it is effective to dilute a highly concentrated master pellet during film formation. Using rutile type titanium dioxide, adjust the melt viscosity and copolymerization component of high concentration, preferably 1 to 5 layered master pellets,
Difference between glass transition point Tg and cold crystallization temperature Tcc (Tcc
-Tg) at 65 to 110°C, particularly 75 to 100°C, is extremely effective.

After sufficiently drying the pellets containing a predetermined amount of inert inorganic particles, the pellets were fed to a known melt extruder and 27
It is extruded into a sheet through a slit-shaped die at 0 to 330°C, and cooled and solidified on a casting roll to produce an unstretched film.

When making this unstretched film, the draft during casting (slit width of the die/thickness of the unstretched film) is 16
Preferably, the value is at least twice as high. Since the contained particles are spherical particles, high draft casting causes a unique phenomenon in which the particles concentrate on the surface layer. Therefore, such high draft casting is particularly effective in the present invention.

Next, this unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. In the case of the sequential biaxial stretching method, it is common to stretch in the longitudinal direction and then in the width direction, but this order may be reversed. The conditions for biaxial stretching are not necessarily constant depending on the stretching method, type of polymer, etc., but usually 80 to 160 in both the longitudinal and width directions.
℃, preferably in the range of 90℃ to 150℃, and the stretching ratio is 3.0 to 5.0 times, preferably 382 to 4.
The range is 5 times, and the stretching speed is 1000-70000%
A range of /min is preferred.

Next, this stretched film is heat treated. The heat treatment conditions are preferably 150 to 230°C, preferably 170 to 220°C for 0.5 to 60 seconds under constant length and relaxation of 1 to 15%, preferably 2 to 10%.

[Method of Measuring Physical Properties and Evaluating Effects] The methods of measuring the characteristic values and evaluating the effects of the present invention are as follows.

(1) Content of inorganic fine particles (wt%) 0-chlorophenol 1, Oa in 100 g of polyester
After heating at 120°C for 3 hours, centrifugation was performed at 30°000 rpm for 40 minutes using an ultracentrifuge 55P-72 manufactured by Hitachi Koki ■, and the obtained particles were vacuum dried at 100°C. When fine particles were measured with a scanning differential caloric meter,
If a dissolution peak corresponding to the polymer is observed, 0° chlorophenol is added to the particles, and after heating and cooling, centrifugation is performed again. When the dissolution peak is no longer observed, the fine particles are considered to be precipitated particles. Normally, two centrifugation operations are sufficient. The ratio (wt%) of the thus separated particles to the total amount is defined as the content of fine particles.

(2) Average particle size of inorganic fine particles (μm) Using a Yamato Chemical plasma reactor (model PR-503), the film surface was plasma-etched with oxygen supply ff 150 cc/min and processing time 20 minutes.This sample was coated with platinum evaporation. After that, use an electron microscope at a magnification of 2000 to 5000.
The particles were observed under magnification and the short axis and long axis of the particles were measured.

(3) Spherical coefficient of inorganic particles The surface of the film was plasma etched using a Yamato Chemical plasma reactor (Model PR-503) with an oxygen supply rate of 50 cc/min and a processing time of 20 minutes. After platinum deposition, this sample was etched with electrons. The particles were observed with a microscope at a magnification of 2,000 to 5,000 times, the short axis and long axis of the particles were measured, and the average value of the ratio of the short axis to the long axis was taken as the sphericity coefficient of the fine particles.

(4) Using a scanning electron microscope [ESM-3200, manufactured by Elionix ■] with a two-detection method for surface protrusion flatness and a cross-sectional measuring device [PMS-1, manufactured by Elionix ■, the height of the smooth surface of the film surface was set to 0.
The height measurement value when scanning is sent to the image processing device [IBAS2000, manufactured by Carl Zeiss ■] as a 25656-level gray value, and based on this gray value, the IBAS2000
Reconstruct the film surface projection image on top. Next, the circular diameter was determined from the area of each protrusion obtained by lowering 10 or more gradations of this surface protrusion image by two values, and this was taken as the surface protrusion diameter. Next, determine the height of the highest value among the individual protrusions measured in the same manner.

This measurement is performed for 1 mm2, and the average values are defined as the surface protrusion diameter d and the surface height h, respectively. Using the surface protrusion diameter d and surface protrusion height h obtained by the above method, d/h is the surface protrusion flatness. Toshiba.

Note that the magnification of a scanning electron microscope is usually 3000 times, but an optimal magnification can be selected from a range of 2000 to 5000 times depending on the size of the protrusion.

(5) Planar orientation index Using an Atsube refractometer with sodium D line (wavelength 589 nm) as a light source, measure the refractive index in the thickness direction of the biaxially oriented film (denoted as A) and quench it in water at 10°C after melt pressing. The refractive index (referred to as B) in the thickness direction of the non-oriented amorphous film produced was measured, and A/B was taken as the plane orientation index. Methylene iodide was used as the mounting solution.
Measurement was performed at 25° C. and 65% RH.

(6) Glass transition point Tg, cold crystallization temperature Tcc Measured using a PerkinElmer DSC (differential scanning calorimeter) type II. The conditions for DSC are as follows. That is,
Sample 10 is set in a DSC device, melted at a temperature of 300° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. This rapidly cooled sample is heated at a rate of 10° C./min, and the glass transition point Tg is detected. The temperature was further increased, and the exothermic peak temperature of crystallization from the glass state was defined as the cold crystallization temperature Tcc.

(7) Density index The density of the film measured using a density gradient tube made of n-hebutane/carbon tetrachloride is dl (g/csi3),
This film was melt-pressed and then rapidly cooled in water at 10 DEG C. to produce a non-oriented (amorphous) film.The difference in density d2 (dl-d2) was taken as the density index.

(8) Coefficient of friction (μk) Using a tape runnability tester TBT-300 model (manufactured by Yokohama System Research New Co., Ltd.), run the tape in an atmosphere of 20°C and 60% RH, and determine the initial μk (coefficient of friction) as shown below. It was calculated from the formula.

μ = 0.733 l og (T1/To) where To is the inlet tension and T1 is the outlet tension.

The guide diameter is 6mmφ, and the guide material is 5US27 (
The surface roughness is 0.2S), and the winding angle is 180°. The running speed is 3.3cn/sec.

(9) Surface specific resistance Measured using a superinsulator meter (manufactured by Tsukihi Denki Seisakusho ■) model VE-40.

<10) The scratch-resistant film was slit into a tape with a width of 1/2 inch, and the film was slit into a tape with a tension of 300 g and a running speed of 200 m/min. The wrapping was run at an angle of 90° on a stainless steel guide bottle, and the amount of scratches created at that time was visually judged according to the following criteria.

Items with no scratches: 5 points Items with shallow scratches: 3 points Items with deep scratches: 1 point In addition, the points between 5 and 3 points are 4 points and 3 points. The middle point of 1 point is 2
It was marked as a point. At this time, 3 points or more indicates good scratch resistance.
A value less than a point was considered poor scratch resistance. Judgment at this time was 3
If the film is below the point, the surface of the film will be abraded and deep scratches will occur during processing or during running when it is made into a product, resulting in significantly poor quality of the product.

01) Press one blade perpendicularly against a tape-like slit of abrasion-resistant film 1/2 inch wide, press it further by 0°5++ un, and run it for 20 am (running tension crab 500g)
, running speed: 6.7 cn/sec). At this time, the height of the scraped material on the film surface attached to the tip of the single blade was read using a microscope.
The unit for the amount of abrasion is μm. If the average value of the amount of abrasion on both sides is 5 μm or less, the abrasion resistance is very good, 5 to 7
If it was μm, it was determined that the abrasion resistance was good, and if it exceeded 7 μm, it was determined that the abrasion resistance was poor. This value of 7 μm is a critical point for strictly determining whether or not troubles in the process and product performance will occur due to scraping of the film surface during processing steps such as the printing process and the calendering process.

[Example] The present invention will be explained based on examples.

Example 1 Rutile-type titanium oxide with an average particle size of 0.3 μm and a sphericity coefficient of 0.95 was uniformly dispersed in 2% by weight ethylene glycol, heat-treated at 195°C for 2 hours, and then polymerized with dimethyl terephthalate to form particles. Particle master pellets of polyethylene terephthalate containing 2% by weight of This particle master pellet and pellets of polyethylene terephthalate containing no particles were mixed so that the particle content was a predetermined amount, and the pellet was dried under reduced pressure (3 Torr) at 180° C. for 3 hours. The pellets were supplied to an extruder, melt-extruded at 290°C, wound around a casting drum with a surface temperature of 30°C using an electrostatic casting method, and cooled and solidified to produce an unstretched film with a thickness of approximately 180 μm. . The draft ratio at this time was 22.

This unstretched film was stretched 3° to 4 times in the longitudinal direction at 90°C. This -axis film was heated to 100°C using a stenter.
The film was stretched 3.6 times in the width direction and heat treated at 210° C. for 5 seconds under constant length to obtain a biaxially oriented film with a thickness of 15 μm.

This film had a planar orientation index of 0.950 and a density index of 0.03.

Moreover, the surface average roughness Ra of this film is 0.0155μ
m, and the friction coefficient μ was 0.22.

The surface protrusion flatness of this film was 11.

Next, the scratch resistance of this film was measured and was found to be 5 points, which was very good. Also, when measuring the abrasion resistance, 3
．． It was 0 μm, which was very good. (Table 1).

Examples 2-3. Comparative Examples 1 to 5 Biaxially oriented films of polyethylene terephthalate were prepared in the same manner as in Example 1 by changing the type of particles contained, average particle diameter, content, sphericity coefficient of particles, film forming conditions, etc. Those whose contained particles, particle sphericity coefficient, draft ratio, and surface protrusion flatness were all within the range of the present invention had good scratch resistance and cracking resistance. (Examples 2-4).

However, when any of the particle type, average particle size, content, and particle sphericity coefficient is outside the scope of the present invention, it was not possible to satisfy both scratch resistance and abrasion resistance (Comparative Example 1). ~7).

[Effects of the Invention] The present invention uses rutile-type titanium dioxide particles to produce a biaxially oriented polyester film whose average particle diameter, content, and sphericity coefficient are set within specific ranges, so while maintaining slipperiness,
Scratch resistance that can withstand today's harsh usage conditions,
A film with excellent abrasion resistance was obtained.

Although the use of the film of the present invention is not particularly limited, (1) the film surface is damaged during the processing process. ■The film surface can be scraped. This is particularly useful as a base film for magnetic recording media, which has a particularly large influence on product performance.

Claims (2)

[Claims] (1) 0.05 to 5% by weight of rutile titanium dioxide particles
A biaxially oriented polyester film comprising titanium dioxide particles, wherein the titanium dioxide particles have an average particle size of 0.05 to 2 μm and a sphericity coefficient of 0.8 to 1. (2) The biaxially oriented polyester film according to claim 1, wherein the film has a surface projection flatness of 7 to 16.