JPH02214736A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To provide the subject film containing specific amounts of two specific kinds of particles, having excellent scratch resistance and abrasion resistance and suitable as a base film for magnetic tape, packaging film and film for various industrial materials. CONSTITUTION:The objective film contains two kinds of particles A and B. The particle A has an average particle diameter of 5-300nm and its content in the film is 0.1-2wt.%. The particle B has an average particle diameter of 30-2,000nm and its content in the film is 0.005-0.5wt.%. The concentration of the particle A in the vicinity of the particle B is higher than the concentration in the other region. The surface resistivity of the film is preferably <1X10<15>OMEGA.cm.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a biaxially oriented polyester film, and particularly to a biaxially oriented polyester film that is suitable for use as a film for magnetic tapes, packaging, and various industrial materials, and has excellent scratch resistance and resistance. This invention relates to a biaxially oriented polyester film with excellent abrasion resistance.

[Prior Art] Previously, the present applicant used base films for packaging, capacitors, or magnetic tapes with average particle diameters of O, OS~
A biaxially oriented polyester film containing particles with a diameter of 2.0 μm and a Mohs hardness of 7 or more has been proposed (Japanese Patent Laid-Open No. 6
3-230741! Public bulletin).

In this film, by incorporating hard particles, the abrasion resistance of the film surface is improved, and by making the particle size of the particles relatively large, the film has good properties during film processing and when used as a product. We try to ensure slipperiness and running properties. , -m=[Problem to be Solved by the Invention] However, polyester films, especially biaxially oriented polyester films used as base films for magnetic tapes and packaging films that require high mechanical properties, have even higher Abrasion resistance and scratch resistance with excellent roughness have been required, and
The film proposed in Publication No. 1 was still insufficient.

For example, as the speed of various processes increases, there is a growing demand for high scratch resistance that will not damage the film surface even if it comes into contact with various high-speed mortars during the process.
If only one type of hard particles with a relatively large particle size were included as in the proposed film mentioned above, the hardness and abrasion resistance would be improved in the areas where the particles protrude like protrusions on the film surface. 1. The background of the film (
Since the surface (other than the protrusions) itself is not reinforced, there is a risk of scratches on this bare surface.

In addition, as a result of not reinforcing the background part, the retention force of the particles on the film surface part, which are used to improve wear resistance, is not sufficient, and there is a risk that the particulate parts will be scraped off as film powder by external forces received from contacting rolls, etc. When this scraping occurs, it adheres to the roll surface, etc., and the film surface is further damaged by the deposits, and the film powder that falls off becomes foreign matter, which may cause disturbances in various processing steps or damage the product itself. There is a risk that performance may deteriorate.

In view of the above-mentioned problems, the present invention aims to further improve the surface scratch resistance and abrasion resistance against abrasion and the like of a two-wheel oriented polyester film.

[Means for Solving the Problem] The biaxially oriented polyester film of the present invention that meets this objective contains two types of particles A and B, and the particles A have an average particle size of 5 to 3001 m and a content of 0. .1 to 2% by weight,
Particles B have an average particle diameter of 300 to 2000 nm, a content of o, oos to 0.5% by weight, and the concentration of particles A in the region near the particles B is higher than the concentration in other regions. .

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, the component may be copolymerized within a range that does not impede the present invention, preferably within 15 mol%.

Further, polyester containing ethylene terephthalate as a main component is particularly desirable because it has better scratch resistance.

The film of the present invention contains two types of particles A and B.

Particle A is a particle with a relatively small average particle size, and mainly reinforces the background part of the film, but in order to enhance this background reinforcement effect, particles with high hardness or particles with good affinity with the film are selected. be done. As particles with high hardness, particles made of δ-alumina, titania sol, and titanium nitride are preferable, and as particles with good affinity, organic particles can be mentioned. However, as the material for the particles,
Not limited to these.

Examples of the organic particles include crosslinked styrene-divinylbenzene copolymer particles, silicon particles, polyimide particles,
Examples include crosslinked polyester particles, Teflon particles, crosslinked polyethersulfone particles, and among them, crosslinked polymer particles such as crosslinked spherical styrene-divinylbenzene copolymer particles are preferred.

The polyester film of the present invention has a polymer cross sectionff1ff1
When using combined particles, the degree of crosslinking of the crosslinked polymer particles is desirably 25% or more, preferably 35% or more.

The crystallization promotion coefficient of the inert particles contained in the polynisder film of the present invention is preferably in the range of -5 to +10°C.

The elastic modulus of the organic particles is not particularly limited, but is 40 to 50.
00Kg/Wn2 Preferably 100-200K'
The range is preferably J/mm2.

In addition, the heat resistance of organic particles is 300℃ under nitrogen atmosphere,
Preferably, the weight loss rate in 2 hours is less than 5%.

Further, it is preferable that the organic particles do not substantially react with the polyester. Substantially unreactive particles are particles that do not cause a chemical reaction with polynisdel when contained in polyester, and do not have chemical bonds such as covalent bonds or ionic bonds between the particles and the polyester. Indicates particles. When the particles and polyester react, it is not preferable because the agglomeration of the particles increases, resulting in coarse particles and poor abrasion resistance.

Further, it is preferable to add a dispersant together with the particles in order to prevent particle agglomeration and further improve the abrasion resistance.

Moreover, the particles A are relatively small particles with an average particle diameter d1 of 5 to 300 nlll. If the average particle size is smaller than this range, the reinforcing effect of the film background will be weakened and the scratch resistance will be poor, which is not preferable.

In addition, if the average particle size is larger than the above range, the particle distribution will become too coarse, the film background reinforcing effect will be weakened, and the particle B
Alternatively, the strength for holding the film surface protrusions formed by the particles B is reduced, and the particles B or the film surface protrusions caused by them are likely to be scraped. Furthermore, the chances of the protrusions on the film surface themselves being scraped by the particles A increase, which is not preferable.

Further, the content of particles A is adjusted to a range of 0.1 to 2.0% by weight. If the amount is less than this range, the effect of reinforcing the film background due to the inclusion of Particle A will be weakened, and desired scratch resistance will not be obtained. If the amount is more than this range, there is a risk that the content will be too large and the structure may become brittle, and the white of the film may be easily scraped off or the contained particles may easily fall off, which is not preferable.

Particle B is a particle having a larger average particle size than particle A,
The film surface protrusions formed by particles B increase the roughness of the film surface and lower the coefficient of friction on the surface, improving scratch resistance and making it easier to contact other surfaces such as O-ru during processing. The purpose of this technique is to reduce the resistance at the time of contact and make it difficult for the film surface to be scraped off. In addition, in order to improve the abrasion resistance, it is preferable to use a material that has good affinity with the film. Examples of materials for particles B that can achieve these goals include silica, calcium carbonate, and organic materials, and the same materials as those for particles A described above can be used for organic particles. However, the material of the particles B is not particularly limited to those mentioned above.

In addition, the particles B have an average particle diameter d2 of 300 to 20,000 m.
These are relatively large particles, and are set larger than the average particle diameter d1 of particles A. Since the particles B are relatively large particles, the height of the film surface protrusions formed by the particles can be made higher than that by the particles A, and the surface roughness of the portions can be made rougher. When the grain size becomes rough, the coefficient of friction can be reduced, resulting in better scratch resistance on the film surface. However, if the average particle diameter d2 is smaller than the above range, the effect of roughening the film surface will be reduced, and its weight scratch resistance will be improved. This is not preferable because it makes the condition worse.

On the other hand, if it is larger than the above range, the particles B themselves or the surface protrusions formed by the particles B will be scraped off, which is not preferable.

The content of particles B is adjusted to a range of o, oos to 0.5%. If the amount is less than this range, the effect of reducing the coefficient of friction due to the inclusion of particles B will be weakened, making it impossible to obtain desired scratch resistance. Conversely, if the amount exceeds the above range, particles A
Particle B, which supports the film background part reinforced by
Alternatively, the number of protrusions on the film surface caused by the particles B becomes too large, making it easy to be scraped off, which is not preferable.

In the film of the present invention, the concentration of particles A in the region near particles B is higher than the concentration in the region (hereinafter sometimes referred to as bulk region). That is, particles A are unevenly distributed around particles B with respect to the bulk region, and particles A with a small average particle size are aggregated around particles B with a large average particle size. The degree of uneven distribution of particles A and the definition of the vicinity area of particles B will be described later. Because particles A are unevenly distributed in the vicinity of particles B, the effect of reinforcing the film background by particles A is particularly enhanced around particles 8, compared to when particles A are uniformly dispersed, and the reinforced The holding strength of the particles B is increased by the film background and the surrounding particles themselves. As a result, the particles B or the protrusions on the film surface formed by the particles B are less likely to be scraped, and the scratch resistance is also improved at the same time since these portions are less likely to become a starting point for scratches.

The film of the present invention has the above-mentioned composition as its main component, but other types of volima 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 additives 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. For unstretched films and -axially oriented films,
This is not preferable because the scratch resistance becomes poor and the particles or film surface protrusions formed by the particles tend to fall off.

In addition, the plane orientation index representing the degree of biaxial orientation is not particularly limited, but scratch resistance and wear resistance are improved when it is in the range of 0.935 to (), 975, especially 0°940 to 0.970. This is desirable because it provides even better results. Also,
It is particularly desirable that the polishing index of the film of the present invention 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 tlm, particularly 0.007 to 0.
．． A thickness in the range of 0.025 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 1×1015Ω・
It is particularly desirable that the value is smaller than α because scratch resistance and wear resistance become even better. If the film powder exceeds this value, it is not preferable because if the film powder is scraped off, the film powder tends to become agglomerated due to static electricity, etc., and the agglomerated film powder tends to damage the film surface.

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

First, as a method for incorporating particles A and B into a given polyester, it is possible to add them before, during, or after polymerization, but in particular, before polymerization of polyester, that is, as a diol component of polyester. A preferred method is to mix and disperse the compound in a slurry, such as ethylene glycol, and then add the compound.

In particular, mixing two types of particles is at the slurry stage.
Alternatively, the stage immediately after the transesterification reaction is particularly effective for increasing the degree of agglomeration (degree of maldistribution) around the particles within the range of the present invention, that is, the concentration of particles A in the region near the particles B is higher than the concentration in the bulk region. It is.

Further, at this time, it is preferable to disperse the particles by a media dispersion method in which fine glass beads or the like are dispersed as a media and then the glass beads are removed. Furthermore, a method of heat-treating the particles at the stage of forming the ethylene glycol slurry is also particularly effective in bringing the degree of agglomeration around the particles within the range of the present invention.

Further, as a method for adjusting the content of particles, a method of diluting a highly concentrated master pellet during film formation is particularly effective in controlling the degree of agglomeration around the particles within the range of the present invention.

Thus, the high-concentration master pellets and pellets not containing particles A1B are mixed, and the polyester pellets containing particles A1B at a predetermined concentration are sufficiently dried, and then supplied to a known melt extruder and heated at 270°C to 330°C. The film is then extruded into a sheet through a slit die, cooled and assimilated on a casting roll to form an unstretched film. When producing this unstretched film, the draft ratio (slit width of die/thickness of unstretched film) during casting is preferably a high value of 16 times or more. When high draft casting is performed, a unique dyeing occurs in which the particles are concentrated on the surface layer, making it easier for particles A and B to perform their intended functions. It is particularly effective in

Next, this unstretched film is stretched twice to make it biaxially oriented. As the stretching method, a sequential two-wheel stretching method or a simultaneous two-wheel stretching method can be used. In the case of the sequential biaxial stretching method, it is common to stretch in the order of the hand force direction and the width direction, but this order may be reversed. The conditions for two-wheel stretching are not necessarily constant depending on the stretching method, type of polymer, etc., but are usually 80 to 1 in both the longitudinal and width directions.
At 60°C, preferably in the range of 90 to 150°C, the stretching ratio is 3° to 5.0 times, preferably 3.2 to 4.
The range is 5 times, and the stretching speed is 1000 to 70,000.
A range of %/min is preferred.

Next, this stretched film is heat treated. The heat treatment conditions are 1 to 15%, preferably 2 to 10% in the constant length and width direction.
under relaxation of
0°C1 preferably 0.5 in the range of 170-220°C
~60 seconds is suitable.

[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) Particle content (weight %) 1J of polyester is incinerated with a plasma device, and the amount of each element in the polyester is determined using an atomic absorption spectrometer (for example, AA-680 model manufactured by Shimadzu Corporation). The amount of particles consisting of the element is determined as a percentage by weight by checking the molecular weight of the particles.The chemical composition of the particles can be determined by a method such as Xa diffraction.

Furthermore, if necessary, a constant value can be determined using fluorescent X-ray analysis, pyrolysis gas chromatography, infrared absorption, Raman scattering, or the like.

(2) Average particle diameter of particles (nm) The film containing the particles was cut into ultrathin sections perpendicular to the plane of the film to a thickness of 100 mm, and sliced using a transmission electron microscope (for example, JEOL JEH-1200EX, etc.). The particles were observed, and the average value for the 100 pA field was taken as the average particle diameter. However, the average particle size herein refers to the average particle size of primary particles, and is determined from the effective diameter of each primary particle even when the particles are in an agglomerated state.

(3) Degree of uneven distribution of particles A The film containing the particles was cut into ultrathin sections perpendicular to the film surface to a thickness of 1000 mm, and observed at a magnification of about 20,000 to 100,000 times using a transmission electron microscope. Shape. In the above photograph, particles with a primary particle size of 0.3μ7n or more are defined as particles B, and -
Particles having a secondary particle size of less than 0.3μ7n are designated as A. Further, here, a region within 0.2 μm from the interface between particle B and polyester to the polyester side is defined as a region near particle B.

In this transmission electron micrograph, the number of primary particles of particle A existing in the vicinity of particle B was counted, and the number of primary particles shaved by the area of the vicinity (μm'') was expressed as N (particles/μ7rt2).
). Further, the number of primary particles of particle A existing in 1 μTrL at a place 0.2 μ7n or more away from particle B is Nm. This measurement is performed for 100 fields of view,
Let the average values be NK and NM, respectively, and let NK/NM be the degree of uneven distribution of particles A.

Therefore, the fact that the concentration of particles A in the region near particle B is higher than 81 degrees in other regions (bulk region) means that the degree of uneven distribution>1 according to the above definition.This degree of uneven distribution is preferably 2. More preferably, it is larger than 3, and more preferably larger than 3.

Incidentally, the type of particles can also be confirmed by TEX-XMA.

(4) Planar orientation index sodium D line (wavelength 589 nm) Using Atsube's refractive index W1 as a light source, determine 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 made by Measured at R11.

(5) Density index The density of the film measured using a density gradient tube made of n-hebutane/carbon tetrachloride is ρ1 (g/cIIt),
After melt-pressing this film, the difference (ρ1-ρ2) from the density ρ2 of a non-oriented (amorphous) film made by rapidly cooling it in water at 10° C. was determined to be the density [a index].

(6) Tape runability test for friction coefficient μ Using a 1ff TBT-300 model [manufactured by Yokohama System Research Institute Co., Ltd.], run in an atmosphere of 20°C and 60% RH, and calculate the initial μk (friction coefficient) using the following formula. I asked for more.

μ = 0.733 +oo (T-1/1'0 > Here, To is the inlet tension, T1 is the outlet tension. The guide diameter is 6#Φ, and the guide material is 5US27 (surface roughness 0.28), wrapping angle is 180°, running speed is 3.3c
m/sec.

(7) Surface specific resistance Super insulation correction [manufactured by Kawaguchi Electric Seisakusho Co., Ltd.] Measured using VE-40 model.

(8) Scratch resistance 7 7 Driving test! 1iHJt T B T-300D
/ Using the T-1 model [Yokohama System Research Institute Co., Ltd.], slit the film into a tape shape with a width of 1/2 inch.
At a tension of 3JJ and a running speed of 2501n/min, the video cassette tape guide pin (surface roughness Rt is 2500nm)
The test piece was run for 60 m at a wrapping angle of 60° on a stainless steel guide bottle (with a surface of about 100 degrees), and the scratches formed during the run were visually judged according to the following criteria.

Items with no scratches at all...5 points Items with shallow scratches...3 points Items with deep scratches...・・・・・・・・・1 point and 5
The middle point between points and three points was set as 4 points, and the middle point between 3 points and 1 point was set as 2 points. At this time, a score of 3 or more was considered good scratch resistance, and a score of less than 3 was considered poor scratch resistance.

If the film scores less than 3 points at this time, the quality of the product will be significantly poor because the surface of the film will be abraded and deep scratches will occur during processing or during running when the film is made into a product.

(9) Press one blade perpendicularly against a 1/2 inch wide tape-shaped slit of the abrasion-resistant film, push it further by 0.5 mm, and run it for 20 cm (running tension = 500 g, running speed: 6. 7cm/sec). At this time, the height of the scraped material on the surface of the film attached to the tip of the single blade was read using a microscope, and the scraped amount was determined (unit: μm).The average value of this scraped amount on both sides was 5.
If it was less than μm, it was determined that the abrasion resistance was very good, if it was 5 to 7 μm, it was determined that the abrasion resistance was good, and if it was more than 7 μm, it was determined that the abrasion resistance was poor. This value of 7 .mu.m is a critical point for strictly determining whether or not the surface of the film is scraped during processing steps such as printing and calendering, thereby causing troubles in processing and product performance.

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

Examples 1 to 12 As particles A, δ-alumina, titania sol, titanium nitride, and crosslinked polymer particles were selected, each having a different average particle size d1 but within the range of the present invention, and as particles B, average particle size d2 was selected. Select silica, calcium carbonate, and crosslinked polymer particles each having different values but within the scope of the present invention, and uniformly disperse them in 19 ethylene glycol.
After heat treatment at 5°C for 2 hours, polycondensation is carried out after transesterification with dimedyl terephthalate to create a polyester containing both particles A and B in a concentration considerably higher than the range specified in the present invention, which is then made into master pellets. I made it. At the stage of preparing this master pellet, the ratio of particles A and B contained in the master pellet was determined.

Each master pellet and a polyester pellet that does not contain particles are mixed so that the content of particles A and B is within the range of the present invention, and the mixed pellet is
Area L1-dried (3-"orr) for 3 hours at 0'C. The pellets were fed to an extruder and melt extruded at 290C,
Using the electrostatic casting method, it is wrapped around a chelating drum with a surface temperature of 30°C and cooled and solidified to a thickness of approximately 180°C.
An unstretched film of μIn was made. The draft ratio at this point was 22.

This unstretched film was stretched 3.4 times in the longitudinal direction at 90°C. This stretching is performed with a difference in the peripheral speed of two sets of rolls,
The stretching speed was 10,000%/min. Stretch this -axis film using a stenter, & If 3000%
Stretched 3.6 times in the width direction at 100℃/min, and stretched 1 times in the width direction.
．． A biaxially oriented polyester film having a thickness of 15 μm was obtained by heat treatment at 210° C. for 5 seconds while slightly stretching the film by a factor of 0.05. As shown in Table 1, the performance of these films is that the average particle diameter of particles A and B and the 1 content are within the range of the present invention, and the degree of uneven distribution of particle A is greater than 1, so the scratch resistance is excellent. , Abrasion resistance +! 1 and 1 were both excellent films.

Comparative Examples 1 to 10 Particles A and B whose average particle diameters are outside the scope of the present invention,
Those whose content falls outside the scope of the present invention, and particles A
are uniformly dispersed and the degree of maldistribution in the particles is substantially 1, or the degree of maldistribution is less than 1 and the concentration of particles A in the bulk region is higher, respectively, by the same production as in the above example. A biaxially oriented polyester film with a thickness of 15μ7n was obtained by this method. As shown in Table 2, the performance of these films is that even if the average particle size, content, or uneven distribution of particles A and [3 in the particles are outside the scope of the present invention, scratch resistance and abrasion resistance are maintained. It was not possible to obtain a film that was compatible with both properties. In addition, the poly 1 sprue in both Examples and Comparative Examples was polyethylene terephthalate.

[Effects of the Invention] As explained above, according to the present invention, the content of two types of particles A and B having an average particle diameter in a specific range and a concentration of Since the biaxially oriented polyester film has a large diameter, it is possible to obtain a film with excellent scratch resistance and abrasion resistance (abrasion resistance) that can withstand all the harsh conditions of use these days.

Claims (1)

[Claims] Contains one or two types of particles A and B, where particle A has an average particle diameter of 5 to 300 nm and a content of 0.1 to 2% by weight, and particle B has an average particle size of 5 to 300 nm and a content of 0.1 to 2% by weight. Diameter is 300-2000nm, content is 0
．． 005 to 0.5% by weight, and the concentration of particles A in a region near particles B is higher than the concentration in other regions. 2. The biaxially oriented polyester film according to claim 1, which has a surface resistivity smaller than 1×10^1^5 Ω·cm.