JPH02214732A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To provide the subject film containing specific amounts of two specific kinds of inert particles, having high scratch resistance, effective in preventing the damage of a magnetic layer applied to the film and suitable as a base film for magnetic tape. CONSTITUTION:The objective film contains two kinds of inert particles A and B. The particle A has an average particle diameter d1 of 10-500nm and a Mohs hardness of >=6 and its content in the film is 0.2-2.0wt.%. The particle B has an average particle diameter d2 of 300-1,500nm and larger than the average diameter d1 of the particle A, a Mohs hardness of <6 and a content of 0.005-0.15wt.% in the film. The difference between the Mohs hardness of the particle A and that of the particle B is preferably >1. 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, which is particularly suitable as a base film for magnetic tapes, and has excellent scratch resistance and scratch resistance on the magnetic surface after coating the magnetic layer. The present invention relates to a biaxially oriented polynisdel film with excellent anti-resistance properties and the like.

[Prior Art] Previously (by the present applicant), as a base film for packaging, condensation, or magnetic tape, the average particle size is 0.05~
A biaxially oriented polyester film containing particles having a Mohs hardness of 2.0 μm rL1 and 7 or more has been proposed (Japanese Unexamined Patent Publication No. 63-230741).

In this film, by containing hard particles, the wear resistance of the film surface is improved, and by making the particle size relatively large, it is possible to improve the abrasion resistance of the film surface during film processing or when it is made into a product. It is designed to ensure good slipperiness and running f1.

[Problems to be Solved by the Invention] However, the quality requirements for polynisdel films, especially biaxially oriented polyester films as base films for magnetic tapes, have become increasingly strict in recent years. In the film proposed in Publication No. 230741,
In particular, the scratch resistance of the surface and the prevention of scratches on the magnetic surface after the magnetic layer is applied to the base film are still not satisfactory.

In other words, as the speed of the magnetic layer coating process increases, there is a growing need for high scratch resistance that will not damage the film surface even if it comes into contact with various rolls during the process.
Simply incorporating hard particles with a relatively large particle size as in the proposed film above increases the hardness and abrasion resistance of the portions of the film that protrude like projections on the surface of the film. Since the skin (the surface area other than the above-mentioned protrusions) itself is not reinforced, there is a risk of scratches on this skin.Also, the skin F1!
As a result of not reinforcing one part, the holding force of the particles on the film surface is not sufficient, and there is a risk that the particles may fall off due to external force received from the rolls, etc. that come in contact with the film, and if they fall off, they will stick to the roll surface, etc. However, there is a risk that the surface of the film may be damaged by the deposits.

After the magnetic layer is applied to the base film, the film is usually wound into a roll.

Therefore, during winding, the magnetic surface and the surface of the base film opposite to the magnetic layer coating come into contact. At this time, if the protrusions formed on the surface of the base film by the contained particles are too hard, there is a risk of damaging the magnetic surface. In particular, scratches are likely to occur when a relative shear velocity occurs between the two surfaces, or when contained particles fall off the film surface as film powder and the fallen powder is caught between the base film surface and the magnetic surface.

The present invention overcomes the above-mentioned problems and improves the scratch resistance of the surface of a biaxially oriented polyester film, and also improves the scratch resistance of the magnetic layer after it is coated on the film. The purpose is to prevent

[Means for Solving the Problems] The biaxially oriented polyester film of the present invention that meets this objective contains two types of inert particles A and B, and the particles A have an average particle diameter d1 h of 10 to 500 nm, The Mohs hardness is 6 or more, the content is 0.2 to 2.0% by weight, the particle B has an average particle diameter d2 of 300 to 1500 nm, which is larger than the average particle diameter d1 of the particles, and the Mohs hardness is less than 6. , the content η is 0.0
0.05 to 0.15% by weight.

The polyester in the present invention includes ethylene terephthalate, ethylene α/β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, ethylene 2,6
The main constituent is at least one structural unit selected from -naphthalene-1 unit. 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 inert particles A1B.

Particles A are relatively small particles with an average particle diameter d1 of 10 to 500 n1m. If the average particle size is smaller than this range, the scratch resistance will be poor, which is not preferable.

In addition, since particle A has a high hardness, the protrusions on the film surface formed by particles A also become hard, but if the average particle size of particle A becomes larger than the above range, the protrusions on the film surface formed by the particles become hard. This is not preferable because the magnetic surface is likely to be ridged. In general, if the particle size of the contained particles becomes too large, the effect of reinforcing the film background by the particles will decrease. As will be described later, the particles A mainly play a role in reinforcing the film background, and from this point of view as well, the upper limit of the average particle size range is suppressed as described above.

Particle A has a Mohs hardness of 6 or more. If it is smaller than this, the effect of reinforcing the surface of the film will be small, and the desired scratch resistance will not be improved by 1q.

In addition, the content of particles A is 0.2 to 2.0 fffffl%
It is prepared within the range of . If the amount is less than this range, particles A
The effect of reinforcing the surface of the film due to its inclusion is weakened, and the desired scratch resistance is not improved by 1q. If the amount exceeds this range, there will be too much content, making it easier for the film itself to be structurally scraped off, or for the contained particles to fall off easily, and the magnetic surface and film surface to be damaged by film dust and fallen particles. This is not preferable as it makes it easier to get damaged.

The particles B are relatively large particles with an average particle diameter d2 of 300 to 1500 nII+, and the average particle diameter d2 is set larger than the average particle diameter d1 of the particles A (d2>d
t). Since this particle B is a relatively large particle,
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 that portion can be made rougher. As the roughness increases, the coefficient of friction can be reduced.
As a result, the scratch resistance of the film surface improves, but
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 poor, which is not preferable. On the other hand, if it is larger than the above range, the surface protrusions formed by the whites of particles 13 or particles B tend to fall off, and the chances of the falling objects damaging the magnetic surface and film surface increase, which is not preferable.

The Mohs hardness of particles B is less than 6. Particles B mainly contribute to roughening the film surface and lowering its coefficient of friction, but if the Mohs hardness is 6 or more, the protrusions on the film surface formed by particles B will become too hard. The protrusions may damage the magnetic surface. On the other hand, if the -E-su hard melon of particle B becomes too low, it may become difficult to form effective protrusions on the film surface, or even if protrusions are formed, the protrusions will not be sufficient to withstand the contact pressure etc. Since it has no affinity with This is also a practical manufacturing limit for particles that are included to reduce the coefficient.

The content of particles B is adjusted to a range of 0.005-0.15% by weight. 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 the desired scratch resistance, and the number of high protrusions on the film surface due to particles B will decrease, causing the magnetic surface to have hard protrusions due to the particles. Since the chances of contact with the magnetic surface rapidly increase, the scratch prevention performance of the magnetic surface decreases. Conversely, if the amount exceeds the above range, particles B
Alternatively, the projections on the film surface caused by the particles B tend to fall off, and the magnetic surface and the film surface are likely to be damaged by the falling particles, which is not preferable.

In the relationship between particles A and B, the average particle diameters d1 and d2
The magnitude relationship between the two is <d2>dl as described above. If d1≧d2, when the base film surface and the magnetic surface come into contact during winding, etc., hard film surface protrusions caused by particles will come into direct contact with the magnetic surface, and these protrusions may damage the magnetic surface. It is not desirable because it attaches. That is, in the present invention, although the possible ranges of dl and d2 overlap, it is necessary that dt < d2.

Further, regarding the Mohs hardness, it is preferable that the Mohs hardness of particle A - Mohs of particle B + 1 degree>1, and it is more preferable that this difference is 2 or more. By increasing this difference, particles A tend to become harder, improving the film background reinforcing effect, and particles B tend to become softer, making it difficult for surface protrusions caused by particles B to damage the magnetic surface. It becomes easier to achieve both improved scratch resistance and prevention of scratches on the magnetic surface.

The specific material of the inert particles AXB is not particularly limited as long as it satisfies the above-mentioned requirements, but it is preferably a Q material that has an affinity with polynisder. When the affinity is good, the contained particles are difficult to aggregate and are easily dispersed uniformly, and
Since the bonding force with the film base material can be maintained high, particles or film surface protrusions formed by particles are less likely to fall off. As such inert particles, examples of materials for particles A include zirconia, butane nitride, α-alumina, T-alumina, and δ-alumina, and examples of materials for particles B include calcium phosphate and calcium carbonate. Can be mentioned.

Although the present invention has the above-mentioned composition as a main component, it is also possible to blend trusted polymers within the range that does not impede the purpose of the present invention, and inorganic materials such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers. Alternatively, organic 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. An unstretched film or a -axially oriented film is not preferred because the scratch resistance is reduced and the particles or film surface protrusions formed by the particles tend to fall off.

Further, the plane orientation index representing the degree of biaxial orientation is not particularly limited, but is 0.935 to 0.975, particularly 0°9.
Scratch resistance in the range of 40-0.970;
This is desirable because it provides even better resistance to falling off. Further, it is particularly preferable that the density index of the film of the present invention is in the range of 0.02 to 0.05, since the scrap resistance and shedding resistance become even better.

Further, the film of the present invention has an average surface roughness Ra in the width direction of 0.005 to 0.030 μ7L, particularly 0.007 to 0.7L.
A thickness in the range of 0.025 μm is particularly desirable because the scratch resistance becomes even better.

Friction coefficient μk tfiO,2 of the film in the present invention
A value in the range of 0 to 0.35 is particularly desirable because scratch resistance becomes even better.

Furthermore, the surface resistivity of the film of the present invention is 1×1015Ω・
It is particularly desirable when the thickness is smaller than cm, since scratch resistance and falling resistance become even better. If it exceeds this value,
The fallen film may become lumpy due to static electricity, etc.
Film powder that becomes clumpy or clumpy is undesirable because it may damage the surface of the base film or the magnetic surface.

Next, the details of the method for manufacturing the film of the present invention will be explained.

First, as a method for adding inert 14 particles A and B to a given polyester, they may be added before polymerization, during polymerization, or at the φ joint. An effective method is to add it in the form of a slurry by kneading and dispersing it. Furthermore, as a method for adjusting the hω content of particles, a method of diluting high-temperature master pellets 1 to 1 during film formation is effective. Using particles A and B, adjust the melt viscosity and copolymerization components of the master pellet at a high temperature, preferably 1 to 5%, to obtain the difference (T
CC--r q > from 65 to 110°C, especially from 75 to
It is extremely effective to keep the temperature at 100°C.

Furthermore, it is effective to add a slurry of inert particles A and B dispersed in ethylene glycol before or during the polymerization reaction to obtain an average particle size within the range of the present invention.

In the present invention, a high IIfJj master polyester containing inert particles A and B separately may be produced, but the particles A and B may be mixed in advance at a predetermined mixing ratio during polymerization or master pellet production. The most preferable method is to put the film at 11 degrees Celsius and then dilute the prepared master pellet with other chips and pellets at the film manufacturing stage to reach a predetermined concentration.

After sufficiently drying the polyester pellets containing a predetermined amount of inert particles A and B, the polyester pellets are supplied to a known melt extruder, extruded into a sheet through a slit die at 210°C to 330°C, and then passed through a casting roll. The film is cooled and solidified 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 as high as 16 times or more. When high draft casting is performed, a peculiar phenomenon occurs in which particles concentrate on the surface layer, and particles A
Performing such a high draft cast is particularly effective in the present invention because it makes it easier for each of the 1Bs to perform their intended functions.

Next, this unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial 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 longitudinal direction and then in the width direction.
This inkstone may be reversed and stretched/stretched. The conditions for two-wheel stretching are not necessarily constant depending on the stretching method, type of polymer, etc., but are usually 80 to 160°C in both the longitudinal and width directions.
Preferably, the temperature is in the range of 90 to 150°C, the stretching ratio is in the range of 3° to 5.0 times, preferably 3.2 to 4.5 times, and the stretching speed is in the range of 1000 to 70.000%/min. The range is f-suitable.

Next, this stretched film is heat treated. The heat treatment length is 1 to 15%, preferably 2 to 10% in the constant length and width direction.
under relaxation of
0°C, preferably 0.5 to 6 in the range of 170 to 220°C
0 seconds is suitable.

[Function] In the biaxially oriented polyester film of the present invention as described above, the average particle diameter d1 is small, and Morse & J. Particles with a high degree of hardness and a high content of Particles 8 sufficiently reinforce the film background and significantly improve scratch resistance. The surface of the film is roughened by B,
In addition to lowering the coefficient of friction and further improving scratch resistance, the protrusions formed by the particles B formed on the film surface are kept soft, which prevents scratches on the magnetic surface when the base film surface comes into contact with the magnetic surface. Prevented. Also,
As a result of Particle 8 reinforcing the film surface, the holding power of Particle B or film surface protrusions formed by Particle B is also increased, making it difficult for them to fall off and preventing damage to the base film surface or magnetic surface due to falling objects. Even more Ei
f is actually prevented.

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

(1) Particle content (G% by weight) Polyester resin is incinerated with a plasma device, and the concentration of each element in the polyester is determined using an atomic absorption spectrometer (for example, △A680 model manufactured by Shimadzu Corporation). , the amount of 416 particles from the element is converted from the molecular weight of the particles, and the weight %
Close and ask. Incidentally, the chemical composition of the particles can be determined by methods such as X-ray diffraction.

Further, depending on the essence, -C, fluorescence X-ray analysis, pyrolysis gas chromatography, infrared absorption, Raman scattering, etc. can be used for quantitative determination.

(2) Average particle diameter of particles (n?rt) The film containing the particles was cut into ultrathin sections perpendicular to the plane of the film to a thickness of 1000 mm, and a transmission electron microscope (for example, JEOL JEH-1200EX, etc.) was used. The particles were observed using the same method, and the average value over 100 visual fields was defined 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) Measure a test piece with the same composition and structure as the particles added to the Mohs hardness film, or use a mineral that has not been crushed into particles as a test piece, and scratch it against the standard mineral for Mohs hardness measurement. ,
The hardness number is measured to the nearest 0.1 depending on whether scratching occurs.

(4) Planar orientation index Sodium D line (wavelength 589 nm) Using Atsube's refractive index ■ as a light source, calculate the refractive index in the thickness direction of the biaxially oriented film (denoted as A) and place 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 rapid cooling was measured, and A/B was taken as the plane orientation index. Methylene iodide was used as the mounting liquid.
Measured at 25°C and 165% RIM.

(5) Glass transition point - [q, cold crystallization temperature - Measured using a DSC (Differential Scanning Calorie ωh1) model manufactured by RCC Perkin 1 Lumane 1. The thread attachment of DSC is as follows. In other words, set samples 10Tri, 9 in the DSC device,
After melting for 5 minutes at a temperature of 300°C, it is cooled in liquid nitrogen. This rapidly cooled sample is back-heated at 10° C./min, and the glass transition point of 1゛q is detected. Continuing to gradually increase the temperature, the crystallization exothermic peak from the glass state reaches the cold crystallization temperature - [
I made it CC. Here, the difference between T-CC and Tg (-rcc-
-rq) is defined as Δ-rcg.

(6) Density index ") - The density of the film measured using a density gradient tube made of hebutane/carbon tetrachloride is ρ1 (g/cri), and the film is melt-pressed and then rapidly cooled in water at 10 °C. The dense garden ρ of the non-oriented (amorphous) film made by
The difference (ρ1−ρ2) from 2 was calculated as the density index by multiplying by 5.

(7) Tape runability test IITB-r-3oo type [manufactured by Yokohama System Research Institute Co., Ltd.] was used for the friction coefficient μ, 20'C160%R)
The vehicle was run in a −1 atmosphere, and the initial μk (friction coefficient) was determined from the following formula.

μ=o, 733 1oO (T1/”T-Ro) Here, To is the inlet tension and T1 is the outlet tension. The guide diameter is 6/Il#lΦ, and the guide material is 5US27 (surface roughness). degree 0.23), wrapping angle is 180°, running speed is 3
．． It is 3 crn/sec.

(8) Surface specific resistance was measured using a superinsulator meter [Type IVE40 manufactured by Kawaguchi Electric Seisakusho Co., Ltd.].

(9) Scratch resistance tape running test 11 Using TBT300 D/H type [Yokohama System Research Institute Co., Ltd.], the film was slit into a tape shape with a width of 172 inches, tension 30 g, running speed) 1
At 2so rrt/min, wrap around the video cassette tape guide pin (stainless steel guide pin with surface roughness R↑ and 2500 nm culmosity) for 60 m with a wrapping angle of 60°.
The vehicle was run, and the appearance of scratches formed during the run was visually judged according to the following criteria.

No scratches at all...5 points Light scratches: LJ...3 points Deep scratches - B...・・・・・・・・・・・・1 point Also, the middle point between 5 points and 3 points was set as 4 points, and the middle point between 3 points and 1 points was set as 2 points. At this time, a score of 3 or more indicates good scratch resistance, and a score of less than 3 indicates poor scratch resistance.

If the film size is less than 3 Y as determined at this time, the surface of the film will be abraded and deep scratches will occur during processing or when the film is run as a product, resulting in a significantly poor quality of the product.

(10) Scratches on magnetic surface A commercially available videotape (manufactured by TDK 1-13-120) was damaged with a diameter of 7 tnm using J1009 with the magnetic P1 side facing up.
Wrap the length of the tape around the pin in the circumferential direction. Wrap the evaluation film roughly slit into 1/2 inch width at a 60 degree angle and with a tension of 5J7, aligning the longitudinal direction of the evaluation film with the longitudinal direction of the videotape. It goes back and forth 10 times. At this time, the scratches generated on the magnetic surface were observed, and when there were almost no scratches, the magnetic scratches were determined to be good, and when there were 10 or more scratches per hoop width, the magnetic scratches were determined to be poor.

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

Examples 1 to 14 As inert particles 8, zirconia, titanium nitride, α-alumino, γ-alumina, and δ were used, each having a different average particle diameter d1 but within the range of the present invention, and a Mohs hardness within the range of the present invention. - Select alumina particles, and as particles B, select calcium phosphate and calcium carbonate particles whose average particle diameter d2 is within the range of the present invention, and whose Mohs hardness is within the range of the present invention, and each is in ethylene glycol. After uniformly dispersing the particles and heat-treating them at 195°C for 2 hours, they were combined with dimethyl terephthalate after a transesterification reaction to create a polynisdel containing each particle at a considerably higher concentration than the range specified in the present invention, I made it into a master pellet.

Each master pellet and a polyester pellet containing no particles are mixed so that particle A and particle B fall within the range of the content ratio of the present invention, and the mixed pellet is
It was dried under reduced pressure (3 Torr) at 0'C for 3 hours. The pellets were fed into an extruder, melt-extruded at 290'C, and the surface temperature r was measured using an electrostatic application method. It is wrapped around a casting drum at 30°C, cooled and solidified, and has a thickness of about 180 ml.
An unstretched film of μm was made. The draft ratio at this time was 22.

This unstretched film was stretched 3.4 times in the longitudinal direction at 90°C. This stretching was carried out with a difference in peripheral speed between two sets of rolls, and the stretching speed was 10,000%/min. This -axis film was stretched using a sudentor [1 at 3000%/min].
Stretched 3.6 times in the width direction at 00°C, 1.05 times in the width direction
A biaxially oriented polynisdel film with a thickness of 15μ7n was produced by heat-treating it at 210°C for 5 seconds while slightly stretching it. l
is. As shown in Table 1, the performance of these films is that the average particle diameter, hardness, and content of inert particles A and B are within the range of the present invention, so they have excellent scratch resistance and prevention of scratches on the magnetic surface. A film with excellent properties was obtained.

Comparative Examples 1 to 10 Inert particles A and B whose average particle diameter is outside the scope of the present invention, whose content is outside the scope of the present invention, and
For those which are out of the scope of the present invention in terms of Mohs hardness by changing the combination of particles used as described above, the thickness of 15 μm or more was produced using the same manufacturing method as in the above example. A biaxially oriented polyester film of W was obtained. The performance of these films is second to none.
As shown in the table, the average particle diameter of particles A and B, Mohs hardness,
Even if the content was outside the range of the present invention, no film was found that was able to achieve both scratch resistance and scratch prevention properties on the magnetic surface. In addition, the polyester in both Examples and Comparative Examples was polyethylene terephthalate.

[Effects of the Invention] As explained above, according to the present invention, a biaxially oriented polynisdelic acid containing two types of inert particles A and B having an average particle diameter, Mohs hardness, and content within a specific range. Since it is made into a film, it is possible to obtain a film with excellent scratch resistance and scratch prevention performance on the magnetic surface, which can withstand recent harsh usage conditions.

Note that in J3 in this specification, the explanation focused on the pace noilum for magnetic tapes because the film of the present invention provides excellent scratch-preventing performance on the magnetic surface, but the film of the present invention has the same [14] Since it has excellent scratch resistance, it goes without saying that the film of the present invention can also be applied to the above applications.

Claims (1)

[Claims] 1. Contains two types of inert particles A and B, where particle A has an average particle diameter d_1 of 10 to 500 nm, a Mohs hardness of 6 or more,
The content is 0.2-2.0% by weight, and particle B has an average particle size d_
2 is 300 to 1500 nm and larger than the average particle diameter d_1 of the particles A, the Mohs hardness is less than 6, and the content is 0.0
05 to 0.15% by weight of a biaxially oriented polyester film. 2. The biaxially oriented polyester film according to claim 1, wherein the difference between the Mohs hardness of the particles A and the Mohs hardness of the particles B is greater than 1. 3. The biaxially oriented polyester film according to claim 1 or 2, which has a surface resistivity smaller than 1×10^1^5 Ω·cm.