JPH0760832A - Biaxially oriented film - Google Patents

Abstract

(57) [Summary] [Structure] Primary particle size 10 to 200 nm, average particle size 50 to 6
Agglomeration α of 00 nm and particle density of 3.4 to 4.0 g / cm ³
A biaxially oriented film containing alumina particles. [Effect] According to the biaxially oriented film of the present invention, since agglomerated α-alumina particles having a specific primary particle size, secondary particle size and particle density are used, the film surface is not easily scratched, and the film is not suitable for magnetic media. When this is done, excellent image quality and dropout characteristics can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biaxially oriented film.

[0002]

2. Description of the Related Art As a biaxially oriented film, for example, a biaxially oriented polyester film, a film in which agglomerated aluminum oxide particles are contained in polyester is known (for example, JP-A-3-6239).

However, in the above-mentioned conventional biaxially oriented film, for example, the process speed of the magnetic layer application in a magnetic medium application, the calendering process, or the process of producing a soft tape or the like by dubbing the resulting video tape or the like. Along with the increase, there is a drawback that the surface of the film is scratched by the contacting rolls or guides. Further, the conventional one has a drawback that the image quality when formed into a video tape, that is, the S / N (signal / noise ratio) is insufficient because of the deterioration of the image quality during the dubbing. The present invention solves such a problem, and in particular, a biaxially oriented film in which a film is less likely to be scratched in a high-speed process (hereinafter referred to as excellent in scratch resistance) and has little deterioration in image quality during dubbing (hereinafter referred to as excellent in dubbing resistance) The purpose is to provide.

[0004]

A biaxially oriented film of the present invention which meets this object has a primary particle size of 10 to 200 nm, an average particle size of 50 to 600 nm, and a particle density of 3.4 to 4.0 g / c.
It is characterized by containing m ³ aggregated α-alumina particles.

The polymer constituting the biaxially oriented film of the present invention is not particularly limited, but polyester is preferable. The polyester is not particularly limited, but at least one selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4.4′-dicarboxylate, and ethylene 2.6-naphthalate unit.
It is preferable to use various kinds of structural units as main constituents because scratch resistance and dubbing resistance are further improved. Of these, polyesters containing ethylene terephthalate as a main constituent component are particularly preferable because the dubbing resistance and scratch resistance are further improved. Two or more kinds of polyesters may be mixed, or a copolymerized polymer may be used, as long as the present invention is not impaired.

The biaxially oriented film of the present invention contains agglomerated α-alumina particles in order to improve scratch resistance and dubbing resistance. The primary particle size of the aggregated α-alumina particles is 10 to 200 nm, preferably 20 to 150 nm, more preferably 30 to 100 nm. The average particle size is 50 to 600 nm, preferably 60 to 500 nm,
More preferably, it is 70 to 400 nm. Primary particle size,
If the average particle size is out of this range, scratch resistance and dubbing resistance deteriorate. Further, the density of the agglomerated α-alumina particles is 3.4-from the viewpoint of scratch resistance and dubbing resistance.
4.0 g / cm ³ , preferably 3.5 to 4.0 g / cm
³ and more preferably 3.6 to 4.0 g / cm ³ .

The content of the agglomerated α-alumina particles is not particularly limited, but from the viewpoint of scratch resistance and dubbing resistance,
0.01 to 3% by weight, preferably 0.05 to 2% by weight,
More preferably, it is 0.1 to 1% by weight.

From the viewpoint of scratch resistance and dubbing resistance, the biaxially oriented film of the present invention includes γ-alumina, δ-alumina, θ-alumina, zirconia, silica and titanium in addition to the above-mentioned aggregated α-alumina particles. It is preferable to contain at least one kind of agglomerated particles A selected from From the viewpoint of scratch resistance and dubbing resistance, the primary particle diameter of the aggregated particles A is not particularly limited, but is 5 to 100 nm, preferably 10 to 80 nm, and the aggregate secondary particle diameter is not particularly limited, but is 20 to 800 nm, preferably Is 25 to 600 nm, and the content is not particularly limited, but is 0.01 to 3% by weight, preferably 0.05 to 2% by weight.

Further, from the viewpoint of scratch resistance and dubbing resistance, the biaxially oriented film of the present invention preferably contains monodisperse particles B in addition to the above-mentioned aggregated α-alumina particles. The type of the monodisperse particles B is not particularly limited, but calcium carbonate, colloidal silica, titanium oxide,
Organic particles and the like are preferably exemplified. In the case of calcium carbonate, although not particularly limited, the crystal form is calcite type,
In the case of the vaterite type, scratch resistance and dubbing resistance are particularly good. In the case of organic particles, crosslinked organic particles having a vinyl group, for example, are preferred. In the case of crosslinked organic particles, although not particularly limited, the degree of crosslinking is 51%.
Or more, preferably 60% or more, more preferably 75%
The above-mentioned divinylbenzene copolymer particles are particularly preferable.
Further, silicone particles represented by the general formula CH ₃ SiO _1.5 are also preferably exemplified. The monodisperse particles B of the biaxially oriented film of the present invention may contain two or more kinds of them in combination.

The average particle size of the monodisperse particles B is 0.1.
˜2 μm, preferably 0.2 to 1.5 μm, more preferably 0.3 to 1 μm. The content of the monodisperse particles B is not particularly limited, but is 0.01 to 10% by weight, preferably 0.05 to 8% by weight, and more preferably 0.1.
When it is up to 6% by weight, scratch resistance and dubbing resistance are particularly good.

The biaxially oriented film of the present invention contains the above-mentioned polymer and agglomerated α-alumina particles as main components, but may be blended with another polymer within a range not impairing the object of the present invention. Organic and inorganic additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers may be added to the extent that they are usually added.

The biaxially oriented film of the present invention is a film obtained by biaxially orienting the above composition. A uniaxial or non-oriented film is not preferable because scratch resistance becomes poor. The degree of this orientation is not particularly limited, but especially when the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 350 kg / mm ² or more in both the longitudinal direction and the width direction, scratch resistance is further improved. preferable.

In the biaxially oriented film of the present invention, even if the Young's modulus is within the above range, a part of the film in the thickness direction, for example, the orientation of polymer molecules near the surface layer is non-oriented or uniaxially oriented. If not, that is, if the molecular orientation of the entire portion in the thickness direction is biaxial orientation, scratch resistance and dubbing resistance are further improved. Especially scratch resistance and dubbing resistance are better when the molecular orientation measured by Abbe refractometer, laser refractometer, total reflection laser Raman method, etc. is biaxial orientation on both front and back surfaces. Becomes

In the biaxially oriented film of the present invention, from the viewpoint of scratch resistance and dubbing resistance, the film containing agglomerated α-alumina particles is one outermost layer of a laminated film having at least a two-layer structure. Is preferred.

When the biaxially oriented film of the present invention has a structure of three or more layers, the film containing the aggregated α-alumina particles has a three-layer structure in view of scratch resistance and dubbing resistance. It is preferably one outermost layer of the laminated film.

Monodisperse particles B other than the aggregated α-alumina are
It may be contained in the same layer as the agglomerated α-alumina particles, or may be contained in a different layer, but scratch resistance, particularly preferred from the viewpoint of dubbing resistance,
(1) Aggregated α-alumina particles and monodisperse particles B are contained in the same outermost layer on at least one side, and the relationship between the film layer thickness t and the particle diameter d of the monodisperse particles B is 0.2d ≦ t. ≤
10d, preferably 0.5d ≦ t ≦ 5d, more preferably 0.5d ≦ t ≦ 3d, or (2) the thickness t of the film layer containing the monodisperse particles B and the monodisperse particles B The particle size d of 0.2d ≦ t ≦ 10d, preferably 0.5d ≦ t ≦ 5d, more preferably 0.5d ≦
t ≦ 3d, a layer containing agglomerated α-alumina particles is present as the outermost layer on the outer side, and the thickness of the outermost layer is 0.005 to 1 μm, preferably 0.01 to 0.5 μm.
m, and more preferably 0.02 to 0.3 μm.

The polymer constituting the layers other than the film layer containing the agglomerated α-alumina particles in the laminated structure is not particularly limited, but polyester is preferable. The polyester is not particularly limited, but ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, ethylene 2,6
-When at least one structural unit selected from naphthalate units is the main constituent component, scratch resistance and dubbing resistance are better, which is preferable. Of these, polyesters containing ethylene terephthalate as a main constituent component are particularly preferable because the dubbing resistance and scratch resistance are further improved.

From the viewpoint of dubbing resistance and scratch resistance, the biaxially oriented film of the present invention preferably has the number of projections on at least one side of 2 × 10 ^{3 to} 5 × 10 ⁵ pieces / mm ² . The number of protrusions on at least one side is preferably 3 ×
10 ³ to 4 × 10 ⁵ pieces / mm ² , more preferably 5 × 1
0 ^{3 to} 3 × 10 ⁵ pieces / mm ² .

Next, the method for producing the film of the present invention will be described in the case of a laminated polyester film.

First, as a method for incorporating agglomerated α-alumina particles, other agglomerated particles A and monodisperse particles B into polyester, the particles are first dispersed as a slurry in ethylene glycol. Then, the particle-containing ethylene glycol is polymerized with a predetermined dicarboxylic acid component. Further, a method of directly kneading the particle slurry into a predetermined polyester by using a vent type twin-screw kneading extruder is also very effective for further improving the effect of the present invention.

As a method for adjusting the content of particles, it is effective to prepare a high-concentration master by the above method and dilute it with a polyester which does not substantially contain particles at the time of film formation.

Next, pellets containing a predetermined amount of particles are dried, if necessary, and then fed to a known melt extruder,
An unstretched film is produced by extruding a sheet from a slit die and cooling and solidifying it on a casting roll.
That is, two or three extruders, two or three layers of manifolds or merging blocks are used to stack polyester in a molten state. In this case, a method of installing a static mixer and a gear pump in the polymer channel containing the agglomerated α-alumina particles is effective in further improving the effect of the present invention.

Next, this unstretched film is biaxially stretched to be biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, using a sequential biaxial stretching method in which stretching is first performed in the longitudinal direction and then in the width direction, the stretching in the longitudinal direction is divided into three or more stages, the longitudinal stretching temperature is 80 to 150 ° C., and the total longitudinal stretching ratio is 3.0. ~ 5.5
It is preferable to perform the stretching at a doubling and a longitudinal stretching speed of 5,000 to 50,000% / min. As a stretching method in the width direction, a method using a tenter is preferable, a stretching temperature is 80 to 160 ° C., a stretching ratio in the width direction is 3.5 to 6.5 times larger than a longitudinal ratio, and a stretching speed in the width direction is 1000 to 20000% / min. Is preferred.

Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., especially 170 to 2
The range of 0.5 to 60 seconds at 10 ° C. is suitable.

[0025]

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows.

(1) Primary particle size of agglomerated particles, secondary particle size of agglomerated particles, average particle size of monodisperse particles Using a transmission electron microscope (TEM), the cross section of the film was
Observe at a magnification of 0,000 times or more. Section thickness of TEM is about 1
It is set to 00 nm, and the location is changed to measure 100 fields or more.
The primary particle size of the agglomerated particles is the number average diameter of the smallest unit of particles that cannot be divided, the secondary particle size of the aggregate is the number average diameter of the agglomerates, and the particle size of the monodisperse particles is the weight average of the monodisperse particles. It is the diameter (equivalent equivalent circle diameter).

(2) Content of Particles A solvent in which the polyester is dissolved but not the particles is selected is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is taken as the particle content.
In some cases, the combined use of infrared spectroscopy is also effective.

(3) Particle Density The particles separated in (2) above were determined by the pycnometer method, but the method is not limited to this.

The measurement procedure is as follows.

In advance, deaerated pure water (23 ° C.,
The volume V (cm ³ ) of the pycnometer is determined on the basis of 0.99754 / cm ³ , quoted from the Chemical Handbook).

The density d ₂ (g / cm ³ ) of the immersion liquid (toluene) at 23 ° C. is measured using a Lipkin-Davison type pycnometer (internal volume of about 5 cm ³ ).

After washing and drying the pycnometer,
Place the material in a pycnometer and weigh it. This weight is W
_Set to ₁ .

The immersion liquid is added until the sample is immersed, and the air in the sample and the immersion liquid is removed in a vacuum desiccator.

Let stand for a while.

It is placed in a constant temperature bath and kept for 20 minutes or more.

After accurately filling the immersion liquid up to the marked line of the pycnometer, it is taken out from the thermostat and the external water is wiped off cleanly. The weight is measured and the weight of the added immersion liquid is calculated. The weight of this immersion liquid is W ₂ .

The density d ₁ of the sample is calculated as follows. First, assuming that the volume of the added immersion liquid is V ₂ , V ₂ is calculated by the following equation. V ₂ = W ₂ / (d ₂ −0.0012) Therefore, assuming that the volume of the sample is V ₁ , V ₁ = V−V ₂ The density d ₁ of the sample to be obtained is d ₁ = (W ₁ / V ₁ ) +0 .0012

(4) Molecular Orientation on Film Surface The measurement was carried out using an Abbe refractometer with sodium D line (589 nm) as a light source. Methylene iodide was used as the mount solution, and measurement was performed at 25 ° C. and 65% RH. The biaxial orientation of a polymer has a refractive index of N in the longitudinal direction, the width direction, and the thickness direction.
_{When 1} , N ₂ and N ₃ are used, the absolute value of (N ₁ −N ₂ ) is 0.07 or less, and N ₃ / [(N ₁ + N ₂ ) / 2] is 0.95 or less. Can be a standard. Further, the refractive index may be measured using a laser type refractometer. Further, when the measurement is difficult by this method, the total reflection laser Raman method can be used. Laser total reflection Raman is measured by Jobin-Yvon Raman.
OrU-1000 Raman system measures the total reflection Raman spectrum, for example, in the case of PET, 161
5 cm ^-1 (skeleton vibration of benzene ring) and 1730 cm
Polarization measurement ratio of band intensity ratio of ^-1 (stretching vibration of carbonyl group) (YY / XX ratio, etc. where YY: Raman light detection parallel to Y with X as the laser polarization direction, X
X: Raman light detection parallel to X, where X is the polarization direction of the laser, corresponds to the molecular orientation.
The biaxial orientation of a polymer can be determined by converting the parameters obtained from Raman measurement into the refractive index in the longitudinal direction and the refractive index in the width direction, and the absolute value or difference thereof. Further, the half-value width of 1730 cm ^-1 , which is the stretching vibration of the carbonyl group, was used as the total reflection Raman crystallization index of the surface. The measurement conditions in this case are as follows.

Light source Argon ion laser (514
5 angstrom) Setting of sample The surface of the film was pressed against a total reflection prism, and the incident angle of the laser on the prism (angle with the film thickness direction) was set to 60 °. Detector PM: RCA31034 / Photon C
installing System (Hamamatsu)
C1230) (supply 1600V) measurement condition SLIT: 1000 μm LASER: 100 mW GATE TIME: 1.0 sec SCAN SPEED: 12 cm ⁻¹ / min SAMPLING INTERVAL: 0.2 cm
^-1 REPEAT TIME: 6

(5) Young's modulus According to the method specified in JIS-Z-1702,
Using an Instron type tensile tester,
It was measured at 65% RH.

(6) Crosslinking degree of crosslinked organic particles It is defined as the weight of the crosslinking component monomer of the total weight of the particle monomers.

(7) Lamination Thickness of Laminated Film Using a secondary ion mass spectrometer (SIMS), the element and polyester derived from the highest concentration of particles in the film in the depth range from the surface layer to 3000 nm are used. The concentration ratio (M ⁺ / C ⁻ ) of the elemental carbon is used as the particle concentration, and analysis is performed in the thickness direction from the surface to a depth of 3000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration once reaching the maximum value starts to decrease again.
Based on this concentration distribution curve, the surface particle concentration is 1 / maximum
A depth of 2 (the depth is deeper than the maximum value) was obtained and used as the laminated thickness. The conditions are as follows.

Measuring device Secondary ion mass spectrometer (SIMS) ATOMI, Germany
KA Co. A-DIDA3000 measurement conditions primary ion species: 0 ₂ ⁺ primary ion acceleration voltage: 12 kV primary ion current: 200 nA raster region: 400 μm □ analysis region: gate 30% measurement vacuum degree: 6.0 × 10 ^{− 9} Torr E-GUN: 0.5kV-3.0A

If the particles contained most in the depth range of 3000 nm from the surface layer are organic polymer particles, the SI
Since it is difficult to measure with MS, the depth profile similar to the above may be measured by XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy), etc. while etching from the surface layer to obtain the laminated thickness. By observing the cross section with an electron microscope or the like, the interface can be recognized from the difference in the particle concentration change and the contrast due to the difference in the polymer, and the layer thickness can be obtained.
Furthermore, after peeling the laminated polymer, the laminated thickness can be obtained using a thin film step measuring machine.

(8) Scratch resistance A film slit into a tape having a width of 1/2 inch was run on a guide pin (surface roughness: Ra of 100 nm) using a tape running tester. Allow (Running speed 2
50m / min, 1 pass, wrapping angle: 60 °, running tension: 90g). At this time, the scratches in the film were observed with a microscope, and it was judged that scratches with a width of 1 μm or more per tape width were less than 2 and excellent, 2 or more and less than 10 were good, and 10 or more were defective. Good is desirable, but good is practically usable.

(9) Dubbing resistance A magnetic coating composition having the following composition is applied to a film by a gravure roll, magnetically oriented, and dried. In addition, a small test calendar device (steel roll / nylon roll,
(5 stages), temperature: 70 ° C., linear pressure: 200 kg / cm, and then calendaring is performed at 70 ° C. for 48 hours. The above tape raw material was slit to 1/2 inch to prepare a pancake. A length of 250 m from this pancake was incorporated into a VTR cassette to obtain a VTR cassette tape.

(Composition of magnetic paint) Co-containing iron oxide: 100 parts by weight Vinyl chloride / vinyl acetate copolymer: 10 parts by weight Polyurethane elastomer: 10 parts by weight Polyisocyanate): 5 parts by weight Lecithin: 1 Parts by weight-methyl ethyl ketone: 75 parts by weight-methyl isobutyl ketone: 75 parts by weight-toluene: 75 parts by weight-carbon black: 2 parts by weight-lauric acid: 1.5 parts by weight

A 100% chroma signal was recorded on this tape by a television test waveform generator using a home VTR, and from the reproduced signal, a chroma S /
N was measured and designated as A. After dubbing the master cake pancake on which the same signal is recorded as above to the same sample tape (unrecorded) pancake on which A was measured using the magnetic field transfer type video software high-speed printing system (sprinter) The chroma S / N of the tape was measured in the same manner as above and designated as B. Chroma S / N by this dubbing
Resistance (AB) is less than 3 dB, dubbing resistance:
Excellent was judged to be good when 3 dB or more and less than 5 dB, and defective when 5 dB or more. Good is desirable, but good is practically usable.

[0049]

EXAMPLES Next, the embodiments of the present invention will be explained based on examples.

Example 1 Primary particle size 60 nm, Secondary particle size 80 nm, Particle density 3.9
Aggregated α-alumina particles of g / cm ³ were dispersed in ethylene glycol, and the ethylene glycol slurry was polymerized with terephthalic acid to obtain particle-containing polyethylene terephthalate master pellets. Further, similarly, polyethylene terephthalate master pellets containing calcium carbonate having an average particle diameter of 0.8 μm and polyethylene terephthalate master pellets containing no particles were obtained.

These polymers were mixed in appropriate amounts (polymer A: particle-free, agglomerated α-alumina, calcium carbonate, polymer B: particle-free, calcium carbonate), dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, and then, respectively. The polymer A and the polymer B are respectively supplied to the extruder 1 and the extruder 2, and 282 ° C.
Melted at 280 ° C. After high-precision filtration of these polymers, three layers were laminated at the rectangular confluence (lamination constitution: polymer A / polymer B / polymer A).

This was wound around a casting drum having a surface temperature of 25 ° C. by an electrostatically applied cast method and cooled and solidified to prepare an unstretched film. At this time, the ratio of the die slit gap / unstretched film thickness was set to 10. In addition, the total thickness and the thickness of the polymer A layer were adjusted by adjusting the discharge amount of each extruder.

This unstretched film was stretched 4.0 times in the longitudinal direction at a temperature of 91 ° C. This stretching was carried out in four stages with the difference in peripheral speed between each pair of rolls. This uniaxially stretched film is heated to 105 ° C. at a stretching rate of 2000% / min using a tenter.
And stretched 5.5 times in the width direction at a constant length for 3 hours at 195 ° C.
Heat treatment was performed for 2 seconds to obtain a biaxially oriented laminated film having a total thickness of 14 μm. The characteristics of this film are as shown in Table 1, and the scratch resistance and dubbing resistance were good.

Example 2, Example 3, Comparative Example 1, Comparative Example 2 In the same manner as in Example 1, the particle size of agglomerated α-alumina particles,
A film was obtained in which the addition amount, the type of particles other than the aggregated α-alumina particles, the particle size, and the addition amount were changed. As shown in Table 1, the films in the scope of the present invention have good scratch resistance and dubbing resistance, but those other than those cannot satisfy both scratch resistance and dubbing resistance.

[0055]

[Table 1]

[0056]

According to the biaxially oriented film of the present invention, since agglomerated α-alumina particles having a specific primary particle size, secondary particle size and particle density are used, the film surface is not easily scratched, and the magnetic medium When used, excellent image quality and dropout characteristics can be obtained.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08L 101/00 // B29K 67:00

Claims (6)

[Claims] 1. A primary particle diameter of 10 to 200 nm and an average particle diameter of 5
A biaxially oriented film characterized by containing agglomerated α-alumina particles having a particle density of 0 to 600 nm and a particle density of 3.4 to 4.0 g / cm ³ . 2. In addition to the aggregated α-alumina particles, at least one aggregated particle A selected from γ-alumina, δ-alumina, θ-alumina, zirconia, silica and titanium.
The biaxially oriented film according to claim 1, comprising: 3. At least 2 agglomerated α-alumina particles.
The biaxially oriented film according to claim 1 or 2, which is contained in one outermost layer of the laminated film having a layered structure. 4. The biaxially oriented film according to claim 1, which contains monodisperse particles B in addition to the aggregated α-alumina particles. 5. The biaxially oriented film according to claim 4, wherein the monodisperse particles B are at least one kind selected from calcium carbonate, colloidal silica, titanium oxide, and organic particles. 6. The relationship between the average particle diameter d (nm) of the monodisperse particles B and the thickness t (nm) of the film layer containing the monodisperse particles B is 0.2d ≦ t ≦ 10d. The biaxially oriented film according to claim 4 or claim 5.