JPH06136147A - Biaxially oriented film - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented film excellent in scratch resistance and dubbing resistance by incorporating a plurality of kinds of specified particles in the biaxially oriented film. CONSTITUTION:theta Alumina particles having a primary particle diameter of 5-100nm desirably 10-80nm more desirably 10-70nm and having a secondary particle diameter of desirably 20-800nm more desirably 25-600nm most desirably 30-500nm and zirconia particles having a primary particle diameter of 5-100nm desirably 10-80nm more desirably 10-70nm and having a secondary diameter of 20-1000nm more desirably 30-800nm most desirably 50-700nm are incorporated in a biaxially oriented film (e.g. polyethylene terephthalate film).

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 containing δ type alumina particles is known (for example, Japanese Patent Publication No. 4-40).
375).

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 the above problems, and in particular, the 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). It is intended to provide an axially oriented film.

[0005]

Means for Solving the Problems The biaxially oriented film of the present invention for this purpose contains θ-alumina particles having a primary particle diameter of 5 to 100 nm and zirconia particles having a primary particle diameter of 5 to 100 nm. Is characterized by.

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 is selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, and ethylene 2,6-naphthalate units. It is preferable to use at least one structural unit as a main component because scratch resistance and dubbing resistance are further improved. Among them, polyesters containing ethylene terephthalate as a main constituent 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 θ-type alumina particles having a primary particle size of 5 to 100 nm. The primary particle size is 5 to 100 nm, preferably 10 to 80 nm,
More preferably, it is 10 to 70 nm. If the primary particle size is smaller or larger than this range, scratch resistance and dubbing resistance cannot be improved. The secondary particle size is preferably 20 to 800 nm, more preferably 25.
-600 nm, most preferably 30-500 nm.

Further, the biaxially oriented film of the present invention comprises
Zirconia particles having a primary particle size of 5 to 100 nm are contained. According to the present invention, the scratch resistance and the dubbing resistance are remarkably improved by using the θ-alumina particles having the primary particle diameter in the specific range and the zirconia particles in combination. The primary particle size of the zirconia particles is 5 to 100 nm, preferably 10 to 80
nm, more preferably 10 to 70 nm. If the primary particle size is smaller or larger than this range, scratch resistance and dubbing resistance cannot be improved. Also,
The secondary particle size is preferably 20 to 1000 nm, more preferably 30 to 800 nm, and most preferably 50 to 700.
nm.

The contents of θ-type alumina particles and zirconia particles are not particularly limited, but are 0.01 to 3% by weight, preferably 0.05 to 2% by weight, and more preferably 0.1 to 1% by weight. Is good. When the content is less than this range, it is not preferable from the viewpoint of scratch resistance, and when the content is more than this range, it is not preferable from the viewpoint of dubbing resistance.

The biaxially oriented film of the present invention preferably further contains at least one kind of monodisperse particles in addition to the above two kinds of particles. The monodisperse particles are not particularly limited, for example, calcium carbonate particles, organic particles,
Colloidal silica particles, titanium oxide particles and alumina particles are preferably exemplified, and at least one kind of particles selected from organic particles, calcium carbonate particles and colloidal silica particles is particularly preferable. The organic particles are not particularly limited, but divinylbenzene particles and silicone particles are preferable. The divinylbenzene particles are particles mainly composed of divinylbenzene as a crosslinking component. The content of divinylbenzene in the particle component is 51% or more, preferably 60% or more, and more preferably 75% or more. Here, the degree of cross-linking is the weight percentage of the crosslinkable composition in the organic particle composition. The silicone particles have organopolysiloxane (CH ₃ —SiO _3/2 ) as a main component.

The particle size of the monodisperse particles is not particularly limited, but the average particle size is 0.1 to 2 μm, preferably 0.2 to.
The thickness is 1.5 μm, more preferably 0.3 to 1 μm.
The content of the monodisperse particles is not particularly limited,
When it is 0.01 to 10% by weight, preferably 0.05 to 8% by weight, and more preferably 0.1 to 5% by weight, scratch resistance and dubbing resistance are particularly good.

The biaxially oriented film of the present invention contains the above-mentioned polymer and at least two kinds of particles as main components, but other polymers may be blended within a range not impairing the object of the present invention. 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 scratch resistance is further improved 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 and width directions. Particularly preferred. Young's modulus, which is a measure of the degree of molecular orientation, is usually 1500 kg / mm
^{About 2} is the manufacturing limit.

Further, in the film of the present invention, even if the Young's modulus is within the above range, the orientation of polymer molecules in a part in the thickness direction of the film, for example, in the vicinity of the surface layer is not oriented or uniaxially oriented, that is, When 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

The biaxially oriented film of the present invention may be in the state of a single layer film, or may be in the state of being laminated as at least one layer of a laminated film.

When used as a laminated film, from the viewpoint of scratch resistance and dubbing resistance, the above-mentioned film containing at least two kinds of particles is at least one outermost layer of a laminated film having at least a two-layer structure. Preferably there is.

When the laminated structure has three or more layers,
From the viewpoints of scratch resistance and dubbing resistance, it is preferable that the film containing at least two kinds of particles is at least one outermost layer of a laminated film having a three-layer structure.

The thickness of the film layer containing at least two kinds of particles is not particularly limited, but from the viewpoint of scratch resistance and dubbing resistance, it is 0.005 to 3 μm, preferably 0.01 to 2 μm. More preferably 0.02
˜1 μm. Furthermore, in the case of containing mono-dispersed particles in addition to θ-type alumina particles and zirconia particles at the same time,
The relationship between the thickness t of the film layer and the particle diameter d of the monodisperse particles is 0.2d ≦ t ≦ 10d, preferably 0.5d ≦ t ≦.
5d, more preferably 0.5d ≦ t ≦ 3d,
Particularly, scratch resistance and dubbing resistance are improved, which is preferable.

The polymer constituting the layers other than the film layer containing the at least two kinds of particles in the laminated constitution 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-naphthalene
It is preferable to use at least one structural unit selected from the group G as the main constituent because the scratch resistance and the dubbing resistance will be better. Among them, polyesters containing ethylene terephthalate as a main constituent are particularly preferable because the dubbing resistance and scratch resistance are further improved.

The particles may be contained in the polymer constituting the layers other than the film layer containing the at least two kinds of particles in the laminated constitution. In this case, calcium carbonate, alumina, silica, titanium, carbon black and the like are preferably exemplified.

Further, in the biaxially oriented film of the present invention, it is preferable that the number of projections on at least one surface is 2 × 10 ^{3 to} 5 × 10 ⁵ pieces / mm ² from the viewpoint of dubbing resistance and scratch resistance. The number of projections on at least one side is preferably 3 × 10 ³ to 4 × 10 ⁵ pieces / mm ² , and more preferably 5 × 10 ^{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, polyester and θ type alumina particles,
As a method for incorporating the zirconia particles and / or the monodisperse particles, it is preferable to disperse the diol component in ethylene glycol as a slurry and polymerize the ethylene glycol with a predetermined dicarboxylic acid component. Further, a method of directly mixing an aqueous slurry of particles with a predetermined polyester pellet and kneading the polyester into a polyester 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 during film formation.

Next, pellets containing a predetermined amount of particles are dried, if necessary, and then fed to a known extruder for melt lamination, extruded in a sheet form from a slit die, and cast on a casting roll. It is cooled and solidified with to make an unstretched film. That is, two or three extruders, two or three layers of manifolds or merging blocks are used to laminate the polyester in the molten state. In this case, a method of installing a static mixer and a gear pump in the polymer channel containing the above particles is effective for further improving the effect of 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, but a sequential biaxial stretching method in which stretching is first performed in the longitudinal direction and then in the width direction is preferable. The stretching in the longitudinal direction is carried out at a temperature of 85 to 135 ° C. in three or more stages, a total magnification of 3.0 to 6.5 times, and a stretching speed of 5,000.
It is preferably carried out in the range of up to 50,000% / min. As a stretching method in the width direction, a method using a stenter is preferable, the temperature is 80 to 160 ° C., the magnification is 3.0 to 5.0 times, and the stretching speed.
It is preferably performed in the range of 1,000 to 20,000% / min.

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

[0028]

[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 and secondary particle size The cross section of the film was examined by using a transmission electron microscope (TEM).
Observe at over 100,000 times. TEM section thickness is about 100n
m, and change the place to measure 100 fields or more. The primary particle size is the average value of equivalent circular equivalent diameters of the smallest unit that cannot be divided, and the secondary particle size is the aggregate.

(2) Particle size of monodisperse particles The polymer is removed from the film by a plasma low temperature ashing method to expose the particles. The processing conditions are such that the polymer is incinerated but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM) and the particle image is processed with an image analyzer. The magnification of SEM is approximately 2000 to 10000 times, and the visual field in one measurement is appropriately selected from approximately 10 to 50 μm on each side. The volume average diameter d is obtained from the particle diameter and its volume fraction when the number of particles is 5,000 or more by changing the observation location.

D = .SIGMA.di.multidot.Nvi where di is the particle size and Nvi is the volume fraction thereof.

When the particles are significantly damaged by the plasma low temperature ashing method, the following method may be used.
Using a transmission electron microscope (TEM) to examine the cross section of the film, 3
Observe at 000 to 100,000 times. The TEM section thickness is set to about 1000 Å, and the location is changed to 50 Å.
The measurement is performed for 0 fields or more, and the volume average diameter d is calculated from the above formula.

(3) Content of Particles A solvent in which the polyester is dissolved but the particles are not dissolved 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.

(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, N2 and N3 are used, it can be used as a criterion that the absolute value of (N1 -N2) is 0.07 or less and N3 / [(N1 + N2) / 2] is 0.95 or less. 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. The Ramanor U-1000 manufactured by Jobin-Yvon was used for the measurement of laser total reflection Raman.
Raman system measures the total reflection Raman spectrum, for example in the case of PET, 1615 cm ^-1 (skeletal vibration of benzene ring) and 1730 cm ^-1 polarimetry ratio of the band intensity ratio (stretching vibration of carbonyl group) (YY / XX ratio, etc. where YY: Raman light detection parallel to Y with laser polarization direction Y, XX: Raman light detection parallel to X with laser polarization direction X) is the molecular orientation. Correspondence is available. 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.
The total reflection Raman crystallization index of the surface was defined as the half-value width of 1730 cm ^-1 , which is the stretching vibration of the carbonyl group. The measurement conditions in this case are as follows.

Light source Argon ion laser (5145A) Setting of sample The surface of the film was pressed onto a total reflection prism, and the incident angle (angle with the film thickness direction) of the laser on the prism was 60.
It was ゜.

Detector PM: RCA31034 / Photon Counting System (Hamamatsu C1
230) (supply 1600V) Measurement condition SLIT 1000 μm LASER 100mW GATE TIME 1.0sec SCAN SPEED 12cm ^-1 / min SAMPLING INTERVAL 0.2cm ^-1 REPEAT TIME 6

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

(6) Layer Thickness While etching from the surface, the depth profile of the particle concentration is measured by XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy), confocal microscope or the like. In the surface layer of the film laminated on one side, 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 laminated on one side of the present invention, the particle concentration once reaching the maximum value at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth [II] (here, II> I), which is 1/2 of the maximum particle concentration, was defined as the layer thickness. Further, when inorganic particles are contained, a secondary ion mass spectrometer (SIMS) is used to measure the concentration ratio of the element derived from the highest concentration of particles in the film and the carbon element of polyester. (M ⁺ / C
⁺ ) Is used as the particle concentration, and analysis is performed in the depth (thickness) direction from the surface of the polyester A layer. Then, the laminated thickness is obtained from the same method as described above. Alternatively, it can be obtained by observing the cross section of the film or a thin film step measuring machine.

(7) Number of protrusions on the film surface 2 Detector type scanning electron microscope [ESM-3200,
Elionix Co., Ltd.] and cross-section measuring device [PMS-1,
Elionix Co., Ltd.], the height of the flat portion of the film surface is set to 0, and the height of the projection when scanned is measured by an image analyzer [IBAS2000, Carl Zeiss Co., Ltd.].
Manufactured] to reconstruct the film surface protrusion image. Next, for each projection obtained by binarizing the projection part in this surface projection image, the position is changed and repeated 500 times,
The number of protrusions was calculated. The scanning electron microscope (SEM) magnification is selected to be a value between 1000 and 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (WY
KO TOPO-3D, objective lens: 40-200
Height information obtained by using a double high-resolution camera is effective) may be used instead of the SEM value.

(8) Scratch resistance A film obtained by slitting a tape in a width of 1/2 inch was placed on a guide pin (surface roughness: Ra of 100 nm) using a tape running tester. Run (travel speed 25
0 m / min, 1 pass, wrapping angle: 60 °, running tension: 90 g). 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), after calendering at a temperature of 70 ° C. and a linear pressure of 200 kg / cm, curing is performed at 70 ° C. for 48 hours. The above tape raw fabric was slit into 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-methyl isobutyl ketone: 75 parts-toluene: 75 parts-carbon black: 2 parts-lauric acid: 1.5 parts by weight A 100% chroma signal is recorded by the generator, and the chroma S / N is measured from the reproduced signal by a color video noise measuring instrument.
And The master tape pancake on which the same signal as above was recorded was dubbed to the same sample tape (unrecorded) pancake on which A was measured using a magnetic field transfer type video software high-speed printing system (sprinter). The chroma S / N of the subsequent tape was measured in the same manner as above, and B
And Chroma S / N decrease due to this dubbing (A-
When B) was less than 3 dB, dubbing resistance was excellent: when 3 dB or more and less than 5 dB, it was judged to be good, and 5 dB or more was judged to be poor. Good is desirable, but good is practically usable.

[0044]

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

Example 1 (Tables 1 and 2) θ-type alumina and zirconia were dispersed in ethylene glycol, and the ethylene glycol slurry was polymerized with terephthalic acid to prepare master pellets of polyethylene terephthalate containing particles. Further, a water slurry of crosslinked organic particles having a degree of crosslinking of 81% was directly kneaded into polyethylene terephthalate pellets using a vent type twin-screw kneading extruder to obtain polyethylene terephthalate master pellets.

These polymers were mixed in appropriate amounts (polymer A: no particles, θ-type alumina, zirconia, crosslinked organic particles, polymer B: no particles), dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, and then extruded. It was supplied to the extruder 1 and the extruder 2 and melted at 285 ° C and 280 ° C. After high-precision filtration of these polymers, two layers were laminated at the rectangular junction (A /
B).

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. Further, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the thermoplastic resin A layer.

This unstretched film was stretched 3.5 times in the longitudinal direction at a temperature of 85 ° C. This stretching was carried out in four stages with the peripheral speed difference between each pair of two rolls. This uniaxially stretched film was stretched 4.5 times in the width direction at 100 ° C. at a stretching rate of 2,000% / min using a stenter and heat-treated at 200 ° C. for 3 seconds under a constant length to give a total thickness of 7.4 μm. A biaxially oriented laminated film was obtained. The characteristics of this film are as shown in Tables 1 and 2, and the scratch resistance and dubbing resistance were good.

Examples 2 to 3 and Comparative Examples 1 to 4 (Table 1 and Table 2) In the same manner as in Example 1, films were obtained in which the kind of particles, the addition amount, the laminated constitution and the like were changed. As shown in Tables 1 and 2, the films in the range of the present invention have good scratch resistance and dubbing resistance, but those that do not satisfy both scratch resistance and dubbing resistance.

[0050]

[Table 1]

[Table 2]

[0051]

According to the biaxially oriented film of the present invention, θ
Since two specific types of particles, i.e., type alumina particles and zirconia particles, are mixed, the film surface is not easily scratched, and when used for a magnetic medium, excellent image quality and dropout characteristics can be obtained.

Claims (4)

[Claims] 1. A biaxially oriented film comprising θ-alumina particles having a primary particle diameter of 5 to 100 nm and zirconia particles having a primary particle diameter of 5 to 100 nm. 2. The biaxially oriented film according to claim 1,
A biaxially oriented film, which is laminated as one outermost layer of a laminated film having at least a two-layer structure. 3. The biaxially oriented film according to claim 1,
A biaxially oriented film, which is laminated as one outermost layer of a laminated film having at least a three-layer structure. 4. The biaxially oriented laminated film according to claim 1, further comprising, in addition to the at least two types of particles, at least one type of monodisperse particles having a particle size of 0.1 to 2 μm.