JPH05293939A - Laminated film - Google Patents

Abstract

PURPOSE:To enhance the high speed cutting property of the surface of a film by adding specific particles to the outermost layer on the single surface side of a laminated structure consisting of three or more layers so as to satisfy the relation between a specific average particle size and the thickness of the outermost layer and also adding inorg. particles to an intermediate layer. CONSTITUTION:A laminated film is a polyester film having a laminated structure consisting of at least three or more layers formed by coextrusion and particles are added to at least the layer on the single surface side of the laminated structure. The relation between the average particle size d(nm) of particles and the thickness t(nm) of the layer is 0.2<=t/d<=10 and the particles are based on tungsten trioxide. 0.01-2wt.% of at least one kind of inorg. particles are added to an intermediate layer. The inorg. particles added to the intermediate layer are composed of tungsten trioxide, silica or titanium oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film,
In particular, it relates to a laminated polyester film having a laminated structure of three or more layers.

[0002]

As a biaxially oriented laminated film, for example, a biaxially oriented laminated polyester film in which polyester contains substantially spherical silica particles derived from colloidal silica is known (for example, JP-A-59-59). 171
623).

However, with the increase in the process speed of the film processing process, particularly the magnetic layer coating / calendering / winding process in a magnetic medium application, the cassette assembling process, etc., the film surface, especially minute irregularities, is formed on the film by the contacting rolls or guides. There was a drawback that the film surface was easily scraped off. Further, the conventional one has a drawback that the image quality, that is, the S / N (signal / noise ratio) is insufficient because the image quality is deteriorated during dubbing as the dubbing speed is increased by high-speed magnetic field transfer.

In order to eliminate such drawbacks with respect to abrasion resistance and electromagnetic conversion characteristics, the outermost layer of the laminated film is made to be a thin layer, and particles having a relatively large particle diameter relative to the layer thickness are contained. There is proposed a biaxially oriented laminated film in which minute projections which are difficult to be scraped off are formed on the film surface by making the particle diameters of the particles and particles have a specific relationship (Japanese Patent Laid-Open No. 2-77431).

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
To further improve the technology proposed in Japanese Patent No. 77431,
In particular, it is an object of the present invention to provide a laminated film which has further improved abrasion resistance at high speed (hereinafter, also referred to as high-speed abrasion resistance), and further improved dropout characteristics when used as a magnetic tape.

[0006]

The laminated film of the present invention for this purpose is a polyester film having a laminated structure of at least three layers which are coextruded, and contains particles in at least one side layer. , The relationship between the average particle diameter d (nm) of the particles and the layer thickness t (nm) of the layer is 0.2.
≦ t / d ≦ 10, the particles are particles containing tungsten trioxide as a main component, and the intermediate layer contains at least one kind of inorganic particles in an amount of 0.01 to 2% by weight.

First, the laminated film of the present invention must have a laminated structure of at least three layers. If the number of layers is 3 or more, 4 or 5 layers may be used, but a three-layer structure is preferable because the effect of the present invention is further improved. But,
With a single-layer or double-layer film, it is difficult to obtain the target high-speed shaving property and good dropout characteristics when used as a magnetic tape.

The laminated structure of three or more layers is formed by coextrusion. That is, so that the predetermined thickness ratio,
The polymer is laminated in three or more layers by a polymer merging block or a spinneret, discharged into a sheet, and then formed into a film.

Next, in the laminated film of the present invention, it is preferable that at least one of the layers constituting the laminated film is biaxially oriented. It is particularly preferable that all layers in the laminated structure of three or more layers are biaxially oriented. It is difficult to satisfy the characteristics of the present invention when all layers are non-oriented or uniaxially oriented.

The polymer constituting the laminated film of the present invention is polyester, and the polyester is not particularly limited, but ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,
It is particularly preferable when at least one structural unit selected from 4'-dicarboxylate and ethylene 2,6-naphthalate units is the main constituent. Of these, polyesters containing ethylene terephthalate as a main constituent are particularly preferable. Incidentally, within the range that does not inhibit the present invention,
Two or more kinds of polyesters may be mixed, or a copolymer polymer may be used.

In the outermost layer on at least one side of the film having a laminated structure of three or more layers, particles have a relationship between the average particle diameter d (nm) of the particles and the layer thickness t (nm) of the outermost layer. Is contained so that 0.2d ≦ t ≦ 10d. When t is smaller than 0.2d, running property is deteriorated, and when t is larger than 10d, high-speed shaving property is deteriorated and image quality when formed into a magnetic tape is deteriorated, and it is difficult to obtain good dropout characteristics.

In the magnetic tape, it is preferable to lower the coefficient of friction of the magnetic surface and / or the surface opposite to the magnetic surface in order to maintain good running properties. It is preferable to control the number of protrusions within a predetermined range. That is, the number of the protrusions is 3 × 1
The range of 0 ^{3 to} 1.5 × 10 ⁵ pieces / mm ² is preferable.

The particles contained in the outermost layer on at least one side are particles containing tungsten trioxide as a main component. By specifying the particles in this way, a predetermined number of protrusions that are difficult to be scraped off are efficiently formed on the film surface.

Further, in the laminated film of the present invention,
In the laminated structure of three or more layers, the intermediate layer also contains at least one kind of inorganic particles in an amount of 0.01 to 2% by weight. By containing inorganic particles in the intermediate layer, voids are appropriately generated in the intermediate layer, and when the magnetic tape is slit, the cutting edge becomes sharp and the generation of cutting chips is suppressed, and the magnetic tape has good dropout characteristics. Kept in. If the intermediate layer does not have a proper void, the cut end is apt to be jagged, and cutting chips are likely to be generated, resulting in defective dropout.

The inorganic particles contained in the intermediate layer are at least one selected from tungsten trioxide, calcium carbonate, silica, alumina, zirconia and titanium oxide.
It is preferred that it is a type of particles. Since the inorganic particles are not essentially for forming surface protrusions, they may be contained in a small amount of 0.01 to 2% by weight as described above.
However, since the outermost layer is a thin layer, the particles containing the intermediate layer also promote the formation of surface protrusions to some extent.

In the laminated film of the present invention, different polymers may be blended within the range not impairing the object of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. The organic additive may be added to the extent that it is usually added.

Next, the method for producing the film of the present invention will be described for the case of polyester film. First, as a method for incorporating particles into the polyester, for example, a method is preferred in which particles are dispersed in a predetermined ratio in ethylene glycol, which is a diol component, and the ethylene glycol is polymerized with a predetermined dicarboxylic acid component. When adding particles, for example, when the particles are added without drying the water sol or alcohol sol obtained at the time of synthesis, the dispersibility of the particles is very good, and high-speed sharpness,
The electromagnetic conversion characteristics can both be improved. Further, a method in which an aqueous slurry of particles is directly mixed with a predetermined polyester pellet and supplied to a vent type twin-screw kneading extruder and kneaded into polyester is also very effective in further improving the effect of the present invention. As a method of adjusting the content and number of particles, a high-concentration particle master is prepared by the above method, and the particle content is adjusted by diluting it with a polyester that does not substantially contain particles during film formation. The method is effective.

Next, the polyester pellets are used to form a polyester film having a laminated structure of three or more layers. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried and then fed to a known melt laminating extruder, extruded into a sheet from a slit die, and solidified by cooling on a casting roll. At the very least make an unstretched film. That is, using two or more extruders, three or more layers of manifolds or merging blocks (for example, a merging block having a square merging portion), a film layer forming each outermost layer and a film layer forming an intermediate layer are used. Are laminated, and three or more sheets are extruded from the die and cooled with a casting roll to prepare an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer channel is effective. Also, the melting temperature of the extruder for extruding the polymer on the outermost layer side is 5% from the base layer side.
It is effective to lower the temperature by -10 ° C.

Next, the 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, a sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction is used, and stretching in the longitudinal direction is performed in three or more stages, and the total longitudinal stretching ratio is 3.5 to 6.5 times. The method is particularly preferred. The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generally stated, but usually the first step is 50 to 1
It is effective to set the temperature to 30 ° C. and raise the temperature from the second stage onward. The longitudinal stretching speed is 5000 to 50000% /
The range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The draw ratio is 3.0
The range of up to 5.0 times is appropriate. The stretching speed in the width direction is
The range of 1000 to 20000% / min and the temperature of 80 to 160 ° C are suitable. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., especially 1
The range of 80 to 200 ° C. and the time of 0.2 to 20 seconds are suitable.

[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) Average particle size and number of 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 the SEM is approximately 2000 to 10,000 times, and the visual field for 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 with the number of particles of 5000 or more by changing the observation location. d = Σd _i · Nv _i where d _i is the particle size and Nv _i is the volume fraction thereof. The number of particles is calculated from the volume fraction and converted per mm ² for those satisfying the relationship between the laminated thickness and the average particle diameter. When the particles are organic particles or the like and are significantly damaged by the plasma low temperature ashing method, the following method may be used. Using a transmission electron microscope (TEM), the film cross section is 30
Observe at 00-100,000 times. The section thickness of the TEM is set to about 1000Å, the location is changed and 500 or more visual fields are measured, and the volume average diameter d is obtained from the above formula.

(2) Thickness of laminated polyester layer (thickness of outermost layer: t) Using a secondary ion mass spectrometer (SIMS), the highest thickness of the particles in the film in the range of 3000 nm from the surface layer to the depth The concentration ratio (M ⁺ / C ⁺ ) of the element due to the concentration of particles and the carbon element of polyester is defined as the particle concentration, and the 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 depth at which the surface layer particle concentration becomes ½ of the maximum value (this depth is deeper than the maximum value) was determined and used as the laminated thickness. The conditions are as follows. Measuring instrument Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measuring conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12KV Primary ion current: 200nA Raster area: 400μm □ Analysis area: Gate 30% Measured vacuum degree: 6.0 × 10 ^-9 Torr E-GUN: 0.5KV-3.0A If the most contained particles in the depth range from the surface layer to 3000 nm are organic polymer particles, SIMS Since it is difficult to measure with XPS (XPS (X
The layer thickness may be obtained by measuring a depth profile similar to the above by line photoelectron spectroscopy), IR (infrared spectroscopy), or the like, or by observing a cross section with an electron microscope or the like, the state of change in particle concentration or polymer It is also possible to recognize the interface from the difference in contrast due to the difference and obtain the laminated thickness. Furthermore, after peeling the laminated polymer, the laminated thickness can be obtained using a thin film step measuring machine.

(3) Number of protrusions on the film surface The film surface of the film was measured using a two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Co., Ltd.] and a cross-section measuring device [PMS-1, manufactured by Elionix Co., Ltd.]. The measurement value of the height of the projection when scanning is performed with the height of the flat surface set to 0 is sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] to reconstruct a film surface projection image on the image processing apparatus. Next, the highest value among the individual projections obtained by binarizing the projections in this surface projection image is taken as the height of the projection, and this is calculated for each projection. This measurement was repeated 500 times at different places, and the number of protrusions was determined using protrusions having a height of 20 nm or more. The magnification of the scanning electron microscope is selected to be 1000 to 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (WY
KO TOPO-3D, objective lens: 40-200
The height information obtained by using a double high-resolution camera is effective) may be used instead of the value of the SEM.

(4) High-speed shaving property A film is slit into a tape having a width of 1/2 inch, a single blade is pressed at an angle of 90 °, and the film is pushed 0.5 mm to run for 200 m (speed: 200 m / min, tension: 10
0 g). The adhesion height of the powder scraped off by the single blade was read with a microscope and taken as the scraped amount (μm). This abrasion amount is 18 μm
In the following cases, the abrasion resistance is good, and when it exceeds it, the abrasion resistance is poor.

(5) Dropout evaluation on magnetic tape A VTR was used for the tape, and a signal from a TV test signal generator (TG-7 / 1 type manufactured by Shibasoku) was recorded, and then 25
100 passes at 120 ° C and 50% RH (120 minutes x 100 passes)
I made it run. Using a dropout counter, a tape having a dropout width of 5 μsec or more and a reproduced signal attenuation of −16 dB or more was picked up as a dropout. The measurement was performed for 10 rolls, and the number of dropouts converted per minute was 1
When the number was less than 0, the dropout was good, and when the number was 10 or more, it was bad.

[0025]

EXAMPLES Next, the embodiments of the present invention will be described based on examples. Examples 1 to 4 and Comparative Examples 1 to 4 Several kinds of particles having different particle diameters were dispersed in ethylene glycol in the form of a slurry, transesterified with dimethyl terephthalate, and then polycondensed to give a predetermined amount of the particles. The contained polyethylene terephthalate (hereinafter abbreviated as PET) was prepared. In addition, PET was produced by a conventional method without containing substantially inert particles. These polymers were mixed in appropriate amounts to adjust the particle concentration, and dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours. With the combinations shown in Table 1, these were fed to two extruders, melted at 290 ° C, and
A rectangular confluent block (feed block) for layers was combined and laminated, and was wound around a casting drum having a surface temperature of 30 ° C. by an electrostatically applied casting method to be cooled and solidified to form an unstretched film having a three-layer structure. .. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the polyester A layer. This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed by the difference in peripheral speed between the two sets of rolls. This uniaxially stretched film was stretched at a stretching rate of 2000% / min at 100 ° C. in a width direction of 4.0 using a stenter.
The film was double-stretched and heat-treated at 200 ° C. for 5 seconds under a constant length to obtain a biaxially oriented laminated polyester film having a total thickness of 14 μm. All of the laminated constitutions were a three-layer constitution of A layer / B layer / A layer.

High-speed sharpness of these films (characteristic 1)
And the dropout (property 2) when the magnetic tape was used are as shown in Table 1, and the film satisfying the requirements of the present invention had good high-speed shaving property and good dropout when the magnetic tape was used. If this requirement was not met, a film that had both high-speed abrasion and dropout when used as a magnetic tape could not be obtained.

[0027]

[Table 1]

[0028]

According to the laminated film of the present invention, it is specified that the outermost layer on at least one side of the laminated structure of at least three layers satisfies a specific particle average particle diameter and the layer thickness of the outermost layer. Since the above particles are contained and the inorganic particles are also contained in the intermediate layer, it is possible to further improve the high-speed sharpness of the film surface and further improve the dropout characteristics when the magnetic tape is formed.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area B29L 7:00 4F 9:00 4F

Claims (3)

[Claims] 1. A polyester film comprising a coextruded laminated structure of at least three layers, wherein particles are contained in a layer on at least one side of the polyester film, and the average particle diameter d of the particles.
(Nm) and the layer thickness t (nm) of the layer have a relation of 0.2 ≦
t / d ≦ 10, the particles are particles containing tungsten trioxide as a main component, and the intermediate layer contains 0.01 to 2% by weight of at least one kind of inorganic particles. .. 2. The laminated film according to claim 1, wherein the inorganic particles in the intermediate layer are at least one kind of particles selected from tungsten trioxide, calcium carbonate, silica, alumina, zirconia and titanium oxide. 3. The number of surface protrusions on at least one side is 3 × 1.
0 ^{3 to} 1.5 × 10 ⁵ pieces / mm ^{2 3.}
Laminated film.