JP2576321B2 - Biaxially oriented laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated film.

[0002]

2. Description of the Related Art As a biaxially oriented laminated film, for example, a biaxially oriented polyester film, a film in which a polyester contains substantially spherical silica particles originating from colloidal silica is known (for example, see Japanese Patent Application Laid-Open No. H10-163,873). 59
171623).

[0003]

However, as the processing speed of the film processing step, especially the application of a magnetic layer for magnetic media, such as the coating and calendering of a magnetic medium, the winding step, and the cassette assembling step, increases, the film surface is contacted by rolls and guides that come into contact. ,
In particular, there is a disadvantage that the film surface having minute irregularities is easily scraped off. Further, the conventional one has a disadvantage that the image quality, that is, the S / N (signal / noise ratio) is insufficient because the image quality at the time of dubbing decreases due to the increase in dubbing due to high-speed magnetic field transfer or the like.

The present invention solves such a problem, and in particular, the film surface is hardly scraped off in a high-speed process (hereinafter referred to as excellent in high-speed shaving property). That is, an object of the present invention is to provide a biaxially oriented laminated film having good electromagnetic conversion characteristics (hereinafter referred to as excellent in electromagnetic conversion characteristics).

[0005]

A biaxially oriented laminated film according to the present invention for this purpose has a laminated structure of at least three layers, and has at least three layers on at least one surface thereof.
A biaxially oriented laminated film containing particles A, B, and C, wherein the particles A are particles having a primary particle diameter of 1 to 100 nm selected from zirconia, chain silica or alumina, and particles B Is calcite-type calcium carbonate having a primary particle size of 0.1 to 2 μm and a content of 0.005 to 2% by weight, and the particle C is a primary particle selected from colloidal silica, crosslinked organic particles, and vaterite-type calcium carbonate. Particles having a particle size of 0.1 to 2 μm and a content of 0.005 to 2% by weight, wherein the relationship between the particle size d of the particles B and the thickness t of the layer containing the particles B is 0. .5d ≦ t ≦ 5d.

First, the film of the present invention needs to have a laminated structure of at least three layers. If there are three or more layers,
Four or five layers may be used, but a three-layer structure is preferable because the effects of the present invention are further improved. However, a film having a single-layer or two-layer structure cannot satisfy high-speed shaving properties and electromagnetic conversion characteristics.

Next, in the film of the present invention, it is necessary that at least one of the layers constituting the film is biaxially oriented. It is particularly preferable that all the layers of the three or more layered structure are biaxially oriented. If all the layers are non-oriented or uniaxially oriented, the properties of the present invention cannot be satisfied.

[0008] The polymer constituting the biaxially oriented laminated film of the present invention is not particularly limited, but polyester is preferred for use in magnetic media. The polyester is not particularly limited, but ethylene terephthalate, ethylene α,
β-bis (2-chlorophenoxy) ethane-4,4′-
It is particularly preferred when at least one structural unit selected from dicarboxylate and ethylene 2,6-naphthalate units is the main constituent. Among them, a polyester containing ethylene terephthalate as a main component is particularly preferable. In addition, two or more types of polyesters may be mixed or a copolymer may be used within a range not to impair the present invention.

In the biaxially oriented laminated film of the present invention, at least one type of particles A,
B and C are contained. The particles A are composed of particles having a relatively small particle diameter, and mainly serve to reinforce the surface of the outermost layer. The particles B are composed of particles having a larger particle size than the particles A, and form projections on the surface of the outermost layer portion, and play a role of improving high-speed running while improving abrasion resistance. Particle C
Has a role of forming lower surface projections than the particles B, further improving the effect of surface roughening, further reducing the friction coefficient, and further improving the high-speed running property of the film.

The particles A are selected from zirconia, chain silica, or alumina particles. With this material, the ground of the outermost layer is effectively reinforced. The average primary particle size of the particles A is 1 to 100 nm, more preferably 10 to 40 n.
m. When the primary particle size is smaller than 1 nm, the background reinforcing effect is weakened, and when the primary particle size is larger than 100 nm, a surface projection forming effect appears, and high-speed shaving property may be deteriorated.

From the viewpoint of the background reinforcing effect, the particles A
It is desirable that the particles are aggregated to some extent. The particle size in the agglomerated state, that is, the secondary particle size is 3 in the ratio of secondary particle size / primary particle size.
When it is in the range of ~ 60, the ground of the outermost layer is effectively reinforced. Monodisperse or close to it, ie secondary particle size /
When the ratio of the primary particle diameters is less than 3, the effect of improving the ground reinforcement by the aggregation of the particles is almost eliminated. If the ratio exceeds 60, the aggregated particles become too large, and they form fragile projections, deteriorating high-speed scraping.

The content of the particles A is preferably from 0.05 to
It is 2% by weight, more preferably 0.1 to 1% by weight. If the content is less than 0.05% by weight, the density of the particles in the layer becomes too low, so that the expected background reinforcing effect may not be obtained. If the content exceeds 2% by weight, the amount of particles becomes too large, and the layer may be brittle.

Since the particles A are responsible for the background reinforcing effect as described above, it is desirable that the particles A are gathered particularly near the surface in the outermost layer. By doing so, the background on the surface of the outermost layer is effectively reinforced, and the effect of including the particles A is remarkably exhibited. In the present invention, the surface layer particle concentration is used as an index in order to quantitatively express how much particles A are gathered near the surface. When the surface particle concentration of the particles A is 0.1 or more, the above-described background reinforcing effect becomes remarkable.

The particles B are calcite-type calcium carbonate particles. By specifying the particle material, surface projections that are difficult to cut are efficiently formed. Calcite-type calcium carbonate exists as a natural material such as calcite having a hexagonal crystal form, and has a stable natural crystal form. Since there is no deterioration or the like, even if a mechanical or thermal load such as stretching of the film is applied, it can contribute to the formation of surface projections stably. Therefore, stable surface projections that are hard to be removed are formed. The calcite calcium carbonate has a density of about 2.71 g / cm ³ and a relatively large birefringence of 1.658.

The average primary particle size of the particles B is 0.1 to 2 μm.
And more preferably 0.6 to 1 μm. 0.1
If it is smaller than μm, the height of the formed projections becomes too low, and the effect of reducing the friction coefficient becomes small, so that good running properties cannot be obtained. If it exceeds 2 μm, the height of the projections becomes too high, so that high-speed shaving is inferior.

The content of the particles B is 0.005 to 2% by weight, more preferably 0.2 to 0.5% by weight. If the content is less than 0.005% by weight, the number of surface projections becomes too small, so that the contact area of the background other than the projections becomes too large, the friction coefficient becomes high, and the running property deteriorates.
Conversely, if it exceeds 2% by weight, the number of particles becomes too large, the layer itself becomes brittle, and the particles may easily fall off.

The particles B are contained in at least one of the outermost layers to form projections on the surface of the layer. All particles B
However, in a state where the particles are completely buried in the layer, surface projections are hardly formed. Therefore, in order to form desired surface projections by containing particles B, the particle diameter of particles B and the particle It is necessary to specify a relative relationship between the thickness of the layer to be formed. In the present invention, the relationship between the primary particle size d of the particles B and the thickness t of the layer containing the particles B is set to 0.5d ≦ t ≦ 5d. By setting the relative relationship within this range, the surface protrusions having a uniform height and a desired height are formed by the particles B. By this uniform desired surface projection formation,
Electromagnetic conversion characteristics are improved together with high-speed shaving.

The particles C are selected from colloidal silica, crosslinked organic particles and vaterite-type calcium carbonate particles. Since particles of such a material are relatively easy to have a uniform particle size, surface protrusions are formed such that protrusions formed by particles having a uniform particle size compensate for protrusions formed by particles B. That is, relatively high projections are formed by the particles B, and the projections of the particles are formed so as to supplement (be placed between or on the projections), so that the surface is more uniform and coarse. The surface is roughened without forming projections, the friction coefficient is significantly reduced, and excellent running properties are obtained. Further, since the particles C of such a material have a high affinity with a film base material such as polyester, the particles B
Can be reinforced. Of the above materials,
Vaterite-type calcium carbonate has a hexagonal crystal form and is found only in a kind of snail in the natural world, and is usually manufactured as a synthetic product. The synthesis is usually carried out in alcohol since it becomes calcite-type under heating or in the presence of water. Synthetic products are uniform in quality, but are unstable (high in activity) and have high affinity with polyester and the like. The density is about 2.54 g / cm ³ and the birefringence is as small as 1.550. In particular, in the present invention, the uniform quality, uniform particle size, and high affinity with polyester and the like are effectively used, and the particles C form projections smaller than the projections by the particles B and hard to be cut at a uniform height. Is done. The crosslinked organic particles are also easily formed into a uniform particle size, and have an extremely high affinity for a film base material such as polyester. Examples of the material of the crosslinked organic particles include crosslinked polystyrene and crosslinked divinylbenzene.

The average primary particle size of the particles C is also 0.1 to 2 μm.
And more preferably 0.6 to 1 μm. 0.1
If it is smaller than μm, the height of the projections formed is too low, and the effect of improving running properties is reduced. If it exceeds 2 μm, a portion protruding from the projections due to the particles B is formed, and the high-speed scraping property may be deteriorated.

The content of the particles C is 0.005 to 2% by weight, more preferably 0.2 to 0.5% by weight. If the content is less than 0.005% by weight, the number of projections due to the particles C becomes too small, so that a running property improving effect cannot be expected. Conversely, if it exceeds 2% by weight, the number of particles becomes too large, the layer itself becomes brittle, and the particles may easily fall off.

Since the surface of the particle C is formed by forming relatively small protrusions so as not to hinder the formation of protrusions by the particles B, the surface of the particle C is made as uniform as possible. Is preferred. For that purpose, it is desirable to provide a regulation based on the particle size distribution of the particles C. In order to make the particle size distribution of the particles C sharp, it is preferable that the particle size distribution be 0.6 or less in relative standard deviation.

Further, in the film of the present invention, the intermediate layer is not particularly limited, but the surface layer is excellent in high-speed scraping properties as described above, and has a uniform projection height at the outermost layer, and has excellent electromagnetic conversion characteristics. Therefore, it is preferable to include a so-called recycled polymer in the intermediate layer. Here, in the case of polyester, for example, in the case of polyester, the terminal carboxylic acid of the polyester is 55 equivalents / 10 ⁶ g or more and the solution haze of the polymer is 18% or less.

In the film of the present invention, different polymers may be blended as long as the object of the present invention is not impaired, and organic films such as antioxidants, heat stabilizers, lubricants and ultraviolet absorbers may be used. It may be added to the extent that additives are usually added.

Next, the method for producing the film of the present invention will be described for the case of a polyester film. First, as a method for incorporating particles A, B, and C into polyester,
For example, a method is preferred in which particles A, B, and C are separately dispersed in a predetermined ratio in the form of a slurry in ethylene glycol, which is a diol component, and the ethylene glycol is polymerized with a predetermined dicarboxylic acid component. When adding the particles, for example, if the water sol or alcohol sol obtained during the synthesis of the particles is added without drying once, the dispersibility of the particles is very good, and the high-speed scraping property and the electromagnetic conversion characteristics are both good. be able to. A method of directly mixing a water slurry of particles with predetermined polyester pellets, supplying the mixture to a vent-type twin-screw kneading extruder, and kneading the resulting mixture with polyester is also very effective for further improving the effects of the present invention. As a method of adjusting the content of particles, a method of preparing a high-concentration particle master by the above method and diluting it with a polyester substantially containing no particles during film formation to adjust the content of particles is known. It is valid.

Next, a polyester film having a laminated structure of three or more layers is formed using the polyester pellets. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried, fed to a known extruder for melt lamination, extruded from a slit die into a sheet, and cooled and solidified on a casting roll. At least make an unstretched film. That is, two or three or more extruders, three or more layers are stacked using a manifold or a merging block (for example, a merging block having a square merging portion),
Three or more layers of the sheet are extruded from a die and cooled by a casting roll to produce an unstretched film. In this case, a method of installing a static mixer and a gear pump in the polymer flow path is effective. Further, it is effective to lower the melting temperature of the extruder for extruding the polymer on the outermost layer laminated portion side by 5 to 10 ° C. than that on the base layer side.

Next, the 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. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction and then in the width direction is performed first, the stretching in the longitudinal direction is divided into 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 unconditionally determined.
It is effective to set the temperature to 30 ° C. and to increase the temperature after the second stage. The longitudinal stretching speed is 5,000 to 50,000% /
A range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. Stretch ratio is 3.0
A range of up to 5.0 times is appropriate. The stretching speed in the width direction is
The temperature is preferably in the range of 1000 to 20000% / min and the temperature is in the range of 80 to 160 ° C. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., particularly 1
The temperature is preferably from 80 to 200 ° C. and the time is preferably from 0.2 to 20 seconds.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows. (1) Average primary particle size of particles A, B and C E. FIG. The specific surface area of the particles was determined by the T method, and the particle diameter when the particles were made into spheres was determined from the specific surface area by the following equation, and this was defined as the average primary particle diameter. Particle size = 6 / (particle density × specific surface area) When it is difficult to measure by this method, the primary particle size can also be obtained by observing the particles with an electron microscope or the like.

(2) Secondary Particle Size of Particle A The film containing the particles is formed into an ultra-thin section perpendicular to the plane of the film and having a thickness of 1000 °, and is measured using a transmission electron microscope (for example, JEM-1200EX manufactured by JEOL Ltd.). Ten
Observe the particles at about 10,000 times, find the equivalent circle diameter of the particles,
The value averaged over the visual field was taken as the secondary particle size of the particles.

(3) Content of Particles A solvent in which the film base material is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the film base material, and the particle content is defined as a ratio (% by weight) to the total weight of the particles. I do.
If necessary, pyrolysis gas chromatography, infrared spectroscopy, fluorescent X-ray analysis, Raman scattering, SEM-X
It can also be determined using MA or the like. The content of the particles in the laminated portion and the base layer portion can be distinguished by shaving each laminated portion. Further, if necessary, it can be calculated from the number of particles observed in each cross section using a TEM.

(4) Surface Particle Concentration Using a secondary ion mass spectrum (SIMS), the concentration ratio of the highest concentration element among the elements originating from the particles in the film to the carbon element of the thermoplastic resin is determined by the following method. The particle concentration was determined at 3 nm from the surface layer in the direction of the direction, and was defined as the particle concentration. measuring device,
The conditions are as follows. Primary ion species: 12 KV Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6.0 × 10 ⁻⁹ Torr E-GUN: 0.5 KV− 3.0A

(5) Thickness of Outermost Layer Using a secondary ion mass spectrometer (SIMS), the concentration ratio (M) of the element resulting from the highest concentration of the particles in the film and the carbon element of the polyester is determined. ⁺ / C ⁺ ) is defined as the particle concentration, and the analysis is performed in the depth (thickness) direction from the surface of the polyester A layer. 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 that has once reached the maximum value at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth at which the particle concentration of the maximum value becomes 1/2 [II]
(Where II> I) was taken as the lamination thickness. In addition, when the particles most contained in the film are organic polymer particles, it is difficult to measure by SIMS. Therefore, while etching from the surface, XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy) or a confocal microscope is used. For example, the depth profile of the particle concentration may be measured, and the layer thickness may be obtained by the same method as described above. Furthermore, it can be obtained not from the above-mentioned depth profile but by observation of a cross section of a film or a thin film step measuring device.

(6) Particle Size Distribution of Particle C The primary particle size was determined for the 1000 particles by the method described in (1) above, and the particle size distribution was represented by the relative standard deviation.

(7) High-speed scalability One edge of the film is slit into a tape having a width of 1/2 inch and pressed at an angle of 90 °, and the film is pushed in by 0.5 mm and run for 200 m (speed: 200 m / min, tension: 10
0 g). The adhering height of the powder shaved on one blade was read with a microscope, and the shaved amount (μm) was determined. This shaving amount is 180μ
When it is less than m, the abrasion resistance is good, and when it exceeds it, the abrasion resistance is poor.

(8) Electromagnetic conversion characteristics A magnetic paint 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), a calendar treatment is performed at a temperature of 70 ° C. and a linear pressure of 200 kg / cm 2, and then curing is performed at 70 ° C. for 48 hours.
The raw tape 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 form 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 part by weight Methyl ethyl ketone : 75 parts by weight-Methylisobutyl ketone: 75 parts by weight-Toluene: 75 parts by weight-Carbon black: 2 parts by weight-Lauric acid: 1.5 parts by weight Using a home VTR on this tape, using a TV test waveform generator A 100% chroma signal was recorded, and the chroma S / N was measured from the reproduced signal using a color video noise measuring instrument. Compare this S / N with a commercially available VHS tape,
It was determined based on the following criteria. +1.5 (dB) or more: excellent 0 (dB) or more, less than +1.5 (dB) : good less than 0 (dB): bad

[0035]

Next, embodiments of the present invention will be described based on examples. Example 1 (Table 1) Zirconia particles having a primary particle diameter of 20 nm as particles A were dispersed in ethylene glycol using glass beads having a diameter of 50 µm as a medium. After removing the glass beads, the resulting mixture was polymerized with terephthalic acid to obtain polyethylene terephthalate. A master pellet was used.

Next, calcite-type calcium carbonate particles having a primary particle size of 0.8 μm as particles B are uniformly dispersed in ethylene glycol using the above-mentioned media dispersion method, and a master pellet of particles B is prepared in the same manner as described above. Obtained.

Colloidal silica particles having a primary particle size of 0.4 μm as particles C were uniformly dispersed in ethylene glycol by the same method, and a master pellet of particles C was obtained in the same manner as described above.

The master pellet of the particle A, the master pellet of the particle B, the master pellet of the particle C, and the pellet of polyethylene terephthalate containing no particles are used.
% By weight and 0.1% by weight, and supplied to the vented twin-screw kneading extruder 1 to dissolve at 280 ° C. (Polymer I). Further, another extruder 2 was prepared, and 30 parts by weight of the recycled polymer and pellets 70 containing no particles were used.
After mixing the parts by weight, the mixture was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours, supplied to an extruder and dissolved at 290 ° C. (Polymer II). These two polymers are each subjected to high-precision filtration, and then, in a three-layer merging block having a rectangular laminated portion, polymer II is laminated on the base layer so that polymer I comes on the double-sided surface laminated portion. And extruded it into a sheet from a die, wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and cooled and solidified to produce an unstretched film having a thickness of about 160 μm. The draft ratio at this time was 6.5.

This unstretched film is divided into three stages in the longitudinal direction, 1.2 times at 123 ° C., 1.45 times at 126 ° C.,
Each was stretched 2.3 times at 14 ° C. This uniaxial film is divided into two stages in the width direction using a stenter, stretched 3.7 times at 111 ° C. and 1.2 times at 113 ° C., and stretched 200 times at a constant length.
C. for 5 seconds to obtain a film having a thickness of 13 .mu.m. The outermost layer portion laminated thickness t of the obtained film is 1.0
In μm, the relation with the particle diameter d of the particles B was t = 2.5d. The average primary particle size of the particles A was 20 nm, and the ratio of secondary particle size / primary particle size was 7. The particle size distribution of the particles C is 0.
It was 5.

When the electromagnetic conversion characteristics of this film were measured, the chroma S / N was +2.3 dB. In addition, the high-speed scraping property was as good as 35 μm. In this manner, when the type of the particles contained in the outermost layer laminated portion, the particle size, the content, and the relationship with the laminated thickness are within the scope of the present invention,
A film having both good electromagnetic conversion characteristics and high-speed scraping properties can be obtained.

Examples 2 to 4, Comparative Examples 1 to 4 (Table 1) In the same manner as in Example 1, the type, particle size, content, particle size distribution and lamination thickness of the particles contained in the outermost layer portion Various changes were made to obtain a biaxially oriented laminated polyester film. If the type of the particles contained in the outermost layer laminated portion, the particle size, the content, the relationship between the particle size distribution and the layer thickness are not within the scope of the present invention, both the electromagnetic conversion characteristics and the high-speed shaving properties are good. And could not.

[0042]

[Table 1]

[0043]

According to the biaxially oriented laminated film of the present invention, at least one surface of the thin layer outermost surface has a predetermined content,
Particles A having a predetermined particle size, a predetermined content, a predetermined particle size, particles B having a predetermined magnitude relationship with the outermost layer thickness, and a predetermined content,
At least three specific particle components of the particles C having a predetermined particle diameter are contained, and the particles A mainly play the role of reinforcing the background, the particles B form the surface projections of a desired height, and the particles C play the role of further roughening the surface. As a result, it is possible to obtain a desirable surface morphology with a strong background, uniform and hard-to-cut projections, and a very low coefficient of friction. As a result, excellent electromagnetic conversion characteristics can be exhibited.

Further, since the outermost layer can have the above-mentioned excellent characteristics, the intermediate layer can contain the recycled polymer without causing any problem, and the productivity can be improved. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B29L 9:00 (56) References JP-A-62-264947 (JP, A) JP-A-4- 278349 (JP, A) JP-A-4-62151 (JP, A)

Claims (5)

(57) [Claims] 1. A biaxially oriented laminated film having a laminated structure of at least three layers and including at least three types of particles A, B, and C in an outermost layer portion of at least one surface thereof. Are particles having a primary particle size of 1 to 100 nm selected from zirconia, chain silica or alumina, and particles B have a primary particle size of 0.1 to 2 μm and a content of 0.005.
２2% by weight of calcite-type calcium carbonate, and particles C have a primary particle size of 0.1 to 2 selected from colloidal silica, cross-linked organic particles or vaterite-type calcium carbonate.
μm, the content of the particles is 0.005 to 2% by weight, the particle diameter d of the particles B and the thickness t of the layer containing the particles B
Wherein 0.5d ≦ t ≦ 5d. 2. The biaxially oriented laminated film according to claim 1, wherein the intermediate layer contains a recycled polymer. 3. The biaxially oriented laminated film according to claim 1, wherein the ratio of secondary particle size / primary particle size of the particles A is 3 to 60. 4. The biaxially oriented laminated film according to claim 1, wherein the relative standard deviation of the particle size distribution of the particles C is 0.6 or less. 5. The biaxially oriented laminated film according to claim 1, wherein the surface particle concentration of the particles A is 0.1 or more.