JP2867789B2 - 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 the magnetic layer in the magnetic medium application, calendering and winding, and the step of assembling the cassette, increases, the film surface, especially minute irregularities, is caused by the contacting rolls and guides. There is a disadvantage that the film surface 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.

[0004] In order to solve such a drawback, the outermost layer of the laminated film is made to be a thin layer, and particles having a relatively large particle diameter are contained in the layer thickness. There has been proposed a biaxially oriented laminated film in which minute projections are formed on the film surface so as to be hardly scraped off by making the relationship (JP-A-2-77431).

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art and discloses a technique disclosed in
The technology proposed in Japanese Patent No. 7431 is further improved to further improve the runnability by further optimizing the minute projections on the film surface, and in particular, when used as a magnetic medium, there is little deterioration in image quality during dubbing and the like, and dropout characteristics are improved. It is an object of the present invention to provide a biaxially oriented laminated film having good (hereinafter, sometimes referred to as excellent in electromagnetic conversion characteristics).

[0006]

According to the present invention, there is provided a biaxially oriented laminated film having a laminated structure of at least three layers, wherein particles are contained in at least one outermost layer of the biaxially oriented laminated film. The relationship between the average particle diameter d (nm) of the particles and the layer thickness t (nm) of the outermost layer is 0.2d ≦ t ≦ 10d, and the height of the projection on the film surface on the outermost layer side is 20n
m or more number of projections is ³ × 10 3 ~2 × 10 ⁵ cells / mm ²
And an intermediate layer containing organic particles.

[0007] In the above biaxially oriented laminated film, above
The number of particles having a particle size satisfying the relationship of 0.2d ≦ t ≦ 10d is 3 × 10 ^{3 to} 1.5 × 1.
0 ⁵ / mm ² der Rukoto is preferable.

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, and cannot obtain good image quality and good dropout 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.

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, the outermost layer on at least one surface of the biaxially oriented laminated film first has particles in the relation 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. If t is smaller than 0.2d, the running property is deteriorated, and if t is larger than 10d, the image quality of a magnetic tape is reduced.

The number of the particles having a particle size satisfying the relationship of the above formula is 3 × 10 ^{3 to} 1.5 × 10 ⁵ / mm ^2.
It is contained so that it becomes. As described above, by setting the number of particles having a particle diameter satisfying the specific relationship between the particle diameter of the particles and the layer thickness of the outermost layer in a specific range, first, the desired fine projections are formed on the film surface by the contained particles themselves. Are formed efficiently.

[0013] In the biaxially oriented laminated film of the present invention, since the intermediate layer contains organic particles, the effect of forming the projections of the intermediate layer-containing organic particles also appears on the outermost layer of the thin layer. The projections are formed in a form in which the projections formed by the outermost layer-containing particles are further added to the projection formation surface by the above, and the desirable projections that are harder to be scraped off and that can exhibit better running properties are formed. If organic particles are not contained in the intermediate layer, dropout at the end of the tape, especially when a magnetic tape is used, increases.

As described above, in addition to the outermost layer-containing particles, the intermediate layer-containing organic particles also have a projection-forming effect. As a result, in the biaxially oriented laminated film of the present invention, the projection height of the outermost layer-side film surface is 20 nm or more. The number of projections is 3 × 10 ³ to 2
× 10 ⁵ pieces / mm ² .

If the number of projections on the outermost film surface is less than the above range, the coefficient of friction becomes high, and good running properties cannot be obtained. Conversely, if the number of protrusions is larger than the above range, the image quality of a magnetic tape will be reduced.

On the other hand, if the number of the outermost layer-containing particles having a particle size satisfying the above formula is smaller than the above range, good running property cannot be obtained. Image quality is deteriorated.

The organic particles contained in the intermediate layer are not particularly limited, but are preferably crosslinked organic particles. In particular, the organic particles are divinylbenzene copolymer particles,
Alternatively, the surface of the organic particles has the general formula “-COOX”
It is preferable that the particles are coated with a polymer having a functional group represented by (X is H, an alkali group, an alkali metal or an alkaline earth metal). More specifically, they are divinylbenzene copolymer particles, silicone particles, butyl acrylate particles and the like.

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 antioxidants, heat stabilizers, lubricants, ultraviolet absorbers and the like may be blended. Organic additives may be added to the extent that they 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 into the polyester, for example, a method is preferred in which particles are dispersed in a predetermined ratio in the form of a slurry in ethylene glycol, which is a diol component, and this ethylene glycol is polymerized with a predetermined dicarboxylic acid component. When adding 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, high-speed scraping,
Both electromagnetic conversion characteristics can be improved. 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 and the number of particles, a high-concentration particle master is prepared by the above method, and the particle master is adjusted by diluting it with a polyester substantially containing no particles during film formation. The method is effective.

Next, a polyester film having a laminated structure of three or more layers is formed by 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, using two or three or more extruders, three or more manifolds or a merging block (for example, a merging block having a square merging portion), a film layer constituting each outermost layer and a film layer constituting an intermediate layer Are laminated, and three or more sheets 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, the melting temperature of the extruder for extruding the polymer on the side of the outermost layer lamination portion is set at 5 from the base layer side.
It is effective to lower by -10 ° C.

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, 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 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 selected so that the polymer is ashed 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 about 2000 to 10000 times, and the visual field in one measurement is appropriately selected from about 10 to 50 μm on one side. The volume average diameter d is obtained from the particle diameter and its volume fraction by the following formula from 5000 particles or more at different observation points. d = Σd _i · Nv _i where d _i is the particle size, Nv _i is its volume fraction. The number of particles is determined from the volume fraction of the particles satisfying the relationship between the layer thickness and the average particle diameter, and is converted into mm ² . If the particles are organic particles or the like and are significantly damaged by the plasma low-temperature incineration method, the following method may be used. The cross section of the film was measured using a transmission electron microscope (TEM).
Observe at a magnification of 100 to 100,000. The thickness of the section of the TEM is about 1000 mm, the measurement is made at 500 places or more at different places, and the volume average diameter d is obtained from the above equation.

(2) Thickness of laminated polyester layer (thickness of outermost layer: t) Using a secondary ion mass spectrometer (SIMS), the highest of the particles in the film in the range from the surface layer to a depth of 3000 nm. The concentration ratio (M ⁺ / C ⁺ ) between the element resulting from the particles and the carbon element of the polyester is defined as the particle concentration, and the analysis in the thickness direction is performed from the surface to 3000 nm in depth. 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 which has once reached the maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration was の of the local maximum value (this depth was deeper than the local maximum value) was determined, and this was defined as the lamination thickness. The conditions are as follows. Measurement device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measurement conditions Primary ion species: O ₂ ⁺ 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-3.0 A SIMS is used when organic particles are most contained in the range from the surface layer to the depth of 3000 nm. Is difficult to measure with XPS (X
Line photoelectron spectroscopy), IR (infrared spectroscopy), etc., the same depth profile as described above may be measured to determine the lamination thickness, or the change in particle concentration and polymer The interface can be recognized from the difference in contrast due to the difference, and the lamination thickness can be determined. Further, after the laminated polymer is peeled off, the laminated thickness can be determined using a thin film step measuring device.

(3) Number and height of projections on the film surface Two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Inc.] and a cross-section measuring device [PMS-1, manufactured by Elionix Inc.] In step (1), the measured height of the projections when scanning was performed with the height of the flat surface of the film surface set to 0, was sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.]. To construct. Next, the highest value among the individual projections obtained by binarizing the projections in this surface projection image is defined as the height of the projection, and this is determined for each individual projection. This measurement was repeated 500 times at different locations, and a projection having a height of 20 nm or more was determined as the number of projections, and the average value of the measured projections was defined as the average height. The magnification of the scanning electron microscope is selected between 1000 and 8000 times. In addition,
In some cases, a high-precision optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40 to 2)
The height information obtained by using (00 times, use of a high-resolution camera is effective) may be replaced with the SEM value and used.

(4) Image Quality (Chroma S / N) A magnetic paint having the following composition is applied to the film by 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.
Slit the above tape into 1/2 inch, length 25
A length of 0 m was incorporated into a VTR cassette to form a VTR cassette tape. (Magnetic paint composition) Co-containing iron oxide (BET value 50 m ² / g): 100 parts by weight Eslek A (vinyl chloride / vinyl acetate copolymer manufactured by Sekisui Chemical): 10 parts by weight Nipporan 2304 (manufactured by Nippon Polyurethane) Polyurethane elastomer): 10 parts by weight-Coronate L (polyisocyanate manufactured by Nippon Polyurethane): 5 parts by weight-Lecithin: 1 part 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 using a home VTR with a Shibasoku TV test waveform generator (TG7 / U706), and the reproduced signal was used as a shivasoku. Chroma S / N was measured with a color video noise measuring instrument (925 D / 1) manufactured by FUJIFILM Corporation.

(5) Runnability (Friction Coefficient μk) A film obtained by slitting a film into a tape having a width of 1/2 inch was used by using a tape runnability tester SFT-700 (produced by Yokohama System Laboratory Co., Ltd.). , 20 ° C., 60% RH atmosphere, and the initial coefficient of friction was determined by the following equation (film width was １ ／ inch). μk = 2 / πln (T ₂ / T ₁ ) Here, T ₁ is the entrance tension, and T ₂ is the exit tension. The guide diameter is 6 mmφ, the guide material is SUS27 (surface roughness 0.2S), the winding angle is 90 °, and the running speed is 3.
3 cm / sec. When μk obtained by this measurement was 0.3 or less, it was determined that the friction coefficient was good, and when it exceeded 0.3, it was determined that the friction coefficient was poor. This μk is a critical point that affects the handling properties when processing the film for magnetic recording media, capacitors, packaging and the like.

(6) Evaluation of Dropout on Magnetic Tape After recording a signal from a TV test signal generator (Shibasoku TG-7 / 1 type) using a VTR on the tape, 25
100 passes at 120 ° C and 50% RH (120 passes x 100 passes)
I ran. Using a drop-out counter, the tape was picked up as a drop-out having a drop-out width of 5 μsec or more and a reproduction signal attenuation of -16 dB or more. The measurement was performed for 10 volumes, and the number of dropouts 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.

[0028]

Next, embodiments of the present invention will be described based on examples. Example 1 (Table 1) Organic particles to be contained in the outermost layer were dispersed in ethylene glycol using glass beads having a diameter of 50 μm as a medium, and after removing the glass beads, polymerization was carried out with terephthalic acid to obtain a polyethylene terephthalate master pellet. did.

Next, divinylbenzene copolymer particles as particles to be contained in the intermediate layer were uniformly dispersed in ethylene glycol using the above-mentioned media dispersion method, and a master pellet containing the particles was obtained in the same manner as described above. .

Each of the above master pellets was diluted at a predetermined ratio with polyethylene terephthalate pellets containing no particles, and dried at 180 ° C. for 8 hours under reduced pressure (3T
orr), and then supplied to an extruder 1 and an extruder 2 (for example, a vent-type twin-screw kneading extruder).
Dissolved at 0 ° C. After each of these two polymers is subjected to high-precision filtration, the divinylbenzene copolymer particle-containing polymer is contained in the intermediate layer and the particle-containing polymer is contained in the double-sided surface layer in a three-layer merging block having a rectangular laminated portion. After being extruded into a sheet form from a fish tail type die, it is wound around a casting drum with a surface temperature of 30 ° C using an electrostatic application casting method, cooled and solidified, and unstretched with a thickness of about 160 μm I made a film. 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 laminated thickness t of the obtained film is 100
At 0 nm, the laminated thickness t of the outermost layer and the average particle size d of the contained particles
And the relationship t / d was 1.5. The number of protrusions on both surfaces is the same, and the number of surface protrusions is 20,000 / mm ^2.
Met. Further, the number of particles having a t / d of 0.2 to 10 is 1
The number was 5000 / mm ² .

When the image quality of the VTR tape made with this film was measured, the chroma S / N was 2.5 dB.
The running property (coefficient of friction) of the film was as good as 0.28. Furthermore, when the dropout at the tape end was evaluated, it was good. As described above, the relationship between the particles contained in the outermost layer laminate and the laminate thickness, the number of particles satisfying the relationship, the number of surface protrusions are within the scope of the present invention, and
When the intermediate layer contains organic particles, excellent image quality, running properties, and dropout characteristics can be obtained.

Examples 2 to 4 and Comparative Examples 1 to 4 (Table 1) In the same manner as in Example 1, the thickness t of the outermost layer and the relationship t between the thickness t of the outermost layer and the average particle diameter d of the contained particles were determined. / D, the number of surface protrusions, the number of particles having a t / d of 0.2 to 10, and the type of the intermediate layer-containing organic particles are variously changed. A biaxially oriented laminated polyester film was prepared (however,
In Example 4, the intermediate layer was a polyethylene naphthalate (PEN) film, and a three-layer laminated structure of a polyethylene terephthalate (PET) film and PET / PEN / PET was used. Comparative Example 4 was a single-layer film. ). The laminated thickness of the outermost layer, the relationship t / d between the laminated thickness t and the average particle diameter d of the contained particles, the number of surface protrusions, and the number of particles having a t / d of 0.2 to 10 are within the scope of the present invention. Yes, and
When organic particles were contained in the intermediate layer, excellent image quality, running properties, and dropout characteristics were obtained (Examples 2 to 4), but when no organic particles were contained in the intermediate layer,
Even if some other conditions were within the range of the present invention, all of the image quality, running properties, and dropout characteristics could not be satisfied (Comparative Examples 1 to 4).

[0034]

[Table 1]

[0035]

According to the biaxially oriented laminated film of the present invention, the outermost layer on at least one side of the laminated structure of at least three layers satisfies the relationship between the specific particle average particle size and the layer thickness of the outermost layer. As described above, the number of surface protrusions or the number of particles having a particle size satisfying the above relationship is set to a specific range, and the intermediate layer contains organic particles. Can be efficiently formed to have a desired surface form, excellent running properties can be exhibited, and excellent image quality and dropout characteristics for a magnetic medium can be obtained.

Continuation of the front page (56) References JP-A-3-210339 (JP, A) JP-A-62-290535 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 1 / 00-35/00 B29C 55/00-55/30 G11B 5/704

Claims (5)

(57) [Claims] 1. A biaxially oriented laminated film having a laminated structure of at least three or more layers, wherein the outermost layer on at least one side thereof contains particles, and the particles have an average particle diameter d (nm).
And the thickness t (nm) of the outermost layer is 0.2d ≦ t ≦ 10d, and the projection height of the film surface on the outermost layer side is 20n.
3 × 10 ³ to 2 × 10 ⁵ protrusions / mm ²
And a biaxially oriented laminated film characterized in that the intermediate layer contains organic particles. 2. The method according to claim 1, wherein the number of particles satisfying the above equation is three.
× Ru ¹⁰ 3 to 1.5 × 10 ⁵ cells / mm ² der claim 1
Biaxially oriented laminated film of. 3. The biaxially oriented laminated film according to claim 1, wherein the organic particles of the intermediate layer are crosslinked organic particles. 4. The biaxially oriented laminated film according to claim 3, wherein the organic particles of the intermediate layer are divinylbenzene copolymer particles. 5. The particle surface of the organic particles of the intermediate layer is coated with a polymer having a functional group represented by the general formula “—COOX” (X is H, an alkali group, an alkali metal or an alkaline earth metal). 4. The biaxially oriented laminated film according to claim 3.