JP2803774B2 - 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 (weak projection strength). 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
No. 7431, which further improves the technology proposed in JP-A No. 7431, further improving the running property and the breaking strength of the protrusions by further optimizing the fine protrusions on the film surface, and has a better adhesiveness with the magnetic layer when used as a magnetic medium. It is another object of the present invention to provide a biaxially oriented laminated film that has little deterioration in image quality.

[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 thickness t (nm) of the outermost layer is as follows:
0.2d ≦ t ≦ 10d, and the number of protrusions having a height of 20 nm or more on the outermost film surface is 3 × 10 ³
２2 × 10 ⁵ / mm ² , and at least one outermost layer is made of a material having lower crystallinity than the intermediate layer.

[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 provide running properties, protrusion breaking strength, good adhesion to a magnetic layer, and good image quality when used as a magnetic tape.

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.

[0012] Mainly due to the outermost layer-containing particles, the number 3 × 10 ³ to 2
× 10 ⁵ protrusions / mm ² are formed.

If the number of protrusions on the outermost film surface is less than the above range, the coefficient of friction increases, 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.

In order to form such projections, the number of particles having a particle size satisfying the relationship of the above equation is 3 × 10 ^{3 to} 1.5 × 1.
Contained such that 0 ⁵ / mm ^2. in this way,
By setting the number of particles having a particle diameter satisfying a 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 protrusions are efficiently formed on the film surface by the contained particles themselves. Is done. The reason why the range of the number of particles is smaller than the range of the number of protrusions is that the protrusions may be formed by the transfer effect from the intermediate layer or the like.

[0015] In the biaxially oriented laminated film of the present invention, the outermost layer on at least one side has a lower crystallinity than the intermediate layer. By making the surface layer of low crystallinity, the strength of the projections formed on the surface is improved, the number of falling particles is reduced, and the dropout of a magnetic tape is reduced. In addition, by making the surface of the magnetic layer coated with low crystallinity, the adhesion to the magnetic layer is improved (the easy adhesion is improved).

In order to express the degree of the crystallinity, the present invention uses a crystallinity parameter by Raman spectroscopy defined as described below. The difference between the crystallinity parameters of the surface layer and the intermediate layer is 0.5 cm ^-1 or more, preferably 0.7 cm ^-1 or more, and more preferably 0.8 cm ^-1 or more. And the adhesiveness with a magnetic layer is obtained.

In the present invention, polyester is desirable as the polymer constituting the outermost layer. Furthermore, in order to achieve the object of the present invention, it is necessary that the polymer constituting the outermost layer has lower crystallinity than the polymer constituting the intermediate layer. Therefore, it is desirable that such a polymer be composed of a copolymerized polyester derived from ethylene terephthalate units and other ester components. Acid components used in other ester components include, for example, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, and diol components such as diethylene glycol, propylene glycol, and 1,4-cyclohexanedicarboxylic acid. Methanol or the like is used.

In other words, it is desirable that the polymer constituting the outermost layer be a thermoplastic polymer containing an aromatic copolyester. In this case, it is preferable that the number of protrusions having a height of 500 nm or more on the film surface on the outermost layer side is less than 50 / mm ² . By suppressing the number of the high protrusions as described above, the strength of the protrusions can be further improved, and the dropout of a magnetic tape can be further reduced.

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 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, 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 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 a 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 A two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Inc.] and a cross-section measuring device [PMS-1, 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) Crystallinity Parameter by Raman Spectroscopy The crystallinity of the laminated portion and the intermediate layer portion was evaluated using a laser Raman microprobe. Apparatus: Rmanor U-1000 (manufactured by Jobin-Yvon) Microprobe: Olympus BH-2 type Objective lens: × 100 Light source: Argon ion laser (5145A) Detector: PM: RCA31034 / Photon Counting System Measurement conditions: SLIT 1000 μm LASER 100 mW GATE TIME 1.0 sec SCAN SPEED 12 cm ^-1 / min SAMPLING INTERVAL 0.2 cm ^-1 REPEAT TIME 6 Sample setting and evaluation method: After embedding the sample in epoxy resin, polishing was performed to expose the cross section. The Raman spectrum was measured for the laminated portion and the intermediate layer portion of the sample (n = 5). The crystallinity parameter of each layer was defined as a half-width of 1730 cm ⁻¹ , which is the stretching vibration of the carbonyl group. The smaller the value of this parameter, the higher the crystallinity of the film.

(5) Image Quality (Chroma S / N) A magnetic paint having the following composition is applied to the 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.
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.

(6) Runnability (Friction coefficient μk) Using a tape runnability tester SFT-700 (Yokohama System Laboratory Co., Ltd.), a film obtained by slitting a film into a tape having a width of 1/2 inch is used. , 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.

(7) Protrusion Breaking Strength A film obtained by slitting a film into a tape having a width of 1/2 inch is repeatedly run on guide pins using a tape running tester. (Guide material: SUS, surface roughness:
0.3S) A 200 g load was applied to one end of the film, and the film was run for 20 passes at a winding angle of 90 degrees and a running speed of 3.3 cm / sec. Then, the amount of white powder adhering to the guide pins was evaluated. Was observed with a differential interference microscope, and the state of destruction of projections and the state of falling particles was evaluated. Magnification 1
Observation was performed for 10 visual fields at a magnification of 000, and the ratio of the particle dropping portion to the total number of protrusions was excellent (no particle dropping was observed), good (particles were dropped slightly, but the amount of adhered white powder was very small), and poor. (A large number of particles were observed and the amount of adhered white powder was large).

(8) Adhesive Strength of Magnetic Layer After applying the magnetic layer to the film of the present invention, a commercially available polyester tape was stuck on the magnetic surface, and the film was treated at 25 ° C. and 65% RH.
Crimping was performed for 10 minutes under the condition of 00 g / cm ² . Thereafter, the polyester tape was peeled off at a stretch, and the amount of the magnetic layer adhered to the tape was evaluated as excellent, good, and poor on a three-point scale. Excellent: No adhesion of magnetic layer at all Good: Very small amount of adhesion of magnetic layer Poor: Adhesion of magnetic layer considerably observed

[0031]

Next, embodiments of the present invention will be described based on examples. Examples 1 to 6 , Comparative Examples 1 to 3 Several kinds of particles having different particle diameters were dispersed in ethylene glycol in the form of a slurry, and after transesterification with dimethyl terephthalate, polycondensation was carried out. Polyethylene terephthalate (hereinafter abbreviated as PET) was prepared. In addition, PET containing substantially no inert particles was produced by a conventional method. Further, a polyethylene terephthalate / isophthalate copolymer (hereinafter abbreviated as PET / I) substantially containing no particles was prepared.
An appropriate amount of these polymers is mixed and the particle concentration and PE
The concentration of T / I was adjusted and dried under reduced pressure at 180 ° C. for 3 hours (3
Torr). These are combined as shown in Table 1,
It is fed to two extruders, melted at 290 ° C, merged and laminated by a rectangular merging block (feed block) for three layers, and wound around a casting drum having a surface temperature of 30 ° C using an electrostatic application casting method. After cooling and solidification, an unstretched film having a three-layer structure was produced. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the lamination thickness. This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed at a peripheral speed difference between two sets of rolls. This uniaxially stretched film is stretched 4.0 times in the width direction at 100 ° C. using a stenter at a stretching speed of 2000% / min.
C. for 5 seconds to obtain a biaxially oriented laminated polyester film having a total thickness of 14 .mu.m. In each of the examples and comparative examples, the laminated configuration was a three-layer configuration of A layer / B layer / A layer.

The crystallinity parameters of the laminated portion, the molar concentration of isophthalate (IPA), and the crystallinity parameters of the intermediate layer portion are as shown in Table 1, and the running properties, protrusion breaking strength, and magnetic properties of the obtained film are shown in Table 1. Evaluation of the adhesive strength with the magnetic layer in the case of a tape and the image quality in the case of a magnetic tape showed that the film satisfying the requirements of the present invention obtained good results for all of these characteristics. If any of the requirements were not met, no film could satisfy all of these characteristics.

[0033]

[Table 1]

[0034]

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 that satisfies the above relationship is set to a specific range, and the crystallinity relationship between the outermost layer and the intermediate layer is specified. It is possible to efficiently form difficult and desired projections to obtain a desired surface form,
Excellent runnability and projection breaking strength can be exhibited, and excellent image quality and adhesiveness to a magnetic layer for a magnetic medium can be obtained.

Continuation of the front page (56) References JP-A-62-290535 (JP, A) JP-B-2-50865 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 1 / 00-35/00 B29C 55/00-55/30

Claims (4)

(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 2 of the film surface on the outermost layer side
The number of protrusions having a height of 0 nm or more is 3 × 10 ³ to 2 × 10 ^3
A biaxially oriented laminated film, characterized in that the number is ⁵ / mm ² , and the outermost layer on at least one side is lower in crystallinity than the intermediate layer. 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. A difference in crystallinity parameter of at least one outermost layer and an intermediate layer determined by Raman spectroscopy is 0.5 cm ^−1.
A biaxially oriented laminated film as described above. 4. The outermost layer is made of a thermoplastic polymer containing an aromatic copolyester, and the number of protrusions having a height of 500 nm or more present on the film surface on the outermost layer side is 50 / mm ^2. Claims 1 to 3
The biaxially oriented laminated film according to any one of the above.