JPH089672B2 - Biaxially oriented polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film.

[Prior Art] As a biaxially oriented polyester film, a film containing particles in polyester is known (for example, JP-A-59-68325).

[Problems to be Solved by the Invention] However, in the above-mentioned conventional film, the contact speed is increased due to an increase in the process speed of the film processing step, for example, the printing step in packaging applications, the magnetic layer coating / calendering step in magnetic media applications, etc. When the surface of the film is scraped with a roll, etc., it causes a trouble in product performance in the processing process, and if the projection height of the surface is lowered to satisfy the scraping resistance, the slipperiness is satisfied. There was a problem that was not done. It is an object of the present invention to solve the above problems and provide a biaxially oriented polyester film having excellent abrasion resistance and running properties.

[Means for Solving Problems] The present invention is a biaxially oriented polyester film having fine protrusions on the surface, wherein the protrusions having a height of less than 0.08 μm have an average spacing of 10 μm or less and a height of The average distance between the projections with a diameter of 0.08 to 0.5 μm is 15 to 150 μm, and the difference in the average height between the projections with a diameter of less than 1 μm and the projections with a diameter of 1 to 8 μm is
The biaxially oriented polyester film has a thickness of 0.02 to 0.42 μm.

The polyester in the present invention means ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, ethylene-
The main constituent is at least one structural unit selected from 2,6-naphthalate units. However, other components may be copolymerized within a range that does not impair the present invention, preferably within 15 mol%. Further, in the case of a polyester containing ethylene terephthalate as a main component, it is particularly desirable because the abrasion resistance is further improved.

The surface protrusions of the film in the present invention are caused by the fine particles contained in the polyester. As the fine particles, if inert to polyester, the type is not particularly limited, substantially spherical silica due to colloidal silica, synthetic calcium carbonate, α-alumina,
Rutile type titanium dioxide and thermal type carbon black are preferable. Moreover, the surface may be surface-modified. Furthermore, not only a method of adding fine particles, but also a method of forming surface protrusions by internally depositing particles that precipitate fine particles containing calcium, lithium, or phosphorus in the polymerization system during the synthesis of polyester in combination with the addition of fine particles Can be used.

The average particle size of the fine particles is not particularly limited, but it is desirable to combine the small particle size and the large particle size in order to further improve the abrasion resistance and the running property. As the small particles, silica having an average particle diameter of 0.15 to 0.45 μm, carbon black, 0.2 to
In the case of 0.65 μm calcium carbonate and titanium oxide, abrasion resistance and running property are further improved, which is desirable. Also,
As large particles, silica having an average particle size of 0.5 to 0.8 μm, 0.
In the case of 7 to 1.2 μm calcium carbonate and titanium oxide, the abrasion resistance and the running property are further improved, which is desirable. When the content of the fine particles of the present invention is 0.3 to 1.5% by weight, particularly 0.4 to 1.0% by weight, it is effective to obtain the average protrusion interval of the present invention. Further, when combining particles having different average particle diameters, the content of the small diameter particles is 0.3 to 0.8% by weight, the content of the large diameter particles is 0.01 to 0.07% by weight, and particularly 0.02 to 0.05% by weight. It is effective in obtaining the average protrusion interval.

The film of the present invention contains the above composition as a main component,
Other types of polymers may be blended within a range that does not impair the object of the present invention, and an antioxidant, a heat stabilizer, a lubricant,
Inorganic or organic additives such as UV absorbers and nucleating agents may be added to the extent that they are usually added. The present invention is a film in which the composition is biaxially oriented, the refractive index ratio in the thickness direction indicating the degree of orientation is not particularly limited, when the range of 0.935 to 0.970, abrasion resistance,
It is particularly desirable because the running property is further improved.

The biaxially oriented polyester film of the present invention has fine protrusions on its surface. The surface protrusion has a height of 0.08
It is necessary that the average spacing of the protrusions having a size of less than 10 μm is 10 μm or less, more preferably 8 μm or less. Height is 0.08 μm
If the average distance between the protrusions is less than 10 μm, the running property cannot be satisfied. The lower limit of the average spacing of the protrusions is not particularly limited, but about 1 to 2 μm is a manufacturing limit. Further, it is necessary that the average interval between the protrusions having a height of 0.08 to 0.5 μm is 15 to 150 μm, and more preferably the average interval is 20 to 100 μm. The average distance between protrusions with a height of 0.08 to 0.5 μm is 15
If it is less than μm, the abrasion resistance cannot be satisfied. Also the height
If the average distance between the protrusions of 0.08 to 0.5 μm exceeds 150 μm, the running performance cannot be satisfied.

Furthermore, a protrusion having a protrusion diameter of less than 1 μm and a protrusion diameter of 1 to 8 μm
It is necessary that the difference in average height of the protrusions is 0.02 to 0.42 μm, and more preferably the difference in average height is 0.05 to 0.30 μm. If the difference in height average value is less than the above range, the running performance cannot be satisfied. If the difference in average height exceeds the above range, the abrasion resistance cannot be satisfied.

The biaxially oriented polyester film of the present invention has a surface space volume (φ) of 2 × 10 ³ to 1 × 10 ⁵ , preferably 1 × 10 ⁴ to 1 × 10 ⁵ , and a refractive index n in the film width direction. _TD
Is in the range of 1.655 to 1.700, preferably 1.675 to 1.700, because the abrasion resistance and the running property are better. Furthermore, the total reflection Raman crystallization index of the film surface is 13 cm ^-1
Above, preferably at least 17 cm ⁻¹ , the abrasion resistance and running property are further improved, which is particularly desirable.

Next, a method for producing the biaxially oriented polyester film of the present invention will be described. The polyester constituting the biaxially oriented polyester film of the present invention can be obtained by directly performing polycondensation via esterification or performing polycondensation via a transesterification reaction. As a method of adding fine particles to the polymer, a method of adding at the time of polymerization or a method of mixing with polymer pellets before extrusion can be adopted, but as a method of adjusting the content of particles, high-concentration master pellets, preferably 1 to A master pellet method in which a master pellet having a particle concentration of 5% by weight is diluted with a substantially particle-free polyester during film formation is preferred. Furthermore, a high concentration, preferably 1 to 5% by weight of the intrinsic viscosity of the master pellet,
Adjusting the copolymerization component, the difference between Tcc (cold crystallization temperature) and Tg (glass transition temperature) of the master pellet containing small particles △ Tcg is 50 to 90 ℃, △ of the master pellet containing large particles When Tcg is in the range of 60 to 100 ° C. and the former is smaller than the latter, it is extremely effective for satisfying the projection interval in the range of the present invention. Furthermore, when the crystallization acceleration coefficient of the master pellet containing the small-sized particles is larger than the crystallization acceleration coefficient of the master pellet containing the large-sized particles, the difference between the average value of the protrusion interval and the height in the range of the present invention is satisfied. Is extremely effective for

After sufficiently drying the pellets of the particle-containing polyester obtained by the above method, the pellets are supplied to a melt extruder, and the pellets are melted or higher, at a temperature at which the polymer is decomposed or lower, and melt-extruded into a sheet from a slit die, An unstretched film is prepared by cooling and solidifying.

Next, the unstretched film is biaxially stretched and oriented.
As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used, and the sequential biaxial stretching method is particularly preferable. As the stretching conditions in this case, stretching in the longitudinal direction and then in the width direction is performed first, and the stretching in the longitudinal direction is divided into three or more steps so that the total stretching ratio in the longitudinal direction is 3 to 5.
The method of doubling is effective for obtaining the protrusion spacing within the scope of the present invention. The stretching ratio in the width direction is generally 3 to 4 times.
The stretching speed is preferably set within a relatively slow range of 10 ³ to 10 ⁴ % / min in order to satisfy the above conditions. Further, the stretching temperature is effectively within the range of the present invention in the range of Tg to Tg + 20 ° C. Next, the stretched film is heat-treated, and the heat treatment condition at that time is generally a temperature of 180 to 230 ° C., preferably 190 to 220 ° C. for 0.5 to 60 seconds. The biaxially oriented polyester film of the present invention can be obtained as described above, but is not particularly limited to this method.

[Method for Measuring Characteristics 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 of particles Fine particles are dispersed in ethylene glycol or as a water slurry, and a centrifugal sedimentation type particle size distribution measuring device (Horiba Seisakusho) is used.
The volume average diameter (μm) was measured using CAPA500).

(2) Content of particles After adding o-chlorophenol 1.0 to 100 g of polyester and heating at 120 ° C. for 3 hours, centrifugal separation was performed at 30,000 rpm for 40 minutes using an ultracentrifuge 55P-72 manufactured by Hitachi Koki Co., Ltd. The obtained particles are vacuum dried at 100 ° C. When a fine particle corresponding to a polymer is observed when the fine particles are measured with a scanning differential calorimeter, o-chlorophenol is added to the fine particles, and after heating and cooling, centrifugation is performed again. When the dissolution peak is no longer observed, the fine particles are designated as precipitated particles. Normally, two centrifugation operations are sufficient. The content is defined as the ratio (% by weight) to the total weight of the particles thus separated.

(3) Intrinsic viscosity Measured in o-chlorophenol according to ASTM D1601, expressed in dl / g.

(4) Glass transition point Tg, cold crystallization temperature Tcc It was measured using a Perkin Elmer DSC (differential scanning calorimeter) type II. The DSC measurement conditions are as follows. That is, 10 mg of a sample is set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The temperature of this quenched sample is raised at 10 ° C./min, and the glass transition point Tg is detected. The temperature was further raised, and the crystallization exothermic peak temperature from the glass state was set as the cold crystallization temperature Tcc. Where Tcc
The difference between Tg (Tcc-Tg) is defined as ΔTcg.

(5) Crystallization acceleration coefficient (unit: ° C) ΔTcg (I) of polyester containing 1% by weight of inactive particles by the above method, and ΔTcg (II) of polyester of the same viscosity obtained by removing inactive particles therefrom. Is measured and △ Tcg
Difference between (II) and △ Tcg (I) [△ Tcg (II)-△ Tcg
(I)] was used as the crystallization acceleration coefficient.

(6) Surface projection height 2 The height of the smooth surface of the film was measured with a scanning electron microscope (ESM-3200 manufactured by Elionix Co., Ltd.) and a cross-section measurement device (PMS-1 manufactured by Erionix Co., Ltd.). The height measurement value when scanning with 0 as the gray value of 256 gradations is used as an image processing device (IBAS20 manufactured by Carl Zeiss Co., Ltd.).
00) and reconstruct the film surface projection image on the image processing device based on this gray value. Next, the maximum gray value of the projection portion binarized in this surface projection image was obtained by converting it to the projection height (μm). This measurement 1m of the film
Performed for m ² .

(7) Protrusion spacing Similar to the item (6), regarding the protrusion height of the gray value of the protrusion portion binarized in the surface protrusion image, find the number of protrusions within the protrusion height range, and then calculate the number of protrusions. The protrusion interval was calculated from This measurement was performed on 1 mm ² of the film.

(8) Projection diameter In the same manner as in item (6), the projection diameter was determined for the binarized projection portion in the surface projection image.

(9) Surface space volume (Φ) Using a high precision thin film step measuring instrument ET-10 of Kosaka Laboratory, stylus tip radius 0.5 μm, cutoff 0.08 mm, measurement length 1.0 mm, longitudinal magnification 200,000 times, lateral magnification 2000 The surface roughness curve of the film is measured in fold. A peak count level is set every 0.005 μm in parallel above the average line (center line) of this roughness curve.
When there is a point that intersects the above peak count level one or more times between two points where the curve intersects the average line,
This is defined as one peak, and the number of peaks is obtained during the measurement length. For each peak count level, the number of peaks is determined and the number of peaks determined for the nth peak count level from the average line is defined as PC (n). When the peak count level at which the number of peaks starts to become 0 between measurement lengths is mth from the average line, the effective space volume Φ is The average value of 50 measurements taken at different locations is used.

(10) Refractive Index and Refractive Index Ratio The measurement was performed at 20 ° C. and 60% relative humidity using an Abbe refractometer with sodium D line (wavelength 589 nm) as a light source. As the mount solution, sulfur-methylene iodide or methylene iodide solution was used. Also, the refractive index in the thickness direction of the biaxially oriented film (denoted as A) and the refractive index in the thickness direction of the non-oriented (amorphous) film prepared by quenching into water at 10 ° C. after melt pressing (denoted as B) Was measured, and A / B was defined as the refractive index ratio in the thickness direction.

(11) Total reflection Raman crystallization index of the surface Ramanor U-1000 Raman system manufactured by Jobin-Yvon Co., was used to measure the total reflection Raman spectrum, and the total half-width of the surface was 1730 cm ^-1 which is the stretching vibration of the carbonyl group. The reflection Raman crystallization index was used. The measurement conditions are as follows. The measurement depth is 500 to 1000Å from the surface.

Light source Argon ion laser (5145cm ^-1 ) Sample setting Press the film surface to the total reflection prism so that the laser polarization direction (S polarization) and the film longitudinal direction are parallel, and the incident angle of the laser to the prism (film thickness The angle with the vertical direction) was set to 60 °.

Detector PM: RCA31034 / Photon Counting System (Hamamatsu C1230) (supply 1600V) Measuring condition SLIT 1000μm LASER 100mW GATE TIME 1.0sec SCAN SPEED 12cm ^-1 / min SAMPLING INTERVAL 0.2cm ^-1 REPEAT TIME 6 (12) Scraping resistant film 20 cm by pushing the one-sided blade at a 90-degree angle into a slit of 1/2 inch width tape and pushing in 0.5 mm
Run (speed: 6.7 cm / s, tension: 500 g). The adhesion height of the powder scraped off by the single blade is read with a microscope and the scraped amount (μ
m). If the abrasion amount is 15 μm or less, the abrasion resistance is good, and if it exceeds it, the abrasion resistance is poor. This corresponds to the abrasion resistance in the film processing process.

(13) Running property As a standard condition, a 1/2 inch wide tape-shaped film is contacted with a fixed shaft (surface roughness 0.2S) with an outer diameter of 6mmφ at an angle θ = πrad in an atmosphere of 20 ° C and 60% relative humidity. And drive at a speed of 3.3 cm / s. When the inlet tension T _{1 is set} to 25 g, the outlet tension T ₂ is measured, and the dynamic friction coefficient (μ _k ) is calculated from the following equation.
To calculate.

_{μ k = (1 / θ)} In (T 2 / T 1) = (1 / π) In (T 2/25) This mu _k value is good when the running of 0.25 or less, when the traveling resistance beyond that It is bad. This corresponds to the runnability when using a magnetic medium.

[Examples] The present invention will be described based on Examples and Comparative Examples.

Example 1 An ethylene glycol slurry containing fine particles was prepared by using colloidal silica having an average particle size of 0.3 μm as the small particles and colloidal silica having an average particle size of 0.6 μm as the large particles. Only a slurry containing large particles is boiled at 180 ° C for 2 hours, then transesterified by a conventional method, polymerized, and polyethylene terephthalate particle master pellets containing 1% by weight of large particles having an intrinsic viscosity of 0.70 are polymerized. And 1% by weight of small particles with an intrinsic viscosity of 0.60
A containing particle master pellet was obtained. These particle master pellets and polyethylene terephthalate pellets that do not substantially contain particles are
Pellets mixed so that 0.5% by weight and 0.05% by weight of large particles were vacuum dried at 180 ° C for 8 hours, then fed to an extruder, melt-extruded at 280 ° C, and passed through a gear pump and a filter. Discharge in sheet form from the die and wrap this molten sheet around a cooling drum with a surface temperature of 40 ° C.
An unstretched sheet was prepared by cooling and solidifying.

The unstretched sheet was introduced into a stretching stenter and stretched 4.0 times in the longitudinal direction and 3.7 times in the width direction. Stretching speed is 2 × 10 ³
% / Min, the heating temperature during stretching is relatively slow.
85 ° C. Next, this film was introduced into the heat treatment zone as it was without cooling, and was heat-fixed at 210 ° C. for 3 seconds to obtain a biaxially oriented polyester film having a thickness of 14 μm.

Examples 2 to 4 and Comparative Examples 1 to 5 Among various conditions of Example 1, types of fine particles to be added, average particle size, addition amount, stretching temperature, stretching ratio, heat setting temperature, and heat setting Samples with different properties were made by varying the degree of relaxation. The evaluation results of these films are summarized in Table 1. From Table 1, when the surface protrusion of the film and the interval are within the range of the present invention, a film having both abrasion resistance and running property is obtained, but otherwise, a film having both abrasion resistance and running property is obtained. I know there isn't.

[Effect of the Invention] The biaxially oriented polyester film thus obtained is
By providing a magnetic layer on one side or both sides, it is used by being processed into various magnetic recording media such as video tapes, audio tapes, and floppy disks. The magnetic layer may be formed by coating magnetic powder with a binder, or may be formed by thinning a ferromagnetic material by a method such as vacuum deposition, sputtering, ion plating, or plating. The biaxially oriented polyester film of the present invention is used not only for magnetic recording media, but also for applications such as graphics, stamping foils, electrical insulating materials, dielectrics for capacitors, and packaging where smoothness and slipperiness are problems. , Can be effectively used.

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Claims (1)

[Claims] 1. A biaxially oriented polyester film having fine projections on its surface, wherein the average spacing of projections having a height of less than 0.08 μm is 10 μm or less, and the average spacing of projections having a height of 0.08 to 0.5 μm. Is 15 to 150 μm, and the difference in height average value between the projections with a projection diameter of less than 1 μm and the projections with a projection diameter of 1 to 8 μm is
A biaxially oriented polyester film having a thickness of 0.02 to 0.42 μm.