JP2569686B2 - Biaxially oriented polyester film - Google Patents

Description

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

[Prior Art] As a biaxially oriented polyester film, a film in which a polyester contains substantially spherical silica particles caused by colloidal silica is known (for example, JP-A-59-171623).

[Problems to be Solved by the Invention] However, the above-mentioned conventional biaxially oriented polyester film is required to increase the processing speed of a film processing step, for example, a printing step in a packaging application, a magnetic layer coating / calendering step in a magnetic medium application. The disadvantage is that the film position regulating guide pin and the film end surface (side surface) come into contact at high speed, and the powder generated by the film shaving the film end surface becomes a trouble in the processing process and product performance. Recently, it has become a problem. Further, with the increase in the processing speed of the film processing step, there is a problem that the film is damaged when the film passes through the step.

An object of the present invention is to improve such a problem and to provide a film which is excellent in the difficulty of powder falling off from an end face (hereinafter referred to as an end face strength) and the damage resistance of a film (hereinafter referred to as a scratch resistance). I do.

[Means for Solving the Problems] In the present invention, at least one surface of a layer (A layer) composed of a polyester (A) substantially containing no inorganic particles contains spherical polyester derived from colloidal silica in the polyester. A film obtained by laminating a layer (B layer) composed of the composition (B), wherein the thickness ratio of the A layer and the B layer (B /
A) is 0.04 to 1.4, the difference (AB) between the crystallization parameter ΔTcg of the polyester (A) and the composition (B) is 1 to 45 ° C., and the average projection height on the surface of the composition (B) is 20 to 150nm, and
The present invention relates to a biaxially oriented polyester film characterized in that the average protrusion interval on the surface is 20 μm or less.

The polyester in the polyester (A) and the polyester in the composition (B) constituting the present invention are ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, ethylene 2,6- At least one structural unit selected from naphthalate units is used as a main component. 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 end face strength and the scratch resistance are further improved.

It is necessary that the polyester (A) constituting the present invention does not substantially contain inorganic particles. Here, “substantially” means not more than 0.05% by weight. If more inorganic particles are contained, the end face strength becomes poor, which is not preferable.

The spherical silica originating from the colloidal silica in the composition (B) of the present invention is not particularly limited, but is usually produced by an ion exchange method or an alkoxide method, and in particular, is substantially spherical produced by an alkoxide method. Silica is particularly desirable because scratch resistance is further improved.

The polyester (A) and the composition (B) of the present invention contain the above-mentioned composition as a main component, but may be blended with other kinds of polymers as long as the object of the present invention is not impaired. Organic additives such as heat stabilizers, lubricants and ultraviolet absorbers may be added to the extent that they are usually added.

The film of the present invention is a film in which the composition (B) layer is laminated on at least one surface of the polyester (A) layer, wherein the polyester (A) layer is biaxially oriented, and the composition (B)
The layers need to be biaxial or uniaxially oriented. While the extent of this orientation is not particularly limited, the Young's modulus is a measure of the degree of molecular orientation of the polymer, as layered film, a longitudinal direction 350~1300kg / mm ^2, the width direction 400-1500
It is particularly preferable that the weight ratio is in the range of kg / mm ^{2 because} the end face strength and the scratch resistance are further improved.

The film of the present invention has a thickness ratio (B / A) of the polyester (A) layer to the composition (B) layer of 0.04 to 1.4, preferably 0.1 to 0.4.
It is necessary to be in the range of 06 to 0.6, more preferably 0.1 to 0.5. If the thickness ratio is smaller than the above range, the scratch resistance becomes poor, while if it is large, the end face strength becomes poor, which is not preferable. When there are two or more layers of the composition (B), the total thickness must be within the above range.

In the film of the present invention, the difference (AB) in the crystallization parameter ΔTcg between the polyester (A) layer and the composition (B) layer is 1
~ 45 ° C, preferably 2-40 ° C, more preferably 2-30 ° C
It must be in the range of ° C. Crystallization parameter Δ
If the difference in Tcg is smaller than the above range, the end face strength becomes unfavorable. If the crystallization parameter ΔTcg is larger than the above range, the scratch resistance becomes poor, which is not preferable.

In the film of the present invention, the average projection height on the surface of the composition (B) needs to be in the range of 20 to 150 nm, preferably 30 to 130 nm, and more preferably 35 to 120 nm. If the average protrusion height on the surface of the composition (B) is smaller than the above range or larger than the above range, the scratch resistance becomes poor, which is not preferable.

In the film of the present invention, the average interval between projections on the surface of the composition (B) needs to be 20 μm or less, preferably 18 μm or less. If the average protrusion interval is larger than the above range, the scratch resistance becomes poor, which is not preferable. The lower limit of the average protrusion interval is not particularly limited, but usually about 5 μm is the manufacturing limit.

When the average particle diameter of the spherical silica caused by the colloidal silica contained in the composition (B) of the film of the present invention is c,
When the thickness of the composition (B) layer is in the range of 2c to 20c, especially 4c to 10c, scratch resistance and end face strength are further improved, which is particularly desirable.

The thickness (total thickness) of the composition (B) layer of the film of the present invention is not particularly limited, but when it is in the range of 1 to 5 μm, particularly 1.5 to 4 μm, the scratch resistance and the end face strength are further improved. Especially desirable.

The film of the present invention is resistant when the effective space volume formed by the surface projections of the composition (B) layer is in the range of 1 × 10 ^{3 to} 5 × 10 ⁵ , particularly 5 × 10 ^{3 to} 3 × 10 ^5. This is particularly desirable because the scratching property and the end face strength are further improved.

The film of the present invention is more excellent in scratch resistance and end face strength when the degree of peak of surface protrusions (ratio of protrusion height / projection diameter) of the composition (B) layer is in the range of 0.05 to 0.12. Is particularly desirable.

The film of the present invention is particularly preferable when the melting point of the polyester of the composition (B) is lower by 3 to 10 ° C. than the melting point of the polyester (A), because the scratch resistance and the end face strength are further improved.

The film of the present invention comprises a composition (B) layer having a surface average roughness Ra (nm) in the width direction and a composition (B) layer thickness d (μ).
It is particularly preferable that the ratio m) and Ra / d are in the range of 1 to 20 because the scratch resistance and the end face strength are further improved.

The film of the present invention is particularly desirable when the surface average roughness Ra in the width direction of the surface of the composition (B) layer is in the range of 8 to 18 nm, because the scratch resistance and the end face strength are further improved.

The film of the present invention has a refractive index in the width direction of at least one surface.
When it is in the range of 1.675 to 1.700, scratch resistance and end face strength are further improved, which is particularly desirable.

 Next, a method for producing the film of the present invention will be described.

First, as a method of incorporating silica particles derived from colloidal silica into the polyester of the composition (B),
Dispersing in the form of a sol of ethylene glycol, which is a diol component of the polyester, and polymerizing the ethylene glycol with a predetermined dicarboxylic acid component is suitable for obtaining the projection height and spacing of the present invention. At this time, it is preferable that the content of sodium in the sol is 0.5% by weight or less, preferably 0.2% by weight or less based on the particles, and the pH of the sol is in the range of 7 to 10. This is useful for obtaining optimization parameters. Further, as a method of adjusting the content of particles, a method of diluting a high-concentration master pellet with a polyester containing substantially no particles at the time of film formation is effective for obtaining the projection height and projection interval of the present invention. is there. The average particle size of the spherical silica caused by colloidal silica is 0.25 to 0.45 μm, and the content (based on the composition (B)) is
An amount of 0.4 to 1.5% by weight is effective for obtaining the difference in the crystallization parameter ΔTcg, the average projection height, and the average projection interval in the range of the present invention. Also, a slurry of ethylene glycol
A method of heat-treating at a temperature of 140 to 200 ° C., particularly 180 to 200 ° C. for 30 minutes to 5 hours, especially 1 to 3 hours, or
The method of adding 0.5 to 20% by weight of an ammonium phosphate salt obtains a difference in crystallization parameter ΔTcg, a projection height, a projection interval, and a projection sharpness of the polyester (A) of the present invention and the composition (B). It is effective for Further, as a method for making a difference between the melting points of the composition (B) and the polister (A), it is effective to use the composition (B) as a copolymerized polyester. In this case, the copolymerized component is an isophthalic acid component, 1,4 cyclohexylene dimethanol component, as the copolymerization amount,
1-8 mol% is preferred.

Further, the intrinsic viscosity of the polyester (A) is 0.60 to 0.75,
It is possible to set the intrinsic viscosity of the polyester of the composition (B) to 0.55 to 0.65 and to set the intrinsic viscosity of the polyester (A)> the polyester of the composition (B) so that the crystals of the polyester (A) and the composition (B) are formed. It is effective to set the optimization parameter ΔTcg within the scope of the present invention. It is also effective to use the copolymerized polyester as the composition (B) to obtain the difference in the crystallization parameter ΔTcg within the range of the present invention. In this case, the copolymer component is preferably an isophthalic acid component, a 1,4-cyclohexylene dimethanol component, and the copolymerization amount is preferably 1 to 8 mol%.

Next, as a method of laminating the composition (B) on at least one surface of the polyester (A), the following method is effective.

<Lamination method 1> The polyester (A) and the composition (B) are supplied to a known extruder for melt lamination, extruded into a sheet from a slit die, and cooled and solidified on a casting roll to produce an unstretched film. . That is, the polyester (A) and the composition (B) are laminated using two or three extruders, two or three layers of a manifold, and a die. in this case,
The ratio of die slit gap / unstretched film thickness is 5 to 30,
It is effective to set the average projection height within the range of the present invention preferably in the range of 8 to 20. Further, the composition (B)
It is effective to raise the melting temperature of the extruder 20 to 40 ° C. higher than that of the polyester (A) side to obtain the difference in the crystallization parameter ΔTcg and the average projection height in the range of the present invention.

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, first use the sequential biaxial stretching method of stretching in the longitudinal direction, then in the width direction,
The elongation in the longitudinal direction is from (glass transition point of polymer -10 ° C)
(Glass transition point of polymer + 10 ° C)
The method in which the stretching is performed at a relatively small stretching speed of 1000 to 10000% / min is effective for obtaining a difference in the average projection height, interval, and crystallization parameter ΔTcg in the range of the present invention. The stretching temperature and speed in the width direction are preferably in the range of 80 to 160 ° C. and 1000 to 20000% / min. The stretching ratio is preferably 3 to 5 times in both the longitudinal and width directions. Further, a method in which the stretching in the longitudinal direction is performed in three stages, preferably in four or more stages, is extremely effective in obtaining the differences in the average projection height, interval, and crystallization parameter ΔTcg within the range of the present invention. Next, this stretched film is heat-treated. The heat treatment conditions in this case are as follows:
The temperature is preferably in the range of -220C, preferably 170-200C for 0.5-60 seconds.

<Lamination method 2> Instead of performing lamination during extrusion in the above lamination method 1, after stretching an unstretched film of polyester (A) in the longitudinal direction, and before stretching in the width direction, the composition (B) ) Are laminated and then stretched in the width direction to laminate. The conditions for obtaining the film of the present invention are lamination method 1
Is the same as

[Action] The present invention provides a polyester composition containing a colloidal silica containing a polyester composition containing colloidal silica and a polyester containing substantially no inorganic particles in a specific range of thickness ratio and crystallization characteristics. It is presumed that the effects of the present invention were obtained as a result of improving the shock absorbing ability of the projections existing on the surface and the viscoelastic properties of the end faces because the heights and the intervals of the projections on the surface were within the specific ranges.

[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 of particles Polyester is removed from the film by plasma ashing or O-chlorophenol dissolving, dispersed in ethanol, and stretched and sedimented (HORIBA, CAPA50
0 used).

(2) Particle content 1.0 g of O-chlorophenol was added to 100 g of polyester, heated at 120 ° C. for 3 hours, and then centrifuged at 30,000 rpm for 40 minutes using an ultracentrifuge 55P-72 manufactured by Hitachi Koki Co., Ltd. And the resulting particles are vacuum dried at 100 ° C. When the dissolution peak corresponding to the polymer is observed when the fine particles are measured by a scanning differential calorimeter, O-chlorophenol is added to the fine particles, and the mixture is heated and cooled and then centrifuged again. When the dissolution peak is no longer observed, the fine particles are regarded as precipitated particles. Usually, two centrifugation operations are sufficient. The particle content is defined as a ratio (% by weight) to the total weight of the particles thus separated.

(3) Crystallization parameter ΔTcg Measured using a DSC (differential scanning calorimeter) type II manufactured by PerkinElmer. The measurement conditions for DSC are as follows.
That is, 10 mg of a sample is set in a DSC device, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The quenched sample is heated at a rate of 10 ° C./min, and the glass transition point Tg is detected.
The temperature was further increased, and the crystallization exothermic peak temperature from the glassy state was defined as the cold crystallization temperature Tcc. Here, the difference between Tcc and Tg (Tcc−Tg) is defined as a crystallization parameter ΔTcg.

(4) Effective space volume of protrusion Φ Using the Kosaka Laboratory high-precision thin film level measuring device ET-10, the tip radius of the stylus is 0.5 μm, the cutoff is 0.08 mm, the measurement length is 1.0 mm, the vertical magnification is 200,000, and the horizontal magnification is 2000 Measure the surface roughness curve of the film in times. A peak count level is provided every 0.005 μm in parallel above the average line (center line) of the roughness curve,
When there is a point at which the peak count level crosses one or more times between two points at which the curve crosses the average line,
This is defined as one peak, and the number of peaks is determined between the measurement lengths. For each peak count rel, the number of peaks is determined, and the number of peaks determined for the n-th peak count level from the average line is defined as PC (n). When the peak count level at which the number of peaks becomes zero for the first time during the measurement length is m-th from the average line, the effective space volume Φ is The average value measured 50 times at different locations is used.

(5) Refractive index Measured using an Abbe refractometer using sodium D line (589 nm) as a light source. The measurement was performed at 25 ° C. and 65% RH using methylene iodide as the mounting solution.

(6) Thickness ratio The cross section of the film was observed with a transmission electron microscope, and the thickness of the layer containing spherical particles (composition B) caused by colloidal silica and the layer containing substantially no inorganic particles (polyester A) The thickness was measured and the thickness ratio was calculated from those values.

(7) Average height of projections and peak degree of projections In a two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Inc.] and a cross-section measuring device [PMS-1, manufactured by Elionix Inc.] The height measurement value of the projection when scanning with the height of the flat surface of the film surface set to 0 is sent to an image processing device [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] as a gray value of 256 gradations. First, reconstruct the film surface projection image on IBAS2000. Next, a circle-equivalent diameter is obtained from the area of each projection obtained by binarizing a surface projection image having 10 or more gradations, and this is defined as the average diameter of the projection. The highest value among the binarized individual projections is defined as the height of the projection, and this is determined for each individual projection. Repeat this measurement 500 times in different places,
The average value of all the measured protrusions was used as the average protrusion diameter and the height, and the ratio of the average protrusion height / the protrusion diameter was defined as the protrusion peak degree. In addition, the height of one gradation is an arbitrary set value H
Is divided by 256, and the arbitrary set value H is a value obtained by multiplying Ra (unit: μm) of the film surface to be measured usually by 30. The magnification of the scanning electron microscope is selected from a value between 2000 and 8000 times, and is changed according to the Ra of the film surface.

(8) Center line average surface roughness Ra, average protrusion interval Sm Measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was an average value of 20 measurements.

・ Stylus of stylus tip: 0.5 μm ・ Load of stylus: 5 mg ・ Measuring length: 1 mm ・ Cutoff value: 0.08 mm The definition of Ra and the average spacing Sm of projections is, for example, the Measurement and evaluation method ”(General Technology Center, 1983).

(9) Young's modulus According to the method specified in JIS-Z-1702, using an Instron type tensile tester, 25 ° C, 65%
Measured at RH.

(10) Intrinsic viscosity [η] (unit: dl / g) A value calculated from the following formula from the solution viscosity measured at 25 ° C. in orthochlorophenol is used. That is, η _SP / C = [η] + K [η] ² · C where η _SP = (solution viscosity / solvent viscosity) −1, and C is the solvent 10
Dissolved polymer weight per 0 ml (g / 100 ml, usually 1.2), K
Is the Haggins constant (0.343). The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

(11) Scratch resistance A tape running tester (TBT3, manufactured by Yokohama System Research Institute) that is obtained by slitting a film into a 1/2 inch wide tape
(Running speed 3.3cm /)
Second, 100 passes).

At this time, the scratches in the film were observed with a microscope, and when there were almost no scratches, it was judged that the scratch resistance was good, and when there were three or more scratches per tape width, the scratch resistance was poor.

(12) Edge strength The film is slit into a 1/2 inch wide tape, and the end face of the film is the "collar" of the position control guide.
At a running speed of 1000 m / min.
After traveling 500,000 m, the amount of powder generated and attached to the "brim (flange)" was checked, and the following ranking was performed. Rank A: Little white powder is generated Rank B: White powder is slightly generated, but does not cause any trouble in the processing process or product performance Rank C: Many white powders are generated, and processing process and product performance [Example] The present invention will be described based on an example.

Example 1 An ethylene glycol sol (slurry) containing colloidal silica having an average particle diameter of 0.3 μm was prepared, and the sodium content was adjusted to 0.1% by weight based on the particles. This ethylene glycol slurry was heat-treated at 190 ° C. for 1.5 hours, transesterified with dimethyl terephthalate, and polycondensed to prepare a particle master pellet of polyethylene terephthalate containing 1% by weight of silica particles derived from colloidal silica. At this time, the polycondensation time was adjusted to increase the intrinsic viscosity to 0.62.
And In addition, a PET containing substantially no inorganic particles having an intrinsic viscosity of 0.62 is produced by a conventional method, mixed with a polyethylene terephthalate particle master pellet containing 1% by weight of the silica particles derived from the colloidal silica, and the silica particles are mixed. The content was adjusted to 0.5% by weight (composition B). Next, a PET containing substantially no inorganic particles having an intrinsic viscosity of 0.70 was produced by a conventional method (composition A), and pellets of these compositions A and B (Table 1) were prepared.
It was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours. The composition A is supplied to the extruder 1, and the composition B is supplied to the extruder 2,
It was melted at 300 ° C., merged and laminated in a manifold, wrapped around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, cooled and solidified, and a two-layer unstretched film was produced. At this time, an unstretched film was prepared by setting the melting temperature of the extruder 1 to 280 ° C., the melting temperature of the extruder 2 to 310 ° C., and setting the ratio of the die slit gap / unstretched film thickness to 10. Further, the discharge amount of each extruder was adjusted so that the composition A
And B were adjusted. Temperature of this unstretched film
The film was stretched 4.5 times in the longitudinal direction at 80 ° C. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film is stretched using a stenter at a stretching speed of 2000% / min.
The film was stretched 4.0 times in the width direction at 0 ° C. and heat-treated at 190 ° C. for 5 seconds under a constant length to obtain a biaxially oriented laminated film having a thickness of 15 μm. The parameters of the present invention of these films were within the range of the present invention as shown in Table 2, and the scratch resistance and end face strength were good as shown in Table 2.

Examples 2 to 5 and Comparative Examples 1 to 8 Ethylene glycol sols (slurries) containing colloidal silica having different average particle sizes were prepared, and the sodium content was adjusted to 0.02 to 1.5% by weight based on the particles. After heat-treating this ethylene glycol slurry under various conditions, after transesterification with dimethyl terephthalate, polycondensation,
A particle master pellet of polyethylene terephthalate containing 1% by weight of silica particles derived from colloidal silica was prepared. At this time, the polycondensation time was adjusted to reduce the intrinsic viscosity to 0.
Changed between 4 and 0.9. Further, a PET having substantially the same intrinsic viscosity as described above and substantially free of inorganic particles is produced by a conventional method, and mixed with a polyethylene terephthalate particle master pellet containing 1% by weight of the silica particles derived from the above colloidal silica. Compositions with different particle contents were made (Composition B). Next, by a conventional method, silica particles having an intrinsic viscosity of 0.50 to 0.85 and different average particle diameters of 0.001 to
A PET containing 0.5% by weight and a PET substantially containing no inorganic particles were produced (composition A), and pellets of these compositions A and B (Table 1) were dried at 180 ° C. for 3 hours under reduced pressure (Table 1). 3 Torr). The composition A is supplied to the extruder 1 and the composition B is further supplied to the extruder 2, melted at 300 ° C., merged and laminated in a manifold, and cast at a surface temperature of 30 ° C. using an electrostatic application casting method. -It was wound around a drum and cooled and solidified to form an unstretched film having a three-layer structure. At this time, the melting temperature of the extruder 1 was changed in the range of 270 to 320 ° C., the melting temperature of the extruder 2 was changed in the range of 280 to 310 ° C., and the ratio of die slit gap / unstretched film thickness was also variously changed. An unstretched film was made. In addition, the discharge rates of the respective extruders were adjusted to prepare compositions A and B having different thickness ratios. This unstretched film is stretched at 80 ° C in the longitudinal direction.
It was stretched 4.5 times. This stretching was carried out by changing the number of stretching stages in 1 to 4 stages by the peripheral speed difference between two sets of rolls. This uniaxially stretched film is stretched 4.0 times in the width direction at 100 ° C. at a stretching speed of 2,000% / min using a stenter, and is heat-treated at 190 ° C. for 5 seconds under a constant length to obtain a biaxially oriented laminated film having a thickness of 15 μm. I got The parameters of the present invention and the scratch resistance and end face strength of these films are as shown in Table 2. When the parameters of the present invention are within the range of the present invention, both the scratch resistance and end face strength are good. It can be seen that when the parameters are out of the range of the present invention, a film having both good scratch resistance and good end face strength cannot be obtained.

[Effects of the Invention] The present invention provides a polyester composition containing colloidal silica, wherein a polyester composition containing colloidal silica and a polyester containing substantially no inorganic particles are laminated in a specific range of thickness ratio and crystallization characteristics and laminated. Since the height and spacing of the protrusions on the surface of the composition are in a specific range, a film having both good scratch resistance and end face strength is obtained, and can respond to an increase in film processing speed in each application. It is. Although the use of the film of the present invention is not particularly limited, it is particularly useful as a base film for a magnetic recording medium in which scratches on the film surface and powder from the end face in the processing step are particularly problematic in the processing step and product performance. In the film of the present invention, the one having a two-layer structure has the surface of the composition B on the running surface (the surface on which the magnetic layer is not coated for a magnetic recording medium, and other processes such as printing and laminating are not applied. Surface).

Claims (1)

(57) [Claims] 1. A layer comprising a composition (B) comprising a polyester containing spherical silica derived from colloidal silica on at least one side of a layer (A layer) comprising a polyester (A) substantially containing no inorganic particles. (B layer), wherein the thickness ratio of the A layer and the B layer (B /
A) is 0.04 to 1.4, the difference (AB) between the crystallization parameter ΔTcg of the polyester (A) and the composition (B) is 1 to 45 ° C., and the average projection height on the surface of the composition (B) is 20 to 150nm, and
A biaxially oriented polyester film, wherein the average protrusion spacing on the surface is 20 μm or less.