JPH0445529B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a biaxially oriented polyester film. [Prior Art] As a biaxially oriented polyester film, a polyester film in which the height of the surface protrusions is limited is known (for example, Japanese Patent Laid-Open No. 73877/1983). [Problems to be Solved by the Invention] However, the above-mentioned conventional biaxially oriented polyester film has problems with the processing speed of the film, such as the printing process in packaging applications and the magnetic layer coating/calendering process in magnetic recording media applications. As the film's surface increases, the surface of the film is scraped by contacting rolls, which causes problems in the processing process and product performance, which has recently become a problem. The object of the present invention is to improve such problems and provide a film that maintains the "slip properties" necessary for any application and has an excellent "scratching resistance" on the surface. [Means for solving the problem] A biaxially oriented film whose main component is a composition consisting of polyester and inert inorganic particles,
The average particle diameter D (μm) of the inert inorganic particles, the average surface roughness Ra (μm) in the width direction of the film, and the average height H (μm) of surface protrusions satisfy the following formula. Axially oriented polyester film. 0.05≦D≦0.6 ... Ra≧0.04D ... 2Ra≦H≦8Ra ... The polyester in the present invention is ethylene terephthalate, ethylene α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylate , at least one structural unit selected from ethylene 2,6-naphthalate units. However, other components may be copolymerized within a range that does not impede the present invention, preferably within 20 mol%. In addition, polyester containing ethylene terephthalate as a main component is particularly desirable because its slipperiness and abrasion resistance are even better. The type of inert inorganic particles used in the present invention is not particularly limited, but synthetic calcium carbonate, titanium oxide, silica, and α-alumina are preferable, and in particular, when it is substantially spherical silica caused by colloidal silica, slipperiness , which is particularly desirable because the abrasion resistance becomes even better. The colloidal silica referred to herein is preferably particles produced from sodium silicate as a raw material in the process of removing alkaline content. Average particle size D of inert inorganic particles in the present invention
needs to be in the range of 0.05 to 0.6 μm, preferably 0.1 to 0.5 μm. If the average particle diameter D is smaller than the above range, the slip properties will be poor, and if it is larger, the abrasion resistance will be poor, which is not preferable. Two or more types of inert inorganic particles may be used in the present invention, or two or more types of the same type but different in average particle size may be used in combination. In such a case, when the particle size distribution has two or more peaks, the smallest of these peaks is taken as the average particle size D. The content of inert inorganic particles in the present invention is not particularly limited, but is 0.3 to 3.0% by weight, particularly 0.4 to 1.0% by weight.
% by weight is particularly desirable because the slip properties and abrasion resistance become even better. The film of the present invention has the above-mentioned composition as a main component, but other polymers may be blended within the range that does not impede the purpose of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. Inorganic or organic additives such as agents, nucleating agents, etc. may be added to the extent that they are normally added. The film of the present invention is a film in which the above composition is biaxially oriented. An unstretched film or a uniaxially oriented film is not preferred because it has poor slip properties and abrasion resistance. In addition, the plane orientation index representing the degree of biaxial orientation is not particularly limited, but is 0.935 to 0.975, particularly 0.940.
A range of 0.970 to 0.970 is particularly desirable because slipperiness and abrasion resistance become even better. Average surface roughness Ra in the width direction of the film of the present invention
(μm) and the average particle diameter D of the inert inorganic particles mentioned above
(μm) must satisfy the following formula. Ra≧0.04D...If the relationship between Ra and D does not satisfy the formula,
This is not preferable because it results in poor abrasion resistance. In addition,
The upper limit of Ra is not particularly limited, but usually
The manufacturing limit is about 0.05 μm. Next, the average height H of the surface protrusions of the film of the present invention
(μm) and the average surface roughness in the width direction Ra (μm) mentioned above
needs to satisfy the following formula, preferably the following formula-1. 2Ra≦H≦8Ra … 3Ra≦H≦7Ra …−1 The relationship between H and Ra is the above formula, preferably the formula −
If condition 1 is not satisfied, it is not preferable because a film that has both abrasion properties and abrasion resistance cannot be obtained. In addition, the density index of the film of the present invention is 0.02 to
A value in the range of 0.05 is particularly desirable because the slipperiness is even better. The film of the present invention is particularly desirable when the melt viscosity at 290°C and 200 sec ^-1 is in the range of 1,000 to 10,000 poise, particularly 2,000 to 7,000 poise, since the abrasion resistance becomes even better. Next, a method for manufacturing the film of the present invention will be explained. First, as a method for incorporating inert inorganic particles into a given polyester, they may be added before, during, or after polymerization, but they may be added in the form of a slurry to ethylene glycol, which is the diol component of the polyester. A method of dispersing and adding is effective in satisfying the relational expression of the present invention. Furthermore, as a method for adjusting the content of inert inorganic particles, a method of diluting a highly concentrated master pellet with polyester that does not substantially contain inert inorganic particles during film formation satisfies the relational expression of the present invention. It is effective for In this case, it is effective to set the inert inorganic particle content of the master pellet to 1 to 10% by weight, preferably 1 to 5% by weight, in order to satisfy the relational expression of the present invention. In addition, the melt viscosity of the polyester used in the master pellet, the copolymerization of other components, Adjusting the ratio is extremely effective in satisfying the relational expression of the present invention. 70−15Φ≦△Tcg≦100−2Φ Also, the crystallization parameter △Tcg of the polyester that dilutes this master pellet and does not contain substantially inert inorganic particles is 10°C or more than the crystallization parameter △Tcg of the master pellet. A method of reducing the size is extremely effective in satisfying the relational expression of the present invention. After thoroughly drying the pellets containing a predetermined amount of inert inorganic particles, the pellets are fed to a known melt extruder, extruded into a sheet through a slit die at 270 to 330°C, and solidified by cooling on a casting roll. At least make an unstretched film. Next, this 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. In the case of the sequential biaxial stretching method, it is common to stretch in the longitudinal direction and then in the width direction, but this order may be reversed. The conditions for biaxial stretching are the stretching method,
Although not necessarily constant depending on the type of polymer, it is usually 80 to 160℃ in both the longitudinal and width directions.
Preferably, the temperature is in the range of 90 to 150°C, and the stretching ratio is preferably in the range of 3.0 to 5.0 times, preferably 3.2 to 4.5 times. In addition, the stretching speed is 1×10 ³ to 7×10 ⁴
A range of %/min is preferred. Next, this stretched film is heat treated. In this case, the heat treatment conditions are preferably 180 to 250°C, particularly 190 to 230°C for 0.5 to 60 seconds under constant length. [Effect] As a result of controlling the average particle diameter of the inert inorganic particles and the film surface morphology, the true contact area when the film surface contacts another object becomes smaller, and the effects of the present invention are obtained. It is estimated that [Method of Measuring Characteristics and Method of Evaluating Effects] A method of measuring characteristic values and a method of evaluating effects of the present invention are as follows. (1) Average particle diameter D of inorganic fine particles Polyester was removed from the film using the plasma ashing method or the 0-chlorophenol dissolution method, dispersed in ethanol, and measured using the centrifugal sedimentation method (Horiba, Ltd., using CAPA500). It is the volume average diameter. (2) Content of inorganic fine particles: 0-chlorophenol 1.0 per 100g polyester
After adding and heating at 120℃ for 3 hours,
Using an ultracentrifuge 55P-72 manufactured by Co., Ltd., the obtained particles were
Vacuum dry at 100℃. When the fine particles are measured using a scanning calorimeter, if a melting peak corresponding to the polymer is observed, the fine particles are heated and cooled with 0-chlorophenol, and then the stretching separation operation is performed again. When the melting peak is no longer observed, the fine particles are considered to be precipitated particles. Normally, two stretching and separating operations are sufficient. (3) Glass transition point Tg, cold crystallization temperature Tcc Measured using a DSC (differential scanning calorimeter) manufactured by PerkinElmer. The DSC measurement conditions are as follows. That is, 10 mg of the sample was set in the DSC device, and after melting at a temperature of 300°C for 5 minutes,
Quench in liquid nitrogen. This rapidly cooled 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 exothermic peak temperature of crystallization from the glass 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) Surface projection diameter d Two-detector scanning electron microscope [ESM-
3200, manufactured by Elionix Co., Ltd.] and a cross-sectional measuring device [PMS-1, manufactured by Elionix Co., Ltd.], the height measurement value when scanning with the height of the smooth surface of the film surface as 0 is the gray value of 256 gradations. It is sent to an image processing device [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] as
Based on this gray value, the film surface protrusion image is reconstructed on IBAS2000. Next, the equivalent circle diameter was determined from the area of each protrusion obtained by binarizing the surface protrusion image with 10 or more gradations, and this was taken as the surface protrusion diameter. Among the 256 gray levels, the 0th level is represented by black, indicating the smooth surface of the film, and the 255th level is represented by white. Further, the height of one gradation is the value obtained by dividing the arbitrarily set value H by 256.
The arbitrary setting value H is the value of the film surface usually measured.
Use the value obtained by multiplying Ra (unit: μm) by 30. Furthermore, the magnification of the scanning electron microscope is selected to be between 2,000 and 8,000 times, and is changed depending on the Ra of the film surface. Measurements are taken horizontally in the scanning electron microscope field of view.
Measurements were made at 100 to 500 points, and 512 rows of these were measured in the vertical direction, giving the measured value per field of view. This measurement was performed for 1 mm ² , and the surface protrusion diameter indicated by the highest point of the peak of the surface protrusion diameter distribution curve, that is, the surface protrusion diameter with the highest frequency (number of protrusions) among all the surface protrusions, was defined as the surface protrusion diameter d. (5) Surface protrusion height H In the surface protrusion image expressed by 256 gray levels obtained from the two-detector type scanning electron microscope, cross-sectional measurement device, and image processing device, 2.
It is obtained by converting the maximum gray value of the valued protrusion portion into a protrusion height (unit: μm) (gray value×arbitrary setting value (H)×1/255). This measurement is performed for 1 ^mm2 , and the surface protrusion height with the highest frequency among all the surface protrusion heights is determined as the surface protrusion height H.
And so. (6) Planar orientation index Using an Atsube refractometer with sodium D line (wavelength 589 nm) as a light source, the refractive index in the thickness direction of the biaxially oriented film (referred to as A) and 10 after melt pressing were measured.
The refractive index (referred to as B) in the thickness direction of a non-oriented (amorphous) film prepared by quenching in water at ℃ was measured, and A/B was taken as the plane orientation index. Methylene iodide was used as the mounting solution, 25℃, 65%
Measured at RH. (7) Density index The density of the film measured using a density gradient tube made of n-heptane/carbon tetrachloride is d ₁ (g/cm ³ ).
The density index was defined as the difference (d ₁ - _{d 2} ) from the density d ₂ of a non-oriented (amorphous) film prepared by melt-pressing this film and then rapidly cooling it in water at 10°C. (8) Melt viscosity Using a high-temperature flow tester, the temperature was 290°C.
Measured at a shear rate of 200 sec ^-1 . (9) Surface average roughness Ra Measured using a stylus type surface roughness meter in accordance with JIS-B-0601. However, the cutoff was 0.08 mm and the measurement length was 1 mm (scanning in the width direction). (10) Slip property (coefficient of friction with metal guide) Using a tape runability tester model TBT-300 (manufactured by Yokohama System Research Institute Co., Ltd.), run the tape in an atmosphere of 20℃ and 60% RH, and check the initial μk. (friction coefficient) was determined from the following formula. μk=0.733og (T ₁ /T ₀ ) Here, T ₀ is the inlet tension and T ₁ is the outlet tension.
The guide diameter is 6mmφ, and the guide material is SUS27.
(Surface roughness 0.2S), wrapping angle is 180°, running speed is
3.3cm/sec. When the above μk was 0.30 or less, it was determined that the slip property was good, and when it exceeded 0.30, it was determined that the slip property was poor. This μk value of 0.30 is the critical point for whether or not troubles due to slippage will occur during processing steps such as printing and calendering, or during running when used as a magnetic tape. (11) Scraping resistance Press one blade perpendicularly against a film slit into a tape shape with a width of 1/2 inch.
Run 20cm while pushing in (running tension
500g, running speed 6.7cm/sec). At this time, the height of the scraped material on the film surface attached to the tip of the single blade was read using a microscope and determined as the amount of scraped material (unit: μm). If the amount of abrasion was 5 μm or less, the abrasion resistance was determined to be good, and if it exceeded 5 μm, the abrasion resistance was determined to be poor. This value of 5μm indicates whether or not the film surface will be scratched during processing steps such as printing and calendering, causing problems in the process or in product performance of magnetic media for short wavelength recording. This is the critical point when making a strict judgment. [Example] The present invention will be described based on an example. Examples 1-2, Comparative Examples 1-2 Ethylene glycol slurries of various colloidal silicas with different average particle diameters were subjected to transesterification and polycondensation with dimethyl terephthalate at a silica concentration of 1% by weight to form master pellets. I made it. The crystallization parameter △Tcg of this master pellet is
It was 80℃. This master pellet and pellets of polyethylene terephthalate containing no inert inorganic particles (ΔTcg: 68°C) were mixed to have various particle contents. This mixed pellet was dried under reduced pressure (3 Torr) at 180°C for 3 hours. This pellet is fed to an extruder and melt-extruded at 300℃,
Using an electrostatic casting method, the film was wound around a casting drum with a surface temperature of 30°C, and cooled and solidified to produce an unstretched film with a thickness of approximately 180 μm. This unstretched film was stretched 3.4 times in the longitudinal direction at 90°C. This stretching is performed using a difference in peripheral speed between two sets of rolls,
The stretching speed was 10,000%/min. This uniaxial film was stretched using a stenter at a stretching speed of 2000%/min.
Stretched 3.6 times in the width direction at ℃ and stretched 5 times at 210℃ under constant length.
Heat treatment was performed for seconds to obtain a film with a thickness of 15 μm. The average grain size D of silica, the average surface roughness Ra in the width direction, and the average height H of surface projections of these films are as shown in Table 1. When the average particle diameter was outside the range of the present invention, no matter how much Ra and H were modified, a film that had both slipperiness and abrasion resistance could not be obtained.

[Table] Examples 3 to 5, Comparative Examples 3 to 5 Ethylene glycol slurry of inert inorganic particles with different average particle diameters and types was mixed with a silica concentration of 1% by weight.
This was subjected to transesterification and polycondensation with dimethyl terephthalate to produce master pellets. At this time, by changing the polymerization conditions and copolymerization components,
As shown in Table 2, its crystallization parameters △
Changed Tcg. These master pellets and pellets of polyethylene terephthalate containing no inert inorganic particles (△Tcg 65°C) were mixed to have various particle contents, and in the same manner as in Example 1, pellets with different thicknesses were prepared.
A 15 μm biaxially oriented film was obtained. The average particle diameter D of the inert inorganic particles of these films, the average surface roughness Ra in the width direction, and the average height H of surface protrusions are as shown in Table 3. As can be seen from Table 3,
Even if the average roughness of the film surface is almost the same, D,
When Ra and H satisfied the relational expression of the present invention, a film that had both slipperiness and abrasion resistance was obtained; otherwise, a film that had both slipperiness and abrasion resistance could not be obtained. .

【table】

[Table] [Effects of the invention] As a result of controlling the average particle size of inert inorganic particles and the film surface morphology, the present invention provides a film that has both slipperiness and abrasion resistance, which will speed up future film processing processes. can correspond to Although the use of the film of the present invention is not particularly limited,
It is suitable for use in magnetic recording media, especially video tape base films, which require abrasion resistance during the processing process and product performance.

Claims (1)

[Scope of Claims] 1. A biaxially oriented film whose main components are a composition consisting of polyester and inert inorganic particles, the average particle diameter D (μm) of the inert inorganic particles and the surface in the width direction of the film. A biaxially oriented polyester film characterized in that the average roughness Ra (μm) and the average surface protrusion height H (μm) satisfy the following formula. 0.05≦D≦0.6 …… Ra≧0.04D …… 2Ra≦H≦8Ra ……