JPH05124100A - Biaxial oriented polyester film - Google Patents

Abstract

PURPOSE:To provide a high speed process for the production of a biaxial oriented polyester film protecting its surface from damage by controlling the average height of projections, the number of projections, the radius of curvature of the projection tops to the specific values, respectively, on the surface of the film which contains a specific amount of chain particles having a specific average radius of primary particles and a specific chain coefficient and inactive particles with a specific average radius. CONSTITUTION:A biaxial oriented polyester film is controlled to contain 0.005-5wt.% of chain particles having an average radius of primary particles of 1-400nm and a chain coefficient of 3-200 and inactive particles with an average radius of 0.3-2mum. The film surface is also controlled to have an average height of projections of 50-500nm, the number of projections of 1000/mm<2> or more, and the radius of curvature of projection tops of 0.3-3.0mum, where the branching index of chain particles is 1-50. This film is laminated at least on one surface of a polyester film. By the lamination, a special interaction is generated between the particles and the polyester film to form a special structure on the film surface, so that the surface is protected from damage even when the processing speed is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester suitable as a base film for packaging, capacitors and magnetic tapes.

[0002]

As a biaxially oriented polyester film, a film in which inert inorganic particles are contained in polyester is known (for example, JP-A-63-72729).

[0003]

However, as the process speed of film processing, especially the magnetic layer application in magnetic media applications, calendering and winding, cassette assembling process, etc., has increased, the roll surface and the guide which come into contact with the film surface It had the drawback of being easily scratched.

An object of the present invention is to solve the above problems and to provide a biaxially oriented polyester film which is less likely to be scratched on the surface of the film particularly in a high speed process (hereinafter referred to as excellent scratch resistance).

[0005]

The biaxially oriented polyester film of the present invention for this purpose has an average particle size of primary particles of 1 to 400 nm and chain particles of 0.005 to 0.005. A biaxially oriented polyester film containing 5% by weight and further containing inert particles having an average particle size of 0.3 to 2 μm, the average protrusion height of the film surface is 50 to 500 nm, and the number of protrusions is 1000. / Mm ²
As described above, the protrusion has a radius of curvature of 0.3 to 3.0 μm.

The polyester constituting the present invention is not particularly limited, but ethylene terephthalate, ethylene α, β
It is particularly preferable when at least one structural unit selected from -bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate and ethylene 2,6-naphthalate units is the main constituent component. Of these, polyesters containing ethylene terephthalate as a main constituent are particularly preferable. Two or more kinds of polyesters may be mixed, or a copolymerized polymer may be used, as long as the present invention is not impaired.

The film of the present invention must contain chain-like particles. When the film does not contain chain-like particles, scratch resistance becomes poor, which is not preferable. The chain-like particles contained in the film of the present invention may be in a rod-like state continuous in the length direction, or may be in a form in which fine particles are continuously connected, but fine particles are continuously connected. The form is preferable because the scratch resistance is better. Further, at this time, the fine particles may be bound to each other by covalent bond or ionic bond, or may be simply adhered, but in order to maintain the chain-like morphology in the film, It is more preferable that the fine particles forming the chain-like particles are bound to each other by a strong bond such as a covalent bond or an ionic bond. When the fine particles are linked and linked, the linked state may be linear, linked in a zigzag shape, or linked in a double chain or a triple chain.

The average primary particle diameter d of the chain-like particles in the present invention is 1 to 400 nm. If it is smaller than 1 nm, it is difficult to obtain a desired surface protrusion, and if it exceeds 400 nm, the protrusion height becomes high, particles and their vicinity are easily scraped off, and the protrusion height tends to vary, resulting in scratch resistance. The sex becomes poor.

The chain-like particles contained in the film of the present invention must have a chain coefficient of 3 to 200, preferably 5 to 100. If it is larger or smaller than this range, the scratch resistance becomes poor.

The chain-like particles may be branched in the middle, and it is particularly preferable that the chain-like particles have a branching index in the range of 1 to 50 because the scratch resistance is particularly good.

The hardness of the chain-like particles is 5 in Mohs' hardness.
Within the range of 10 to 10, the effect of surface reinforcement is large and the scratch resistance is further improved, which is particularly preferable.

The film of the present invention must contain the chain-like particles in an amount of 0.005 to 5% by weight, preferably 0.01 to 2% by weight. If the content is more or less than this range, the scratch resistance becomes poor. In addition, it is preferable to add a dispersant together with the particles because coarse agglomeration of the particles is prevented and scratch resistance is further improved.

In the film of the present invention, the scratch resistance becomes good when the inert particles having an average particle diameter of 0.3 to 2 μm are contained. When the addition amount is 0.05 to 2% by weight, scratch resistance becomes better, which is preferable. Examples of types of inert particles include titanium dioxide, silica, calcium carbonate, calcium phosphate, inorganic particles such as alumina and crosslinked spherical divinylbenzene particles,
Although there are organic particles such as spherical polyimide particles, calcium carbonate or crosslinked spherical divinylbenzene particles are particularly preferred. Further, internally precipitated particles may be used together.

The height of protrusions on the surface of the film of the present invention must be in the range of 50 to 500 nm, preferably 100 to 300 nm. If it is smaller or larger than this range, the scratch resistance becomes poor.

The number of protrusions on the surface of the film of the present invention is 100.
It should be 0 pieces / mm ² or more. If it is less than this range, the scratch resistance becomes poor, which is not preferable.

The radius of curvature of the projection tip on the surface of the film of the present invention must be in the range of 0.3 to 3.0 μm.
If it is smaller or larger than this range, the scratch resistance becomes poor.

Further, the film of the present invention may be a multi-layer laminated film. In this case, the average diameter of primary particles is 1 to 400 nm on at least one side of the film.
And a chain-like particle having a chain coefficient of 3 to 200 is 0.
A biaxially oriented laminated polyester film in which polyester films containing 005 to 5% by weight are laminated is preferable because scratch resistance is improved. At this time, the laminated thickness of the laminated film containing the chain-like particles is not particularly limited, but is preferably 400 nm or more, more preferably 500 nm or more, further preferably 1000 nm.
nm or more.

Next, the method for producing the film of the present invention will be described. The method for producing the chain-like particles used in the present invention is not particularly limited, but the following will be explained by taking the chain-like silica particles as an example. For example, when synthesizing particles using water glass or the like as a raw material by an ion exchange method or the like, a method of binding the particles by adding a cation or the like when the particles have grown to an appropriate size is effective. Further, at this time, if the particles once bonded are further grown as they are, the bonds between the primary particles become stronger, which is more preferable for obtaining the chain coefficient of the present invention.

Next, the chain-like particles are incorporated into a predetermined polyester. As a method of addition, it is preferable to use a method in which ethylene glycol, which is a diol component of polyester, is mixed and dispersed in the form of a slurry to be added, because the effect of the present invention is further enhanced. At this time, it is preferable to disperse fine glass beads or the like as a medium so that the chain coefficient falls within the range of the present invention. Further, kneading the particles into the polymer using a vent type twin-screw kneading extruder is effective in keeping the chain coefficient within the range of the present invention. Furthermore, when the polymer thus obtained is re-kneaded with a vent type twin-screw kneading extruder again, the particles are refined,
It is particularly effective to set the average height of protrusions on the film surface, the number of protrusions, and the radius of curvature of protrusions within the scope of the present invention. Further, as a method for adjusting the content of particles, it is preferable to use a method of diluting a high-concentration master pellet during film formation, because the effect of the present invention is further enhanced.

Next, the pellets of the polyester are used to prepare a biaxially oriented polyester film. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried, and then supplied to a known melt extruder, extruded into a sheet from a slit-shaped die, and cooled and solidified on a casting roll. Make an unstretched film. A draft ratio (slit width of die / thickness of unstretched film) at the time of casting is as high as about 3 to 10 times, which is suitable for keeping the chain coefficient of the particles within the range of the present invention.

Next, the unstretched film is biaxially stretched to be biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, a sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction is used, and stretching in the longitudinal direction is performed in 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 generally stated, but usually the first step is 50 to 1
It is effective to set the temperature to 30 ° C. and raise the temperature from the second stage onward. The longitudinal stretching speed is 5000 to 50000% /
The range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The draw ratio is 3.0
The range of up to 5.0 times is appropriate. The stretching speed in the width direction is
The range of 1000 to 20000% / min and the temperature of 80 to 160 ° C are suitable. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., especially 1
The range of 80 to 200 ° C. and the time of 0.2 to 20 seconds are suitable.

[Measurement Method of Characteristic] The characteristic value of the present invention is based on the following measuring method and evaluation criteria. (1) Average Diameter, Chain Coefficient, and Branching Index of Primary Particles of Chain-Shaped Particles A film containing particles is made into an ultrathin section of about 1000 angstroms to 5000 angstroms in the thickness direction, and a transmission electron microscope (for example, JEM manufactured by JEOL Ltd. is used. -12
(For example, 00EX), the particle size is observed at a magnification of about 50,000 to 500,000 times. At this time, the size of the smallest particle that cannot be further divided into particles is taken as the primary particle size, and the average value in 50 fields of view of the microscope is taken as the average diameter of the primary particles. However, when it is difficult to confirm the primary particles because the primary particles are strongly bound by covalent bonds etc.,
The thickness of particles connected in a chain is regarded as a primary particle. Further, the longest part of the particles connected in a chain form is taken as the major axis, and how many primary particles are connected in the major axis direction is measured, and the value averaged over 50 fields of view of the microscope is taken as the chain coefficient. When it is difficult to confirm the primary particles because the primary particles are strongly bound by a covalent bond or the like, a value obtained by dividing the major axis of the chain-like particles by the primary particle size (thickness) is used as the chain coefficient. Further, the longest part of the particles connected in a chain form was defined as the main chain, and the number of branches branched from the main chain was defined as the branching index.

(2) Average Diameter of Inert Particles A film containing particles is made into an ultrathin section of about 1000 angstroms to 5000 angstroms in the thickness direction, and a transmission electron microscope (for example, JEM-12 manufactured by JEOL Ltd.) is used.
(For example, 00EX), the inactive particles are observed at a magnification of about 50,000 to 500,000 times and the average diameter thereof is determined. At this time, chain particles are not added to the average diameter of the inert particles.

(3) Content of Particles A solvent in which polyester is dissolved but not particles is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is taken as the particle content.
If necessary, pyrolysis gas chromatography, infrared spectroscopy, fluorescent X-ray analysis, Raman scattering, SEM-X
It can also be quantified using MA or the like. The inclusion of particles in the laminated portion and the base layer portion can be distinguished by scraping off each laminated portion. Further, if necessary, it can be calculated from the number of particles observed in each cross section using a TEM.

(4) Average protrusion height on film surface, number of protrusions 2 Detector type scanning electron microscope (ESM-3200,
Elionix Co., Ltd. and cross-section measuring device (PMS-1,
In Elionix Co., Ltd., the measured value of the height of the protrusion when the flat part of the film surface is set to 0 and the measured value of the height of the projection is analyzed by an image analyzer (IBAS2000, Carl Zeiss Co., Ltd.).
, And reconstruct the film surface projection image. Next, the projection portion is binarized in this surface projection image, the highest value among the individual projection portions is set as the height of the projection, and this is obtained for each projection. This measurement was repeated 50 times by changing the place. The number of protrusions measured was regarded as a protrusion having a height of 0.3 μm or more, and the number of protrusions was determined. The scanning electron microscope usually has a magnification of 3000 times, depending on the size of the protrusion
The optimum magnification can be selected in the range of 000 to 5000 times.

(5) Radius of curvature at the tip of the protrusion The radius of curvature at the tip of the protrusion was determined by the following definition for individual protrusions having a size of 30 nm or more measured by the same method as in the above (4). In the cross-sectional curve (y = f (x)) of the protrusion passing through the apex of the protrusion on the image analysis device, the value of the protrusion height corresponding to the portion of 9 pixels in total including the apex of the protrusion as the center is calculated as follows. Interpolated by the method of least squares, the radius of curvature βMD in the film longitudinal direction according to the following equation,
The radius of curvature βTD in the film width direction orthogonal to βMD was calculated. Next, find the radius of curvature β of the protrusion tip from this value,
Similar to the measurement in (4), the location was changed and the measurement was repeated 50 times and averaged. y = ax ² + bx + c βMD, TD = 1 / | y ″ | β = 2βMD · βTD / (βMD + βTD)

(6) Runnability film is slit into 1/2 inch, and tape runnability tester TBT-300 type (manufactured by Yokohama System Research Co., Ltd.)
Was used to run in an atmosphere of 20 ° C. and 60% RH, and the initial friction coefficient μK was calculated from the following formula. μK = 0.733 log (T ₁ / T ₂ ), where T ₂ is the inlet tension and T ₁ is the outlet tension. The guide diameter is 6 mmφ, the guide material is SUS27 (surface roughness 0.2S), the winding angle is 180 °, and the running speed is 3.
It is 3 cm / sec. When the above μK was 0.35 or less, the runnability was good. The value of μK of 0.35 is a critical value of whether or not the running property during film processing or as a product becomes extremely poor.

(7) Surface Roughness It was measured using a high precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions are as follows, and the average value of 20 measurements was taken as the surface roughness.・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measuring length: 1 mm ・ Cutoff value: 0.08 mm

(8) Scratch resistance The film is slit into a tape having a width of 1/2 inch, the tape guide pin of the video cassette (surface roughness Rt is 2500 nm at Rt of 90 g and running speed of 250 m / min).
A guide pin made of stainless steel having a surface of a certain degree was run at a winding angle of 60 °, and the amount of scratches produced at that time was visually determined according to the following criteria. No scratches ・ ・ ・ 5 points Shallow scratches ・ ・ ・ ・ ・ ・ ・ ・ 3 points Many deep scratches ・ ・ ・ 1 point Also, 5 points and 3 points are 4 points in between. 2 between the points, 3 points and 1 point
It was a point. The evaluation was shown as an average value measured 10 times, and at this time, 3 points or more were good scratch resistance and 3 points or less were bad scratch resistance.

[0030]

【Example】

Example 1 (Tables 1 and 2) Chain-like silica particles were dispersed in ethylene glycol by a media dispersion method and polymerized with ethylene glycol and dimethyl terephthalate to obtain polyethylene terephthalate pellets containing chain-like particles. It was The content of particles relative to polyethylene terephthalate is 1.0% by weight.
Met. The pellets were kneaded again with a vent type twin-screw extruder. Further, crosslinked spherical civinylbenzene / ethylbenzene copolymer particles having an average particle diameter of 0.45 μm were dispersed in ethylene glycol to obtain polyethylene terephthalate pellets in the same manner. The content of the cross-linked spherical sivinylbenzene / ethylbenzene copolymer particles with respect to polyethylene terephthalate was also 1.0% by weight.

3 pellets containing the above chain-like particles
0 parts by weight, 40 parts by weight of pellets containing cross-linked spherical divinylbenzene / ethylbenzene copolymer particles, and 30 parts by weight of pellets containing no particles are mixed together to give 18
After drying under reduced pressure (3 Torr) at 0 ° C for 3 hours, it is supplied to an extruder, filtered with high precision, melt-extruded at 300 ° C, and wrapped around a casting drum with a surface temperature of 30 ° C using an electrostatic cast method to cool. The film was solidified to prepare an unstretched film having a thickness of about 180 μm. The draft ratio at this time is 6.7.
Met. This unstretched film was divided into three stages in the longitudinal direction and stretched 4.2 times at 110 ° C. This uniaxial film was stretched 3.6 times in the width direction at 100 ° C. using a stenter and heat-treated at 200 ° C. for 5 seconds under a fixed length to give a thickness of 15 μm.
m film was obtained.

The average diameter of the primary particles of the chain-like particles contained in this biaxially oriented polyester film was 30 nm, the chain coefficient was 25, and the branching index was 9. The height of protrusions on the front surface of the film was 130 nm, the number of protrusions was 15,000 / mm ² , the radius of curvature of the front protrusion was 0.5 μm, and the average surface roughness was 0.0153 μm.

Next, the scratch resistance of this film was measured and found to be 4.8, which was very good. The running property was also 0.20, which was very good. As described above, it can be seen that when a chain-shaped particle having a specific structure and a specific particle size is contained in the film in a specific amount, the film can be excellent in scratch resistance.

Examples 2 to 6 and Comparative Examples 1 to 7 (Tables 1 and 2) The particles to be added and the film forming conditions were variously changed, and the average diameter, chain coefficient and branching index of the primary particles of the chain-like particles contained were changed. The scratch resistance was good when all of the content, the average height of protrusions on the surface, the number of protrusions, and the radius of curvature of the protrusion tip were within the range of the present invention (Examples 2 to 6).

However, the average diameter of the primary particles of the chain-like particles,
When any of the chain coefficient, the content, the average height of protrusions on the surface, the number of protrusions, and the radius of curvature of the protrusion tip is out of the range of the present invention, the scratch resistance could not be satisfied (Comparative Examples 1 to 7). ).

[0036]

Since the biaxially oriented polyester film of the present invention is a film containing a specific amount of chain-like particles having a specific structure, the particles and the polyester film show a unique interaction, and the surface of the film is shown. Since the structure is peculiar, even if the processing speed is increased in the film processing step, there is no trouble such as scratches on the surface due to excellent scratch resistance. Moreover, since it has good running properties and transparency, it has excellent effects such as being suitable for packaging materials and industrial materials.

[0037]

[Table 1]

[0038]

[Table 2]

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Claims (3)

[Claims] 1. The average particle diameter of primary particles is 1 to 400 nm,
A chain-like particle having a chain coefficient of 3 to 200 is 0.005
A biaxially oriented polyester film containing 5% by weight and further containing inert particles having an average particle size of 0.3 to 2 μm, wherein the average protrusion height on the surface of the film is 50 to 500 n.
m, the number of protrusions is 1000 / mm ² or more, and the radius of curvature of the protrusion tip is 0.3 to 3.0 μm. A biaxially oriented polyester film. 2. The biaxially oriented polyester film according to claim 1, wherein the chain-like particles have a branching index of 1 to 50. 3. A biaxially oriented polyester film comprising the film of claim 1 or 2 laminated on at least one surface layer.