JPH0659679B2 - Biaxially oriented thermoplastic resin film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a biaxially oriented thermoplastic resin film, and more particularly to a biaxially oriented thermoplastic resin film having a laminated film structure with improved surface characteristics.

[Prior Art] As a biaxially oriented thermoplastic resin film having improved surface properties, a film in which polyester, which is a thermoplastic resin, contains substantially spherical silica particles derived from colloidal silica is known. (For example, JP-A-59-1
71623 publication).

In such a biaxially oriented thermoplastic resin film,
With the silica particles contained, it is possible to form protrusions on the film surface and reduce the friction coefficient of the surface to improve handling and running properties.

[Problems to be Solved by the Invention] However, in the conventional biaxially oriented thermoplastic resin film described above, the contained silica particles are distributed substantially randomly throughout the thickness direction of the film. There is a limit to the increase in the density of the protrusions, and the heights of the protrusions also vary considerably at random. On the surface of a film having such projections, the tip surface of the projections mainly comes into contact with an object (for example, a roll in the processing step). However, if the density of the projections is low, the contact area by the tip surface becomes small and the contact surface Since the pressure becomes high, a problem may occur in the abrasion resistance of the film surface, and the film surface may be easily scraped. In addition, if the height of the protrusions on the film surface is uneven, it is easy to scrape high-height protrusions.
For example, as the process speed increases, such as a printing process in packaging applications, a magnetic layer coating / calendering process in magnetic recording media applications, or a heat-sensitive transfer layer coating in heat-sensitive transfer applications, there is a possibility that the film surface may be scratched by the contacting rolls. .

The present invention focuses on the above problems, in forming the protrusions by the particles contained on the surface of the biaxially oriented thermoplastic resin film, while achieving a high density of the protrusions and a uniform protrusion height, It is another object of the present invention to make the surface of the film on which the protrusions are formed more difficult to scrape and scratch.

[Means for Solving the Problems] A biaxially oriented thermoplastic resin film of the present invention which meets this object is a thermoplastic resin obtained by co-extruding a film containing a thermoplastic resin A and inert particles A and B as main components. A biaxially oriented thermoplastic resin film having a thickness of 0.01 to 5 μm laminated on at least one surface of a film containing B as a main component, wherein the average particle diameter of the inactive particles A is a film layer thickness of the thermoplastic resin A. 0.1 to 10 times the average particle size, and the inactive particles B are agglomerated particles in which primary particles having an average particle size smaller than the average particle size of the inactive particles A are arranged in a large number without any directionality. Become.

The thermoplastic resin A constituting the present invention is not particularly limited to polyester, polyolefin, polyamide, polyphenylene sulfide, etc., but especially polyester,
Among them, at least one structural unit selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate and ethylene 2,6-naphthalate units is the main constituent component. In this case, abrasion resistance and scratch resistance (also referred to as scratch resistance) are further improved, which is desirable. Further, when the thermoplastic resin constituting the present invention is crystalline, the abrasion resistance and the scratch resistance are further improved, which is extremely desirable. The crystallinity referred to here means that it is not so-called amorphous, and quantitatively, the cold crystallization temperature Tcc in the crystallization parameter is detected, and the crystallization parameter ΔTcg is 15
It is below 0 ° C. Furthermore, when the heat of fusion (change in enthalpy of fusion) measured by a differential scanning calorimeter shows a crystallinity of 7.5 cal / g or more, abrasion resistance and scratch resistance are further improved, which is extremely desirable. Further, in the case of polyester containing ethylene terephthalate as a main constituent component, abrasion resistance and scratch resistance are further improved, which is particularly desirable. Two or more kinds of thermoplastic resins may be mixed, or a copolymerized polymer may be used, as long as the present invention is not impaired.

The shape of the inert particles A in the thermoplastic resin A of the present invention is not particularly limited, but particles having a particle size ratio (major axis / minor axis of particles) of 1.0 to 1.3 in the film, particularly spherical particles. In this case, the film surface is less likely to be scratched and abrasion resistance is further improved, which is desirable.

Further, the inert particle A has a single particle index of 0 in the film.
When it is 7 or more, preferably 0.9 or more, scratch resistance and abrasion resistance are further improved, which is particularly desirable.

The type of the inert particles A in the present invention is not particularly limited, but alumina silicate, silica in which primary particles are aggregated, internally precipitated particles, and the like are not preferable in order to satisfy the above preferable particle characteristics. Preferable particles include substantially spherical silica particles derived from colloidal silica and particles formed by a cross-linked polymer (for example, cross-linked polystyrene). Particularly, the temperature at the time of 10% weight loss (thermogravimetric analyzer in nitrogen, Shimadzu TG- Measured using 30 M. Heating rate is 20 ° C / min)
In the case of crosslinked polymer particles having a high degree of crosslinking up to 380 ° C or higher, scratch resistance and abrasion resistance are further improved, which is particularly desirable. In the case of spherical silica due to colloidal silica, it was manufactured by the alkoxide method,
In the case of a substantially spherical silica having a low sodium content, scratch resistance and abrasion resistance are further improved, which is particularly desirable. However, other particles such as calcium carbonate, titanium dioxide, and alumina can be sufficiently used by appropriately controlling the film thickness and the average particle size.

The size of the inactive particles A is such that the average particle diameter in the laminated film containing the inactive particles is 0.1 to the thickness of the laminated film.
10 times, preferably 0.5 to 5 times, more preferably 1.1 to
The range is tripled. The thickness of the laminated film layer is 0.01 ~
It is set to 5 μm. If it is thinner than this, the film layer is likely to open, and the scratch resistance deteriorates. When the ratio of the average particle diameter of the inactive particles A to the thickness of the laminated film is smaller than the above range, the effect of forming surface projections by the inactive particles A becomes small and the height of the projections becomes uneven. However, the scratch resistance and the abrasion resistance become poor, and even if it is large, the projections formed are easily broken and the scratch resistance and the abrasion resistance become poor, which is not preferable.

The average particle size (diameter) of the inactive particles A in the thermoplastic resin A in the film is basically larger than the average particle size of the primary particles of the inactive particles B described later. More preferably, it is in the range of 0.007 to 0.5 μm, preferably 0.02 to 0.45 μm, because scratch resistance and abrasion resistance are further improved, which is desirable.

That is, the laminated film layer in the present invention contains the inert particles A having an average particle diameter in the vicinity of or larger than the thickness of the film. In other words, the ultra-thin laminated film contains fine inert particles A having an average particle diameter in the vicinity of or larger than the thickness of the film. Therefore,
With respect to the entire biaxially oriented thermoplastic resin film, the inactive particles A can be distributed substantially in the laminated film layer in the thickness direction thereof. As a result, the particle density in the laminated film can be easily increased, and the density of protrusions formed on the surface of the film can be easily increased. In addition, the inert particles A are contained in the above-mentioned laminated film, whereby the position is regulated in the thickness direction with respect to the entire biaxially oriented thermoplastic resin film, and the thickness and the average of the laminated film are averaged. Since the particle size has the above-described relationship, the height of the surface protrusions formed by the particles becomes extremely uniform.

Inert particles B are further contained in the film layer of the thermoplastic resin A.

The average particle size of the primary particles of the inert particles B is basically much smaller than the average particle size of the inert particles A, and a large number of primary particles are arranged without directivity. Thus, it is contained in the film in the form of beaded or mesh-like aggregated particles. The average particle diameter of the primary particles of the inert particles B is preferably in the range of 5 to 100 nm in order to form the above-mentioned beaded or mesh-like aggregated particle state. The inert particles B composed of such agglomerated particles increase the holding strength of the inert particles A in the laminated film by continuously extending around the inert particles A, and at the same time, the laminated film itself. To reinforce. That is,
The inert particles A are mainly responsible for forming film surface protrusions,
The inert particles B are responsible for the holding strength of the inert particles A and the reinforcement of the laminated film material. As a result, as described above, the surface protrusions formed at a uniform height and a high density by containing the inert particles A in the ultra-thin laminated film are formed into the inert particles B.
Due to the presence of the above, the abrasion resistance and scratch resistance of the film surface are further improved.

The type of the inert particles B is not particularly limited as long as it forms a beaded or mesh-like aggregated particle as described above, but preferable ones are δ-alumina, γ-alumina, zirconia, beaded silica, and meshes. The titanium dioxide may be mentioned.

The content of the inert particles B in the laminated film is 0.05.
It may be as small as ~ 1% by weight. If it is less than this range, the reinforcing effect cannot be expected, and if it is more than the above range, a large amount of fine particles are contained, so that the laminated film layer becomes rather brittle and may be easily scraped.

The film containing the thermoplastic resin A and the inert particles A and B as the main components is laminated on at least one surface of the film containing the thermoplastic resin B as the main component.

The thermoplastic resin B is the same as the above-mentioned thermoplastic resin A, and the thermoplastic resin B and the thermoplastic resin A may be the same kind or different. The film layer of the thermoplastic resin A is laminated on both sides or one side of the film layer of the thermoplastic resin B. In other words, the laminated structure is A / B
In the case of / A and A / B, of course, A / B / C in which a C layer having a surface state different from A is provided on the surface opposite to A, or a multilayer structure of more than that may be used. (here,
Even if the type of thermoplastic resin for each of A, B, and C is the same,
It may be different. Further, at least one surface needs to be the A layer. ) Also as the thermoplastic resin B, a crystalline polymer is desirable. Specific examples thereof include polyester, polyamide, polyphenylene sulfide, and polyolefin. In the case of polyester, scratch resistance and abrasion resistance are further improved, which is particularly desirable. In addition, as the polyester, at least one structural unit selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, and ethylene 2,6-naphthalate units is mainly used. When it is used as a constituent component, scratch resistance becomes particularly good, which is desirable.

However, other components may be copolymerized within a range that does not impair the present invention and a range that does not impair the desired crystallinity, and preferably within 5 mol%.

The thermoplastic resin B of the present invention may also be blended with another type of polymer within a range that does not impair the object of the present invention, and an organic additive such as an antioxidant, a heat stabilizer, a lubricant or an ultraviolet absorber may be added. The agent may be added to the extent that it is usually added.

It is not particularly necessary for the film containing the thermoplastic resin B as a main component to contain inert particles, but when this film forms one side of the film surface, the average particle size is 0.007-
Inert particles of 2 μm, especially 0.02 to 0.45 μm, 0.001 to 0.
2% by weight, especially 0.005-0.15% by weight, and even 0.005-
When the content is 0.12% by weight, not only the coefficient of friction and scratch resistance are further improved, but also the winding shape of the film is improved, which is highly desirable. As the type of the inert particles contained, it is desirable to use those which are preferably used as the inert particles A contained in the thermoplastic resin A.
The types and sizes of particles contained in the thermoplastic resins A and B may be the same or different.

Thermoplastic resin A containing inert particles A and B as described above
And thermoplastic resin B are laminated by coextrusion, formed into a sheet, and then biaxially stretched to obtain a biaxially oriented thermoplastic resin film. Laminating by coextrusion in the present invention means a thermoplastic resin A containing inert particles A and B,
Extruding the thermoplastic resin B with different extruders,
It means stacking these before discharging the laminated sheet from the die. This lamination may be performed in a die for forming and discharging into a sheet (for example, a manifold), but since the laminated film layer is extremely thin as described above, it is performed in a polymer tube before being introduced into the die. It is preferable. In particular, it is particularly preferable that the laminated portion in the polymer tube is formed in a rectangular shape because the laminated portion can be uniformly laminated in the width direction and the subsequent biaxial stretching can be easily performed. The molten polymer laminated in the polymer tube rectangular lamination portion is widened to a predetermined width in the seal width direction by the manifold in the die, discharged in a seal shape from the die, and then biaxially stretched. Therefore, even if the laminated film layer after biaxial orientation is extremely thin, since the inert particle-containing thermoplastic resin polymer is laminated in a considerable thickness in the rectangular laminated portion in the polymer tube, it is easy to And it can be laminated accurately.

The biaxially oriented thermoplastic resin film of the present invention preferably has a Young's modulus in the width direction of 400 kg / mm ² or more, more preferably in the width direction and the longitudinal direction in video tape applications and the like. Is preferably 400 kg / mm ² or more. By laminating in the polymer tube having the above-mentioned rectangular laminating section, uniform laminating is possible, and even if the laminated film layer is an extremely thin layer, the stretching ratio in the width direction can be at least 3 times. 400 kg / mm ²
The above Young's modulus in the width direction can be easily achieved. When the Young's modulus is lower than the above value, when the wide film is slit narrowly according to the intended use, the powder falling property from the slit film end face is poor, and the generated film powder may cause various troubles. Therefore, it is not preferable. If the Young's modulus in the width direction and the longitudinal direction is lower than the above values, the dubbing resistance and dropout characteristics of the video tape may deteriorate, which is not preferable.

Further, in the biaxially oriented thermoplastic resin film of the present invention, it is preferable that the particle concentration ratio of the inactive particles A in the surface layer on the laminated film side containing the inactive particles A and B is 0.1 or less. This surface layer particle concentration ratio indicates how the inactive particles forming the film surface projections are covered with the thin film of the thermoplastic resin A on the film surface as shown in the measuring method described later. The higher the degree of direct exposure to the surface, the higher the surface layer particle concentration ratio,
Although surface protrusions are formed, the higher the degree of coverage with the thin film of the thermoplastic resin A, the lower the surface layer particle concentration ratio. In the present invention, the inactive particles A mainly form the protrusions on the film surface, but the inactive particles A are covered with the thin film of the thermoplastic resin A by the effect of the rectangular lamination, so that the inactive particles A are Even when the particles are densely distributed in the ultra-thin laminated film layer, the particles are firmly held in the laminated film layer, and by extension, in the base film layer of the thermoplastic resin B. Therefore, by setting the surface layer particle concentration ratio to the above value or less, the particles are prevented from falling off, and the scratch resistance and abrasion resistance of the film surface are maintained high.
Such a surface layer particle concentration ratio can be achieved by performing lamination by coextrusion. By the way, also by the coating method, a film similar to the present invention, namely,
It is possible to coat the base film layer with a resin layer with an extremely thin thickness and to contain the inert particles in the resin layer, but the surface layer particle concentration ratio becomes extremely high (that is, the particles are substantially on the surface). The degree of direct exposure becomes extremely high), and only the surface of the film of the invention is extremely brittle.

In the film of the present invention, the height of the surface protrusions formed by the inert particles A is not particularly limited, but in order to obtain the desired effect of improving slipperiness (reduction of friction coefficient) and the like, the protrusion average It is preferable to set the average particle diameter of the inert particles A and the thickness of the laminated film layer of the thermoplastic resin A so that the height is 0.3 times or more the average particle diameter of the inert particles A. Further, in order to obtain uniform and high-density projections, the standard deviation of the particle size distribution of the inert particles A itself is preferably 0.5 or less.

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

First, as a method of incorporating the inert particles A and B into the thermoplastic resin A, either after the polymerization, during the polymerization, or before the polymerization may be performed, but the inert particles A may be added to the polymer by using a vent type twin-screw extruder. The method of kneading B and B at the same time is effective for obtaining a film having a surface morphology within the scope of the present invention. Further, as a method for adjusting the content of particles, a high-concentration master is prepared by the above method, and the content of particles is diluted by a thermoplastic resin that does not substantially contain inert particles during film formation. The adjusting method is effective for obtaining the film having the surface morphology within the scope of the present invention. Furthermore, the method of adjusting the melt viscosity, copolymerization component, etc. of the high concentration master polymer of particles to keep the crystallization parameter ΔTc g in the range of 30 to 80 ° C. does not cause stretching breakage and the surface morphology within the range of the present invention. It is effective for obtaining a film.

Thus, after the pellet A containing the inert particles A and B is sufficiently dried, it is supplied to a known melt extruder and melted at a temperature not lower than the melting point and not higher than the decomposition point of the thermoplastic resin, and the other substantially unmelted. A thermoplastic resin B containing no active particles (the type thereof may be the same as or different from the thermoplastic resin containing inert particles) is supplied to the laminating apparatus as described above, and a sheet is produced from a slit-shaped die. The film is extruded and cooled and solidified on a casting roll to prepare an unstretched film. That is, these thermoplastic resins are laminated using two or three extruders, a merging block or a die for two or three layers. When the confluent block method is used, the laminated portion should be rectangular as described above, and the difference (absolute value) in melt viscosity between the two thermoplastic resins should be in the range of 0 to 2000 poise, preferably 0 to 1000 poise. Is effective for industrially producing a film having a surface morphology within the scope of the present invention with stability and without unevenness in the width direction.

Next, this multilayer unstretched film is biaxially stretched and biaxially oriented. The biaxial stretching method may be simultaneous biaxial stretching or sequential biaxial stretching method, but in the case of the sequential biaxial stretching method of stretching in the longitudinal direction and the width direction in order, a film having a surface morphology within the scope of the present invention is stabilized. Therefore, it is effective for industrial production without unevenness in the width direction. In the case of sequential biaxial stretching, stretching in the longitudinal direction is divided into three stages, particularly four or more stages, in the range of 40 to 150 ° C., and at a stretching rate of 1000 to 50,000% / min, 3 to 6
The doubling method is effective for obtaining a film having a surface morphology within the scope of the present invention. The stretching temperature and speed in the width direction are 80
A range of up to 170 ° C and 1000 to 20000% / min is suitable. The stretching ratio is preferably 3 to 10 times. If necessary, it can be further stretched in at least one of the longitudinal direction and the width direction. In any case, the point of the present invention is to provide an extremely thin layer containing the inert particles A and B and then perform an area stretching ratio (longitudinal direction ratio × width direction ratio) of 9 times or more. Next, this stretched film is heat-treated. The heat treatment conditions in this case are 140 to 280 ° C. in any state of relaxation in the width direction, fine stretching and under constant length,
The temperature is preferably in the range of 160 to 220 ° C. for 0.5 to 60 seconds, but it is preferable to use microwave heating together with the heat treatment because a film having a surface morphology within the range of the present invention can be easily obtained.

The feature of the production method of the film of the present invention is that a high concentration particle polymer having a specific range of thermal characteristics prepared by a special method is used,
It is a method of biaxially stretching the film after providing an extremely thin layer containing inert particles.In the film forming process, the film is uniaxially stretched and then subjected to coating or the like, or a biaxially stretched film. The performance of the film of the present invention is far inferior to the laminated film produced by coating the film of the present invention, and the film of the present invention is excellent in terms of cost.

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows.

(1) Average particle size of particles Polyester is removed from the film by a plasma low temperature ashing method (for example, PR-503 type manufactured by Yamato Scientific Co., Ltd.) to expose the particles. The processing conditions are selected such that polyester is incinerated but particles are not damaged. This is SEM
Observe with a (scanning electron microscope), connect the image of particles (light and shade of light generated by particles) to an image analyzer (eg QTM900 made by Cambridge Instruments), change the observation point and perform the following numerical processing with 5000 or more particles The number average diameter D thus obtained is taken as the average particle diameter.

D = ΣD _i / N Here, D _i is the equivalent circle diameter of the particles, and N is the number. For the inert particles B, the average particle size of the primary particles is measured.

(2) Content of particles A solvent in which the polyester is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is defined as the particle content.
In some cases, the combined use of infrared spectroscopy is also effective.

(3) Crystallization parameter ΔTc g It was measured using DSC (Differential Scanning Calorimeter) II type manufactured by Perxielmer. The measurement conditions of DSC are as follows. That is, set 10 mg of sample in the DSC device and
After melting for 5 minutes at a temperature of ° C, it is quenched 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. The difference between Tcc and Tg (Tcc-Tg) is the crystallization parameter ΔT.
Define as c g.

(4) Average height of surface protrusions A flat surface of the film surface in a two-detector scanning electron microscope [ESM-3200, Elionix Co., Ltd.] and a cross-section measuring device [PMS-1, Elionix Co., Ltd.] The height measurement value of the protrusions when the height is 0 is sent to the image processing device [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] to reconstruct the film surface protrusion image on the image processing device. Next, the equivalent circle diameter is calculated from the area of each protrusion obtained by binarizing the protrusion portion in this surface protrusion image, and this is made the average diameter of the protrusion. In addition, the highest value among the binarized individual projection portions is set as the height of the projection, and this is obtained for each projection. This measurement was repeated 500 times at different locations, the number of protrusions was determined, and the average value of the heights of all the measured protrusions was taken as the average height. The magnification of the scanning electron microscope is selected to be a value between 1000 and 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (W
TOPO-3D made by YKO, objective lens: 40 to 200 times,
The height information obtained by using a high-resolution camera is effective) may be read as the SEM value and used.

(5) Surface Layer Particle Concentration Ratio Using the secondary ion mass spectrum (SIMS), the particle concentration is defined as the concentration ratio of the highest concentration element of the elements in the film and the carbon element of polyester,
Analyze in the thickness direction. The ratio of the particle concentration A at the outermost surface particle concentration (point at depth 0) measured by SIMS and the maximum concentration B obtained by continuing the analysis in the depth direction,
A / B was defined as the surface particle concentration ratio. The measuring device and conditions are as follows.

Measuring instrument Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measuring conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12KV Primary ion current: 200nA Raster area: 400 μm □ Analysis area : Gate 30% Measuring degree of vacuum: 6.0 × 10 ⁹ Torr E-GUN: 0.5KV-3.0 A (6) Single particle index The cross section of the film is photographically observed with a transmission electron microscope (TEM) to detect particles. If the observation magnification is set to about 100,000, one particle that cannot be further divided can be observed. When the total area occupied by particles is A and the area occupied by aggregates in which two or more particles are aggregated is B, (A
-B) / A is a single particle index. The TEM conditions are as follows: 1 field of view area: 2 μm ² 500 fields of view are measured by changing the location.

-Apparatus: JEM-1200EX manufactured by JEOL-Observation magnification: 100000 times-Slice thickness: Approximately 1000 angstroms (7) Particle size ratio Average value of major axis of individual particles in the above measurement (1) /
It is the ratio of the average value of the minor axis.

That is, it is calculated by the following formula.

Major axis = ΣD1 _i / N long diameter short diameter _{= ΣD2 i / N D1 i,} D2 i each individual particle (maximum diameter), short diameter (the shortest diameter), N is the total number.

(8) Young's modulus In accordance with the method specified in JIS-Z-1702, using an Instron type tensile tester, 25 ℃, 65 ℃
It was measured by RH.

(9) Thickness of Thermoplastic Resin A Layer in Laminated Film Using secondary ion mass spectrometer (SIMS), the element derived from the highest concentration of particles in the film and the carbon element of polyester The concentration ratio (M ⁺ / C ⁺ ) is defined as the particle concentration, and analysis is performed in the depth (thickness) direction from the surface of the thermoplastic resin A layer. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration once reaching the maximum value at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth [I
I] (here, II> I) was taken as the laminated thickness. The conditions are the same as in measurement method (5).

If the particles contained most in the film are organic polymer particles, it is difficult to measure by SIMS, so XPS (X-ray photoelectron spectroscopy), while etching from the surface,
It is also possible to measure the depth profile of the particle concentration by IR (infrared spectroscopy) or a confocal microscope, and obtain the layer thickness by the same method as above.

Further, the laminated thickness of the thermoplastic resin A may be obtained by observing the cross section of the film or by a thin film step measuring device, etc., instead of using the depth profile of the particle concentration described above.

(10) Scratch resistance The film slit into a tape with a width of 1/2 inch is run on a guide pin (surface roughness: Ra 100 nm) using a tape running tester (running speed 1000 m.
/ Min, 10 passes, winding angle: 60 °, running tension:
20g). At this time, the scratches in the film were observed with a microscope, and it was judged that scratches with a width of 2.5 μm or more per tape width were excellent when less than 2 and good when 2 or more and less than 10 were good and bad when 10 or more. Good is desirable, but good is practically usable.

(11) Scraping resistance A film is slit into a tape shape with a width of 1/2 inch, a single blade is pressed vertically, and the product is run 0.5 cm further for 20 cm (running tension: 500 g, running speed: 6.
7 cm / sec). At this time, the height of the scraped material on the surface of the film attached to the tip of the single blade was read with a microscope and the scraped amount was taken (unit: μm). The amount of powder scraped on at least one side is 10μ
When it was less than m, the abrasion resistance was judged to be good, and when it exceeded 10 μm, the abrasion resistance was judged to be poor. The scraped amount: 10 μm is a critical point for determining whether or not the film surface is scraped during a working process such as a printing process or a calendering process, which causes a process or product performance trouble.

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

Examples 1 to 6, Comparative Examples 1 to 5 Crosslinked polystyrene particles having different average particle diameters as the inert particles A, silica particles derived from colloidal silica, and beaded silica as the inert particles B, reticulated titanium dioxide. Prepare ethylene glycol slurries containing each of them, and add the ethylene glycol slurries at 190 ° C to 1.
After heat-treating for 5 hours, it was transesterified with dimethyl terephthalate and then polycondensed to form polyethylene terephthalate (hereinafter abbreviated as PET) pellets containing 0.3 to 55% by weight of the particles. That is, the inert particles A and B were simultaneously added in the polymerization stage. A thermoplastic resin A is prepared using the pellets, and PET containing substantially no inert particles is produced by a conventional method.
And Each of these polymers was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours. The thermoplastic resin A is supplied to the extruder 1 and melted at 310 ° C., and the thermoplastic resin B is further added to the extruder 2
, Melted at 280 ℃, these polymers are merged and laminated in a merging block equipped with a rectangular laminated part, and they are wound around a casting drum with a surface temperature of 30 ° C using the electrostatic cast method to cool and solidify, An unstretched film having a two-layer structure was made. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the thermoplastic resin A layer. This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80 ° C. This stretching was carried out in four stages with the difference in peripheral speed between each pair of rolls. This uniaxially stretched film is stretched using a stenter.
Biaxially oriented laminate with total thickness of 15 μm, thermoplastic resin A layer thickness of 0.008 to 3 μm, stretched 4.0 times in width direction at 100 ° C. at 2000% / min and heat-treated at 200 ° C. for 5 seconds under constant length. I got a film. The parameters of the present invention for these films are the first
As shown in the table, when the parameter of the present invention is within the range, the scratch resistance and the abrasion resistance show good values as shown in Table 1, but if not, they have both characteristics. No film was obtained.

[Effects of the Invention] As described above, in the case of the biaxially oriented thermoplastic resin film of the present invention, the inert particles A contained in the laminated film layer allow the desired height of uniform and high density on the film surface. Inert particles B capable of forming protrusions and in a state of agglomerated particles
Since the protrusions and the film surface itself can be reinforced by the above, the scratch resistance and abrasion resistance of the film surface can be remarkably enhanced.

Further, the film of the present invention is a film produced by directly compounding and laminating by coextrusion in the film forming process without an operation such as coating, and compared with a laminated film made by coating during or after the film forming process. Since the molecules of the outermost layer are also biaxially oriented, not only the entire film but also the surface layer portion thereof have extremely high strength, which is advantageous in terms of cost and stability of quality.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B32B 27/08 8413-4F // B32B 27/20 Z 8413-4F B29K 105: 16 B29L 9:00 4F (56) Reference JP 60-63150 (JP, A) JP 60-63151 (JP, A) JP 49-98483 (JP, A) JP 50-123420 (JP, A) JP-A-60-254415 (JP, A) JP-A-62-95339 (JP, A) JP-B-58-5037 (JP, B2)

Claims (6)

[Claims] 1. A film containing a thermoplastic resin A and inert particles A, B as a main component is laminated by coextrusion on at least one side of a film containing a thermoplastic resin B as a main component to a thickness of 0.01 to 5 .mu.m. A biaxially oriented thermoplastic resin film, wherein the average particle size of the inert particles A is the thermoplastic resin A.
The thickness of the film layer is 0.1 to 10 times, and the inactive particles B are agglomerated particles in which a large number of primary particles having an average particle size smaller than the average particle size of the inactive particles A are arranged in a non-directional manner. A biaxially oriented thermoplastic resin film characterized in that 2. The biaxially oriented thermoplastic resin film according to claim 1, wherein the primary particles of the inert particles B have an average particle diameter of 5 to 100 nm. 3. The content of the inert particles B in the film layer of the thermoplastic resin A is 0.05 to 1% by weight.
The biaxially oriented thermoplastic resin film described. 4. The biaxially oriented thermoplastic resin film according to claim 1, which has an axial Young's modulus of 400 kg / mm ² or more. 5. The biaxially oriented thermoplastic resin film according to claim 1, wherein the particle concentration ratio of the inactive particles in the surface layer on the laminated film side containing the inactive particles A and B is 0.1 or less. 6. The biaxially oriented thermoplastic resin film according to claim 1, wherein the thermoplastic resin A is a crystalline resin.