JP3088426B2 - Laminated biaxially oriented film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laminated biaxially oriented film, and more particularly, to a film having uniform fine roughness and fine irregularities on the film surface, uniform surface roughness, slipperiness and resistance to slip. The present invention relates to a laminated biaxially oriented film having excellent abrasion resistance and scratch resistance and particularly useful as a base film for a magnetic recording medium.

[Prior Art] A thermoplastic biaxially oriented film represented by a polyethylene terephthalate film is used as a base film of a magnetic recording medium such as a magnetic tape and a floppy disk because of its excellent physical and chemical properties. .

In such a biaxially oriented film, for example, a polyester film, its slipperiness and abrasion resistance are major factors that determine the workability of the film manufacturing process and the working process in each application, and the quality of the product quality. I have. If these are insufficient, for example, a magnetic layer is applied to the polyester film surface, and when used as a magnetic tape, the friction between the coating roll and the film surface at the time of applying the magnetic layer is severe, and the film surface due to this is also severely worn, In extreme cases, wrinkles on the film surface, scratches, etc. occur.

Even after the film after applying the magnetic layer is slit and processed into audio, video or computer tape, it can be used with many guides, playback heads, etc., when drawing out or winding up from reels or cassettes. In particular, abrasion occurs remarkably during the process, and as a result of generation of abrasion and distortion, and precipitation of a white powdery substance due to abrasion of the surface of the polyester film, loss of a magnetic recording signal, that is, dropout is often a major cause.

Generally, in order to improve the slipperiness of a film, a method of reducing the contact area with a guide roll or the like by imparting a film surface unevenness is adopted. A method of depositing inert fine particles from the catalyst residue and a method of (ii) adding inert inorganic fine particles are used. Generally, the larger the size of the fine particles in the raw material polymer, the greater the improvement in the slipperiness.

On the other hand, in the case of a magnetic recording medium, particularly a high-density magnetic recording tape or a high-sensitivity floppy disk, the surface of the base film is required to be as flat as possible from the viewpoint of improving the electromagnetic conversion characteristics. However, when the film surface is flat, as described above, the film has poor slipperiness, and causes various troubles.

Therefore, there is a demand for a film for a magnetic recording medium to simultaneously satisfy these contradictory characteristics.

For the purpose of simultaneously satisfying such demands, one side is flat,
There has been proposed a method using a front and back different surface film having different surface roughness between the front and back such that the other surface is rough and smooth. When a magnetic layer is provided on the flat surface of the film, and the rough surface is a film running surface, it is possible to have both flatness in terms of improvement of electromagnetic conversion characteristics and slipperiness in terms of film running properties, A film in a better direction can be obtained as a film for a recording medium.

However, these means also have problems to be solved, and it is difficult to meet the demands for higher grade, higher density, etc. of the magnetic recording medium as it is.

The above-mentioned problem of the method of roughening using inert fine particles is considered to be mainly attributable to the fact that there are variations in the individual sizes of the fine particles and the distribution of the particle diameters. If the particle size distribution becomes large (wide), coarse protrusions based on large particles will be present on the film surface, which may cause shaving during processing, and may cause scratches during running as a magnetic tape after processing. , Dropouts increase due to generation of shavings, and electromagnetic conversion characteristics deteriorate.
Not desirable.

For this reason, it is important that the variation in the particle diameter is small, that is, the particle size distribution is small (narrow) in order to reduce the coarse projections. However, the smaller the particle size distribution, the smaller the number of large projections, which tends to make the slipperiness and running properties inadequate. Therefore, it is necessary to increase the amount of addition.
However, according to the research results of the present inventors, when the amount of added particles is increased, the particles are overlapped in the film thickness direction, so that the overlapping portion is likely to become a coarse projection even if the particle diameter of the particles is small. These coarse projections cause scraping during processing, as described above, and when magnetic tape is used, shavings and abrasions are generated due to friction with the pins during running, resulting in frequent occurrence of dropouts. Not so desirable. Further, the electromagnetic conversion characteristics are deteriorated due to the large protrusion, which is not desirable.

In recent years, plastic pins, such as polyacetal pins, have been used in many cases. However, plastic pins tend to have the above-mentioned problems more remarkably than metal pins, and further improvement is required.

[Object of the Invention] As a result of further research, the present inventor has found that in order to satisfy the required characteristics of a base film for a magnetic recording medium, in particular, the particle size distribution of inert particles contained in the film is small.
Further, they have found that it is important to prevent the particles from overlapping in the film thickness direction, and have reached the present invention.

Accordingly, an object of the present invention is to provide a film having a uniform surface roughness, uniform projections and fine irregularities on the surface, and excellent in slipperiness, abrasion resistance, and scratch resistance. It is an object of the present invention to provide a biaxially oriented film having a small increase in coefficient of friction after running, a small dropout, and excellent electromagnetic characteristics, particularly a laminated biaxially oriented film useful as a magnetic recording medium base film.

[Constitution / Effect of the Invention] An object of the present invention is to provide, according to the present invention, (I) at least one surface of a biaxially oriented film made of a thermoplastic polymer, (II) (A) an average particle size of 0.1 to 2 μm. (B) the particle size ratio (major axis / minor axis) of the particles is 1.0 to 1.2, and (c) the relative standard deviation represented by the following formula is 0.5 or less. Here, Di: area circle equivalent diameter of individual particles (μm): average value of area circle equivalent diameter (μm) n: represents the number of particles.

0.005% by weight of inert spherical particles excluding spherical silica particles
This is achieved by a laminated biaxially oriented film in which a biaxially oriented film composed of a thermoplastic polymer containing at least 0.4% by weight and having a film thickness of not more than 5 times the average particle size is laminated.

The film (I) in the present invention is a biaxially oriented film made of a thermoplastic polymer. As the thermoplastic polymer, a thermoplastic aromatic polyester is preferable. Further, as the polyester, a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component is preferable. Such polyesters are substantially linear and have film forming properties, especially film forming by melt molding. Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. Can be. Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol and the like.
Alicyclic diols such as 4-cyclohexanedimethanol can be mentioned. More specifically, those containing alkylene terephthalate and / or alkylene-2,6-naphthalate as a main component are preferred.

Among such polyesters, not only polyethylene terephthalate and polyethylene-2,6-naphthalate but also, for example, 80 mol% or more of all dicarboxylic acid components are terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and all glycol components are Is preferably a copolymer in which at least 80 mol% of ethylene glycol is ethylene glycol. At that time, not more than 20 mol% of the total acid component is terephthalic acid and / or 2,6-
The above-mentioned aromatic dicarboxylic acids other than naphthalenedicarboxylic acid can be used, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid; cyclohexane-1,4-
It may be an alicyclic dicarboxylic acid such as a dicarboxylic acid. In addition, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol. For example, aromatic diols such as hydroquinone, resorcinol and 2,2-bis (4-hydroxyphenyl) propane; Aliphatic diols having an aromatic ring such as 1,4-dihydroxymethylbenzene; and polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

In addition, the above-mentioned polyester contains components derived from oxycarboxylic acids such as aromatic oxyacids such as hydroxybenzoic acid; aliphatic oxyacids such as ω-hydroxycaproic acid, and the total amount of dicarboxylic acid components and oxycarboxylic acid components. And those which are copolymerized or bonded at 20 mol% or less with respect to the total amount.

Further, the polyester may be added in an amount in a range that is substantially linear, for example, in an amount of 2 mol% or less based on the total
Also included are those obtained by copolymerizing a polycarboxylic acid or polyhydroxy compound having a functionality higher than or equal to that of, for example, trimellitic acid, pentaerythritol and the like.

Such polyesters are known per se and can be produced in a manner known per se. As the above polyester, as a solution in o-chlorophenol
Those having an intrinsic viscosity of about 0.4 to 0.9 measured at 35 ° C are preferred.

The film (II) in the present invention is a biaxially oriented film made of a thermoplastic polymer containing inert spherical particles. The thermoplastic polymer may be the same as or different from the polymer forming the film (I), but the same is preferred. The more detailed description of the thermoplastic polymer can be applied to what has been described as the polymer forming the film (I).

The intrinsic viscosity of the film (II) may be the same as or different from that of the film (I). As an example of the embodiment of the laminated biaxially oriented film, in order to efficiently use the recovered material (such as a lug portion at the time of film formation), this is often used by mixing it with the film (I). In this case, the intrinsic viscosity of the film (I) is generally slightly lower than that of the film (II).

The inert spherical particles dispersed and contained in the film (II)
Average particle size is 0.1-2μm, particle size ratio (major axis / minor axis)
Are 1.0 to 1.2 (excluding spherical silica particles). The average particle size is preferably from 0.10 μm to less than 1.5 μm, more preferably from 0.15 μm to less than 0.8 μm, particularly preferably from 0.20 μm to 0.48 μm.
If the average particle size is less than 0.1 μm, the slipperiness becomes poor, the running property of the magnetic recording tape becomes poor, and the effect of improving the scratch resistance is insufficient. Further, the particle size ratio of the inert spherical particles is preferably 1.0
To 1.1, more preferably 1.0 to 1.05. If the particle size ratio is too large, the abrasion resistance deteriorates, which is not preferable.

Further, the inert spherical particles need to have a sharp particle size distribution, and the relative standard deviation representing the steepness of the distribution needs to be 0.5 or less.

 This relative standard deviation is expressed by the following equation.

Here, Di: area circle equivalent diameter of individual particles (μm): average value of area circle equivalent diameter (μm) n: represents the number of particles.

When an inert spherical particle having a relative standard deviation of 0.5 or less is used, since the particle is spherical and the particle size distribution is extremely steep, the height of the film surface projections becomes extremely uniform,
Even with the same number of projections, the slipperiness becomes extremely good as compared with the conventional one. In this sense, the relative standard deviation is 0.4
The following is preferable, 0.3 or less is more preferable, and 0.2 or less is especially preferable. If the relative standard deviation is too large, the abrasion resistance deteriorates, which is not preferable.

In the present invention, the content of the inert spherical particles is 0.005 to the thermoplastic polymer forming the film (II).
The content is at least 0.01% by weight and less than 0.4% by weight, preferably at least 0.01% by weight and less than 0.4% by weight, more preferably at least 0.02% by weight and less than 0.4% by weight, particularly preferably 0.05-0.3% by weight. If this amount is small, the effect of improving the slipperiness and winding property is insufficient, while if it is too large, the surface flatness is deteriorated, the electromagnetic conversion characteristics are reduced, and the particles tend to overlap in the thickness direction. Is not preferred.

The inert spherical particles are not particularly limited as long as the particles satisfy the above-mentioned requirements, but inorganic oxide spherical particles except spherical silica particles (eg, spherical titania particles, spherical zirconia particles, spherical alumina particles, spherical magnetite particles) And the like, and resin spherical particles (eg, spherical silicone resin particles, spherical crosslinked polystyrene particles, etc.). One or more of these can be used. Such spherical particles are not limited at all by the manufacturing method and others.

For example, the spherical silicone resin particles are represented by the following formula (A) RxSiO _{2-x / 2} ... (A) wherein R is a hydrocarbon group having 1 to 7 carbon atoms, and x is a number of 1 to 1.2. is there. ] It has the composition represented by these.

R in the above (A) is a hydrocarbon group having 1 to 7 carbon atoms, and is preferably, for example, an alkyl group having 1 to 7 carbon atoms, a phenyl group or a tolyl group. The alkyl group having 1 to 7 carbon atoms may be linear or branched, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-
-Butyl, tert-butyl, n-pentyl, n-heptyl and the like.

Among them, R is preferably methyl and phenyl, and particularly preferably methyl.

X in the above formula (A) is a number of 1 to 1.2. When x is 1 in the above formula (A), the above formula (A) is
The following formula (A) -1 RSiO _1.5 ... (A) -1 [where R has the same definition as above. ] Can be represented by

The composition of the above formula (A) -1 has the following structural part in the three-dimensional polymer chain structure of the silicone resin; It is derived from.

When x is 1.2 in the above formula (A), the above formula (A) is represented by the following formula (A) -2 R _1.2 SiO _1.4 ... (A) -2 [where R has the same definition as above. is there. ] Can be represented by

The composition of the above formula (A) -2 has the structure of the above formula (A) -1.
0.8 mol and the following formula (A) ′ R ₂ SiO... (A) ′ [wherein the definition of R is the same as above. ] Can be understood to consist of 0.2 mol.

The above formula (A) ′ is represented by the following structural part in a three-dimensional polymer chain of a silicone resin; Derived from

As understood from the above description, the composition of the above formula (A) of the present invention substantially consists of, for example, only the structure of the above formula (A) -1 or the structure of the above formula (A) -1. It can be seen that the structure of formula (A) -2 and the structure of the above formula (A) -2 coexist in a state of being randomly bonded at an appropriate ratio.

The spherical silicone resin particles preferably have a value of x in the range of 1 to 1.1 in the above formula (A). The silicone resin fine particles may have, for example, the following formula: RSi (OR ') ₃ [where R is a hydrocarbon group having 1 to 7 carbon atoms, and R' is a lower alkyl group. ] Or a partially hydrolyzed condensate thereof represented by the formula (1) by hydrolysis and condensation in the presence of ammonia or an amine such as methylamine, dimethylamine, ethylenediamine and the like with stirring. According to the above-mentioned method using the above-mentioned starting materials, silicone resin fine particles having a composition represented by the above formula (A) -1 can be produced.

In the above method, for example, the following formula R ₂ Si (OR ′) ₂ [wherein the definitions of R and R ′ are the same as above. According to the above method, the dialkoxysilane represented by the formula (A) -2 can be used together with the trialkoxysilane to produce silicone resin fine particles having the composition represented by the formula (A) -2.

Spherical crosslinked polystyrene particles include, for example, styrene derivative monomers such as styrene monomer, methylstyrene monomer, α-methylstyrene monomer, dichlorostyrene monomer, conjugated diene monomer such as butadiene, unsaturated nitrile monomer such as acrylonitrile, methyl Monomers such as methacrylates such as methacrylate, functional monomers such as unsaturated carboxylic acids, hydroxyl-containing monomers such as hydroxyethyl methacrylate, monomers having epoxide groups such as glycidyl methacrylate, unsaturated One or more monomers selected from sulfonic acids and the like, and a polyfunctional vinyl compound such as divinylbenzene or ethylene glycol dimethacrylate as a crosslinking agent for forming a three-dimensional structure of the polymer particles. Relate, trimethylolpropane triacrylate, and diallyl phthalate,
An emulsion of polymer particles is prepared by emulsion polymerization in an aqueous medium in which a water-soluble polymer is dissolved as a protective colloid, polymer particles are recovered from the emulsion, dried, and then crushed by a jet mill. And then classifying.

The spherical crosslinked polystyrene particles do not melt or melt during the polymerization of the thermoplastic polymer, and do not melt when the polymer is melted during the film forming.

In the present invention, in addition to the above-mentioned inert spherical particles, other inert particles can be contained within a range that does not impair the characteristics of the spherical particles. If the amount of the inert particles other than the inert spherical particles increases, the abrasion resistance deteriorates, which is not preferable. In this sense, the amount of other inert particles is preferably 4.
0 wt% or less, more preferably 2.5 wt% or less, particularly preferably 1.0 wt% or less.

Examples of such inert particles include silicon dioxide (including hydrates, diatomaceous earth, silica sand, and quartz); alumina; silicates containing 30% by weight or more of SiO ₂ (eg, amorphous or crystalline) Clay minerals, aluminosilicates (including calcined and hydrated products), hot asbestos, zircon, fly ash, etc.); oxides of Hg, Zn, Zr, and Ti; sulfates of Ca and Ba; Li, Ba, and Ca phosphates (including mono- and di-hydrogen salts); Li, Na, and K benzoates; C
a, Ba, Zn, and Mn terephthalates; Mg, Ca, Ba, Zn, Cd, P
titanates of b, Sr, Mn, Fe, Co, and Ni; chromates of Ba, and Pb; carbon (eg, carbon black, graphite, etc.); glass (eg, glass powder, glass beads, etc.); Illustrative are carbonates of Mg; fluorite; and ZnS.

The timing at which the inert spherical particles or other inert particles are contained in the thermoplastic polymer may be any stage before the melt extrusion step.For example, before the polymerization of the polymer, during the polymerization, after the polymerization Either may be used. Also, it may be during the preparation step for melt extrusion. Examples of this include direct addition or kneading immediately before melting.

The laminated biaxially oriented film of the present invention has a laminated structure of two or more layers, and at least one of the outermost layers is made of the thermoplastic polymer containing the inert spherical particles. Preferably it has a three-layer structure, both outermost layers consisting of a polymer. The other film layers constituting the laminated biaxially oriented film may or may not contain inert spherical particles, other inert particles, and the like. However, when the inert particles are contained, the inert spherical particles (and other inert particles) contained in the other film layer are replaced with the inert spherical particles (and other inert particles) contained in the film layer forming the surface. (Inert particles), but preferably at the same level. Also, the content of inert spherical particles is preferably small or the same. Particles other than the inert spherical particles may not be contained in the outermost layer or may be contained to such an extent that the characteristics of the inert spherical particles are not impaired.

In the laminated biaxially oriented film, the film (II) containing the inert spherical particles forming the surface must have a thickness not more than 5 times the average particle diameter of the inert spherical particles, and preferably 4 times. Or less, more preferably 3 times
Less than twice. If the film (II) containing the inert spherical particles forming the surface is too thick, the overlapping of the inert spherical particles will occur and coarse projections will be formed, which is not preferable. On the other hand, if the film layer is too thin It is not preferable because the surface becomes flat, the winding property and the scratch resistance deteriorate, and the fixing force of the spherical particles decreases. Therefore, the thickness of the film layer is preferably at least 1/2 times the average particle size.

In the present invention, as can be seen from the fact that the thickness of the layer of the film (II) containing inert spherical particles is preferably 5 times or less, more preferably 1/2 times or more the average particle size of the inert spherical particles.
The average particle size of the inert spherical particles is at a level close to 0.1 to 2 μm, and is characterized in that the thickness of the film (II) layer is small.

The laminated biaxially oriented film of the present invention can be obtained by a conventionally known method or a method accumulated in the art. For example, it can be obtained by first producing a laminated film and then biaxially orienting the film.
This laminated film can be manufactured by a conventionally accumulated method for manufacturing a laminated film. For example, a method of laminating a film layer forming a surface and a film layer forming a core layer in a molten state or a state of being cooled and solidified can be used. More specifically, for example, co-extrusion,
It can be manufactured by a method such as extrusion lamination.

The film laminated by the above-mentioned method can be made into a biaxially oriented film by further following the conventional method for producing a biaxially oriented film.

For example, it is manufactured by stretching an amorphous unstretched film that has been melted and laminated by the above-described method in a biaxial direction, heat-setting, and if necessary, performing a relaxation heat treatment. At this time, since the film surface characteristics vary depending on the particle size and amount of the inert spherical particles and the stretching conditions, they are appropriately selected from conventional stretching conditions. Further, since the density, the heat shrinkage, and the like also change depending on the temperature, magnification, speed, and the like during stretching and heat treatment, conditions that simultaneously satisfy these characteristics are determined. For example, in the case of polyethylene terephthalate, the first-stage stretching temperature (for example, the longitudinal stretching temperature: T ₁ ) is (Tg−10) to (Tg + 4).
5) From the range of ° C (Tg: glass transition temperature of polymer), the second-stage stretching temperature (for example, the transverse stretching temperature: T ₂ ) is (T
_It is preferable to select from the range of ₁ +5) to (T ₁ +40) ° C. Further, after the first and second stages of stretching, the third and fourth stages of stretching may be performed again in the vertical or horizontal direction. The stretching ratio may be selected from a range where the stretching ratio in the uniaxial direction is 2.5 times or more, particularly 3 times or more, and the area magnification is 8 times or more, particularly 10 times or more. Furthermore, the heat setting temperature is 18
The temperature is preferably selected from the range of 0 to 250 ° C, more preferably 200 to 230 ° C. The thickness of the film is preferably 1 to 100 μm. More preferably from 5 to 80 μm, particularly preferably from 7 to 25 μm
It is.

In the laminated biaxially oriented film, the film (II) layer containing the inert spherical particles forming the surface has a thickness of 10 μm or less, preferably 4 μm or less, more preferably 2.4 μm or less. It is particularly preferably 1.44 μm or less, and the lower limit of the thickness of the film layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, and still more preferably 0.25 μm or more.
μm, particularly preferably more than 0.6 μm.

The laminated biaxially oriented film of the present invention has, as compared with the conventional one, extremely good slipperiness even though the film surface is flat, and also has excellent abrasion resistance and excellent scratch resistance. Have. Further, it has a feature that the above characteristics are good not only for metal pins but also for plastic pins.

The reason for this is not clear, but the use of fine spherical particles that are extremely spherical and nearly monodisperse makes the shape of each projection on the film surface sharp, and a film containing spherical particles that form the surface. Due to the thin layer, the spherical particles are prevented from overlapping in the thickness direction, and the protrusion heights on the film surface are uniform.As a result, the coefficient of friction is low despite the good surface flatness of the film surface, and In addition, it is presumed that the contact with other objects is more uniform and supported by many protrusions, so that the durability is excellent, and it is hard to be scraped and hard to scratch.

The laminated biaxially oriented film of the present invention is useful as a base film of a magnetic recording medium, particularly a high-density magnetic recording medium, by utilizing such features. In particular, when used as a base film for high-density video tapes such as those for super high grade and 8 mil video, high-density floppy disks, and magnetic tapes for high-density computers, excellent electromagnetic conversion characteristics, slipperiness, running properties, Scratch resistance, scratch resistance, etc. are obtained.

The production of a magnetic recording medium using a laminated biaxially oriented film as a base film can be performed by a conventionally known method. For example, the magnetic layer is usually made of a polymer binder containing a ferromagnetic powder such as γ-iron oxide, Co-containing iron oxide, chromium oxide, iron powder, and the like, such as a vinyl chloride-vinyl acetate copolymer and a vinyl chloride-vinyl acetate-vinyl alcohol. Copolymer, polyvinyl butyral, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butyl acrylate-2
Vinyl resins such as -hydroxyethyl methacrylate copolymer, rubber resins such as acrylonitrile-butadiene copolymer, cellulose resins such as nitrocellulose and acetylcellulose, and crosslinkable resins such as epoxy, phenoxy and urethane. To this, if desired, a lubricating material, a light-blocking agent, a dispersant, an antistatic agent and the like may be added. The coating type magnetic layer is formed by applying a magnetic paint. Further, a metal thin film type magnetic layer can be provided.

EXAMPLES Hereinafter, the present invention will be further described with reference to examples. In addition,
Various physical properties and characteristics in the present invention were measured as follows.

(1) Particle Size of Spherical Particle The particle diameter is measured in the following states.

 1) When the average particle size, the particle size ratio, and the like are determined from the powder.

2) To find the average particle size, particle size ratio, etc. of the particles in the film.

1) From powder: Particle particles are scattered on an electron microscope sample stand so that individual particles do not overlap as much as possible, and a gold thin film deposition layer is formed on this surface with a thickness of 200 to 300 mm by a gold sputtering apparatus.
Observation is performed at a magnification of 10,000 to 30,000 with a scanning electron microscope, and the major axis (Dli), minor axis (Dsi), and area circle equivalent diameter (Di) of at least 100 particles are obtained with Luzex 500 manufactured by Nippon Regulator. The major axis (Dl), minor axis (Ds), and average particle size () of the inert spherical particles are represented by the number average values represented by the following equations.

2) In the case of particles in the film: A small piece of the sample film is fixed on a sample stage for a scanning electron microscope, and a sputtering device (JFC-1100 type ion sputtering device manufactured by JEOL) is used on the film surface under the following conditions. An ion etching process is performed. The conditions are as follows: a sample is placed in a bell jar, the degree of vacuum is raised to a vacuum of about 10 ⁻³ Torr, and ion etching is performed at a voltage of 0.25 KV and a current of 12.5 mA for about 10 minutes. Further, the film surface was subjected to gold sputtering with the same apparatus, and a scanning electron microscope was used to 10,000-300
Observed at 00x, Luzex 500 manufactured by Nippon Regulator
The major axis (Dli) and minor axis (Ds) of at least 100 particles at
i) and the equivalent circle diameter (Di) are determined. Hereinafter, the above 1)
Perform in the same manner as described above.

(2) Relative standard deviation of spherical particles The area equivalent circle diameter (Di) obtained in the section (1) and its average value () are used, and are obtained from the equation described in the text.

(3) Average particle size, particle size ratio, etc. of particles other than spherical particles 1) Average particle size CP-50 Centrifugal Particle Size Analyzer manufactured by Shimadzu Corporation (Centrifugal Particle Siz)
e Analyser). The particle size corresponding to 50% by mass was read from the integrated curve of the particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, and this value was set as the above average particle size (Book Diameter measurement technology, published by Nikkan Kogyo Shimbun, 1975, pp. 242 to 247).

2) Particle size ratio A small piece of film is fixedly formed with epoxy resin, and an ultra-thin section (cut in parallel to the film flow direction) with a thickness of about 600 mm is created with a microtome. The cross-sectional shape of the lubricant (particles) in the film of this sample is observed with a transmission electron microscope (H-800, manufactured by Hitachi, Ltd.), and expressed as a ratio of the major axis to the minor axis of the lubricant.

3) Relative standard deviation Determined by the following formula.

Here, each particle diameter (μm) obtained in Di; 1) item; average diameter (μm) obtained in 1) item; n; the number of divisions (μ) when the integration curve in 1) item is obtained.
m) φi; represents the existence probability (mass percent) of particles of each particle size.

(4) Film surface roughness (Ra) This is a value defined by JIS-B0601 as the center line average roughness (Ra). In the present invention, a stylus type surface roughness meter (SURFCORDER) manufactured by Kosaka Laboratory Co., Ltd. (SE-30C). The measurement conditions and the like are as follows.

(A) Probe tip radius: 2 μm (b) Measurement pressure: 30 mg (c) Cut-off: 0.25 mm (d) Measurement length: 2.5 mm (e) How to summarize the data: Measure the same sample 5 times and repeat Except for one large value, 4 decimal places of the average of the remaining 4 data
Round the digits to the third decimal place.

(5) Film surface roughness PV1 / 1 Using a stylus-type surface roughness meter, enlarge the reference length direction by 50 times and increase the surface roughness direction by 50,000 times to draw a chart. From the straight line parallel to the average line of the portion extracted by 1.0 mm, select the straight line that passes through the first peak from the highest and the bottom of the first valley from the deep, and the value obtained by dividing the interval between these two straight lines by the vertical magnification Is expressed in microns, and this PV value
Expressed as the average value of 10 samples.

(6) Coefficient of friction of film (μk) Measured as follows using the apparatus shown in the figure.
In the figure, 1 is an unwinding reel, 2 is a tension control, 3, 5, 6, 8, 9 and 11 are free rollers, 4 is a tension detector (entrance), 7 is a stainless steel SUS304 fixing rod (outer diameter). 5 mmφ, roughness 0.3S) or a plastic fixing rod made of polyacetal (outer diameter 5mmφ, roughness 0.1S), 10 is a tension detector (outlet), 12 is a guide roll, and 13 is a take-up reel.

A magnetic tape cut to a width of 1/2 inch in an environment of a temperature of 20 ° C and a humidity of 60% is fixed on a fixing rod (surface roughness: 0.3 μm) at an angle θ = (152/180) π radian (152 °). Move (friction) at a speed of 200 cm per minute by contact. When the tension controller 2 is adjusted so that the entrance tension T ₁ is 40 g, the film is 90 m in tension at the exit (T ₂ : g).
After traveling, it is detected by an exit tension detector, and a traveling wear coefficient μk is calculated by the following equation.

μk = (2.303 / π) log (T 2 / T 1) = 0.868 log (T 2/40) if this was repeated running, and the running friction coefficient .mu.k after repeated.

(7) Electromagnetic conversion characteristics of magnetic coating tape A 50% white level signal (100% white level signal has a peak: two: peak voltage is 0.714 volts) and a 100% chroma level signal using a commercial household VTR Is recorded, and the reproduced signal is measured using a Shibasoku noise meter: type 925R. The definition of chroma S / N is as follows according to the definition of Shibasoku.

Here, ES (pp) is a peak-to-peak voltage difference (pp) of the reproduced signal of the white level signal.

ES (pp) = 0.714V (pp) EN (rms) is the square root value of the peak voltage of the reproduced signal of the chroma level signal.

(8) Dropout A commercially available dropout counter (eg, Shibasoku VH)
(01BZ type) and count the dropout of 4μsec × 10dB, and calculate the count number per minute.

Example 1 Dimethyl terephthalate and ethylene glycol were
Manganese acetate is used as a transesterification catalyst, antimony trioxide is used as a polymerization catalyst, and phosphorous acid is used as a stabilizer.
5 ° C.) to obtain a polyethylene terephthalate of 0.62 [hereinafter referred to as polyester I].

On the other hand, 0.2% by weight of spherical silicone resin particles having an average particle diameter of 0.8 μm, a particle diameter ratio of 1.04, and a relative standard deviation of 0.19 as a lubricant.
Polyethylene terephthalate having an intrinsic viscosity of 0.61 was obtained in the same manner as for polyester I, except that it was added and polymerized [hereinafter referred to as polyester II].

The above polyester I and polyester II are each 170 ° C.
After drying for 3 hours, the mixture is fed to separate extruders of a co-extrusion film forming machine, and polyester I forms a film I layer, and polyester II forms a film II layer. Film II: Film I: Film II is 2: 10: 2
Then, an unstretched film was obtained by co-extrusion from a three-layer die.

This unstretched film is preheated by a longitudinal stretching preheating roll and an IR heater, stretched in the longitudinal direction at a stretching temperature of 91 ° C. and a stretching ratio of 3.7, and then stretched in a transverse direction at a stretching temperature of 105 ° C. and a stretching ratio of 3.9. Further, the film was heat-treated at 210 ° C., and the thickness of a three-layered laminate having a film I layer made of polyester I as a core layer and a film II layer made of polyester II on both surface layers was obtained.
A μm biaxially oriented film was obtained.

 Table 1 shows the characteristics of this film.

Further, on this film, 100 parts by weight of iron oxide powder having the following composition Co: Essrec A (vinyl chloride-vinyl acetate copolymer manufactured by Sekisui Chemical Co., Ltd.) 10 Nipporan 2304 (polyurethane elastomer manufactured by Nippon Polyurethane) 5 〃 lecithin 1 メ チ ル methyl ethyl ketone 75 メ チ ル methyl isobutyl ketone 75 〃 toluene 75 添加 Additive (lubricant, silicone resin) 0.15 磁性 magnetic paint is applied by gravure roll and the magnetic paint layer is smoothed by doctor knife Then, the magnetic paint is magnetically oriented by a conventional method while it is still dry, then guided to an oven, dried and cured, further calendered to make the coating surface uniform, slit, and a magnetic layer having a thickness of about 4 μm. A magnetic tape having a width of 1/2 inch was formed. Table 1 shows the characteristics of this film and magnetic tape.
It is shown in FIG.

From this table, it can be seen that the film thus obtained has the same protrusion height on the surface, no coarse protrusions, and thus has good electromagnetic conversion characteristics when used as a magnetic tape, and has good runnability with metal pins. Not only is good, but also the running property with the plastic pin is good, and the increase in μk after 200-pass repetitive running is small and the shaving property is good. Further, it can be seen that the number of dropouts after 200 passes is relatively small and good.

Comparative Example 1 A film and a tape were prepared in the same manner as in Example 1, except that the inert particles contained in the polyester II were changed as shown in Table 1. As shown in Table 1, those having a large particle diameter ratio and a large relative standard deviation showed a large increase in μk and a large dropout in the plastic pin.

[Brief description of the drawings]

The figure shows the coefficient of friction (μk) for evaluating film runnability.
FIG. 1: payout reel, 2: tension controller, 3, 5, 6,
8, 9, 11: Freeroll, 4: Tension detector (entrance),
7: fixed pin, 10: tension detector (outlet), 12: guide roll, 13: take-up reel

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-77431 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 G11B 5 / 73-5/738

Claims (4)

(57) [Claims] 1. A biaxially oriented film made of a thermoplastic polymer (I) having at least one surface having (II) (A) an average particle size of 0.1 to 2 μm, and (B) a particle size ratio of particles (major axis / minor axis). ) Is 1.0 to 1.2, and (c) the relative standard deviation represented by the following formula is 0.5 or less. Here, Di: area circle equivalent diameter of individual particles (μm): average value of area circle equivalent diameter (μm) n: represents the number of particles. A thermoplastic polymer containing at least 0.005% by weight and less than 0.4% by weight of inert spherical particles excluding spherical silica particles;
A laminated biaxially oriented film in which a biaxially oriented film having a film thickness of not more than 5 times the average particle size is laminated. 2. The laminated biaxially oriented film according to claim 1, wherein the thermoplastic polymer is a polyester. 3. The laminated biaxially oriented film according to claim 1, wherein the inert spherical particles are at least one selected from spherical silicone resin particles and spherical crosslinked polystyrene particles. 4. The laminated biaxially oriented film according to claim 1, wherein the laminated biaxially oriented film is a base film of a magnetic recording medium.