JPH01299832A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented polyester film having uniform and regular surface roughness and excellent lubricity and chipping resistance, by forming said film from a mixture of an aromatic polyester with specified porous hollow organic particles. CONSTITUTION:A biaxially oriented polyester film formed from a mixture of an aromatic polyester (i) with 0.001-5wt.% (based on the aromatic polyester) porous hollow organic particles (ii) having a particle diameter (a) as defined as a ratio to the minimum diameter of 1.0-1.2, a mean hollow rate (b) of the formula of 0.001-0.95, a mean particle diameter (c) of 0.1-5mum and a specific surface area (d) as determined by the BET method >=20m<2>/g. In the formula, Dxi is the equivalent diameter (mum) of an equal surface circle for the inside diameter of an individual particle, Di is the equivalent diameter (mum) of an equal surface circle for the outside diameter of an individual particle, and n is the number of particles. Said porous hollow organic particle is a hollow sphere having a hollow which communicates with its outside through 10-500Angstrom (on the average) pores formed in the shell.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a biaxially oriented polyester film, and more specifically, the present invention relates to a biaxially oriented polyester film having a specific surface area (BET method) of 2 as an effective lubricant component.
The present invention relates to a biaxially oriented polyester film containing porous hollow organic particles of 0rIt/g or more, which is flat and has excellent abrasion resistance.

<Prior Art> Polyester, represented by polyethylene terephthalate, is used for magnetic tapes, photographs, and capacitors because of its excellent physical and chemical properties.

Widely used as packaging film.

The slipperiness and abrasion resistance of these films are major factors that determine the workability of the film manufacturing process and the processing process in each application, as well as the quality of the product. In particular, when applying a magnetic layer to the surface of a polyester film, the friction and abrasion between the coating roll and the film surface are extremely severe, and scratches and scratches are likely to occur on the film surface. Furthermore, even after slitting a film coated with a magnetic layer and processing it into audio, video, or computer tape, there are many guide parts, playback heads, etc. when pulling it out from a reel or cassette, winding it, or other operations. Significant abrasion occurs between the layers, causing scratches, distortion, and the precipitation of white powdery substances due to scratches on the surface of the polyester film, which is a major cause of missing magnetic recording signals, that is, dropouts. There are many things.

□ In general, to improve the slipperiness and abrasion resistance of films, a method is adopted in which the surface of the film is provided with unevenness to reduce the contact area with guide rolls, etc. These methods can be broadly classified into (i) film raw materials; (ii) A method in which inert fine particles are precipitated from the catalyst residue in the polyester used for the reaction, and (ii) a method in which inert inorganic fine particles are added to the polyester are used. Generally speaking, the larger the size of the fine particles in these raw polyesters, the greater the effect of improving slipperiness. Since the film itself can cause defects such as dropouts, the unevenness on the film surface must be as fine as possible, and the current situation is that there are demands to satisfy contradictory characteristics at the same time.

Conventionally, as a method of improving the slipperiness of a film, a method of adding inorganic particles such as silicon oxide, titanium dioxide, calcium carbonate, talc, clay, calcined kaolin, etc. to polyester, which is a film substrate (for example, Japanese Patent Application Laid-Open No. 54-57
562) or a method has been proposed in which fine particles containing calcium, lithium or phosphorus are precipitated in the polymerization system for producing polyester (Japanese Patent Publication No. 52-3).
(See Publication No. 2914). When formed into a film, the fine particles that are inert to polyester form protrusions on the surface of the film, and these protrusions improve the slipperiness of the film.

However, the method of improving the slipperiness of a film by using protrusions made of fine particles has an essential problem in that the protrusions impair the flatness of the film surface.

In an attempt to resolve these contradictory issues of flatness and slipperiness, a method has been proposed that utilizes a composite particle system of relatively large particles and relatively small particles.

U.S. Patent No. 3,821,156 specifies 0.5 to 30
A combination of 0.02-0.1% by weight of micron calcium carbonate particles and 0.01-0.5% by weight of 0.01-1.0 micron silica or hydrated alumina silicate is disclosed.

U.S. Pat. No. 3,884,870 is approximately 0.5 to 30
Inert fine particles such as calcium carbonate, calcined aluminum silicate, hydrated aluminum silicate, magnesium silicate, calcium silicate, calcium phosphate, silica, alumina, barium sulfate, mica, diatom, etc. with a micrometer of approximately 0.0
02 to 0.018 heavy ol% and about o, oi to about 1.0 μm
silica, calcium carbonate, calcined calcium silicate, hydrated calcium silicate, calcium phosphate, alumina, barium sulfate, magnesium sulfate, diatomaceous, etc. in combination with about 0.3 to 2.5% by weight of inert fine particles. ing.

U.S. Patent No. 3,980,611 specifies particle size i, oμ
Calcium phosphate fine particles of three particle size grades of less than m, 1 to 2.5 μm, and more than 2.5 μm are combined to form a
It discloses adding i5000 ppm or less to polyester.

Japanese Patent Publication No. 55-41648 (Japanese Patent Publication No. 53-7115)
No. 4) is a fine particle of 0.22 to 2.5 μm in diameter.
1.0% by weight and 0.003 to 1.8 to 10 μm fine particles
0.25% by weight, and the microparticles are proposed to be oxides or inorganic salts of elements of groups Ⅰ, ② and IV of the periodic table.

Japanese Patent Publication No. 55-40929 (Japanese Patent Publication No. 52-1190)
No. 8) contains inert inorganic fine particles of 3 to 6 μm from 0.01 to
0.08% by weight and 0 inert inorganic fine particles of 1-2.5 μm
．． 08 to 0.3% by weight, the total amount of these fine particles with different particle sizes is 0.1 to 0.4% by weight, and the ratio of large particle size to small particle size particles is Discloses mixed particles that are between 0.1 and 0.7.

JP-A No. 52-78953 has a length of 10 to 1,000 m.
, cz m of inert particles 0.01-0.5% by weight.
5-15 μm calcium carbonate 0.11-0.5% by weight
Discloses a biaxially oriented polyester film containing. Japanese Patent Application Laid-Open No. 52-78953 discloses that 10 to 1,0
Various inorganic substances other than calcium carbonate are listed in the general description as inert particles of 00 mμ. However, this publication merely discloses a specific example in which silica or clay, which is usually available as fine particles of 10 to 1000 mμ, is used as the inorganic substance.

In addition, in a film made of polyester containing the above-mentioned inert fine particles, peeling occurs at the boundary between the fine particles and the polyester due to biaxial stretching, and voids are formed around the fine particles. The larger the particle is, the larger the void is.
The shape is more spherical than plate-like, and the fine particles are single particles that are less likely to deform, and the larger the stretching area ratio when stretching an unstretched film, and the lower the temperature. As these voids get larger, the shape of the protrusions becomes gentler, increasing the wear coefficient, and small scratches on the voids of the biaxially oriented polyester film that occur during repeated use also cause particles to fall off. This reduces durability and causes the generation of shavings. It has traditionally been common practice to add calcium carbonate, titanium oxide, kaolin, etc. as inert fine particles, but these fine particles form large voids, causing the above-mentioned problem, and improvements to this problem are also desired. ing.

<Purpose of the Invention> The present inventor has solved these disadvantages, and has improved the slipperiness and abrasion resistance of the film by reducing the voids around the inert fine particles and making the film surface moderately rough, and which is suitable for various uses. The present invention was developed as a result of intensive studies to obtain a biaxially oriented polyester film with suitable surface properties.

Accordingly, an object of the present invention is to provide a biaxially oriented polyester film with small voids, uniform film surface roughness, uniform surface irregularities, and excellent slipperiness and abrasion resistance.

<Configuration/Effects of the Invention> According to the present invention, the above objects and advantages of the present invention are achieved by: (1) aromatic polyester; and (2) (a) defined by the ratio of the maximum diameter to the minimum diameter; (b) the average hollowness ratio expressed by the following formula (A) is o, o
oi ~ 0.95, Σ (Dxi/Di )3/n - (A)i=1 where Dxi is the area circular diameter (μ
m), Di is the area circle equivalent diameter of the outer diameter of each particle (μm), n is the number of particles, (C) the average particle size is o, oi ~ 5 μm, and (d
) This is achieved by a biaxially oriented polyester film consisting of a mixture of porous hollow organic particles o, ooi ~5% by weight (based on the aromatic polyester) having a specific surface area of 20 sides/g or more by the BET method.

Here, the maximum diameter and minimum diameter of the porous hollow organic particles.

The area circular phase light diameter is determined from an image magnified, for example, 10,000 to 30,000 times with a scanning electron microscope after depositing a gold thin film layer on the particle surface, and the ratio of two average particle diameters is determined by the following formula.

Average particle size = Area of measured particles Sum of circular phase light diameters / Number of measured particles Particle size ratio = Average maximum diameter of measured particles / Average minimum diameter of the particles Furthermore, the area circle of the inner diameter and outer diameter of the porous hollow organic particles As shown in FIG. 1, the phase light diameter is determined from an image magnified, for example, 10,000 to 30,000 times using a transmission electron microscope after preparing ultrathin sections of the particles using a microtome, as shown in FIG.

The aromatic polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such aromatic polyesters are substantially linear and have film forming properties, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarbonyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, and diphenyl ketone dicarboxylic acid.

Examples include anthracene dicarboxylic acid. Examples of aliphatic glycols include ethylene glycol,
trimethylene glycol, tetramethylene glycol,
Pentamethylene glycol.

Examples include fullylene glycols having 2 to 10 carbon atoms such as hexamethylene glycol and decamethylene glycol, and alicyclic diols such as cyclohexane dimetatool.

In the present invention, as the aromatic polyester, for example, one containing alkylene terephthalate and/or alkylene naphthalate as a main component is preferably used.

Among such aromatic polyesters, for example, polyethylene terephthalate, polyethylene-2.

In addition to 6-naphthalate, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and/or 2-naphthalate.
, 6-naphthalene dicarboxylic acid, and a copolymer in which 80 mol% or more of the total glycol component is ethylene glycol is preferred. At that time, 20 mol% or less of the total acid component is terephthalic acid and/or 2.

Can be the above-mentioned aromatic dicarboxylic acids other than 6-naphthalene dicarboxylic acid, and also aliphatic dicarboxylic acids such as adipic acid, cepatic acid, etc.; cyclohexane-1
, 4-dicarboxylic acid, and the like. In addition, up to 20 mol% of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or aromatic diols such as hydroquinone, resorcinol, 2,2-bis(4-hydroxyphenyl)propane, etc. Aliphatic diols having an aromatic ring such as 4-dihydroxymethylbenzene; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. can also be used.

In addition, the aromatic polyester used in the present invention includes a dicarboxylic acid component and a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid; an aliphatic oxyacid such as ω-hydroxycaproic acid; It also includes those copolymerized or bonded in an amount of 20 mol % or less based on the total amount of carboxylic acid components.

Generally, the aromatic polyester in the present invention contains a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound, such as a trimellitic acid, in a substantially linear amount, for example, 2 mol % or less based on the total acid component. Copolymers of acids, pentaerythritol, etc. are also included.

The above polyester is known per se, and can be produced by a method known per se.

The above-mentioned polyester has an intrinsic viscosity of about 0.001 as measured as a solution in O-chlorophenol at 35°C.
4 to about 0.9 is preferred.

The biaxially oriented polyester film of the present invention has many fine protrusions on its surface.

According to the present invention, these large numbers of fine protrusions originate from a large number of porous hollow organic particles dispersed and contained in the polynisder.

Aromatic polyesters containing dispersed porous hollow organic particles are usually used at any time during the reaction to form polyesters, such as during the transesterification reaction or polycondensation reaction when using the transesterification method, or at any time during the polycondensation reaction when using the direct polymerization method. It can be prepared by adding porous hollow organic particles (preferably as a slurry in glycol) into the reaction system at any time. Preferably, at the beginning of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3,
Preferably, porous hollow organic particles are added to the reaction system.

In the present invention, the porous hollow particles include (i) a shape close to a true sphere, (ii) a hollow sphere having pores in the shell wall, (ii)
It is characterized by six properties: ) small particle size, Ov) narrow particle size distribution, (■) large specific surface area and (Vi) good affinity with polyester.

That is, the porous hollow organic particles in the present invention have a particle size ratio defined by the ratio of maximum diameter to minimum diameter in the range of 1.0 to 1.2. A preferred particle size ratio is in the range of 1.0 to 1.15, and a more preferable particle size ratio is in the range of 1.0 to 1.12.

Furthermore, the porous hollow organic particles have an average hollowness ratio expressed by the following formula (A) in the range of 0.001 to 0.95. A preferable average hollowness ratio is in the range of o, ooi to 0.51,
A more preferable average hollowness ratio is in the range of 0.001 to 0.13.

Σ (Dxi/Di)3/n ・=(A)i・1 Here, Dxi is the equivalent diameter within the area of the inner diameter of each particle (μ
m), Di is the area equivalent diameter of the outer diameter of each particle (μm), n is the number of particles, if this average hollowness ratio is less than o, ooi, the effect of the particles being hollow and porous will not appear; If it exceeds 0.95, the thickness of the shell wall will be insufficient and particles will break during film formation, which is not preferable.

This hollow particle was used as a slit to obtain a thin piece, and FIG. 1 schematically shows the thin piece. In Figure 1, 1 is the shell wall, 2 is the pore, 3 is the internal cavity, 4 is the inner diameter (DXi),
5 is the outer diameter (Di).

The average particle size of the porous hollow organic particles is o, oi ~ 5 μm
1 preferably 0.05 to 2 μm. If the average particle size is less than 0.01 μm, the effect of improving slipperiness and abrasion resistance is insufficient, which is not preferable. In addition, the average particle size is 5 μm
If it exceeds , the surface of the film becomes too rough, which is not preferable.

In addition, it is preferable that the porous hollow organic particles have a sharp particle size distribution, and the relative standard deviation representing the steepness of the distribution is 0.
．． It is preferably 5 or less, more preferably 0.3 or less, particularly 0.12 or less.

This relative standard deviation is expressed by the following formula (B).

Relative standard deviation = Here, Di is the area circular phase diameter (μm) of each particle, b is the average value of the area circular phase light diameter (μm), (=Σ　Di/n) i=1 n is the measured number of particles It is.

When porous hollow organic particles with a relative standard deviation of 0.5 or less are used, the height of the protrusions on the film surface becomes extremely uniform because the particles are spherical and have an extremely steep particle size distribution.

The porous hollow organic particles in the present invention are hollow spheres with a cavity inside, and the cavity inside the sphere and the outside of the sphere are connected by an average of 10 to 500 pores formed in the shell wall. .

Furthermore, the thickness of the shell wall can be arbitrarily selected depending on the required characteristics.

The porous hollow organic particles in the present invention are minute as described above and have pores in the shell wall that communicate with the internal cavities, so the specific surface area is 20TIi/g by the BET method.
It's bigger than that. Therefore, it is thought that the particle surface is extremely active and the adhesion with polyester is further improved, and various surface treatments can also be performed. Furthermore, by filling the internal cavities of the porous organic particles in advance with glycol and subjecting them to polycondensation of aromatic polyester, the aromatic polyester in the internal cavities of the hollow organic particles and the aromatic compounds surrounding the outside of the particles are combined. It is also possible that the polyester is bonded through the pores of the shell wall to further improve the adhesion with the polyester.

The porous hollow organic particles are not limited in any way in terms of their production method or other aspects, as long as the above-mentioned conditions are satisfied.

For example, porous hollow organic particles can be produced by in-situ polymerization or by making a W10/W type double emulsion with a monomer and a surfactant, and then drying it after polymerization to handle the water contained in the porous hollow organic particles. It can be prepared by a double emulsion method.

To explain further, unsaturated nonionic monomers such as (meth)acrylic acid esters (e.g. methyl methacrylate, butyl acrylate, etc.), unsaturated dicarboxylic acid esters such as maleic acid dialkyl esters, unsaturated monomers such as styrene, etc. Vinyl compounds, unsaturated nitrites such as acrylonitrile, functional septamers such as unsaturated carboxylic acids, hydroxyl-containing monomers such as hydroxyethyl methacrylate, and epoxide group-containing monomers such as glycidyl methacrylate.

One or more monomers selected from unsaturated sulfonic acids, etc., and a polyfunctional vinyl compound such as divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropanetria as a crosslinking agent to give the polymer particles a three-dimensional structure. Crate, diallyl phthalate, etc. are polymerized to form a W10/W type double emulsion using a surfactant, the polymer particles are collected and dried, and then crushed into individual particles using a jet mill. and then classification.

Furthermore, the porous hollow organic particles in the present invention include, for example, epoxy resin, phenol resin, melamine resin, maleimide resin, and benzoguanamine resin.

It may be formed from a resin such as formaldehyde resin.

The porous hollow organic particles in the present invention do not dissolve or melt during the polymerization of polyester, and do not melt when the polymer is melted during film forming, but there is no problem if they are deformed.

Although the biaxially oriented polyester film of the present invention has extremely small voids compared to conventional films,
The reason why these voids are small is that the porous hollow organic particles have a good affinity for aromatic polyester, and because the particles themselves are extremely close to true spheres, the stress around the particles propagates evenly during stretching, and the aromatic polyester Stress does not concentrate on a part of the interface between the polyester and the lubricant, and in some cases, the aromatic polyester contained inside the particle and the aromatic polyester around the outside of the particle are strongly bonded through the pores of the shell wall. It is assumed that this is due to the fact that

The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness and abrasion resistance, and is characterized by not being harsh and generating significantly less white powder and the like.

The porous hollow organic particles used in the present invention have a high affinity with the aromatic polyester substrate as described above, and therefore voids are less likely to occur around the particles. Therefore, the frequency of occurrence of voids, which generally increases as the particle size increases, can be suppressed when using the above porous hollow organic particles. Combined with inert particles,
It has become clear that it is possible to provide a film that has the advantage of using two types of particles and has excellent runnability, abrasion resistance, fatigue resistance, electrical insulation, transparency, etc.

That is, such a biaxially oriented polyester film has (1) an aromatic polyester, (2) (a) a particle size ratio defined by the ratio of the maximum diameter to the minimum diameter of 1.0 to 1.2, and (b) ) The average hollowness ratio expressed by the following formula (A) is 0.00
1 to 0.95, Σ (Dxi, /[)i )3 , /n −(
A) i=1 Here, Dxi is the area circular diameter of the inner diameter of each particle (・
μm), Di is the area circle equivalent diameter of the outer diameter of each particle (μm), n is the number of particles, (C) the average particle size is o, oi ~ 5 μm, and (d
) Porous hollow organic particles with a specific surface area of 20 TIt and '1 or more by the BET method (based on aromatic polyester), and (3) an average particle size of 0.01 to 5 μm. A biaxially oriented polyester film comprising a mixture of 0.001 to 5% by weight (based on aromatic polyester) of inert particles.

Aromatic polyester (1) and porous hollow organic particles (2)
The details are as described above.

As the inert fine particles (3), those that are inert and insoluble in the aromatic polyester and solid at room temperature are used. These may be externally added particles or internally generated particles. Further, for example, a metal salt of an organic acid may be used, or an inorganic substance may be used. Preferred inert particles (3) include: -calcium carbonate, -silicon dioxide (including hydrates, diatomaceous earth, quartz sand, etc.), -alumina, and -silicic acid containing 30% or more of 5iQz. Salts (e.g. amorphous or crystalline clay minerals, aluminosilicate compounds (including calcined products and hydrates), warm asbestos, zircon, fly ash, etc.),
■Mg, Zn, Zr, and Ti oxides, ■Ca, □
and sulfates of Ba, ■ phosphates of Li, Ha, and Ca (including monohydrogen salts and dihydrogen salts), ■ Li, Na, and K
benzoate of, ■Ca, Ba, Zn, and) terephthalate of In, @1Mg, 'Ca, Ba, Zn, Cd
, titanate of Pb, Sr, Mn, Fe; Co, and N'i, chromate of @Ba and Pb, ■ carbon (e.g. carbon black, graphite, etc.), ■ glass (e.g. glass powder, glass beads). etc.), [phase]) IOco+
, ■ Fluorite, and [Co.] ZnS are exemplified.

Particularly preferred are calcium carbonate, anhydrous silicic acid, hydrated silicic acid, aluminum oxide, aluminum silicate (including calcined products, hydrates, etc.), monolithium phosphate, trilithium phosphate,
Lithium, sodium phosphate.

Calcium phosphate, barium fiR acid, titanium oxide, lithium benzoate, double salts of these compounds (including hydrates), glass powder, clay (including kaolin, bentonite, clay, etc.), talc, diatom, etc. Illustrated. Among such inert fine particles (3), externally added particles are particularly preferred. The porous hollow organic particles (2) have an average particle size of o, oi to 5 μm. Preferably 0.05-2μm1
Particularly preferably, they have an average particle size of 0.1 to 1.5 μm.

Further, the porous hollow organic particles (2) have o, ooi to 0.
It has an average hollowness ratio of 95. A preferable average hollowness ratio is 0.001 to 0.51, and a particularly preferable average hollowness ratio is 0.01 to 0.13.

Moreover, the inert particles (3) have an average particle size of 0.01 to 5 μm. It preferably has an average particle size of 0.05 to 2 μm, more preferably 0.1 to 1.5 μm.

The content of the inert particles (3) is 0.005 to 5% by weight based on the aromatic polyester, but preferably 0.01 to 1% by weight, especially 0.01 to 1% by weight. 05~0.
5% by weight is preferred. On the other hand, the content of porous hollow organic particles (2) is 0.005 to 5% by weight based on the aromatic polyester, but o, oi to 2% by weight, and even o, o.
i~1% by weight, especially 0.05 to 0.5% by weight is preferred.

If the content of the inert particles (3) or the porous hollow organic particles (2) is too small, the synergistic effect of using the two types of particles cannot be obtained, resulting in poor running performance, wear resistance, fatigue resistance, crushability, @
This is not preferable because properties such as surface uniformity deteriorate. On the other hand, if the content of inert particles (3) is too large, voids due to these particles tend to occur more frequently, resulting in poor wear resistance, fatigue resistance, crushability, insulation voltage, transparency, etc. descend.

Moreover, if the content of porous hollow organic particles (2) is too large,
This is not preferable because the surface of the film is too rough, and the electromagnetic conversion characteristics of the tape, for example, are deteriorated.

When producing the biaxially oriented film of the present invention, porous hollow organic particles or inert particles are mixed with the aromatic polyester by adding these particles to the aromatic polyester prior to or during the polymerization of the aromatic polyester. The mixture may be sufficiently kneaded with the aromatic polyester in a pot, in an extruder when pelletizing after completion of polymerization, or in an extruder when melt extruding into a sheet.

The polyester film of the present invention has, for example, a melting point (Tll
l: °C) or Tm +70) Aromatic polyester is melt-extruded at °C to achieve an intrinsic viscosity of 0.35 to 0.9 d.
An unstretched film of No. 110 was obtained, and the unstretched film was uniaxially (machine or transversely) (TO-10) to (TF
+70) °C (however, Tg: glass transition temperature of aromatic polyester) and stretched at a magnification of 2.5 to 5.0 times, and then in a direction perpendicular to the above stretching direction (if the -th stage stretching is in the longitudinal direction) , the second stage of stretching is in the transverse direction) and Tg (”
It can be produced by stretching at a temperature of C) to (7g+70)'C at a magnification of 2.5 to 5.0 times. In this case, the area stretching ratio is preferably 9 to 22 times, more preferably 12 to 22 times. The stretching means may be either simultaneous two-wheel stretching or sequential biaxial stretching.

Furthermore, the biaxially oriented film has a temperature of (7g+70)℃~Tm
It can be heat-set at a temperature of ('C). For example, for polyethylene terephthalate film, 190-2
It is preferable to heat set at 30°C.

The heat setting time is, for example, 1 to 60 seconds.

The thickness of the polyester film is preferably 1 to 100 μm, more preferably 1 to 50 μm, and especially 1 to 25 μm.

The polyester film of the present invention has a small coefficient of friction during running and has very good operability. Furthermore, when this film is used as a base for a magnetic tape, there is very little wear of the base film due to contact friction with the running part of a magnetic recording/reproducing device (hardware), and the durability is good.

Further, the biaxially oriented polyester film of the present invention has the advantage that it has good windability during film formation, is less likely to generate wrinkles, and can be cut dimensionally stably and sharply at the slitting stage.

By combining the above-mentioned advantages as a film product and advantages during film formation, the film of the present invention particularly has the following advantages:
It is extremely useful as a base film for high-grade magnetic applications, and has the advantage of being easy and stable to produce. The polyester film of the present invention can be used for high-grade magnetic recording media, such as micro-recording materials, compact or high-density floppy disk products, ultra-thin materials for long-term recording of audio and video, high-density recording magnetic films, and high-quality magnetic recording media. It is suitable as a base film for magnetic recording films for edge recording and reproduction, such as metal and vapor-deposited magnetic recording materials.

Therefore, according to the present invention, there is also provided a magnetic recording medium in which a magnetic layer is provided on one or both sides of the biaxially oriented polyester film of the present invention.

The magnetic layer and the method of providing the magnetic layer on the base film are known per se, and the known magnetic layer and method of providing the same can be employed in the present invention.

For example, when a magnetic layer is provided by applying a magnetic paint onto a base film, the ferromagnetic powder used for the magnetic layer is γ-Fe2 Q3. Co-containing γ-F
e3 (:)4, Co-containing Fe304, Cr
Q2. Known ferromagnetic materials such as barium ferrite can be used.

The binder used with the magnetic powder is a known thermoplastic resin, thermosetting resin, two-reaction type resin, or a mixture thereof. Examples of these resins include vinyl chloride-vinyl acetate copolymers and polyurethane elastomers.

The magnetic paint is further coated with an abrasive (e.g. α-/V20=, etc.)
, conductive agent (e.g. carbon black, etc.), dispersant (e.g. lecithin, etc.), lubricant (e.g. n-butyl stearate, lecithic acid, etc.), curing agent (e.g. epoxy resin, etc.)
and a solvent (for example, methyl ethyl ketone, methyl isobutyl lactone, toluene, etc.).

When the magnetic layer is provided by a method of forming a metal thin film on a base film, a method known per se such as vacuum evaporation method, sputtering method, ion blating method, C, V, (
), (Chemical Vapor ()eps
ition) law.

A method such as an electroless plating method can be employed.

Examples of metals include iron, cobalt, nickel, and alloys thereof (for example, Co-N1-P alloy, Co-Ni-Fe alloy, Co-Cr alloy, Co-old alloy, etc.).

The biaxially oriented polyester of the present invention can be used for various purposes in addition to the above-mentioned magnetic recording media.

For example, it is useful for uses such as capacitors, packaging, and vapor deposition.

Note that various physical property values and characteristics in the present invention were measured and defined as follows.

(1) Particle size etc. of porous hollow organic particles There are the following conditions for particle size measurement.

(i) Average particle size from porous hollow organic particle powder.

When determining particle size ratio, etc. (ii) When determining average particle size 1 particle size ratio, etc. of porous hollow organic particles in a film 1) Particle size (i) From porous hollow organic particle powder: Electron microscopy The porous hollow organic particle powder was scattered on the sample stage so that the individual particles did not overlap as much as possible, and a thin gold film was deposited on the surface using a gold sputtering device to a thickness of 200 to 300 layers, and then a scanning electron microscope was used. 10000~30 at
Observe at 1,000x magnification and measure the maximum diameter of at least 100 particles (D
li), minimum diameter (DSi) and area circular diameter (Di)
seek. Then, the maximum diameter (DI) of the porous hollow organic particles, ff
i represents the small diameter (DS) and average particle diameter (D).

D1=(Σ[)Ii),/n.

i=1 Ds=(Σ[)Si),/n.

i=1 mouth=(Σ[)i),/rl i=1 (ii) For porous hollow organic particles in a film:
A small piece of sample film was fixed on a sample stage for a scanning electron microscope, and a JEOL IHJ sputtering device (JFC-11
The surface of the film is subjected to ion etching using a 00 type ion sputtering apparatus under the following conditions. The conditions were to place the sample in a Pel jar, raise the degree of vacuum to approximately 1O-3 Torr, and apply a voltage of 0.25 KV and a current of 1.
Ion etching is performed at 2.5 mA for about 10 minutes. Furthermore, gold sputtering was applied to the film surface using the same equipment, and the film was observed at 10,000 to 30,000 times magnification using a scanning electron microscope.
Maximum diameter of at least 100 particles (Dli>) using Nihon Regulator (Tai-made Rubix 500).

The minimum diameter (DSi>) and the area circular diameter (Di) are determined.

The following steps are performed in the same manner as in (i) above.

2) Particle size ratio Determined from the ratio of the maximum diameter (Dl) and minimum diameter (Ds) determined in 1) above.

3) Relative standard deviation The area circular diameter (Di) obtained in 1) above and its average value (
D), and is determined by formula (B) described in the text.

(2) Particle size of inert particles, etc. 1) Average particle size (DP) Shimadzu CP-50 type Centrifugal Particle Size Analyzer (Centrifugal Particle 5iz)
e Analyser). The particle size corresponding to 50 mass percent is read from the integrated curve of particles of each particle size and their abundance calculated based on the obtained centrifugal sedimentation curve, and this value is defined as the above average particle size (Bookr particle size measurement technology) ” Published by Nikkan Kogyo Shimbun.

1975, 2, pp. 242-247).

2) Particle size ratio A small piece of the film is fixed and molded with epoxy resin, and an ultra-thin section (cut parallel to the film flow direction) with a thickness of approximately 600 mm is created using a microtome. The cross-sectional shape of the lubricant particles in the film was observed using a transmission electron microscope (Newly manufactured by Hitachi: Model H-800).
The ratio of the maximum diameter to the minimum diameter of each lubricant particle is determined and expressed as the average value.

3) Relative standard deviation A differential particle size distribution is obtained from the integration curve in the above 1), and the relative standard deviation is calculated based on the following definition formula of relative standard deviation.

Relative standard deviation -7nn --'- /Σ (Di-D)2・φi, /p J i=1 Here, Di is each particle size determined in 1), and the diameter is determined in 1) The obtained average particle diameter, n is the number of divisions when calculating the integration curve in section 1), and φi represents the existence probability (mass percentage) of particles of each particle size.

(3) Average Hollow Ratio of Particles After fixing and molding the lubricant particles with epoxy resin, ultra-thin sections with a thickness of approximately 600 mm were made using a microtome, and the sections were examined using a transmission electron microscope (Hitachi?A: H-800). type)
The cross-sectional shape of the lubricant particles is observed and expressed as the third power of the ratio of the outer diameter to the inner diameter of at least 50 particles.

(4) Determine the particle surface area SET by applying the adsorption theory. A constant pressure method is adopted as the measurement method, N2 is used as the adsorption substrate, and the measurement temperature is set to -195°C using a liquid nitrogen bath.

SET formula % formula % However, UPS is the nitrogen saturated vapor pressure at the measurement temperature, P is the nitrogen pressure at adsorption equilibrium, (2) is the adsorption amount at adsorption equilibrium, Vm is the monomolecular layer adsorption amount, and is a constant.

Draw the relationship between □ and □ on a graph V(Ps-P) Ps using P P , draw a straight line Ps with □ in the range of 0.05 to 0.35, and calculate Vm and K from its intercept and slope. do. In this case, the area occupied by nitrogen molecules is 16.2 people.

(5) Film surface roughness (Ra) This is the value defined in JIS-BO801 as the center line average roughness (Ra), and in the present invention, ). The measurement conditions are as follows.

(a) Stylus tip radius: 2 μm (b) Measurement pressure: 30 mg (C) Cutoff: 0.25 mm (d) Measurement length
: 0.5mm (e) How to summarize the data - Repeat the measurement 5 times for the sample, and mark the largest value as 1.
The average value of the remaining four data is rounded off to the fourth decimal place and displayed to the third decimal place.

(6) Void ratio in the film (surface) according to the method (1)-2) above.
The area around the lubricant particles is exposed, and the major axis of at least 50 solid fine particles and the major axis of the voids are measured, and expressed as the number average value of the void ratio determined by the following formula: Long axis void ratio of the voids = □ Long axis of the solid fine particles.

(7) Film friction coefficient (μk) In an environment of temperature 20℃ and humidity 60%, a film cut to a width of 172 inches is held on a fixed rod (surface roughness 0.3μm) at an angle θ = (152/180) π radian. (152") and move (friction) for 10m at a speed of 20Cm/SeC. Repeat this 200 times. At that time, adjust the tension controller so that the inlet tension T1 is 35g, and repeat 200 times. The exit tension (T2:IJ) after the treading is detected by the exit tension detector, and the running friction coefficient μk is calculated using the following formula.

μk = (2,303,/θ) 10(1(T2/T
I>-0,868log (T2/35) (8) Scrapability The scratchability of the running surface of the film is evaluated using a 5-stage mini super calendar. The calender is a 5-stage calender with nylon rolls and steel rolls, the processing temperature is 80°C, and the linear pressure applied to the film is 200 kg/cm.
The film was run at a speed of 50 m/min. After running the running film for a total length of 2000 m, the abrasion resistance of the base film was evaluated based on the dirt that adhered to the top roller of the calendar.

4-level evaluation> ◎ No stains on the nylon roll ○ Almost no stains on the nylon roll

Comparative Example 1 Dimethyl terephthalate and ethylene glycol were mixed with manganese acetate (ester exchange catalyst), antimony trioxide (polymerization catalyst), phosphorous r1i (stabilizer) and average particle size of 0.5
Polyethylene terephthalate with an intrinsic viscosity of 0.62 was obtained by polymerization by a conventional method in the presence of kaolin (lubricant) with a particle size ratio of 5 μm and 10.

This polyethylene terephthalate pellet was
℃, after drying for 3 hours, the molten polymer is fed to an extruder hopper and melted at a melting temperature of 280 to 300℃.
Through the slit-shaped die, the surface finish is about 0.3S,
Extruded onto a rotating cooling drum with a surface temperature of 20℃, 200μ
An unstretched film of m was obtained.

The unstretched film thus obtained was preheated at 75°C, and further heated with one IR heater at a surface temperature of 900″C from 15mm above between low-speed and high-speed rolls.
Stretched longitudinally by 3.5 times due to the difference in surface speed between low and high speed rolls,
It was rapidly cooled, then supplied to a stenter and stretched 3.7 times in the transverse direction at 105°C. The 1q biaxially stretched film was heat set at a temperature of 205° C. for 5 seconds to obtain a biaxially oriented film with a thickness of 15 μm.

Although the resulting film had good abrasion resistance, it had a large running friction coefficient and was unsatisfactory.

The properties of this film are shown in Table 1.

Comparative Example 2 Instead of kaolin, average particle size 0.73 μm2 particle size ratio 1.4
A biaxially oriented film with a thickness of 15 μm was obtained in the same manner as in Comparative Example 1 except that calcium carbonate was used. Although this film had good running properties, white powder was generated during the calendering process. The properties of this film are shown in Table 1.

Comparative Examples 3 and 4 Instead of kaolin, average particle size 0.66 μm 1 particle size ratio 10
porous silica (Comparative Example 3), or average particle size of 0.34
A biaxially oriented film with a thickness of 15 μm was obtained in the same manner as in Comparative Example 1 except that calcium carbonate (Comparative Example 4) having a μm2 particle size ratio of 1.4 was used.

Although the material of Comparative Example 3 had good machinability, it had a large running friction coefficient and was unsatisfactory. The surface of Comparative Example 4 was flat, but the running properties were poor and white powder was generated, making it unsatisfactory. These properties are shown in Table 1.

Examples 1 to 3 A biaxially oriented film with a thickness of 15 μm was obtained in the same manner as in Comparative Example 1, except that the porous hollow organic particles listed in Table 1 were used instead of kaolin. All films had a flat surface and excellent running properties, and were satisfactory in that the amount of scratches and white powder produced was small.

These properties are shown in Table 1.

Comparative Example 5 A biaxially oriented film with a thickness of 15 μm was obtained in the same manner as Comparative Example 1 except that the porous hollow organic particles listed in Table 1 were used instead of kaolin. This film has good running properties because the porous hollow organic particles have an excessively large particle size.
The surface was rough and a large amount of white powder was generated, which was unsatisfactory. These properties are shown in Table 1.

Comparative Examples 6 to 8 Biaxially oriented films with a thickness of 15 μm were obtained in the same manner as in Comparative Example 1, except that the fine particles listed in Table 1 were used instead of kaolin.

In Comparative Examples 6 to 8, since the films of Comparative Examples 1 to 4 were unsatisfactory, the abrasion resistance was improved by adding calcium carbonate with a small particle size together with kaolin or porous silica with a large particle size. However, the improvement effect was small and unsatisfactory. These properties are shown in Table 1.

Examples 4 to 6 A biaxially oriented polyester film having a thickness of 15 μm was obtained in the same manner as in Comparative Example 6 except that the fine particles shown in Table 1 were used. Since these films used porous hollow organic particles as small particles, the running resistance was low and the generation of white powder was extremely small, which was satisfactory. These properties are shown in Table 1.

Example 7 Porous hollow particles with an average particle size of 0.54 μm were prepared by uniformly dispersing manganese acetate as a transesterification catalyst in a mixture of dimethyl terephthalate and ethylene glycol, lithium acetate and calcium acetate dissolved in ethylene glycol, and ethylene glycol. Add organic particles O,OS in constant% (relative to polyester) and carry out a transesterification reaction by a conventional method. When the Nisder exchange reaction is completed, trimethyl phosphate and antimony trioxide as a polymerization catalyst are added and polycondensation is carried out by a conventional method. By reacting, the intrinsic viscosity (0
-chlorophenol, 35°C) 0.62 of polyethylene terephthalate.

When the amount of internally precipitated particles in this polyethylene terephthalate was determined by the aforementioned particle separation method, it was found that the internally precipitated particles corresponded to the suspension of the porous hollow organic particles added as external additive particles. In addition, when the polyethylene terephthalate was sandwiched between prepared plates, dissolved, and then observed under a microscope after cooling, it was found that many particles had an average particle size of 0.7 μm and 0.54 μm.
It was found that m spherical particles were mixed therein. The former are internal precipitated particles precipitated in the polymer during polyester production, and the latter are porous hollow organic particles added from the outside.

Next, the polyethylene terephthalate was heated to 280 to 30
Melt extrusion from a slit at 0°C, quenching, stretching and heat setting of the unstretched film at a longitudinal stretch ratio of 3.5 times, a transverse stretch ratio of 3.7 times, and a heat treatment temperature of 205°C, resulting in a thickness of 1
A biaxially oriented film of 5 μm was obtained.

The properties of this film are shown in Table 1.

The 1q film yielded a small amount of white powder and had excellent runnability, which was satisfactory.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the cross-sectional shape of a hollow particle. 1: shell wall, 2: pore, 3: cavity, 4: inner diameter. 5: Outer diameter

Claims (1)

[Claims] 1. (1) an aromatic polyester, and (2) (a) a particle size ratio defined by the ratio of maximum diameter to minimum diameter of 1.0 to 1.2, and (b) The average hollowness ratio expressed by the following formula (A) is 0.00
1 to 0.95, ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(A) Here, Dxi is the area circle equivalent diameter of the inner diameter of each particle (μ
m), Di is the area circle equivalent diameter of the outer diameter of each particle (μm), n is the number of particles, (c) the average particle size is 0.01 to 5 μm, and (d) the ratio according to the BET method A biaxially oriented polyester film comprising a mixture of 0.001 to 5% by weight (based on aromatic polyester) of porous hollow organic particles having a surface area of 20 m^2/g or more. 2. The film according to claim 1, wherein the porous hollow organic particles are made of a thermosetting resin or a crosslinked polymer. 3. The film according to claim 1, wherein the porous hollow organic particles have a relative standard deviation represented by the following formula (B) of 0.5 or less. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(B) Here, Di is the area circle equivalent diameter of each particle (μm), @D@ is the average value of the area circle equivalent diameter (μm), ▲Mathematical formula , chemical formulas, tables, etc. ▼ n is the number of particles. 4, (1) aromatic polyester, (2) (a) has a particle size ratio defined by the ratio of maximum diameter to minimum diameter of 1.0 to 1.2, (b) is represented by the following formula (A) The average hollowness ratio is 0.00
1 to 0.95, ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(A) Here, Dxi is the area circle equivalent diameter of the inner diameter of each particle (μ
m) Di is the area circle equivalent diameter of the outer diameter of each particle (μm), n is the number of particles, (c) the average particle diameter is 0.01 to 5 μm, and (d) the specific surface area by the BET method. 0.001 to 5% by weight (based on aromatic polyester) of porous hollow organic particles having a particle size of 20 m^2/g or more, and (3) 0 other inert particles having an average particle size of 0.01 to 5 μm. Biaxially oriented polyester film consisting of a mixture of .001 to 5% by weight (based on aromatic polyester).