JP2001034931A - Polyester film for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve slipperiness, running properties and abrasion resistance by a method wherein a polyester A layer for which deposit particles containing calcium and phosphorus and inactive particulates are specified is laminated on a polyester B layer and the ratio of the Young's modulus in the lateral and longitudinal directions of a film, the root-mean-square roughness, mean roughness and maximum roughness of the surface of the polyester A layer are made to be in specified ranges. SOLUTION: A polyester A layer contains deposit particles containing calcium and phosphorus and having a mean particle size of 0.7-1.5 μm by 0.01-0.1 wt.%, inactive particulates having a mean particle size of 0.1-1.0 μm by 0.1-1.0 wt.% and inactive particulates having a mean primary particle size of 0.3 μm or below and a Mohs hardness of 7 or above by 0.01-1.0 wt.%. The ratio between the Young's modulus YTD in the lateral direction of a film and the Young's modulus YMO in the longitudinal direction thereof is expressed by the formula. Besides, the root-mean-square roughness of the surface of the polyester A layer is made to be in the range of 0.010-0.025 pm, the mean surface roughness thereof in the range of 0.005-0.020 μm and the maximum roughness thereof in the range of 0.200-0.350 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biaxially oriented polyester film. Specifically, the present invention, as a base film for a high-quality magnetic recording medium, has excellent slit properties during film production and magnetic recording medium production, and highly satisfies the durability running performance and electromagnetic conversion characteristics as a magnetic recording medium, The present invention also relates to a biaxially oriented polyester film which is excellent in preventing dropout.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are widely used as industrial materials because they have various properties in a highly balanced manner and are excellent in cost performance. Among the many uses of polyester films, especially for magnetic tapes, in recent years, the required properties of base films for improving the quality of magnetic tapes have become increasingly sophisticated. That is, it is strongly desired that the film surface be flat in order to improve the electromagnetic conversion characteristics. In particular, it is an essential condition that there are no coarse projections that cause dropout. On the other hand, in order to improve the running property of the magnetic recording medium, it is necessary to appropriately roughen the film surface and lower the friction coefficient of the film.

In addition to these requirements, recently, it has been desired that the film be excellent in slitting property particularly in the production of films and magnetic recording media. If the slit property is insufficient, wrinkles may occur because the shape of the slit end face is not uniform at the time of film production, or a problem that the slit blade must be replaced frequently may occur. In addition, chips generated by the slit,
There is a problem that cutting powder generated in a slitting process at the time of manufacturing a magnetic recording medium adheres to a film surface or a magnetic layer surface to cause dropout.

On the other hand, in the process of processing a film, the surface of the film is scraped off by contact with a roll or a guide in a magnetic layer coating process, a calendering process, a winding process, etc. in manufacturing a magnetic recording medium. However, there is a problem that electromagnetic conversion characteristics are deteriorated and shaving powder causes dropout. Also, particularly with the recent spread of video software, high-speed dubbing apparatuses have been used to improve the productivity of soft video tapes, and when such high-speed dubbing apparatuses are used, magnetic tapes, and thus base films for magnetic tapes, are used. High quality has come to be required. That is, the running speed of the tape during dubbing is higher than the running speed during normal video playback,
A different design from that of the conventional magnetic tape is required. For example, the running stability at high speed running is good and it does not meander, the magnetic tape is shaved during running,
It is required that the shaving powder does not cause a problem such as dropout.

In addition to these strict requirements for quality, there is also a strong demand for cost reduction, and it is essential that base film productivity be good.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a film having excellent slitting properties at the time of manufacturing a film and a magnetic recording medium, and having good running properties as a magnetic recording medium. Another object of the present invention is to provide a film which can satisfy the electromagnetic conversion characteristics to a high degree, is excellent in preventing the occurrence of dropout, and is extremely free from scratches and abrasion powder.

[0007]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventor has found that a laminated film containing specific particles has excellent characteristics, and has completed the present invention. That is, the gist of the present invention is that the precipitated particles having an average particle diameter of 0.7 to 1.5 μm containing calcium and phosphorus precipitated in a polyester production reaction system are 0.01 to 0.1% by weight, Particle size is 0.1-1.0
0.1 to 1.0% by weight of inert fine particles having an average primary particle diameter of 0.3 μm or less and a Mohs hardness of 7 μm.
A biaxially oriented polyester film obtained by laminating a polyester A layer containing 0.01 to 1.0% by weight of the above inert fine particles on a polyester B layer, wherein the following formulas (1) to (4) are simultaneously A polyester film for a magnetic recording medium characterized by satisfying.

[0008]

(Equation 2) 0.010 ≦ RMS ≦ 0.025 (2) 0.005 ≦ SRa ≦ 0.020 (3) 0.200 ≦ PV ≦ 0.350 (4) (where Y _MD is a film Young's modulus in the vertical direction (GP
a), Y _TD is the Young's modulus (GPa) in the transverse direction of the film,
RMS is the root mean square roughness (μm) of the polyester A layer surface, SRa is the average surface roughness (μm) of the polyester A layer surface, and PV is the maximum roughness (μm) of the polyester A layer surface.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester of the present invention is a polyester obtained by using an aromatic dicarboxylic acid or an ester thereof and a glycol as main starting materials, and 80% of the repeating structural units.
The above is ethylene terephthalate unit or ethylene-
Refers to a polyester having 2,6-naphthalate units or 1,4-cyclohexylene dimethylene terephthalate units. And if it is in the said range, you may contain another 3rd component.

As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, diphenyldicarboxylic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid, etc.) can be used. As the glycol component, in addition to ethylene glycol and 1,4-cyclohexanedimethanol, for example, one or more of diethylene glycol, triethylene glycol, propylene glycol, butanediol, neopentyl glycol, and the like can be used.

In order to improve the slipperiness, running properties and abrasion resistance of the film, to maintain flatness and to prevent the occurrence of scratches during the production of the film, particles are usually added to the polyester so that appropriate projections are formed on the film. Let it form. The present inventor has found that when the specific particles are used, the above-described effects can be highly achieved. That is, the precipitated particles having an average particle diameter of 0.7 to 1.5 μm containing calcium and phosphorus precipitated in the polyester production reaction system are 0.01 to 0.1 μm.
% Of inert fine particles having an average particle size of 0.1 to 1.0 μm, and 0.1 to 1.0% by weight of inert fine particles having an average primary particle size of 0.3 μm or less and a Mohs hardness of 7 or more. In the case of having a polyester A layer containing 0.01 to 1.0% by weight of active fine particles, the slipperiness and flatness of the film are highly satisfied. Since the abrasion is good and the flatness is excellent, a high quality magnetic recording medium having good electromagnetic conversion characteristics can be obtained.

In the present invention, the particles precipitated in the production reaction system are those in which the catalyst such as the calcium compound used in the transesterification reaction is precipitated as fine particles in the polyester production reaction system in the presence of the phosphorus compound. in this case,
After the transesterification reaction, a calcium compound may be added to form fine particles, and the same method is applicable to the case where the reaction is conducted via an esterification reaction.

In the present invention, it is preferable to use a trialkyl phosphate and a trialkyl phosphite as the above-mentioned phosphorus compound, because when used as a polyester film for a magnetic recording medium, higher abrasion resistance can be imparted. That is, in the polyester production reaction system, for the calcium compound soluble in the reaction system,
It is preferable to include particles precipitated by allowing a trialkyl phosphite and a trialkyl phosphate to act thereon, and the particles have a calcium element and a phosphorus element of 0.7 to 2.5 as a molar ratio of a phosphorus element to a calcium element. In a proportion of

When the molar ratio of the elemental phosphorus to the elemental calcium in the precipitated particles is less than 0.7, the particles tend to be easily broken by stretching, and the film may not be given a high degree of slipperiness. . On the other hand, when the molar ratio exceeds 2.5, a large amount of the phosphorus compound necessarily exists in the polymer, and the polymerization rate during the production of the polyester tends to be slow.

In the present invention, other metal elements such as lithium, zinc, manganese, magnesium,
Preferably, it does not substantially contain barium element or the like. The reason is that, when the precipitated particles are formed in the coexistence of a metal element other than calcium, the precipitated form often changes, and stable inert fine particles cannot be obtained. The amount of the metal element other than calcium in the precipitated particles is preferably 0.1 times or less, more preferably 0.05 times or less the molar amount of the calcium element.

In the present invention, the content of the precipitated particles in the polyester A layer is from 0.01 to 0.1% by weight, preferably from 0.015 to 0.08% by weight, more preferably from 0.05% by weight.
2 to 0.05% by weight. Precipitated particle content is 0.01
When the amount is less than 0.1% by weight, the effect of improving the winding characteristics at the time of film production and the production of the magnetic recording medium becomes insufficient. When the amount exceeds 0.1% by weight, the winding characteristics of the magnetic recording medium are good, but the film is processed. In the process, the film surface is scraped off by contact with a roll or a guide in a magnetic layer coating step, a calendaring step, a winding step, etc. in manufacturing a magnetic recording medium, and the electromagnetic conversion characteristics are deteriorated due to the scratch, There is a problem that shavings cause dropout.

The average particle size of the precipitated particles is 0.7 to
It is 1.5 μm, preferably 0.8 to 1.4 μm, more preferably 0.9 to 1.2 μm. If the average particle size of the precipitated particles is less than 0.7 μm, the effect of improving the film winding property is insufficient, which is not preferable. On the other hand, when the average particle size is 1.5
If it exceeds μm, the protrusions on the film surface become too large, and the flatness and abrasion resistance of the film deteriorate. In particular, when used for a magnetic recording medium, a problem that the electromagnetic conversion characteristics are deteriorated occurs.

The method for producing the precipitated particles used in the present invention is diversified and cannot be described in detail. However, as a specific example, the particles can be produced by the following method. That is, one or more calcium compounds are added before or during the transesterification reaction, and then a plurality of phosphorus compounds consisting of a trivalent phosphorus compound and a pentavalent phosphorus compound are added to the reaction system before the polycondensation reaction. Obtainable. Even within this range, the precipitated fine particle form depends on the molar ratio of the phosphorus compound to the calcium compound, the molar ratio of the pentavalent phosphorus compound to the trivalent phosphorus compound, the time of addition of the phosphorus compound, and polymerization conditions such as heating and decompression. Therefore, conditions must be appropriately selected from these combinations so as to be within the range of the average particle diameter and the particle amount of the present invention.

Particularly preferred methods among them are as follows. That is, first, as an ester exchange reaction catalyst, 0.05 wt
The transesterification reaction is carried out using a calcium compound of about 0.3 mol%, preferably 0.08 to 0.14 mol%. At this time, the calcium compound that can be used may be any compound as long as it is a calcium compound soluble in the reaction system, for example, a calcium salt of an aliphatic carboxylic acid such as acetic acid, propionic acid, and butyric acid, benzoic acid, p-methylbenzoic acid. Examples thereof include calcium salts of aromatic carboxylic acids such as acids, calcium compounds such as calcium glycolates such as ethylene glycol and propylene glycol, and inorganic compounds such as calcium hydride. Among them, calcium acetate is particularly preferably used.

Next, the transesterification reaction is substantially terminated, and two kinds of trivalent and pentavalent phosphorus compounds are added to the reaction mixture. In this case, the trivalent phosphorus compound is, for example, phosphorous acid, Trimethyl phosphite, tributyl phosphite, triethyl phosphite, dimethyl phosphite, diethyl phosphite, monobutyl phosphite and dibutyl phosphite, and the like,
On the other hand, examples of the pentavalent phosphorus compound include trialkyl phosphates, in particular, trimethyl phosphate, triethyl phosphate or tributyl phosphate.

The molar ratio of the pentavalent phosphorus compound to the trivalent phosphorus compound is 1 to 20, more preferably 2 to 10, and the total amount of these phosphorus compounds is based on the calcium compound previously used as the transesterification catalyst. It is good to make it 1 to 3 times mol. When the molar ratio of the pentavalent phosphorus compound to the trivalent phosphorus compound is less than 1, the obtained polymer tends to be dark, and black foreign matter tends to be generated during the production of the polymer, and it tends to be difficult to perform a stable operation. If it exceeds 20, the amount of precipitated particles is small, and the effect of imparting lubricity may be insufficient. When the molar ratio of the total amount of the phosphorus compound to the calcium compound is less than 1, the molar ratio of the phosphorus element to the calcium element in the precipitated particles becomes less than 0.7, and the particles tend to be easily broken by stretching. If this value exceeds 3, the polymerization rate during polymer production tends to be slow.

When a metal element other than calcium is present at the time of adding the phosphorus compound, for example, when a calcium compound is added after performing a transesterification reaction using lithium, zinc, manganese, magnesium, barium compound, or the like, In the case where the transesterification reaction is carried out in the coexistence of a metal compound and a calcium compound, the particle size and the particle amount of the obtained particles are often out of the range of the present invention. If metal elements other than calcium element are contained beyond the permissible limit, they become unsuitable as particles of the present invention.

The phosphorus compound is added at a temperature of 225 to 250 ° C.
A temperature of 30 to 240 ° C. is preferable because an appropriate average particle size and particle amount are obtained. The feature of the polyester film of the present invention resides in that a combination of the specific particle size and the specific amount of the precipitated particles and the specific particle size and the specific amount of the inert fine particles are used.

That is, in addition to the above-mentioned precipitated particles, the average particle diameter (d50) is 0.1 to 1.0 μm as additional particles.
m, preferably 0.2 to 0.8 μm, more preferably 0.3 to 0.6 μm, 0.1 to 1.0% by weight, preferably 0.2 to 0.9% by weight, By preferably containing 0.3 to 0.8% by weight of the polyester A layer, high film handling properties and magnetic tape properties can be obtained.

When the average particle size of the inert fine particles is less than 0.1 μm, appropriate protrusions cannot be formed on the film surface, and the effect of improving the running property of the film cannot be obtained. Agglomeration tends to occur, causing the problem of formation of coarse projections, which causes dropout when used for magnetic recording media. On the other hand, when the average particle size of the inert fine particles exceeds 1.0 μm, the protrusions on the film surface become too large, and the flatness and abrasion resistance of the film decrease. In particular, when used for a magnetic recording medium, a problem that the electromagnetic conversion characteristics are deteriorated occurs.

When the content of the inert fine particles is less than 0.1% by weight, the slipperiness of the film and the running property of a magnetic recording medium cannot be satisfied. On the other hand, if the content of the inert fine particles exceeds 1.0% by weight, the electromagnetic conversion characteristics deteriorate,
Particles may fall off to cause dropout, and the slitting property of the film may be reduced, causing problems such as troubles in the slitting process.

In the present invention, as the inert fine particles to be used, for example, inorganic particles such as calcium carbonate, silica, calcium phosphate, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, etc. And organic particles such as calcium oxalate and crosslinked polymer particles, and one or more of these can be contained.

In the present invention, in order to improve the abrasion resistance and abrasion resistance of the film, inorganic particles having an average primary particle diameter of 0.3 μm or less and a Mohs hardness of 7 or more are added to the above-mentioned particles. It is essential that the polyester A layer be contained in the range of 0.01 to 1.0% by weight. Preferably, the particles have a size of 0.1 μm or less. The amount of particles having a Mohs' hardness of 7 or more is 0.1 to
When the content is 0.5% by weight, the slitting property is particularly good, which is preferable.

Examples of particles having a Mohs hardness of 7 or more include alumina, silicon carbide, vanadium carbide, titanium carbide, boron carbide and the like. Among these, alumina which is easily available industrially and has a large effect of improving scratch resistance is preferable,
Among them, δ-type alumina and γ-type alumina are particularly preferable. Inorganic particles with a Mohs hardness of 7 or more
More than one species may be used in combination.

As a method for producing alumina particles, for example, a thermal decomposition method, that is, a method of performing flame hydrolysis using anhydrous aluminum chloride as a raw material, or an ammonium alum pyrolysis method, that is, a method of reacting with aluminum sulfate as a raw material and reacting with aluminum sulfate to form aluminum sulfate After that, a method of reacting with ammonium sulfate and calcining as ammonium alum can be mentioned. The primary particle size of the alumina obtained by these methods is usually in the range of 5 to 40 nm, but often forms aggregates exceeding 0.5 μm. When used in the present invention, secondary particles that are slightly aggregated may be formed, but the apparent average particle size is preferably 0.5 μm or less, particularly preferably 0.2 μm or less.

Fine particles may be contained in the polyester B layer in some cases, for example, because recycled materials generated during the production of the film are used, but the content of the particles in the B layer is 1.0%.
It is desirably not more than 0.5% by weight, more preferably not more than 0.5% by weight. When the content of the particles in the B layer exceeds 1.0% by weight, the slitting properties may be reduced. In the production of polyester containing particles constituting the film of the present invention,
The particles may be added during the polyester synthesis reaction or may be added directly to the polyester. When it is added during the synthesis reaction, a method in which the particles are added as a slurry in which the particles are dispersed in ethylene glycol or the like at an arbitrary stage of polyester synthesis is preferable. On the other hand, when directly added to the polyester, it is used as dried particles,
A method in which a slurry dispersed in an organic solvent at 0 ° C. or lower is added to and mixed with the polyester using a twin-screw kneading extruder is preferable. In addition, the particles to be added may be subjected to processing such as crushing, dispersion, classification, and filtration as needed.

The term "laminated film" as used in the present invention means a film extruded by a so-called co-extrusion method in which all layers are co-melt extruded from a die of an extruder and stretched and heat-treated. The laminated structure has a structure in which the A layer is laminated on at least one side of the B layer.
In addition to the layer film, 4
It may be a layer or more layers. For example, when the A layer is laminated on both sides of the B layer, a mode in which the B layer has a two-layer or three-layer structure and the entire film is a four-layer or five-layer film can be adopted. The excellent effects of the present invention can be obtained by including the above-mentioned particles in at least one outermost layer, which is the layer A.

The layer A may be on one side of the film,
It may be on both sides. A layer C may be provided on the opposite side of the layer A. The C layer may be composed of a composition different from that of the A layer,
It is made of the same polyester composition as the layer A, and can be provided as layers having different thicknesses. By using such a configuration, it is possible to obtain a film having surfaces with different roughness on the front and back, and it is possible to simultaneously satisfy a high degree of electromagnetic conversion characteristics and running properties of the magnetic recording medium. In particular, the C layer
When the layers are formed of the same polyester composition as the layers and have different thicknesses, the manufacturing process can be simplified, the cost can be reduced, and the physical properties such as surface roughness can be easily adjusted. In the case of such a configuration, the thickness tC of the C layer is the thickness of the A layer t.
The range of A to 0.05 to 0.8 times, and more preferably 0.1 to 0.7 times is desirable. If tC / tA exceeds 0.8, a sufficient difference in front and back of the surface roughness may not be obtained. On the other hand, t
When C / tA is less than 0.05, the thickness of the C layer becomes thin,
A problem that the wear resistance is insufficient may occur.

The film of the present invention has a root-mean-square roughness (RMS) of the layer A surface of 0.010 to 0.025 μm, preferably 0.012 to 0.020 μm, and an average surface roughness (SRa) of the surface of the layer A. Is 0.005 to 0.020 μm, preferably 0.007 to 0.015 μm, and the maximum height (PV) of the A layer surface is 0.200 to 0.350 μm, preferably 0.220 to 0.300 μm. By being in the range,
It can be an advanced magnetic recording medium film.

If any one of RMS, SRa and PV falls outside the above lower limits, the handling properties of the film, the winding properties, and the running properties of a magnetic tape become insufficient. On the other hand, if any of RMS, SRa, and PV are outside the above upper limits, the electromagnetic conversion characteristics of the magnetic tape deteriorate, which is not preferable. The difference between the center line roughness SRaA of the surface of layer A constituting one surface of the film of the present invention and the surface roughness SRa ′ of the other surface is preferably 1 to 10 nm, more preferably 1.5 to 8 nm. And particularly preferably 2 to 5 nm
Range. 10n difference in surface roughness only by difference in layer thickness
If the thickness exceeds m, the difference in thickness must be increased, and the same problem as described above occurs.

The intrinsic viscosity of the polyester constituting the layer B of the film of the present invention is usually less than 0.600, preferably less than 0.580, and more preferably less than 0.570. When the intrinsic viscosity is 0.600 or more, the slit property of the film may be deteriorated. The lower limit of the intrinsic viscosity of the B layer is
From the viewpoint of film productivity, it is usually 0.450, preferably 0.480, and more preferably 0.500. A
Depending on the intrinsic viscosity of the layer, the intrinsic viscosity of the layer B is 0.450.
If it is less than 30, the breaking frequency during film production tends to increase.

Further, the intrinsic viscosity of the layer A is preferably higher than that of the layer B by 0.02 or more, more preferably 0.03 or more. When the intrinsic viscosity of the surface layer is low, the abrasion resistance of the film tends to deteriorate. The intrinsic viscosity of the A layer is preferably 0.570 or more, more preferably 0.580 or more.
The value is particularly preferably 0.600 or more. The film of the present invention has a ratio of the Young's modulus in the transverse direction (Y _TD ) to the Young's modulus in the machine direction (Y _MD ) in the range of 1.2 to 1.8, preferably 1.3 to 1.7. is there. When the ratio of the Young's modulus in the horizontal direction (Y _TD ) to the Young's modulus in the vertical direction (Y _MD ) is less than 1.2, the slitting property of the film is deteriorated, and the productivity at the time of magnetic tape production is reduced. The problem that the dropout characteristics of the magnetic tape deteriorate due to the generated foreign matter occurs. If the ratio of the Young's modulus in the horizontal direction (Y _TD ) to the Young's modulus in the vertical direction (Y _MD ) exceeds 1.8, productivity during film production deteriorates, which is not preferable.

Next, a method for producing a film according to the present invention will be described, but the present invention is not limited to the following production method. The polyester raw material constituting the film is supplied to an extruder and extruded as a molten sheet from a slit die. In the case of manufacturing as a laminated film, the polyester raw material constituting each layer is supplied to an extruder for coextrusion and lamination. That is, 2
Alternatively, three or more extruders, three or more layers are stacked using a multi-manifold or a feed block, and extruded as a three or more layers molten sheet from a slit die. At that time, the thickness of each layer can be set by adjusting the flow rate of the polymer by a fixed-quantity feeder such as a gear pump installed on the melt line.

Next, the molten sheet extruded from the die is rapidly cooled and solidified on a rotary cooling drum so as to have a glass transition temperature or less, to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is necessary to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method or the liquid application adhesion method is preferably employed.

In the present invention, the sheet thus obtained is biaxially stretched to form a film. When the stretching conditions are specifically described, the unstretched sheet is preferably 70 to 150 ° C, more preferably 75 to 130 ° C.
At a temperature range of 3.0 to 7 times, preferably 3.2 to 6 times in one direction by a roll or tenter type stretching machine.
Stretch twice. Next, the film is stretched 3.2 to 7 times, preferably 3.5 to 6 times in a temperature range of preferably 75 to 150 ° C., more preferably 80 to 140 ° C. in a direction orthogonal to the first stage, and biaxially stretched. Obtain an oriented film. Incidentally, a method of performing unidirectional stretching in two or more stages can also be used,
Also in that case, it is desirable that the final stretch ratio falls within the above range. In addition, the unstretched sheet has an area magnification of 10
Simultaneous biaxial stretching can be performed so as to be up to 40 times.

The thus obtained film was prepared for 150 to 25
Heat treatment at 0 ° C. for no more than 30% elongation, limited shrinkage, or constant length for 1 second to 5 minutes. After biaxial stretching, another 11
A method of performing re-stretching in the longitudinal direction at a temperature of 0 ° C. to 180 ° C. by 1.05 to 2.5 times, and then performing a heat treatment may be employed. At this time, techniques such as heat setting before re-longitudinal stretching, longitudinal relaxation after re-longitudinal stretching, and longitudinal stretching at a micro-magnification before or after re-longitudinal stretching can be appropriately adopted. In addition, re-stretching may be similarly performed in the lateral direction. Further, various surface treatments or the like may be performed in the film forming process as needed.

Further, when the film of the present invention is used particularly for a magnetic recording medium, a coating layer may be provided on the film surface in order to enhance the adhesiveness with the magnetic layer. The coating layer may be provided in the film manufacturing process, or may be applied after the film is manufactured. In particular, from the viewpoint of uniformity of coating thickness and production efficiency, a method in which coating is performed after stretching in the longitudinal direction in the film production step and before the transverse stretching step is preferable.

Examples of the coating agent include polyester, polyamide, polystyrene, polyacrylate, polycarbonate, polyarylate, and the like, which have excellent adhesion to the magnetic layer.
Examples thereof include resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl butyrate, polyvinyl alcohol, and polyurethane, and copolymers and mixtures of these resins, but are not limited thereto. The most preferred coating agent among these is a polyester resin. Further, in order to prevent a decrease in handleability due to blocking of the film, it is preferable to incorporate a crosslinking component into the coating layer. As the crosslinking component, a crosslinking agent such as an epoxy-based, melamine-based, isocyanate-based, aziridine-based, or oxazoline-based crosslinking agent can be used.

The coating agent used in the present invention is desirably a coating agent using water as a medium. When using water as the medium,
A coating agent forcibly dispersed by a surfactant or the like may be used, but a hydrophilic nonionic component such as a polyether or a self-dispersing coating agent having a cationic group such as a quaternary ammonium salt is preferable. And more preferably a water-soluble or water-dispersible resin coating having an anionic group.

Particularly when used as a base film for a magnetic recording medium for a video pancake used in a high-speed dubbing apparatus, it is effective to improve the quality by performing such easy adhesion treatment and preventing the magnetic layer from peeling off. It is. In the present invention, the amount of 1
0% by weight or less of other polymers (eg, polyethylene, polystyrene, polycarbonate, polysulfone,
Polyphenylene sulfide, polyamide, polyimide, etc.). If necessary, additives such as an antioxidant, a heat stabilizer, a lubricant, a dye, and a pigment may be added.

[0046]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The measuring methods and definitions of various physical properties and characteristics in the examples are as follows. In the examples and comparative examples, “parts” means “parts by weight”. (1) Average particle size, particle size distribution value, particle size ratio In the case of precipitated particles, a polyester film containing the particles is sandwiched between preparations, melted, cooled, observed with a microscope, and the image is processed by a Leica image processing apparatus. (Quantime
The average particle size was measured using t500 +).

When the added particles were in a powder state before the addition of the polyester, they were measured with a centrifugal sedimentation type particle size distribution analyzer (SP-CP3 type) manufactured by Shimadzu Corporation. Regarding the added particles in the film, the film is dissolved in a mixed solvent of phenol / tetrachloroethane = 50/50 (solvent 75
microgram by laser diffraction / confusion method (Nikkiso HRA9320-X10)
0). (2) Amount of precipitated particles 1.0 liter of o-chlorophenol was added to 100 g of polyester, heated at 120 ° C. for 3 hours, and then centrifuged for 40 minutes using an ultracentrifuge (55P-72) manufactured by Hitachi Koki Co., Ltd. The particles obtained are vacuum dried at 100 ° C. When the particles are measured by a scanning differential calorimeter and a melting peak corresponding to a polymer is observed, o-chlorophenol is added to the particles, and the mixture is heated and cooled, and then centrifuged again.
When the melting peak is no longer observed, the particles are regarded as precipitated particles. Two centrifugation operations are usually sufficient. (3) Intrinsic viscosity of polymer [η] (dl / g) 1 g of polymer is phenol / tetrachloroethane = 50
/ 50 (weight ratio) in 100 ml of a mixed solvent.
It was measured at 0 ° C. (4) Film Layer Thickness It was performed by observing the cross section of the film by a transmission electron microscope (TEM). That is, a small piece of the film sample was embedded in a resin in which a curing agent and an accelerator were mixed with an epoxy resin, and a section having a thickness of about 200 nm was prepared with an ultramicrotome to obtain a sample for observation. A micrograph of the cross section of the obtained sample was taken using a transmission electron microscope (H-9000) manufactured by Hitachi, Ltd., and the thickness of the surface layer was measured.
However, the acceleration voltage was set at 300 kV, and the magnification was set within the range of 10,000 to 100,000 times according to the surface layer thickness. 5 for thickness measurement
Perform 0 points and measure 10 points from the thicker one and 10 from the thinner one.
The points were deleted, and the average of 30 points was obtained and used as the measured value. (5) Film surface roughness Non-contact surface shape measurement system (Mic, manufactured by Micromap, using direct phase detection interferometry, so-called two-beam interferometry)
(rmap 512), the root mean square roughness (RM
S), average surface roughness (SRa), and maximum roughness (PV) were measured. The measurement wavelength was 554 nm, the objective lens was used at a magnification of 20 times, and 20 visual fields were measured. (6) Film Young's Modulus (GPa) Length (between chucks) 300 mm, width in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH using a tensile tester (model 2001) manufactured by Intesco Corporation. A 20 mm sample film was pulled at a strain rate of 10% / min, and was calculated by the following equation using the initial linear portion of the tensile stress-strain curve.

[0048]

E = Δσ / Δε (where E is Young's modulus (GPa), Δσ is stress difference (GPa) due to the original average cross-sectional area between two points on the straight line, Δε
Represents the difference in strain / initial length (-) between the above two points. (7) Abrasion Resistance Measured as follows using the apparatus shown in FIG. 1 of Japanese Patent Publication No. 7-81020. did. At a room temperature of 23 ° C. and a humidity of 50% RH, a film cut to a width of イ ン チ inch was brought into contact with a fixing rod at an angle θ = 135 °, and the film was cut at a rate of 1 minute.
At a speed of 0 m, the inlet tension is 400 g,
Run for 00m. After running, the amount of abrasion powder adhering to the fixed rod was visually evaluated.

At this time, when a 6 mm tape guide made of carbon black-containing polyacetal was used as a fixing rod, the surface was sufficiently finished by SUS420-J2 using Method A.
The method using the tape guide (surface roughness 0.2S) of ψ is referred to as method B. <Judgment of abrasion powder> ：: No adhesion is observed at all ○: Extremely slight adhesion is observed but practically no problem △: Slightly large amount of adhesion, problematic when used for a long time ×: Large amount of adhesion, practical use Difficult to perform (8) Slit properties After slitting the film by 10,000 m with a slit blade, the blade was observed with a microscope. Evaluation was made as follows according to the state of blade damage.

◎: Little damage is observed. ○: Damage is slightly recognized, but there is no problem in practical use. Δ: Damage is slightly large and causes a problem when used for a long time. ×: Slit is large and difficult to use in practical use. If not, the blades must be replaced frequently during film production. Further, the slit property is also evaluated by a dropout in the magnetic tape characteristics. That is, when the slit property is poor, dropout may increase. (9) Magnetic tape properties 200 parts of magnetic fine powder, 30 parts of polyurethane resin, 10 parts of nitrocellulose, 10 parts of vinyl chloride-cellulose acetate copolymer, 5 parts of lecithin, 100 parts of cyclohexane, 100 parts of methyl isobutyl ketone, and 300 parts of methyl ethyl ketone Part was mixed and dispersed in a ball mill for 48 hours, and 5 parts of a polyisocyanate compound was added to obtain a magnetic coating material, which was applied to the surface of the polyester A layer or, in the case of A / B / C lamination, to the surface of the C layer. Before being sufficiently dried and solidified, it was magnetically oriented and then dried to form a magnetic layer having a thickness of 1.8 μm.

Next, the coating film was calendered using a super calender composed of a mirror-finished metal roll and a polyester-based composite resin roll. Next, the tape after the calendar processing was
Slit to 2-inch width, BR6 manufactured by Victor Company of Japan, Ltd.
According to 400, the following magnetic tape characteristics were evaluated at normal speed. (A) Electromagnetic conversion characteristics (VTR head output) The initial VTR head output at a measurement frequency of 4 MHz was measured with a synchroscope, and compared with a reference tape (commercially available high-grade type video tape). An evaluation was performed.

A: Equivalent to the reference tape B: Slightly inferior to the reference tape C: Clearly inferior to the reference tape and unusable (B) Dropout Plays back a video tape on which a 4.4 MHz signal is recorded. The number of dropout counters (IDC2) of Okura Industry Co., Ltd. was measured for about 20 minutes, and a good one was A, and a bad one that was not practically usable was C, and an intermediate situation between A and C was B. (10) Scratch resistance A magnetic tape slit to a width of 1/2 inch is 6 mm in diameter.
The base film surface of the magnetic tape was rubbed once at a winding angle of 135 °, a running speed of 4 m / min, and a tension of 50 g around the hard chrome plated metal pin (finished 3S). Next, aluminum was vacuum-deposited on the rubbed surface so as to have a thickness of about 50 nm, the amount of scratches was visually observed, and the following judgment was made.

Rank 1: Extremely large amount of scratches Rank 2: Large amount of scratches Rank 3: Intermediate between 2 and 4 scratches Rank 4: Low amount of scratches Rank 5: No scratching (11) Runnability The video tape was run for 120 minutes using a commercially available VTR system VTR with the unwinding side back tension set to zero. The running state of the video tape was observed with the pin immediately before the head cylinder, and the following judgment was made.

A: The deviation of the running position of the running tape is less than 0.5 mm from the specified position. B: The deviation of the running position of the running tape is 0.5 mm or more and less than 2 mm from the specified position. The running position deviates from the specified position by 2 mm or more Examples 1-4 and Comparative Examples 1-7 [Production of Polyester A] Dimethyl Terephthalate 10
0 parts, 70 parts of ethylene glycol and 0.11 part of calcium acetate monohydrate were placed in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction. The transesterification reaction was substantially completed.

Next, 0.124 parts of triethyl phosphite and 0.54 parts of triethyl phosphite were added to the reaction compound.
And a solution in which ethylene glycol is uniformly dissolved in ethylene glycol, and then 0.04 part of antimony trioxide.
It took 10 minutes to reach 236 ° C. From this point, the pressure in the system was gradually reduced, and after the addition of antimony trioxide, 80
The temperature in the system was set to 265 ° C. and the pressure was set to 300 mmHg in minutes.
Hg or less, and after 4 hours, a polyester A having an intrinsic viscosity of 0.63 was obtained.

A large number of uniform and fine precipitated particles were observed in the obtained polyester, and the particle size was 1.2 μm. When the amount of the precipitated particles was measured according to the method described in the text, it was 0.4% by weight with respect to the polyester. [Production of polyester B] dimethyl terephthalate 10
0 part, 70 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, and methanol was distilled off. It took about 4 hours from the start of the reaction to reach 230 ° C., and transesterification was carried out. The reaction was completed. Then, after adding 1.0 part of calcium carbonate particles having a particle size of 0.4 μm as an ethylene glycol slurry, 0.06 part of phosphoric acid and 0.04 part of antimony trioxide were further added, and the reaction system was gradually reduced in pressure. The polycondensation reaction was performed at an elevated temperature to obtain a polyester B having an intrinsic viscosity of 0.62 after 4 hours. [Production of Polyester C] Instead of the calcium carbonate particles used in Polyester B, 1.5 δ-alumina particles having a primary particle size of 0.02 μm, which had been crushed, classified and filtered in advance, were used.
A polyester C having an intrinsic viscosity of 0.62 was obtained by carrying out a transesterification reaction and a polycondensation reaction in the same manner as in the case of polyester B, except that part of the mixture was added as an ethylene glycol slurry. [Production of Polyester D] A transesterification reaction and a polycondensation reaction were carried out in the same manner as described above except that no particles were added, to obtain a polyester D having a limiting viscosity of 0.67 substantially containing no inert particles. [Production of Polyester E] Average particle size 0.6 μm as particles
A transesterification reaction and a polycondensation reaction were carried out in the same manner as above, except that 0.8 parts of calcium carbonate particles of m were added as an ethylene glycol slurry, to obtain a polyester E having an intrinsic viscosity of 0.62. [Production of Polyester F] A transesterification reaction and a polycondensation reaction were carried out in the same manner as described above except that no particles were added, to obtain a polyester F having an intrinsic viscosity of 0.59 substantially containing no inert particles. [Production of polyester film] The obtained polyesters A, B, C, D and E were blended so as to have the particle contents shown in Table 1, and were melt-extruded by a melt extruder.
A laminated amorphous sheet was obtained. In the layer B, 30% of a recycled material was blended with polyester F and extruded.

Next, the amorphous sheet is stretched 2.4 times at 83 ° C. in the film flow direction (longitudinal direction) and 1.30 times at 83 ° C. in the machine direction, and 4.4 times at 115 ° C. in the transverse direction. Stretched twice, heat-treated at 210 ° C. for 4 seconds,
The film was relaxed in the transverse direction at 3 ° C. by 3% to obtain a biaxially oriented laminated film. The total thickness of the film was 15 μm, and the thickness of each layer was as summarized in Table 1.

Example 5 With the raw material and layer thickness configuration of Example 1, the stretching ratio in the second stage in the longitudinal direction was 1.35 times, and the stretching ratio in the transverse direction was 4.1 times. A film was prepared in the same manner as in Example 2. Comparative Examples 6 and 7 In Example 2, except that the stretching ratio in the longitudinal direction and the stretching ratio in the lateral direction were changed so that the ratio of the Young's modulus in the transverse direction to the Young's modulus in the longitudinal direction was out of the range of the present invention. Example 2
In the same manner as in the above, a biaxially stretched laminated polyester film was obtained.

A magnetic layer was applied to the films obtained in Examples and Comparative Examples to obtain a magnetic tape, and the characteristics were evaluated. Tables 1 to 3 below show respective film characteristics and evaluation results of the magnetic tape.

[0060]

[Table 1]

[0061]

[Table 2]

[0062]

[Table 3]

[0063]

[Table 4]

[0064]

[Table 5] The films of Examples 1 to 5 satisfying the requirements of the present invention have excellent running properties, abrasion resistance, and abrasion resistance, and are at a level that is highly satisfactory in magnetic tape properties.

On the other hand, the films of Comparative Examples 1 to 7 are examples of films which do not satisfy the requirements of the present invention, but are inferior in abrasion resistance, scratch resistance and magnetic tape characteristics.

[0066]

As described in detail above, the film of the present invention has excellent slitting properties at the time of film production and magnetic recording medium production as a base film for a magnetic recording medium,
It is highly satisfactory in running properties and electromagnetic conversion characteristics as a magnetic recording medium, is excellent in preventing dropout, has very few scratches and abrasion powder, and is excellent in productivity and cost. , Its industrial value is very large.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C08L 67/00 C08L 67/00 F term (reference) 4F071 AA43 AF20Y AH14 BB08 BC01 BC10 BC16 4F100 AA04A AA04C AA04H AA08H AA19H AK41A AK41B AK41C BA02 BA03 BA06 BA13 BA25 CA23A CA23C DD07A DD07C DE01A DE01C DE01H EJ38 GB41 JG10 JK07 JK09 JK12A JK12C JK12H JK15 JL00 YY00 YY00A YY00C YY00H 4J002 CF04 006 006 001 001

Claims (3)

[Claims] Claims: 1. A polyester production reaction system,
Average particle size containing calcium and phosphorus is 0.7-
0.01 to 0.1% by weight of precipitated particles having a size of 1.5 μm,
0.1 to 1.0% by weight of inert fine particles having an average particle size of 0.1 to 1.0 μm and an average primary particle size of 0.3 μm
m is a biaxially oriented polyester film obtained by laminating a polyester A layer containing 0.01 to 1.0% by weight of inert fine particles having an Mohs hardness of 7 or more on a polyester B layer; A polyester film for a magnetic recording medium, which simultaneously satisfies 1) to 4). (Equation 1) 0.010 ≦ RMS ≦ 0.025 (2) 0.005 ≦ SRa ≦ 0.020 (3) 0.200 ≦ PV ≦ 0.350 (4) (where Y _MD is a film Young's modulus in the vertical direction (GP
a), Y _TD is the Young's modulus (GPa) in the transverse direction of the film,
RMS is the root mean square roughness (μm) of the polyester A layer surface, SRa is the average surface roughness (μm) of the polyester A layer surface, and PV is the maximum roughness (μm) of the polyester A layer surface. 2. The method according to claim 1, wherein the precipitated particles are particles formed by allowing a trialkyl phosphite and a trialkyl phosphate to act on a calcium compound soluble in the reaction system in the polyester production reaction system. 2. The polyester film for a magnetic recording medium according to 1. 3. A film having an A / B / C structure in which a C layer made of a polyester composition constituting a polyester A layer is laminated on a polyester B layer, wherein the thickness of the C layer is the thickness of the A layer. 0.1 to 0.8 times, and the difference between the average surface roughness of the A layer surface and the average surface roughness of the C layer surface is 1 to 10 nm.
The polyester film for a magnetic recording medium according to claim 1 or 2, wherein