JPH11216824A - Polyester film for magnetic recording media - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To be useful as a base of a magnetic recording medium having excellent abrasion resistance, winding property and blocking resistance in a film forming process, and also excellent in electromagnetic conversion characteristics, dropout characteristics and running durability. To provide a perfect polyester film. SOLUTION: A film layer A is formed on one side of a polyester film (layer C) comprising a single layer or two or more layers,
The coating layer A includes inert particles having an average particle diameter of 10 to 100 nm, and a resin as a binder.
1 × 10 ⁶ to 1 × 10 ⁸ protrusions Aa of 0 nm / mm ²
Having an average projection height of only 2
1 × 10 ^{6 to} 3 × 10 ⁸ microprojections Ab of 15 nm /
a film made of a continuous film having a frequency of mm ^2, micro surface roughness Ra ^S only by the continuous film of resin in said coating layer A is 0.4～2.0Nm, and the said coating layer A The surface roughness Ra ^A of the formed surface is 0.3 to 2 nm,
When the layer C is a single layer, it contains substantially no inert particles, and when it has two or more layers, the layer on which the coating layer A is formed contains no inert particles. Polyester film for media.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a magnetic recording medium, and more particularly, to a film having excellent abrasion resistance, winding property and blocking resistance in a film forming process, as well as electromagnetic conversion characteristics, dropout characteristics and running. The present invention relates to a polyester film useful as a base for a magnetic recording medium having excellent durability.

[0002]

2. Description of the Related Art As a high-density magnetic recording medium, a ferromagnetic metal thin film magnetic recording medium in which a ferromagnetic metal thin film is formed on a nonmagnetic support by a physical deposition method such as vacuum evaporation or sputtering or a plating method is known. . For example, a magnetic tape on which Co is deposited (Japanese Patent Laid-Open No. 54-147010), Co-
Perpendicular magnetic recording media using a Cr alloy
No. 4706) is known. The metal thin film formed by such thin film forming means as vapor deposition, sputtering or ion plating has a very small thickness of 1.5 μm or less, and in spite of that, the thickness of the magnetic recording layer is 3 μm or more. There is an advantage that performance equal to or higher than that of a magnetic recording medium (a magnetic recording medium obtained by mixing a magnetic substance powder into an organic polymer binder and coating it on a nonmagnetic support) can be obtained.

[0003] By the way, it is considered that the magnetic characteristics such as the coercive force Hc or the squareness ratio of the hysteresis loop, which are the static characteristics of the magnetic recording medium, do not depend much on the surface condition of the non-magnetic support used. As an example based on this idea, U.S. Pat. No. 3,787,327 discloses a multilayer structure of Co--Cr by vacuum evaporation.

However, in a metal thin-film type magnetic recording medium, the thickness of the metal thin film formed on the surface of the non-magnetic support is small, and the surface condition (surface unevenness) of the non-magnetic support is not changed on the surface of the magnetic recording layer. As a drawback that it causes noise.

[0005] From the viewpoint of noise, it is preferable that the surface state of the nonmagnetic support is as smooth as possible. On the other hand, from the viewpoint of handling such as winding and unwinding of the base film, if the film surface is smooth, the sliding property between the film and the film is poor, and a blocking phenomenon occurs.
It cannot be a product and therefore requires a rough base film surface. As described above, the surface of the non-magnetic support is required to be smooth from the viewpoint of electromagnetic conversion characteristics, and is required to be rough from the viewpoint of handling properties. Therefore, it is necessary to simultaneously satisfy these two conflicting properties.

Further, a serious problem of the metal thin film magnetic recording medium when it is actually used is the running property of the metal thin film surface. In the case of a coating type magnetic recording medium in which a conventional magnetic powder is mixed with an organic polymer binder and applied to a base film, a lubricant is dispersed in the binder to improve the runnability of the magnetic surface. However, in the case of a metal thin-film magnetic recording medium, such measures cannot be taken, and it is very difficult to maintain a stable running property.
In particular, it has disadvantages such as poor running performance at high temperature and high humidity.

For the purpose of improving this drawback, Japanese Patent Publication No. Sho 62
Japanese Patent No. 30105 proposes forming fine projections on the film surface using fine particles, a water-soluble resin and a silane coupling agent. In addition, Japanese Patent Publication 62-30
No. 106 and JP-A-59-229316 propose to form fine projections on the film surface using fine particles and a water-soluble resin. However, all of them have fine particles present in the trapezoidal protrusions of the water-soluble resin, and do not have fine particles uniformly present on the film surface. Japanese Patent Publication No. 34456/1989 proposes that a discontinuous film of a water-soluble polymer and fine particles forming higher projections are independently adhered to the film surface. However, this is inferior in uniformity on the film surface because the projections are discontinuous films and are due to fine particles that are not uniformly dispersed.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art, to provide excellent abrasion resistance, winding property and blocking resistance in the film forming process, and to obtain electromagnetic conversion characteristics and dropout characteristics. Another object of the present invention is to provide a polyester film useful as a base for a magnetic recording medium having excellent running durability.

[0009]

The present invention has the following arrangement to attain the object. A film layer A is formed on one surface of a polyester film (layer C) composed of a single layer or two or more layers, and the film layer A has an average particle size of 10 to 10.
The protrusions Aa having an average protrusion height of 15 to 100 nm are formed of 1 × 10 ⁶ to
1 × 10 ⁸ fine protrusions Ab having a frequency of 1 × 10 ⁸ / mm ² and an average protrusion height of 2 to 15 nm made of only the resin are 1 × 1
0 ⁶ a film made from a continuous thin film having at a frequency of to 3 × 10 ⁸ pieces / mm ^2, very small surface roughness Ra ^S only by the continuous film of resin in said coating layer A is 0.4~2.0nm , and the and the surface roughness Ra ^a of the surface forming the said coating layer a is 0.3～2Nm, and said layer C is in the case of single-layer substantially free of inert particles and two layers In the above case, the layer on which the coating layer A is formed does not contain inert particles.

The present invention is described in detail below. The polyester constituting the film of the present invention is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Preferred specific examples of such polyesters include:
Polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly (1,
Examples thereof include 4-cyclohexylene dimethylene terephthalate), polyethylene-2,6-naphthalenedicarboxylate, and the like, and also include copolymers thereof and blends thereof with a small proportion of other resins.

[0011] Such a polyester can be produced by a conventionally known method. For example, polyethylene terephthalate can be produced by an esterification reaction of terephthalic acid and ethylene glycol or a transesterification reaction of dimethyl terephthalate and ethylene glycol, followed by polycondensation of the reaction product.

In the present invention, the polyester film of the layer C needs to contain substantially no inert particles when it is a single layer, and forms the coating layer A when it is a laminated film of two or more layers. It is necessary that the side layers do not contain inert particles.

[0013] Here, "contains substantially no particles"
It does not contain externally added particles or internally precipitated particles that form protrusions on the film surface, but contains extremely small amounts of particles that do not substantially exhibit a lubricant effect, which may be caused by, for example, a catalyst required for polymerization of polyester. Means that you can do it. For example, except for particles that form surface projections, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, and an antistatic agent can be contained as needed.

In the present invention, as a resin (binder) for forming the coating layer A and binding the inert particles to the polyester film surface, alkyd resin, unsaturated polyester resin, saturated polyester resin, phenol resin, epoxy resin, Examples thereof include amino resins, polyurethane resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymer resins, acrylic resins, and acrylic-polyester resins. These resins may be a homopolymer, a copolymer, or a mixture.

The acrylic resin includes, for example, acrylic acid esters (alcohol residues such as methyl, ethyl, n-propyl, isopropyl, n-butyl,
Isobutyl group, t-butyl group, 2-ethylhexyl group,
Examples thereof include a cyclohexyl group, a phenyl group, a benzyl group and a phenylethyl group); methacrylic acid esters (alcohol residues are the same as described above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
Hydroxy-containing monomers such as -hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-dimethylol Amide group-containing monomers such as acrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-phenylacrylamide; amino group-containing monomers such as N, N-diethylaminoethyl acrylate and N, N-diethylaminoethyl methacrylate; Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; styrene sulfonic acid, vinyl sulfo Monomers containing sulfonic acid groups or salts thereof, such as acids and salts thereof (eg, sodium salts, potassium salts, ammonium salts, etc.); crotonic acid, itaconic acid, acrylic acid, maleic acid, fumaric acid, and Monomers containing a carboxyl group or a salt thereof such as a salt (eg, sodium salt, potassium salt, ammonium salt, etc.); monomers containing an anhydride such as maleic anhydride or itaconic anhydride; other vinyl isocyanate, allyl isocyanate, styrene , Vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester,
Alkyl fumaric acid monoester, acrylonitrile,
(Meth) acrylic monomers such as acrylic acid derivatives and methacrylic acid derivatives, which are made from a combination of monomers such as methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, vinyl acetate and vinyl chloride Is preferably contained in an amount of 50 mol% or more, particularly preferably a component containing a methyl methacrylate component.

The acrylic resin can be self-crosslinked by a functional group in the molecule, or can be crosslinked by using a crosslinking agent such as a melamine resin or an epoxy compound.

The acid component constituting the polyester resin is, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-
Naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2
—Polyvalent carboxylic acids such as potassium sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, and monopotassium trimellitic acid salt. Examples of the hydroxy compound component include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol,
-Xylylene glycol, ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, dimethylolpropionic acid Examples include polyvalent hydroxy compounds such as potassium. A polyester resin can be prepared from these compounds by a conventional method. When making an aqueous coating liquid, 5
-It is preferable to use a polyester resin containing a sodium sulfoisophthalic acid component or a carboxylate group.
Such a polyester resin can be a self-crosslinking type having a functional group in the molecule, or can be crosslinked using a curing agent such as a melamine resin or an epoxy resin.

Further, the acryl-polyester resin is used to mean an acryl-modified polyester resin and a polyester-modified acryl resin. The acryl-polyester resin is composed of an acrylic resin component and a polyester resin component bonded to each other. Type, block type, etc. Acrylic-polyester resin, for example, adds a radical initiator to both ends of the polyester resin to polymerize the acrylic monomer, or attaches a radical initiator to the side chain of the polyester resin to polymerize the acrylic monomer. Alternatively, it can be produced by attaching a hydroxyl group to the side chain of the acrylic resin and reacting it with a polyester having an isocyanate group or a carboxyl group at a terminal to obtain a comb polymer.

In the present invention, the material of the inert particles A blended in the film layer A includes polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, methyl methacrylate copolymer crosslinked product, polytetrafluoroethylene. Organic matter such as polyvinylidene fluoride, polyacrylonitrile, benzoguanamine resin, silica, alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, inorganic matter such as molybdenum disulfide, carbon black, barium sulfate. May be used.

Further, core-shell type particles having a multilayer structure composed of substances having different properties inside and outside may be used.

The average particle size of the inert particles A is 10 to 10
0 nm, preferably 10 to 50 nm. Further, those having a uniform particle size distribution are preferred. The average protrusion height of the protrusion Aa having the inert particle A as a nucleus and the resin as a binder is 1
It is 5 to 100 nm, preferably 20 to 60 nm. If the average particle size is smaller than 10 nm or the projection height is lower than 15 nm, the slipperiness of the film deteriorates, and the running durability of a magnetic tape becomes insufficient. On the other hand, if the average particle size is larger than 100 nm or the average protrusion height is higher than 100 nm, the particles will fall off,
The abrasion resistance deteriorates. Further, when the scraped particles adhere to and deposit on the film to form a magnetic tape, dropouts are increased. In addition, the spacing with the magnetic head is increased, making it difficult to provide a high-density magnetic recording medium.

The frequency of surface protrusions of the protrusions Aa in the coating layer A is 1
× 10 ⁶ to 1 × 10 ⁸ pieces / mm ² . If the frequency of the surface projections is less than 1 × 10 ⁶ / mm ² , the running durability of a magnetic recording medium is insufficient. On the other hand, 1 × 10 ⁸ /
If it exceeds mm ² , the electromagnetic conversion characteristics will be adversely affected. The preferred frequency of surface projections is 2 × 10 ^{6 to} 5 × 10 ⁷ / m
m ² , more preferably 3.0 × 10 ^{6 to} 3.0 × 10 ⁷
Pieces / mm ² .

The coating layer A has fine projections Ab made of only the resin (binder), and the average projection height is 2 to 2.
15 nm, preferably 2 to 10 nm, and the frequency is 1 × 10 ⁶ to 1 × 10 ⁸ / mm ² , preferably 5 × 1
0 ⁶ ~1 × 10 ⁸ cells is / mm ^2. Further, the minute surface roughness Ra ^S of the continuous thin film portion of the coating layer A made of only the resin is 0.1.
It is 4 to 2.0 nm, preferably 0.5 to 1.5 nm. The average projection height of the minute projections Ab is smaller than 2 nm;
Or the frequency is less than 1 × 10 ⁶ pieces / mm ² ,
Alternatively micro surface roughness Ra ^S is when drops below 0.4nm, the blocking phenomenon occurs in the case of winding the film into a roll. Further, the average projection height of the micro projections Ab is larger than 15 nm, or the frequency is 3 × 10 ⁸
If the surface roughness exceeds Ra / mm ² , or if the fine surface roughness Ra ^S is greater than 2.0 nm, the coercive force of the magnetic recording medium decreases, which adversely affects the electromagnetic conversion characteristics.

Ra ^A of the surface on which the coating layer A is formed is 0.3 to
2 nm, and preferably 0.5 to 1.5 nm.
If the Ra ^A is less than 0.3 nm, the slipperiness of the film deteriorates, and the running durability of a magnetic tape becomes insufficient. On the other hand, if it exceeds 2 nm, the electromagnetic conversion characteristics deteriorate.

As a method for forming the coating layer A on the polyester film surface, a resin coating liquid in which the inert particles Aa and the thin film forming resin and, if necessary, the inert particles Ac are further dispersed uniformly, preferably an aqueous A method in which an emulsion or suspension coating liquid is applied to the film surface during the polyester film manufacturing process and dried and solidified (in-line method), or a method in which the coating liquid is applied to a biaxially oriented polyester film and dried and solidified (off-line method) And the like, but the former in-line method is preferred. Inclusion of a surfactant for facilitating application in these coating solutions is inevitable.

In the above method, the microprojections Aa having an inert Aa as a nucleus and the large projections Aa formed by inert particles Ac
At the same time as the formation of c, minute projections made of only the thin film forming resin are formed. The drying and solidification after the application of the coating liquid on the film surface is performed under the condition that the resin forms a continuous thin film and a part of the resin forms minute projections. At this time, although it depends on the thermal characteristics of the resin, it is desirable to appropriately select the size of the emulsion or suspended resin in the coating liquid, the drying temperature, the time, and the like. These can be easily understood from the examples described later. More specifically, for example, the size of the resin fine particles in the coating liquid preferably has an average particle diameter of 25 to 100 nm as measured by a light scattering method. The resin fine particles having such an average particle size can be obtained by a usual method for preparing an emulsion or suspension, and can also be obtained from the market.

In the present invention, it is preferable to provide a film layer B made of a continuous thin film on the other surface on which the film layer A of the layer C is formed in order to impart the film winding property.

The coating layer B contains inert particles B. Examples of the inert particles B include polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, and polytetramethyl methacrylate. Organic particles such as fluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoquanamine resin, silica, alumina, titanium dioxide, kaolin, talc, graphite,
Any of inorganic particles such as calcium carbonate, feldspar, molybdenum disulfide, carbon black, and barium sulfate may be used. Further, it may be a shell core type particle.

Inert particles B contained in the coating layer B
Has an average particle size of 10 to 200 nm, preferably 20 to 1 nm.
00 nm. The content of the inert particles B in the coating layer B is 3 to 50% by weight, preferably 5 to 30% by weight. If the average particle diameter of the particles B is less than 10 nm or the content is less than 3% by weight, the film is not satisfactory in terms of film winding properties, transportability in a film forming process, and the like, and tends to cause blocking. . On the other hand, when the average particle size exceeds 200 nm, the particles easily fall off the coating film. When the content of the inert particles B in the coating layer B exceeds 50% by weight, the strength of the coating layer B itself is reduced and the coating layer B is easily chipped.

As the resin containing the inert particles B to form the coating layer, the same resins as those exemplified for the coating layer A can be exemplified. Further, these may further contain a cellulosic resin.

If necessary, other components such as a surfactant, a stabilizer, a dispersant, a UV absorber and a thickener may be added to the film layer B as long as the effects of the present invention are not impaired. can do.

Ra ^B on the surface on which the coating layer B was formed was 1
３０30 nm, preferably 2-20 nm. When Ra ^B is less than 1 nm, the film winding property and the transport property in the film forming process are insufficient, and blocking tends to occur. On the other hand, when Ra ^B exceeds 30 nm, there is a problem that the coating layer B is easily scraped.

The layer C of the present invention can be produced by a conventionally known method.

For example, in the case of a biaxially oriented polyester film, when the core layer is a single layer, the polyester is first extruded from a die into a film at a melting point of Tm ° C to (Tm + 70) ° C, and then extruded at 40 to 90 ° C. Rapidly solidifies to obtain an unstretched film. Thereafter, the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) to
The film is stretched at a temperature of (Tg + 70) ° C. (Tg: glass transition temperature of polyester) at a magnification of 2.5 to 8.0 times, preferably 3.0 to 7.5 times, and then a coating layer A , B are applied to both sides of the film, and then Tg to (Tg +
70) The film is stretched at a temperature of ° C at a magnification of 2.5 to 8.0 times, preferably at a magnification of 3.0 to 7.5 times. Further, if necessary, the film may be stretched again in the machine direction and / or the cross direction. That is, stretching in two, three, four, or more stages may be performed. The total stretching ratio is usually 9 as an area stretching ratio.
Times or more, preferably 12 to 35 times, more preferably 15 times.
Up to 32 times. Subsequently, the biaxially oriented film is heated to a temperature of (Tg + 70) to (Tm−10) ° C., for example, 18 ° C.
Excellent dimensional stability is provided by heat set crystallization at 0-250 ° C. The heat setting time is preferably 1 to 60 seconds.

In the case of the coextrusion method, two kinds of polyesters are laminated and compounded in a molten state in or before the extrusion die (generally, the former is referred to as a multi-manifold type, and the latter is referred to as a feed block type). Then, co-extrusion is performed to form a two-layer unstretched film, and thereafter, the same process as in the single-layer method is performed.

In the production of the polyester film, additives such as a stabilizer, a coloring agent, and an agent for controlling the resistivity of the molten polymer (antistatic agent) can be added to the polyester, if desired.

The polyester film for a magnetic recording medium of the present invention can be formed on the surface of the coating layer A by iron, cobalt, chromium or an alloy or oxide containing these as main components by a method such as vacuum deposition, sputtering, or ion plating. A ferromagnetic metal thin film layer is formed, and a protective layer such as diamond-like carbon (DLC) and a fluorinated carboxylic acid-based lubricating layer are sequentially provided on the surface of the ferromagnetic metal thin film layer if necessary. By providing a well-known back coat layer on the surface of the, especially in the short wavelength region, the S /
Excellent electromagnetic conversion characteristics such as N, C / N, dropout,
A vapor-deposited magnetic recording medium for high-density recording with a low error rate can be obtained. This vapor-deposited electromagnetic recording medium can be used as a Hi8 for analog signal recording, a digital video cassette recorder (DVC) for digital signal recording, a 8 mm data, and a tape medium for DDSIV, and is extremely useful.

In the polyester film for a magnetic recording medium of the present invention, iron or fine needle-like magnetic powder mainly composed of iron is coated on the surface of the coating layer A with polyvinyl chloride, vinyl chloride / vinyl acetate copolymer or the like. Uniformly dispersed in a binder of
By coating the magnetic layer so as to have a thickness of 1 μm or less, preferably 0.1 to 1 μm, and further providing a back coat layer on the surface of the coating layer B by a known method, the output in a short wavelength region, S / S A metal-coated magnetic recording medium for high-density recording with excellent electromagnetic conversion characteristics such as N and C / N and low dropout and error rate can be obtained. If necessary, a non-magnetic layer containing fine titanium oxide particles or the like may be dispersed and coated on the coating layer A in the same organic binder as the magnetic layer as a base layer of the metal powder-containing magnetic layer. Can also. This metal-coated magnetic recording medium is an 8 mm video for analog signal recording, Hi8, β cam SP, W-VH
It is very useful as a tape medium for S, digital video cassette coder (DVC) for recording digital signals, data 8 mm, DDSIV, digital β cam, D2, D3, SX, etc.

The polyester film for a magnetic recording medium of the present invention is also characterized in that a needle-like fine magnetic powder such as iron oxide or chromium oxide or a plate-like fine magnetic powder such as barium ferrite is coated on the surface of the coating layer A with polyvinyl chloride. , A uniform dispersion in a binder such as a vinyl chloride / vinyl acetate copolymer or the like, and coating so that the thickness of the magnetic layer is 1 μm or less, preferably 0.1 to 1 μm. By providing the coating layer, it is possible to obtain a coating type magnetic recording medium for high-density recording which is particularly excellent in output in a short wavelength region, electromagnetic conversion characteristics such as S / N, C / N and the like, and has little dropout and error rate. I can do it. If necessary, a nonmagnetic layer containing fine titanium oxide particles and the like is dispersed and coated on the coating layer A in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. You can do it. This oxide-coated magnetic recording medium is useful as a high-density oxide-coated magnetic recording medium such as a data streamer QIC for digital signal recording.

[0040]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In addition, "part" in an example is a weight part. The measuring method used in the present invention is as follows.

(1) Average particle size of particles (average particle size: 0.0
6μm or more) Shimadzu CP-50 Centrifugal Particle Size Analyzer (Centrifugal Particle)
It is measured using a Size Analyzer). From the integrated curve of particles of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, the particle size “equivalent sphere diameter” corresponding to 50 mass percent is read, and this value is defined as the above average particle size. (See "Granularity measurement technology" published by Nikkan Kogyo Shimbun, 1975, pp. 242 to 247).

(2) Average particle size of ultrafine particles (average particle size:
The particles having an average particle size of less than 0.06 μm that form small projections are:
It is measured using a light scattering method. That is, Nicom Instruments Inc. (NicompInst)
devices Inc. NICOMP MO manufactured by
DEL 270 SUBMICRON PARTICL
50% by weight of all particles as determined by E Sizer
At the point indicated by "Equivalent spherical diameter".

(3) Layer Thickness The total thickness of the film is randomly 10 micrometer.
Measure the points and use the average value. The layer thickness is obtained by measuring the layer thickness on the thinner side by the method described below, and subtracting the layer thickness on the thicker side from the layer thickness on the thinner side than the total thickness. That is, using a secondary ion mass spectrometer (SIMS), a concentration ratio (M ⁺ /) of an element originating from the highest concentration particle among the particles in the film having a depth of 5000 nm from the surface layer to the carbon element of the polyester. C ⁺ ) is defined as the particle concentration and the depth from the surface is 500
Analysis in the thickness direction is performed up to 0 nm. In the surface layer, the particle concentration is naturally low, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, there are cases where the particle concentration once reaches a stable value 1 and then increases or decreases to a stable value 2 and cases where the particle concentration monotonously decreases. Based on this distribution curve, the former has a depth giving a particle concentration of (stable value 1 + stable value 2) / 2, and the latter has a depth at which the particle concentration becomes 1/2 of the stable value 1. (This depth is deeper than the depth that gives a stable value of 1), which is the layer thickness of the layer.

Secondary ion mass spectrometer (SIMS): P
The measurement conditions of 6300 manufactured by ERKIN ELMER are as follows. Primary ion species: O2 + Primary ion acceleration voltage: 12 KV Primary ion current: 200 mA Raster region: 400 μm □ Analysis region: Gate 30% Measurement vacuum degree: 6.0 × 10 ⁻⁹ Torr E-GUNN: 0.5 KV-3.0 A In addition, when the particles contained most in the range of 5000 nm from the surface layer are organic polymer particles other than the silicone resin, SI
Since measurement is difficult with MS, the same concentration distribution curve as above is measured by FT-IR (Fourier transform infrared spectroscopy) while etching from the surface, or XPS (X-ray high electron spectroscopy) depending on the particles, and the layer is measured. Find the thickness.

The above is an effective measurement method for a co-extruded layer. In the case of a coated layer, a small piece of a film is fixedly formed with an epoxy resin, and an ultra-thin section (thickness of the film) of about 60 nm is formed with a microtome. The sample is cut parallel to the flow direction), and this sample is taken with a transmission electron microscope (H-8, manufactured by Hitachi, Ltd.).
(Type 00), and the layer thickness is determined from the boundary surface of the layers.

(4) Surface Roughness of Film (Center Line Average Roughness: Ra) The center line average roughness (Ra) is measured according to JIS-B601. In the present invention, it is measured and measured under the following conditions using a stylus type surface roughness meter (SURFCORDER SE, 30C) manufactured by Kosaka Laboratory Co., Ltd. (A) Probe tip radius: 2 μm (b) Measurement pressure: 30 mg (c) Cut-off: 0.08 mm (d) Measurement length: 8.0 mm (e) How to summarize data: Repeatedly measure the same sample six times The center line average roughness (Ra) is determined as an average using the remaining five data except for the largest value.

(5) Frequency of protrusions Aa and Ab Atomic force microscope Nano Scop manufactured by Digital Instruments
eIII, using an AFM J-scanner under the following conditions:
Measurement is performed at 10 locations in a range of μm × 2 μm, the number of each projection is counted from the AFM image, and the average value is calculated as the number of projections per piece / mm ² by area conversion. Scanning mode; Tapping mode Surface prime number: 256 × 256 Data points Scanning speed: 2.0 Hz Measurement environment: Room temperature, in air

(6) Average height of projections Aa, Ab 100 projections are randomly selected from the above-mentioned AFM image, the height of each projection is measured, and the average value is used as the average height of the projections. I do.

(7) Micro surface roughness Ra ^{S A} portion having no protrusions Aa having inactive particles as nuclei is selected from the above-mentioned 2 μm × 2 μm AFM image and measured from the film surface roughness curve in the direction of the center line thereof. When a portion having a length L is extracted and the center line of the extracted portion is set as the X axis and the direction of the vertical magnification is set as the Y axis, the roughness curve is represented by Y = f (x).
The value given by the following equation is expressed in nm.

[0050]

(Equation 1)

In practice, this measurement was performed at five locations for a single AFM image with a length of 0.4 to 1.2 μm, and the average value of a total of 50 locations of the ten AFM images was used as the fine surface. the roughness Ra ^S.

(8) Abrasion resistance The film was sampled at a length of 25 to 30 cm and a width of 1/2 inch, and the leather blade was applied under the conditions of an angle of 90 ° with respect to the surface of the coating layer B and a depth of 0.5 mm. , Load 500g /
The width in the depth direction of the shaving powder adhering to the razor blade when running at a speed of 0.5 cm and a speed of 6.7 cm / sec was determined by taking a microphotograph (× 160). If the width of the shavings in the depth direction is less than 3 μm (○), 3 to 5 μm (△), 5
A value exceeding μm is represented by (x). The smaller the width of the shaving powder in the depth direction, the better the shaving properties.

(9) Blocking The surfaces of the two films on which the film layer A was formed and the film layer B were superimposed, and a pressure of 150 kg / cm ² was applied thereto at 60 ° C. in an atmosphere of 80% RH for 65 hours. Peel off,
Evaluation is based on the peeling force (g per 5 cm). In addition,
The evaluation is performed based on the following criteria based on the peeling force. ：: 0 to less than 10 g / cm Δ: 10 g / cm or less to less than 15 g / cm ×: 15 g / cm or more to tear

(10) Winding property After optimizing the winding conditions at the time of slitting, a roll having a size of 560 mm in width and 9000 m in length was slit into 10 rolls, and a roll free of film wrinkles after being left for one week. Using the book as a good product, the winding property is evaluated based on the following criteria. Number of good rolls Judgment criteria 8 or more ○ 3 to 7 △ 2 or less ×

(11) Manufacture of magnetic tape and evaluation of properties On the surface of the film layer A of the laminated film, a vacuum evaporation method was used.
A ferromagnetic thin film of 100% cobalt is formed in two layers (each layer thickness is about 0.1 μm) so as to have a thickness of 0.02 μm, and a diamond-like carbon (DLC) film and a fluorine-containing carboxylic acid-based lubricating layer are formed on the surface. A back coat layer is provided on the surface of the layer C or the coating layer B by a known method. Then, it is slit into an 8 mm width and loaded on a commercially available 8 mm video cassette. Next, the properties of the tape are measured using the following commercially available equipment.

Measurement of Coercive Force Hc The hysteresis loop is measured by the method shown in JIS C-2561 to determine the coercive force Hc. A sample vibration magnetometer (BHV-30 manufactured by Riken Denshi Co., Ltd.) is used for the measurement. ；: More than 1300 Oe △; 1000 to 1300 Oe ×; less than 1000 Oe

C / N Measurement A signal having a recording wavelength of 0.5 μm (frequency about 7.4 MHz) was recorded, and the ratio of the value of the reproduced signal between 6.4 MHz and 7.4 MHz was defined as the C / N of the tape. The C / N of the 8 mm video evaporation tape is represented by OdB and expressed as a relative value. Equipment used: 8mm video tape recorder: EDV manufactured by Sony Corporation
-6000 C / N measurement: Noise meter manufactured by Shibasoku Co., Ltd. ○: more than 2 dB ×; -2 to 2 dB ×; less than -2 dB

Dropout (D / O) measurement Using a dropout counter, 15 μs / 18 d
The number per minute is measured in B. ：: less than 0 to 20 (pieces / minute) △: 20 to 40 (pieces / minute) ×: more than 40 (pieces / minute)

Running Durability C / N was measured after recording and reproducing 500 times at 40 ° C., 80% RH and a tape at a running speed of 85 cm / min.
The deviation from the initial value is determined based on the following criteria. ：: more than +0.0 dB with respect to the initial value Δ: −1.0 dB to +0.0 dB with respect to the initial value ×: less than −1.0 dB with respect to the initial value

Example 1 Dimethyl terephthalate and ethylene glycol were added, manganese acetate was added as a transesterification catalyst, antimony trioxide was added as a polymerization catalyst, and phosphorous acid was added as a stabilizer. Polyethylene terephthalate (P) containing no inert particles
ET).

The polyethylene terephthalate was converted to 170
After drying at 3 ° C. for 3 hours, the mixture was fed to an extruder and melted at 280 to 280 ° C.
It was melted at 300 ° C., extruded into a sheet from a die, and quenched to obtain an unstretched film having a thickness of 82 μm.

The obtained unstretched film is preheated, further stretched 3.2 times in the machine direction at a film temperature of 95 ° C. between low-speed and high-speed rolls, quenched, and then coated on one side of the vertically-stretched film. The water-dispersible coating liquid containing the resin of the coating layer A and the particles A in Tables 1 and 2 was coated on the other surface with the resin and the particles B of the coating layer B.
Of water-dispersible coating liquids containing 0.005 μm and 0.020 μm respectively.
It was applied to a thickness of μm (after stretching and drying), and then supplied to a stenter, and stretched 4.1 times in the horizontal direction at 110 ° C. The obtained biaxially stretched film was heat-set with hot air at 220 ° C. for 4 seconds to obtain a polyester film for a magnetic recording medium having a thickness of 6.0 μm.

[Comparative Examples 1 and 3] A magnetic recording medium was manufactured in the same manner as in Example 1 except that the thicknesses of the resin and particles of the coating layers A and B and the core layer C were changed as shown in Tables 1 and 2. A polyester film for use was obtained.

Example 2, Comparative Example 4 Polyethylene terephthalate for the first layer and the second layer of the core layer C shown in Tables 1 and 2 was supplied to two extruders, respectively, to perform multi-manifold co-extrusion. A polyester film for a magnetic recording medium was obtained in the same manner as in Example 1 except that the layers were laminated using a die, and the resins and particles of the film layers A and B were changed as shown in Tables 1 and 2.

[Examples 3 and 4, Comparative Examples 2 and 5] Except that the particles shown in Tables 1 and 2 were used and dimethyl 2,6-naphthalenedicarboxylate was used in the same molar amount instead of dimethyl terephthalate. Polyethylene-2,6-naphthalate (PEN) was obtained in the same manner as in 1.

After drying this polyethylene-2,6-naphthalate at 170 ° C. for 6 hours, an unstretched film satisfying each example and comparative example was obtained in the same manner as in Example 1.

The obtained unstretched film was preheated, stretched 3.5 times in the machine direction at a film temperature of 135 ° C. between low-speed and high-speed rolls, quenched, and then coated with a coating layer A shown in Tables 1 and 2. Then, the aqueous coating solution of the coating layer B was applied in the same manner as in Example 1, then supplied to a stenter and stretched 5.6 times in the horizontal direction at 155 ° C. The obtained biaxially stretched film was
It was heat-set with hot air of 0 ° C. for 4 seconds to obtain a polyester film for a laminated recording medium.

[0068]

[Table 1]

[0069]

[Table 2]

As is evident from Table 2, the polyester film for a magnetic recording medium according to the present invention is excellent in abrasion resistance, winding property and blocking resistance in a film forming process, and has an electromagnetic conversion property when used as a magnetic recording medium. Excellent in characteristics, dropout characteristics and running durability. On the other hand, those which do not satisfy the requirements of the present invention cannot satisfy these characteristics at the same time.

[Usability of the Invention] The polyester film for a magnetic recording medium of the present invention has a total thickness of about 2.5 to 20 μm and is suitably used as a base for a magnetic recording medium. The magnetic recording medium is useful for a metal thin film type. The polyester film of the present invention can be applied to a coating type magnetic recording medium having a magnetic layer thickness of 1 μm or less.
It can also be used for digital signal recording type magnetic recording media.

[0072]

According to the present invention, a base of a magnetic recording medium which is excellent in abrasion resistance, winding property and blocking resistance in a film forming process, and excellent in electromagnetic conversion characteristics, dropout characteristics and running durability. A polyester film useful as a film can be provided.

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Claims (4)

[Claims] A film layer A is formed on one side of a polyester film (layer C) comprising a single layer or two or more layers,
The coating layer A includes inert particles having an average particle diameter of 10 to 100 nm, and a resin as a binder.
1 × 10 ⁶ to 1 × 10 ⁸ protrusions Aa of 0 nm / mm ²
Having an average projection height of only 2
1 × 10 ^{6 to} 3 × 10 ⁸ microprojections Ab of 15 nm /
a film made of a continuous film having a frequency of mm ^2, micro surface roughness Ra ^S only by the continuous film of resin in said coating layer A is 0.4～2.0Nm, and the said coating layer A The surface roughness Ra ^A of the formed surface is 0.3 to 2 nm,
When the layer C is a single layer, it contains substantially no inert particles, and when it has two or more layers, the layer on which the coating layer A is formed contains no inert particles. Polyester film for media. 2. The polyester film for a magnetic recording medium according to claim 1, wherein the resin forming the coating layer A is at least one resin selected from the group consisting of an acrylic resin, a polyester resin, and an acryl-polyester resin. 3. A coating layer B consisting of a continuous thin film is formed on the other side of the layer C, and the coating layer B has an average particle size of 10 to 2 mm.
Inert particles of 00nm containing 3 to 50 wt%, the magnetic recording medium for polyester film of claim 1 or 2 surface roughness Ra ^B of the surface is 1 to 30 nm. 4. A magnetic recording medium comprising a polyester film according to claim 1, 2 or 3, and a magnetic recording layer provided on the film layer A.