JP2003288717A - Laminated film for high-density magnetic recording medium, and high-density magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated film which has proper adhesion quality to a magnetic recording layer and backcoat layer, and suitable for a base film of a magnetic recording medium use in a short-wavelength region, where recording wavelength are 0.4 micrometers or smaller. <P>SOLUTION: This film comprises a polyester film which substantially does not contain inert particles, a binder resin provided on both sides, and an coating layer containing the inert particles and a siloxane copolymerized acrylic resin. A coating layer A on one side has inert particles of means particle diameters of 10-20 nm, in the range of protrusion frequency from 7.0×10<SP>6</SP>to 2.0×10<SP>7</SP>protrusions/mm<SP>2</SP>, and contains a siloxane copolymerized acrylic resin from 3 to 20 wt.% by weight. A coating layer B on the other side contains a siloxane copolymerized acrylic resin from one to 30 wt.%. Surface roughness (Ra) of the coating layer A is in the range of 0.8 to 1.3 nm, and surface roughness (Ra) of the coating layer B is in the range of 6.0 to 15.0 nm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film used as a base film of a magnetic recording medium for high density and a high density magnetic recording medium using the same. More specifically, there is no blocking between films, and when a magnetic recording medium is used, it has excellent adhesiveness to the magnetic recording layer and the back coat layer, and particularly a high signal output in the short wavelength region of 0.4 μm or less of the recording wavelength. The present invention relates to a laminated film used as a base film of a magnetic recording medium for density, and a high-density magnetic recording medium using the same.

[0002]

2. Description of the Related Art Polyester film is a magnetic recording medium such as a video tape, an audio tape, a memory tape, a magnetic sheet, a magnetic disk, etc., because of its excellent mechanical properties, heat resistance, durability, flexibility and surface characteristics. It is preferably used for. The magnetic recording medium is composed of a magnetic recording layer formed of a magnetic metal thin film on one surface of a polyester film and a DLC (Diamond Lid).
It is known that a protective layer made of ke carbon) is sequentially laminated, and an easily backable back coat layer is provided on the other surface.

By the way, in recent years, as the amount of information to be recorded increases, there has been a demand for higher recording density of the magnetic recording medium. As a method for increasing the recording density, it is effective to narrow the track width of the magnetic recording medium or to shorten the recording wavelength. However, in all cases, the reproduction output tends to decrease, and in particular, in order to shorten the recording wavelength to 0.4 μm or less, the drive side has an M value for reproduction.
It becomes necessary to adopt the R head.

Since the MR head has much higher sensitivity than the conventional induction type magnetic head, it is easy to obtain a sufficient reproduction output even for recording with a narrow track width and a short recording wavelength. Generally, the residual magnetization (Mr) and film thickness (t) of the magnetic layer
The reproduction output increases in proportion to the product of (Mr · t). However, even if the value of Mr · t is continuously increased, the output does not increase beyond a certain value and saturates. Further, if Mr · t is increased, noise increases.・
When t is increased, only noise is increased, resulting in S
/ N will decrease. Since the MR head has high sensitivity, the output is likely to be saturated, and it is required to design the MR · t to be considerably lower than the conventional one. For example, a magnetic recording medium having a magnetic layer with a very thin thickness of 33 nm is used for electronic information. It has been proposed in the Technical Report of the Institute of Communication Engineers (MR2000-29).

As described above, in order to shorten the recording wavelength to 0.4 μm or less to increase the recording density, it is necessary to combine the MR head with the high density magnetic recording layer having a film thickness of 100 nm or less. It seems necessary.

By the way, a magnetic recording medium is one in which the above recording layer is laminated on a base film, and the base film requires a system using the magnetic recording medium, that is, optimization of the surface design according to the recording layer. It Then, in order to obtain an excellent electromagnetic conversion characteristic by adopting a recording layer having a film thickness of 100 nm or less, the surface of the base film is required to be extremely smooth. However, if the surface of the base film is made too smooth, there is a problem that blocking between the base films occurs. Specifically, currently marketed DVC (Digital V
video cassette, track width 10 μm, shortest recording length 0.49 μm, magnetic recording layer thickness 150 to 21
(0 nm), an undercoat coating layer is provided on the surface on which the magnetic recording layer is laminated, and projections of particles having an average particle size of 20 to 50 nm are provided in the coating layer, or a release agent is added (for example, JP-A No. 2003-242242). 2000-37838, etc.), it is possible to cope with it to some extent, but when the thickness of the magnetic recording layer is further reduced, it has excellent electromagnetic conversion characteristics and blocking resistance when used as a magnetic recording medium. At present, the base film has not been provided yet.

[0007]

As described above, the MR
In a magnetic recording medium in which a magnetic recording layer having a thin film thickness of 100 nm or less corresponding to the head is laminated, the surface property of the base film directly affects the surface property of the magnetic recording layer, and thus the base film is more excellent than the conventional one. Smoothness is required. However, if the surface is made smooth, blocking between films is likely to occur, and it is the current situation that their contradictory properties cannot be satisfied at the same time.

Therefore, an object of the present invention is to satisfy these contradictory characteristics at the same time, and further, to provide excellent adhesiveness to a magnetic recording layer and a back coat layer when used as a magnetic recording medium, and to record at a recording wavelength of 0.4 μm or less. Another object of the present invention is to provide a laminated film used as a base film of a high-density magnetic recording medium capable of obtaining a high signal output even in the short wavelength region, and a high-density magnetic recording medium using the same.

[0009]

Thus, according to the present invention, an object of the present invention is to provide a polyester film substantially free of inert particles, a binder resin provided on both sides thereof, inert particles and A coating film A comprising a coating layer made of a siloxane copolymerized acrylic resin, wherein the coating layer A provided on one surface of the polyester film has an average particle diameter of inert particles of 10 to 20 n.
In the range of m, 7.0 × 10 ^{6 to} 2.0 × the protrusions formed by the inert particles on the surface not in contact with the polyester film.
3 to 20 based on the weight of the coating layer A and having a siloxane copolymerization acrylic resin in the range of 10 ⁷ pieces / mm ^2.
The coating layer B, which is contained on the other side of the polyester film, contains a siloxane copolymerized acrylic resin.
1 to 30 wt% based on the weight of the coating layer B,
The surface roughness (Ra) of the surface of the coating layer which is not in contact with the polyester film is 0.8 to 1.3 for the coating layer A.
and the coating layer B is in the range of 6.0 to 15.0 nm, which is achieved by the laminated film for high density magnetic recording medium.

In the laminated film for high density magnetic recording medium of the present invention, the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate, or the recording layer has a thickness of 10.
It also includes a laminated film for a high-density magnetic recording medium, which is used as a base film of a magnetic recording medium which is a magnetic metal thin film of 0 nm or less.

Furthermore, according to the present invention, the above-mentioned laminated film for a high-density magnetic recording medium of the present invention, a magnetic metal thin film having a thickness of 100 nm or less provided on the surface of the laminated film on the coating layer A side, and There is also provided a high density magnetic recording medium comprising a back coat layer provided on the surface of the laminated film on the coating layer B side.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The laminated polyester film for a high-density magnetic recording medium of the present invention comprises a polyester film, a coating layer A laminated on the surface of the polyester film on which the magnetic recording layer is to be provided, and the other surface. Coating layer B.

The polyester film of the present invention will be described below.

The polyester constituting the polyester film in the present invention is polyethylene terephthalate,
Examples thereof include polyethylene isophthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, and polyethylene-2,6-naphthalene dicarboxylate. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate are preferred.

The polyester may be a homopolyester or a copolyester. In the case of copolyester, examples of the copolymerization component of polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate include diethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, polyoxyethylene glycol, p- Other diol components such as xylene glycol and 1,4-cyclohexanedimethanol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (in the case of polyethylene-2,6-naphthalenedicarboxylate), 2, 6-Naphthalenedicarboxylic acid (in the case of polyethylene terephthalate), 5-
Other dicarboxylic acid components such as sodium sulfoisophthalic acid, oxycarboxylic acid components such as p-oxyethoxybenzoic acid and the like can be mentioned. The amount of the copolymerization component is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total acid component. Furthermore, in the present invention, a trifunctional or higher polyfunctional compound such as trimellitic acid or pyromellitic acid can be used as a copolymerization component in the polyester, and in this case, the copolymerization amount is such that the polymer is substantially linear. Is preferable, for example 2 mol% or less. It will be easily understood that the copolymerization components in the case of polyesters other than polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate can be considered in the same manner as described above.

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

The thickness of the polyester film in the present invention is 1 to 20 μm, preferably 2 to 10 μm, more preferably 3 to 6 μm. When the thickness exceeds 20 μm, when the magnetic recording medium is used, the specific surface area in the same volume decreases, and as a result, the recording amount decreases. On the other hand, when the thickness is less than 1 μm, it becomes difficult to impart practical mechanical strength to the obtained magnetic recording medium.

The polyester as described above in the present invention is substantially free of inert particles acting as a lubricant. The term "substantially free of inert particles" as used herein means that
It means that the residue of the catalyst is positively deposited or that inert particles are not added from the outside, and the particle size is preferably 50 n.
3 or more particles based on the weight of polyester
It contains less than 00 ppm. When the polyester contains the inert particles, there is a problem that coarse projections are generated on the surface, which deteriorates the electromagnetic conversion characteristics.

The coating layer A in the present invention will be described below.

The coating layer A in the present invention comprises a binder resin, inert particles (inactive particles A) and a siloxane copolymerized acrylic resin.

As the binder resin constituting the coating layer A, alkyd resin, phenol resin, epoxy resin,
Examples thereof include amino resins, polyurethane resins, cellulose resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, and the like. A water-soluble or water-dispersible acrylic resin, polyester resin, or acrylic resin from the viewpoints of adhesion to polyester film, retention of protrusions, slipperiness, etc.
Polyester resin and the like are preferable. These resins may be homopolymers or copolymers, and may be a mixture.

In order to improve blocking resistance, these binder resins preferably have a softening point (measured by drying the binder resin) measured according to JIS K-7206 of 50 ° C. or higher. . However, if the Tg of the binder resin of the coating layer A is too high, the surface of the coating layer A may be rough and the electromagnetic conversion characteristics may be deteriorated depending on the coating conditions and the like. Therefore, when a binder resin having a high Tg is used, it is desirable to devise the coating conditions so as not to roughen the surface. The content of the binder resin is 20 to 9 based on the weight of the coating layer A.
0% by weight is preferred.

The water-soluble or water-dispersible acrylic resin used as the binder resin for the coating layer A is, for example, an acrylate ester (as the alcohol residue, a methyl group,
Ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); Methacrylic acid ester (Alcohol residue is the same as above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, hydroxy-containing monomers such as 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methylmethacrylamide. , N-methyl acrylamide, N-
Amido group-containing monomers such as methylol acrylamide, N-methylol methacrylamide, N, N-dimethylol acrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide and N-phenyl acrylamide; N, N-diethylaminoethyl acrylate, An amino group-containing monomer such as N, N-diethylaminoethyl methacrylate; an acrylic monomer such as an epoxy group-containing monomer such as glycidyl acrylate, glycidyl methacrylate or the like, or containing the monomer as a main component, for example, styrene sulfonic acid, vinyl Monomers containing sulfonic acid groups or salts thereof such as sulfonic acid and salts thereof (eg sodium salt, potassium salt, ammonium salt, etc.); crotonic acid, itaconic acid, acryl acid Monomers containing carboxyl groups or salts thereof such as acids, maleic acid, fumaric acid and salts thereof (eg sodium salt, potassium salt, ammonium salt etc.); containing anhydrides such as maleic anhydride, itaconic anhydride Monomer; Other vinyl isocyanate,
Allyl isocyanate, allyl glycidyl ether, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, methacrylonitrile, alkyl itaconic acid monoester, vinylidene chloride, acetic acid Examples are those made from a combination of monomers (copolymerization components) such as vinyl and vinyl chloride. Among these, those containing a component of a (meth) acrylic monomer such as an acrylic acid derivative or a methacrylic acid derivative in an amount of 50 mol% or more are preferable, and one containing a methyl methacrylate component is particularly preferable. The water-soluble or water-dispersible acrylic resin used in the present invention can be self-crosslinked with a functional group in the molecule, or can be crosslinked with a crosslinking agent such as a melamine resin or an epoxy compound.

Examples of the water-soluble or water-dispersible polyester resin used as the binder resin for the coating layer A include, for example, terephthalic acid, isophthalic acid, phthalic acid, and 1,4 acid components.
-Cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2-potassium sulfoterephthalic acid, tri Meritic acid, trimesic acid,
Examples thereof include polyvalent carboxylic acids such as trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, and monopotassium trimellitic acid. Examples of the hydroxy compound component include ethylene glycol, propylene glycol, and 1,3. -Propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, poly Ethylene oxide glycol, polytetramethylene oxide glycol, dimethylolpropionic acid,
Examples thereof include polyvalent hydroxy compounds such as glycerin, trimethylolpropane, sodium dimethylolethyl sulfonate, and potassium dimethylolpropanoate. Then, a polyester resin can be prepared from these compounds by a conventional method. From the viewpoint of producing an aqueous paint, it is preferable to use an aqueous polyester resin containing a 5-sodium sulfoisophthalic acid component or a carboxylate group. The polyester resin used in the present invention may be a self-crosslinking type having a functional group in the molecule, or may be crosslinked using a curing agent such as a melamine resin or an epoxy resin.

The water-soluble or water-dispersible acrylic-polyester resin used as the binder resin of the coating layer A includes an acrylic-modified polyester resin and a polyester-modified acrylic resin, and the acrylic resin component and the polyester resin component are bonded to each other. It is a thing. For example, those in which an acrylic resin component and a polyester resin component are bonded by a graft type or a block type are included. Acrylic-polyester resin, for example, adds a radical initiator to both ends of the polyester resin to polymerize the acrylic monomer, or adds a radical initiator to the side chain of the polyester resin to polymerize the acrylic monomer. It can be produced by, for example, or by attaching a hydroxyl group to the side chain of an acrylic resin and reacting it with a polyester having an isocyanate group or a carboxyl group at the end to obtain a comb polymer.

The inert particles (inert particles A) contained in the coating layer A in the present invention include polystyrene, polystyrene-divinylbenzene, polymethylmethacrylate, methylmethacrylate copolymer, methylmethacrylate copolymer crosslinked product, and polytetratetrafluoroethylene. Particles of organic polymer such as fluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine resin, silicone resin, acrylic resin, silica, alumina, titanium dioxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, Particles made of an inorganic compound such as carbon black and barium sulfate can be exemplified, and two or more kinds of these may be used in combination, and a core / shell having a multilayer structure composed of substances having different internal and external properties. Shaped grain It may be used.

The average particle size of the inert particles A used in the present invention is 10 to 20 nm. The particle size distribution of the inert particles A is preferably sharp. If the average particle size of the inert particles is less than 10 nm, the winding property of the laminated film and the transport property in the film forming process may be insufficient, or blocking may occur. On the other hand, if the average particle size exceeds 20 nm, the electromagnetic conversion characteristics deteriorate, and particularly when an MR head is used, the head is greatly damaged.

Surface of coating film A side of laminated film of the present invention
(Table not in contact with the polyester film of the coating layer A
The surface) is formed with protrusions due to the inert particles A.
The frequency is 7.0 × 10⁶~ 2.0 x 10⁷Pieces / mm
²Is. The protrusion frequency is 7.0 × 10⁶Pieces / mm²Less than
In some cases, winding properties of laminated film and transportability in film forming process
Shortage or blocking occurs. on the other hand,
Protrusion frequency is 2.0 × 10 ⁷Pieces / mm²Above the
The replacement characteristic is deteriorated, and especially when an MR head is used.
It causes great damage to the head.

The center line average roughness (Ra) of the surface of the laminated film of the present invention on the coating layer A side (the surface of the coating layer A which is not in contact with the polyester film) is 0.8 to 1.3 nm.
Is. If the Ra is less than 0.8 nm, the winding property of the laminated film and the transportability in the film forming process may be insufficient, or blocking may occur. On the other hand, when Ra exceeds 1.3 nm, electromagnetic conversion characteristics are deteriorated, and particularly when an MR head is used, the head is greatly damaged. The Ra may be caused by the coating layer A or the polyester film, or may be formed by the cooperation effect of the coating layer A and the polyester film.

The coating layer A must contain a siloxane copolymerized acrylic resin in which a siloxane component and an acrylic resin component are bonded to each other, for example, in a graft type or a block type, as a release agent. Such siloxane-copolymerized acrylic resin is used, for example, to add radical initiators to both ends of the acrylic resin to polymerize the siloxane, or to attach a hydroxyl group to the side chain of the siloxane and to have an isocyanate group or a carboxyl group at the terminal. It can be produced by, for example, reacting with to form a comb-shaped polymer.

More specifically, as the acrylic resin component used for the polymerization of the siloxane copolymerized acrylic resin, the same resins as those exemplified as the acrylic resin used for the binder resin of the coating layer A can be exemplified.

The siloxane used for the polymerization of the siloxane copolymerized acrylic resin has the following structural formula as a chain component.

[0033]

[Chemical 1]

(Here, R ₁ is CH ₃ , C ₆ H ₅
Alternatively, H and R ₂ are CH ₃ , C ₆ H ₅ , H or a functional group (eg, epoxy group, amino group, hydroxyl group), and n is 10
It means an integer of 0 to 7000. ) Is a siloxane compound having an epoxy group, an amino group, a hydroxyl group at the terminal,
Those having other functional end groups are mentioned. The siloxane compound does not necessarily have to be a homopolymer, but may be a copolymer or a mixture of several homopolymers. The weight ratio of the acrylic resin component to the siloxane component is preferably 98: 2 to 50:50, more preferably 95: 5 to 60:40.

The content of the siloxane copolymerized acrylic resin is 3 to 20% by weight based on the weight of the coating layer A. If the content is less than 3% by weight, the effect as a releasing agent to be obtained is insufficient and blocking between films occurs, while if it exceeds 20% by weight, the adhesiveness to the magnetic layer is deteriorated. , Transfer to the contact surface may occur when rolled into a roll.

In the present invention, the coating layer A preferably contains a surfactant. The surfactant contained in the coating layer A is not particularly limited, and examples thereof include nonionic surfactants, anionic surfactants, and cationic surfactants. Among these, nonionic surfactants, particularly those obtained by adding or binding (poly) ethylene oxide to alkyl alcohol, alkylphenyl alcohol, higher fatty acid, etc. are preferable. As a specific surfactant, as a polyoxyethylene alkylphenyl ether compound, trade name of NOF CORPORATION,
"Nonion NS-230", "Same NS-240", "Same HS-220", "Same HS-240", trade name of Sanyo Kasei Co., Ltd., "Nonipol 200", "Nonipol 4"
00 "," Nonipol 500 "," Octapole 40 "
0 ”; as a polyoxyethylene alkyl ether compound, trade name“ NONION E-2 ”manufactured by NOF CORPORATION
30 ”,“ K-220 ”,“ K-230 ”; as polyoxyethylene ester compounds of higher fatty acids, trade name of NOF Corporation,“ NONION S-15.
4 ”,“ S-40 ”, and the like.

The amount of the surfactant is 5 to 50% by weight, more preferably 5 to 40% by weight, especially 10 to 40% by weight, especially 12 to 30% by weight, based on the weight of the coating layer A. preferable. If the amount of the surfactant is less than 5% by weight, coarse projections that may cause dropouts are likely to occur, while if the amount of the surfactant exceeds 50% by weight, streak-like coating defects due to foaming occur. It will be easier.

In order to improve the blocking resistance of the laminated film, the surfactant used in the coating layer A in the present invention has a softening point (drying the surfactant to dryness) measured according to JIS K-7206. It is preferable that the temperature is 30 ° C. or higher. In addition, in order to prevent coating omission when forming a coating layer by coating a coating liquid with a surfactant other than the above, that is, to reduce the surface tension of the coating liquid, 10% by weight
It is also preferable to use in combination within a range not exceeding (based on total solid content).

The coating layer A in the present invention may be added with other components other than the binder resin, the inert particles, the surfactant and the siloxane copolymerized acrylic resin as long as they do not affect the present invention. . Specifically, in order to improve the slipperiness, it is possible to add a cellulose resin. The layer thickness of the coating layer A is 1 to 100 nm.
Is preferable, and 2 to 20 nm is more preferable.

The coating layer B in the present invention will be described below. In the laminated film of the present invention, a coating layer B made of a binder resin, inert particles (inert particles B) and a siloxane copolymerized acrylic resin is provided on the surface of the polyester film different from the surface on which the coating layer A is formed. In addition,
The layer thickness of the coating layer B is preferably 1 to 100 nm, more preferably 2 to 20 nm.

The inert particles B contained in the coating layer B can be exemplified by the same kind of particles as the inert particles A contained in the coating layer A, and the same particles as the coating layer A or different particles can be used. Well, two or more kinds may be used in combination.

The average particle size of the inert particles B is preferably 5 to
It is 100 nm, more preferably 10 to 50 nm.
The particle size distribution of the inert particles is preferably sharp. If the average particle size is less than 5 nm, the slipperiness and abrasion resistance of the resulting laminated film are likely to decrease, while if the average particle size exceeds 100 nm, particles may fall off or the abrasion resistance may decrease. To do

Surface of coating layer B (Coating layer B of laminated film
Side surface, contacting the polyester film of coating layer B
It is a surface that has not been done. ) Is due to the above-mentioned inert particles B
1 x 10 protrusions⁶~ 1 x 10⁸Pieces / mm²Yes in the range of
To do. The surface protrusion frequency is 1 × 10⁶Pieces / mm²Is less than
As a result, running durability when used as a magnetic recording medium is insufficient.
On the other hand, the surface protrusion frequency is 1 × 10⁸Pieces / mm²Over
Then, the electromagnetic conversion characteristics deteriorate. More preferred coating layer B
Surface protrusion frequency is 2 × 10⁶~ 5 x 10⁷Pieces / mm ², Special
Preferably 3.0 × 10⁶~ 3.0 x 10⁷Pieces / mm²
Is. In addition, the surface protrusion frequency is not included in the coating layer A.
The coating layer B can be adjusted by adjusting the amount of the inert particles B
The inert particles B in the inside are aggregated particles in which two or more particles are aggregated.
The value (aggregation rate) obtained by dividing the offspring by the total number of inert particles B is 2
It is preferably 0% or less. The aggregation rate exceeds 20%
If the magnetic recording medium is
It may adversely affect the electromagnetic conversion characteristics of the body
It

The surface of the coating layer B in the present invention (the surface of the laminated film on the coating layer B side, that is, the surface not in contact with the polyester film of the coating layer B) has a center line average roughness (Ra). 2 to 30 nm, preferably 6 to 15 n
m. If the Ra is less than 2 nm, the winding property of the laminated film and the transportability in the film forming process may be insufficient, or blocking may occur. On the other hand, when Ra exceeds 30 nm, the coating layer B is easily scraped, or the shape is transferred to the other surface (surface on the coating layer A side) when wound in a roll shape. This roughness may be imparted by the coating layer B, may be imparted by the polyester film, or may be imparted by the cooperation effect of the coating layer B and the polyester film.

Examples of the binder resin forming the coating layer B include the same resins as the binder resin forming the coating layer A. Among them, water-soluble or water-dispersible acrylic resin, polyester resin, acrylic-polyester resin Resins such as the above are preferable in terms of adhesion to the polyester film (base film), retention of protrusions, slipperiness, and the like. The binder resin forming the coating layer B may be the same as or different from the binder resin forming the coating layer A. The content of the binder resin is preferably 20 to 90% by weight based on the weight of the coating layer B.

As the surfactant constituting the coating layer B, the same surfactants as constituting the coating layer A can be exemplified. Further, it may be the same as or different from the surfactant of the coating layer A. The content of the surfactant is
Based on the weight of the coating layer B, 5 to 40% by weight is preferable.

A feature of the laminated film of the present invention is that the coating layer B contains a siloxane copolymer acrylic resin. That is, in the present invention, the coating layer A to be the base of the magnetic recording layer has a very flat surface so as to correspond to the recording layer made of a magnetic metal thin film having a thickness of 100 nm or less. It was possible to prevent flocking between the films by including a release agent composed of a siloxane copolymerized acrylic resin in both of the coating layers A and B laminated on.

As the siloxane copolymer acrylic resin, the same siloxane copolymer acrylic resins as those exemplified as those contained in the coating layer A can be exemplified. The content of the siloxane copolymerized acrylic resin in the coating layer B is 1 to 30% by weight, preferably 3 to 20% by weight. This amount is 30
When the content exceeds the weight%, the adhesiveness of the magnetic recording layer when used as a magnetic recording medium is impaired. The siloxane copolymer acrylic resin contained in the coating layer B may be the same as or different from the siloxane copolymer acrylic resin contained in the coating layer A.

The method for producing the laminated film of the present invention will be described below. The laminated polyester film in the present invention can be obtained according to a method known in the art or accumulated in the art.

For example, a biaxially oriented polyester film will be described. Prior to the extrusion die, the polyester is filtered with high precision, and then the melting point Tm.degree. C. to (Tm + 70) .degree.
40 to 9 after extruding the polyester in a molten state at a temperature of (where Tm is the melting point of polyester) into a film.
An unstretched film is obtained by rapidly cooling and solidifying with a cooling roll at 0 ° C. Thereafter, the unstretched film is uniaxially (in the film-forming direction (longitudinal direction) or in the direction (transverse direction) orthogonal thereto) (Tg-10) to (Tg + 7) according to a conventional method.
0) ° C. (however, Tg: glass transition temperature of polyester) is 2.5 to 8.0 times, preferably 3.0 to 7.
Stretching at a stretch ratio of 5 times, and then at a temperature of Tg to (Tg + 70) ° C. in a direction orthogonal to the stretching direction is 2.5 to 8.0 times, preferably 3.0 to 7.5 times. Stretch at a magnification. Further, if necessary, it may be re-stretched in the machine direction and / or the transverse direction. That is, 2 stages, 3
Stretching may be performed in multiple stages, four stages, or multiple stages. The total draw ratio is usually 9 times or more, preferably 12 to 35 times, and more preferably 15 to 32 times as an area draw ratio. Subsequently, a biaxially oriented film (Tg + 7
0) to (Tm-10) ° C., for example 180 to 250
Excellent dimensional stability is imparted by heat-fixing crystallization at ° C. The heat setting time is preferably 1 to 60 seconds.

The coating layers A and B in the present invention can be obtained by applying a coating liquid containing the above-mentioned inert particles, a binder resin, a surfactant and a siloxane copolymer acryl, preferably an aqueous coating liquid. The application is preferably performed on the surface of the polyester film before the final stretching treatment, and the polyester film is preferably stretched in at least uniaxial direction after the application. The coating film is dried before or during this stretching. A particularly preferable coating time is an unstretched film or a longitudinal (uniaxial) stretched film, particularly a longitudinal (uniaxial) stretched film. The coating method is not particularly limited, but examples thereof include a roll coating method and a die coating method.

The solid content concentration of the above coating solution, especially the aqueous coating solution, is
0.2-8.0% by weight, further 0.3-6.0% by weight,
In particular, it is preferably 0.5 to 4.0% by weight. Then, in the coating liquid (preferably an aqueous coating liquid), other components, for example, other surfactants, within a range that does not impair the effects of the present invention,
Stabilizers, dispersants, UV absorbers, thickeners and the like can be added.

The magnetic recording medium of the present invention will be described below. The magnetic recording medium of the present invention can be produced by using the above-mentioned laminated film of the present invention as a base film, which will be described below.

The magnetic recording medium of the present invention is formed by vacuum vapor deposition, sputtering, on the surface of the coating layer A of the above-mentioned laminated film.
By the method such as ion plating, iron, cobalt,
A ferromagnetic metal thin film layer made of chromium or an alloy or oxide containing chromium as a main component is formed. At that time, a protective layer such as DLC or a lubricating layer such as a fluorine-containing carboxylic acid type may be sequentially provided on the metal thin film layer depending on the purpose and use. The thickness of the ferromagnetic metal thin film layer is 100 nm
The following can be suitably used especially for high density recording with a recording wavelength of 0.4 μm or less. On the other hand, the magnetic recording medium of the present invention has a back coat layer provided on the surface of the coating layer B of the above-mentioned laminated film.

[0055]

The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. In addition, "parts" and "%" in Examples and Comparative Examples are based on weight unless otherwise specified, and physical property values and characteristics in the present invention are measured by the following methods and defined, respectively. is there.

(1) Average Particle Size of Particles The average particle size of particles forming protrusions is measured by a light scattering method. That is, Nicomp Instruments Inc.
NICOMP MODEL 270 SUBMI manufactured by
It is indicated by the "equivalent spherical diameter" of the particles at the point of 50% by weight of all the particles determined by CRON PARTICLE SIZER.

(2) Centerline average roughness: Ra Digital Instrument Co. (Digital)
l Instruments Inc. ) Atomic force microscope, trade name "Nano Scope III AF
Ra is the centerline average roughness measured and calculated under the following conditions using a scanner of "M". <Measurement conditions> Scan mode: Tapping mode Scan range: 2 μm × 2 μm (when measuring the surface of coating layer A) 10 μm × 10 μm (when measuring the surface of coating layer B) Number of pixels: 256 × 256 data points Scan speed : 1.0 Hz Measurement environment: room temperature, in air Numerical values are displayed as an average value measured 5 times.

(3) Protrusion frequency SEM (scanning electron microscope, S-4 manufactured by Hitachi, Ltd.)
700), and the surface of the laminated film is magnified 3.5 times.
Ten times of photographs were taken at an angle of 0 ° at a magnification of 10,000, and the number of projections containing particles on the surface of the coating layer was counted, and the average value was calculated as the projection frequency per mm ² by area conversion.

(4) Blocking property The different surfaces of two films are superposed on each other and
A pressure of 5 MPa is set to 65 at 60 ° C. and an atmosphere of 80% RH.
After taking time, the inscribed angle between the peeled films is 18
The film was peeled so as to be 0 degree, and the peeling force required for peeling the film was evaluated (displayed in kg per 1 m of film width). The evaluation is performed based on the peeling force according to the following criteria. ◯: Less than 1 kg / m Δ: 1 kg / m or more and less than 1.5 kg / m ×: 1.5 kg / m or more or the film was torn

(5) C / N measurement On the coating layer A of the laminated film, the incident angle of vapor deposition was 90 to 90 by continuous vacuum oblique vapor deposition in the presence of a slight amount of oxygen.
45 degrees, and a ferromagnetic metal thin film made of cobalt 50n
It is formed to have a thickness of m, and a DLC protective film is formed to have a thickness of 8 nm on the surface thereof. Further, a back coat layer having the following composition was applied on the coating layer B, dried and provided, and cut into a predetermined tape width (12.7 mm) to obtain a magnetic tape. The thickness of the back coat layer after drying was 0.3 μm.
m. Backcoat layer composition: Carbon black: 100 parts Thermoplastic polyurethane: 60 parts Isocyanate compound: 18 parts Silicone oil: 0.5 parts Methyl ethyl ketone: 250 parts The resulting magnetic tape has recording wavelengths of 0.5 μm and 0.3.
The recording signal in μm is reproduced by using each MR head, and C / N is displayed as a value where the value of the magnetic tape using the laminated film of Comparative Example 1 described later is 0 dB.

(6) Running durability The magnetic tape prepared in the above (5) C / N evaluation was tested for 4 times.
After recording / reproducing 500 times at 0 ° C. and 80% RH at a tape traveling speed of 85 cm / min, the above C / N was measured and judged from the amount of change from the initial value before recording / reproducing according to the following criteria. To do. ◯: +0.0 dB or more with respect to the initial value Δ: −1.0 or more and less than 0.0 dB with respect to the initial value ×: Less than −1.0 with respect to the initial value

(7) Adhesiveness of Magnetic Layer The magnetic layer surface of the magnetic tape prepared in the above (5) C / N evaluation was cross-cut with a 2 mm square to obtain an adhesive tape (Scotch Tape No., manufactured by Sumitomo 3M Limited). .600)
Affix so that no air bubbles enter,
2701 (1975), using a manual load roll, T-shaped peeling was performed at a head speed of 100 mm / min using the Tensilon UM-11 manufactured by Toyo Boardwin Co., Ltd., and the 5 cm between the laminated layers was cross-cut. The number of magnetic layers was divided by the total number of cross-cut magnetic layers (magnetic layer peeling rate), and evaluation was made according to the following criteria. ◯: Magnetic layer peeling rate is less than 3% Δ: Magnetic layer peeling rate is 3% or more and less than 10% ×: Magnetic layer peeling rate is 10% or more

(8) Adhesiveness of back coat layer Scotch tape No. 600 (manufactured by 3M Company) was adhered to the back coat layer of the magnetic tape prepared in the above (5) C / N evaluation so as to prevent air bubbles from entering. I put on and JIS. C27
No. 01 (1975) leveling with a manual load roll, and 5 cm between the adhering laminated portions are manufactured by Toyo Boardwin Tensilon U.
T-peeling was performed at a head speed of 300 mm / min using M-11, the peeling strength at this time was determined, and this was divided by the tape width to obtain kg / m. In the T-type peeling, the laminated body is taken with the tape side down, and the distance between the chucks is set to 5 cm. ○: 5 kg / m or more △: 2 kg / m or more and less than 5 kg / m ×: less than 2 kg / m

Example 1 Dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol, manganese acetate as an ester exchange catalyst, antimony trioxide as a polymerization catalyst, and phosphorous acid as a stabilizer were added by a conventional method. Polymerized, essentially free of inert particles, intrinsic viscosity 0.5
Polyethylene-2,6-naphthalate (PEN) of 3 (measured at an ambient temperature of 35 ° C. using orthochlorophenol as a solvent) was obtained.

This polyethylene-2,6-naphthalate
Was dried at 170 ° C for 6 hours and then fed to the extruder to
Melt at 310 ℃, extrude into sheet form from die,
After cooling, an unstretched film was obtained. Unstretched film obtained
Preheat, and the film temperature between the low and high speed rolls is 9
Stretched 3.5 times in the machine direction at 5 ° C, quenched, then machined
On one side of the stretched film, water-soluble coating layer B having the following composition
3.8g / m ², Water solubility of coating layer A on the other side
1.5g / m coating liquid²It was applied so as to have a coating weight of.
After that, continue to supply to the stenter, at 150 ℃
Biaxially stretched film obtained by stretching 5.6 times in the transverse direction
Was heat-fixed with hot air at 200 ° C for 4 seconds to obtain a thickness of 4.6 μm.
A biaxially oriented laminated film was obtained. <Water-soluble coating liquid used for forming coating layer A> Solid content concentration 1.0% Solid content composition ・ Binder resin (made by Takamatsu Yushi Co., Ltd.
Reester IN-170-B) 57.8 parts ・ Inert particles (crosslinked acrylic resin particles, average particle size 15n
m) 5.2 copies ・ Surfactant (Nonion, NS-240, manufactured by NOF CORPORATION)
27 copies ・ Release agent (Shin-Etsu Chemical Co., Ltd. siloxane copolymer
Kuril resin, X-22-8053) 10 parts Water-soluble coating liquid used for forming the coating layer B: Solid content concentration 2.3% Solid content composition ・ Binder resin (Takamatsu Yushi Co., Ltd., acrylic modified
Reester, SH551BK) 49 parts ・ Binder resin (Shin-Etsu Chemical Co., Ltd., Methyl cell)
Loin, SM15) 20 parts -Inert particles (crosslinked acrylic resin particles, average particle size 40n
m) 18 copies ・ Surfactant (Nonion, NS-240, manufactured by NOF CORPORATION)
10 copies ・ Release agent (Shin-Etsu Chemical Co., Ltd. siloxane copolymer
Kuril resin, X-22-8053) 3 parts Obtained biaxially oriented laminated film and magnetism using the same
The characteristics of the recording medium are shown in Table 1.

[Examples 2 to 8 and Comparative Examples 1 to 8] Average particle diameter and composition of inert particles in the water-soluble coating liquid used for forming the coating layers A and B, composition of siloxane copolymerized acrylic resin, A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the coating weight of the water-soluble coating liquid was changed as shown in Table 1. When changing the composition of the fine particles in the coating liquid and the siloxane copolymerized acrylic resin, the composition of the binder resin was adjusted accordingly. Table 1 shows the properties of the obtained biaxially oriented laminated film and the magnetic recording medium using the same.

Example 9 Dimethyl terephthalate and ethylene glycol were added, manganese acetate was used as a transesterification catalyst, antimony trioxide was used as a polymerization catalyst, and phosphorous acid was added as a stabilizer. Polyethylene terephthalate (PET) having an intrinsic viscosity of 0.58 (measured at an ambient temperature of 35 ° C. using orthochlorophenol as a solvent) containing no inert particles was obtained.

170% of this polyethylene terephthalate
After being dried at ℃ for 3 hours, it is fed to an extruder and melted at a temperature of 280-280.
Melt at 300 ℃, extrude into a sheet from the die,
After cooling, an unstretched film was obtained. Unstretched film obtained
Preheat, and the film temperature 9
Stretched 3.2 times in the machine direction at 5 ° C, then rapidly cooled and then machined
The water content of the coating layer B having the above composition on one side of the stretched film
3.8g / m ², Water solubility of coating layer A on the other side
1.5g / m coating liquid²It was applied so as to have a coating weight of.
After that, continue to supply to the stenter, at 110 ℃
It was stretched 4.1 times in the transverse direction. Obtained biaxially stretched fill
The film is heat-set with hot air at 220 ° C for 4 seconds, and the thickness is 6.4 μm.
A biaxially oriented laminated film of was obtained. Obtained biaxially oriented laminate
Table 1 shows the characteristics of the film and the magnetic recording medium using the film.
Shown in.

[0069]

[Table 1]

[0070]

As is clear from Table 1, according to the present invention, the film-blocking property and the adhesion to the magnetic recording layer and the back coat layer when used as a magnetic recording medium are excellent,
In particular, it is possible to provide a base film for obtaining a magnetic recording medium that can obtain a high signal output even in a short wavelength region of a recording wavelength of 0.4 μm or less.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsuho Tojo             3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture             People DuPont Films Co., Ltd. Sagamihara Research Center             In the center (72) Inventor Hirofumi Murooka             3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture             People DuPont Films Co., Ltd. Sagamihara Research Center             In the center F term (reference) 4F100 AJ06B AJ06C AK01B AK01C                       AK25B AK25C AK25H AK25J                       AK41A AK42A AK52B AK52C                       AK52J BA02 BA03 BA06                       BA10A BA10B BA10C BA15                       CC00B CC00C DD07B DD07C                       DE01B DE01C DE01H GB41                       JJ03 JK00 JK13 JL00 YY00B                       YY00C                 5D006 BB01 BB07 CB01 CB07 CB08                       EA03 FA00 FA09

Claims (5)

[Claims] 1. A laminated film comprising a polyester film substantially free of inert particles, and a coating layer comprising a binder resin, inert particles and a siloxane copolymerized acrylic resin provided on both sides of the polyester film. , Coating layer A provided on one surface of the polyester film
Is 7.0 × 10 ^{6 to} 2.0 × 10 ^{7 when} the average particle diameter of the contained inactive particles is in the range of 10 to 20 nm and the protrusions formed by the inactive particles are not in contact with the polyester film.
Has a range of pieces / mm ^2, and a siloxane copolymer acrylic resin, based on the weight of the coating layer A, containing 3 to 20 wt%, the coating layer B disposed on the other surface of the polyester film
Contains 1 to 30 wt% of a siloxane copolymerized acrylic resin based on the weight of the coating layer B, and the surface roughness (Ra) of the surface of the coating layer which is not in contact with the polyester film is the coating layer A. Is in the range of 0.8 to 1.3 nm, and the coating layer B is in the range of 6.0 to 15.0 nm. 2. The laminated film for a high-density magnetic recording medium according to claim 1, wherein the polyester is polyethylene terephthalate. 3. The polyester is polyethylene-2,6-
The laminated film for a high-density magnetic recording medium according to claim 1, which is naphthalene dicarboxylate. 4. The laminated film for a high density magnetic recording medium according to claim 1, which is used as a base film of a magnetic recording medium in which the recording layer is a magnetic metal thin film having a thickness of 100 nm or less. 5. The laminated film for a high-density magnetic recording medium according to claim 1, a magnetic metal thin film having a thickness of 100 nm or less provided on the surface of the laminated film on the side of the coating layer A, and the laminated film. A high density magnetic recording medium comprising a back coat layer provided on the surface of the laminated film on the side of the coating layer B.