JP3923176B2 - Laminated biaxially oriented polyester film - Google Patents

Description

【００６４】
この磁性塗料を、上述の積層二軸配向ポリエステルフィルムの片面（Ｂ層）に、塗布厚０．５μｍになるように塗布し、次いで２，５００ガウスの直流磁場で配向処理を行い、１００℃で加熱乾燥後、スーパーカレンダー処理（線圧；３００ｋｇ／ｃｍ、温度；８０℃）を行い、巻き取った。この巻き取ったロールを５５℃のオーブン中に３日間放置したのち、８ｍｍ幅に裁断して磁気テープを得た。
【００６５】
〔比較例１１〕
表１に示す粒子をポリエステルＡ層およびポリエステルＢ層に添加し、またフィルムのヤング率が縦方向５５０ｋｇ／ｍｍ^２、横方向１，２００ｋｇ／ｍｍ^２になるように縦方向および横方向の延伸倍率を変える以外は、実施例１と同様にして、積層二軸配向ポリエステルフィルムを得て、その後、実施例１と同様にして磁気テープを得た。
【００６６】
【表１】

【００６７】
表１から明らかなように、本発明によるものは、優れた電磁変換特性を示しつつ、優れた巻き取り性、搬送性の特性を有している。
【００６８】
【発明の効果】
本発明によれば、優れた電磁変換特性を有し、かつ優れた巻き取り性、搬送性などの特性を有する積層二軸配向ポリエステルフィルムが得られる。このポリエステルフィルムは、磁気記録媒体のベースフィルムとして、特に１／２インチビデオテープ、８ｍｍビデオテープ、データカートリッジテープ、デジタル方式のビデオテープなどの磁気テープのベースフィルムとして有用である。
【図面の簡単な説明】
【図１】フィルムをロール状に巻いたときのブツの発生状況を模式的に示す説明図である。
【図２】フィルム縦シワの発生状況と、この比率を求める模式的説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laminated biaxially oriented polyester film. More specifically, the present invention is excellent in film winding and handling properties, and is a high density magnetic recording medium, preferably a digital magnetic recording medium, particularly an ultra high density magnetic recording medium. The present invention relates to a laminated biaxially oriented polyester film capable of imparting excellent electromagnetic conversion characteristics when used as a base film.
[0002]
[Prior art]
A biaxially oriented polyester film typified by a polyethylene terephthalate film is excellent in physical and chemical properties, and is therefore widely used, particularly as a base film for magnetic recording media.
[0003]
In recent years, magnetic recording media have been increased in density and capacity, and accordingly, flattening of the base film and reduction in thickness have been demanded. In particular, recently, a multilayer metal tape having performance comparable to a vapor deposition tape has been developed, and the demand for flattening the base film has increased. However, if the surface of the base film is flattened in order to maintain excellent electromagnetic conversion characteristics, the slipperiness or air squeeze property will deteriorate, and if it is rolled up, it will be wrinkled or crumpled easily, and it will be rolled up. Becomes very difficult. Also, in the film processing step, if the slipperiness is poor, friction with the metal roll that comes into contact increases, wrinkles enter the film, and the magnetic layer cannot be applied well, and the calendar cannot be applied well.
[0004]
In general, the slipperiness of a polyester film can be improved by (1) a method in which inert particles are precipitated from a catalyst residue in the production process in the raw polymer, or (2) a method in which inert particles are added. A method of providing fine irregularities on the surface is employed. In general, the larger the size and the larger the content of particles in these films, the greater the improvement in slipperiness.
[0005]
On the other hand, as described above, the surface of the base film is required to be as flat as possible from the viewpoint of improving electromagnetic conversion characteristics. If the surface roughness of the base film is rough, when processing into a magnetic recording medium, the surface irregularities of the base film protrude to the surface of the magnetic layer even after the magnetic layer is formed, thereby deteriorating electromagnetic conversion characteristics. In this case, the larger the particles in the base film and the greater the content thereof, the rougher the surface and the worse the electromagnetic conversion characteristics.
[0006]
As a means to achieve the contradictory properties of improving slipperiness and improving electromagnetic conversion characteristics, a laminated film improves the electromagnetic conversion characteristics by flattening the surface on which the magnetic layer is applied, and the opposite surface is a rough surface. Means for improving the slipperiness by converting is known. However, even when the laminated biaxially oriented polyester film as described above is used and the surface opposite to the surface on which the magnetic layer is applied (hereinafter also referred to as “rough surface”) is roughened, the base thickness is thin, so Depending on the amount, type, and particle size of the lubricant to be added, there is a problem that the surface to which the magnetic layer is applied is affected, waviness is caused on the flat surface, and the flatness is deteriorated.
[0007]
In particular, in recent high-density magnetic recording media, further flattening of the magnetic layer is required, and a metal calender with a high linear pressure is used. From the rough surface side to the surface property by pushing up the protrusion on the flat surface. The negative effects of are increasing.
[0008]
In order to reduce the protrusion of the projection on the flat surface from the rough surface side, a method of reducing the particle size of the lubricant contained in the rough surface side or a method of slightly containing a large particle size has been proposed. However, in the former case, since the height of the formed protrusion is low, sufficient air squeezing property cannot be obtained, and in the latter case, the formed protrusion frequency is low, so that the film slips sufficiently. Sex cannot be obtained. In addition, when the film is wound in a roll shape, vertical wrinkles are generated in the former case, and in the latter case, there is a problem in that sufficient product yield cannot be obtained.
[0009]
On the other hand, in order to improve electromagnetic conversion characteristics, further flattening of the film surface on the magnetic layer surface side has been demanded, and a flat layer substantially free of a lubricant has been proposed. There is a new problem in that the transportability on the flat surface side becomes poor, wrinkles occur in the process, and the product yield is greatly reduced.
[0010]
[Problems to be solved by the invention]
The present invention has excellent film winding and handling properties, and excellent electromagnetic conversion when used as a base film as a high-density magnetic recording medium, preferably a digital magnetic recording medium, particularly an ultra-high-density magnetic recording medium. It is providing the laminated biaxially-oriented polyester film which can provide a characteristic.
[0011]
[Means for Solving the Problems]
  The present invention comprises a polyester A layer laminated on a polyester B layer,(1)~(4)It is a laminated biaxially oriented polyester film that satisfies the above requirements.
[0012]
  (1)The polyester A layer contains at least two kinds of lubricants I and II having different average particle diameters. ₁ ) Is 0.2 μm or more and less than 0.4 μm, and the average particle size of the lubricant I (D₁) And the average particle size of lubricant II (D₂) Difference (D₁-D₂) Is 0.10.2μm, the content of lubricant I0.15-0.4% by weight and the content of lubricant II is 0.1-0.8% by weight.
[0013]
  (2)The polyester B layer contains a lubricant having an average particle size of 0.05 to 0.2 μm and a content of 0.005 to 0.1% by weight.
[0014]
  (3)The surface roughness WRa of the polyester A layer is 2 to 6 nm, and the total number of protrusions is 1 × 10.⁴Ke / mm²The cumulative number of protrusions is 30 / mm²The projection height at 20 to 50 nm, the surface roughness WRa of the polyester B layer is 0.5 to 2 nm, and the cumulative number of projections is 30 / mm.²The projection height at is 20 nm or less.
[0015]
  (4)Film friction coefficient is0.4It is as follows.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention uses a laminated biaxially oriented polyester film as the film, specifies the particle size and content of the lubricant contained on the rough surface side and the flat surface side, and specifies the surface roughness on the rough surface side and the flat surface side. By specifying the coefficient of friction of the film, a laminated biaxially oriented polyester film having excellent electromagnetic conversion characteristics for the above-described high-density magnetic recording medium and excellent in winding property and transportability as a base film To get.
[0017]
The polyester used in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. This polyester is substantially linear and has film-forming properties, particularly film-forming properties by melt molding. Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenylether dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenylketone dicarboxylic acid, and anthracene dicarboxylic acid. Etc. Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, or 1,4-cyclohexanedimethanol. And alicyclic diols such as
[0018]
In the present invention, the polyester preferably includes alkylene terephthalate and / or alkylene-2,6-naphthalate as a main constituent. Among these polyesters, in particular, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, A copolymer in which 80 mol% or more of the glycol component is ethylene glycol is preferred. In this case, 20 mol% or less of the total acid component can be the above aromatic dicarboxylic acid other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid, for example. Acid; can be an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. Further, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol, and for example, aromatic diols such as hydroquinone, resorcin, 2,2-bis (4-hydroxyphenyl) propane; It can also be an aliphatic diol having an aromatic ring such as 4-dihydroxydimethylbenzene; polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polyethylene glycol, and polytetramethyl glycol.
[0019]
In the polyester of the present invention, for example, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid or an aliphatic oxyacid such as ω-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component Those which are copolymerized or bonded in an amount of 20 mol% or less based on the total amount of the above are also included.
[0020]
Furthermore, the polyester in the present invention includes a polycarboxylic acid or polyhydroxy compound having a functionality of 3 or more, such as trimellitic acid, in an amount in a substantially linear range, for example, 2 mol% or less based on the total acid component. And those obtained by copolymerizing pentaerythritol and the like.
[0021]
The polyester is known per se and can be produced by a method known per se. The polyester preferably has an intrinsic viscosity of 0.4 to 0.9 determined as a solution in o-chlorophenol at 35 ° C., more preferably 0.5 to 0.7. Particularly preferred is .55 to 0.65.
[0022]
The laminated biaxially oriented polyester film in the present invention is composed of two layers, a polyester A layer and a polyester B layer. The two layers of polyester may be the same or different, but the same is preferred.
[0023]
In the laminated biaxially oriented polyester film according to the present invention, (1) the polyester A layer contains at least two kinds of lubricants I and II having different average particle diameters._I) Is 0.2 μm or more and less than 0.4 μm, and the average particle size of the lubricant I (D₁) And the average particle size of lubricant II (D₂) Difference (D₁-D₂) Is 0.1 to 0.3 μm, the content of the lubricant I is 0.1 to 0.4% by weight, and the content of the lubricant II is 0.1 to 0.8% by weight.
[0024]
In the case of a single-component lubricant system, when a large particle size is used, it is necessary to reduce the content from the viewpoint of electromagnetic conversion characteristics, the friction coefficient of the film becomes high, and when wound into a roll, It occurs and does not wind well. In addition, when a small particle size is used, the content can be increased, but sufficient air squeezing property cannot be obtained, and when the film is wound in a roll shape, vertical wrinkles are generated and the film cannot be wound well. . And from the relationship between the occurrence of bumps and vertical wrinkles, the single component system cannot take an appropriate region of particle size and content.
[0025]
In the present invention, it comprises at least two lubricant systems containing at least lubricants I and II having different average particle diameters. And the average particle size of the lubricant I (D₁) Is 0.2 μm or more and less than 0.4 μm, preferably 0.25 μm or more and less than 0.35 μm, particularly preferably about 0.3 μm. If this average particle size is less than 0.2 μm, the air squeeze property is insufficient, vertical wrinkles are generated, and winding is not possible. On the other hand, when it is 0.4 μm or more, when it is used as a base film for the latest ultra-high density magnetic recording medium, the content cannot be increased so much from the viewpoint of electromagnetic conversion characteristics, and the friction coefficient of the film becomes high. Occurs and does not wind well. Further, the content of the lubricant I is 0.1 to 0.4% by weight, preferably 0.15 to 0.3% by weight. If it is less than 0.1% by weight, the coefficient of friction of the film is high, and when it is wound into a roll, fluff is generated and it cannot be wound well. On the other hand, if it is 0.4% by weight or more, satisfactory electromagnetic conversion characteristics cannot be obtained.
[0026]
Further, the average particle size of the lubricant II (D₂) Is the average particle size of the lubricant I (D₁) To 0.1 to 0.3 μm, preferably 0.1 to 0.2 μm. The difference (D₁-D₂) Is less than 0.1 μm, it is close to a single component system, and the same problem as in the single component system occurs. On the other hand, if the difference is larger than 0.3 μm, the average particle size of the lubricant II becomes too small, the formation of protrusions on the background is too small, the coefficient of friction of the film becomes high, and when it is wound in a roll shape, a flaw occurs. Can't wind well. Further, the content of the lubricant II is 0.1 to 0.8% by weight, preferably 0.15 to 0.5% by weight, and more preferably 0.2 to 0.3% by weight. If this content is less than 0.1% by weight, the coefficient of friction of the film becomes high, and when wound into a roll, fluff is generated and the film cannot be wound well. On the other hand, when it is more than 0.8% by weight, the surface roughness becomes rough and satisfactory electromagnetic conversion characteristics cannot be obtained.
[0027]
Next, in the laminated biaxially oriented polyester film of the present invention, (2) the polyester B layer has an average particle size of 0.05 to 0.2 μm, preferably 0.1 to 0.2 μm, and a content of 0.005. 0.1% by weight, preferably 0.01 to 0.05% by weight of lubricant is contained. If the average particle size is less than 0.05 μm, or the content is less than 0.005% by weight, the surface on the flat surface side becomes too flat, the coefficient of friction with the metal roll becomes high, the film does not run well, Wrinkles may occur, the magnetic layer cannot be applied well, and the calendar cannot be applied properly. On the other hand, when the average particle diameter exceeds 0.2 μm or the content is more than 0.1% by weight, satisfactory electromagnetic conversion characteristics cannot be obtained.
[0028]
Next, in the laminated biaxially oriented polyester film of the present invention, (3) the surface roughness WRa of the polyester A layer is 2 to 6 nm, preferably 4 to 6 nm, and the total number of protrusions is 1 × 10.^FourKe / mm²Or more, preferably 1.4 × 10^FourKe / mm²The cumulative number of protrusions is 30 / mm²The protrusion height at 20 to 50 nm, preferably 30 to 50 nm, the surface roughness WRa of the polyester B layer is 0.5 to 2 nm, preferably 0.8 to 1.5 nm, and the cumulative number of protrusions is 30 / mm.²The height of the protrusion is 20 nm or less, preferably 15 nm or less.
[0029]
The surface roughness WRa of the polyester A layer (rough surface side) is less than 2 nm, and the total number of protrusions is 1 × 10.^FourKe / mm²If it is less than 1, the film friction coefficient becomes high, and when it is wound into a roll, fluff is generated and it cannot be wound well. Further, when the surface roughness WRa of the polyester A layer exceeds 6 nm, the magnetic layer surface becomes rough due to pushing up or transfer to the flat surface side surface in the tape processing step, and satisfactory electromagnetic conversion characteristics are obtained. I can't. Furthermore, the cumulative number of protrusions of the polyester A layer is 30 / mm.²When the protrusion height at is less than 20 nm, sufficient air squeeze property cannot be obtained, and when the film is wound in a roll shape, vertical wrinkles are generated and the film cannot be wound well. On the other hand, when the thickness exceeds 50 nm, the number of high protrusions increases, and the magnetic layer surface becomes rough due to push-up to the flat surface side surface or transfer in the tape processing step, and satisfactory electromagnetic conversion characteristics cannot be obtained.
[0030]
On the other hand, if the surface roughness WRa of the polyester B layer (flat surface side) is less than 0.5 nm, the friction coefficient between the flat surface side and the metal roll increases, the film does not run well, wrinkles enter, The magnetic layer cannot be applied well or the calendar cannot be applied properly. On the other hand, when the surface roughness WRa exceeds 2 nm, the surface of the magnetic surface becomes rough and satisfactory electromagnetic conversion characteristics cannot be obtained.
[0031]
The cumulative number of protrusions of the polyester B layer is 30 / mm²If the projection height at 20 exceeds 20 nm, the surface of the magnetic layer becomes rough, and satisfactory electromagnetic conversion characteristics cannot be obtained.
[0032]
The above condition (3) is that the thickness of the polyester A layer and the sizes and amounts of the lubricants I and II contained in the A layer are adjusted, and the thickness of the polyester B layer and the lubricant contained in the B layer are adjusted. This can be achieved by adjusting the size and amount, and further by adjusting the stretching conditions.
[0033]
Next, in the laminated biaxially oriented polyester film of the present invention, (4) the film friction coefficient is 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less. When the film friction coefficient exceeds 0.5, when the film is wound in a roll shape, the film enters and does not wind well.
[0034]
The lubricant contained in the polyester A layer or polyester B layer in the present invention is preferably spherical inert particles having a particle size ratio (major axis / minor axis) in the range of 1.0 to 1.2. As the spherical inert particles, inorganic particles such as spherical silica are preferable. In addition, crosslinked polystyrene resin particles, crosslinked silicon resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, crosslinked polyester particles, polyimide particles, melamine resin. Examples thereof include heat-resistant polymer particles such as particles. Among the heat resistant polymer particles, it is preferable to use crosslinked polystyrene resin particles or crosslinked silicon resin particles because the effect of the present invention becomes more remarkable.
[0035]
The polyester A layer preferably contains a lubricant III having an average particle size smaller than that of the lubricants I and II. Here, as the lubricant III, inert particles having an average particle size of 0.1 μm or less, and 0.04 to 0.1 μm, for example, spherical silica, crosslinked resin particles, and the like are preferably exemplified. By containing the lubricant III, the film friction coefficient is reduced, and damage to the film due to contact with the pass roll in the film forming process or tape forming process is reduced.
[0036]
Further, the laminated biaxially oriented polyester film of the present invention preferably has a longitudinal Young's modulus of 500 to 1,000 kg / mm.²More preferably, 500 to 900 kg / mm², Particularly preferably 500 to 750 kg / mm²The lateral Young's modulus is preferably 500 to 1,400 kg / mm²More preferably, 600-1300 kg / mm²Particularly preferably 700 to 1,250 kg / mm²Preferably, the sum of the vertical and horizontal Young's modulus is preferably 1,300 to 2,000 kg / mm²More preferably, 1,400-1800 kg / mm²It is.
[0037]
Longitudinal Young's modulus is 500 kg / mm²Below, the longitudinal strength of the magnetic tape becomes weak, and if a strong force is applied in the longitudinal direction during recording / reproduction, the magnetic tape is easily broken. Also, the Young's modulus in the lateral direction is 500 kg / mm²If it is less than 1, the transverse strength of the magnetic tape becomes weak, the contact between the tape and the magnetic head becomes weak, and satisfactory electromagnetic conversion characteristics cannot be obtained. On the other hand, the Young's modulus in the vertical direction is 1,000 kg / mm²If the value exceeds 1, the strength in the lateral direction decreases, the contact between the tape and the magnetic head becomes weak, and satisfactory electromagnetic conversion characteristics cannot be obtained. In addition, the Young's modulus in the lateral direction is 1,400 kg / mm²Exceeding this causes the strength in the vertical direction to decrease, and if a strong force in the vertical direction during recording / reproduction is applied, it will easily break. Furthermore, the sum of vertical and horizontal Young's modulus is 1,300 kg / mm²If it is less than 1, the contact between the tape and the magnetic head becomes weak, and satisfactory electromagnetic conversion characteristics cannot be obtained. On the other hand, this sum is 2,000 kg / mm.²If it exceeds 1, the draw ratio becomes high during film formation, the film breaks frequently, and the product yield deteriorates.
[0038]
When the laminated biaxially oriented polyester film of the present invention is used as a helical magnetic recording medium tape, the lateral Young's modulus is preferably higher than the longitudinal Young's modulus from the viewpoint of improving the contact between the tape and the magnetic head.
[0039]
Furthermore, the polyester A layer and / or polyester B layer in the present invention is preferably made of polyethylene terephthalate or polyethylene-2,6-naphthalate, and more preferably made of polyethylene-2,6-naphthalate. In particular, when the thickness of the whole film is 6 μm or more, it may be composed of polyethylene terephthalate, but when it is less than 6 μm, polyethylene-2,6-naphthalate that can further increase the Young's modulus is preferable.
[0040]
The total thickness of the laminated biaxially oriented polyester film in the present invention is 2 to 10 μm, preferably 3 to 7 μm, and more preferably 4 to 6 μm. If the thickness is less than 2 μm, the film is thin, so that the film breaks frequently during film formation, and the film winding property becomes poor, and a good film roll cannot be obtained. Further, the thickness of the flat layer is reduced, and the influence of the surface property on the flat surface from the rough surface side is increased, so that a satisfactory flat surface property cannot be obtained. On the other hand, if it exceeds 10 μm, the thickness of the tape becomes thick, for example, the length of the tape put in the cassette becomes short, and a sufficient magnetic recording capacity cannot be obtained.
[0041]
The laminated biaxially oriented polyester film in the present invention can be produced by a method conventionally known or accumulated in the art. For example, it can be obtained by first producing an unoriented laminated film and then biaxially orienting the film. This unoriented laminated film can be produced by a conventionally produced method for producing laminated films. For example, a method of laminating the polyester A layer and the polyester B layer forming the opposite surface in a molten state or a cooled and solidified state of the polyester can be used. More specifically, it can be produced by a method such as coextrusion or extrusion lamination. The film laminated | stacked by the above-mentioned method can be performed according to the manufacturing method of the biaxially-oriented polyester film accumulate | stored conventionally, and can be made into a biaxially-oriented film. For example, an unstretched laminated film is obtained by melting and coextrusion at a temperature of melting point (Tm; ° C.) to (Tm + 70) ° C., and this unstretched laminated film is uniaxially (longitudinal or transverse) (Tg-10 ) To (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester) 2.5 to 6.0 times, preferably 3.0 to 5.5 times, particularly preferably 3.0 to 5.0 times. The film is stretched at a double magnification, and then in a direction perpendicular to the stretching direction (when the first stage is the longitudinal direction, the second stage is the transverse direction) at a temperature of Tg to (Tg + 70) ° C., 3.5 to 7.5. It is desirable that the film is stretched at a magnification of 4.0 times, preferably 4.0 to 7.0 times, particularly preferably 4.5 to 6.5 times. Furthermore, you may extend | stretch again in the vertical direction and / or a horizontal direction as needed. Thus, the total draw ratio is preferably 9 times or more, more preferably 12 to 35 times, and particularly preferably 15 to 30 times as the area draw ratio. Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° C. to (Tm−10) ° C., for example, 190-250 ° C., more preferably 200-240 ° C. The heat setting time is preferably 1 to 60 seconds.
[0042]
The laminated biaxially oriented polyester film of the present invention has excellent flatness, slipperiness, winding property and the like, and is preferably used as a base film for high-density magnetic recording media, particularly digital recording magnetic recording media.
[0043]
The laminated biaxially oriented polyester film of the present invention is formed on the surface of the polyester B layer by a method such as vacuum deposition, sputtering, or ion plating, and is made of iron, cobalt, chromium, or an alloy or oxide mainly composed of these. A magnetic metal thin film layer is formed, and a protective layer such as diamond-like carbon (DLC) and a fluorine-containing carboxylic acid-based lubricating layer are sequentially provided on the surface of the magnetic metal thin film layer according to the purpose, application, and necessity. A known back coat layer is provided on the surface of the polyester A layer side. Thereby, it is possible to obtain a vapor-deposited magnetic recording medium for high-density recording, which is excellent in electromagnetic conversion characteristics such as output in a short-wave super-long region, S / N, C / N, etc., and has low dropout and error rate. This vapor deposition type electromagnetic recording medium is extremely useful as Hi8 for analog signal recording, digital video cassette recorder (DVC) for digital signal recording, data 8 mm, tape medium for DDSIV.
[0044]
In addition, the laminated biaxially oriented polyester film of the present invention has a surface of the polyester B layer and iron or fine acicular magnetic powder mainly composed of iron as a binder such as polyvinyl chloride or a vinyl chloride-vinyl acetate copolymer. It is uniformly dispersed and coated so that the magnetic layer thickness is 1 μm or less, preferably 0.1 to 1 μm. Excellent output characteristics in the short wavelength region, S / N, C / N and other electromagnetic conversion characteristics, and dropout Thus, a metal-coated magnetic recording medium for high density recording with a low error rate can be obtained. Further, if necessary, a nonmagnetic layer containing fine titanium oxide particles or the like can be dispersed and coated in the same organic binder as the magnetic layer as an underlayer of the metal powder-containing magnetic layer. This metal-coated magnetic recording medium includes 8 mm video for analog signal recording, Hi8, β cam SP, W-VHS, digital video cassette coder (DVC) for digital signal recording, data 8 mm, DDSIV, digital β cam, D2, It is extremely useful as a magnetic tape medium for recording digital signals such as D3 and SX.
[0045]
Further, the laminated biaxially oriented polyester film of the present invention is obtained by applying a fine powder of acicular fine magnetic powder mainly composed of iron oxide or chromium oxide or plate-like fine magnetic powder such as barium ferrite to the surface of the polyester B layer. Uniformly dispersed in a binder such as vinyl or vinyl chloride-vinyl acetate copolymer, and coated so that the magnetic layer thickness is 1 μm or less, preferably 0.1 to 1 μm. , C / N and other electromagnetic conversion characteristics are excellent, and a coating type magnetic recording medium for high density recording with low dropout and error rate can be obtained. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like is dispersed in the same organic binder as the magnetic layer on the B layer as an underlayer of the oxide-containing magnetic layer, It can also be painted. This oxide-coated magnetic recording is useful as a high-density oxide-coated magnetic recording medium such as a digital signal recording data streamer QIC.
[0046]
The W-VHS is an analog HDTV signal recording VTR, and the DVC is applicable to digital HDTV signal recording. The film of the present invention is extremely suitable for these HDTV compatible VTR magnetic recording media. Useful base film.
[0047]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to an Example. In addition, each characteristic value in an Example was measured with the following method.
[0048]
Average particle size (DP)
It measured using the Shimadzu Corp. make and CP-50 type | mold centrifugule particle size analyzer (Centrifugal Particle Size Analyzer). The particle size corresponding to 50 mass percent is read from the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is taken as the average particle size (“particle size measurement”). Technology ", published by Nikkan Kogyo Shimbun, 1975, pages 242-247).
[0049]
Layer thickness
Using a secondary ion mass spectrometer (SIMS), among the particles in the film ranging from the surface layer to a depth of 3,000 nm, the concentration ratio of the element due to the highest concentration of particles to the carbon element of polyester (M⁺/ C⁺) Is the particle concentration, and analysis in the thickness direction is conducted from the surface to a depth of 3,000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. And the particle concentration once reached the maximum value starts to decrease again. Based on this concentration distribution curve, a depth that is ½ of the maximum value of the surface particle concentration (this depth is deeper than the maximum value of the maximum value) was obtained, and this was defined as the stacking thickness. The conditions are as follows.
[0050]
(1) Measuring device
Secondary ion mass spectrometer (SIMS)
A-DIDA3000, manufactured by Atomica, Germany
(2) Measurement conditions
Primary ion species; O₂ ⁺
Primary ion acceleration voltage: 12KV
Primary ion current; 200 nA
Raster area: 400 μm
Analysis area: 30% gate
Measuring vacuum: 6.0 × 10^-9  Torr
E-GUN; 0.5KV-3.0A
In addition, when the most contained particles in the range from the surface layer to a depth of 3,000 nm are organic polymer particles, it is difficult to measure with SIMS. Therefore, XPS (X-ray photoelectron spectroscopy), IR (red) while etching from the surface. The depth profile similar to the above may be measured by the outer spectroscopic method or the like to obtain the stacking thickness.
[0051]
Young's modulus
The film was cut into a sample width of 10 mm and a length of 15 cm, and the chuck was set to 100 mm. The film was pulled with an Instron type universal tensile tester under the conditions of a tensile speed of 10 mm / min and a chart speed of 500 mm / min. The Young's modulus was calculated from the tangent line of the rising part of.
[0052]
Total number of protrusions and protrusion distribution
Using a non-contact type three-dimensional roughness meter (TOPO-3D) manufactured by WYKO, measurement magnification is 40 times, measurement area is 242 μm × 239 μm (0.058 mm)²) And at least n = 10 or more, and with the surface projection analysis software built in the roughness meter, each projection height Hi (μm) is 1 mm above the same height.²The average number of protrusions per contact is obtained and Yi (ke / mm²) And a cumulative projection distribution curve was obtained.
The total number of protrusions is the maximum number of protrusions Y at which the cumulative protrusion distribution curve reaches saturation._max(Ke / mm²) Is the total number of protrusions.
[0053]
Windability
The number of bumps having a size of 2 mmφ or more when the film was wound in a roll shape with a width of 1,000 mm (see FIG. 1) and the occurrence of vertical wrinkles (see FIG. 2) were observed.
About the number of irregularities, it converted proportionally per 1m of product width.
[0054]
In addition, the evaluation calculated | required the average value per one when 10 or more rolls were wound, and evaluated it as follows.
(A)
◎; 0 to 2 units / m
○: 3 to 5 units / m
Δ: 6 to 10 units / m
×: 11 units / m or more
(B) Vertical wrinkles
◎; 0 to less than 10%
○: Less than 10 to 20%
Δ: Less than 20-30%
×: 30% or more
[0055]
Film thickness
Ten films were stacked so that rubber did not enter, and the thickness was measured with a dot-type electronic micrometer to calculate the film thickness per sheet.
[0056]
Transportability
Generation | occurrence | production of the process wrinkle by the film flatness in a magnetic layer application | coating process or a calendar process and the slipperiness defect with a metal roll was determined by the following evaluation criteria.
◎: No wrinkles are generated.
○: Wrinkles are slightly generated, but there is no problem in the process.
Δ: There are wrinkles, but they can be used in the process.
×: Wrinkles are strong and cannot be used.
[0057]
Electromagnetic conversion characteristics
Using the following commercially available equipment, a signal having a frequency of 7.4 MHz is recorded, and the ratio of the 6.4 MHz and 7.4 MHz values of the reproduced signal is defined as the C / N of the tape. The relative value was expressed as 0 dB.
◎; 0dB or more
○: -2 to less than 0 dB
×: Less than −2 dB
[0058]
Here, the devices used are as follows.
8 mm video recorder; manufactured by Sony Corporation, EDV-6000, C / N measurement; manufactured by Shibasoku Co., Ltd., noise meter
[0059]
Friction coefficient of film
Place two superposed films on a fixed glass plate, and take the film under the superposed film (film in contact with the glass plate) using a constant speed roll (about 10 cm / min) A detector was fixed to one end of the upper film (opposite to the take-up direction of the lower film), and the tensile force at the start of film / film was detected. The thread used at this time weighs 1 kg and has a lower area of 100 cm.²I used one.
[0060]
    Example 13,4, Comparative Examples 1 to10]
  Add dimethyl-2,6-naphthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and particles shown in Table 1 as a lubricant, Polymerization was conducted by a conventional method to obtain polyethylene-2,6-naphthalate (PEN) for layer A and layer B having an intrinsic viscosity (value measured at 35 ° C. using o-chlorophenol as a solvent) of 0.61 dl / g. .
[0061]
These polyethylene-2,6-naphthalate pellets were dried at 170 ° C. for 6 hours, then supplied to two extruder hoppers, melted at a melting temperature of 280 to 300 ° C., and a multi-manifold coextrusion die was used. Then, the A layer was laminated on one side of the B layer and extruded onto a rotary cooling drum having a surface finish of about 0.3 S and a surface temperature of 60 ° C. to obtain a laminated unstretched film having a thickness of 105 μm.
[0062]
This laminated unstretched film is preheated to 120 ° C., further heated by an IR heater with a surface temperature of 900 ° C. from 15 mm above between low-speed and high-speed rolls, stretched 4.0 times, rapidly cooled, and subsequently It was supplied to a stenter and stretched 5.0 times in the transverse direction at 145 ° C. The obtained biaxially stretched film was heat-fixed with hot air at 210 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 5.2 μm. The Young's modulus of this film is 600 kg / mm in the longitudinal direction.², 900 kg / mm in the horizontal direction²Met.
[0063]
The magnetic tape was manufactured as follows.
That is, the composition shown below was put in a ball mill, kneaded and dispersed for 16 hours, 5 parts by weight of an isocyanate compound (Desmodur L manufactured by Bayer) was added, and high-speed shear dispersion was performed for 1 hour to obtain a magnetic paint. .

[0064]
This magnetic paint is applied to one side (B layer) of the above-mentioned laminated biaxially oriented polyester film so as to have a coating thickness of 0.5 μm, and then subjected to orientation treatment with a 2,500 gauss direct current magnetic field at 100 ° C. After heat drying, a super calender treatment (linear pressure: 300 kg / cm, temperature: 80 ° C.) was performed and wound up. The wound roll was left in an oven at 55 ° C. for 3 days and then cut into a width of 8 mm to obtain a magnetic tape.
[0065]
    [Comparative Example 11]
  The particles shown in Table 1 are added to the polyester A layer and the polyester B layer, and the Young's modulus of the film is 550 kg / mm in the longitudinal direction.², Lateral direction 1,200kg / mm²A laminated biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the draw ratios in the longitudinal direction and the transverse direction were changed so that the magnetic tape was obtained.
[0066]
[Table 1]

[0067]
As is apparent from Table 1, the present invention has excellent winding characteristics and transportability while exhibiting excellent electromagnetic conversion characteristics.
[0068]
【The invention's effect】
According to the present invention, a laminated biaxially oriented polyester film having excellent electromagnetic conversion properties and excellent properties such as winding property and transportability can be obtained. This polyester film is useful as a base film for magnetic recording media, particularly as a base film for magnetic tapes such as ½ inch video tape, 8 mm video tape, data cartridge tape, and digital video tape.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view schematically showing the occurrence of irregularities when a film is wound into a roll.
FIG. 2 is a schematic explanatory view for determining the occurrence of film vertical wrinkles and the ratio thereof.

Claims (10)

A laminated biaxially oriented polyester film obtained by laminating a polyester A layer on a polyester B layer and satisfying the following requirements (1) to (4) .
(1) The polyester A layer contains at least two kinds of lubricants I and II having different average particle diameters, and the average particle diameter (D ₁ ) of the lubricant I is 0.2 μm or more and less than 0.4 μm. the average particle diameter _{(D 1)} and the difference between the average particle diameter of the lubricant _{II (D 2) (D 1} -D 2) is 0.1 to 0.2 [mu] m, the content of the lubricant I 0.15 ~0 of. 4% by weight and the content of lubricant II is 0.1 to 0.8% by weight.
(2) The polyester B layer contains a lubricant having an average particle size of 0.05 to 0.2 μm and a content of 0.005 to 0.1% by weight.
(3) The surface roughness WRa of the polyester A layer is 4 to 6 nm, the total number of protrusions is 1 × 10 ⁴ / mm ² or more, the protrusion height is 20 to 50 nm when the cumulative number of protrusions is 30 / mm ² , polyester B The protrusion height when the surface roughness WRa of the layer is 0.5 to 2 nm and the cumulative number of protrusions is 30 / mm ² is 20 nm or less.
(4) The film friction coefficient is 0.4 or less.   The laminated biaxially oriented polyester film according to claim 1, wherein the lubricants I and II contained in the polyester A layer are spherical inert particles.   The laminated biaxially oriented polyester film according to claim 1 or 2, wherein the lubricants I and II contained in the polyester A layer are spherical silica.   The laminated biaxially oriented polyester film according to any one of claims 1 to 3, wherein the polyester A layer contains a lubricant III having a smaller average particle diameter than the lubricants I and II.   The laminated biaxially oriented polyester film according to claim 1, wherein the lubricant contained in the polyester B layer is a spherical inert particle.   The laminated biaxially oriented polyester film according to claim 1 or 5, wherein the lubricant contained in the polyester B layer is spherical silica. The longitudinal Young's modulus is 500 to 1,000 kg / mm ² , the transverse Young's modulus is 500 to 1,400 kg / mm ² , and the sum of the longitudinal and lateral Young's moduli is 1,300 to 2,000 kg / mm ^2. The laminated biaxially oriented polyester film according to any one of 1 to 6.   The laminated biaxially oriented polyester film according to claim 7, wherein the transverse Young's modulus is higher than the longitudinal Young's modulus.   The laminated biaxially oriented polyester film according to claim 7 or 8, wherein the polyester A layer and the polyester B layer are polyethylene-2,6-naphthalate films.   The laminated biaxially oriented polyester film according to any one of claims 1 to 9, which is used for a digital recording magnetic recording medium.

Images