JP2004030809A - Substrate for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate capable of manufacturing a high density magnetic recording medium excellent in thickness homogeneity, physical property uniformity in width direction, size stability, and rigidity, causing less track deviation for even storage for a long time under a high temperature and a high humidity environment in particular, and exhibiting excellence in running durability, size stability and electromagnetic transducing performance, and to provide the magnetic recording medium. <P>SOLUTION: This invention provides the magnetic recording medium with a magnetic layer formed on one side of a biaxial orientation polyester film substrate with a rate of change in width a[=ä(A<SB>1</SB>-B<SB>1</SB>)/A<SB>1</SB>}×100] of 0.01 to 0.06%, wherein A<SB>1</SB>is a width at a 10MPa load in the length direction and B<SB>1</SB>is a width at a 20MPa load in the length direction. This invention also provides the magnetic recording medium substrate of the biaxial orientation polyester film that exhibits a rate of change in width c[=ä(A<SB>3</SB>-B<SB>3</SB>)/A<SB>3</SB>}×100] of 0.01 to 0.075%, wherein A<SB>3</SB>is a width at a 10MPa load in the length direction and B<SB>3</SB>is a width at a 20MPa load in the length direction, thickness unevenness in the length direction of 1 to 5%, and a ratio of a maximum minimum difference x in a width direction orientation angle to a width L is 0 to 15°/m. <P>COPYRIGHT: (C)2004,JPO

Description

【０１０１】
【表２】

【０１０２】
【発明の効果】
本発明による磁気記録媒体は、高温高湿下で長時間保管してもトラックずれが少なく、走行耐久性、寸法安定性に優れ、良好な電磁変換性を示すことができるものであり、高密度磁気記録媒体として好適なものである。また、本発明による磁気記録媒体用支持体は、厚み均質性、幅方向物性均一性、寸法安定性、剛性に優れた支持体であり、特に磁気記録媒体用に好適なものである。
【図面の簡単な説明】
【図１】アヤハエンジニアリング製シート幅測定器等を用いて支持体サンプル等の幅を測定する場合の概略をモデル的に示す図である。
【符号の説明】
１：固定クリップ
２：レーザーセンサー（長手方向測定用）
３：レーザーセンサー（幅方向測定用）
４：試料
５：ガラス板
６：回転ロール
７：重り（分銅）
８：ロードインジケーター（ＪＣ−５００）
９：レーザー寸法測定器（ＬＳ−５０００）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a magnetic recording medium having a magnetic layer having a magnetic layer exhibiting good trackability, excellent track durability and excellent dimensional stability even when stored for a long time under high temperature and high humidity, and having uniform thickness, The present invention relates to a support excellent in uniformity of physical properties in the width direction, dimensional stability, rigidity and the like and used for a magnetic recording medium such as a magnetic tape.
[0002]
[Prior art]
Biaxially stretched polyester films are used for various applications because of their excellent thermal properties, dimensional stability, mechanical properties, and ease of control of surface morphology, and their usefulness as a support for magnetic recording media is particularly important. It is well known. In recent years, magnetic tapes have been required to have higher densities in order to reduce the weight, size, and long-term recording of equipment. For high-density recording, it is useful to shorten the recording wavelength and downsize the recording signal. However, when the size of the recording signal is reduced, there is a problem that the recording track is likely to be displaced due to heat during the running of the magnetic tape and thermal deformation during storage of the tape. Accordingly, there is an increasing demand for improvements in properties such as thermal dimensional stability and storage stability in a tape usage environment. Further, in order to reduce the size of the recording signal, it is necessary to further reduce the thickness of the magnetic layer, but with this, the mechanical strength becomes insufficient, so that the film becomes weak and easily stretched, For example, problems such as susceptibility to tape damage and deterioration of head contact due to deterioration of electromagnetic conversion characteristics are likely to occur.
[0003]
Therefore, in the case of a thinned tape, it is desired to meet the above-mentioned requirement of dimensional stability and obtain compatibility (such as head contact and running property) with a conventional thick tape. An aromatic polyamide having high rigidity is used for the support in view of strength and dimensional stability. However, the amount of this aromatic polyamide film on the market at present is significantly smaller than that of a conventional polyester film, and there are many restrictions on the quantitative expansion of a metal thin film type magnetic recording medium using an aromatic polyamide film.
[0004]
On the other hand, polyethylene terephthalate (hereinafter, referred to as PET) and polyethylene naphthalate (hereinafter, referred to as PEN) have low rigidity as they are, and as a technique for increasing the strength of a biaxially stretched polyester film, there are two techniques, vertical and horizontal. A method in which the stretched film is stretched again in the machine direction to increase the strength in the machine direction (for example, JP-B-42-9270, JP-B-43-3040, JP-B-46-1119, JP-B-46-119). -1120, JP-A-50-133276, JP-A-55-22915, etc.) are known. However, the tape breaks during use, edge damage occurs due to insufficient rigidity in the width direction, dimensional changes due to stress elongation deformation or environmental conditions, the recording track shifts, errors occur during recording and reproduction, insufficient strength Therefore, problems such as difficulty in handling a thin film and obtaining desired electromagnetic conversion characteristics are likely to occur.
[0005]
Further, there is known a method of increasing the strength of a biaxially stretched polyester film by forming a metal-based reinforcing film on the film surface (JP-A-2000-11376, JP-A-11-33925, etc.). However, it is still difficult to satisfy all the strict requirements for high-density recording.
[0006]
As a technique for improving the dimensional stability of a biaxially oriented polyester film having high productivity, a biaxially oriented polyester film composed of polyethylene terephthalate and polyetherimide (for example, JP-A-2000-141475) is known. ing. However, even if the support for the magnetic recording medium has excellent dimensional stability, if the thickness unevenness is large or the physical properties in the width direction are non-uniform, as a result, the properties such as the dimensional stability and strength of the support are reduced. Since unevenness occurs, uneven application of the magnetic layer occurs during the processing step of the magnetic recording medium, and the dimensional stability in the environment of use as the magnetic recording medium is not sufficient. There are many issues to record in
[0007]
As described above, in the case of the conventional support, those satisfying important characteristics as a magnetic recording medium such as thickness uniformity, uniformity of physical properties in the width direction, dimensional stability, and rigidity have not been obtained. Many problems remain when applied to a density recording medium.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems, and in particular to a high-density magnetic recording medium having excellent running durability and dimensional stability and exhibiting good electromagnetic conversion properties, uniform thickness, uniform physical properties in the width direction, and dimensional stability. Another object of the present invention is to provide a magnetic recording medium support having excellent rigidity.
[0009]
[Means for Solving the Problems]
The magnetic recording medium of the present invention is obtained by providing a magnetic layer on at least one surface of a support made of a biaxially oriented polyester film and applying a load of 10 MPa in the longitudinal direction at 23 ° C. and 65% RH. Width (A₁) And the width when a load of 20 MPa is applied in the longitudinal direction (B₁), The width dimension change rate a determined by the following equation is 0.01 to 0.06%.
Width change rate a (%) = ｛(A₁-B₁) / A₁｝ × 100
[0010]
Further, the support for a magnetic recording medium of the present invention is a support for a magnetic recording medium made of a biaxially oriented polyester film, and has a load of 10 MPa in the longitudinal direction at 23 ° C. and 65% RH. Width (A₃) And the width when a load of 20 MPa is applied in the longitudinal direction (B₃) Is 0.01 to 0.075%, the thickness unevenness in the longitudinal direction of the film is 1 to 5%, and the maximum value and the minimum value of the orientation angle in the film width direction are determined. The ratio x / L of the difference x (゜) to the film width L (m) is 0 to 15 ゜ / m or less.
Width change rate c (%) =） (A₃-B₃) / A₃｝ × 100
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The polyester used in the present invention is a polyester containing an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid, or an aliphatic dicarboxylic acid and a diol as main components. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid , 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, etc., of which terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid can be preferably used. As the alicyclic dicarboxylic acid, for example, cyclohexanedicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid, for example, adipic acid, suberic acid, sebacic acid, dodecandioic acid and the like can be used. These acid components may be used alone or in combination of two or more. Further, an oxyacid such as hydroxyethoxybenzoic acid may be partially copolymerized.
[0012]
Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. , 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2'-bis (4 '-Β-hydroxyethoxyphenyl) propane and the like can be used. Among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like are particularly preferable, and ethylene glycol is particularly preferable. thing It can be. These diol components may be used alone or in combination of two or more. Among them, polyethylene terephthalate containing an ethylene terephthalate unit as a main component is preferable.
[0013]
In addition, other compounds such as polyfunctional compounds such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, 2,4-dioxybenzoic acid, lauryl alcohol, and phenyl isocyanate may be used as the polyester. You may copolymerize within the range which is linear.
[0014]
As the polyester of the present invention, polyethylene terephthalate, polyethylene-2,6-naphthalate, a copolymer thereof, and a modified product thereof are preferable.
[0015]
The polyester used in the present invention may contain polyetherimide in a range of 5 to 30% by weight. The polyetherimide used is a polymer containing an aliphatic, alicyclic or aromatic ether unit and a cyclic imide group as a repeating unit, and is not particularly limited as long as it is a polymer having melt moldability. For example, US Pat. Nos. 4,141,927, 2,622,678, 2,606,912, 2,606,914, 2,596,565, 2,596,566, 2,598,478, polyetherimides, 2,598,536, and 2,599,171. Japanese Patent Application Laid-Open No. 9-48852, Japanese Patent No. 2565556, Japanese Patent No. 2564636, Japanese Patent No. 25664637, Japanese Patent No. 25656348, Japanese Patent No. 25663547, Japanese Patent No. 2558341, Japanese Patent No. 2558339, and Japanese Patent No. 2834580. It is a polymer of description. As long as the effects of the present invention are not impaired, the main chain of the polyetherimide contains cyclic imides, structural units other than ether units, for example, aromatic, aliphatic, alicyclic ester units, oxycarbonyl units and the like. May be. In the present invention, polyetherimide having a glass transition temperature of 350 ° C. or lower, more preferably 250 ° C. or lower is preferable, and 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m -Condensates with phenylenediamine or p-phenylenediamine are most preferred from the viewpoint of compatibility with polyester, cost, melt moldability and the like. This polyetherimide is available from General @ Electric under the trade name "Ultem" (registered trademark).
[0016]
The biaxially oriented polyester film in the present invention preferably contains inert particles. Examples of the inert particles include clay, mica, titanium oxide, calcium carbonate, kaolin, talc, wet or dry silica, colloidal silica, inorganic particles such as calcium phosphate, barium sulfate, aluminum silicate, alumina and zirconia, and acrylic acid. And organic particles containing styrene or the like as a component, and so-called internal particles that are precipitated by a catalyst or the like added during the polyester polymerization reaction. Among these, crosslinked polymer particles, alumina, spherical silica, and aluminum silicate are particularly preferred.
[0017]
The biaxially oriented polyester film in the present invention is within a range that does not impair the effects of the present invention, and various other additives such as a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment, and a dye. And organic lubricants such as fatty acid esters and waxes.
[0018]
The magnetic recording medium of the present invention is provided with a magnetic layer on at least one surface of a support made of a biaxially oriented polyester film, and is subjected to a load of 10 MPa in the longitudinal direction at 23 ° C. and 65% RH. Width dimension (A₁) And the width when a load of 20 MPa is applied in the longitudinal direction (B₁) Is 0.01 to 0.06%, preferably 0.01 to 0.05%, and more preferably 0.01 to 0.04. is there.
Width change rate a (%) = ｛(A₁-B₁) / A₁｝ × 100
[0019]
If the width dimensional change rate a exceeds 0.06%, when the recording medium is expanded in the longitudinal direction by the tension in the tape drive in the longitudinal direction, it contracts in the width direction due to the elongation deformation, and the recording track shifts. Is easy to occur. Furthermore, due to frequent occurrence of dropouts, storage stability of data is deteriorated, and electromagnetic conversion characteristics are deteriorated. Further, when the width dimension change rate a is less than 0.01%, it is a region that is difficult to reach with a magnetic recording medium using polyester as a support. Here, the width dimension change rate a is a value obtained by a measuring method described later.
[0020]
Further, the magnetic recording medium of the present invention has a width (A) before processing for 72 hours under a condition of 49 ° C. and 90% RH with a load of 32 MPa applied in the longitudinal direction.₂) And the width dimension after the treatment (B₂), The dimensional change b (%) determined by the following equation is preferably in the range of 0 to 0.4%, more preferably 0 to 0.35%, and still more preferably 0 to 0.3%. %.
Width change rate b (%) = ｛(A₂-B₂) / A₂｝ × 100
When the dimensional change rate b is out of the range of 0 to 0.4%, the running durability of the tape deteriorates, the dropout frequently occurs, and the storage stability of data under high temperature and high humidity tends to deteriorate.
[0021]
Further, the support for a magnetic recording medium of the present invention is a support for a magnetic recording medium made of a biaxially oriented polyester film, and has a load of 10 MPa in the longitudinal direction at 23 ° C. and 65% RH. Width (A₃) And the width when a load of 20 MPa is applied in the longitudinal direction (B₃), The width dimensional change c obtained by the following equation is 0.01 to 0.075%, the thickness unevenness in the longitudinal direction and the width direction is 1 to 5%, and the orientation angle in the film width direction is The ratio x / L of the difference x (゜) between the maximum value and the minimum value to the film width L (m) is 0 to 15 ゜ / m.
Width change rate c (%) =） (A₃-B₃) / A₃｝ × 100
Here, the width dimension change rate c and the difference x between the maximum value and the minimum value of the orientation angle are values obtained by a measurement method described later.
[0022]
The width dimension change rate c is preferably 0.01 to 0.06%, and more preferably 0.01 to 0.05%. The thickness unevenness is preferably 1 to 4%, more preferably 1 to 3%, and x / L is preferably 0 to 10 ° / m, and more preferably 0 to 5 ° / m. It is. When the width dimension change rate c exceeds 0.075%, the width dimension tends to shrink during processing into a tape, and the dimensional stability is deteriorated. In addition, when used as a magnetic recording medium, data storability also deteriorates, such as deterioration of tape running properties and frequent occurrence of dropouts. On the other hand, the width dimensional stability c of less than 0.01% is a region that is difficult to reach when polyester is used as the support. On the other hand, if the thickness unevenness exceeds the above range, uneven coating of the magnetic layer is liable to occur. In particular, in the case of a multi-head of a linear tape, the contact at the end head is weakened, which causes PES noise. Further, when the thickness unevenness and x / L exceed the above range, the unevenness of the physical properties causes unevenness in the dimensional change rate, and as a result, the width dimensional change rate c is out of the above range, The number of parts that cannot be commercialized increases, which causes a deterioration in yield. On the other hand, when the width dimensional change rate c, thickness unevenness, and x / L of the magnetic recording medium support are all within the above ranges, the width dimensional change rate a of the magnetic recording medium is easily set to the above range. This is effective in obtaining a magnetic recording medium having excellent dimensional stability.
[0023]
In addition, the support of the present invention had a width (A) before being treated for 72 hours under a condition of 49 ° C. and 90% RH with a load of 32 MPa applied in the longitudinal direction.₄) And the width dimension after the treatment (B₄) Is preferably in the range of 0 to 0.3%. It is more preferably in the range of 0 to 0.25%, most preferably in the range of 0 to 0.2%.
Width change rate d (%) =） (A₄-B₄) / A₄｝ × 100
When the width dimension change rate d exceeds the above range, wrinkles easily occur during tape processing, which is not preferable. Further, when the thickness is less than the above range, shrinkage in the width direction is apt to occur during tape processing, dimensional stability is deteriorated, running durability of the tape is deteriorated, data storage property such as frequent occurrence of dropout is liable to deteriorate. .
[0024]
Further, it is preferable that the elastic modulus in the longitudinal direction of the support of the present invention is 6 to 15 GPa, and the sum of the elastic modulus in the longitudinal direction and the elastic modulus in the width direction is 10 to 30 GPa. More preferably, the elastic modulus in the longitudinal direction is in the range of 7 to 14.5 GPa, most preferably in the range of 8 to 14 GPa, and the sum of the elastic moduli in the longitudinal direction and the width direction is more preferably 11 to 27 GPa, still more preferably 12 to 24 GPa. It is. When the elastic modulus in the longitudinal direction is less than the above range, the tape is easily extended in the longitudinal direction due to the tension in the longitudinal direction in the tape drive. easy. Furthermore, due to frequent dropouts, storage stability of data is deteriorated, and electromagnetic conversion characteristics are liable to deteriorate. On the other hand, if the elastic modulus in the longitudinal direction exceeds the above range, the tape is likely to break, or the Young's modulus in the width direction is insufficient, causing edge damage. Further, it is preferable that the sum of the elastic modulus in the longitudinal direction and the elastic modulus in the width direction is within the above range from the viewpoint of running durability, storage stability, and off-rack.
[0025]
The support of the present invention preferably has a total thickness of 2 to 8 μm, more preferably 3.5 to 6 μm.
[0026]
The surface roughness Ra of the surface A of the support of the present invention is preferably 1.5 to 20 nm, more preferably 2 to 15 nm, and still more preferably 3 to 8 nm. Here, the surface A indicates a surface on a side on which a magnetic layer is applied when a magnetic tape is formed. If the Ra of the surface A is less than the above range, the magnetic layer formed on the film surface A is too smooth, and digital linear tape (DLT), linear tape open (LTO), quarter inch cassette (QIC), digital video The magnetic layer is worn by the magnetic head during magnetic recording / reproducing with a data recording device such as a cassette (DVC). On the other hand, if the Ra of the surface A exceeds the above range, the magnetic layer becomes too rough, and the electromagnetic conversion characteristics of the magnetic tape deteriorate. In other words, by setting the Ra of the surface A within the above range, it is possible to minimize the wear of the magnetic layer by the magnetic head during recording / reproducing and to keep the electromagnetic conversion characteristics of the magnetic recording tape favorable.
[0027]
The surface roughness Ra of the surface B opposite to the surface A of the support of the present invention is preferably from 5 to 50 nm, more preferably from 6 to 30 nm, and even more preferably from 7 to 10 nm. Here, the surface B is a surface on the running surface side of the magnetic tape. By setting the Ra of the surface B within the above range, when the film is formed and then slit into a predetermined width, it is easy to collect a product having a good winding shape, and the magnetic layer is formed on the film surface A of the support. In the state where the film is wound up in a roll shape after the formation of the support, the roughness of the film surface B of the support is transferred to the surface A side, thereby making it possible to minimize the occurrence of undulating deformation in the magnetic layer.
[0028]
The average particle size of the inert particles contained in the biaxially stretched polyester film used in the present invention is preferably 0.001 to 2 μm, more preferably 0.005 to 1 μm, and still more preferably 0.01 to 0.5 μm. is there. If the average particle size of the inert particles is less than the above range, it does not play a role as a film surface projection, which is not preferable. On the other hand, if it exceeds the above range, it becomes unfavorable because it becomes coarse projections and easily falls off.
[0029]
Further, the content of the inert particles contained in the biaxially stretched polyester film used in the present invention is preferably 0.01 to 3% by weight, more preferably 0.02 to 1% by weight, and further preferably 0.1 to 1% by weight. 0.5 to 0.5% by weight. If the content of the inert particles is less than the above range, it is not preferable because the running characteristics of the film are not effective. On the other hand, if it exceeds the above range, it is not preferable because it aggregates and becomes coarse projections and easily falls off.
[0030]
Further, in the present invention, it is particularly preferable to adopt a two-layer structure in which a film layer having a role of improving the running property and the handling property of the film is laminated on one side of the base layer portion of the film. Note that the base layer portion is a layer having the largest thickness in the layer thickness, and the other portion is a laminated portion. Physical properties such as elastic modulus and dimensional stability, which are important for magnetic material applications, are determined mainly by the physical properties of the base layer. When the relationship between the average particle size d (nm) of the inactive particles and the thickness t (nm) of the two-layer structure film is 0.2d ≦ t ≦ 10d, the laminated portion is uniform. This is preferable because a projection having a height can be obtained.
[0031]
The support made of the biaxially oriented polyester film of the present invention is not particularly limited, but has a creep compliance after a lapse of 30 minutes at a temperature of 50 ° C. and a load of 28 MPa of 0.11 to 0.4 GPa.^-1It is preferable that If the creep compliance exceeds the above range, it is not preferable from the viewpoints of suppressing elongation deformation of the magnetic tape caused by tension during running or storage of the magnetic tape, and suppressing track deviation during recording / reproducing. On the other hand, if it is less than the above range, it is not preferable from the viewpoint of suppressing magnetic tape breakage. The creep compliance is more preferably 0.13 to 0.35 GPa.^-1, Most preferably 0.15 to 0.30 GPa^-1Range.
[0032]
By providing a magnetic layer on the surface A side of the magnetic recording medium support of the present invention, a magnetic recording medium can be manufactured.
[0033]
Preferable examples of the magnetic layer include a magnetic layer in which a ferromagnetic metal thin film or a ferromagnetic metal fine powder is dispersed in a binder. As the ferromagnetic metal thin film, iron, cobalt, nickel and other alloys are preferable. Further, as the ferromagnetic metal fine powder, ferromagnetic hexagonal ferrite fine powder, iron, cobalt, nickel and other alloys are preferable. As the binder, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used. Examples of the thermoplastic resin include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, and vinyl ether. There are a polymer or a copolymer, a polyurethane resin, and various rubber-based resins which are contained as a simple substance. Further, as a thermoplastic resin or a reactive resin, phenolic resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic-based reactive resin, formaldehyde resin, silicone resin, epoxy-polyamide resin, polyester resin and A mixture of an isocyanate prepolymer, a mixture of a polyurethane and a polyisocyanate, and the like can be given. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. It is also possible to use a known electron beam-curable resin.
[0034]
The magnetic layer is formed by kneading the magnetic powder with a polymer (binder) such as thermoplastic, thermosetting, or radiation curable, applying, drying, and calendering, and depositing a metal or alloy. Any of dry methods in which a magnetic metal thin film layer is directly formed on a substrate film by a method, a sputtering method, an ion pre-coating method, or the like can be adopted.
[0035]
In the magnetic recording medium of the present invention, a protective film may be provided on the ferromagnetic metal film. With this protective film, running durability and corrosion resistance can be further improved. Examples of the protective film include oxide protective films such as silica, alumina, titania, zirconia, cobalt oxide, and nickel oxide; nitride protective films such as titanium nitride, silicon nitride, and boron nitride; silicon carbide, chromium carbide, and boron carbide. Examples of the protective film include a carbon protective film made of carbon such as a carbide protective film, graphite, and amorphous carbon. The carbon protective film is a carbon film made of an amorphous structure, a graphite structure, a diamond structure, or a mixture thereof formed by a plasma CVD method, a sputtering method, or the like, and is particularly preferably a hard carbon film generally called diamond-like carbon. . Further, the surface of the hard carbon protective film may be subjected to a surface treatment with an oxidizing or inert gas plasma for the purpose of further improving the adhesion with the lubricant provided on the hard carbon protective film.
[0036]
Further, after applying the magnetic layer to the support, it is effective and preferable to carry out a two-step curing treatment in order to keep the dimensional change rate a within the above-mentioned range. At this time, the first curing treatment is performed at (Tg-20 ° C.) to Tg for 12 to 24 hours, and then the second curing treatment is performed at Tg to (Tg + 10 ° C.) for 12 to 24 hours. It is more preferable that 1 cure processing temperature <2nd cure processing temperature.
[0037]
In the present invention, in order to improve the running durability and corrosion resistance of the magnetic recording medium, it is preferable to add a lubricant or a rust inhibitor to the magnetic film or the protective film.
[0038]
Next, the method for producing the support of the present invention will be specifically described, but the present invention is not limited to such an example.
[0039]
The polyester film used in the support of the present invention is a film obtained by subjecting a sheet obtained by melt-molding a polyester resin to sequential biaxial stretching and / or simultaneous biaxial stretching in the longitudinal direction and / or the width direction to stretch and orient the film. It can be obtained by successively stretching the film at a multi-step temperature and highly orienting the film.
[0040]
Hereinafter, an example in which a film made of polyethylene terephthalate (PET) is manufactured by a sequential biaxial stretching method will be described as a preferable manufacturing method.
[0041]
First, the high molecular weight polyethylene terephthalate used in the present invention is produced by a usual method, that is, any one of the following processes. That is, (1) a low molecular weight polyethylene terephthalate or oligomer is obtained by a direct esterification reaction using terephthalic acid and ethylene glycol as raw materials, and a high molecular weight polymer is obtained by a subsequent polycondensation reaction using antimony trioxide or a titanium compound as a catalyst. (2) Process of obtaining low molecular weight product by transesterification using dimethyl terephthalate and ethylene glycol as raw materials, and obtaining high molecular weight polymer by subsequent polycondensation reaction using antimony trioxide or titanium compound as catalyst (DMT method). Here, the esterification proceeds without a catalyst, but the transesterification reaction usually proceeds using a compound such as manganese, calcium, magnesium, zinc, lithium, or titanium as a catalyst. After substantial completion, a phosphorus compound may be added for the purpose of inactivating the catalyst used in the reaction.
[0042]
The PET pellets obtained by the above method are vacuum-dried at 180 ° C. for 3 hours or more, then heated to a temperature higher than the melting point of the polymer, then discharged quantitatively from a T-die die, and applied to a cooling drum while applying a high voltage. It is closely contacted and cooled to obtain an unstretched film. Here, in the present invention, in order to make the thickness unevenness of the finally obtained biaxially oriented polyester film 0.3 to 5%, for example, the draft ratio of the die (= lip lip gap / extruded sheet) Thickness) is preferably 1 to 15, more preferably 2 to 10, and more preferably 2 to 8. Furthermore, in the electrostatic application method, although a 0.15 mm diameter wire electrode is usually used, from the viewpoint of reducing thickness unevenness, a 0.10 mm diameter wire electrode is preferable, and a cross section is more preferably rectangular and uniform in the longitudinal direction. It is preferable to use a tape-shaped electrode having a form.
[0043]
Subsequently, the unstretched film is heated by a group of heating rolls in the range of Tg (glass transition temperature of polyester) to (Tg + 55 ° C.) and stretched 3 to 8 times in one step or multiple steps in the longitudinal direction, and 20 to 20 times. It cools with a 50 degreeC cooling roll group. At this time, in order to satisfy the Young's modulus of the present invention, the stretching speed in the longitudinal direction is set to 50,000 to 200,000% / min, and the first-stage stretching condition is set to 1. (Tg + 10 ° C.) to (Tg + 40 ° C.). 5 to 3 times, and subsequently, it is preferable to stretch 1.5 to 4.5 times in multiple stages in a temperature range of (first stage stretching temperature −40 ° C.) to (first stage stretching temperature −10 ° C.). . Subsequently, stretching in the lateral direction is performed. As a stretching method in the width direction, for example, a method using a stenter is generally used. The stretching temperature in the width direction is in the range of Tg to (Tm (melting point of polyester) -40 ° C.), and the magnification is 3 to 8 times (when performing vertical stretching again, the first stage stretching is 3 to 4.5 times). The stretching speed is preferably in the range of 2000 to 10000% / min. Further, re-longitudinal stretching and / or re-lateral stretching are performed as necessary. In this case, it is preferable that the stretching in the longitudinal direction is performed by a group of heating rolls at a temperature of Tg to (Tg + 70 ° C.) and the stretching ratio is 1.2 to 2.2 times. As a method of re-transverse stretching, a method using a tenter is preferable, and the temperature ゜ is preferably in a range of (Tm-140 ° C.) to (Tm-40 ° C.), and the stretching ratio is preferably in a range of 1.2 to 2.0 times. . Subsequently, the stretched film is heat-treated while being relaxed under tension or in the width direction. The heat treatment temperature in this case is (Tm-50 ° C) to (Tm-20 ° C), preferably (Tm-40 ° C) to (Tm-10 ° C), and the treatment time is in the range of 0.2 to 10 seconds. Is preferred. At this time, in order to make x / L of the obtained support 0 to 15 ° / m, after biaxially stretching the film, the film is once cooled to a glass transition temperature or lower, or the end of the film is A method in which a temperature gradient is set so as to be higher than the central portion, and a pre-heat treatment is performed while maintaining the temperature of the central portion at 90 ° C. or lower, and then a heat treatment is performed. It is preferable to use a method of performing a heat treatment so as to be higher than the temperature of the central portion by 10 ° C. or more.
[0044]
According to the method as described above, a support for a magnetic recording medium having excellent dimensional stability, thickness uniformity, uniformity of physical properties in the width direction, and rigidity can be obtained, and a problem or the like that occurs during manufacturing of the magnetic recording medium can be solved. .
[0045]
[Method of measuring physical properties and method of evaluating effects]
The method for measuring characteristic values and the method for evaluating effects are as follows. The longitudinal direction (MD) and the width direction (TD) when measuring the support for the magnetic recording medium are the same as the longitudinal direction and the width direction of the film constituting the support. The longitudinal direction (MD) and the width direction (TD) when measuring a magnetic recording medium other than a magnetic tape are the same as the longitudinal direction and the width direction of a film constituting a support in the recording medium.
[0046]
When measuring the width of the magnetic tape sample, the magnetic recording medium sample sampled in the tape shape, and the magnetic recording medium support sample sampled in the tape shape, the sheet width manufactured by Ayaha Engineering shown in FIG. The measurement is performed by the following method using a measuring device and a laser size measuring device (LS-5000) manufactured by Keyence Corporation.
[0047]
In FIG. 1, a sample (sample) 4 is fixed at one end by a fixing clip 1, a weight (weight) 7 is hung at the other end, and an intermediate portion thereof is hung over a rotating roll 6 and a glass plate 5. It is. A load indicator (JC-500) manufactured by KEYENCE CORPORATION is connected to the fixed clip 1 as a load cell. The width dimension is measured at the sample portion placed on the glass plate. Reference numeral 2 denotes a laser sensor for measuring in the longitudinal direction, reference numeral 3 denotes a laser sensor for measuring in the width direction, and reference numeral 9 denotes a main body of the laser dimension measuring device.
[0048]
The tape-shaped sample 4 is set on the sheet width measuring device shown in FIG. 1, and a weight (weight) 7 having a predetermined weight is suspended. The atmosphere at this time is an atmosphere of 23 ° C. and 65% RH. In order to apply the load as accurately as possible, the tension of the sample is finely adjusted so that the load displayed on the load cell connected to the fixing clip 1 becomes a predetermined load value, and the dimension in the width direction of the sample is read.
[0049]
(1) Width change rate a of a magnetic recording medium such as a magnetic tape
The length of the magnetic recording medium is defined as a sample length, and a sample slit in a tape shape having a sample length of 250 mm and a sample width of 1/2 inch is used. In the case of a magnetic tape having a tape width of less than 1/2 inch, a sample having a tape length and a sample length of 250 mm is used.
[0050]
Using the sheet width measuring device shown in FIG. 1, a weight (weight) 7 having a load of 10 MPa was applied to the sample after the humidity and temperature were controlled in an atmosphere of 23 ° C. and 65% RH for 24 hours. While suspended, measure the sample width dimension. Further, the sample width dimension is measured with the weight (weight) 7 suspended such that the load becomes 20 MPa. The width dimension change rate a is obtained by the following equation.
Width change rate a (%) = ｛(A₁-B₁) / A₁｝ × 100
Where A₁: Width (mm) when a load of 10 MPa is applied, B₁: Width (mm) when a load of 20 MPa is applied. In addition, five points were measured at random within a 10 m section in the longitudinal direction, and the maximum value at the five points was adopted.
[0051]
(2) Width change rate b of a magnetic recording medium such as a magnetic tape
The length of the magnetic recording medium is defined as a sample length, and a sample slit in a tape shape having a sample length of 250 mm and a sample width of 1/2 inch is used. In the case of a magnetic tape having a tape width of less than 1/2 inch, a sample having a tape length and a sample length of 250 mm is used.
[0052]
Using the sheet width measuring device shown in FIG. 1 described above, the sample was subjected to a humidity control at a temperature of 23 ° C. and an atmosphere of 65% RH for 24 hours.₂mm). Thereafter, the sample is left for 72 hours in a 49 ° C., 90% RH atmosphere with a load of 32 MPa applied in the longitudinal direction. After standing for 72 hours, the load was released, and the temperature and humidity were controlled at 23 ° C. and 65% RH for 24 hours.₂mm). The width dimension change rate b is determined by the following equation. The measurement was performed five times, and an average value of the five measurements was adopted.
Width change rate b (%) = ｛(A₂-B₂) / A₂｝ × 100
[0053]
(3) Width change rate c of magnetic recording medium support
Using a tape-shaped sample having a sample length of 250 mm and a sample width of 30 mm in the longitudinal direction, a grid of 20 × 20 mm is drawn in advance with an oil-based pen at a position where the dimensions can be read by a laser. The sample subjected to humidity control at 23 ° C. and 65% RH for 24 hours by the same apparatus and method as in the measurement of the width dimension change rate of the magnetic recording medium such as the magnetic tape is loaded with 10 MPa load. The sample width dimension at the time and the sample width dimension under the load of 20 MPa are measured, and the width dimension change rate c is obtained by the following equation.
Width change rate c (%) =） (A₃-B₃) / A₃｝ × 100
Where A₃: Width (mm) when a load of 10 MPa is applied, B₃: Width (mm) when a load of 20 MPa is applied. In addition, five points were randomly measured in a 10 m section in the longitudinal direction, and the maximum value at the five points was adopted.
[0054]
(4) Width change rate d of support for magnetic recording medium
In an atmosphere of 23 ° C. and 65% RH, a support sample having a sample length (film longitudinal direction) of 143 mm and a width of 31 mm was humidified and conditioned for 24 hours, and then placed on a chrome mask manufactured by Dai Nippon Printing Co., Ltd. At the center, a sample was stuck, and the width (A) was measured using an optical microscope.₄mm). Thereafter, the sample is left for 72 hours in a 49 ° C., 90% RH atmosphere with a load of 32 MPa applied in the longitudinal direction. After standing for 72 hours, the load was released, and the temperature and humidity were controlled at 23 ° C. and 65% RH for 24 hours.₄mm). The dimensional change rate in the width direction is obtained by the following equation. The measurement was performed five times, and an average value of the five measurements was adopted.
Width change rate d (%) =） (A₄-B₄) / A₄× 100｝
[0055]
(5) Uneven thickness of support for magnetic recording medium
Using a film thickness nest tester “KG601A” manufactured by Anritsu Corporation and an electronic micrometer “K306C”, the thickness of a support sample sampled at a length of 30 mm and a length of 10 m continuously in the longitudinal direction at a transport speed of 3 m / min. Measure. From this measurement result, the maximum value of the thickness at a length of 10 m was Tmax, the minimum value was Tmin, the average value of the thickness was Tave, R = Tmax−Tmin was determined, and the thickness unevenness (%) was determined from R and Tave by the following equation. .
Uneven thickness (%) = R / Tave × 100
[0056]
(6) x / L of support for magnetic recording medium
Using a polarizing microscope with white light as a light source, the narrow angle between the main alignment axis and the film width direction is determined from the extinction value, and this is defined as the alignment angle (°). This orientation angle is measured for the entire width in the film width direction, and the difference x (°) between the maximum value and the minimum value of the orientation angle in the film width direction is determined. The value x / L (° / m) of the ratio of the orientation angle difference x (°) to the film width L (m) is determined. The main orientation axis was 0 ° in the width direction and 90 ° in the direction (longitudinal direction) perpendicular to the width direction.
[0057]
(7) Elastic modulus of support for magnetic recording medium
According to the method specified in ASTM-D882, a sample having a width of 10 mm and a test length of 100 mm was sampled at a temperature of 23 ° C. and a humidity using an automatic film strength and elongation measuring device “Tensilon AMF / RTA-100” manufactured by Orientec Co., Ltd. The measurement was performed five times under the conditions of 65% RH and a tensile speed of 10 mm / min, and the average value was taken.
[0058]
(8) Total thickness of support and laminated thickness
Using a transmission electron microscope (H-600 manufactured by Hitachi, Ltd.), the cross section of the support was ultrathin section (RuO) at an acceleration voltage of 100 kV.₄(Staining). From the observation result of the interface, the total thickness and the lamination thickness are obtained. The magnification may be appropriately set according to the total thickness of the support to be determined and the lamination thickness, but generally, 1,000 times for the total thickness measurement and 10,000 to 100,000 times for the lamination thickness measurement are appropriate. .
[0059]
Further, the thickness of the laminate can be measured using a secondary ion mass spectrometer (SIMS). An element (M) originating from the highest concentration of particles among the inert particles in the film having a depth of 3000 nm from the surface layer.⁺) And the concentration ratio of the carbon element of the polyester (M⁺/ C⁺) Is analyzed by SIMS in the thickness direction from the surface to a depth of 3000 nm. In the surface layer, the element concentration due to the inert particles is low, and the element concentration due to the inert particles increases as the distance from the surface increases. In the case of the film of the present invention, the element concentration caused by the inert particles that have once reached a maximum value starts to decrease again. In this concentration distribution curve, the depth at which the element concentration caused by the inert particles is reduced to half of the maximum value is defined as the lamination thickness. The measurement conditions are as follows.
[0060]
1) Measuring device
Two-dimensional ion mass spectrometer (SIMS)
A-DIDA3000 manufactured by Atomika, West Germany
2) Measurement conditions
Primary ion species II: O₂ ⁺
Primary ion acceleration voltage: 12 KV
Primary ion current: 200 nA
Raster area: 400 μm □
Analysis area I: Gate 30%
Measurement vacuum degree: 5.0 × 10^-9Torr
E-GUN: 0.5KV-3.0A
[0061]
In the case where the inactive particles most contained in the range from the surface layer to the depth of 3000 nm are organic polymer particles, it is difficult to measure by SIMS. Therefore, XPS (X-ray photoelectron spectroscopy), IR (infrared A depth profile similar to the above can be measured by, for example, spectroscopy to determine the layer thickness.
[0062]
(9) Surface roughness Ra of the support
The center line average roughness Ra at a stylus tip radius of 0.5 m, a stylus load of 5 mg, a measurement length of 1 mm, and a cutoff value of 0.08 mm was measured using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The measurement is performed 20 times by scanning in the film width direction, and the average value is taken.
[0063]
(10) Thermal properties of polymer (glass transition temperature, melting point)
Specific heat measurement was performed under the following conditions using a differential scanning calorimeter using a robot DSC “RDC220” manufactured by Seiko Denshi Kogyo KK and a data analysis device using a disk station “SSC / 5200” manufactured by the company. The melting point (Tm) and the like were determined according to JIS K7121.
[0064]
Measurement condition
Heating temperature: 270-540K (RCS cooling method)
Temperature calibration: melting point of high purity indium and tin
Temperature modulation amplitude: ± 1K
Temperature modulation cycle: 60 seconds
Average heating rate: about 10mg
Sample weight: open aluminum container (33mg)
The glass transition temperature (Tg) was calculated by the following equation.
Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2
[0065]
(11) Support creep compliance
The support was sampled with a width of 4 mm and a test length of 15 mm, and was set on a TMA @ TM-3000 manufactured by Vacuum Riko Co., Ltd. and a heating control unit TA-1500, and the humidity and temperature were adjusted under the conditions of 50 ° C. and 65% RH. , The length of the sample film at that time is L₀(Μm). Thereafter, a load of 28 MPa is applied to the sample film, and the length of the sample film after holding for 30 minutes is L₁(Μm). From the amount of expansion and contraction of the sample film at this time, creep compliance was calculated from the following equation.
Creep compliance (GPa^-1) = ｛(L₁-L₀) / L₀｝ /0.028 The measurement was performed five times, and the average value of the five measurements was adopted. In addition, creep here is a phenomenon in which strain increases with time under a constant stress, and creep compliance is a ratio of this strain to a constant stress, and is described in "Introduction to Polymer Chemistry (Second Edition)". (Issued by Kagaku Doujin Co., Ltd.) p150.
[0066]
(12) Running durability and storage stability of magnetic tape
The magnetic recording medium was slit to a width of 1/2 inch, and a length of 670 m as a magnetic tape was assembled into a cassette to form a cassette tape. The cassette tape was run for 150 hours using Quantum DLT (IV) @Drive, and the running durability of the tape was evaluated according to the following criteria.
：: No tape end surface elongation, no bend, and no trace of scraping.
：: No tape end surface elongation or bending, but slight scraping marks.
Δ: The tape end face was not stretched, but was partially bent and scraping marks were observed.
×: A part of the tape end face is elongated, wakame-like deformation is observed, and scraping marks are observed.
[0067]
Also, after reading the data of the cassette tape prepared above using Dquant (IV) @Drive manufactured by Quantum, the cassette tape was stored in an atmosphere of 60 ° C. and 80% RH for 100 hours. The storage stability of the tape was evaluated according to the following criteria.
A: The tape was reproduced normally without a change in the tape width of 2 μm or less, without track deviation.
：: The tape width was changed more than 2 μm and was 4 μm or less, there was no track shift and the tape was reproduced normally.
Δ: The change in the tape width was more than 4 μm and 6 μm or less, there was no track deviation, and the tape was reproduced normally.
X: The change in the tape width exceeds 4 μm, and reading is impossible.
[0068]
(13) Electromagnetic conversion characteristics of magnetic tape (C / N)
The magnetic recording medium was slit into a width of 8 mm to prepare a pancake. Next, a 200 m-long magnetic tape was assembled from the pancake into a cassette to form a cassette tape.
[0069]
The magnetic tape was measured for C / N at 7 MHz ± 1 MHz using a commercially available VTR for Hi8 (EV-BS3000 manufactured by Sony Corporation). This C / N was compared with a commercially available MP video tape for Hi8 and ranked as follows.
：: +3 dB or more
Δ: +1 dB or more and less than +3 dB
×: less than +1 dB
[0070]
【Example】
Example 1
Polymerization by the DMT method was performed. That is, 0.1 part by weight of magnesium acetate tetrahydrate was added to 194 parts by weight of dimethyl terephthalate and 124 parts by weight of ethylene glycol, and a transesterification reaction was performed at 140 to 230 ° C. while distilling off methanol. Next, an ethylene glycol solution of 0.05 parts by weight of trimethyl phosphate and 0.05 parts by weight of antimony trioxide were added, and the mixture was stirred for 5 minutes. The resulting low polymer was stirred at 30 rpm, and the reaction system was heated to 230 ° C. The temperature was gradually raised to 290 ° C., and the pressure was lowered to 0.1 kPa. The time required to reach the final temperature and the final pressure was 60 minutes. When the polymerization reaction was carried out for 3 hours and the specified stirring torque was reached, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, and the polymerization product was discharged into cold water in the form of a strand, and immediately cut to produce a unique product. A pellet of polyethylene terephthalate having a viscosity of 0.65 was obtained.
[0071]
The thermal characteristics of the polyethylene terephthalate (PET) having an intrinsic viscosity of 0.65 obtained by the above method were measured by DSC, and were found to be Tg: 82 ° C and Tm: 256 ° C.
[0072]
Using this PET, a film was formed by the following method using two extruders (A, B).
The extruder A heated to 285 ° C. was charged with a raw material (A1) containing 0.1% by weight of silica having an average particle size of 0.07 μm in PET substantially containing no inert particles at 180 ° C. Supplied after vacuum drying for hours. The extruder B heated to 285 ° C. contains a raw material in which 0.5 wt% of crosslinked polystyrene having an average particle size of 0.3 μm is contained in PET having an intrinsic viscosity of 0.65 and substantially no inert particles. B1) was supplied after vacuum drying at 180 ° C. for 3 hours.
[0073]
Subsequently, the raw material (A1) was filtered in three stages in the order of a sand filter, a 1.2 μm cut fiber-sintered stainless steel metal filter, and a 0.8 μm cut fiber-sintered stainless steel metal filter. After filtering in two steps in the order of a filter and a fiber-sintered stainless steel metal filter cut at 3 μm, the polymer was joined with a T-die so that the temperature of the polymer became 285 ° C., and extruded from a die into a sheet. At this time, the draft ratio (= base lip gap / extruded sheet thickness) was 5, and the distance between the LDs (the distance between the base lip and the cooling drum) was 20 mm. Further, the sheet-shaped extruded polymer is adhered to a cast drum having a surface temperature of 25 ° C. by an electrostatic application method using a tape-shaped (0.04 mm in thickness, 7.2 mm in width) electrode, and cooled and solidified to form two layers. A laminated unstretched film (lamination thickness ratio A1 / B1 = 5/1) was produced.
[0074]
The obtained unstretched film is stretched at 115 ° C. in the longitudinal direction by 3.5 times using a roll peripheral speed difference by a roll-type stretching machine, and then stretched to 95 ° C. in the width direction by a stenter. The film was stretched 3.3 times, and further subjected to re-longitudinal stretching at 140 ° C. and 1.7 times using a roll longitudinal stretching machine, and then re-transversely stretched 1.3 times at 190 ° C. in a tenter. Thereafter, the film is heat-treated with a temperature gradient such that the center of the film is 210 ° C. and the end of the film is 10 ° C. higher than the center, and then relaxed at a cooling rate of 150 ° C. at a relaxation rate of 5% in the width direction. The film is further subjected to a relaxation treatment at a relaxation rate of 1% in the width direction in a zone of 100 ° C., and the film is gradually cooled to room temperature and wound up to produce a biaxially stretched polyester film having a thickness of 4 μm. A support for a recording medium was used. In addition, the film thickness was set to a desired level by adjusting the extrusion amount.
[0075]
On the surface A (surface of the layer of the raw material (A1)) of the obtained support, a magnetic paint and a non-magnetic lower layer paint having the following compositions are applied in multiple layers by an extrusion coater (the upper layer is made of a magnetic paint with a coating thickness of 0.1 μm). The thickness of the nonmagnetic lower layer was appropriately changed.), Magnetically oriented, and dried. Next, a back coat layer having the following composition was formed on the opposite surface (surface B side), and calendered at a temperature of 85 ° C. and a linear pressure of 200 kg / cm with a small test calender (steel / nylon roll, 5 steps). After a first cure at 60 ° C. for 24 hours, a second cure at 80 ° C. for 24 hours was performed to obtain a magnetic recording medium. The characteristics of the magnetic recording medium were evaluated using a magnetic tape slit to a width of 1/2 inch or 8 mm.
[0076]
(Composition of magnetic paint)
-Ferromagnetic metal powder: 100 parts by weight
-Modified vinyl chloride copolymer: 10 parts by weight
・ Modified polyurethane: 10 parts by weight
・ Polyisocyanate: 5 parts by weight
-Stearic acid: 1.5 parts by weight
・ Oleic acid: 1 part by weight
・ Carbon black: 1 part by weight
・ Alumina: 10 weight parts
・ Methyl ethyl ketone: 75 parts by weight
・ Cyclohexanone: 75 parts by weight
・ Toluene: 75 parts by weight
(Composition of back coat)
・ Carbon black (average particle size: 20 nm): 95 parts by weight
・ Carbon black (average particle size: 280 nm): $ 10 parts by weight
・ Α alumina: 0.1 parts by weight
-Modified polyurethane: 20 parts by weight
-Modified vinyl chloride copolymer: 30 parts by weight
・ Cyclohexanone: 200 parts by weight
・ Methyl ethyl ketone: 300 parts by weight
・ Toluene: 100 parts by weight
[0077]
Table 1 shows the physical properties of the obtained support. Table 2 shows the running durability, storage stability, and magnetic conversion characteristics of the magnetic tape as characteristics of the magnetic recording medium obtained from the support.
As shown in Tables 1 and 2, the obtained support was excellent in dimensional stability, and a magnetic tape excellent in running durability, storage stability and the like was obtained.
[0078]
Example 2
After preparing an unstretched film (lamination thickness ratio A1 / B1 = 5/1) in which two layers are laminated in the same manner as in Example 1, the unstretched film is firstly rolled by a roll-type stretching machine to obtain a difference in peripheral speed between rolls. The film is stretched 3.1 times at 115 ° C. in the longitudinal direction using a tenter, then stretched 3.52 times at 100 ° C. by a tenter, and further 150 ° C. and 1.53 times stretched using a roll stretching machine. After re-longitudinal stretching, the film was re-laterally stretched 1.53 times at 150 ° C. in a tenter. Thereafter, a heat treatment is performed with a temperature gradient such that the center of the film is 205 ° C. and the edge of the film is 10 ° C. higher than the center, and then relaxed in the cooling zone at 150 ° C. at a relaxation rate of 5% in the width direction. The film is further subjected to a relaxation treatment at a relaxation rate of 1% in the width direction in a zone at 100 ° C., and the film is gradually cooled to room temperature and wound up, and a 4 μm-thick biaxially stretched polyester film support for a magnetic recording medium is used. And In addition, the film thickness was set to a desired level by adjusting the extrusion amount.
[0079]
Using the obtained support, a magnetic recording medium was produced in the same manner as in Example 1. As shown in Tables 1 and 2, the dimensional stability of the obtained support was relatively good, and a magnetic tape having excellent storage stability and electromagnetic conversion characteristics could be obtained.
[0080]
Example 3
After preparing a 4 μm-thick film support in the same manner as in Example 2, the same procedure as in Example 1 was carried out except that the curing conditions after coating the magnetic layer on the support were changed to 60 ° C. for 48 hours. A magnetic recording medium was manufactured.
As shown in Tables 1 and 2, the obtained support has relatively excellent dimensional stability, excellent running durability, excellent storage stability, and a magnetic tape having relatively excellent electromagnetic conversion characteristics. Was.
[0081]
Comparative Example 1
The draft ratio at the time of extruding the raw material (A1) and the raw material (B1) from the die in Example 1 was changed to 20, and the tape-shaped electrode when the sheet was brought into close contact with the cooling drum by the electrostatic application method was replaced with a wire. Except for changing to an electrode (diameter: 0.15 mmφ), a two-layer unstretched film was prepared in the same manner as in Example 1, and then a 4 μm-thick film support was produced in the same manner as in Example 2. Using the obtained support, a magnetic recording medium was produced in the same manner as in Example 1.
As shown in Tables 1 and 2, the obtained support was a magnetic tape having poor dimensional stability and poor running durability and electromagnetic conversion characteristics.
[0082]
Comparative Example 2
The thickness of the film was 4 μm in the same manner as in Example 2 except that the heat treatment after re-transversely stretching the film in Example 2 was performed at 210 ° C. without applying a temperature gradient from the edge to the center of the film. A film support was prepared, and a magnetic recording medium was prepared in the same manner as in Example 1 using the obtained support.
As shown in Tables 1 and 2, the resulting support was a magnetic tape having poor dimensional stability and poor storage stability.
[0083]
Example 4
In the same manner as in Example 1, pellets of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.85 (Tg of 80 ° C.) were produced. 50% by weight of the PET pellets and 50% by weight of Polyetherimide (PEI) "Ultem" 1010 (Tg at 216 ° C) having an intrinsic viscosity of 0.68 manufactured by General Electric (GE) were heated to 290 ° C. The mixture was fed to a directional rotation type vent-type twin-screw kneading extruder to produce a blend chip (I) containing 50% by weight of PEI. The thermal characteristics of this blend chip (I) were measured using DSC, and it was found that Tg: 89 ° C. and Tm: 254 ° C.
[0084]
Next, using two extruders (A, B), a film was formed by the following method.
Extruder A heated to 295 ° C. contained 0.05% by weight of silica having an average particle size of 0.09 μm in polyethylene terephthalate (PET) having an intrinsic viscosity of 0.62 and containing substantially no inert particles. The mixed raw material (A1) obtained by dry-blending the pellet (II) and the blend chip (I) containing PEI at a ratio of 8: 2 was supplied after vacuum drying at 180 ° C. for 3 hours. The extruder B heated to 295 ° C. contains 0.5% by weight of calcium carbonate having an average particle diameter of 0.3 μm in polyethylene terephthalate (PET) having an intrinsic viscosity of 0.62 and containing substantially no inert particles. The mixed raw material (B1) obtained by dry-blending the blended pellet (III) and the blend chip (I) containing PEI at a ratio of 8: 2 was supplied after vacuum drying at 180 ° C. for 3 hours.
[0085]
Subsequently, the mixed raw material (A1) was filtered in three stages in the order of a sand filter, a 1.2 μm cut fiber-sintered stainless steel metal filter, and a 0.8 μm cut fiber-sintered stainless steel metal filter. Was filtered in two stages in the order of a sand filter and a fiber-sintered stainless steel metal filter having a cut of 3 μm, and then joined by a T-die so that the temperature of the polymer became 295 ° C., and extruded from a die into a sheet. At this time, the draft ratio (= base lip gap / extruded sheet thickness) was 5, and the distance between the LDs (the distance between the base lip and the cooling drum) was 20 mm. Further, the sheet-shaped extruded polymer is adhered to a cast drum having a surface temperature of 25 ° C. by an electrostatic application method using a tape-shaped (0.04 mm in thickness, 7.2 mm in width) electrode, and cooled and solidified to form two layers. A laminated unstretched film (lamination thickness ratio A1 / B1 = 5/1) was produced.
[0086]
The obtained unstretched film is stretched at 110 ° C. 3.1 times in the longitudinal direction using a peripheral speed difference of a roll by a roll-type stretching machine, and then stretched to 100 ° C. in the width direction by a stenter. The film was stretched 3.3 times, and further subjected to re-longitudinal stretching at 150 ° C. and 1.7 times using a roll longitudinal stretching machine, and then re-transversely stretched 1.3 times at 200 ° C. in a tenter. Thereafter, a heat treatment is performed with a temperature gradient such that the center of the film is 205 ° C. and the edge of the film is 10 ° C. higher than the center, and then relaxed in the cooling zone at 150 ° C. at a relaxation rate of 5% in the width direction. The film is further subjected to a relaxation treatment at a relaxation rate of 1% in the width direction in a zone at 100 ° C., and the film is gradually cooled to room temperature and wound up to produce a biaxially stretched film having a thickness of 4 μm, which is subjected to magnetic recording. The support was used as a medium. In addition, the film thickness was set to a desired level by adjusting the extrusion amount.
[0087]
On the surface A (surface of the layer of the mixed raw material (A1)) of the obtained support, the same magnetic paint and non-magnetic lower-layer paint as in Example 1 were applied in multiple layers by an extrusion coater (the upper layer was a magnetic paint, The coating thickness was 0.1 μm, and the thickness of the nonmagnetic lower layer was appropriately changed.), And the layer was magnetically oriented and dried. Next, a back coat layer similar to that of Example 1 was formed on the opposite surface (surface B side), and calendered at a temperature of 85 ° C. and a linear pressure of 200 kg / cm using a small test calender (steel / nylon roll, 5 steps). After the treatment, the first curing was performed at 60 ° C. for 24 hours, and the second curing was performed at 80 ° C. for 24 hours to obtain a magnetic recording medium. The characteristics were evaluated using a magnetic tape obtained by slitting this magnetic recording medium.
[0088]
As shown in Tables 1 and 2, the obtained support was excellent in dimensional stability, and a magnetic tape excellent in running durability, storage stability, and electromagnetic conversion characteristics could be obtained.
[0089]
Example 5
The polyethylene terephthalate in Example 1 was changed to polyethylene-2,6-naphthalenedicarboxylate (PEN), and a film was formed by the following method using two extruders (A, B). When the thermal characteristics of PEN were measured using DSC, it was Tg: 119 ° C and Tm: 261 ° C.
[0090]
The extruder A heated to 300 ° C. was charged with a raw material (A1) containing 0.05% by weight of silica having an average particle size of 0.09 μm in PEN containing substantially no inert particles at 180 ° C. Supplied after vacuum drying for hours. Further, the extruder B heated to 300 ° C. contains a raw material (PEN having an intrinsic viscosity of 0.65 containing substantially no inert particles and containing 0.5% by weight of calcium carbonate having an average particle size of 0.3 μm). B1) was supplied after vacuum drying at 180 ° C. for 3 hours.
[0091]
Subsequently, the raw material (A1) was filtered in three stages in the order of a sand filter, a 1.2 μm cut fiber-sintered stainless steel metal filter, and a 0.8 μm cut fiber-sintered stainless steel metal filter. After filtering at two stages in the order of a filter and a 3 μm-cut fiber sintered stainless metal filter, the polymers were joined by a T-die so that the temperature of the polymer became 255 ° C., and extruded from a die into a sheet. At this time, the draft ratio (= base lip gap / extruded sheet thickness) was 5, and the distance between the LDs (the distance between the base lip and the cooling drum) was 20 mm. Further, the sheet-shaped extruded polymer is adhered to a cast drum having a surface temperature of 25 ° C. by an electrostatic application method using a tape-shaped (0.04 mm in thickness, 7.2 mm in width) electrode, and cooled and solidified to form two layers. A laminated unstretched film (lamination thickness ratio A1 / B1 = 5/1) was produced.
[0092]
The obtained unstretched film is first stretched at 100 ° C. in the longitudinal direction by 3.5 times using a peripheral speed difference of the roll by a roll-type stretching machine, and then stretched at 100 ° C. in the width direction by a stenter. The film was stretched 3.5 times, further stretched again at 145 ° C. and 1.4 times using a roll longitudinal stretching machine, and then transversely stretched 1.4 times at 145 ° C. in a tenter. Thereafter, the film is heat-treated with a temperature gradient such that the center of the film is 210 ° C. and the end of the film is 10 ° C. higher than the center, and then relaxed at a cooling rate of 150 ° C. at a relaxation rate of 5% in the width direction. The film is further subjected to a relaxation treatment at a relaxation rate of 1% in the width direction in a zone of 100 ° C., and the film is gradually cooled to room temperature and wound up to produce a biaxially stretched polyester film having a thickness of 4 μm. A support for a recording medium was used. The film thickness was set to a desired level by adjusting the extrusion amount.
[0093]
On the surface A (the surface of the layer of the raw material (A1)) of the obtained support, the same magnetic paint and non-magnetic lower layer paint as in Example 1 were applied in multiple layers by an extrusion coater (the upper layer was coated with a magnetic paint. The thickness of the nonmagnetic lower layer was changed as appropriate, and the layer was magnetically oriented and dried. Next, a back coat layer similar to that of Example 1 was formed on the opposite surface (surface B side), and calendered at a temperature of 85 ° C. and a linear pressure of 200 kg / cm using a small test calender (steel / nylon roll, 5 steps). After the treatment, the first curing was performed at 60 ° C. for 24 hours, and the second curing was performed at 80 ° C. for 24 hours to obtain a magnetic recording medium. The characteristics were evaluated using a magnetic tape obtained by slitting this magnetic recording medium.
[0094]
As shown in Tables 1 and 2, the dimensional stability of the obtained support was relatively good, and a magnetic tape having excellent electromagnetic conversion characteristics could be obtained.
[0095]
Comparative Example 3
The draft ratio at the time of extruding the raw material (A1) and the raw material (B1) from the die in Example 5 was changed to 20, and the tape-shaped electrode when the sheet was brought into close contact with the cooling drum by the electrostatic application method was replaced with a wire. A biaxially stretched polyester film having a thickness of 4 μm and a magnetic recording medium were produced in the same manner as in Example 5 except that the electrode (diameter: 0.15 mmφ) was changed.
As shown in Tables 1 and 2, the obtained support had poor dimensional stability, and was a magnetic tape having inferior running durability, storage stability, and electromagnetic conversion characteristics.
[0096]
Example 6
Biaxial stretching with a thickness of 4 μm in the same manner as in Example 1 except that the particles blended in the raw material (B1) in Example 1 were changed to contain 0.05% by weight of silica having an average particle size of 0.04 μm. A polyester film and a magnetic recording medium were produced.
As shown in Tables 1 and 2, the obtained support was excellent in dimensional stability and could be a magnetic tape excellent in storage stability.
[0097]
Example 7
Biaxial stretching with a thickness of 4 μm was performed in the same manner as in Example 1 except that the particles blended in the raw material (A1) in Example 1 were changed to contain 0.3% by weight of silica having an average particle diameter of 0.03 μm. A polyester film and a magnetic recording medium were produced.
As shown in Tables 1 and 2, the obtained support was excellent in dimensional stability and could be used as a magnetic tape excellent in storage stability.
[0098]
Example 8
The particles blended in the raw material (A1) in Example 1 were changed to contain 0.3% by weight of alumina having a particle diameter of 0.03 μm and 0.5% by weight of crosslinked polystyrene having a particle diameter of 0.4 μm. A biaxially stretched polyester film having a thickness of 4 μm and a magnetic recording medium were produced in the same manner as in Example 1 except for the above.
As shown in Tables 1 and 2, the obtained support was excellent in dimensional stability and could be a magnetic tape excellent in storage stability.
[0099]
Example 9
Biaxial with a thickness of 4 μm in the same manner as in Example 1 except that the particles blended in the raw material (B1) in Example 1 were changed to contain 0.5% by weight of calcium carbonate having an average particle diameter of 1.2 μm. A stretched polyester film and a magnetic recording medium were produced.
As shown in Tables 1 and 2, the obtained support was excellent in dimensional stability and could be a magnetic tape excellent in storage stability.
[0100]
[Table 1]

[0101]
[Table 2]

[0102]
【The invention's effect】
The magnetic recording medium according to the present invention has a small track shift even when stored under a high temperature and a high humidity for a long time, has excellent running durability and dimensional stability, and can exhibit good electromagnetic conversion properties. It is suitable as a magnetic recording medium. The support for a magnetic recording medium according to the present invention is a support excellent in thickness uniformity, uniformity in physical properties in the width direction, dimensional stability, and rigidity, and is particularly suitable for a magnetic recording medium.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a case where a width of a support sample or the like is measured using a sheet width measuring device manufactured by Ayaha Engineering.
[Explanation of symbols]
1: Fixed clip
2: Laser sensor (for longitudinal measurement)
3: Laser sensor (for width measurement)
4: Sample
5: glass plate
6: rotating roll
7: Weight (weight)
8: Road indicator (JC-500)
9: Laser dimension measuring device (LS-5000)

Claims (8)

A magnetic layer is provided on at least one side of a support made of a biaxially oriented polyester film, and the width (A ₁ ) and the length when a load of 10 MPa is applied in the longitudinal direction at 23 ° C. and 65% RH. A magnetic recording medium characterized in that a width dimension change rate a obtained from the width dimension (B ₁ ) when a load of 20 MPa is applied in the direction is 0.01 to 0.06%.
Width change ratio a (%) = {(A ₁ −B ₁ ) / A ₁ } × 100 It is obtained from the width dimension (A ₂ ) before the treatment for 72 hours under a condition of 49 ° C. and 90% RH with a load of 32 MPa applied in the longitudinal direction under a load of 32 MPa and the width dimension (B ₂ ) after the treatment by the following formula. 2. The magnetic recording medium according to claim 1, wherein the width change rate b is in the range of 0 to 0.4%.
Width change rate b (%) = {(A ₂ −B ₂ ) / A ₂ } × 100 A support for a magnetic recording medium made of a biaxially oriented polyester film, the width (A ₃ ) when a load of 10 MPa is applied in the longitudinal direction and a load of 20 MPa in the longitudinal direction at 23 ° C. and 65% RH. The width dimension change rate c obtained from the width dimension (B ₃ ) obtained by the following equation is 0.01 to 0.075%, the thickness unevenness in the longitudinal direction of the film is 1 to 5%, and the film A support for a magnetic recording medium, wherein the ratio x / L of the difference x (゜) between the maximum value and the minimum value of the orientation angle in the width direction to the film width L (m) is 0 to 15 ° / m.
Width change rate c (%) = {(A ₃ −B ₃ ) / A ₃ } × 100 It is calculated from the width (A ₄ ) before the treatment for 72 hours under a load of 32 MPa in the longitudinal direction under the conditions of 49 ° C. and 90% RH under a load of 32 MPa and the width (B ₄ ) after the treatment by the following formula. 4. The support for a magnetic recording medium according to claim 3, wherein the width change rate d is in the range of 0 to 0.3%.
Width change rate d (%) = {(A ₄ −B ₄ ) / A ₄ } × 100 5. The magnetic recording medium according to claim 3, wherein the elastic modulus in the longitudinal direction is 6 to 15 GPa, and the sum of the elastic moduli in the longitudinal direction and the width direction is 10 to 30 GPa. Support. The magnetic recording medium support according to any one of claims 3 to 5, comprising polyethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, or a copolymer or modified product thereof. The total thickness is 2 to 8 μm, the surface roughness Ra of one surface A is 1.5 to 20 nm, and the surface roughness Ra of the other surface B is 5 to 50 nm. A support for a magnetic recording medium according to any one of the above. A magnetic recording medium according to claim 1, wherein a magnetic layer is formed on a surface A of the support for a magnetic recording medium according to claim 3. Manufacturing method.

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