JP2003016635A - Magnetic recording medium and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having the deformation level lower than that of a conventional medium and having a predictable deformation level by using a nonmagnetic supporting body having specified physical properties of the source material. SOLUTION: In the process of manufacturing the magnetic recording medium by preparing a film of a layered body having at least a magnetic layer applied on a nonmagnetic supporting body, the nonmagnetic supporting body used has <=1% thermal shrinkage during forming the film. The magnetic recording medium which uses the nonmagnetic supporting body having <=1% thermal shrinkage shows a low deformation level and can be repaired, whereas, a magnetic recording medium manufactured by using a nonmagnetic supporting body having >1% thermal shrinkage shows a significantly high deformation level and can not be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a magnetic layer formed on a non-magnetic support and a method for manufacturing the same, and more particularly to a magnetic recording medium which is hardly deformed even by heating film formation. The manufacturing method is related.

[0002]

2. Description of the Related Art In recent years, the spread of Internet lines has increased,
Infrastructure as an information transmission medium is being constructed on an international scale. In addition to the constant connection service for general households, which is becoming popular in the United States and South Korea, the amount of information such as voice and image information is increasing explosively, not limited to text information. A so-called storage system technological innovation for recording and reproducing such information is also urgently needed in society, and further improvement of each element characteristic such as storage capacity, transfer speed, reliability and miniaturization is required. In particular, a hard disk has achieved rapid improvement in storage density in recent years due to its ideal head media interface structure, and has established itself as a high-density storage device. The magnetic recording media of these hard disk devices are mainly those formed by film-forming various ferromagnetic materials by sputtering.
Recording and reproduction are performed by a magnetoresistive head such as R.

Regarding the production of the magnetic recording medium of the above-mentioned hard disk device, for example, Wang Tratorn, Magnetic.
It is described in Information Storage Technology. According to this document, as a general structure of a fixed magnetic disk, an underlayer, a magnetic layer, a protective layer,
And a lubricant layer is used. These hard substrates are made of Al-M having high hardness in order to meet the demand for high-speed rotation.
g alloy, glass, ceramics, or the like is used.
For example, in the case of an Al-Mg substrate, NiP is placed on the substrate.
By forming a plating layer and polishing them, errors caused by the substrate surface during recording and reproduction are reduced. In some cases, a fine machining texture is formed on the polished NiP surface. The texture is used to reduce the sticking phenomenon between the magnetic head and the magnetic disk called stiction. In addition, recently, by the texture selectively processed in the circumferential direction of the magnetic disk, the magnetostatic characteristics such as the coercive force, the squareness ratio, the coercive force squareness ratio, etc. are improved and the stability against thermal fluctuation is improved. There is an improving effect.

On this hard substrate, Cr or the like is formed as a base layer by a sputtering method. The crystal structure of Cr is a body-centered cubic lattice, and the mismatch between the (001) plane and the crystal lattice constant of the close-packed cubic lattice (11.0) plane of the Co-based alloy magnetic material described later is as small as 0.2%. . Therefore C
When the o-based alloy magnetic material is sputter-deposited on the Cr underlayer, the C-axis direction, which is the crystal easy axis direction, is oriented in the substrate surface, and as a result, it has characteristics as a longitudinal recording medium. . Since the film forming conditions of the Cr underlayer and the film forming conditions of the layer called the seed layer for controlling the crystal state of the underlayer have a great influence on the magnetic characteristics of the magnetic recording layer produced in the subsequent step, Research and development are done vigorously. On the other hand, while technological accumulation of the magnetic recording medium as described above is progressing, the innovation of the magnetic recording head plays a major role in contributing to the improvement of the recording density reaching 100% per year.
In particular, in recent years, a magnetoresistive magnetic head (AMR head) or a giant magnetoresistive magnetic head (GMR head) is becoming the mainstream of fixed disk devices in place of the conventional inductive head.

Next, the magnetic layer, which is the core technology of the magnetic recording medium, will be described. A CoCr-based alloy is often used in the magnetic layer, and Nb for increasing the coercive force Hc,
Ta, Pt, etc. are added, and Mo, W, etc. are added for the purpose of making particles fine [Naoe, Journal of Applied Magnetics, Vol. 24, p. 27 (2000)]. These so-called CoCr
In addition to the ternary medium called X, recently, a quaternary medium in which the number of additive elements is increased is also frequently used. These CoCr
In order to reduce the noise of the system medium, it is necessary to reduce the crystal grains grown as the magnetic layer and magnetically separate the grains. The CoCr-based magnetic medium is formed into a ferromagnetic region having a high Co density and excellent in crystallinity and a nonmagnetic region having a high Cr density by performing a phase separation (spinodal) by forming a film while heating the substrate to around 250 ° C. (Decomposition) to form nm-sized isolated magnetic domain groups.

[0006] In recent years, Co-containing gamma-iron oxide based sputter media have been studied as inexpensive magnetic recording media that are chemically stable and do not contain precious metals [eg Doi et al., Journal of Japan Society for Applied Magnetics, Volume 21]. 225 (1997), etc.]. In the case of these media, reactive sputtering film formation by oxygen is used to form Co-containing F
After the e target, in order to transform Fe ₃ O ₄ into γFe ₂ O ₃ , a post-oxidation step is performed at a temperature near 270 ° C. for about 1 to 24 hours. On the other hand, in recording media, the demand for so-called backup and archive, which saves increasing information at the lowest cost and in the smallest space, is increasing year by year. In this field, there is currently no technical option other than the tape medium, which has a high volume recording density and low cost, and as described above, the technology of the magnetic recording material regarding the high recording density accumulated in the hard disk is applied to the polymer film. It is expected to realize a magnetic recording tape with low noise and high recording density, which is applied to a non-magnetic support represented by.

Flexible thin-film magnetic recording media using these polymer films as supports have been proposed to be manufactured by several methods. For example, put the wound film together with the vacuum chamber, and feed the web while passing it over a large area sputtering target.
There is a web-conveying continuous film forming method of unwinding. However, as described above, substrate heating is indispensable for causing spinodal decomposition in a CoCr-based medium. In the case of an oxide film type medium using γFe ₂ O ₃ , high temperature post-oxidation is required after film formation.

[0008]

Therefore, it is difficult to reduce the noise of a CoCr-based medium with a conventional non-magnetic support made of a polymer film such as polyethylene terephthalate (PET), and the substrate is heated at around 250 ° C. or post-oxidized. Even if a high Tg material that can withstand high temperature, for example, a polymer support such as polyaramid or polyimide is used, tape damage may occur due to film deformation, etc., and the conventional fixed magnetic disk manufacturing method is used as it is. I can't. An object of the present invention is to use a non-magnetic support formed of a polymer film having a relatively low mechanical strength such as PET or a polymer film having a relatively high mechanical strength such as polyaramid to substantially prevent the deformation of the medium. To provide a magnetic recording medium that can be manufactured without causing such a problem and a manufacturing method thereof.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a magnetic recording medium produced by forming a laminated body in which a non-magnetic support having a preferable thickness of 3 μm to 10 μm is coated with at least a magnetic layer into a film. The heat shrinkage ratio of the non-magnetic support is 1
% Or less, and a non-magnetic support having a preferable thickness of 3 μm to 10 μm and at least a magnetic layer coated on the laminate, wherein the non-magnetic support has a heat shrinkage ratio of 1%. It is a method of manufacturing a magnetic recording medium, characterized in that the film is formed at the following temperature.

The present invention will be described in detail below. Materials such as PET, which are generally used as substrates for conventional magnetic recording media, have relatively weak mechanical strength, and heat contraction is strongly caused by heating during film formation, resulting in deformation and distortion, and thus magnetic recording. Performance deterioration as a medium was inevitable. In order to avoid this, a material with high mechanical strength such as polyaramid film is used, but when performing heating film formation by separately using multiple films that are commercially available as the same polyaramid film. However, the deformation level of the magnetic recording medium obtained may differ depending on the film used. Therefore, even if a relatively expensive polyaramid film is used, a magnetic recording medium of a satisfactory level may not be obtained, and if the deformation level cannot be grasped without film formation, the yield will decrease and efficient production will be possible. Cannot be done.

The present inventor has solved this drawback and predicted the deformation level of the obtained magnetic recording medium from the physical properties of the raw materials,
The inventors of the present invention have found that a magnetic recording medium having a predetermined deformation level can be obtained with high probability by forming a film on a magnetic recording medium using only raw materials that satisfy the conditions. Therefore, in the present invention, the non-magnetic support, the magnetic layer laminated on the non-magnetic support, the non-magnetic underlayer, and the protective layer, if necessary, at a temperature at which the thermal contraction rate of the non-magnetic support is 1% or less. A layer or the like is formed into a magnetic recording medium. This film formation may be performed at room temperature or under heating. The "heat shrinkage rate of the non-magnetic support" in the present invention means the ratio of the decrease in the length of the non-magnetic support to the original length when the non-magnetic support is heated at room temperature or a predetermined temperature. . This heat shrinkage rate is a specific value for a specific substance, and the heat shrinkage rate increases as the heating temperature rises. However, for example, even if they belong to the same polyaramid film category, the value of the heat shrinkage ratio may differ depending on the degree of polymerization and the production conditions.

A magnetic recording medium obtained by using a non-magnetic support having a heat shrinkage of 1% or less, and laminating a magnetic layer, and optionally an underlayer or a protective layer on the non-magnetic support ,
Substantial deformation does not occur, or even if it does occur, it is at a level where it can be repaired in a later process, and there is almost no reduction in yield. On the other hand, when a non-magnetic support having a heat shrinkage ratio of more than 1% is used, the deformation during film formation becomes large, and repair becomes impossible.

Next, each element of the magnetic recording medium of the present invention will be described. The non-magnetic support has a thermal shrinkage of 1%
There is no special limitation other than the following, any known material that can be used as a normal magnetic tape can be applied,
For example, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetramethylene phthalate, poly-1,4-cyclohexanedimethylene phthalate, polyethylene 2,6-naphthalene dicarboxylate, and polyethylene-p-oxobenzoate. Examples thereof include polyaramid and polyimide. PET and PEN are preferable from the viewpoint of easy availability of the material and good workability, but polyaramid and polyimide are suitable as the material having a desired heat shrinkage ratio.

The non-magnetic support may have a filler inside or on the surface thereof, and irregularities may be formed on the surface. Further, an inorganic undercoat layer such as silica may be formed on the surface.
The thickness of the non-magnetic support is not particularly limited, but it is 3-10 μm.
Is desirable. This is mainly intended for tape media applications, which provides the necessary and sufficient flexibility and mechanical strength when wound on a reel.
That is, if it is less than 3 μm, the necessary rigidity may not be ensured, and wrinkles are likely to occur on the non-magnetic support at the time of winding or unwinding the roll, and if it exceeds 10 μm, the film is thick. This is because it may not be possible to secure a sufficient winding length.

The non-magnetic support having such a structure may be directly coated with a magnetic layer, but it is preferable to form an underlayer. The underlayer is mainly composed of Cr or a Cr-based alloy, and the alloy contains Ti, Mo, Mn, Si, V, W and T.
It is preferable to contain 2 to 25 atomic% of a, Nb, P and the like. Further, a Ni-based alloy such as Ni or NiAl can be used as the underlayer. In some cases, these atoms or alloys may be reactively sputtered with nitrogen or oxygen. This underlayer is preferably sputtered as a polycrystalline film. For example, at a substrate temperature of 20 to 270 ° C., sputtering is performed at 0.1 to 20 Pa. This underlayer has a function of determining the crystal structure of the magnetic layer, and is preferably formed with low mobility.

As a material for the magnetic layer formed on the underlayer, it is preferable to use a Co-based alloy represented by CoCr, CoNi, CoCrX, CoNiX or the like.
The “X” atoms are in the range of 0 to 30 atomic%, Li, Si,
Ca, Yi, V, Cr, Ni, As, Y, Zr, Nb,
Mo, Ru, Rh, Ag, Pt, Ta, PtTa, Pt
B or TaB, etc., preferably Si, Ni, Cr,
Pt, Ta, PtTa, PtSi, PtB or the like,
More preferably Cr, Pt, Ta or Nb. In addition to these alloys, Co + γFe ₂ O ₃ and BaFe ₁₂ -2 × C
Oxide magnetic materials such as barium ferrite such as o × Ti × O ₁₉ and ferromagnetic metals such as Fe, Co and Ni are also used. Generally, the thickness of the magnetic layer is preferably 10 nm to 100 nm. If it is less than 10 nm, the coercive force may deteriorate.
If it exceeds, the crystal grain size becomes large and noise reduction may not be achieved. The metal magnetic layer may be a single layer film or a multilayer film.

It is desirable that this magnetic layer and the above-mentioned underlayer are formed by a vacuum thin film forming technique such as sputtering.
The technique includes a vacuum vapor deposition method of evaporating a metal magnetic material under vacuum and depositing it on a metal layer, an ion plating method of evaporating the metal magnetic material in a discharge, and an atmosphere containing argon as a main component. Among them, a so-called PVD technique such as a sputtering method in which atoms on the target surface are knocked out by argon ions generated by glow discharge is included. Of these vacuum thin film forming techniques, sputtering is preferably used in the present invention, and the sputtering gas is appropriately selected from Ar, Kr, Xe, etc., and Ar is particularly preferable.

When the film formation is carried out under heating, from 0.5 × Tg to the glass transition temperature (Tg) of the non-magnetic support,
The film can be preferably formed by heating at a temperature in the range of 0.9 × Tg. The heating time is almost proportional to the sputtering time,
Usually less than 1 minute. Further, as the non-magnetic support, the above-mentioned C
When using oCr and heating it to around 230 ° C at which CoCr causes phase separation, heat it up to around 180 ° C in advance,
After that, it may be heated up to around 230 ° C. by a heating roll. Heating may be post-oxidation, as in the case of oxide magnetic media, in which case 150 ° C to 400 ° C, preferably 250 ° C.
Heat at ℃ to 350 ℃ for 15 minutes to 24 hours. This post-oxidation is also used in the case of magnetic media that requires post-oxidation for magnetisation.

In the present invention, a protective layer can be formed on the surface of the magnetic layer. This protective layer is diamond-like carbon, graphite carbon, amorphous carbon,
WC, WMoC, ZrNbN, B ₄ C, SiO ₂ , ZrO
It is appropriately selected from among ₂ and the like, but it is particularly preferable to use diamond-like carbon. As carbon, those having a graphite structure, those having a diamond structure, and the like are known, and when Raman spectrum is measured, peaks derived from each are observed. The diamond-like carbon is a substance in which at least a part thereof has a diamond structure, and a peak derived from the diamond structure is observed in a Raman spectrum. Usually, a peak derived from the diamond structure appears together with a peak derived from the graphite structure.

This protective layer can be formed by a known vacuum film forming technique such as a plasma CVD method. This CV
The D method is a technique for decomposing a carbon compound or the like in plasma to form a film, which has excellent wear resistance, corrosion resistance, and surface coverage, and has a smooth surface shape and high electrical resistance. Carbon can be stably deposited to a thickness of 10 nm or less. In this case, as the carbon compound, known materials such as hydrocarbon-based, ketone-based, alcohol-based materials can be used. Further, a high frequency bias voltage is used to decompose in plasma. Also, when plasma is generated, A is used as a gas for promoting the decomposition of carbon compounds.
It may be introduced into the r and H _2.

In order to improve the film hardness and the corrosion resistance of diamond-like carbon, carbon may be in a state of reacting with nitrogen or fluorine, and the diamond-like carbon film may be a single layer or a multi-layer. Is also good. Further, when plasma is generated, in addition to carbon compounds, N ₂ , CHF ₃ , CH ₂ F ₂
The gas may be formed alone or in a state of being appropriately mixed. If the protective layer is too thick, the loss due to spacing increases, and if it is too thin, the wear resistance and corrosion resistance deteriorate. Therefore, the protective layer is formed to a thickness of 2 nm to 30 nm, preferably 5 nm to 10 nm.

A lubricant having a lubricating action can be applied to the outermost surface of the magnetic recording medium thus formed, for example, the surface of the magnetic layer or the protective layer. The lubricant used is
Hydrocarbon lubricants include carboxylic acids such as stearic acid and oleic acid, esters such as butyl stearate,
Preference is given to sulfonic acids such as octadecyl sulfonic acid, phosphoric acid esters such as monooctadecyl phosphate, alcohols such as stearic alcohol, amines such as stearylamine. Further, as the fluoride-based lubricant, a lubricant obtained by substituting a part or all of the alkyl groups of the above hydrocarbon-based lubricant with a fluoroalkyl group or a perfluoropolyether group is more preferable. The preferred thickness of the lubricant layer is 0.
It is from 5 nm to 4 nm. As the coating method, a known bar-type coating method, gravure coating method, dip coating method, spray coating method or the like can be adopted.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Next, examples of the magnetic recording medium according to the present invention will be described, but these do not limit the present invention.

The sputtering environment was set as follows. The sputtering apparatus was a disk-type triple sputter apparatus, and sputtering was performed by the RF sputtering method.
A polyaramid film as a polymer film was attached to a substrate jig and placed on a target. Then, the sputtering chamber was evacuated to 2 × 10 ⁻⁵ Pa by a rotary pump and a cryo-pump, and then Ar gas was introduced as a sputtering gas by a mass flow controller.

Example 1 A titanium underlayer having a thickness of 20 nm was formed on the polyaramid film (flexible non-magnetic support), which was a continuous web having a width of 127 mm and a thickness of 4.5 μm, and further thereon. To Co
The magnetic layer made of CrPt has a thickness of 50 nm,
The film was formed with an input power of 0 W. Then, a carbon protective layer was sputtered on the surface of the magnetic layer under the same conditions to obtain a magnetic recording medium. The sputtering pressure of Ar gas was set to 0.2 Pa. The magnetic recording medium on which film formation was completed was slit to a width of 6 mm, and then left in an annealing furnace in the atmosphere for 15 minutes to observe deformation of the film-formed tape. In order to make it easier to observe the degree of deformation of the tape, the tape was cut into pieces each having a width of about 2 cm, and the pieces were visually inspected, and evaluated in any of the following levels 1 to 4.

Level 1: No change is seen. Level 2: Some curl is seen. Level 3: Curl is badly adopted as a process. Level 4: The curl is extremely severe and cannot be adopted as a process.

In this embodiment, the heat shrinkage is 0.05%, 0.1
%, 0.3%, 0.5%, 1%, 2% and 5% of 6 types of polyaramid films are used, and the relationship between the heat shrinkage rate of each film and the deformation level of the magnetic recording medium after film formation is shown in Fig. 1. Indicated. As can be seen from FIG. 1, when the heat shrinkage rate was 0.1% or less, the deformation did not occur at the level 1. Further, when the heat shrinkage rate was 1% or less, the deformation was level 2, and there was no problem in using it in a normal process. However, when the heat shrinkage was 2% and 5%, the deformation was so bad that it could not be used as a magnetic recording medium. Heat shrinkage rate 0.1% (level 1), 1% (level 2), 2% (level 3) and 5%
Each (level 4) polyaramid was cut into a 2 cm × 6 mm test piece and heated at 250 ° C. for 60 minutes to cause twisting in each test piece. This test was repeated several times to examine the relationship between each deformation level and the number of twists. Level 1 was 0 times, level 2 was 0 to 2 times, and level 3 was 2 to 5 times.
At level 4 it was more than 5 times.

Example 2 Using the polyaramid films having the heat shrinkages of 0.3% and 2% at room temperature used in Example 1, the annealing temperature was set to 250.
A magnetic recording medium was obtained under the same conditions as in Example 1 except that the temperature was set at 0 ° C. The Tg point of polyaramid is 280 ° C., and the annealing temperature of 250 ° C. in this example corresponds to 0.9 × Tg. Also, as a result of actual measurement, the heat shrinkage rate of the polyaramid film having a heat shrinkage rate of 0.3% at room temperature at 250 ° C. is 0.3%, which is 1%.
It was below. The obtained results are shown in FIG. As shown in the figure, the magnetic recording medium using a non-magnetic support having a heat shrinkage of 2% could not be used due to the deformation of level 4, while the magnetic recording medium using a non-magnetic support having a heat shrinkage of 0.3% was used. The deformation of the recording medium was level 2, and although some curl was observed, it was repairable.

[0029]

INDUSTRIAL APPLICABILITY The present invention provides a magnetic recording medium produced by forming a laminated body in which a non-magnetic support is coated with a magnetic layer into a film, and the heat shrinkage rate of the non-magnetic support at the time of heating film formation is 1 % Or less, which is a magnetic recording medium. When a magnetic recording medium is formed into a film using a non-magnetic support having a heat shrinkage of 1% or less, there is substantially no deformation, or even if there is deformation, it can be relatively easily repaired. Therefore, the deformation level of the magnetic recording medium obtained from the physical properties of the raw material can be predicted, and the yield is improved by using only the raw material that can obtain the desired deformation level.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the heat shrinkage rate of each film and the deformation level of a magnetic recording medium after film formation in Example 1.

FIG. 2 is a graph showing the relationship between the heat shrinkage rate of each film and the deformation level of the magnetic recording medium after film formation in Example 2.

Claims (5)

[Claims] 1. A magnetic recording medium produced by coating a non-magnetic support with at least a magnetic layer, wherein the thermal shrinkage of the non-magnetic support during film formation is 1% or less. recoding media. 2. The non-magnetic support has a thickness of 3 μm to 10 μm.
The magnetic recording medium according to claim 1, wherein 3. A magnetic recording medium, comprising: forming a laminated body in which a non-magnetic support is coated with at least a magnetic layer at a temperature at which the thermal contraction rate of the non-magnetic support is 1% or less. Method. 4. The thickness of the non-magnetic support is 3 μm to 10 μm.
The method of manufacturing a magnetic recording medium according to claim 3, wherein 5. The film formation is performed while heating, and the heating film formation temperature is 0.5 of the glass transition temperature (Tg) of the non-magnetic support.
5. The method for manufacturing a magnetic recording medium according to claim 3, wherein the magnetic recording medium has a ratio of 0.9 times.