JPH097154A - Magnetic recording medium and magnetic recorder using the same - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium which has stable magnetic characteristics even if a substrate temp. is raised and is capable of executing a high- density recording by using a glass substrate of which the value satisfying a specific condition equation attains a specific value or above at the time of IR rays of a required wavelength are passed through the substrate. CONSTITUTION: This magnetic recording medium is obtd. by laminating a ground surface layer, magnetic layer and protective layer by vapor deposition on the glass substrate 1 which effectively absorbs IR rays to attain >=0.3[1/cm] in the value satisfying the conditions of the equation at the time of allowing the IR rays of the wavelength of 3μ to pass the substrate perpendicularly thereto via a heater 5 and has the thickness (d) ad reflectivity R stable to the temp. rise. Since such substrate 1 is used, the substrate 1 is stabilized even at the time of the temp. rise by heating, vapor deposition, etc., and the formation of magnetic layers having stable characteristics is possible. The magnetic recording medium which is capable of making high-density recording of >=1 giga bit per 1 square inch by using magnetoresistance(MR) elements, etc., and has the stable magnetic characteristics is obtd. In the equation, Io: the intensity of incident light, I: the intensity of transmitted light.

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 and a magnetic storage device using the same.

[0002]

2. Description of the Related Art With the progress of the information society, the amount of information handled on a daily basis is steadily increasing. Along with this, there is a strong demand for higher density and higher recording capacity for magnetic recording devices. When the density of a magnetic disk device, which is a typical magnetic recording device, is increased, in general, the reproduction output of a conventional electromagnetic induction type magnetic head is reduced, making reproduction difficult. Therefore, as described in JP-A-51-44917,
It is considered to use a magnetic head that utilizes a magnetoresistive effect that can obtain a high output even when the recording density is increased, by separating the recording magnetic head and the reproducing magnetic head. The magnetoresistive effect type magnetic head has a high reproduction output and a low head resistance, so that the thermal noise generated is small.

For this reason, the noise caused by the magnetic recording medium, which is conventionally hidden by the large noise generated from the electromagnetic induction type magnetic head, accounts for a large proportion of the noise of the entire apparatus. Therefore, in order to realize high recording density using the magnetoresistive magnetic head, it is necessary to reduce noise (medium noise) caused by the magnetic recording medium. Although it is necessary to increase the coercive force of the medium in order to reduce the medium noise, there is a problem that a sufficient coercive force cannot be obtained when a glass substrate having high impact resistance used for personal computers and the like is used.

On the other hand, in Japanese Patent Application No. 6-49090,
We proposed a method of forming a conductive film on a glass substrate and applying a bias voltage to it to form a magnetic film to secure the necessary coercive force. A method for applying a stable bias voltage over the entire surface of the disk has been shown.

[0005]

In the method of forming a film on a glass substrate, when the film is formed by raising the substrate temperature in order to reduce the medium noise, there are variations in the magnetic characteristics, and further, the magnetic characteristics in the plane of the magnetic disk. There was a problem that there was a distribution in.

An object of the present invention is to use a glass substrate, a magnetic recording medium suitable for high density recording which has stable magnetic characteristics even when the substrate temperature is raised, and a recording of 1 Gbit or more per square inch using the same. It is to provide a magnetic recording device that realizes a high density.

[0007]

The above object can be achieved by increasing the infrared absorption rate of the glass used for the substrate. In the magnetic recording device having the magnetic recording medium, the magnetic recording medium drive section, the magnetic head, the magnetic head drive section, and the recording / reproducing signal processing system, an MR is used as a reproducing magnetic head.
By using a (magnetoresistance) type or GMR (giant magnetoresistance) type magnetic head, it is possible to provide a magnetic recording device that realizes a recording density of 1 gigabit per square inch or more.

[0008]

The principle of the present invention will be described with reference to FIG. Incident light 2 (intensity Io) emitted from the heater 5 passes through the glass 1 having the thickness d and the refractive index n to become the transmitted light 3. At this time, the intensity of the transmitted light 3 (intensity I) is reflected 4 (reflectance R) when entering the glass 1 and when exiting the glass 1, and is further absorbed in the glass 1.

[0009]

## EQU1 ## I = Io (1-R) ² EXP (-Cd) (Equation 1) C is a constant. The amount of absorption in the glass 1 contributes to the temperature rise of the glass substrate.

[0010]

## EQU00002 ## Iabs = Io (1-R) (1-EXP (-Cd)) (Equation 2).

As a result of investigating the reason why the magnetic characteristics are unstable when the glass substrate is heated, the glass 1 used for the conventional substrate has a high infrared transmittance, so that the temperature rise is gentle even when the substrate is heated. We have come to the conclusion that variability will occur. Therefore, various methods of stably heating the glass substrate have been studied, and it has been found that increasing the infrared absorption rate of glass is effective. In particular, when the infrared absorption of the glass was remarkable at the peak of the infrared spectrum intensity of the heater 5, the heating time was short and stable heating could be realized.

FIG. 2 shows that the heater has 1 kW and 1.5 kW.
It shows the wavelength dependence of the infrared radiation intensity when the power is applied. 8 for each power
It can be approximated by blackbody radiation of 00K and 1000K. From the figure,
In either distribution, there is a peak at a wavelength of 3 to 3.5 μ, and it can be seen that it is important to effectively absorb infrared rays having this wavelength.

According to the equation (2), the constant C may be increased in order to increase the absorption rate. Using a normal heater,
In order to heat the substrate temperature from room temperature to about 300 ° C. in 1 minute, this value needs to be 0.3 [1 / cm] or more.

Co, Ni, C contained in the glass substrate
r, Fe, La, Y, Gd, Yb, Lu, Ce, Sm,
When the transition metal element such as Eu, Tb, Dy, Ho, or Tm is contained in an amount of 0.01 mol or more per liter, the above temperature rise can be obtained. However, even if it is contained in an amount of more than 0.5 mol per liter, the absorptivity does not increase so much, and rather the metal is reduced and the absorptivity becomes unstable, or it becomes difficult to form the surface strengthening layer. It's a problem.

B, P, and V are network-forming components of oxide glass, like Si, and easily replace Si to become the main component of glass. When B is 1 mol or more and less than 20 mols per liter, P is 0.5 mols or more and less than 10 mols per liter, and V is 0.1 mols or more and less than 5 mols per liter, a sufficient infrared absorption amount is obtained. To be In particular, when B is contained, the hardness is increased and the corrosion resistance is improved. further,
When the alkali component (network modification component) is reduced, the coefficient of thermal expansion is lowered. When B is included, the wavelength is 6 to 8 μ, P
Approximately 8μ when V is included and approximately 1μ when V is included
Infrared absorption peak occurs. The glass containing V is
It has a green color. Other components of the glass network include Ge and As, but the inclusion of these does not affect the effect of the present invention.

If Li is contained in the glass, Li-
Absorption based on the transition of mutual vibrational energy of O-bond has a wavelength of 4
It becomes easy to absorb infrared rays of ~ 7μ. If Li is 0.5 mol or more per liter, the absorptivity is sufficient for heating the substrate, but if it exceeds 10 mol, the glass becomes unstable,
Ingredients may precipitate.

Since the magnetic recording medium of the present invention can secure a sufficient and stable coercive force, by combining it with an ordinary inductive type reproducing magnetic head, 700 megabits per square inch or more, and further MR (magnetoresistive) type or GMR type. By combining with a (giant magnetic resistance) type magnetic head, it is possible to provide a magnetic recording device that realizes a recording density of 1 gigabit per square inch or more. Since the MR type or GMR type magnetic head has high sensitivity, noise is also generated from the head unless the value of the product Brt of the residual magnetic flux density Br measured in the head traveling direction and the total thickness t of the magnetic film is 100 Gμ or less. Will occur.

According to the present invention, since heating of the glass substrate is facilitated, the magnetic film for magneto-optical recording, which was conventionally formed on polycarbonate at room temperature, can be formed at high temperature.
The anisotropic magnetic field Hk can be increased. When Hk is high,
Since it is possible to form a small magnetization reversal region, by combining the magnetic recording medium of the present invention, the magnetic recording medium drive unit, the light generation unit and the detection unit, and the drive unit, the recording and reproduction signal processing system, It is possible to provide a magnetic recording device that realizes a recording density of 2 gigabits or more per square inch.

The present invention is effective for all processes in which a desired property is obtained by forming a film on a heated glass substrate.

[0020]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIG. First, as shown in the figure, a double-sided polished parallel plate tempered glass 1 having a thickness (d =) of 0.3 to 1 mm was arranged in parallel to the center of the facing heater 5, and a heating test was conducted. Electric power of 1.5 kW was applied to the heater 5, and variations due to the rate of temperature increase from room temperature and the thickness were examined (heating characteristic value). Table 1 shows the heating characteristic values of the plate glass having various compositions, and the absorption characteristic values are also shown.

However, the absorption characteristic value Ab is expressed by the formula Ab = (1) using the incident intensity Io and the transmission intensity I when infrared rays obtained by the filter and having a wavelength of 3 μ and a half value width of about 1 μ are made incident vertically. / D) loge (Io (1-R) ² / I). Among them, the reflectance R is obtained by measuring the refractive index n by the Pulfrich method, and using the formula R = (1-n) ² / (1+
Although it was obtained from n) ² , the refractive index may be measured by using a method other than n, or substantially the same value can be obtained by directly calculating the reflectance from the actual reflected light. At the beginning of Table 1, the heating characteristic values of the NiP-Al substrate generally used in magnetic disks at present are also shown. Conventional glass (Sample No.
In 1), since the absorption characteristic value Ab is as low as 0.1, the temperature rise is only about 10% that of the NiP-Al substrate.

[0022]

[Table 1]

From the table, when a small amount of Co is added to the composition of the conventional glass of sample No. 1 (samples No. 2 to 4), the heating characteristic value is remarkably improved, and the content of Co is 0.01 mol / liter. A temperature rise of 3 times was obtained. The absorption characteristic value Ab at this time is 0.3. When the amount of Co added is not so large, the degree of temperature rise increases in proportion to the amount added, but when it exceeds 0.5 mol / liter, it does not increase as much as the added amount, and the variation also increases. this is,
This is because the aggregation of metal ions occurs, and the influence of the oxidizing or reducing environment in the glass formation process is large.

Similarly, Ni (sample Nos. 5 to 7), Cr
Similar results were obtained even when 3d transition metal elements such as (Sample No. 8 to 10) and Fe (Sample No. 11 to 13) were added. In addition, La (Sample No. 14 to 16), Sm (Sample N
17-19), Y, Gd, Yb, Lu, Ce, Eu,
When a rare earth element such as Tb, Dy, Ho, or Tm is added, the degree of temperature rise is the same as when the 3d transition metal element is added, but the variation in the degree of temperature rise is reduced. This is mainly because 4f electrons are in the inner core, so that the influence of the oxidizing or reducing environment in the glass formation process is small.

Equivalent results were obtained with a combination of two or more transition metal elements, provided that the total amount of the transition metal elements added was 0.5 mol / liter or more. When Co is added, it is colored blue, when Ni is added, it is yellowish brown, when Cr is added, it is yellowish green, when Fe is added, it is colored bluish green to brown, and Sm, Ce, Eu, Tb, In the case of adding Dy, Ho and Tm, it became pale yellow. When Ce is contained, if a trace amount of Ti, V, Cu, or Ag is further contained, it seems that the color changes due to the irradiation of ultraviolet rays and the degree of temperature rise also changes. Further, Cl or S in the glass is 0.2 to 0.5 mol /
When it is contained in liters, the absorption of infrared rays increases, especially Fe
If is included, it will be several times. Further, when C is contained in the glass, it seems that the variation in the temperature rise degree is reduced.

Si, which is a glass network forming component, is
Even if it is replaced with P, V, etc. (Sample Nos. 20 to 22), the infrared absorption characteristics are improved. B is 1 mol or more per liter 20
If it is less than 0.5 mol, P is 0.5 mol or more and less than 10 mol per liter, and V is 0.1 mol or more and less than 5 mol per liter, a sufficient infrared absorption amount can be obtained. In particular, B
When included, the hardness increases and the corrosion resistance improves. Furthermore, when the alkali component (network modifying component) is reduced, the coefficient of thermal expansion is lowered. The glass containing V has a green color. At this time, when examining the wavelength dependence of the infrared absorption amount,
When B was contained, the wavelength was 6 to 8 μ, when P was contained, it was about 8 μ, and when V was contained, it was about 1 μ, which was the maximum. Ge, As and the like are also included in the glass network forming component, but the inclusion of these did not affect the effect of the present invention.

Even when Na, which is a component for modifying the network of glass, is replaced with Li (Sample No. 23), the infrared absorption characteristics are improved. If the amount of Li is 0.5 mol or more per liter, the absorptivity will be sufficient for heating the substrate, but if it is more than 10 mol, the glass will become unstable and components will precipitate. At this time, when the wavelength dependence of the infrared absorption amount was examined, it became the maximum at 4 to 7 μ.

Next, using Co-added sample No. 3 as the substrate glass 1, a multilayer magnetic recording medium as shown in FIG. 4 was prepared. Put the heater 5 shown in FIG.
After heating for 10 seconds with a power of W, the conductive film 10 and the magnetic film 1
3 and the protective film 16 were formed by a sputtering method, and a lubricating layer was further formed thereon. Here, the conductive film 10 is a Ta film having a thickness of 5 nm, and the magnetic film 13 has a thickness of 20.
nm Co-18 at% Cr-8 at% Pt + SiO ₂ alloy layer. The protective film 16 was made of carbon having a thickness of 20 nm. The lubricating layer is an adsorbent perfluoroalkyl ether. Argon was used as the sputtering gas in the entire film forming process, but if a rare gas such as neon, xenon, or krypton is used, the coercive force is increased by about 100 Oersted. If the oxygen plasma treatment is performed prior to the formation of the magnetic film 13, the coercive force of about 100 Oersted is further increased. Before forming the lubricating layer, Teflon fine particles may be attached onto the carbon protective film and plasma-etched to form a texture having a length of 10 nm. As the material of the magnetic film 13, instead of CoCrPt, CoCrPtTa, C
oPt, CoNi, CoFe, CoCr, CoIr, C
oW, CoRe, CoNiZr, CoCrTa, CoN
The same effect was obtained when iCr, SmCo or YCo was used.

The coercive force was within the range of 2150 to 2250 Oersted for all 100 continuously produced media. This is a conventional glass substrate (Sample No.
This is a good result as compared with 1800 to 2200 Oersted when 1) was used. Regarding heating, the conventional glass substrate achieves energy saving of 1/15 or less as compared with the case where a power of 5 kW was required for 30 seconds or more. For the substrate, in addition to Co-added sample No. 3, sample N
o.2 to 19 and other transition metals may be added. However, in this case, it is necessary to adjust the input power and the heating time in consideration of the temperature rise degree.

In this embodiment, an example in which NaO is used as the glass network modifying component is shown, but K and M are used instead of Na.
Even if an alkali metal such as g, Ca, or Ba, an alkaline earth metal, or a mixed component thereof is contained, the effect of the present invention is not hindered. However, it seems that devitrification occurs when the amount of Mg component is large.

The plate glass used in the present invention is chemically surface-strengthened, and the K composition in the range of 30 to 50 μm from the surface is larger than that in the interior. If the amount of Al as an intermediate component is small, this reinforcing layer cannot be thickened. Since the thickness of the reinforcing layer is sufficiently smaller than the thickness of the plate glass, the effect of the present invention is not hindered.

(Embodiment 2) Another embodiment of the present invention will be described below with reference to FIG. The magnetic recording medium of this embodiment is
As shown in the figure, the Ni-added sample No. 6 in Table 1 was further formed on both surfaces of the tempered glass substrate 1 to which a small amount of K, Mg, and Ca was added, by a sputtering method.
Cr conductive film 10, 30 nm-CrTi base film 12, 30
nm-Co-16 at% Cr-10 at% Pt-3 at
% Ta alloy magnetic film 13 and 20 nm-plasma C
Diamond-like carbon protective film 16 by VD,
Further, it is constituted by a lubricating layer formed thereon.
The lubricating layer is an adsorbent perfluoroalkyl ether. According to the X-ray diffraction method, it was found that the magnetic film was a hexagonal crystal and its c-axis was in the plane. The Cr conductive film 10 was formed by sputtering using a target larger than the substrate. At the time of forming the magnetic film 13, a bias voltage of −300 V was applied through the substrate holder 3. The diamond-like carbon protective film 16 was formed by a plasma CVD method using methane as a working gas. The glass substrate 1 was heated for 12 seconds by applying a power of 1 kW to the heater 5 shown in FIG. 3 before the sputtering film formation.

When the coercive force was measured by using the Kerr effect, the coercive force was in the range of 2900 to 3000 Oersted on both surfaces. If the glass substrate 1 is chamfered, variations in coercive force can be suppressed.

Next, the recording / reproducing characteristics were measured. Using a magnetic head that combines a recording electromagnetic induction thin-film magnetic head and a reproducing magnetoresistive magnetic head with a relative velocity between the medium and the magnetic head of 12 m / s, a floating spacing of 50 nm, and an effective gap length of 350 nm. evaluated. As a result, the medium noise is lower than that of the conventional glass substrate.
It was reduced by about 10%. Output half density (D50) is 1 compared to 80kFCI when using a conventional glass substrate.
It was improved to 20kFCI. As a result, it was found that recording / reproduction can be performed with a recording density exceeding 1 gigabit per 1 square inch.

(Embodiment 3) The medium shown in Embodiments 1 and 2 is used for four discs formed on both sides of a substrate and a reproducing section (giant).
7 composite type thin film magnetic heads with magnetoresistive effect and Ni
A magnetic recording device was manufactured in combination with a servo thin film head using a —Fe alloy as a recording / reproducing magnetic pole. As shown in FIG. 6, this apparatus comprises components such as a magnetic recording medium 101, a magnetic recording medium driving unit 102, a magnetic head 103, a magnetic head driving unit 105, and a recording / reproducing signal system 104. Using this magnetic recording device, levitating spacing 50
When the average time until the error occurred in nm was obtained, it was possible to prove that the reliability was high. Also, the magnetic recording device prototyped in this example has a low head flying height, so that the phase margin in recording and reproducing signals is widened, and the surface recording density is three times that of a conventional flying spacing 80 nm device using a medium. Thus, a small-sized and large-capacity magnetic recording device could be provided. With this device, the track width is 3
When reproducing with an MR head of .mu. or less, a high capacity magnetic recording device having a high recording density of 130 kBPI or more, an S / N of 3 or more, and an overwrite (O / W) characteristic of 26 dB or more was obtained. In particular, even at a high recording density of 4 kTPI or higher, the medium of the present embodiment sufficiently bleeds in the track width direction, so that a high S / N was obtained. Further, since the texture is formed by processing the protective film, the quality of the servo signal is high, and good head positioning is possible.

The magnetic recording apparatus of this embodiment was gently dropped from a height of 1 meter onto a wooden floor, and the same measurement was carried out. However, no difference in the recording / reproducing characteristics was observed before and after the drop. .

(Example 4) Sample No. 20 containing B was used as the substrate glass 1 and heated at a power of 1 kW for 10 seconds.
A TeFeCo magnetic film was formed by the vacuum evaporation method. This magnetic film for magneto-optical recording has perpendicular magnetic anisotropy, and compared with a conventional film formed on polycarbonate at room temperature,
The anisotropic magnetic field Hk could be increased 1.3 times. By combining this magnetic recording medium, the magnetic recording medium drive section, the light generation section and the detection section, and the drive section, and the recording / reproduction signal processing system, it is possible to form a magnetization reversal region that is 60% smaller than the conventional one. It was

[0038]

According to the present invention, a magnetic recording medium suitable for high-density recording which secures sufficient and stable coercive force even on a glass substrate, and a recording density of 1 gigabit per square inch or more using the same. It is possible to provide a magnetic recording device that realizes

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention.

FIG. 2 is an explanatory diagram showing an infrared spectrum from a heater.

FIG. 3 is an explanatory diagram of a heater.

FIG. 4 is an explanatory diagram of a magnetic recording medium showing an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a magnetic recording medium showing a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of an apparatus for realizing an embodiment of the present invention.

[Explanation of symbols]

1 ... Glass substrate, 2 ... Incident light, 3 ... Transmitted light, 4 ... Reflected light, 5 ... Heater.

Front Page Continuation (72) Inventor Nobuyuki Inaba 1-280 Higashi Koikeku, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Masaaki Nihon 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Central Research Co., Ltd. In-house (72) Inventor, Tanahashi, Kokubunji, Tokyo 1-280, Higashi-Kengikubo, Central Research Laboratory, Hitachi, Ltd.

Claims (8)

[Claims] 1. A magnetic recording medium in which a base film, a magnetic film, and a protective film are laminated in this order on a glass substrate, and when the glass substrate transmits infrared rays having a wavelength of 3 μ vertically, the incident light intensity is Io, When the transmitted light intensity is I, the reflectance is R, and the thickness of the glass substrate is d, (1 / d) log e (Io (1
A magnetic recording medium characterized by using a glass substrate having a value of −R) ² / I) of 0.3 [1 / cm] or more. 2. A magnetic recording medium in which a base film, a magnetic film, and a protective film are laminated in this order on a glass substrate, and Co, Ni, Cr, Fe, La, Y, contained in the glass substrate.
Gd, Yb, Lu, Ce, Sm, Eu, Tb, Dy, H
A magnetic recording medium having a total value of o or Tm of 0.01 mol or more and less than 0.5 mol per liter. 3. A magnetic recording medium in which a base film, a magnetic film, and a protective film are laminated on a glass substrate in this order, and B contained in the glass substrate is 1 mol or more per liter.
A magnetic recording medium characterized by being less than 0 mol. 4. A magnetic recording medium in which a base film, a magnetic film, and a protective film are laminated in this order on a glass substrate, and the P contained in the glass substrate is 0.5 mol or more and less than 10 mol per liter. A magnetic recording medium characterized by the following. 5. A magnetic recording medium in which a base film, a magnetic film, and a protective film are laminated in this order on a glass substrate, and V contained in the glass substrate is 0.1 mol or more and less than 5 mol per liter. A magnetic recording medium characterized by the following. 6. A magnetic recording medium in which a base film, a magnetic film, and a protective film are laminated in this order on a glass substrate, and the Li contained in the glass substrate is 0.5 mol or more and less than 10 mol per liter. A magnetic recording medium characterized by the following. 7. A magnetic recording medium, a drive unit for the magnetic recording medium, a magnetic head, and a drive unit for the magnetic head,
7. A product Brt of a residual magnetic flux density Br measured in the head traveling direction and a total film thickness t of the magnetic film, preferably using a magnetic recording medium according to any one of claims 1 to 6 having a recording / reproducing signal processing system. Is 100 Gauss · μ or less, and a magnetoresistive head or a giant magnetoresistive head is used as a reproducing magnetic head. 8. A magnetic recording medium, a drive unit for the magnetic recording medium, a light generation unit, a detection unit, and a drive unit for the magnetic recording medium, and a recording / reproducing signal processing system. A magnetic recording device using the magnetic recording medium according to.