JPH07262552A - Magnetic recording medium and recording and reproducing method - Google Patents

Abstract

PURPOSE:To accurately position a magnetic head without deteriorating the basic characteristics of a magnetic recording medium by carrying out tracking servoing with light of a specified wavelength by means of the magnetic recording medium with an electric conductive intermediate layer between the nonmagnetic substrate and a specified recording layer. CONSTITUTION:This magnetic recording medium is composed of a transparent nonmagnetic substrate 11, a light transmitting electric conductive intermediate layer 12 and a magnetic recording layer 13 contg. magnetic powder having <=1mum average particle diameter and particle of an abrasive material having >=0.45mum average primary particle diameter and >=5m<2>/g BET specific surface area. When optical tracking servoing is carried out with light of >=700nm wavelength by means of this magnetic recording medium, a magnetic head can be accurately positioned on the basis of servo information having a pattern different from that of recorded information without deteriorating the basic characteristics of this medium such as electromagnetic transducing characteristics and durability. This medium has improved transparency, antistatic performance, surface properties and running durability.

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 suitable for positioning a head by using light, and a recording / reproducing method using the magnetic recording medium.

[0002]

2. Description of the Related Art A large number of floppy disk devices are used for recording information in computers and word processors. In an ordinary floppy disk device, the head positioning is performed by open loop control using a step motor, so there is a limit to improvement in track density.

In recent years, there has been proposed a head position measuring technique in which a groove is provided in a magnetic recording medium and the groove position is read by an optical sensor provided integrally with a recording / reproducing head. According to this technique, the head can be positioned by the closed loop control even in the floppy disk device, and the positioning accuracy is improved, so that a track density higher by one digit than that of the conventional floppy disk device can be realized.

In a floppy disk device to which the above principle is applied, a large number of grooves are formed on a medium according to a track pitch, and a light emitting element, a light receiving element and an optical system which are integrated with a recording / reproducing head are adopted. The light emitted from the light emitting element is reflected by the medium or transmitted through the medium, and this is detected by the optical system and the light receiving element to read the groove position, thereby generating a position signal and performing tracking control.

FIG. 3 is a plan view schematically showing the relative arrangement of the light receiving surface of the light receiving element forming the servo signal detecting section of the conventional information recording apparatus based on the above principle and the track of the recording medium. In the figure, the light reflected from the recording medium includes a servo signal composed of two pit rows 42 that sandwich the recording track 43 as a signal component. The light receiving element 41 is
It is composed of four unit elements A to D arranged in a square lattice, and receives the reflected light from the medium and outputs four signals A to D consisting of light and dark of the light. In the signal processing circuit, the difference between the signal B and the signal A and the difference between the signal C and the signal D are calculated from the output of the light receiving element 41.

FIG. 4 is a block diagram showing the configuration of the signal processing circuit. When the head is located at the track position of radius R from the center of the recording medium, a signal proportional to cos (2πR / P) is subtracted from the signal B by the subtractor 52, and a signal C is subtracted from the signal C by the subtractor 53. By subtracting the signal D, signals proportional to sin (2πR / P) are obtained (P represents the track pitch). On the other hand, the binary code of the target value T is sin
And cos table are given to the address terminals of ROMs 54 and 55, respectively, so that sin (2πT / P) and cos (2πT / P)
Make a binary code that represents P) and. This binary code is multiplied by D
At the same time as being converted into analog signals by the A converters (DACs) 56 and 57, they are respectively multiplied by the respective signals obtained from the subtracters 52 and 53, and the product difference is calculated by the subtractor 58 to obtain the following equation. Obtain the position error signal shown.

[0007]

[Equation 1] cos (2πT / P) sin (2πR / P) −sin (2πT / P) cos (2πR / P) = sin ((2πR / P)-(2πT / P)) ≒ 2π (RT) / P By feeding this back to the tracking control device, highly accurate tracking control with an error close to 0 is performed.

[0008]

In the above tracking servo system using light, the transparency of the magnetic recording medium becomes a serious problem. That is, in the tracking servo method using light, the reflected light or the transmitted light of the light applied to the magnetic recording medium is detected, and the tracking is performed based on the difference in the light reflectance or the light transmittance between where the groove exists and where the groove does not exist. To do. Therefore, particularly in the case of detecting transmitted light, if the transparency of the magnetic recording medium is low, the difference in light transmittance between the place where the groove is present and the place where the groove is not present becomes extremely small, and accurate tracking cannot be performed. In fact, when tracking is performed with transmitted light, the light transmittance and the servo signal output are in a substantially proportional relationship, and whether or not the transparency of the magnetic recording medium is good is one of the biggest problems in the success or failure of servo tracking on the medium. Become.

In the conventional floppy disk, carbon black is contained in the magnetic recording layer for the purpose of preventing electrification and the like to impart conductivity, and as a result, its transparency is extremely poor, for example, 830 nm. The light transmittance is about 5% at most. Therefore, in order to impart conductivity without using carbon black, an intermediate layer is provided between the magnetic recording layer and a non-magnetic support that supports the magnetic recording layer, and the intermediate layer is made of a conductive metal, metal compound, resin, or the like. It has been studied to impart conductivity to the magnetic recording medium by containing the element. Such a magnetic recording medium is
It has both conductivity and transparency.

However, as a result of the study by the present inventor, in the magnetic recording medium which does not substantially contain carbon black as described above, the surface property of the medium surface and the running durability are poor, and it is required for the magnetic recording medium. It has been found that it is difficult to satisfy the basic characteristics.

[0011]

The present invention has been made in view of the above problems, and an object thereof is to provide a magnetic recording medium excellent in light transparency, antistatic property, surface property and running durability. It is in. Another object of the present invention is to provide a recording / reproducing method capable of accurately positioning a magnetic head without impairing basic characteristics such as electromagnetic conversion characteristics and medium durability.

That is, the gist of the present invention is a magnetic recording medium in which a light-transmissive conductive intermediate layer is formed between a magnetic recording layer and a transparent non-magnetic support, wherein the magnetic recording layer is a primary layer. A magnetic powder having a particle diameter of 0.1 μm or less, and a number average particle diameter of 0.45 μm or more and B.I. E. T. A magnetic recording medium containing abrasive particles having a specific surface area of 5 m ² / g or more according to the method.

Another aspect of the present invention is to record a magnetic signal on a magnetic recording medium and / or to record a magnetic signal recorded on the magnetic recording medium by using a magnetic head that is substantially in contact with the magnetic recording medium. In the recording and reproducing method for reproducing,
The magnetic recording medium has a light-transmissive conductive intermediate layer between the magnetic recording layer and the transparent non-magnetic support, and,
The magnetic recording medium has an optical code recorded therein, which is identified by having different optical properties from other portions, and the magnetic recording layer has a magnetic powder having a primary particle diameter of 0.1 μm or less and a number average. The particle size is 0.45 μm or more, and B. E.
T. A method of irradiating the magnetic recording medium with light having a specific surface area of 5 m ² / g or more and having a wavelength of 700 nm or more, and reading the optical code recorded on the magnetic recording medium. A position signal corresponding to the position of the magnetic head with respect to the magnetic recording medium is generated, and the magnetic head is positioned with respect to the magnetic recording medium based on the position signal. .

The present invention will be described in detail below. Figure 1
FIG. 3 is a schematic cross-sectional view showing the basic structure of the magnetic recording medium of the present invention. A light-transmitting conductive intermediate layer 12 is provided on the transparent non-magnetic support 11, and the intermediate layer 12 is further provided.
A magnetic recording layer 13 is provided on the top. Middle layer 12
May be formed anywhere between the non-magnetic support 11 and the magnetic recording layer 13, for example, the non-magnetic support 1
An easy-adhesion layer may be provided between 1 and the intermediate layer 12. Further, a protective layer may be further provided on the magnetic recording layer 13.

The magnetic recording layer can be formed on both sides or one side of the non-magnetic support. When magnetic recording layers are formed on both sides, a light-transmissive conductive intermediate layer may be provided between at least one of the magnetic recording layers and the non-magnetic support, but preferably a conductive intermediate layer is provided on each surface. Provide layers.
When the magnetic recording layer is formed only on one surface of the non-magnetic support,
A back layer may be provided on the opposite surface.

In the magnetic recording medium of the present invention, the magnetic recording layer formed on the transparent non-magnetic support has a magnetic powder having a primary particle diameter of 0.1 μm or less and a number average particle diameter of 0.4.
5 μm or more and B.I. E. T. Specific surface area by method is 5m
² / g or more of abrasive particles are contained. The magnetic powder used in the present invention is not particularly limited as long as the primary particle diameter is 0.1 μm or less, and various magnetic powders can be used. When the primary particle size is larger than 0.1 μm, the transparency of the magnetic recording layer and the magnetic recording medium as a whole deteriorates. Further, when the primary particle diameter is 0.1 μm or less, not only preferable transparency can be obtained, but also the recording wavelength can be shortened, so that the recording density of the magnetic recording medium can be increased. Specific examples of magnetic powders include, for example, Fe, Ni,
Co, Fe-Co alloy, Fe-Ni alloy, Fe-Co-
Ni alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-
Powders of ferromagnetic metals such as Fe, Ni, Co, etc. such as Cr alloys, Co—Ni alloys, etc., or magnetic alloys containing these as the main components,
γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing γ-Fe ₂ O ₃ , Co
Various ferromagnetic powders such as iron oxide magnetic powders such as Fe ₃ O ₄ content, metal oxide magnetic powders such as CrO ₂ , barium ferrite, strontium ferrite and the like can be mentioned. The amount of the magnetic powder used is preferably such that the content of the ferromagnetic powder in the magnetic recording layer is 50 to 90% by weight, particularly 55 to 85% by weight.

The abrasive particles used in the present invention have a number average particle size of 0.45 μm or more and B.I. E. T. The abrasive particles have a specific surface area of 5 m ² / g or more according to the method. Abrasive particles such as those described above are usually more angular than spherical in shape. When the number average particle diameter is less than 0.45 μm, the durability of the magnetic recording medium is reduced. Also, the specific surface area is 5m
If it is less than ² / g, the durability will be reduced. If the number average particle diameter exceeds 2 μm, the durability of the magnetic recording medium may be deteriorated, so the number average particle diameter of the abrasive particles is preferably 2 μm or less. The abrasive particles having a relatively high hardness are preferably used, and preferably have a Mohs hardness of 6 or more. In particular. Examples thereof include Cr ₂ O ₃ , SiC, alumina, fused alumina, corundum, and silicon nitride. The content of the abrasive in the magnetic recording layer is preferably in the range of 1 to 20% by weight.

The magnetic recording layer is usually formed by dispersing the above magnetic powder, abrasive, etc. in a binder. As the binder, conventionally known binders are appropriately used. For example, polyurethane resins, polyester resins, cellulose acetate butyrate, cellulose diacetate, cellulose derivatives such as nitrocellulose, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylic copolymers. Examples thereof include vinyl chloride resins such as polymers, various synthetic rubbers such as styrene-butadiene copolymers, epoxy resins, phenoxy resins, etc. These may be used alone or in combination of two or more. The content of the binder in the magnetic recording layer is 2 to 50% by weight, particularly 5 to 5% by weight.
It is preferably used so as to be 35% by weight.

By adding a low molecular weight polyisocyanate compound having a plurality of isocyanate groups to the magnetic coating material for forming the magnetic recording layer, a three-dimensional network structure is formed in the magnetic recording layer and its mechanical property is improved. Strength can also be improved. Examples of such a low molecular weight polyisocyanate compound include a tolylene diisocyanate adduct of trimethylolpropane.
Such a low molecular weight polyisocyanate compound is preferably used in a proportion of 5 to 100% by weight with respect to the binder.

The magnetic recording layer may further contain various additives such as a lubricant and a dispersant. As the lubricant, various kinds of lubricants such as aliphatic type, fluorine type, silicone type and hydrocarbon type can be used. Examples of the aliphatic lubricant include fatty acids, fatty acid metal salts, fatty acid esters, fatty acid amides, and aliphatic alcohols. Examples of the fatty acid include oleic acid, lauric acid, myristic acid, palmitic acid, stearic acid and behenic acid. Examples of the fatty acid metal salt include magnesium salts, aluminum salts, sodium salts and calcium salts of these fatty acids. Examples of the fatty acid ester include butyl ester, octyl ester and glyceride of the above fatty acids, and examples of the fatty acid amide include amides of the above acids, linoleic acid amide and caproic acid amide. Examples of the aliphatic alcohol include lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol and the like. Examples of the fluorine-based lubricant include perfluoroalkyl polyether and perfluoroalkylcarboxylic acid. Examples of the silicone lubricant include silicone oil and modified silicone oil. Further, solid lubricants such as molybdenum disulfide and tungsten disulfide, and phosphoric acid esters can also be used. Examples of the hydrocarbon lubricant include paraffin, squalane, wax and the like. The content of the lubricant is usually 0.1 to 20% by weight in the magnetic recording layer,
It is preferably in the range of 1 to 10% by weight. When two magnetic recording layers are laminated, the content of the lubricant may be different between the upper layer and the lower layer.

Examples of the dispersant include fatty acids having 12 to 18 carbon atoms such as capric acid, lauric acid, myristic acid, oleic acid and linoleic acid, metal soaps containing alkali metal or alkaline earth metal salts of this fatty acid, lecithin and the like. Is used. The amount of the dispersant used is usually in the range of 0 to 20% by weight in the magnetic recording layer. In the magnetic recording medium of the present invention, it is not necessary to include an antistatic agent such as carbon black in the magnetic recording layer, but it may be contained within a range that does not impair the transparency of the magnetic recording medium. In this case, for example, when carbon black having an average primary particle diameter of 30 nm or less is contained, the content thereof is usually 0 to 1% by weight with respect to the magnetic powder. When carbon black having an average primary particle diameter of 80 to 400 nm (for example, thermal carbon) is contained, the content thereof is usually 0 to 2% by weight based on the magnetic powder.

The dry thickness of the magnetic recording layer is usually about 0.6 to 0.9 μm. If it is too thick, the light transmittance may deteriorate, and if it is too thin, the durability and output may decrease. In the magnetic recording medium of the present invention, a light transmissive conductive intermediate layer is provided between the magnetic recording layer and the transparent non-magnetic support.

The conductive intermediate layer is usually composed mainly of powder of conductive metal or metal compound or conductive resin and a binder. Examples of the conductive metal or metal compound powder include metals such as silver and platinum, and metal compounds such as tin oxide, zinc oxide, titanium oxide, barium sulfate, and potassium titanate. Further, a metal compound such as tin oxide doped with antimony or aluminum can also be used. Preferably, a metal or metal compound having a volume resistance of 0.05 to 50 Ω · cm is used. The primary particle diameter of these particles is 0.5 μm or less, particularly 0.01 to 0.
It is preferably about 5 μm.

As the binder used for the conductive intermediate layer, various binders similar to those used for the magnetic recording layer can be used. The dry thickness of the conductive intermediate layer is usually 0.01 to 5 μm, and preferably 0.05.
˜1 μm. If the film thickness is too large, the light transmittance may decrease. If it is too small, effective conductivity may not be obtained.

The light transmittance of the conductive intermediate layer is usually 700 to 900 n as the light transmittance of only one conductive intermediate layer.
m, especially 50% or more, and preferably 70% or more for light of 830 nm. As the transparent non-magnetic support used in the magnetic recording medium of the present invention, a support that can be used in general for magnetic recording media can be used as long as it has optical transparency.
Polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polyethylene, cellulose derivatives such as cellulose acetate, various plastics such as polycarbonate, polyamide and polyimide, and other glass can also be used. The light transmittance of the non-magnetic support to be used is usually preferably 70% or more, particularly 85 for the wavelength range of 700 to 900 nm, particularly 830 nm.
% Or more is preferable. The thickness of the non-magnetic support is
It is a thickness that can be used as a support. In addition, the thickness may be a thickness that satisfies the light transmittance, and is usually about 30 to 80 μm.

In the magnetic recording layer and the conductive intermediate layer of the magnetic recording medium of the present invention, usually, a coating material containing each component is kneaded, dispersed, and applied on a non-magnetic support.
It is formed by drying. After forming the conductive intermediate layer and the magnetic recording layer, calendering is performed,
Smoothing the surface is also recommended. Kneading, dispersion,
There are no particular restrictions on the method of drying and calendering, the order of addition of each component, and various conventionally known methods can be used.

As a coating method, various commonly applied methods such as air doctor coating, blade coating, reverse roll coating and gravure coating are adopted. When a plurality of coating materials are applied, the lower layer coating solution and the upper layer coating solution may be applied simultaneously in a wet state, or each layer may be applied sequentially. Examples of the solvent for the coating material include ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohols such as methanol, ethanol, propanol and isopropyl alcohol, methyl acetate, ethyl acetate, esters such as butyl acetate, diethyl ether and tetrahydrofuran. And the like, and aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic hydrocarbons such as hexane, and the like, which are conventionally known, can be used alone or in combination.

The transmittance of the magnetic recording medium of the present invention is 7
It is preferably 20% or more with respect to light in the range of 00 to 900 nm, particularly 830 nm, and is usually preferably 20 to 35% except for the portion with an optical code described later. On the magnetic recording medium of the present invention, it is possible to record an optical code for tracking servo which is identified by having different optical properties from other portions. By reading this optical code with light, accurate tracking becomes possible. The optical code can be recorded, for example, by grooves having a suitable width and depth on the surface of the medium. It is also possible to record the optical code by providing a dye-containing layer containing a dye in the medium and irradiating a predetermined portion of the layer with light to change the optical property. The optical code is identified by different optical properties such as light transmittance and light reflectance from other portions. For example, the portion of the optical code can be a portion having a higher light transmittance or a lower light reflectance than the other portion, or a portion having a lower light transmittance.

When a dye-containing layer containing a dye is provided in the medium, the dye-containing layer may also serve as the magnetic recording layer or the conductive intermediate layer, and the dye-containing layer may be used alone as the other layer. It may be provided. The dye to be used is not particularly limited as long as its optical properties are changed by light irradiation and the like, and may be appropriately selected and determined. Specifically, various known dyes such as cyanine-based, phthalocyanine-based, naphthalocyanine-based, azo-based, anthraquinone-based, naphthoquinone-based, pyrylium-based, azurenium-based, squarylium-based, indophenol-based, indoaniline-based, triarylmethane-based Is used.

In order to form the dye-containing layer on the support, a conventionally known coating method can be applied. As the resin, solvent, etc. used for preparing the coating solution, the conventionally known ones described above may be used alone or as a mixture. The content of the dye, the type of dye used, the thickness of the dye-containing layer,
Although it depends on the performance of the detector and the like, it is usually contained in an amount such that the light transmittance, the light reflectance and the like change to a measurable degree by light irradiation.

The recording pattern of the optical code may be any pattern as long as it can identify the position of the magnetic recording medium. For example, JP-A-2-31
No. 387, there are a large number of optical codes of the same kind (in this case, concentrically on a disk-shaped medium).
Arranging grooves). As a method of forming the groove, a method in which a mold having a convex groove portion is pressed against the medium to transfer the shape of the mold to the medium (stamping processing), laser beam irradiation is performed, and a part of the magnetic recording layer is decomposed and removed. Method (laser processing) and the like. The grooves formed here are usually concentrically provided on the medium surface at a pitch of 20 to 21 μm, and have a width of 4.6 to 5.0 μm and a length of 20 to 2.
The depth is 1 μm and the depth is 0.2 μm or more. The light transmittance in the groove portion is preferably 35% or more, and it is preferable that the transmittance between the groove portion and the portion without the groove produces a contrast of 10% or more.

It is also possible to provide two optical codes having different frequencies on one servo track and record by sequentially making the phase difference between them different for each servo track. In this case, the signal obtained by combining the respective frequency components corresponding to the two optical codes is recorded in correspondence with the width or depth of the servo track (when the optical code is a groove), or the PWM By recording as a modulated binary signal, it is possible to record as one optical code. In either case, tracking is done by detecting the phase difference between two optical codes or frequency components.

The recording / reproducing method of the present invention uses the above-mentioned magnetic recording medium to record a magnetic signal on the magnetic recording medium and / or magnetic recording while accurately determining the position of the magnetic head by applying optical tracking servo. The magnetic signal recorded on the medium is reproduced. In the recording / reproducing method of the present invention, since the magnetic recording medium used is excellent in transparency, the optical code recorded therein can be easily detected, and therefore accurate tracking can be performed. Also,
Since the magnetic recording medium used is also excellent in antistatic property, surface property and running durability, it is possible to perform recording / reproduction excellent in basic properties such as electromagnetic conversion characteristics and durability of the medium against contact with the magnetic head. .

The magnetic head is not limited as long as it can read a magnetic signal recorded on a magnetic recording medium and / or record a magnetic signal on the magnetic recording medium, and various types such as a ring type head which has been conventionally used. What is used. A conventional method can be adopted as a method for recording / reproducing a magnetic signal. For example, when a ring head is used, the magnetic signal is recorded on the magnetic recording medium by the magnetic field generated in the gap, while the magnetic recording is performed. The magnetic signal is read by detecting the magnetic field generated by the magnetic signal recorded on the medium by the gap.

Since the magnetic recording medium used has a high transparency particularly to light having a wavelength of 700 nm or more, in the recording / reproducing method of the present invention, the optical code recorded on the magnetic recording medium is 7
Read using light with a wavelength of 00 nm or more. Wavelength is 7
There is no particular limitation as long as it is at least 00 nm, but 700 to 90
Light of 0 nm is easy to obtain commercially as a semiconductor laser, an infrared LED, or the like.

The optical code is, for example, 70 radiated on the medium.
It is read by detecting reflected light or transmitted light of light having a wavelength of 0 nm or more using a light receiving element. The present invention is particularly effective when transmitted light is used because the magnetic recording medium has high transparency. In the recording / reproducing method of the present invention, a position signal corresponding to the position of the magnetic head with respect to the medium is read by reading the optical code recorded on the magnetic recording medium with a light emitting element and a light receiving element which are usually provided integrally with the head. Is generated, and the magnetic head is positioned with respect to the medium based on this position signal.

As the positioning method, various conventionally known methods can be adopted according to the optical code recorded on the medium. For example, as described in the above description of the prior art, 4
A method of calculating an error from the target value using a divided photodiode can be adopted. Further, when the two optical codes or the optical code obtained by combining two types of frequency components as described above are recorded on the medium while sequentially changing the phase difference for each servo track, the position is detected by detecting the phase difference. A signal is generated.

FIG. 2 is a schematic plan view showing a part of a disk-shaped magnetic recording medium for illustrating the method of reading the phase difference. As noted, the horizontal direction on the drawing indicates the traveling direction of the medium. Further, the direction orthogonal to that, that is, the vertical direction, indicates the tracking direction. In the figure, servo tracks 1 to 5 on the recording medium are illustrated, and as the optical code, a first optical code 21 and a second optical code 22 are used.
And are recorded. The first optical code 21 is recorded at a predetermined interval along the medium traveling direction, and constitutes a first optical pattern 31 which is a periodic repetition of the first optical code 21. The second optical code 22 is recorded at a predetermined interval along the medium traveling direction, and forms a second optical pattern 32 which is a periodic repetition of the second optical code 22. 1 of the first optical pattern 31
One set consisting of a row and one row of the second optical pattern 32 is recorded on each track. The width of each track is 6 μm.

The first optical pattern 31 is recorded as a code having the same phase for each track. The second optical pattern 32 has a frequency different from that of the first optical pattern 31. That is, if the wavelength of the first optical pattern 31 is λ, the wavelength of the second optical pattern 32 is λ.
/ 2. The phase of the second optical pattern 32 sequentially changes by λ / 8 for each track. As the medium travels, the first optical pattern 31 and the second optical pattern 3
An AC signal corresponding to 2 is output from the detector, but the frequencies of these optical patterns are different, so the output signal includes signals of two types of frequencies.

The first optical pattern 31 and the second optical pattern 32 are recorded alternately in the tracking direction, and their widths are each 3 μm. Also, the length is such that rotation of the medium at 750 rpm produces signals at 40 Hz and 20 Hz. In FIG. 2, the phase difference between the optical patterns 31 and 32 is 0 in the track 1, λ / 8 in the track 2, and λ / 4 in the track 3, and thereafter, the optical patterns 31 and 32 are similar to each other. The phase differences are recorded while being sequentially shifted by λ / 8.

The light irradiation position 23 of the detector (light emitting element and light receiving element) for detecting the optical code, which moves integrally with the magnetic head, is schematically shown as being located at the track position shown in the figure. . An electric signal obtained by detecting the transmitted light or the reflected light of the light irradiated on the light irradiation position 23 by the light receiving element is used as the input signal “i” of the subsequent signal processing circuit.

Consider a case where the light irradiation position 23 is located directly above the track 2, for example. At this time, the output of the detector is a signal corresponding to the combination of the optical patterns of the track 2. Now, when the magnetic head moves and the light irradiation position 23 moves in the direction of the track 1, a signal component due to the combination of the optical patterns of the track 1 is superimposed on the output of the detector, so that a short pattern corresponding to the optical pattern 32 is obtained. The phase of the wavelength component advances. On the contrary, when the magnetic head moves and the light irradiation position 23 moves in the direction of the track 3, a signal component due to the combination of the optical patterns of the track 3 is superimposed on the output of the detector, which corresponds to the optical pattern 32. The phase of the short wavelength component is delayed.

As described above, since the optical pattern of the information recording medium is recorded by changing the phase difference for each track, the phase difference δ of the signals of the two detected optical patterns increases according to the moving direction of the detector. Or decrease. Therefore, the signal indicating the track position can be obtained by generating the position signal corresponding to the phase difference δ by the signal processing circuit. For example, the signals “sin δ” and “c as a function of track position
osδ ″ is widely used as a signal of a resolver or an encoder for position control, and the output of the signal processing circuit can be used as an input signal of a tracking control device based on various known position control methods.

The phase difference is obtained by, for example, using a frequency separating means such as a filter to detect the signal detected by the detector.
It is detected by separating into two frequency components corresponding to the optical pattern on the medium and detecting this by the phase difference detecting means. Specifically, for example, the following can be done. That is, a long wavelength component is extracted from the signal detected by the detector using a bandpass filter, and the short wavelength component is extracted by subtracting this from the original signal. After binarizing the long wavelength component, the PLL circuit multiplies it by four, and the timing generation circuit generates two timing signals having the same frequency as the short wavelength component but different in phase by π / 2. Using this, the SIN and COS signals corresponding to the phase difference are obtained by synchronously rectifying the short wavelength component.

This output is input to the head positioning means, which positions the magnetic head. For example, the SIN and COS signals corresponding to the phase difference are
After the D conversion and input to DSP, the zero point and amplitude are corrected, and then the phase difference is calculated by arc tangent calculation.
This is combined with the value of the counter that counts the wave numbers of the SIN and COS signals to form a position signal. To control the magnetic head, for example, a thrust command value is calculated by a normal PID algorithm, and a linear actuator is operated via a D / A converter and a power amplifier.

[0046]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, all "parts" in the examples indicate "parts by weight". Example 1 Tin oxide (particle size 0.03 μm), which is a conductive metal compound
m) was prepared and coated on both surfaces of a 62 μm-thick polyester support as an intermediate layer so that the film thickness after drying would be 0.5 μm. On the upper side, a coating liquid prepared by kneading and dispersing a magnetic coating material having the following composition in a ball mill was applied on both sides as a magnetic recording layer so that the film thickness after drying was 0.8 μm.

[0047]

[Table 1] Coating composition for conductive intermediate layer Tin oxide (primary particle diameter 0.03 μm) 100 parts Binder resin 15 parts Methyl ethyl ketone (MEK) 90 parts Cyclohexanone (CHN) 90 parts

[0048]

[Table 2] Composition of coating material for magnetic recording layer (magnetic coating material) Hexagonal magnetic powder 100 parts (barium ferrite; primary particle diameter determined by image analysis by SEM = 0.05 μm) Vinyl chloride-vinyl acetate copolymer 4 parts Polyurethane 4 parts Polyisocyanate 2 parts Carbon black 1 part (Mitsubishi Kasei # 3250B; average primary particle size 0.03)
μm) Alumina 5 parts (HIT30 manufactured by Sumitomo Chemical Co., Ltd .; number average particle size determined by centrifugal sedimentation = 0.50 μm, BET value 6 m ² / g) Butyl stearate 5 parts MEK 140 parts CHN 140 parts

After the flattening treatment by calendering, a 3.5 "disk was punched out to prepare a floppy disk. Example 2 Example 1 except that carbon black was not added to the magnetic recording layer. A floppy disk was manufactured in the same manner.

Comparative Example 1 A polishing agent added to the magnetic recording layer was added to have a number average particle size of 0.4.
Abrasives smaller than 5 μm (AKP30 manufactured by Sumitomo Chemical Co., Ltd .;
Number average particle diameter 0.41 μm determined by centrifugal sedimentation, B.I. E.
T. A floppy disk was manufactured in the same manner as in Example 1 except that the value was 6.1 m ² / g). Comparative Example 2 The polishing agent added to the magnetic recording layer was B. E. T. Value 5m ²
/ G or less of polishing agent (AKP20 manufactured by Sumitomo Chemical Co., Ltd .; number average particle diameter 0.5 μm determined by centrifugal sedimentation, BET value 4)
A floppy disk was manufactured in the same manner as in Example 1 except that m ² / g) was used.

Table 1 shows the evaluation results of the manufactured floppy disks.

[0052]

[Table 3]

The measuring method for each evaluation item is shown below. The surface resistivity was determined by a high resistance measuring instrument with an AC voltage applied to both ends of the medium according to JIS standard. The smaller the surface resistivity, the better the antistatic effect. The light transmittance was measured using light having a wavelength of 830 nm, and the ratio of transmitted light to incident light was obtained. Surface property (R
The value a) was measured using a Talystep stylus type surface roughness meter manufactured by Taylor Hobson. Running durability is temperature 60 ℃,
After being mounted in a drive in an atmosphere of relative humidity of 30% and running for 5 days, the medium having no scratch on the medium surface was marked with ◯, and the one with scratch was marked with x.

As is clear from the results shown in Table 1, the media of Examples 1 and 2 have good surface resistivity, light transmittance, surface property and running durability. Further, on the surface of the media obtained in Examples 1 and 2, width 5 μm, length 20 μm, depth 0.
When the groove of 4 μm was provided, the difference in light transmittance between the grooved portion and the grooveless portion was 10% or more, and clear contrast was obtained.

Furthermore, a dye-containing layer (polymethine dye is used as a dye) is provided on a transparent non-magnetic support, and a conductive intermediate layer and a magnetic recording layer similar to those in Examples 1 and 2 are provided thereon. Then, by irradiating light through a mask, the length of the media is 20 μm in the circumferential direction and the width is 5 μm.
A floppy disk provided with the servo information of 1. was manufactured.
In this case as well, the difference in light transmittance between the part irradiated with light and the part not irradiated with light was 10% or more, and clear contrast was obtained.

Example 3 A method of forming grooves on the surface of the medium obtained in Examples 1 and 2, a dye-containing layer (using a polymethine dye as a dye) is provided on a non-magnetic support, and the method is carried out thereon. Examples 1 and 2
And a method of irradiating light through a mask after providing an intermediate layer and a magnetic recording layer similar to the above.
A disk-shaped magnetic recording medium having an optical code as shown in FIG. 2 was manufactured to obtain a 3.5 "floppy disk. A normal magnetic head, a light emitting element for irradiating a laser beam of 830 nm, and a floppy disk were used. A detector provided opposite to the light emitting element, which has a light receiving element for detecting the transmitted light of the laser light from the floppy disk, is provided integrally with the magnetic head, and the output from the detector is frequency-separated to obtain a phase difference. a signal processing circuit for generating a position signal corresponding to δ,
Further, the floppy disk was mounted on a magnetic recording apparatus having a drive system for driving the magnetic head in the tracking direction, and the position control of the magnetic head was tried. As a result, it was confirmed that accurate tracking was performed.

[0057]

According to the present invention, there is provided a magnetic recording medium excellent in light transparency, antistatic property, surface property and running durability. By recording an optical code for tracking servo, which is identified by having different optical properties from other portions, on such a magnetic recording medium, a magnetic recording medium with easy servo tracking can be obtained. Further, since the primary particle diameter of the magnetic powder is set to 0.1 μm or less, the recording wavelength can be shortened and the recording density of the magnetic recording medium can be increased. Further, according to the present invention, there is provided a recording / reproducing method capable of accurately positioning the magnetic head without deteriorating the basic characteristics such as electromagnetic conversion characteristics and medium durability. Therefore, it is possible to cope with an increase in the track density of the medium, and it is possible to perform accurate servo tracking.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the basic structure of a magnetic recording medium of the present invention.

FIG. 2 is a schematic plan view of a magnetic recording medium for illustrating a phase difference reading method.

FIG. 3 is a plan view schematically showing a relative arrangement between a light receiving surface of a light receiving element forming a servo signal detecting section of an information recording device and a track of a recording medium.

FIG. 4 is a block diagram showing a configuration of a signal processing circuit.

[Explanation of symbols]

 11 Non-magnetic Support 12 Conductive Intermediate Layer 13 Magnetic Recording Layer 21 First Optical Code 22 Second Optical Code

Claims (6)

[Claims] 1. A magnetic recording medium comprising a magnetic recording layer and a transparent non-magnetic support having a light-transmissive conductive intermediate layer formed therein, wherein the magnetic recording layer has a primary particle diameter of 0.1 μm.
The following magnetic powder, and the number average particle size of 0.45 μm or more and B. E. T. A magnetic recording medium containing abrasive particles having a specific surface area of 5 m ² / g or more according to the method. 2. The magnetic recording medium according to claim 1, which has a light transmittance of 20% or more for light of 700 to 900 nm. 3. The magnetic recording medium according to claim 1, wherein an optical code for tracking servo, which is identified by having a different optical property from other portions, is recorded. 4. The magnetic recording medium according to claim 3, wherein the tracking servo optical code is recorded by a groove provided on the surface of the magnetic recording medium. 5. A magnetic recording medium is provided with a dye-containing layer containing a dye, and the optical code for tracking servo has a characteristic of the optical property of the predetermined part of the dye-containing layer by light irradiation. The magnetic recording medium according to claim 3, wherein the magnetic recording medium is recorded by a change. 6. A recording / reproducing method for recording a magnetic signal on a magnetic recording medium and / or reproducing a magnetic signal recorded on a magnetic recording medium by using a magnetic head which is substantially in contact with the magnetic recording medium, The magnetic recording medium has a light-transmissive conductive intermediate layer between a magnetic recording layer and a transparent non-magnetic support, and the magnetic recording medium has other portions and optical properties. The optical recording layer is recorded with an optical code which is identified by the difference between the magnetic recording layer and the magnetic recording layer. E.
T. A method of irradiating the magnetic recording medium with light having a specific surface area of 5 m ² / g or more and having a wavelength of 700 nm or more to read the optical code recorded on the magnetic recording medium. According to the method, a position signal corresponding to the position of the magnetic head with respect to the magnetic recording medium is generated, and the magnetic head is positioned with respect to the magnetic recording medium based on the position signal.