JPH07272245A - Magnetic recording medium and recording-reproducing method - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium excellent in light transmittance, antistatic performance, surface properties and running durability and to provide a recording and reproducing method by which a magnetic head can be accurately positioned without deteriorating basic characteristics such as electromagnetic transducing characteristics and the durability of a medium. CONSTITUTION:A light transmitting electric conductive middle layer 12 is formed between a magnetic recording layer 13 and a transparent nonmagnetic substrate 11 to obtain the objective magnetic recording medium. The middle layer 12 is based on powder of an electrically conductive metal or metallic compd. having <=0.5mum primary particle diameter and a resin binder and the resin binder content of the layer 12 is 1-2mg per 1m<2> BET specific surface area of the powder. Optical tracking servo is carried out by using the magnetic recording medium with light of >=700nm wavelength.

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 provided 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. A signal proportional to sin (2πR / P) is obtained by subtracting the signal D (P represents a 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 (2
Make a binary code that represents πT / P). This binary code is converted into an analog signal by multiplication type DA converters (DACs) 56 and 57, and at the same time, each signal obtained from the subtracters 52 and 53 is multiplied, and the difference between the products is subtracted by the subtracter 58. The position error signal shown in the following equation is obtained by calculation.

[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, the error is close to 0 and highly accurate tracking control is performed. Be seen.

[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 when detecting transmitted light, if the transparency of the magnetic recording medium is low, the difference in light transmittance between where the groove exists and where it does not becomes extremely small.
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.

On the other hand, in the conventional floppy disk, carbon black is contained in the magnetic recording layer to impart conductivity for the purpose of preventing electrification.
Its transparency is extremely poor, and the light transmittance for light of 830 nm, for example, 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 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 use a magnetic recording medium excellent in light transparency, antistatic property, surface property and running durability. Another object of the present invention is to provide a recording / reproducing method capable of accurately positioning a magnetic head without deteriorating basic characteristics such as electromagnetic conversion characteristics and medium durability.

That is, the gist of the present invention is a magnetic recording medium comprising a magnetic recording layer and a transparent non-magnetic support, and a light-transmitting conductive intermediate layer formed between the magnetic recording layer and the transparent non-magnetic support. The conductive metal or metal compound powder having a particle diameter of 0.5 μm or less and a binder resin as main components, and the binder resin content of B. E. T. A magnetic recording medium having a surface area of 1 to ² mg per 1 m ² .

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 / reproducing method of reproducing, the magnetic recording medium has a light-transmitting conductive intermediate layer between the magnetic recording layer and the transparent non-magnetic support, and the conductive intermediate layer is B. of a powder of a conductive metal or metal compound having a primary particle diameter of 0.5 μm or less as a main component and a powder of a conductive metal or metal compound and a binder resin. E. T. Surface area 1
The optical code for tracking servo is recorded on the magnetic recording medium in an amount of 1 to ² mg per m ^2, which is identified by the difference in optical properties from other portions.
By irradiating the magnetic recording medium with light having a wavelength of 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. A recording / reproducing method characterized in that 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.

The conductive intermediate layer of the magnetic recording medium of the present invention is
The main component is a powder of metal or metal compound having a primary particle diameter of 0.5 μm or less and a binder resin. As the powder of a metal or a metal compound having conductivity, for example, silver,
Examples thereof include metals such as 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, powder of metal or metal compound having a volume resistance of 0.05 to 50 Ω · cm is used. The primary particle diameter of these is 0.01 to 0.5 from the viewpoint of light transmittance.
About μm is preferable.

The binder resin used in the conductive intermediate layer is a polyurethane resin, polyester resin, cellulose acetate butyrate, cellulose diacetate, cellulose derivative such as nitrocellulose, vinyl chloride-vinyl acetate copolymer, vinyl chloride- Examples thereof include vinyl chloride resins such as vinylidene chloride copolymers and vinyl chloride-acrylic copolymers, various synthetic rubbers such as styrene-butadiene copolymers, epoxy resins, and phenoxy resins. These may be used alone or in combination with 2 A mixture of two or more species can be used.

In the conductive intermediate layer, the content of the binder resin is B.p.B. of the conductive metal or metal compound powder.
E. T. It is 1-2 mg per 1 m ^{2 of} surface area. 1 mg
If it is less, the dispersibility is lowered and the surface property of the coating film is lowered.
On the other hand, if the amount is more than 2 mg, the conductivity of the coating film is lowered and the running durability is lowered. 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. The magnetic recording layer of the magnetic recording medium of the present invention does not need to contain carbon black as an antistatic agent as in the conventional magnetic recording medium, but may be contained within a range not impairing the transparency of the magnetic recording medium. Good. 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 based on 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. As the carbon black, conventionally known ones such as furnace black and graphitized carbon black can be used. Further, an antistatic agent other than carbon black may be contained in a range that does not impair the transparency of the magnetic recording medium.

As the magnetic powder, binder, curing agent, lubricant, abrasive, dispersant, etc. used in the magnetic recording layer, conventionally known ones are used. As the magnetic powder, for example, F
e, Ni, Co, Fe-Co alloy, Fe-Ni alloy, F
e-Co-Ni alloy, Fe-Ni-Zn alloy, Fe-C
Fe, Ni, such as o-Ni-Cr alloy and Co-Ni alloy
Powders of ferromagnetic metals such as Co or magnetic alloys containing these as the main components, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , and Co-containing γ-Fe.
₂ O ₃ , iron oxide magnetic powder such as Co-containing Fe ₃ O ₄ , CrO ₂ ,
Examples thereof include various ferromagnetic powders such as metal oxide magnetic powders such as barium ferrite and strontium ferrite.

The magnetic powder used is preferably one having a primary particle diameter of 0.1 μm or less. Primary particle size is 0.1
By using magnetic powder having a particle size of not more than μm, the light transmittance and recording density can be increased. 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.

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 and the like, and these can be used alone or in combination of two or more kinds. The binder is preferably used so that its content in the magnetic recording layer is 2 to 50% by weight, particularly 5 to 35% by weight.

By incorporating a low molecular weight polyisocyanate compound having a plurality of isocyanate groups into the magnetic paint, a three-dimensional network structure can be formed in the magnetic recording layer and its mechanical strength can 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.

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. Also,
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 in the magnetic recording layer is usually 0.
It is preferably used in an amount of 1 to 20% by weight, preferably 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 abrasive include alumina, fused alumina, corundum, silicon carbide, chromium oxide, silicon nitride and the like. Among these, those having a relatively high hardness, preferably those having a Mohs hardness of 6 or more are suitably used. Further, those having a number average particle diameter of 2 μm or less are preferably used. The abrasive is preferably used so that its content in the magnetic recording layer is 1 to 20% by weight.

As the dispersant, 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 salts or alkaline earth metal salts of these fatty acids, Lecithin or 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. 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.

As the non-magnetic support having transparency, any support generally used in magnetic recording media can be used as long as it has light permeability, and polyesters such as polyethylene terephthalate and polyethylene naphthalate can be used. 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 is usually preferably 70% or more, and particularly preferably 85% or more for light having a wavelength range of 700 to 900 nm, particularly 830 nm. The thickness of the non-magnetic support is such that it can be used as a support and satisfies the above transmittance, and is usually 30 to 80 μm.

The conductive intermediate layer and the magnetic recording layer of the magnetic recording medium of the present invention usually comprise the constituent components, respectively.
It is formed by kneading and dispersing in a solvent, coating the resulting coating on a non-magnetic support or a conductive intermediate layer, and then drying. It is also preferable to calender the surface of the conductive intermediate layer and the magnetic recording layer to form a smooth surface.

There are no particular restrictions on the method of kneading, dispersing, drying, calendering, the order of addition of each component, and various conventionally known methods can be used. As a coating method, various commonly used 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 paint include ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohols such as methanol, ethanol, propanol and isopropyl alcohol, esters such as methyl acetate, ethyl acetate and butyl acetate, and diethyl. Conventionally known substances such as ethers such as ether and tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic hydrocarbons such as hexane can be used, and these can be used alone or as a mixture.

The light transmittance of the magnetic recording medium of the present invention is preferably 20% or more for light in the wavelength range of 700 to 900 nm, particularly 830 nm, except for the portions marked with optical symbols described later. , Usually 20 to 35%. The magnetic recording medium of the present invention can 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 a groove having an appropriate width and depth on the medium surface. Further, a dye-containing layer containing a dye is provided in the medium,
It is also possible to record an optical code by irradiating light on a predetermined portion thereof 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 or a portion having a lower light reflectance than other portions.

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 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.

For providing the dye-containing layer, a conventionally known coating method can be applied. As the resin, solvent, etc. used for preparing the coating liquid, conventionally known ones as described above may be used alone or as a mixture. The pigment content is
Although it varies depending on the kind of the dye used, the thickness of the dye-containing layer, the performance of the optical signal detection group, etc., it is usually contained in an amount such that the light transmittance, the light reflectance, etc. are changed 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, it is described in JP-A-2-31387. As described above, it is possible to arrange a large number of optical codes (in this case, grooves) on a concentric circle with respect to a disk-shaped medium. 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 provided concentrically on the medium surface at a pitch of 20 to 21 μm, and have a length of 20 to 21 μm and a width of 4.6 to 5.
It is 0 μm and the depth is 0.2 μm or more. The light transmittance in the groove portion is preferably 35% or more, and the light transmittance between the groove portion and the portion without the groove preferably has a contrast of 10% or more.

Further, 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. Since the magnetic recording medium used is also excellent in antistatic property, surface property, and running durability, it is necessary to perform recording / reproduction with excellent basic properties such as electromagnetic conversion characteristics and durability of the medium against contact with a magnetic head. You can

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 conventionally used ring type head can be used. What is used. A conventional method can be adopted as a method for recording / reproducing a magnetic signal. For example, when a ring type head is used, a magnetic signal is recorded on a magnetic recording medium by a magnetic field generated in a gap, while a magnetic recording medium is used. The magnetic signal is read by detecting the magnetic field generated by the magnetic signal recorded on the disk by the gap.

Since the magnetic recording medium used has a high transparency especially 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 70.
Read using light with a wavelength of 0 nm or more. The wavelength is 70
There is no particular limitation as long as it is 0 nm or more, but particularly 700 to 9
The light of 00 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, a method of calculating an error from a target value by using a photodiode divided into four as described in the above description of the prior art 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, its length is 40 Hz and 20 Hz depending on the rotation of the medium at 750 rpm.
The length is such as to generate a signal of. In FIG. 2, the phase difference between the optical patterns 31 and 32 is 0 in the track 1,
Track 2 has λ / 8, track 3 has λ / 4,
Thereafter, the optical patterns 31 and 32 are recorded with the phase difference sequentially shifted by λ / 8 for each track.

The light irradiation position 23 of the detector (light receiving element and light emitting 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 applied to 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, for example, directly above the track 2. 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 “cos δ” as a function of track position are widely used for position control as resolver or encoder signals, and the output of the signal processing circuit is the tracking based on various known position control methods. It can be used as an input signal of the control device.

The phase difference is obtained, for example, by using a frequency separating means such as a filter for a signal detected by a 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 the long wavelength component is binarized, it is multiplied by 4 by the PLL circuit, 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 A / 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.

[0049]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited by the following examples unless it exceeds the gist. In addition, all "parts" in the examples indicate "parts by weight". Example 1 Tin oxide (primary particle size 0.03) which is a conductive metal compound
μm, B.I. E. T. A coating material for the conductive intermediate layer having the following composition containing a surface area of 80 m ² / g) was prepared and applied to both surfaces of a polyester support having a thickness of 62 μm so that the film thickness after drying was 0.5 μm. A magnetic paint having the following composition was kneaded and dispersed in a ball mill on the upper side, and both surfaces were applied so that the film thickness after drying would be 0.8 μm.

[0050]

[Table 1] Coating composition for conductive intermediate layer Tin oxide 100 parts (primary particle size 0.03 µm, specific surface area 80 m ² / g) Binder resin 15 parts (vinyl chloride-vinyl acetate resin "VAGH", manufactured by UCC) Methyl ethyl ketone (MEK) 90 parts Cyclohexanone (CHN) 90 parts * B. E. T. Binder resin amount per surface area of 1 m ² 1.9 mg

[0051]

[Table 2] Composition for magnetic layer coating (magnetic coating) Barium ferrite magnetic powder 100 parts Vinyl chloride-vinyl acetate copolymer 4 parts Polyurethane 4 parts Polyisocyanate 2 parts ("Coronet L", Nippon Polyurethane Co.) Alumina 5 parts Butyl stearate 5 parts MEK 140 parts CHN 140 parts

After the surface was smoothed by a calendering process, a 3.5 "disk was punched out to prepare a floppy disk. Example 2 An example except that the amount of the binder resin in the conductive intermediate layer was 10 parts. A floppy disk was produced in the same manner as in 1. The amount of the binder resin per 1 m ² of the surface area of the tin oxide powder was 1.3 mg.

Comparative Example 1 A floppy disk was manufactured in the same manner as in Example 1 except that the amount of binder resin in the conductive intermediate layer was changed to 7 parts. The amount of binder resin per 1 m ² of surface area of the tin oxide powder was 0.9 mg.

Comparative Example 2 A floppy disk was manufactured in the same manner as in Example 1 except that the amount of the binder resin in the conductive intermediate layer was 20 parts. The amount of binder resin per 1 m ² of surface area of the tin oxide powder was 2.5 mg.

COMPARATIVE EXAMPLE 3 The conductive metal powder of the conductive intermediate layer was made to have a primary particle diameter of 0.8 μm.
A floppy disk was produced in the same manner as in Example 1 except that tin oxide powder having a specific surface area of 4 m ² / g was used.
The amount of binder resin per 1 m ² of surface area of tin oxide powder is 3
It was 7.5 mg. Table 1 shows the evaluation results of the manufactured floppy disks.

[0056]

[Table 3]

The measuring method for each evaluation item is shown below. The surface resistivity was determined by a high resistance measuring device according to JIS standard with an AC voltage applied to both ends of the medium. 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 on a drive in an atmosphere of relative humidity of 30% and running for 5 days, the medium having no scratch on the surface of the medium was evaluated as ◯, and the one having scratches was evaluated as x.

As is clear from the results shown in Table 1, the floppy disks obtained in Examples 1 and 2 have good surface resistivity, light transmittance, surface property and running durability. Further, when grooves having a length of 20 μm, a width of 5 μm and a depth of 0.4 μm were provided on the surface of the floppy disks obtained in Examples 1 and 2, a grooved portion (servo track portion) and a normal grooveless portion were obtained. The difference in light transmittance from the portion (data track portion) was 10% or more, and clear contrast was obtained.

[0059] The binder resin of the conductive intermediate layer each surface area 1 m ² per tin oxide powder 0.9mg and 37.
In Comparative Examples 1 and 3 with 5 mg, the surface properties of the coating film are poor and the running durability is poor. Further, Comparative Example 2 in which the amount of the binder resin was 2.5 mg per 1 m ² of the surface area of the tin oxide powder had poor running durability. In each of the comparative examples, a medium having effective characteristics as a high recording density medium was not obtained.

Further, a polymethine dye-containing layer was 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 were provided thereon, and then a mask was used. When a portion of 20 μm in length and 5 μm in width whose optical property is changed is provided in the circumferential direction of the medium surface by irradiating light, a part (servo track part) where optical property is changed and a normal part (data track) The difference in light transmittance from the (part) was 10% or more, and clear contrast was obtained.

Example 3 A method of forming grooves on the surface of the floppy disks obtained in Examples 1 and 2 as described above, and providing a polymethine dye-containing layer on a transparent non-magnetic support, An optical code as shown in FIG. 2 is obtained by two methods of irradiating light through a mask after providing a conductive intermediate layer and a magnetic recording layer similar to those of Examples 1 and 2 on each of them. 2. A disk-shaped magnetic recording medium is manufactured.
Each of the obtained floppy disks was mounted on a magnetic recording / reproducing apparatus, and an attempt was made to control the position of the magnetic head. The magnetic recording / reproducing apparatus used was an ordinary magnetic head and a laser beam of 830 nm. A light emitting element for irradiating and a light receiving element which is arranged to face the light emitting element via a floppy disk and detects the transmitted light through which the laser light passes through the floppy disk,
A detector provided integrally with the magnetic head, a signal processing circuit for frequency-dividing the output from the detector to generate a position signal corresponding to the phase difference δ, and a drive system for driving the magnetic head in the tracking direction. is there. As a result, it was confirmed that accurate tracking was performed in all cases.

[0062]

According to the present invention, there is provided a magnetic recording medium excellent in light transmittance, antistatic property, surface property and running durability. When a tracking servo optical code, which is identified by having different optical properties from other portions, is recorded on such a magnetic recording medium, a magnetic recording medium with easy servo tracking can be obtained.

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, since it is possible to cope with an increase in the track density of the magnetic recording medium, accurate servo tracking can be performed even in the high density magnetic recording medium.

[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 showing a part 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 (7)

[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 conductive intermediate layer has a primary particle diameter of 0.5 μm or less. B. of the powder of the conductive metal or metal compound, which contains the powder of the conductive metal or metal compound and the binder resin as main components, and the content of the binder resin is B. E.
T. A magnetic recording medium having a surface area of 1 to ² mg per 1 m ² . 2. The magnetic recording medium according to claim 1, which has a light transmittance of 20% or more with respect to light having a wavelength 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 tracking servo optical code has an optical property of the predetermined part of the dye-containing layer by irradiation with light. The magnetic recording medium according to claim 3, wherein the magnetic recording medium is recorded by a change in 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 substantially contacts 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 conductive intermediate layer has a primary particle diameter of 0.5 μm or less. B. of the powder of the conductive metal or metal compound, which contains the powder of the conductive metal or metal compound and the binder resin as main components, and the content of the binder resin is B. E. T. The surface area is 1 to ² mg per m ² , and the magnetic recording medium has an optical code for tracking servo, which is identified by its different optical properties from other portions, recorded thereon, and has a wavelength of 700 nm or more. A position signal corresponding to the position of the magnetic head with respect to the magnetic recording medium is generated by irradiating the magnetic recording medium and reading the optical code recorded on the magnetic recording medium, and the magnetic signal is generated based on the position signal. A recording / reproducing method characterized in that a head is positioned with respect to the magnetic recording medium. 7. The magnetic recording medium according to claim 2, 4 or 5.
The recording / reproducing method according to claim 6, wherein the recording / reproducing method is the magnetic recording medium according to claim 1.