JPH07296361A - Magnetic recording medium, production thereof and recording/reproducing method - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium onto which a tracking servo signal can be written without deteriorating the surface properties of a magnetic layer by providing a nonmagnetic support, at the intermediate part thereof, with a layer containing such a coloring matter that optical properties thereof are varied upon irradiation with an energy beam. CONSTITUTION:A nonmagnetic support 1 has a laminate structure where a coloring matter-containing layer 3 is sandwiched by first and second support layers 2a, 2b. Magnetic layers 4a, 4b containing a magnetic substance are formed on the opposite sides of the nonmagnetic support 1. Since polyethylene terephthalate(PET), generally used as the support for magnetic recording medium, has light transmittance of 90% or above, generation of heat is substantially eliminated when the PET is employed as a nonmagnetic material and a tracking servo signal can be written only onto the coloring matter containing layer.

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 such as a floppy disk, a manufacturing method thereof and a recording / reproducing method. In particular, the present invention relates to a magnetic recording medium suitable for positioning a recording / reproducing head using an optical detecting means, a manufacturing method thereof, and a recording / reproducing method.

[0002]

2. Description of the Related Art In recent years, in order to increase the capacity of a magnetic recording medium, a portion having a different optical property from a reference portion (that is, an optical pattern is formed) is provided in the medium and is integrated with a head. A technique has been proposed in which the position of the head is determined by reading the position of the portion with an optical sensor provided and using this as a servo signal for tracking, thereby obtaining a track density that is an order of magnitude higher than the conventional one.

As a method of forming an optical pattern for a tracking servo signal, a method is known in which a groove is formed on the surface of a magnetic layer by laser processing or the like, a difference in the amount of transmitted light is detected, and this is used as a tracking servo signal. However, since the groove portion is not suitable for magnetic recording, there is a problem that the recording capacity is reduced. Therefore, a dye is dispersed and contained in a magnetic layer or a non-magnetic support, and the dye is decomposed only in a specific portion in response to a tracking servo signal, thereby changing the optical properties and forming an optical pattern. , A method for obtaining a tracking servo signal for head positioning has been proposed (JP-A-5-143977).
(See Japanese Patent Application No. 4-336277).

[0004]

However, if the dye is contained in the magnetic layer, it is necessary to reduce the amount of the magnetic powder by that amount, and sufficient electromagnetic conversion characteristics cannot be obtained. Further, when a dye-containing layer is provided between the magnetic layer and the non-magnetic support or when a dye is dispersed and contained in the entire non-magnetic support, the mechanical properties of the non-magnetic support are different from those of a normal non-magnetic support. There is a risk of deterioration. Further, there is a problem that when a signal is written by laser irradiation, the magnetic layer is damaged and electromagnetic conversion characteristics are deteriorated.

[0005]

The present invention has been made in view of the above-mentioned problems of the prior art, and its gist is to provide a magnetic layer containing a magnetic substance on a non-magnetic support. In a recording medium, the non-magnetic support has a layer containing a dye whose optical properties are changed by energy ray irradiation in the middle part thereof, and the non-magnetic support contains a magnetic substance on the non-magnetic support. Is provided with a magnetic layer,
Moreover, an optical pattern for a tracking servo signal is formed by irradiating a magnetic recording medium having a layer containing a dye whose optical property is changed in the nonmagnetic support by irradiation with an energy beam in the middle part thereof by irradiating the energy beam. In a method for producing a magnetic recording medium characterized by forming, and a method for recording and reproducing magnetic data using a magnetic recording medium provided with a magnetic layer containing a magnetic substance on a non-magnetic support, As a magnetic recording medium, a magnetic layer containing a magnetic material is provided on a non-magnetic support, and the non-magnetic support has a layer containing a dye whose optical property is changed by irradiation with energy rays in the middle part thereof. A magnetic recording medium having:
For the layer containing the dye, a magnetic recording medium in which an optical pattern for a tracking servo signal based on a change in the optical property of the dye due to irradiation with energy rays is recorded on a track is used, and the layer containing the dye is used. And a magnetic recording medium which records and reproduces magnetic data while tracking the magnetic head using the tracking servo signal detected by the optical means.

The present invention will be described in detail below. Layer containing a dye in the magnetic recording medium of the present invention (dye-containing layer)
Since the optical properties change due to irradiation with energy rays such as laser light, electron beams, and ultraviolet rays, if the energy rays are radiated corresponding to the tracking servo signals to be recorded, the tracking servo signal An optical pattern for the above can be easily formed on the medium.

As a method of irradiating an energy ray used for forming an optical pattern on the dye-containing layer, an optical system is used.
For example, a method of irradiating a light beam (for example, strobe light, ultraviolet light, etc.) or an electron beam through a mask having a light shielding portion and a light transmitting portion corresponding to a laser beam condensed to a certain spot diameter or a signal to be recorded. Can be adopted. Examples of the changes in the optical properties include an increase in light transmittance, a decrease in light transmittance, an increase in light reflectance, and a decrease in light reflectance. For example, when a dye whose light transmittance is increased by irradiation with energy rays is used, an optical signal can be obtained from a portion having a high light transmittance in a medium surface having a low light transmittance. Further, when a dye whose light transmittance is reduced by irradiation with energy rays is used, an optical signal can be obtained from a portion having a low light transmittance in a medium surface having a high light transmittance.

FIG. 1 is a schematic sectional view showing an example of the layer structure of the magnetic recording medium of the present invention. The nonmagnetic support 1 has a laminated structure in which the dye-containing layer 3 is used as an intermediate layer and sandwiched between the first support layer 2a and the second support layer 2b. Magnetic layers 4 a and 4 b containing a magnetic material are formed on both outer layers of the non-magnetic support 1. 2 and 3 are schematic cross-sectional views showing examples of other layer configurations of the magnetic recording medium of the present invention. The dye-containing layer 3 is composed of a plurality of dye-containing layers such as 3a and 3b. These may be separated from each other as shown in FIG. 2 or may be adjacent to each other as shown in FIG. When there are a plurality of dye-containing layers in this way, it is possible to write different information in each of the dye-containing layers 3a and 3b.

The formation of the optical pattern is carried out by irradiating the dye-containing layer arranged in the middle part of the non-magnetic support with a focused energy beam, preferably a laser beam, focused on a spot diameter. . At this time, heat is generated in a portion that absorbs the laser light and is close to the focal point where the laser is effectively focused. Therefore, if a non-magnetic support having a high light transmittance is used and a dye-containing layer is provided in the middle of the non-magnetic support and a focused laser beam is applied to the dye-containing layer, only the laser-irradiated part of the dye-containing layer is irradiated. Fever,
It causes phenomena that change the optical properties of the dye, such as decomposition of the dye. For example, a polyethylene terephthalate (PET) film or the like, which is widely used as a support for magnetic recording media, has a light transmittance of 90% or more. Therefore, when PET is used as a non-magnetic support, it hardly generates heat and the dye-containing layer Only the tracking servo signal can be written. Further, although the magnetic layer absorbs the laser light, it is far from the focus position of the laser light, so that it is hard to generate heat. Therefore, the damage of the magnetic layer can be suppressed low, and the optical tracking servo signal can be written in the dye-containing layer.

On the other hand, when the dye-containing layer is provided in contact with the magnetic layer on the side opposite to the non-magnetic support, or between the magnetic layer and the non-magnetic support, the magnetic layer is laser light. Since the magnetic layer is close to the focal point, the magnetic layer may generate heat and be damaged, resulting in deterioration of surface properties. When the dye is dispersed throughout the non-magnetic support, the damage to the magnetic layer can be improved by adjusting the focal point to the middle part of the support.
Since the dye-containing layer is thick, the spread of the laser beam is directly written as an optical pattern, and it is difficult to obtain a good tracking servo signal.

In the present invention, when the thickness of the dye-free non-magnetic support layer portion between the dye-containing layer and the magnetic layer is too thin, the distance from the magnetic layer to the dye-containing layer becomes too small. Therefore, the magnetic layer may be damaged due to direct heating of the magnetic layer by laser light or heat transfer from the dye-containing layer. On the other hand, if the thickness is too large, the dye-containing layer and the signal light receiving portion of the magnetic recording medium become too far apart, which may weaken the positioning signal. Therefore, the thickness of the non-magnetic support layer portion containing no dye between the dye-containing layer and the magnetic layer is usually 3 μm.
To 100 μm, more preferably 10
μm to 70 μm. The dye-containing layer does not necessarily have to be provided in the central portion of the non-magnetic support or symmetrically.
Therefore, the thickness of each non-magnetic support layer forming the non-magnetic support does not necessarily have to be the same.

The dye used in the dye-containing layer is a dye whose optical properties are changed by irradiation with energy rays, and is not particularly limited as long as it can effectively absorb the irradiation energy rays. Good. In a magnetic recording medium, the absorption of light by the magnetic layer becomes smaller as the wavelength becomes longer in the ultraviolet region → visible region → infrared region. Therefore, the detection of transmitted light is facilitated by using light in the visible region to the infrared region. Therefore, it is preferable to use a dye having a light absorption in this region as the dye used in the dye-containing layer,
Further, it is preferable to irradiate a laser having this wavelength for forming the optical pattern.

In the present invention, preferably, a dye-containing layer in which a dye is added is used as the dye-containing layer. However, the color developability (absorption wavelength, absorbance) at this time is often different from that in the organic solvent. It is preferable to form a film containing a dye-containing coating liquid containing a dye added thereto and evaluate the light absorption characteristics. The maximum absorption wavelength (λmax) of the dye is preferably 600 nm or more, more preferably 7 nm in the above coating film.
It is 50 nm or more, particularly preferably 750 to 900 nm. The reason why it is particularly preferable to use a dye having a λmax of 750 nm to 900 nm is 780 nm and 830 nm.
This is because it is possible to cause a change in absorbance by utilizing thermal decomposition with a general-purpose laser having a wavelength such as.

Specific examples of the dye include polymethine, cyanine, phthalocyanine, naphthalocyanine, azo, anthraquinone, naphthoquinone, pyrylium, azulenium, squarylium, indophenol, indoaniline. Various known dyes such as triaryl methane series are used. The content of the dye in the dye-containing layer varies depending on the type of dye used, the thickness of the dye-containing layer, the performance of the optical signal detector, etc., but the light transmittance, light reflectance, etc. can be measured by irradiation with energy rays. The dye-containing layer usually contains 0.0
It is about 01 to 30% by weight.

The dye-containing layer may contain additives such as an antistatic agent, an anti-degradation agent and a crosslinking agent, as long as the effects of the present invention are not impaired. As a method for obtaining a non-magnetic support having a dye-containing layer in the middle portion used in the present invention, for example, a dye solution prepared by dissolving or dispersing a dye in a solvent is first mixed with a binder resin, a dispersant, etc., if necessary. It is prepared as a coating solution and coated on the first non-magnetic support layer directly or via another layer. As a coating method, various coating methods that are usually applied, such as air doctor coating, blade coating, reverse roll coating, and gravure coating, are adopted. It is also possible to use a method such as vapor deposition or transfer. As the resin, solvent and the like used for preparing the coating liquid, conventionally known ones can be used alone or in combination as will be described later. Then, the second non-magnetic layer (film) is bonded with the dye-containing layer sandwiched (dry lamination) to obtain the non-magnetic support.

Further, a method of hot-melting a dye with a resin, melt-coating the first non-magnetic layer on the first non-magnetic layer, and then laminating the second non-magnetic layer together (hot melt lamination), or a method in which the dye is a binder resin Alternatively, a method of extruding into a film shape and sandwiching it between the non-magnetic films and adhering it (extrusion lamination) or the like can be used. In addition, after a dye-containing layer is laminated on a non-magnetic film, a binder resin dissolved in a solvent is applied thereon to a predetermined thickness to form a substantially dye-free layer. Can be used.

Among the above methods, the dry laminating method is particularly preferable because the thermal damage to the dye is small. An adhesive may be used to bond the non-magnetic film,
As the adhesive in that case, a known adhesive such as a urethane-based adhesive can be used. Further, a urethane resin may be used as the binder resin of the dye-containing layer to serve also as the adhesive.

Further, the non-magnetic film may be subjected to surface modification as described later in order to improve the adhesiveness of each layer during lamination. Further, when the dye-containing layer is formed in multiple layers, repeated coating and laminating of the dye-containing layer may be repeated. As the material of the non-magnetic support layer portion containing no dye, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polypropylene, polyolefins such as polyethylene, cellulose derivatives such as cellulose acetate, polycarbonate, polyamide,
Examples include various plastics such as polyimide, glass, and the like.

As the non-magnetic support, polyesters such as polyethylene terephthalate and polyethylene naphthalate are usually used because of their excellent mechanical properties, heat resistance, electrical properties and chemical resistance. Since the polyester film is highly crystallographically oriented, it generally has poor adhesion to the dye-containing layer. Therefore, in order to improve the adhesion between the non-magnetic support and the magnetic layer, alkali, amine aqueous solution, trichloroacetic acid,
Treatment with a surface modifier such as phenols can also be applied. At this time, a dye may be mixed with the surface modifier and coated on one of the nonmagnetic layers.

Further, in order to improve the adhesiveness, various easily-adhesive resins may be used to form an easily-adhesive layer, and the easily-adhesive layer may contain a dye. For example, a known adhesive resin, such as an acrylic resin, a polyurethane resin, or a polyester resin, mixed with a dye is usually prepared as a coating solution and applied on the surface of one nonmagnetic layer. The thickness of the easily adhesive layer is usually 0.005 as a dry film thickness.
It is 5 μm.

In addition, an intermediate layer containing a conductive material and a binder resin may be provided between the magnetic layer and the non-magnetic support in order to improve the charging property of the magnetic layer. Examples of the conductive material include a conductive metal or a metal compound, and are not particularly limited. For example, a powder of a metal such as silver or platinum or a powder of a metal compound such as tin oxide, zinc oxide, or potassium titanate is used. To be done. The average particle diameter of these powders is 0.
005 to 0.6 μm is preferable. A magnetic recording medium provided with a conductive intermediate layer has a low electric resistance on the surface of the magnetic layer, and since the amount of carbon black in the magnetic layer can be reduced, it is excellent in light transmission and writing an optical pattern for a tracking servo signal, Suitable for reproduction. The thickness of the intermediate layer is a dry film thickness and is usually 0.005 to 5 μm.

Magnetic substance and binder used in the magnetic layer
Resin, curing agent, lubricant, abrasive, antistatic agent, dispersant, etc.
Any known material can be used. Magnetism
As the body, for example, Fe, Ni, Co, Fe-Co compound
Gold, Fe-Ni alloy, Fe-Co-Ni alloy, Fe-N
i-Zn alloy, Fe-Co-Ni-Cr alloy, Co-N
Ferromagnetic metal such as i alloy, Fe, Ni, Co or the like
Magnetic alloy powder containing these as main components, γ-Fe₂O₃,
Fe₃O_Four, Co-containing γ-Fe₂O ₃, Co-containing Fe₃
O_FourIron oxide magnetic powder such as CrO₂, Barium Ferrai
, Magnetic powder of metal oxide such as strontium ferrite
Various ferromagnetic powders such as

The magnetic substance has a primary particle diameter of 0.1 μm.
The following are preferred. By using a magnetic material having a primary particle diameter of 0.1 μm or less, the light transmittance and the recording density can be increased. The amount of the magnetic material used is preferably such that the content of the ferromagnetic powder in the magnetic layer is 50 to 90% by weight, particularly 55 to 85% by weight.

As the binder resin, one having excellent adhesion to the support and abrasion resistance is appropriately used. For example,
Polyurethane resin, polyester resin, cellulose acetate butyrate, cellulose diacetate, cellulose derivative such as nitrocellulose, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylic copolymer Examples thereof include vinyl chloride resins such as, 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 resin is preferably used such that its content in the magnetic layer is 2 to 50% by weight, particularly 5 to 35% by weight.

By adding a low molecular weight polyisocyanate compound having a plurality of isocyanate groups to the magnetic paint, a three-dimensional network structure is formed in the magnetic layer,
The 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 resin.

As the lubricant, various kinds of lubricants such as aliphatic type, fluorine type, silicone type and hydrocarbon type can be used. Examples of aliphatic lubricants 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 salt, aluminum salt, sodium salt, calcium salt and the like of these fatty acids. Examples of the fatty acid ester include butyl ester, octyl ester and glyceride of the above fatty acid, 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. As a silicone lubricant,
Examples thereof 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 amount of the lubricant used is preferably such that the content in the magnetic layer is usually 0.1 to 20% by weight, preferably 1 to 10% by weight.
When the magnetic layer is formed in two layers, 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, and among these, those having relatively high hardness are preferably used. The number average particle size is 2
Those having a size of μm or less are preferably used. The abrasive is preferably used so that the content in the magnetic layer is 1 to 20% by weight.

As the antistatic agent, carbon black,
Natural surfactants such as graphite and saponin, nonionic surfactants such as alkylene oxides and glycerin, higher alkylamines, quaternary ammonium salts, cationic surfactants such as pyridinium salts and other heterocyclic compounds, carvone Anionic surfactants containing acidic groups such as acid groups, sulfonic acid groups, phosphoric acid groups, sulfuric acid ester groups, phosphoric acid ester groups, etc., amphoteric surfactants such as amino acid-based, aminosulfonic acid-based, sulfuric acid or phosphoric acid ester-based amino alcohols, etc. Etc. are used. These surfactants may be used alone or as a mixture. The amount of the antistatic agent used is usually preferably such that the content in the magnetic layer is 1 to 15% by weight. These are used as antistatic agents, but sometimes their purpose is, for example, to improve dispersibility and lubricity.

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 dispersant is usually preferably used so that the content in the magnetic layer is 0 to 20% by weight.

Kneading, dispersing, and magnetic coating containing the above components
As the solvent used at the time of coating, for example, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, methanol, ethanol, propanol, alcohols such as isopropyl alcohol, methyl acetate, ethyl acetate, esters such as butyl acetate, Examples thereof include ethers such as diethyl ether and tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic hydrocarbons such as hexane.

Regarding the method of kneading and dispersing the magnetic coating material, the order of addition of each component, etc., a conventionally known method generally applied to the kneading and dispersing of the magnetic coating material is used. The magnetic layer can be formed by applying the magnetic coating material onto the non-magnetic support directly or through another layer. As a method of applying the magnetic coating material onto the non-magnetic support, various methods that are usually applied such as air doctor coating, blade coating, reverse roll coating, and gravure coating are adopted. When a plurality of magnetic layers are coated, the lower layer coating solution and the upper layer coating solution may be coated simultaneously in a wet state, or each layer may be coated sequentially.

The thickness of the magnetic layer is usually 0.
It is 1 to 10 μm, preferably 0.3 to 2 μm. Further, a top coat layer for imparting lubricity or a back coat layer for preventing electrification can be provided. Further, orientation treatment, random treatment, smoothing treatment, or the like may be performed as necessary.

In the present invention, the tracking servo signal is recorded by providing a portion (forming an optical pattern) on the servo track of the dye-containing layer where the change in the optical property of the dye due to the irradiation of energy rays occurs. It In the case of a disk-shaped magnetic recording medium, the above tracks are concentric tracks. The portion where the optical property of the dye is changed may be continuously provided on the track, or the portion where the optical property of the dye is changed and the part where the optical property of the dye is not changed are alternately provided. Good. Further, an optical pattern may be provided so that a signal containing one type of frequency component can be obtained as the tracking servo signal, or an optical pattern can be provided so that a signal containing two types of frequency components can be obtained. .

Here, the case where an optical pattern is provided so as to obtain a signal containing two kinds of frequency components as the tracking servo signal will be specifically described. An optical pattern that can obtain a signal containing two types of frequency components as tracking servo signals may be recorded on one servo track, or two types of signals with different frequencies may be spatially different and close to each other. May be recorded in each. In the latter case, a single detector can be used to detect the two signals at the same time to obtain a signal in which two types of frequency components are superimposed. The tracking servo signal read by the optical means by the detector is separated into the respective frequency components by the frequency separating means, and an error signal for detecting a tracking error is obtained from these, whereby accurate tracking becomes possible.

The above frequency components are recorded so as to have different phase tracking servo signals from one servo track to another. In this case, the current head position can be detected by measuring this phase tracking servo signal, and the head position can be controlled so that this value becomes a predetermined value. As a method of recording a signal containing two kinds of frequency components on one servo track, for example, a trigonometric function corresponding to the two kinds of signals is added, and this magnitude is made to correspond to the width of the servo track and analogized. Recording, or by converting into a binary signal by PWM (pulse width modulation) and recording, or by dividing the servo track into minute sections in the circumferential direction and sequentially allocating each frequency component to different corresponding recording sections. The recording method may be used.

The width of the section divided in the circumferential direction on the servo track should be sufficiently smaller than the wavelength of each frequency component. By making the width of the section sufficiently smaller than the detection area of the detector, A signal obtained by combining the respective frequency components is output from the detection device. In the magnetic recording medium of the present invention, tracking is performed as follows, for example. The detector is integrated with the magnetic head,
Reflected light or transmitted light from the detection region is detected by irradiating the light beam from the light source. Whether to detect the reflected light or the transmitted light is determined by whether the servo track of the medium is recorded on the basis of the difference in the optical properties of the reflectance and the transmittance. Since the recorded portion and the non-recorded portion of the servo track have different optical properties, the amount of light received by the detector changes periodically due to the rotation of the magnetic recording medium, and an AC signal is output from the detector. .

Here, in the case of the magnetic recording medium of the present invention in which the PWM-modulated tracking servo signal is recorded, the detection area is sufficiently larger than the PWM modulation period, and as a result, the recording signals in this portion are averaged and output. The optical recording PWM-modulated at a sufficiently high frequency is detected as a signal that changes in an analog manner. When the detection unit is small, the signal of the PWM modulation frequency is included in the detector output signal, but in this case, it can be removed by using an electronic filter or the like.

Since the detected AC signal has two frequency components, these can be separated by using a frequency separating means such as a bandpass filter. Since the phase difference of signals sequentially differs between tracks, the current position of the magnetic head can be detected by measuring the phase difference of each separated frequency component with a phase difference detector or the like.

As a servo device for performing tracking, various known devices can be used. Generally, a servo circuit known as a PLL (Phase Locked Loop) is nothing but a servo circuit using a phase difference as a signal source, and each of the two signals is multiplied by 4 to multiply a short wavelength component by 4 and a long wavelength component. Accurate tracking can be performed by controlling the head position by PLL so that the phases of the signals obtained by multiplying by .times. Further, when the servo device is constructed using the digital signal processor, the rising time of the two signals can be read into the digital signal processor and the difference between them can be calculated to easily obtain the tracking error.

[0040]

EXAMPLES Specific embodiments of 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. All "parts" in the examples indicate parts by weight. Example 1 4 parts of polymethine dye, 87 parts of vinyl chloride-vinyl acetate-vinyl alcohol copolymer and 9 parts of polyisocyanate were dissolved in methyl ethyl ketone (MEK) to give a thickness of 6
About 2 μm polyethylene terephthalate (PET) film is coated on one side by microgravure to a thickness of about 1
A μm dye-containing layer was formed. PET having a thickness of 30 μm was dry-laminated on this film with the dye-containing layer inside, using a polyurethane adhesive.

Next, in order to impart conductivity to the laminated PET, tin oxide powder (particle size: 0.05 μm) 100
Part, 15 parts of a binder resin and 180 parts of an organic solvent (methyl ethyl ketone / cyclohexanone = 1/1) are prepared, and both surfaces of the film are coated so that the film thickness after drying is 0.5 μm. did. Further on the upper side, 100 parts of barium ferrite magnetic powder, 4 parts of vinyl chloride-vinyl acetate copolymer, 4 parts of polyurethane, 2 parts of polyisocyanate, 1 part of carbon black, 5 parts of alumina, 5 parts of butyl stearate, organic A magnetic coating composition consisting of 280 parts by weight of a solvent (methyl ethyl ketone / cyclohexanone = 1/1) was kneaded and dispersed in a ball mill, and a coating solution was applied on both sides so that the film thickness after drying was 0.8 μm.

After flattening the surface by calendering, it was punched into a 3.5-inch disk. Then, a semiconductor laser beam having a wavelength of 830 nm was irradiated to partially decompose and decolor the dye. The light transmittance of 830 nm in the undecomposed portion of the dye was about 11%, while the light transmittance of the decomposed portion was about 2%. The dye-decomposed portion showed almost no damage to the magnetic layer or deterioration of the surface property as compared with the undecomposed portion. By arranging the disassembled parts on the tracks in the circumferential direction, the servo information could be added to the floppy disk without substantially impairing the electromagnetic conversion characteristics.

Comparative Example 1 In the same manner as in Example 1, a dye-containing layer was formed on one side of a PET film having a thickness of 62 μm. Next, as in the first embodiment,
A tin oxide-containing layer and a magnetic layer containing barium ferrite magnetic powder were coated on both sides to prepare a floppy disk. When the dye was partially decomposed by laser light in the same manner as in Example 1, the light transmittances of the decomposed portion and the undecomposed portion were almost the same as those in Example 1, but the magnetic layer was partially damaged and the surface was damaged. Clearly deteriorated, and the electromagnetic conversion characteristics also deteriorated.

[0044]

According to the magnetic recording medium of the present invention, the tracking servo signal required for the head positioning system can be written without deteriorating the surface property of the magnetic layer, and the head is positioned by using the optical detecting means. It is possible to provide a suitable magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a layer structure of a magnetic recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the magnetic recording medium of the present invention.

FIG. 3 is a schematic cross-sectional view showing another example of the layer structure of the magnetic recording medium of the present invention.

[Explanation of symbols]

 1 non-magnetic support whole 2 non-magnetic layer 3 dye-containing layer 4 magnetic layer

Claims (7)

[Claims] 1. A magnetic recording medium comprising a magnetic layer containing a magnetic material provided on a non-magnetic support, wherein the non-magnetic support contains a dye having an optical property which is changed in the middle part thereof by irradiation with energy rays. A magnetic recording medium having a layer. 2. The magnetic recording according to claim 1, wherein the non-magnetic support is a laminated body in which a first non-magnetic layer, a dye-containing layer and a second non-magnetic layer are laminated in this order. Medium. 3. The magnetic material according to claim 1, wherein an optical pattern for a tracking servo signal based on a change in the optical property of the dye upon irradiation with energy rays is recorded in the dye-containing layer. recoding media. 4. An energy ray is a laser having a wavelength in the maximum absorption wavelength (λmax) region of a dye.
4. The magnetic recording medium according to any one of 1 to 3. 5. A magnetic layer containing a magnetic material is provided on a non-magnetic support, and a layer containing a dye whose optical property is changed by energy beam irradiation is provided in the middle of the non-magnetic support. A method of manufacturing a magnetic recording medium, comprising forming an optical pattern for a tracking servo signal by irradiating the magnetic recording medium having the energy beam. 6. A method for recording / reproducing magnetic data using a magnetic recording medium having a magnetic layer containing a magnetic material provided on a non-magnetic support, wherein the magnetic recording medium is a non-magnetic support. Is provided with a magnetic layer containing a magnetic substance,
In addition, the non-magnetic support is a magnetic recording medium having a layer containing a dye whose optical properties are changed by irradiation with energy rays in the middle part thereof, and the layer containing the dye has energy-saving properties.
Tracking detected by optical means from a layer containing a dye using a magnetic recording medium in which an optical pattern for a tracking servo signal based on a change in the optical property of the dye by line irradiation is recorded. While tracking the magnetic head using the servo signal,
A recording / reproducing method for a magnetic recording medium, which comprises recording / reproducing magnetic data. 7. The tracking servo signal includes a signal in which two types of signals having different wavelengths are superposed, the two types of signals are uniform, and the phase difference between the two types of signals is equal to each other. 7. The recording / reproducing method for a magnetic recording medium according to claim 6, wherein the recording and reproducing are sequentially different for each track.