JPH06243619A - Magnetic recording medium and tracking servo control device thereof - Google Patents

Abstract

(57) [Summary] [Purpose] Writing information even if the recording capacity is increased,
An object of the present invention is to provide a highly reliable magnetic recording medium that can be read properly and a tracking servo control device suitable for the magnetic recording medium. [Structure] A magnetic layer 12a and magnetic head tracking servo layers 10 and 11 composed of a layer containing a phosphor are provided.
Provided in a superposed state in the thickness direction of the magnetic recording medium,
The data tracks 14 formed on the magnetic layer 12a and the servo tracks 21 formed on the magnetic head tracking servo layers 10 and 11 are in a correspondence relationship, and are emitted from the phosphor in the magnetic head tracking servo layers 10 and 11. The magnetic head is configured to be tracked based on fluorescence.

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 flexible magnetic disk, a magnetic tape or a magnetic card and a tracking servo control device suitable for the magnetic recording medium, and more particularly to a tracking servo capable of optically tracking a magnetic head. Regarding the mechanism.

[0002]

2. Description of the Related Art In a flexible magnetic disk, a reference track is formed on the innermost circumference of a donut-shaped recording band of the flexible magnetic disk, and the reference track is separated from the reference track by a predetermined distance toward the outer side in the radial direction. It is known that a large number of concentric magnetic head tracking recesses are formed in a ring shape and data tracks are provided between the magnetic head tracking recesses (see, for example, Japanese Patent Application Laid-Open No. 2-1876969).

20 and 21 are an enlarged sectional view and a plan view for explaining this type of magnetic disk.

As shown in these figures, a magnetic layer 101 is provided on the surface of the base film 100, and a tracking servo groove 102 extends in the magnetic layer 101 in the rotational direction of the magnetic disk. For example, it is formed by means such as laser processing. A data track 103 is formed between the grooves 102 (FIG. 21).
reference).

On the other hand, in the case of the magnetic recording / reproducing apparatus, a beam 104 for tracking servo is formed on the surface of the magnetic disk.
And a light receiving element 106a, 10 for receiving the reflected light 105 from the surface of the magnetic disk.
6b, 106c, 106d (see FIG. 21).

The light beam 1 emitted from the light emitting element
04 is applied to the surface of the magnetic disk, and the reflected light from it is 1
05 to the light receiving elements 106a, 106b, 106c, 106
Light is received at d.

Since the groove 102 for tracking servo is formed in the magnetic layer 101 as described above, the light intensity reflected on the data track 103 and the light intensity reflected on the groove 102 are different. In the example shown in FIG. 21, the light receiving element 106
a and the total output value of 106b, and the light receiving elements 106c and 10
Tracking servo of a magnetic head (not shown) is performed so that both output values are equal by constantly comparing the total output value of 6d.

In the conventional magnetic disk, the magnetic layer 101 has a thickness of about 1 to 3 μm, and therefore the data track 103 is formed.
Since there is a clear difference between the light intensity reflected above and the light intensity reflected on the groove 102, good tracking servo was possible.

However, if the thickness of the magnetic layer is reduced to less than 1 μm in order to improve the overwrite characteristic of the magnetic disk, the reflection intensity on the surface of the magnetic layer tends to vary, and therefore proper tracking servo is performed. The problem of difficulty came out.

First, the relationship between the thickness of the magnetic layer and the overwrite characteristic will be described. The following Table 1 is a table in which the overwrite characteristics at each magnetic layer thickness are measured and summarized when the thickness of the magnetic layer is variously changed.

The overwrite characteristic is initially 150H.
The z signal is written on the data track, the 600 Hz signal is overwritten on the data track on which the signal is written, and the reproduction output of the remaining 150 Hz signal is measured.

The thickness of the magnetic layer was measured using a transmission electron microscope (TEM) H-700H manufactured by Hitachi, Ltd. Table 1 Thickness of magnetic layer (μm) Overwrite characteristics (dB) 0.21-42.2 0.27 -40.0 0.49-36.0 0.52-35.7 0.57-33. 3 0.75 -31.2 0.79 -30.3 0.90 -30.0 1.05-26.5 1.30-25.2 1.55-23.1 As is clear from this table When the thickness of the magnetic layer exceeds 1 μm, the overwrite characteristic is poor, but when it is less than 1 μm, good overwrite characteristics of −30 dB or less can be obtained. it can.

[0013]

Next, the light reflection characteristics of this ultrathin magnetic layer will be described with reference to FIG. This figure is a diagram in which samples having various thicknesses of the magnetic layer were prepared, and the relationship between the thickness of the magnetic layer and the light reflectance was experimentally obtained. In this experiment, an LED having a center wavelength of 880 nm was used as a light source, and the incident angle of light with respect to the magnetic layer surface was 20 degrees.

As is clear from this figure, there are regions with high light reflectance and regions with low light reflectance depending on the thickness of the magnetic layer. It is considered that this is due to the interference between the reflected light on the surface of the magnetic layer and the return light that passes through the magnetic layer, is reflected at the interface with the base film, passes through the magnetic layer again, and appears on the surface.

Therefore, if the thickness of the magnetic layer varies, the light reflectance fluctuates, and there is a concern that proper tracking servo cannot be performed. In order to prevent this from happening, it is necessary to strictly control the thickness of the magnetic layer during the manufacturing process of the magnetic recording medium, which lowers the production efficiency and increases the manufacturing cost. It has drawbacks such as

On the other hand, the increase in the recording capacity of the magnetic recording medium is
Although it is achieved by improving the recording density and the track density, the magnetic disk is aiming for a large capacity mainly by improving the track density by optical servo.

To explain this concretely, for example, 3.5
In the case of an inch-inch flexible magnetic disk with a recording capacity of 21 MB, the track density is 1245 TPI, and the track width of the data track is 15 μm.
Thus, the servo groove width for tracking servo becomes 5.4 μm. When the track density is doubled to 2490 TPI on the same size magnetic disk, the recording capacity is doubled, but the track width of the data track is 7.
At 5 μm, the servo groove width becomes 2.7 μm, and it is necessary to reduce the width dimension to half or less.

In order to accurately read the signal from the recording medium, it is preferable that the magnetic signal and the optical signal are as large as possible. However, when both the data track and the servo track are formed on the same plane of the recording medium, it is inevitable. At least one is sacrificed. At this time, if the data track is sacrificed, writing and reading of information will be hindered, and if the servo track is sacrificed, proper tracking cannot be performed.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a highly reliable magnetic recording medium in which information can be written and read properly even if the recording capacity is increased, and its magnetic field. It is to provide a tracking servo control device suitable for a recording medium.

[0020]

In order to achieve the above object, a first aspect of the present invention provides a magnetic recording medium having a base made of a non-magnetic material and a magnetic layer formed above the base. Layer and a magnetic head tracking servo layer formed of a layer containing a phosphor are provided in an overlapping state in the thickness direction of the magnetic recording medium, and the data track formed on the magnetic layer and the magnetic head tracking layer are provided. The servo track formed in the servo layer has a correspondence relationship, and the magnetic head is configured to be tracked based on the fluorescence emitted from the phosphor in the magnetic head tracking servo layer. It is a thing.

In order to achieve the above object, the second aspect of the present invention is such that a magnetic layer and a magnetic head tracking servo layer composed of a layer containing a phosphor are superposed in the thickness direction of a magnetic recording medium. Light for exciting a phosphor in the magnetic head tracking servo layer of a magnetic recording medium provided with a data track formed in the magnetic layer and a servo track formed in the magnetic head tracking servo layer in a corresponding relationship. A light-receiving element group for irradiating light, a light-receiving element group including a plurality of light-receiving elements for receiving fluorescence emitted from the magnetic head tracking servo layer, and arranged on the optical path from the magnetic recording medium and in front of the light-receiving element group. And a filter that blocks the reflected light from the surface of the magnetic recording medium and transmits only the fluorescence emitted from the servo layer for magnetic head tracking. Servo signal calculation means for inputting a signal from the light receiving element group to calculate and output a servo signal; and a magnetic head servo control section for correcting the position of the magnetic head based on the servo signal from the servo signal calculation means. It is characterized by having.

In order to achieve the above object, a third aspect of the present invention is to provide a light emitting element for irradiating the surface of a magnetic recording medium with light, and a first optical path and a first optical path disposed on the optical path from the magnetic recording medium. Optical path branching means for branching into two optical paths, and a light head tracking servo layer arranged on the first optical path for blocking reflected light from the surface of the magnetic recording medium and emitting from a magnetic head tracking servo layer provided on the magnetic recording medium. A filter that transmits only the emitted fluorescent light, a first light receiving element group that includes a plurality of light receiving elements that receive the light that has passed through the filter, and a reflected light from the surface of the magnetic recording medium that is arranged on the second optical path. A second light receiving element group composed of a plurality of light receiving elements for receiving
The signals from the light receiving element groups and the second light receiving element groups can be input, and the signal judging means for selecting one of the signals from both the light receiving element groups as an effective signal, and the judgment by the signal judging means Based on a servo signal calculating means for calculating and outputting a servo signal based on one of the signals from the first light receiving element group and the second light receiving element group, and based on the servo signal from the servo signal calculating means A magnetic head servo controller for correcting the position of the magnetic head, and when the signals from the first light receiving element group and the second light receiving element group are both inputted to the signal judging means, the magnetic recording being used. It is determined that the medium is a magnetic recording medium having a magnetic head tracking servo layer containing a phosphor, and the signal from the first light receiving element group is selected as valid, and the second light receiving element is selected. When only the signal from the subsidiary group is input to the signal determining means, it is determined that the magnetic recording medium used is a magnetic recording medium having a magnetic head tracking recess formed on the surface of the magnetic layer, and the second recording medium is used. It is characterized in that the signal from the light receiving element group is selected as valid.

In order to achieve the above-mentioned object, a fourth aspect of the present invention is to provide a light emitting element for irradiating the surface of a magnetic recording medium with light, and an optical element arranged on the optical path from the magnetic recording medium, and A light receiving element group including a filter that blocks reflected light and transmits only fluorescence emitted from the magnetic head tracking servo layer provided on the magnetic recording medium, and a plurality of light receiving elements that receive the light that has passed through the filter. A filter moving means for arranging the filter on the optical path or removing the filter from the optical path, a signal judging means for inputting a signal from the light receiving element group and judging the presence or absence of filter transmitted light, Servo signal calculating means for calculating and outputting a servo signal based on a signal from the light receiving element group, and the position of the magnetic head is corrected based on the servo signal from the servo signal calculating means. And a magnetic head servo control unit for detecting the presence of light transmitted through the filter by the signal determining means, the magnetic recording medium used is a magnetic recording medium having a magnetic head tracking servo layer containing a phosphor. Judgment is made, a filter is arranged on the optical path, and if the signal judging means detects the absence of light transmitted through the filter, the magnetic recording medium in use has a magnetic layer with a magnetic head tracking recess formed on the surface of the magnetic layer. When the recording medium is determined to be a recording medium, the filter moving means is driven so as to remove the filter from the optical path.

[0024]

According to the first aspect of the present invention, the magnetic layer and the servo layer for magnetic head tracking are provided in an overlapping manner in the thickness direction of the magnetic recording medium, and the data track formed on the magnetic layer and the magnetic head tracking are formed. Since the servo track formed in the servo layer has a corresponding relationship, it is not necessary to form the servo track in the magnetic layer, and there is a margin in the track width of the data track in the magnetic layer, and a large output can be obtained. The track density can be increased.

Further, since the fluorescence emitted from the phosphor in the magnetic head tracking servo layer is received to perform the tracking of the magnetic head, the conventional tracking servo is performed based on the difference in the light reflection intensity. The output of the light receiving element is larger than that of what is performed, so that the tracking servo is properly performed.

In the second aspect of the invention, since the fluorescent substance in the magnetic head tracking servo layer emits fluorescence almost at the same time as the irradiation from the light emitting device, the reflected light on the surface of the magnetic recording medium is blocked in front of the light receiving device group. By disposing a filter that transmits only the fluorescence from the servo layer for tracking the magnetic head, the tracking of the magnetic head is accurately performed and the reliability can be improved.

In the third and fourth inventions, a magnetic recording medium having a phosphor in a servo layer for magnetic head tracking and a magnetic recording medium having a tracking recess on the surface of the magnetic layer can be used in common. Moreover, it is possible to automatically determine which magnetic recording medium is used, and it is possible to perform control according to each tracking servo, which is very convenient in use.

[0028]

Embodiments of the present invention will now be described with reference to the drawings.
1 is an exploded perspective view of a part of a magnetic disk cartridge according to an embodiment, FIG. 2 is an enlarged sectional view of a magnetic sheet, and FIG.
FIG. 3 is a plan view of a magnetic disk.

As shown in FIG. 1, the magnetic disk cartridge comprises a cartridge case 1, a flexible magnetic disk 2 rotatably housed therein, and a shutter 3 slidably mounted on the cartridge case 1.
And a cleaning sheet (not shown) welded to the inner surface of the cartridge case 1.

The cartridge case 1 is an upper case 1
a and a lower case 1b, which are injection molded from a hard synthetic resin such as ABS resin mixed with an antistatic agent.

An opening 4 for inserting the rotary drive shaft is formed in a substantially central portion of the lower case 1b, and a rectangular head insertion opening 5 is formed in the vicinity thereof. Although not shown, a head insertion opening 5 is similarly formed in the upper case 1a.

In the vicinity of the front surfaces of the upper case 1a and the lower case 1b, a recess 6 is formed which is slightly lowered in order to regulate the sliding range of the shutter 3, and the head insertion port 5 is located at an intermediate position of the recess 6. It is open.

The magnetic disk 2 is, as shown in FIG.
It is composed of a donut-shaped flexible magnetic sheet 7 and a center hub 8 made of metal or synthetic resin, which is inserted into a central hole of the magnetic sheet 7 and adhered thereto.

The magnetic sheet 7 is a base film 9
A phosphor layer 10 uniformly formed on the upper surface thereof, a light transmitting / blocking layer 11 formed thereon, a magnetic layer 12a formed further thereon, and a lower surface of the base film 9. The magnetic layer 12b is formed into a laminated structure.

The base film 9 is made of a synthetic resin film such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polyimide. A white pigment such as titanium oxide is dispersed and held in the base film 9 and has a property of reflecting infrared rays including near infrared rays.

The phosphor layer 10 is mainly composed of phosphor fine particles which are excited by irradiation of infrared rays (including near infrared rays) and emit fluorescence, and a binder which disperses and holds them.

The fluorescent fine particles are, for example, NdP.
₅ O ₁₄ , LiNdP ₄ O ₁₂ and Al ₃ Nd (B
An inorganic compound selected from the group of O ₃ ) ₄ or an inorganic compound represented by the following general formula.

General formula Ln _1-XY Nd _X Yb _Y Z Ln in the formula is Bi, Ge, Ga, Gd, In, La,
Represents one or more elements selected from the group of Lu, Sb, Sc and Y.

In the formula, Z is A ₅ (MO ₄ ) ₄ A is at least one element selected from the group of K and Na, and M is at least one element selected from the group of W and Mo. Represent

D ₃ (BO ₃ ) ₄ D represents at least one element selected from the group consisting of Al and Cr.

P ₅ O ₁₄ A ₃ (PO ₄ ) ₂ A represents one or more elements selected from the group of K and Na.

Na ₂ Mg ₂ (VO ₄ ) ₃ A '(MO ₄ ) ₂ A'is one or more elements selected from the group of Li, Na and K, and M is selected from the group of W and Mo. Represents one or more elements.

Then, in the x and y in the formula, Z is A ₅ (M
O ₄ ) ₄ is a value in the range of 0.25 ≦ x ≦ 0.99 and 0.01 ≦ y ≦ 0.75, and Z is D ₃ (B
When O ₃₎ is _4, 0.10 ≦ x ≦ 0.99 and 0.01 ≦ y ≦ 0.90 range of values, when Z is _{P 5 O 14, 0.05 ≦ x} ≦ 0. 98 and 0.02 ≦ y ≦
Values in the range of 0.95, when Z is A ₃ (PO ₄ ) ₂ , 0.02 ≦ x ≦ 0.98 and 0.02 ≦ y ≦ 0.
A value in the range of 98, when Z is Na ₂ Mg ₂ (VO ₄ ) ₃ , 0.57 ≦ x ≦ 0.90 and 0.10 ≦ y ≦
A value in the range 0.43, when Z is A ′ (MO ₄ ) ₂ , 0.20 ≦ x ≦ 0.95 and 0.05 ≦ y ≦ 0.
The value is in the range of 80.

Specifically, for example, Nd _0.8 Yb _0.2 Na ₅
(WO ₄ ) ₄ , Nd _0.9 Yb _0.1 Na ₅ (Mo
O ₄ ) ₄ , Y _0.1 Nd _0.75 Yb _0.15 (WO ₄ ) ₄ , Nd
_0.8 Yb _0.2 Na ₅ (Mo _0.5 W _0.5 O ₄ ) ₄ , Bi
_0.1 Nd _0.75 Yb _0.15 K ₅ (MoO ₄ ) ₄ , La _0.1 N
d _0.8 Yb _0.1 (Na _0.9 K _0.1 ) ₅ (WO ₄ ) ₄ , N
d _0.9 Yb _0.1 Al ₃ (BO ₃ ) ₄ or the like can be used.

Further, an inorganic compound represented by the following general formula can also be used.

General formula EF _1-XY Nd _X Yb _Y P ₄ O ₁₂ E in the formula is one or more elements selected from the group of Li, Na, K, Rb and Cs, and F in the formula is Sc, Y,
It represents one or more elements selected from the group consisting of La, Ce, Gd, Lu, Ga, In, Bi and Sb.

X and y in the formula are values in the following range.

0.05 ≦ x ≦ 0.999 0.001 ≦ y ≦ 0.950 x + y ≦ 1.0 Specifically, for example, LiNd _0.9 Yb _0.1 P ₄ O ₁₂ , Li
Bi _0.2 Nd _0.7 Yb _0.1 P ₄ O ₁₂ , NaNd _0.9 Yb
_0.1 P ₄ O ₁₂ or the like can be used.

Thus, the phosphor to which neodymium (Nd) is added as an activator is chemically stable and has a high excitation efficiency, so that it can be used for a prize.

The binder for forming the phosphor layer 10 has a property of transmitting infrared rays, and is made of, for example, wax, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, polyester, polyurethane or carbonate. Used alone or as a mixture. If necessary, a plasticizer, a surfactant and the like can be added as appropriate.

FIG. 2 described above is a cross-sectional view taken along a direction orthogonal to the traveling direction of the magnetic disk 2, that is, along the radial direction of the magnetic disk 2. As shown in the figure,
The blocking layer 11 is composed of a transmitting portion 11a that transmits infrared rays emitted from the outside and fluorescence from the fluorescent layer 10 and a blocking portion 11b that blocks transmission of the infrared rays and fluorescent light. The transmitting portion 11a and the blocking portion 11a. Many 11b are formed alternately along the radial direction of the magnetic disk 2.

The infrared rays 34 radiated from the outside pass through the transmitting portion 11a and irradiate the phosphor layer 10 located therebelow, whereby the phosphor fine particles in the phosphor layer 10 are excited to emit fluorescence 35. Then, the fluorescence 35 passes through the transmissive portion 11a and appears on the surface. On the other hand, since the infrared ray 34 radiated toward the blocking section 11b is blocked at that portion, the blocking section 11b
The phosphor layer 10 under b is not excited and therefore does not emit light.

Further, as shown in FIG. 5, the transmission part 11a is formed discontinuously or continuously along the running direction X of the magnetic disk 2, and the blocking part 11b is continuous along the running direction X of the magnetic disk 2. Is formed.

Therefore, in this embodiment, the combination of the phosphor layer 10 and the transmissive portion 11a constitutes a light emitting portion, and the light emitting portion constitutes a servo track 21. Further, the part corresponding to the blocking part 11b becomes a non-light emitting part, and
A non-light emitting area between one servo track 21 and an adjacent servo track 21 corresponds to the blocking section 11b.

6 and 7 show examples of the servo tracks 21, FIG. 6 shows an example in which the discontinuous servo tracks 21 are concentrically formed, and FIG. 7 shows the continuous servo tracks 21. Each of the examples is formed concentrically.

The magnetic layers 10a and 10b are made of ferromagnetic powder,
It is composed of a mixture of binder, polishing powder and lubricant.

Examples of the ferromagnetic powder include barium ferrite, strontium ferrite, α-Fe and Co.
-Ni, Co-P, γ- Fe 2 O 3, Fe 3 O 4, Co
Γ-Fe ₂ O ₃ containing, γ-Fe ₃ O ₄ containing Cr, CrO
₂ , fine powders of Co, Fe-Ni, etc. are used.

As the binder, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, urethane resin, polyisocyanate compound, radiation curable resin and the like are used.

As the polishing powder, for example, aluminum oxide, chromium oxide, silicon carbide, silicon nitride or the like is used. The addition rate of the polishing powder was about 0.
1-25% by weight is suitable.

Examples of the lubricant include higher fatty acids such as stearic acid and oleic acid, higher fatty acid esters thereof, liquid paraffin, squalane, fluorine resin,
Fluorine oil can be used. The appropriate addition rate of this lubricant is about 0.1 to 25% by weight with respect to the magnetic powder.

A specific example of the composition of the magnetic coating material is as follows.

Magnetic paint composition example 100 parts by weight of barium ferrite (Hc: 530 [Oe], saturation magnetization: 57 [emu / g], average particle size: 0.04 [μm]) Vinyl chloride-vinyl acetate-vinyl alcohol Copolymer 11.0 parts by weight Urethane resin 6.6 parts by weight Trifunctional isocyanate compound 4.4 parts by weight Aluminum oxide powder (average particle size 0.43 [μm]) 15 parts by weight Carbon black 2 parts by weight Oleyl oleate 7 parts by weight Cyclohexanone 150 parts by weight Toluene 150 parts by weight The composition of the above-mentioned magnetic coating composition example is well mixed and dispersed in a ball mill to prepare a magnetic coating, which is applied to both sides of a 62 μm polyethylene terephthalate (PET) base film. , Apply so that the dry average thickness is 0.89 μm, dry, and then calender Magnetic layer 10 Te
a and 10b are formed respectively.

The magnetic disk 2 thus constructed
As shown in FIG. 3, a reference track 13 is formed on the surface of the magnetic layer 10a at the innermost circumference by embossing or the like. A number of data tracks 14 are formed on the outer peripheral side of the reference track 13. In this embodiment, the track density is 2490 TPI and the track width is 8.
The track pitch is 7 μm and the track pitch is 10.2 μm.

The reference track 13 and the data track 14 are provided concentrically with respect to the rotation center 15 of the magnetic disk 2.

As shown in FIG. 4, the reference track 13 extends along the traveling direction X of the magnetic disk 2, and is symmetrical with respect to an arbitrary point 17 on the center line 16 of the reference track 11. A rectangular reference recess region 18A and a reference recess region 18B are formed in pairs. This reference recess area 18A
Adjacent to (in front of the reference recessed region 18B) and next to the reference recessed region 18B (rearward to the reference recessed region 18A), there are no recessed flat portions 19A and 1
There is 9B.

These sets of reference recessed regions 18
The reference track 13 is formed by forming a large number of A, 18B and plane portions 19A, 19B intermittently or continuously along the traveling direction X of the magnetic disk.

A predetermined signal is recorded in advance on the reference track 13, and the magnetic head scans the reference track 13. Based on the output waveform at that time, the center position of the magnetic head (magnetic gap) is determined. Can be guided on the center line 16 of the reference track 13.

As shown in FIG. 2, the magnetic layer 12a is transparent to light.
The magnetic layer 11b is provided on the upper side of the blocking layer 11, the magnetic layer 11b is provided on the lower side of the base film 9, and the magnetic layer 12a and the light transmitting / receiving layer are provided.
Although the blocking layer 11 and the magnetic layer 11b are in a vertical relationship with each other, the servo track 21 and the magnetic layers 12a and 12b each including the combination of the phosphor layer 10 and the light transmitting portion 11a of the light transmitting / blocking layer 11 are arranged. The data tracks 14 of FIG.

FIG. 8 schematically shows this relationship. For example, when the magnetic head is tracked to the innermost data track DT1 in the data track 14, the innermost track in the servo track 21 Servo track S
T1 and the servo track ST2 next to it are used,
Spot-shaped light is emitted from the servo track ST1 to the servo track ST2. Similarly, when the magnetic head is tracked to the second data track DT2, spot-shaped light is emitted from the second servo track ST2 to the third servo track ST3. In this way, the tracking servo of one data track 14 is performed using the two servo tracks 21.

The phosphor fine particles in the phosphor layer 10 are excited by infrared rays to emit light, but in order to effectively excite the phosphor fine particles, the light reflectance of the base film 9 is 1% or more in this embodiment. , Preferably 20% or more, more preferably 50% or more. That is, the base film 9 having a high reflectance is used, or the base film 9 is used.
By providing a high reflectance to the base film 9
Infrared is reflected on the surface of the to promote the excitation of phosphor fine particles. By dispersing and holding a white pigment such as titanium oxide in the base film 9 as described above, the reflectance of the base film 9 can be increased.

Table 2 below shows the results of measuring the output voltage and S / N of the phosphor layer 10 when the reflectance of the base film 9 was variously adjusted by adjusting the content of the white pigment. is there.

Table 2 Base film reflectance (%) Output voltage (mV) S / N 1 18 1.00 2 23 1.10 5 36 1.25 20 61 61 1.61 30 77 1.83 50 120 2.51 60 130 2.93 80 580 3.60 As is apparent from this table, the reflectance of the base film is 1% or more, preferably 20% or more, more preferably 5% or more.
When it is 0% or more, the excitation of the phosphor fine particles is effectively performed, the output voltage is sufficiently taken, and a high S / N is obtained.

FIG. 9 is a characteristic diagram showing the relationship between the film thickness of the phosphor layer 10 and the output voltage. A curve A in the figure is a characteristic curve showing the relationship between the film thickness and the output voltage when the phosphor layer 10 is formed on the base film 9 containing a white pigment (titanium oxide) and having a reflectance of 80%. The straight line B indicates the phosphor layer 10
Is a line indicating an output level at which the output is 1.6 times the output voltage of only the base film 9 (having a reflectance of 80%).

The results of various experiments conducted by the present inventors, the phosphor layer 1
When the output of 0 is lower than the straight line B, the fluorescence from the phosphor layer 10 cannot be sufficiently detected. Therefore, the output voltage of the phosphor layer 10 is 1.6 times the output voltage of the base film 9 only (straight line B).
The above is necessary, and the minimum thickness of the phosphor layer 10 at this time is 0.5 μm as is apparent from this figure. The output voltage increases as the thickness of the phosphor layer 10 increases, but becomes almost constant when the film thickness reaches about 50 μm. This tendency is almost the same when the reflectance of the base film 9 is low.

As shown in FIG. 2, in order to perform tracking servo, the light emitting element 22 and the light receiving element group 23 are arranged close to the magnetic layer 12a. A part of the infrared rays 34 emitted from the light emitting element 22 is reflected on the surface of the magnetic layer 12a, and the reflected light 36 goes toward the light receiving element group 23 side.
Most of the infrared rays 34 pass through the magnetic layer 12a (as described above, the magnetic layer 12a is an extremely thin layer of less than 1 μm,
The infrared ray 34 can be easily transmitted. ) Light transmission
It reaches the blocking layer 11. The irradiation area of the infrared rays 34 on the light transmitting / blocking layer 11 extends over one transparent portion 11a, the blocking portion 11b adjacent to the transparent portion 11a, and the transparent portion 11a adjacent to the transparent portion 11a. The phosphor layer 10 is excited. Due to this excitation, the phosphor layer 10
Emits fluorescence 35, passes through the magnetic layer 12a, and travels toward the light receiving element group 23 side.

Immediately before the light receiving element group 23, the magnetic layer 12a is formed.
A filter 24 having an optical characteristic of blocking the reflected light 36 from the fluorescent substance layer 10 and transmitting the fluorescent light 35 from the fluorescent substance layer 10 is provided, and the light emitting portion (composed of the fluorescent substance layer 10 and the transmitting portion 11a).
The light-receiving element group 23 receives only the fluorescent light 35 from the.

FIG. 10 is a spectrum characteristic diagram, and the curve C in the figure shows the emission spectrum of the semiconductor laser diode light emitting element 22 used in this embodiment and the magnetic layer 12a.
A spectral curve of the reflected light 36 from the above, curve D is an emission spectrum when LiNdP ₄ O ₁₂ is used as the phosphor. A curve E is a characteristic curve showing the cutoff region and the transmission region of the filter 24.

The light emitting element 22, the light receiving element group 23, the filter 24 and the like are integrally incorporated in one magnetic head 25a as shown in FIG. FIG. 12 is a diagram showing an arrangement state of the light receiving elements 23a to 23d in the light receiving element group 23. In the case of this embodiment, the light receiving element group 23 is composed of four light receiving elements 23a to 23d, and is optically arranged so as to straddle the two servo tracks 21, 21. Then, the fluorescent light 35 emitted from the light emitting portion is received by the light receiving element 2
Light is received by 3a to 23d, and the outputs of the respective light receiving elements 23a to 23d are input to the servo signal calculation unit 26 as shown in FIG. The deviation amount of the magnetic head with respect to the data track 14 is calculated from the output state from each of the light receiving elements 23a to 23d, and the servo signal is output to the head servo control unit 27. The head servo controller 27 adjusts the position of the magnetic head 25 based on this servo signal.

In this embodiment, the light receiving element group 23 is composed of four light receiving elements 23a to 23d, but the present invention is not limited to this, and two or more light receiving element groups 23 (for example, 2 to 4).

FIG. 13 is an enlarged sectional view of the magnetic sheet 7 according to the second embodiment of the present invention. This embodiment differs from the magnetic sheet 7 used in the first embodiment in that a transparent resin film is used as the base film 9. Then, the transmitting portion 11a of the light transmitting / blocking layer 11
When the fluorescent layer 10 is excited by passing through, the fluorescent light 35 emitted from the fluorescent layer 10 is emitted from the base film 9 and the lower magnetic layer 12.
The light is transmitted through b and received on the opposite side.

FIG. 14 is an enlarged sectional view of the magnetic sheet 7 according to the third embodiment of the present invention. In the case of this embodiment, the reflective layer 28 is formed on the base film 9. The reflective layer 28 is made of a material having a high reflectance such as aluminum, and the reflective portions 28a and the non-reflective portions 28b are alternately formed along the radial direction of the magnetic disk 2.

The patterning of the reflective portion 28a and the non-reflective portion 28b can be easily performed by, for example, vapor deposition, sputtering and etching.

The phosphor layer 10 and the magnetic layer 12a are uniformly formed on the reflective layer 28. In addition, the reflector 28
In order to have a clear difference in the fluorescence intensity emitted from the phosphor layer 10 between the place where a is present and the place where it is the non-reflective portion 28b, the content rate of the phosphor fine particles is reduced or the phosphor layer is used. The film thickness of 10 is made thin.

When the area where the reflecting portion 28a is present is illuminated,
A part of the irradiation light (infrared ray) is reflected by the reflecting portion 28a, and the phosphor layer 10 thereon can be effectively excited. On the other hand, since the non-reflecting portion 28b does not reflect the irradiation light (infrared ray), the fluorescence intensity is extremely weak, and it can be optically distinguished from the place where the reflecting portion 28a exists.

FIG. 15 is an enlarged sectional view of the magnetic sheet 7 according to the fourth embodiment of the present invention. In the case of this embodiment, the pattern of the phosphor layer 10 is directly formed on the base film 9 in which the white pigment is dispersed and held by printing or the like. By forming a binder layer 29 that transmits infrared rays 34 and fluorescence 35 on the phosphor layer 10, surface flatness is imparted, and a magnetic layer 12a is provided thereon.

The binder layer 29 is made of wax, for example.
Vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, polyester, polyurethane, carbonate, epoxy resin and the like are used.

FIG. 16 is an enlarged sectional view of the magnetic sheet 7 according to the fifth embodiment of the present invention. In the case of this embodiment, the magnetic layer 12a is directly formed on the base film 9, and the pattern of the phosphor layer 10 is formed thereon by printing or the like. Infrared light 34 and fluorescent light 35 are formed on the phosphor layer 10.
By forming the binder layer 29 that transmits the light, the phosphor layer 10 is protected by the binder layer 29.

FIG. 17 is an enlarged sectional view of the magnetic sheet 7 according to the sixth embodiment of the present invention. This embodiment differs from the magnetic sheet 7 shown in FIG. 2 of the first embodiment in that
The magnetic layer 12a is not formed on the light transmitting / blocking layer 11. Therefore, the magnetic head tracking servo layer composed of the phosphor layer 10 and the light transmitting / blocking layer 11 is dedicated to tracking of the lower magnetic layer 12b.

In the first embodiment shown in FIG. 2, the second portion shown in FIG.
Similarly, in the embodiment, the transmission portion 11a of the light transmission / blocking layer 11 and the shielding portion are blocked, and in the third embodiment shown in FIG. 14, the reflection portion 28a and the non-reflection portion 28b of the reflection layer 28 are used. In the embodiment, the phosphor layer 10 is provided with and without the phosphor layer 10, and the fifth embodiment shown in FIG. 16 is also provided with the phosphor layer 10 without the phosphor layer 10. In the sixth embodiment shown in FIG. Transmission / blocking layer 1
The light-transmitting portion 11a and the light-transmitting portion 11a form one light-emitting portion that emits light in the phosphor layer 10 and a non-light-emitting portion that does not emit light in some phosphor layer 10.

The light emitting portion and the non-light emitting portion are alternately formed along the relative movement direction of the magnetic recording medium and the light emitting element-light receiving element group, that is, the radial direction of the magnetic disk 2.
The ratio (A1: A2) of the area (A1) of one light emitting portion to the area (A2) of one non-light emitting portion is 1: 0.5 to 1.5.
It is better to regulate to the range of, preferably 1: 0.75-1.25. The area ratio between the light emitting portion and the non-light emitting portion is 1:
If it is less than 0.5 or exceeds 1: 1.5, it becomes difficult to optically distinguish the light emitting portion and the non-light emitting portion, and there is a concern that the tracking servo accuracy may be deteriorated. Therefore, the area ratio between the light emitting portion and the non-light emitting portion should be controlled within the above range.

FIG. 18 is a schematic block diagram showing a first modification of the tracking servo control device of the present invention. The tracking servo control device shown in FIGS. 2, 11 and 12 is a device that can be used only for the magnetic recording medium provided with the phosphor layer 10. In the modification shown in FIG. 18, a magnetic recording medium provided with a phosphor layer 10 and a phosphor layer 1 are provided.
Both of the magnetic recording media in which 0 is not provided and a recess for tracking is formed can be used.

That is, the beam splitter 30 is arranged on the optical path from the magnetic recording medium (magnetic disk 2), and only the light from the phosphor layer 10 is provided on the first optical path branched from the beam splitter 30. A filter 24 that transmits light and a first light receiving element group 23 are arranged. Further, a second light receiving element group 31 for arranging reflected light from the surface of the magnetic recording medium (magnetic disk 2) on the second optical path branched from the beam splitter 30.

In the figure, 32 is a CPU, 33 is its CPU 3
The reference numeral 26 in FIG. 2 is a servo signal calculator in the CPU 32. Further, λ ₁ is the reflected light from the magnetic recording medium (magnetic disk 2), and λ ₂ is the fluorescence from the phosphor layer 10.

FIG. 18A shows the case where a magnetic recording medium provided with the phosphor layer 10 is used, and FIG.
Shows the case where a magnetic recording medium having a recess for tracking is used.

When the magnetic recording medium provided with the phosphor layer 10 as shown in FIG. 18A is used, the reflected light λ ₁ from the magnetic recording medium (magnetic disk 2) and the phosphor layer 10 are used. fluorescence lambda ₂ of both light (λ ₁ + λ ₂₎ is incident on the beam splitter 30.

Then, the beam splitter 30 splits the light into two optical paths. In the first optical path, the reflected light λ ₁ is cut by the filter 24, only the fluorescence λ ₂ is transmitted, and the first light receiving element group 23 receives the light. . Both lights (λ ₁ + λ ₂ ) are received by the second light receiving element group 31 in the second optical path.

Signal S ₂ from the first light receiving element group 23
And the signal S ₁ from the second light receiving element group 31 is input to the determination unit 33, and when the signal S ₂ is present, the determination unit 33 causes the fluorescent material layer 1 to be detected.
It is determined that the magnetic recording medium provided with 0 is used. Then, the signal S ₂ from the first light receiving element group 23 is made valid, the signal S ₁ from the second light receiving element group 31 is made invalid, and the selected signal S _{2 is changed} to the servo signal calculation unit 26.
To perform tracking servo as described above (see FIG. 11).

When a magnetic recording medium in which a tracking recess is formed as shown in FIG. 18B is used, only the reflected light λ ₁ from the magnetic recording medium (magnetic disk 2) is used, which is the beam splitter. It is incident on 30.

The beam splitter 30 splits the light into two optical paths, and the reflected light λ ₁ is cut by the filter 24 in the first optical path. Therefore, the first light receiving element group 23
The signal S _{2 from} is not output.

On the other hand, in the second optical path, the reflected light λ
₁ is received by the second light receiving element group 31, and the signal S ₁ is input to the determination unit 33 to determine that the signal is valid. Then, the signal S ₁ is transmitted to the servo signal calculator 26 to perform the tracking servo as described above (see FIG. 11).

FIG. 19 is a schematic block diagram showing a second modification of the tracking servo control device of the present invention. In the modification shown in the figure, both the magnetic recording medium provided with the phosphor layer 10 and the magnetic recording medium having the recessed portion for tracking can be used.

In the case of this modification, the beam splitter 30
Is not used, magnetic recording medium (magnetic disk 2)
A filter 24 is arranged on the optical path from the electromagnetic wave, and is movable by an electromagnetic solenoid 40.

When the electromagnetic solenoid 40 is not energized, the filter 24 is on the optical path of the magnetic recording medium (magnetic disk 2). Then, when performing the tracking servo, the determination unit 33 determines whether or not there is the signal S ₂ from the light receiving element group 23. It signals S ₂ if the signal S ₂ is input
Is transmitted to the servo signal calculation unit 26 to perform the tracking servo as described above (see FIG. 11).

If the signal S ₂ is not input, the solenoid drive signal S ₃ output from the determination unit 33 drives the electromagnetic solenoid 40 to remove the filter 24 from the optical path, and the filter 24 is removed from the magnetic recording medium (magnetic disk 2). Reflected light λ ₁
Can be directly received by the light receiving element group 23. As a result, the signal S ₁ can be output from the light receiving element group 23, and the system is such that tracking servo is performed based on this signal S ₁ (see FIG. 11).

[0105]

According to the first aspect of the present invention, the magnetic layer and the servo layer for magnetic head tracking are provided in an overlapping state in the thickness direction of the magnetic recording medium, and the data track and the magnetic head tracking formed on the magnetic layer. Since there is a correspondence relationship with the servo track formed in the servo layer for use, it is not necessary to form the servo track in the magnetic layer, the track width of the data track in the magnetic layer has a margin, and a large output can be obtained. Moreover, the track density can be increased.

Further, since a servo track having a sufficient track width can be formed in the servo layer, the tracking servo can be properly performed even if the density is increased, and the reliability can be improved.

To describe a specific example of this, for example, in a 3.5-inch flexible magnetic disk, when the recording capacity is 80 MB, the track density is 2490TP.
I, the track width of the data track at that time is 8.7 μm, and the servo groove width for tracking servo is 5.1 μm. If the magnetic disk of the same size has a track density of 2988 TPI, the recording capacity is 1.5 times, the track width of the data track is 7.5 μm, and the servo groove width for the tracking servo is 4.2 μm. Even if the capacity is increased, the track width of the data track and the servo groove width for the tracking servo can be sufficiently secured.

Further, since the fluorescence emitted from the phosphor in the magnetic head tracking servo layer is received to perform tracking of the magnetic head, tracking servo is performed based on the conventional difference in light reflection intensity. The output of the light receiving element is larger than that of the light receiving element, so that the tracking servo is properly performed.

In the second invention, since the fluorescent substance in the servo layer for magnetic head tracking emits fluorescence almost at the same time as the irradiation from the light emitting element, the reflected light on the surface of the magnetic recording medium is blocked in front of the light receiving element group. By arranging a filter that transmits only the fluorescence from the servo layer for magnetic head tracking, the tracking of the magnetic head is accurately performed,
The reliability can be improved.

In the third and fourth aspects, the magnetic recording medium having the phosphor in the servo layer for magnetic head tracking and the magnetic recording medium having the tracking recess on the surface of the magnetic layer can be used in common, and The magnetic recording medium can be automatically discriminated, and control according to each tracking servo is possible, which is very convenient in use.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view of a magnetic disk cartridge according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the magnetic sheet according to the first embodiment of the present invention.

FIG. 3 is a plan view of a magnetic disk.

FIG. 4 is an enlarged plan view for explaining a reference track.

FIG. 5 is a plan view for explaining a servo track.

FIG. 6 is a plan view for explaining a servo track.

FIG. 7 is a plan view for explaining a servo track.

FIG. 8 is a schematic diagram for explaining a correspondence relationship between servo tracks and data tracks.

FIG. 9 is a characteristic diagram showing the relationship between the thickness of the phosphor layer and the output voltage.

FIG. 10 is a spectrum characteristic diagram of each light.

FIG. 11 is a block diagram for explaining tracking control of a magnetic head.

FIG. 12 is an explanatory diagram showing an arrangement state of light receiving elements.

FIG. 13 is an enlarged sectional view of a magnetic sheet according to a second embodiment of the present invention.

FIG. 14 is an enlarged sectional view of a magnetic sheet according to a third embodiment of the present invention.

FIG. 15 is an enlarged sectional view of a magnetic sheet according to a fourth embodiment of the present invention.

FIG. 16 is an enlarged sectional view of a magnetic sheet according to a fifth embodiment of the present invention.

FIG. 17 is an enlarged sectional view of a magnetic sheet according to a sixth embodiment of the present invention.

FIG. 18 is a schematic configuration diagram for explaining a first modified example of the tracking servo control device in the present invention.

FIG. 19 is a schematic configuration diagram for explaining a second modified example of the tracking servo control device in the present invention.

FIG. 20 is a partially enlarged sectional view of a conventionally proposed magnetic disk.

FIG. 21 is a partially enlarged plan view of the magnetic disk.

FIG. 22 is a characteristic diagram showing the relationship between the film thickness of the magnetic layer and the reflectance.

[Explanation of symbols]

 2 magnetic disk 7 magnetic sheet 9 base film 10 phosphor layer 11 light transmitting / blocking layer 11a transmitting part 11b blocking part 12a, 12b magnetic layer 14 data track 21 servo track 22 light emitting element 23, 31 light receiving element group 23a-23d light receiving element 24 Filters 25a, 25b Magnetic Head 26 Servo Signal Calculation Section 27 Head Servo Control Section 28 Reflective Layer 29 Binder Layer 30 Beam Splitter 32 CPU 33 Judgment Section 34 Infrared 35 Fluorescent 36 Reflected Light 40 Electromagnetic Solenoid X Magnetic Disk Running Direction

Claims (20)

[Claims] 1. A magnetic recording medium having a base made of a non-magnetic material and a magnetic layer formed above the base, wherein the magnetic layer and a servo layer for magnetic head tracking are formed of a layer containing a phosphor. And a data track formed on the magnetic layer and a servo track formed on the magnetic head tracking servo layer have a correspondence relationship with each other. A magnetic recording medium, characterized in that tracking of a magnetic head is performed based on fluorescence emitted from a phosphor in a tracking servo layer. 2. The magnetic head tracking servo layer according to claim 1, wherein the magnetic head tracking servo layer is formed between the base and the magnetic layer, and the magnetic layer transmits light that excites the phosphor and fluorescence from the phosphor. A magnetic recording medium having the property of: 3. The magnetic recording medium according to claim 2, wherein the thickness of the magnetic layer is regulated to less than 1 μm to allow light that excites the phosphor and fluorescence from the phosphor to pass therethrough. . 4. The magnetic recording medium according to claim 1, wherein the substrate has a reflectance of 1% or more with respect to light that excites the phosphor. 5. The magnetic recording medium according to claim 1, wherein the phosphor layer has a thickness of 0.5 μm or more. 6. The magnetic recording according to claim 1, wherein the center wavelength of fluorescence emitted from the phosphor is different from the center wavelength of light exciting the phosphor. Medium. 7. The magnetic recording medium according to claim 6, wherein the phosphor is an inorganic compound to which neodymium is added as an activator element. 8. The phosphor according to claim 7, wherein the phosphor is N.
dP ₅ O ₁₄ , LiNdP ₄ O ₁₂ and Al ₃ Nd (B
A magnetic recording medium, which is an inorganic compound selected from the group of O ₃ ) ₄ . 9. The magnetic head tracking servo layer according to claim 1, wherein the magnetic head tracking servo layer is formed uniformly on the phosphor layer and between the phosphor layer and the magnetic layer. A magnetic recording medium comprising a light transmitting / blocking layer. 10. The magnetic recording medium according to claim 9, wherein the substrate has a property of reflecting light for exciting the phosphor and fluorescence from the phosphor. 11. The magnetic recording medium according to claim 9, wherein the substrate has a property of transmitting fluorescence from the phosphor. 12. The fluorescent layer according to claim 1, wherein the magnetic head tracking servo layer is a patterned reflective layer on a substrate, and the reflective layer is uniformly formed on the reflective layer. A magnetic recording medium comprising a layer and a magnetic recording medium. 13. A magnetic recording medium according to claim 1, wherein the servo layer for magnetic head tracking is composed of a phosphor layer patterned on a substrate. 14. The binder layer according to claim 13, wherein a binder layer having a property of transmitting light exciting the phosphor is formed between the patterned phosphor layer and the magnetic layer, and the surface of the binder layer is A magnetic recording medium having a flat surface. 15. The servo layer for magnetic head tracking according to claim 1, wherein:
A magnetic recording medium having a light emitting portion made of a phosphor, the light emitting portion being formed along a relative movement direction of the magnetic recording medium and the light emitting element-light receiving element group. 16. The magnetic recording medium according to claim 15, wherein the light emitting portion is formed continuously along the relative movement direction of the magnetic recording medium and the light emitting element-light receiving element group. 17. The magnetic recording medium according to claim 15, wherein a light emitting portion that emits light with the phosphor and a non-light emitting portion that does not emit light with the phosphor are provided along a direction orthogonal to the relative movement direction of the light emitting element-light receiving element group. Areas of one light emitting portion (A
The ratio (A1: A) of the area (A2) of 1) and one non-light emitting portion
2) The magnetic recording medium is characterized in that it is regulated in the range of 1: 0.5 to 1.5. 18. A magnetic layer and a magnetic head tracking servo layer composed of a layer containing a phosphor are provided in an overlapping state in the thickness direction of a magnetic recording medium, and a data track formed on the magnetic layer. A light emitting element for irradiating the magnetic head tracking servo layer of a magnetic recording medium having a corresponding relationship with a servo track formed on the magnetic head tracking servo layer with light for exciting a phosphor, and the magnetic head tracking servo. A light receiving element group consisting of a plurality of light receiving elements for receiving the fluorescence emitted from the layer, and is arranged on the optical path from the magnetic recording medium and in front of the light receiving element group, and blocks the reflected light from the surface of the magnetic recording medium. A filter that transmits only fluorescence emitted from the magnetic head tracking servo layer, and a signal from the light receiving element group is input, A magnetic recording medium comprising: a servo signal calculating means for calculating and outputting a servo signal; and a magnetic head servo control section for correcting the position of the magnetic head based on the servo signal from the servo signal calculating means. Tracking servo controller. 19. A light emitting element for irradiating the surface of a magnetic recording medium with light, an optical path branching unit arranged on an optical path from the magnetic recording medium, for branching into a first optical path and a second optical path, A filter which is disposed on the optical path of 1, blocks the reflected light from the surface of the magnetic recording medium, and transmits only the fluorescence emitted from the magnetic head tracking servo layer provided on the magnetic recording medium, and the filter which transmits the fluorescence. A first light receiving element group including a plurality of light receiving elements for receiving the reflected light, and a second light receiving element including a plurality of light receiving elements arranged on the second optical path for receiving reflected light from the surface of the magnetic recording medium. Signals from the element group, the first light receiving element group and the second light receiving element group can be input, and signal determining means for selecting one of the signals from both light receiving element groups as an effective signal, and the signal Judgment means The servo signal calculating means for calculating and outputting a servo signal based on one of the signals from the first light receiving element group and the second light receiving element group, and the servo signal calculating means from the servo signal calculating means. A magnetic head servo control unit for correcting the position of the magnetic head based on a servo signal, and when both signals from the first light receiving element group and the second light receiving element group are input to the signal judging means, use It is determined that the present magnetic recording medium is a magnetic recording medium having a magnetic head tracking servo layer containing a phosphor, and the signal from the first light receiving element group is selected as valid, and the second light receiving medium is selected. When only the signals from the element group are input to the signal determining means, it is determined that the magnetic recording medium used is a magnetic recording medium having a magnetic head tracking recess formed on the surface of the magnetic layer. To the tracking servo control device for a magnetic recording medium characterized by being configured to select as an enable signal from the second light receiving element group. 20. A light emitting element for irradiating the surface of a magnetic recording medium with light, the light emitting element being arranged on an optical path from the magnetic recording medium, and blocking the reflected light from the surface of the magnetic recording medium, the light emitting element being provided on the magnetic recording medium. A filter that transmits only the fluorescence emitted from the magnetic head tracking servo layer, a light receiving element group including a plurality of light receiving elements that receives the light that has passed through the filter, and the filter is arranged on the optical path, Filter moving means for removing from the optical path, signal judging means for judging the presence or absence of the filter transmitted light, servo signal calculating means for calculating and outputting a servo signal based on a signal from the light receiving element group, and its servo A magnetic head servo control unit that corrects the position of the magnetic head based on the servo signal from the signal calculation unit, and the signal determination unit transmits the filter. Upon detecting the presence of, it is determined that the magnetic recording medium using is a magnetic recording medium having a servo layer for magnetic head tracking comprising phosphor, to place the filter directly into the optical path,
When the signal determining means detects the absence of light transmitted through the filter, it is determined that the magnetic recording medium used is a magnetic recording medium having a magnetic head tracking recess formed on the surface of the magnetic layer, and the filter is set to A tracking servo control device for a magnetic recording medium, characterized in that the filter moving means is driven so as to be removed from the optical path.