JPH09204689A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record/reproduce informations on/from the recording layers of a double-sided recording medium without a trouble by a method wherein first and second recording layers and first and second light transmitting layers are provided and the respective thicknesses of both the first and second light transmitting layers are within respective specific ranges. SOLUTION: A double-sided magneto-optical recording medium 10 is composed of a common substrate 11 and recording parts 16, photocuring resin layers 17 and transparent protective plates 18 which are provided on both the surfaces of the common substrate 11. Both the transparent protective plate 18 and the photocuring resin layer 17 are light transmitting and the summation of their thicknesses can be not larger than 0.6mm. In each recording part 16, a reflective layer 15 is so built up as to be closer to the substrate 11 than a recording magnetic layer 12. That is, the reflective layer 15, a second dielectric layer 14, the recording magnetic layer 12 and a first dielectric layer 13 are built up in layers in this order from the substrate 11 side. As the double-sided magneto-optical recording medium 10 has the common substrate 11, its thickness can be suppressed to approximate a half of the thickness of a conventional double-sided magneto-optical recording medium.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a numerical aperture of 0.55.
The present invention relates to an optical recording medium having an objective lens of 0.70 or less and used in an apparatus for recording and / or reproducing information.

[0002]

2. Description of the Related Art FIG. 5 shows a magneto-optical disk system, which is a kind of apparatus for recording and / or reproducing information using an optical recording medium, and an optical recording medium used in this magneto-optical disk system. A conventional example of a kind of disc-shaped magneto-optical recording medium is shown.

In the magneto-optical disk system shown in FIG. 5, when a disk-shaped one-sided magneto-optical recording medium 50 is mounted, an optical system including a laser device 58, an objective lens 59, etc. is provided on the upper surface side of the one-sided magneto-optical recording medium 50. The magnetic field generator 60, which is a magnetic system, is located on the lower surface side of the single-sided magneto-optical recording medium 50. The numerical aperture (hereinafter referred to as “NA”) of the objective lens 59 is set to 0.50 to 0.53.

A drive system (not shown) is provided for driving the optical system with respect to the magneto-optical recording medium 50 in the focus direction and the tracking direction. The magnetic system is also provided with another drive system (not shown) for driving in the arrow direction and the tracking direction in FIG.

In this magneto-optical disk system, a magnetic field modulation system is used for recording. In this magnetic field modulation method, since it is necessary to control the reversal of the magnetic field at a high speed, a sufficient exciting current cannot be obtained, and the generated magnetic field strength is limited. Therefore, the magnetic field generator 60 is arranged in the single-sided magneto-optical recording medium 50. It is arranged near a recording magnetic layer 53 described later. Overwriting is possible in the magnetic field modulation method.

The single-sided magneto-optical recording medium 50 is a recording medium having a large magneto-optical effect such as a dielectric layer 52 and a rare earth-transition metal alloy amorphous thin film on one side surface of a transparent substrate 51 such as polycarbonate. The magnetic layer 53, the dielectric layer 54, the reflective layer 55, and the protective cover 56 are sequentially laminated and configured. The thickness t ₁ of the transparent substrate 51 is constant and conventionally set to 1.2 mm.

Next, the operation will be briefly described. First, the single-sided magneto-optical recording medium 50 is placed on a rotating disk (not shown) and driven to rotate, and a magnetic field from the magnetic field generator 60 is applied to the recording magnetic layer 53. This magnetic field is subjected to high-speed reversal control, and the recording magnetic layer 53 to which this magnetic field is applied,
By focusing the laser beam emitted from the laser device 58 through the objective lens 59, the recording magnetic layer 53 in the region where the laser beam is focused can be magnetized, and the information signal is overwritten in real time. be able to.

[0008]

By the way, in order to simplify and miniaturize the above-mentioned optical system, magnetic system, and magneto-optical pickup equipped with these drive systems, the optical system and the magnetic system are integrally formed on one side. It is conceivable to arrange them on the same surface side of the magneto-optical recording medium 50. That is, a configuration in which the magnetic field generator 60 is arranged on the objective lens 59 side (transparent substrate 51 side) and these are integrated may be considered. However, in this configuration,
Due to the thick transparent substrate 51 of 1.2 mm, the distance from the magnetic field generator 60 to the recording magnetic layer 53 becomes long, and it becomes impossible to apply a magnetic field of sufficient strength to the recording magnetic layer 53.

On the other hand, with the increase in the amount of information in recent years, there is provided a double-sided magneto-optical recording medium which is provided with the above-mentioned recording magnetic layers on both sides of one magneto-optical recording medium and can record information on both sides. Has been developed. However, in order to record and reproduce information on such a double-sided magneto-optical recording medium, for example, a magneto-optical pickup having an optical system and a magnetic system shown in FIG. Applying a strong magnetic field is extremely difficult.

In a magnetic field modulation type magnetic field generator, it is necessary to flow a high frequency current corresponding to a high frequency data signal through an electromagnetic coil. However, the higher the frequency of the current, the more difficult it is for the current to flow through the coil and the generated magnetic field. In addition to its limited strength, the distance from the magnetic field generator to the recording magnetic layer is considerably long due to the thick transparent substrate. Therefore, in the magneto-optical disk system using the conventional magneto-optical recording medium, double-sided magneto-optical recording by the magnetic field modulation method has been extremely difficult.

Further, in order to increase the recording density of the single-sided magneto-optical recording medium 50, it is necessary to reduce the minimum diameter of the laser beam focused by the objective lens 59, and as one means therefor, the aperture of the objective lens 59 is required. It is possible to increase the number. However, if the numerical aperture of the objective lens 59 is increased, the objective lens 59 becomes thick and the objective lens 59 and the one-sided magneto-optical recording medium 50 come into contact with each other.

Therefore, according to the present invention, although the information recording layers are provided on both sides, recording and reproduction can be performed on these two recording layers without any trouble, and high density recording and It is an object of the present invention to provide an optical recording medium which can be reproduced and which can have a large capacity.

[0013]

The optical disk system according to the present invention has an objective lens having a numerical aperture of 0.55 to 0.70 and is used in an apparatus for recording and / or reproducing information. A first recording layer, which is a recording medium, in which a laser beam is focused through the objective lens, and a first light transmitting layer which is formed on the first recording layer and which transmits the laser beam. A second recording layer facing the first recording layer via an intermediate layer and focused by the laser beam via the objective lens; and a second recording layer formed on the second recording layer. A second light transmission layer through which a laser beam is transmitted.
Both of the light-transmitting layers have a thickness of 0.1 to 0.6 mm.

In the optical recording medium according to the present invention, the thicknesses of the first and second light transmitting layers respectively formed on the first and second recording layers are as thin as 0.1 to 0.6 mm. Pickups including an objective lens and the like are collectively arranged on the first and second light transmission layer sides, and the first and second light transmission layers are respectively provided between the pickup and the first and second recording layers. However, since the distance between the pickup and the first and second recording layers is short, recording and reproduction can be performed on the recording layers on both sides without any trouble.

Moreover, the numerical aperture of the objective lens is 0.55 to 0.55.
Even if the objective lens is as large as 0.70 and is thick, the objective lens and the optical recording medium do not come into contact with each other because the thicknesses of both the first and second light transmitting layers are as thin as 0.1 to 0.6 mm. With the objective lens having a large numerical aperture, high-density recording and reproduction can be performed.

The minimum diameter (2ω ₀ ) of the laser beam focused by the objective lens is expressed by the following equation. 2ω ₀ = 0.82 × λ / NA (λ: wavelength of laser beam)

The NA of the objective lens in the apparatus using the optical recording medium according to the present invention is the NA of the objective lens in the apparatus using the conventional optical recording medium (0.
50-0.53). Therefore, as is apparent from the above formula, in the device using the optical recording medium according to the present invention, the minimum diameter of the focused laser beam is smaller and the recording density is higher, and the recording density is increased. Playback can be performed.

Although the thickness of the objective lens increases as the NA increases, the thickness of the first and second light transmitting layers of the optical recording medium is the same as the thickness (1) of the light transmitting layer in the conventional optical recording medium. Since it is thinner than 0.2 mm, the thickened objective lens does not come into contact with the optical recording medium.

When the NA of the objective lens and the thickness t of the light transmitting layer of the optical recording medium change, the aberration value of the objective lens changes as follows. (A) Spherical aberration W ₄₀ (Sin α = NA) (N: Refractive index of light transmitting layer of optical recording medium)

(B) Coma aberration W ₃₁ (Θ: skew)

Since the spherical aberration W ₄₀ can be corrected by the objective lens, there is basically no problem. However, there is a problem if the thickness t of the light transmitting layer varies, so it is desirable to suppress this thickness t within the tolerance. On the other hand, since the coma aberration W ₃₁ cannot be corrected by the objective lens, the smaller the absolute value is, the more preferable. Even if the NA of the objective lens is large, in the optical recording medium according to the present invention, the absolute value of the coma aberration W ₃₁ does not become large because the thickness t of the first and second light transmitting layers is thin. Therefore, even if the NA of the objective lens is large, the aberration hardly poses a problem, and recording and reproduction can be performed with a higher density than before.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Reference examples of the present invention and first
And 2nd Embodiment is described, referring FIGS. FIG. 1 is a cross-sectional view showing a magneto-optical recording medium as a reference example of the present invention and a magneto-optical disk system using this magneto-optical recording medium, showing a basic configuration of the magneto-optical disk system. ing. As shown in FIG. 1, this magneto-optical disk system is composed of an objective lens 2 having an NA of 0.55 to 0.70, and an optical glass 8 having a coil pattern 7 and having a light transmitting property. The magnetic field generator 9 is installed.

The disk-shaped single-sided magneto-optical recording medium 40 is
Thin translucent substrate 41 having a thickness t ₂ of 0.1 to 0.6 mm
Further, the dielectric layer 42, the recording magnetic layer 43, the dielectric layer 44, the reflective film 45, and the protective cover 46 are sequentially laminated. The single-sided magneto-optical recording medium 40 is irradiated with a laser beam from a laser beam device (not shown) for recording and reproduction.

The magnetic field generator 9 is of a magnetic field modulation type, which will be described later in detail with reference to FIG. Dielectric layer 42
Is much thinner than the thickness t ₂ of the translucent substrate 41, the dielectric layer 4 has a thickness corresponding to the thickness t ₂ of the translucent substrate 41.
It is not necessary to consider the thickness of 2. The objective lens 2 which is an optical system and the optical glass 8 which is a magnetic system are bonded so as to be integrated, and the coil pattern 7 is arranged close to the magneto-optical recording medium 40.

As described above, since the thickness t ₂ of the transparent substrate 41 is considerably smaller than that of the conventional one and the coil pattern 7 is close to the transparent substrate 41, the coil pattern 7 and the recording magnetic layer 43 are Is preferable because the distance is short. Further, since the optical system and the magnetic system are integrated, the magneto-optical pickup including them can be miniaturized and the cost can be reduced, and as described in the first and second embodiments described later. In addition, recording and reproduction on the double-sided magneto-optical recording medium become possible.

As the magneto-optical recording medium used in this magneto-optical disk system, it is preferable to use, for example, a 3.5-inch magneto-optical disk fixedly or housed in a cartridge holder.

The NA of the objective lens 2 is 0.55 to 0.70.
Therefore, the depth of focus (= λ / NA ² , λ: wavelength of laser beam) is shallow. However, since the magneto-optical disk is small as described above, the actuator (not shown) that constitutes the drive system for the magneto-optical pickup is downsized, and its frequency characteristic is improved so that this actuator can move the magneto-optical disk. Since it sufficiently follows, there is no problem that the focal depth of the objective lens 2 is shallow.

The spherical aberration W ₄₀ is corrected by the objective lens 2. The coma aberration W _{31 is} also caused by the objective lens 2 as described above.
Has a large NA, there is no problem because the thickness t ₂ of the transparent substrate 41 is small. Table 1 below, coma W ₃₁ is equivalent to the coma aberration W ₃₁ in the case of the thickness t = 1.2 mm of NA = 0.50 and the light-transparent substrate of a conventional such objective lens (light transmission layer) NA and thickness t are shown for four cases.

[0029]

[Table 1]

As shown in Table 1 above, even if the NA is 0.55 to 0.70, the thickness t of the light transmissive substrate (light transmissive layer) should be 0.6 to 0.1 mm. For example, it can be understood that the coma aberration can be set to the same as or smaller than that in the conventional case and there is no problem. Further, since the objective lens 2 has a large NA, the objective lens 2 is thick, but as described above, the thickness t of the translucent base 41 is t.
_{Since 2} is thin, the distance d (working distance) between the objective lens 2 and the magneto-optical recording medium 40 is not less than a predetermined value as shown in FIG. Do not touch.

Further, since the magneto-optical recording medium adopts the cartridge holder type or the fixed type, the dust which is a problem in the magneto-optical disk system has no problem in this case. Regarding the above-mentioned dust, the particle size and distribution thereof become a problem, but the laser beam is transmitted by the transparent substrate 4.
The radius r of the circle projected on 1 (see FIG. 1) is r = t · tan (arc sin (NA / N)). Then, as can be seen from this equation, when the thickness t of the light transmission layer becomes smaller, the radius r also becomes smaller, but the NA is large and the radius r does not become significantly small. Not particularly.

As described above, in the magneto-optical disk system in which the magneto-optical recording medium of this reference example is used, the NA of the objective lens 2 is set to 0.55 to 0.70 and the light-transmitting substrate (optical The thickness t ₂ of the transmission layer) 41 is 0.6 to 0.1.
mm. Therefore, as compared with the conventional system using the objective lens having the NA of 0.50, the recording density is (0.55 / 0.50) ² to
It is possible to increase (0.70 / 0.50) ² ≈1.2 to ² times, and it is understood that all of the above various problems caused by increasing the NA can be solved. Therefore, it is possible to increase the capacity of the magneto-optical disk system without any problem.

Next, a magneto-optical recording medium as the optical recording medium of the first and second embodiments and a magneto-optical disk system using the first and second embodiments will be described. FIG. 2 is a cross-sectional view of the magneto-optical recording medium of the first embodiment and a magneto-optical disk system using this magneto-optical recording medium.

In a magneto-optical disk system using the magneto-optical recording medium of the first embodiment, first and second magneto-optical pickup devices having an optical system and a magnetic system are shown in FIG. Thus, they are arranged so as to face each other with the first double-sided magneto-optical recording medium 10 interposed therebetween. The first magneto-optical pickup device arranged on the upper surface side of the double-sided magneto-optical recording medium 10 and the second magneto-optical pickup device arranged on the lower surface side have the same configuration as described below. The constituent parts 1 to 9 and 1'to 9'correspond to each other.

The first and second magneto-optical pickup devices are composed of pickups 6 and 6'which are optical systems and the above-mentioned magnetic field generators 9 and 9'which are magnetic systems. In addition, the pickups 6 and 6'include the laser devices 1 and 1 ',
As described above, the objective lenses 2 and 2'having NA of 0.55 to 0.70, the coil bobbins 4 and 4'on which the focus coils 3a and 3a 'and the tracking coils 3b and 3b' are wound, It consists of magnets 5, 5'disposed around the coil bobbins 4, 4 '.

The coil bobbins 4 and 4'are cylindrical, for example, and the focus coils 3a and 3a 'for driving the pickups 6 and 6'in the F direction in FIG. 2 and the pickups 6 and 6'in FIG. Winding tracking coils 3b and 3b 'for driving in the T direction are provided around the coil bobbins 4 and 4'. Coil bobbin 4,
Lens support members 2a and 2a 'are provided at positions near the end portions 4a and 4a' of 4 ', and the objective lenses 2 and 2'for focusing the laser beams emitted from the laser devices 1 and 1'. Are supported by the lens support members 2a and 2a '.

As shown in FIG. 3, the magnetic field generators 9 and 9'apply a high-frequency signal current to the surfaces 8a and 8a 'of the optical glasses 8 and 8'having optical transparency such as quartz. The conductors 7a and 7a 'for flowing to generate a magnetic field are formed as spiral coil patterns 7 and 7'.

On the back surfaces 8b and 8b 'of the optical glasses 8 and 8'on which the coil patterns 7 and 7'are not formed, the centers of the coil patterns 7 and 7'are aligned with the centers of the objective lenses 2 and 2'. Aligned, coil bobbins 4, 4
The end portions 4a, 4a 'of ′ are adhesively fixed. For this reason, the laser beam can be focused on the center of the generated magnetic field, and adjustment of centering is unnecessary when assembling the pickup.

The use of quartz as the optical glass 8 and 8'is an example, and any material that is transparent to light may be used, and as the coil patterns 7 and 7 ', a print coil, a thin film coil or the like may be used. Can be used. Moreover, in order to prevent reflection of the laser beam, holes through which the laser beam passes may be provided in the optical glasses 8 and 8 '.

On the other hand, the double-sided magneto-optical recording medium 10 shown in FIG.
The recording unit 16, the photo-curable resin layer 17, and the transparent protective plate 18 are provided on both surfaces of the common substrate 11, respectively. Both the transparent protective plate 18 and the photocurable resin layer 17 have a light-transmitting property, and the sum of their thickness can be 0.6 mm or less.

In each recording section 16, the reflection layer 15 is provided.
Are laminated so as to be arranged closer to the substrate 11 than the recording magnetic layer 12, and the reflective layer 15, the second dielectric layer 14, the recording magnetic layer 12 and the first dielectric layer 13 are arranged from the substrate 11 side, respectively. Are laminated in this order. In this double-sided magneto-optical recording medium 10, since the substrate 11 is common, it is possible to reduce the thickness to about half as compared with the conventional double-sided magneto-optical recording medium by bonding the substrates.

Next, the operation will be described. In the first magneto-optical pickup device, the focus driving current is supplied to the focus coil 3a, whereby the coil bobbin 4 and the magnetic field generator 9 provided in the coil bobbin 4 are indicated by an arrow F in FIG. The objective lens 2
Is driven and displaced in the focus direction, which is the optical axis direction of. Further, by supplying the tracking drive current to the tracking coil 3b, the coil bobbin 4 and the magnetic field generator 9 are indicated by an arrow T in FIG.
Is driven and displaced in the tracking direction, which is the direction orthogonal to the optical axis of.

Also in the second magneto-optical pickup device, the coil bobbin 4'and the magnetic field generating device 9'in the same manner as the first magneto-optical pickup device and in synchronization with the drive displacement in the first magneto-optical pickup device. Is driven and displaced in the F and T directions.

Simultaneously with the above-mentioned drive displacement in the first and second magneto-optical pickup devices, a high frequency current signal obtained by amplifying a signal to be recorded is coil patterns 7, 7 '.
A magnetic field is generated by being supplied to. This magnetic field is subjected to high-speed inversion control according to the recording signal and is applied to the recording magnetic layers 12, 12. And the recording magnetic layer 1
The objective lens 2, the laser beam emitted from the laser device 1, 1 ′ is applied to the area of the magnetic field 2, 2 of which the magnetic field is applied.
Information is recorded by focusing the laser beam through the 2'and the optical glass 8 and 8'and raising the temperature of the region of the recording magnetic layers 12 and 12 on which the laser beam is focused to the Curie point or higher.

As is apparent from the above description, in the magneto-optical disk system using the magneto-optical recording medium of the first embodiment, the laser devices 1, 1'and the objective lens 2,
An optical system which is a pickup 6 and 6'comprising 2'and the like,
Since the magnetic system, which is the magnetic field generating device 9 or 9 ′ formed by forming the coil patterns 7 and 7 ′ on the optical glass 8 or 8 ′, is provided on the same surface side of the double-sided magneto-optical recording medium 10,
The distance between the coil patterns 7 and 7'and the double-sided magneto-optical recording medium 10 is short.

Further, the transparent protective plate 18 and the photocurable resin layer 17
Since the light-transmitting layer composed of is thin, the distance between the coil patterns 7 and 7'and the recording magnetic layers 12 and 12 is extremely short, and thus the double-sided light by the magneto-optical modulation method, which has been considered to be extremely difficult until now. Recording and reproduction on a magnetic recording medium are possible.

Further, since the coil bobbins 4 and 4'and the magnetic field generators 9 and 9'are fixed by adhesion, the centers of the objective lenses 2 and 2'and the centers of the magnetic fields from the magnetic field generators 9 and 9'are set. Can be easily aligned. Further, since the pickups 6 and 6 ′ and the magnetic field generators 9 and 9 ′ are interlocked by the focus servo, the double-sided magneto-optical recording medium 10
The strength of the magnetic field applied to the can always be constant.
Further, the drive system for the magnetic system, which has been required until now, is omitted. Since the magneto-optical pickup device is provided with a large space, the degree of freedom in design is increased.

In the magneto-optical disk system using the magneto-optical recording medium of the first embodiment described above, various methods of recording and reproducing can be performed on the double-sided magneto-optical recording medium 10. For example, by simultaneously using the laser devices 1 and 1'and the magnetic field generators 9 and 9 ', simultaneous recording on the upper surface side and the lower surface side of the double-sided magneto-optical recording medium 10 is possible, and the laser devices 1, 1 Simultaneous reproduction is possible by using ‘simultaneously. As a result, the capacity can be further increased, and information can be recorded and reproduced at higher speed.

Further, it is possible to record or reproduce on one side of the double-sided magneto-optical recording medium 10 first, and then record or reproduce on the other side.
Recording and reproducing can be performed with a capacity twice as large as that of a single-sided magneto-optical recording medium. In this case, both magnetic field generators 9 and 9'can be used simultaneously when recording on one surface. Therefore, magnetic fields can be applied to the recording magnetic layer 12 from both sides thereof, and recording can be performed with a larger magnetic field. In addition, when recording on one surface, it is possible to perform recording by using only the magnetic field generator arranged on the other surface side.

Next, the magneto-optical recording medium of the second embodiment and the magneto-optical disk system using this magneto-optical recording medium will be described. As shown in FIG. 4, a magneto-optical disk system using the magneto-optical recording medium of the second embodiment is a magneto-optical disk using the magneto-optical recording medium of the first embodiment shown in FIG. A magneto-optical disk system similar to the system is used, and recording and reproduction can be performed by using the second double-sided magneto-optical recording medium 30 shown in FIG.

The double-sided magneto-optical recording medium 30 has a common substrate 3
The high magnetic permeability layer 32, the photocurable resin layer 33, and
The magneto-optical recording layer 34, the adhesive layer 35, and the transparent protective plate 36 are sequentially laminated. Both the transparent protective plate 36 and the adhesive layer 35 have translucency, and the sum of their thicknesses can be 0.6 mm or less.

The high magnetic permeability layer 32 is made of, for example, Fe, Co,
The double-sided magneto-optical recording medium 30 can be improved in vertical magnetic field efficiency by being made of a material having a high magnetic permeability such as a transition metal such as Ni and an alloy thereof such as permalloy, sendust, or an amorphous magnetic alloy.

In the magneto-optical disk system using the magneto-optical recording medium of the second embodiment, since the double-sided magneto-optical recording medium 30 has the high magnetic permeability layer 32, the magnetic field generators 9 and 9 ' 4 forms a magnetic closed loop as shown by the broken line in FIG. 4, for example, the magnetic flux applied to the double-sided magneto-optical recording medium 30 at the time of recording can be effectively focused and its perpendicular magnetic field efficiency can be increased. Is preferable.

Even in the magneto-optical disk system using the magneto-optical recording medium of the second embodiment, it is possible to record or reproduce on both sides of the double-sided magneto-optical recording medium 30 at the same time. It is also possible to record or reproduce on the other surface after recording or reproducing on the surface.

As described above, the magneto-optical disk system using the magneto-optical recording medium of the first and second embodiments is similar to the magneto-optical disk system using the magneto-optical recording medium of the reference example. Since the objective lenses 2 and 2'has a larger NA, higher-density recording and reproduction are possible, and a double-sided magneto-optical recording medium can be used.
Higher capacity and faster recording and reproduction are possible. Therefore, it is possible to provide a magneto-optical disk system having a large capacity.

In the magneto-optical disk system using the magneto-optical recording medium of the first and second embodiments, the magnetic field generators 9 and 9'are of the magnetic field modulation type, but other types such as the optical modulation type are used. The present invention can be applied to a system. Further, although the first and second embodiments are used in the magneto-optical disk system, the present invention is not limited to this, and for example, an optical recording medium configured by providing pits in the recording layer (additional write). Type optical recording medium etc.) may be used.

[0057]

According to the optical recording medium of the present invention, although information recording layers are provided on both sides, recording and reproduction can be performed on these two recording layers without any trouble, and the opening Since high-density recording and reproduction can be performed with a large number of objective lenses, a large capacity can be achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a reference example of the present invention and a configuration of a magneto-optical disk system using the reference example.

FIG. 2 is a sectional view showing the first embodiment of the present invention and the configuration of a magneto-optical disk system in which the first embodiment is used.

FIG. 3 is a front view of an optical glass having a coil pattern that can be used in the magneto-optical disk system shown in FIGS. 1, 2 and 4.

FIG. 4 is a cross-sectional view showing a second embodiment of the present invention and a configuration of a magneto-optical disk system using the second embodiment.

FIG. 5 is a sectional view showing a conventional example of the present invention and a configuration of a magneto-optical disk system using the conventional example.

[Explanation of symbols]

2, 2'Objective lens 10, 30, 40 Magneto-optical recording medium (optical recording medium) 16 Recording part (recording layer) 17, 18 Photo-curable resin layer and transparent protective plate (light-transmitting layer) 34 Magneto-optical recording layer (recording Layer) 35, 36 Adhesive layer and transparent protective plate (light transmitting layer) 41 Light transmitting substrate (light transmitting layer) 43 Recording magnetic layer (recording layer) t ₁ , t ₂ Thickness of light transmitting layer

Claims (1)

[Claims] 1. An optical recording medium having an objective lens having a numerical aperture of 0.55 to 0.70, which is used in an apparatus for recording and / or reproducing information, wherein the objective lens is used. First laser beam is focused
Recording layer, a first light transmission layer formed on the first recording layer and transmitting the laser beam, and an objective lens facing the first recording layer via an intermediate layer. A second recording layer on which the laser beam is focused through the second recording layer; and a second light transmission layer formed on the second recording layer and transmitting the laser beam. And the thickness of the second light transmitting layer is 0.1 to 0.
An optical recording medium having a length of 6 mm.