JP2000315335A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical recording medium capable of forming a temperature distribution of optimum shape in a recording layer by diffusing heat generated in the recording layer by light irradiation in a film thickness direction. SOLUTION: An optical magnetic recording medium 10 is provided on a transparent substrate 1 with a reproducing layer 2, a heat conductive layer 3, a recording layer 4, dielectric layer 5 and a reflection layer 6. The heat conductive layer 3 is constituted of non magnetic metal material having >=20 Wm-1K-1 heat conductivity such as Cu. Cu can transmit light having <=560 nm wave length. Therefore, even when the heat conductive layer 3 is disposed in a light incident side of the recording layer 4, information can be recorded and reproduced with the light having <=560 nm wave length. Heat of the recording layer generated by light irradiation is diffused in a film thickness direction at a light incident side of the recording layer 4 by the heat conductive layer 3 having a high heat conductivity. As a result, a temperature distribution of desired shape can be formed in the recording layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a recording layer on a substrate, and more particularly to an optical recording medium capable of reducing heat generated by light irradiation.

[0002]

2. Description of the Related Art Optical recording media are widely used as information recording media on which digital data such as moving image data and audio data can be recorded or reproduced. In recent years, higher image quality and higher sound quality of moving image and audio data have progressed, and their data amount has increased. Therefore, in optical recording media, in order to sufficiently cope with such an increase in the amount of data,
There is a demand for a further increase in capacity.

In order to meet this demand, a method of forming a fine recording mark to improve the recording density and reading out the fine recording mark with a small light spot diameter has been studied. The light spot diameter is proportional to the wavelength of light and inversely proportional to the numerical aperture of the lens that collects the light. Therefore, in order to reduce the diameter of the light spot, it is only necessary to shorten the wavelength of the laser beam used for recording and reproduction or to increase the numerical aperture of the objective lens. Currently, DVD (Digital Versatile Disc)
Uses an orange laser light having a wavelength of 650 nm, which is a shorter wavelength than a red laser light having a wavelength of 780 nm for reproducing a CD, and realizes miniaturization of a light spot.

[0004]

By the way, in an optical recording medium having a recording layer on which information is recorded, the recording layer is heated by irradiating the recording layer with a laser beam condensed by a lens. The information is recorded by changing the magnetic properties and the crystallization state. However, the following problems become apparent due to heat generated by light irradiation. That is, in the conventional magneto-optical recording medium 40 as shown in FIG. 4, the second dielectric layer 44 and the reflection layer 45 are provided on the recording layer 43 for the purpose of increasing the apparent Kerr rotation angle, and the recording is performed. A first dielectric layer 42 is provided below the recording layer 43 to prevent corrosion of the layer 43. When such a magneto-optical recording medium 40 is irradiated with a laser beam, the laser beam has a Gaussian light intensity distribution, so that the recording layer 43 is heated at a temperature distribution based on the Gaussian distribution, and the recording layer 43 is irradiated with the laser beam. The heat reaches the reflective layer 45 through the second dielectric layer 44 on the recording layer 43 and is diffused in the reflective layer 45. That is, the reflection layer 45 plays a role of heat radiation, and the heat distribution of the recording layer 46 can be controlled by rapidly cooling the recording layer 46.

However, since the second dielectric layer 44 has a lower thermal conductivity than a metal such as the reflective layer 45, the heat of the recording layer 43 generated by light irradiation is hardly transmitted to the reflective layer 45. Further, the recording layer 43 includes the first and second dielectric layers 42, 4
4, heat is accumulated more than necessary in the recording layer 43, and the accumulated heat diffuses in the recording layer 43 toward the film surface. Therefore, the temperature distribution of the recording layer 43 has a gentler temperature gradient in the radial direction of the light spot than the Gaussian light intensity distribution. For this reason, when the interval between the recording marks is reduced due to the high density, the heat generated when an arbitrary recording mark is recorded affects the formation of the recording mark located next to the recording mark, and the desired shape of the recording mark is obtained. There is a possibility that a recording mark cannot be formed on the recording layer 43. The speed of diffusion of heat of the recording layer 43 to the reflective layer 45 caused by light irradiation can be increased by reducing the thickness of the second dielectric layer 44, but as described above, the second dielectric layer 45 Since the film thickness is controlled for the purpose of increasing the apparent Kerr rotation angle, the film thickness of the second dielectric layer 44 cannot be excessively reduced. In this case, it is necessary to replace the second dielectric layer 44 with a material having an appropriate refractive index. In some cases, the second dielectric layer 44 may be omitted.

The problem of heat is extremely serious in a magneto-optical recording medium 50 of the type shown in FIG. 5 in which recording and reproduction is performed by irradiating a laser beam 9 from the protective layer 57 side. That is, in the magneto-optical recording medium 50 having a laminated structure shown in FIG. 5, since the protective layer 57 is in contact with air, this air layer functions as a heat insulating layer, and the recording layer 53 generated by laser light irradiation. Is accumulated in the recording layer 53 without being dissipated. In the magneto-optical recording medium 40 in which light is incident from the substrate 41 side as shown in FIG. 4, the heat of the recording layer 43 can be diffused by the substrate 41 existing on the light incident side. In such a magneto-optical recording medium 50, since the air layer on the protective layer 57 acts as a heat insulating layer, heat is difficult to escape, and heat is accumulated in the recording layer 53 at a high temperature. Therefore, heat control of the recording layer 53 becomes difficult, and there is a possibility that a desired recording mark cannot be formed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide an optical recording medium capable of reducing heat accumulation in a recording layer caused by light irradiation. Is to do.

[0008]

According to a first aspect of the present invention, there is provided a first recording layer on a substrate, on which information is recorded, wherein at least one of recording and reproduction of information is performed by irradiating light. Optical recording medium provided with a nonmagnetic thermal conductive layer having a thermal conductivity of 20 Wm ^-1 K ^-1 or more on the light incident side of the first recording layer. You.

The optical recording medium of the present invention has a nonmagnetic heat conductive layer on the light incident side of the recording layer. The heat conductive layer has a heat conductivity of 20 Wm ^-1 K ^-1 or more, and therefore, generates heat in the recording layer by light irradiation in a direction perpendicular to the film surface of the recording layer on the light incident side of the recording layer. That is, it can be rapidly diffused in the direction of the film thickness. Since the value of the thermal conductivity is almost the same as the thermal conductivity of the material used for the recording layer of the current magneto-optical recording medium, heat is hardly accumulated in the recording layer. In a conventional optical recording medium, heat of the recording layer can be radiated only on the side of the recording layer opposite to the side on which light is incident. Also, as described in the prior art section,
In the case of a magneto-optical recording medium of the type in which light is incident from the substrate side, the heat of the recording layer can be sufficiently diffused because a dielectric layer with low thermal conductivity was present on the light incident side of the recording layer. Did not. On the other hand, the optical recording medium of the present invention includes a non-magnetic layer having high thermal conductivity on the light incident side, so that heat can be diffused also in the direction of the light incident side. Thereby, the heat of the recording layer generated by the light irradiation can be diffused extremely efficiently as compared with the related art, and a desired temperature distribution can be formed in the recording layer.

Further, since the heat conductive layer is non-magnetic, it is possible to record and reproduce information without magnetically affecting the recording layer even when a magnetic film is used for the recording layer, for example. it can.

Since the heat conducting layer of the optical recording medium of the present invention is formed on the light incident side of the recording layer, it preferably has a property of transmitting light used for recording or reproduction. For example, as shown in FIG. 3, Cu (copper) has a light reflection end near its wavelength of 560 nm, and transmits light having a wavelength of 560 nm or less and transmits light having a wavelength longer than 560 nm. reflect. Therefore, a heat conductive layer is formed using this Cu, and the light for recording / reproducing has a wavelength of 300 nm to 60 nm.
The use of laser light of 0 nm makes it possible to record and reproduce information. Further, since light having a short wavelength of 600 nm or less can be used, the diameter of the light spot can be reduced, and high-density recording can be realized.
Also, as shown in FIG. 3, Au (gold) is also suitable as a material for forming the heat conductive layer because of its low light reflectivity near the wavelength of 500 nm.
Since i and the like have a low light reflectance at a wavelength of 600 nm or less and easily transmit light, these materials are also suitable as materials constituting the heat conductive layer. It is known that the light reflection ends of Ag and CuNi are near 300 nm and 530 nm, respectively. In this specification, the term “light reflection end” indicates a portion where the reflectance sharply rises in the reflectance spectrum with respect to the wavelength of light.

The heat conduction layer preferably has an extinction coefficient at the wavelength of the irradiated light of 3.0 or less. As shown in FIG. 8, as the light extinction coefficient of the material constituting the heat conductive layer decreases, the obtained figure of merit (the value represented by the product of the reflectance and the Kerr rotation angle) increases. When the light extinction coefficient is 3.0 or less, preferably 1.5 or less, a sufficient figure of merit can be obtained. As a material satisfying such conditions, for example, Si is preferable. Although Si does not have a light reflection end within the range of 300 nm to 600 nm, it has a large thermal conductivity of 160 Wm ^-1 K ^-1 and a small extinction coefficient of light of about 0.2. It is suitable as a material constituting a layer.

In the optical recording medium of the present invention, the thickness of the heat conductive layer is preferably 1 nm to 200 nm. If the thickness is less than 1 nm, the effect of radiating heat generated by light irradiation is not sufficient. On the other hand, if the film thickness is larger than 200 nm, as shown in FIG. 9, there is a possibility that the figure of merit may be attenuated due to the presence of the light extinction coefficient of the heat conductive layer and the signal quality may be deteriorated. When the heat conductive layer is made of Si,
It is difficult to form single crystal Si in the process of forming a heat conductive layer, and the light extinction coefficient is larger than that of single crystal Si. Therefore, it is desirable that the thickness of the heat conductive layer made of Si be 40 nm or less.

The optical recording medium of the present invention can be applied to any optical recording medium such as a phase change optical recording medium, a magneto-optical recording medium, and a write-once optical recording medium. For example, if the optical recording medium of the present invention is applied to a magneto-optical recording medium, TbFeCo, DyFeCo, TbDyFeCo
A magnetic material such as a rare earth transition metal alloy may be used.
In this case, it is preferable to use a material having a large Kerr rotation angle with respect to light having a wavelength of 600 nm or less, for example, a rare earth transition metal alloy such as GdFeCo. If the optical recording medium of the present invention is applied to a phase-change type optical recording medium, the recording layer may be made of, for example,
An eSbTe-based, InSe-based, and AgInSbTe-based phase change material may be used.

In the optical recording medium of the present invention, the heat conductive layer provided on the light incident side of the recording layer may be provided in contact with the recording layer or may be provided with an optional layer interposed. For example, when the optical recording medium of the present invention is applied to a magneto-optical recording medium, a mask layer used in a magneto-optical recording medium for magnetic super-resolution (MSR) is provided between the recording layer and the heat conductive layer; The applicant is WO
98/02878 (Magn.
It is also possible to form a magnetic domain expansion reproducing layer used in a magneto-optical recording medium for etic amplification (Magneto-Optical System). Furthermore, it is also possible to provide a heat conductive layer on both sides of the recording layer. Thereby, the heat radiation effect can be further improved.

In the optical recording medium of the present invention, light for recording / reproducing may be incident from the substrate side or from the opposite side of the substrate. When light is incident from the substrate side, a heat conductive layer may be provided between the substrate and the recording layer, and when light is incident from the opposite side of the substrate, the recording layer is formed of the heat conductive layer and the substrate. What is necessary is just to form a heat conductive layer so that it may be pinched by.

In the optical recording medium of the present invention, a second recording layer (second recording layer) different from the recording layer (first recording layer) is further provided on the light incident side of the heat conductive layer. It is preferable to provide When the heat conduction layer is made of Cu, the wavelength is 560.
Since light having a wavelength of not more than 560 nm is transmitted and light having a wavelength longer than 560 nm is reflected, information recorded on the second recording layer and reproduction of the information have a wavelength longer than 560 nm reflected by the heat conductive layer. In order to record information on the first recording layer and to reproduce the information using the light of 560 nm,
If light having a wavelength of less than is used, information can be independently recorded in the first and second recording layers, and the recorded information can be reproduced independently. At this time, in order to prevent the information of the second recording layer from being read by light having a wavelength of less than 560 nm, the thickness of each layer can be adjusted to utilize the light interference effect.

According to a second aspect of the present invention, on a substrate:
In an optical recording medium including a first recording layer and a reproducing layer on which information is recorded, and at least one of recording and reproducing of information is performed by irradiating light, the thermal conductivity is 20 Wm ^-1 K.
^-1 or more thermally conductive layer of non-magnetic optical recording medium, characterized in that it comprises in contact with the reproducing layer.

In the optical recording medium according to the second aspect of the present invention, the heat conductive layer used in the optical recording medium of the first aspect can be provided in contact with the reproducing layer. Thereby, at the time of information reproduction, heat of the reproduction layer generated when the reproduction layer is heated by irradiation of the reproduction light can be diffused through the heat conductive layer. Therefore, a temperature distribution according to the light intensity distribution of the reproduction light is formed in the reproduction layer, and only a desired recording magnetic domain can be transferred from the recording layer by magnetostatic coupling or exchange coupling. As described above, the heat conductive layer can effectively control the temperature distribution of the reproducing layer at the time of reproducing information. Therefore,
The optical recording medium according to the second aspect of the present invention includes, for example, MS
Using the temperature distribution generated in the reproduction light spot of the reproduction layer when irradiating the reproduction light like R and MAMMOS,
This is extremely effective for a magneto-optical recording medium of a type in which only desired recording magnetic domains of a recording layer are transferred to a reproducing layer.

The heat conductive layer can be provided on the light incident side of the reproducing layer or on the opposite side thereof, and can be provided on both sides.

Further, the substrate used in the optical recording medium according to the first and second aspects of the present invention is made of a material having a light transmitting property, and has a transmittance of at least 70% for light having a wavelength of 560 nm or less. It is desirable to have As such a substrate material, a plastic material such as polycarbonate, polymethyl methacrylate, and amorphous polyolefin, glass, ceramic, and the like can be used.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical recording medium according to the present invention will be specifically described below with reference to the drawings, but the present invention is not limited to these embodiments.

[0023]

Embodiment 1 In this embodiment, a magneto-optical recording medium of a type in which light is incident from the substrate side was manufactured as a specific example of the optical recording medium according to the present invention. FIG. 1 shows a cross-sectional structure of the magneto-optical recording medium manufactured in this embodiment. Magneto-optical recording medium 10
Has a structure in which a reproducing layer 2, a heat conductive layer 3, a recording layer 4, a dielectric layer 5, and a reflective layer 6 are sequentially laminated on a transparent substrate 1.

In the structure shown in FIG.
Is a polycarbonate substrate produced by using an injection molding machine (not shown), has irregularities corresponding to the preformat pattern on its surface, and has a thickness of 1.2 mm. The reproducing layer 2 is a layer to which the magnetization of the recording layer is transferred by magnetostatic coupling with the recording layer at the time of reproducing information, and is made of GdFeCo. The heat conductive layer 3 is a layer for diffusing heat accumulated in the recording layer 4 to the transparent substrate 1 side, and is made of Cu. Cu constituting the heat conductive layer 3 has a reflection spectrum characteristic as shown in FIG.
It is near. The thermal conductivity of Cu is about 400 Wm ^-1.
K- ¹ . The recording layer 4 is a layer in which information is recorded as magnetization information, and is configured using TbFeCo. The dielectric layer 5 is a layer for causing multiple interference of light in the film to effectively increase the Kerr rotation angle, and is made of SiN. The reflective layer 6 is a layer for reflecting light transmitted through the recording layer 4 and diffusing heat of the recording layer due to light irradiation to the side opposite to the substrate 1, and is made of AlTi. These layers 2 to 6 were sequentially formed on the surface of the substrate on which the unevenness corresponding to the preformat pattern was formed using a sputtering device (not shown) under the following conditions.

First, in the formation of the reproducing layer 2, a Gd simple substance target and an FeCo alloy target were simultaneously sputtered to form a film having a thickness of 20 nm. In forming the thermal conductive layer 3, Cu is used as a target material and the thickness is 10 nm.
And In the formation of the recording layer 4, a Tb simple target and F
A film was formed by simultaneous sputtering with an eCo alloy target.
The thickness of the recording layer 4 was 100 nm.

In forming the dielectric layer 5, SiN was used as a target material and the film thickness was set to 40 nm. In forming the reflective layer 6, AlTi was used as a target material, and the film thickness was set to 50 nm. Under such film forming conditions, each layer 2-6
Was formed to produce a magneto-optical recording medium 10 having the laminated structure shown in FIG.

The magneto-optical recording medium 10 thus obtained is
For example, recording or reproduction of information can be performed by irradiating recording light or reproduction light from the substrate side using a recording and reproduction device equipped with a laser light source having a wavelength of 400 nm. When recording information, the recording light applied to the magneto-optical recording medium passes through the heat conductive layer 3 and reaches the recording layer 4, and heats the recording layer 4 based on the light intensity distribution of the laser light. At this time, the recording layer 4 generated by the laser beam irradiation
Is transmitted to the heat conductive layer 3 side and diffuses in the heat conductive layer 3 in the thickness direction. As a result, a Gaussian temperature distribution is formed in the recording layer 4 according to the light intensity distribution of the laser light,
As a result, a minute recording mark having a desired size and a sharp outline is formed. A reproduced signal with less jitter is detected from such a recording mark.

[0028]

Embodiment 2 Reproduction layer 2 of magneto-optical recording medium 10 of embodiment 1
A magneto-optical recording medium was manufactured in the same manner as in Example 1, except that the stacking order of the heat conductive layer 3 and the heat conductive layer 3 was changed to provide the heat conductive layer 3 on the light incident side of the reproducing layer 2. FIG. 6 shows a cross-sectional structure of the magneto-optical recording medium manufactured in this example. For convenience, the same layers as those used in the magneto-optical recording medium of the first embodiment are denoted by the same reference numerals as those used in the first embodiment. In the magneto-optical recording medium 60, since the reproducing layer 2 and the recording layer 4 are provided in contact with each other, the magnetic domains of the recording layer 4 are transferred to the reproducing layer 2 by exchange coupling during information reproduction.

Magneto-optical recording medium 6 having such a laminated structure
Similarly to Example 1, information recording or reproduction can be performed by irradiating recording light or reproduction light from the substrate side using a recording / reproducing apparatus equipped with a laser light source having a wavelength of 400 nm. Magneto-optical recording medium 60
Is provided with a heat conducting layer 3 on the light incident side of the reproducing layer 2, so that the heat of the reproducing layer 2 generated by irradiating the reproducing light during information reproduction is transmitted to the heat conducting layer 3 and 3 diffuses in the film thickness direction. Therefore, a desired temperature distribution can be formed in the reproducing layer 2, and a minute recording magnetic domain of the recording layer 4 can be transferred to the reproducing layer 2 through a predetermined temperature region formed based on this temperature distribution. .

[0030]

Embodiment 3 Between the recording layer and the reproducing layer of the magneto-optical recording medium 10 of Embodiment 1, a second layer having the same function as the heat conductive layer is further provided.
A magneto-optical recording medium was manufactured in the same manner as in Example 1 except that a heat conductive layer was provided and the thickness of the second heat conductive layer was changed to 10 nm. FIG. 7 shows a cross-sectional structure of the magneto-optical recording medium manufactured in this example. For convenience, the same layers as those used in the magneto-optical recording medium of the first embodiment are denoted by the same reference numerals as those used in the first embodiment.

The magneto-optical recording medium 7 having such a laminated structure
Similarly to Example 1, information recording or reproduction can be performed by irradiating recording light or reproduction light from the substrate side using a recording / reproducing apparatus equipped with a laser light source having a wavelength of 400 nm. Magneto-optical recording medium 70
Has a structure in which a heat conducting layer 3 is provided on the light incident side of the recording layer 4 and the reproducing layer 2 is sandwiched between the heat conducting layer 3 and the second heat conducting layer 3 'as shown in FIG. Have. Therefore, the heat of the recording layer 4 generated by irradiating the recording light at the time of information recording is diffused through the heat conductive layer 3,
A desired temperature distribution is formed on the recording layer 4, and heat of the reproducing layer 2 generated by irradiating the reproducing light at the time of reproducing information is generated by the heat conductive layers 3 and the second layer located on both upper and lower sides of the reproducing layer 2. The heat is diffused in the vertical direction by the heat conductive layer 3 ′, and a desired temperature distribution is formed in the reproducing layer 2. As described above, the magneto-optical recording medium according to the present embodiment has a configuration capable of simultaneously controlling the temperature distribution of the recording layer during information recording and the temperature distribution of the reproducing layer during reproduction. ing.

[0032]

Embodiment 4 In this embodiment, as another specific example of the optical recording medium according to the present invention, a magneto-optical recording medium of a type in which light is incident from the side opposite to the substrate was manufactured. FIG. 2 shows a cross-sectional structure of the magneto-optical recording medium manufactured in this embodiment. The magneto-optical recording medium 20 includes a reflective layer 22, a first dielectric layer 23, a recording layer 24, a second dielectric layer 25, and a heat conductive layer 26 on a transparent substrate 21.
And a protective layer 27 are sequentially laminated.

The transparent substrate 21 is a polycarbonate substrate produced using the same injection molding machine as that used in Example 1, and has a thickness of 1.2 mm. Reflective layer 22
Is a layer for reflecting the light transmitted through the recording layer 24 and diffusing the heat of the recording layer 24 due to light irradiation to the substrate 21 side, and is made of AlTi. The first dielectric layer 23 is a layer for causing multiple interference of light in the film to effectively increase the Kerr rotation angle, and is configured using SiN. The recording layer 24 is a layer in which information is recorded as magnetization information, and is configured using TbFeCo. The second dielectric layer 25 is a layer for enhancing light.
iN. The heat conductive layer 26 is a layer for diffusing the heat of the recording layer 24 generated by light irradiation to the protective layer 27 side, and is made of Cu. The thermal conductivity of Cu is about ^400W -1 ^{K -1.} The protective layer 27
It is a layer for protecting the layers 22 to 26 laminated on the substrate 21 and is made of carbon. These layers 22-
27 was sequentially formed on the surface of the substrate 21 on which unevenness corresponding to the preformat pattern was formed using the same sputtering apparatus as in Example 1 under the following conditions.

In forming the reflective layer 22, AlTi was used as a target material, and the film thickness was set to 50 nm. In forming the first and second dielectric layers 23 and 25, SiN was used as a target material, and the film thickness was 10 nm and 2 nm, respectively.
It was set to 0 nm. In forming the recording layer 24, a Tb simple substance target and a FeCo alloy target were simultaneously sputtered to form a film. The thickness of the recording layer 24 was 100 nm. In forming the heat conductive layer 26, Cu is used as a target material,
The film thickness was 10 nm. In forming the protective layer 27, carbon was used as a target material, and the film thickness was 10 nm.

The magneto-optical recording medium 20 thus obtained is
For example, recording or reproduction of information can be performed by irradiating recording or reproduction light from the protective layer 27 side using a recording and reproduction apparatus equipped with a laser light source having a wavelength of 400 nm. When recording information, the magneto-optical recording medium 20
Is transmitted through the heat conductive layer 26, reaches the recording layer 24, and heats the recording layer 24 based on the light intensity distribution of the laser light. At this time, the heat of the recording layer 24 generated by the laser beam irradiation is transmitted to the heat conductive layer 26 and diffuses in the heat conductive layer 26 in the thickness direction. As a result, a Gaussian temperature distribution is formed on the recording layer 24 in accordance with the light intensity distribution of the laser beam, and as a result, a fine recording mark having a clear contour and a desired size is formed. A reproduced signal with less jitter is detected from such a recording mark.

Although the optical recording medium according to the present invention has been described with reference to the embodiments, the present invention is not limited to this. The structure of the magneto-optical recording medium described in the first to fourth embodiments is merely an example, and can be applied to a magneto-optical recording medium of a light modulation recording system. That is, in addition to the recording layer and the heat conduction layer, various auxiliary layers, for example, an initialization layer, a reflection layer, a switching layer, a memory layer, and a protection layer may be provided for the purpose of overwriting or the like. In Examples 1 to 4, a magneto-optical recording medium was manufactured as an example of an optical recording medium according to the present invention. However, the present invention is not limited to this, and a phase-change optical recording medium or a write-once optical recording medium can also be manufactured. .

In the fourth embodiment, an example of the so-called film-surface incident type magneto-optical recording medium in which light is incident from the side opposite to the substrate has been described. As an example, SIL (Solid Immersion Len
A magneto-optical recording medium of the type that performs recording and reproduction by near-field light using a floating head equipped with a high NA (numerical aperture) lens called s) can also be used. In such a magneto-optical recording medium, in order to use a flying head, it is desirable that the protective layer 27 of FIG. 2 be made of a lubricant having lubricity. In addition, since the distance between the bottom surface of the lens and the surface of the recording layer needs to be maintained within の of the wavelength due to the restriction of near-field light, each of the protective layer (lubricant layer), the heat conductive layer, and the dielectric layer is required. The sum of the film thickness is 1/1 of the wavelength of the light used.
What is necessary is just to set those film thickness so that it may become four or less.

[0038]

The optical recording medium of the present invention has a heat conducting layer having a high thermal conductivity on the light incident side of the recording layer and / or the reproducing layer. And / or can be quickly diffused to the light incident side of the reproducing layer. This facilitates the control of the temperature distribution of the recording layer at the time of information recording, and at the time of information recording, the recording layer can be appropriately rapidly heated and cooled to form a good recording mark on the recording layer. At the time of information reproduction, a desired temperature distribution can be formed in the reproduction layer, and the transfer of the recording magnetic domain of the recording layer to the reproduction layer can be controlled. Therefore, the present invention is extremely effective for MSR and MAMMOS utilizing the temperature distribution of the reproducing layer.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magneto-optical recording medium manufactured in Example 1 of the present invention, which is an example of a type in which light is incident from a substrate side.

FIG. 2 is a schematic sectional view of a magneto-optical recording medium manufactured in Example 4 of the present invention, which is an example of a type in which light is incident from a side opposite to a substrate side.

FIG. 3 is a graph schematically showing a light reflection spectrum of Cu constituting a heat conductive layer.

FIG. 4 is a schematic cross-sectional view of a conventional magneto-optical recording medium, in which light is incident from the substrate side.

FIG. 5 is a schematic cross-sectional view of a conventional magneto-optical recording medium, in which light is incident from a protective layer side opposite to a substrate.

FIG. 6 is a schematic sectional view of a magneto-optical recording medium manufactured in Example 2 of the present invention, which is an example of a type in which light is incident from the substrate side.

FIG. 7 is a schematic sectional view of a magneto-optical recording medium manufactured in Embodiment 3 of the present invention, which is an example of a type in which light is incident from the substrate side.

FIG. 8 is a graph showing a relationship between a light extinction coefficient and a figure of merit of a heat conductive layer.

FIG. 9 is a graph showing how the figure of merit changes with the thickness of the heat conductive layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 21 Substrate 2 Reproduction layer 3, 25 Heat conduction layer 4, 24 Recording layer 5, 23 Dielectric layer 6, 22 Reflection layer 26 Protective layer 10, 20, 60, 70 Magneto-optical recording medium

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koji Nakagawa 6-27-12 Higashi-Koiwa, Edogawa-ku, Tokyo State 603 Higashi-Koiwa F-term (reference) 5D029 JB05 JB47 MA27

Claims (11)

[Claims] 1. An optical recording medium comprising: a first recording layer on which information is recorded on a substrate, wherein at least one of recording and reproduction of information is performed by irradiation of light; On the incident side, the thermal conductivity is 20 Wm ^-1 K
Optical recording medium, characterized in that it comprises a thermally conductive layer of ^-1 or more non-magnetic. 2. The optical recording medium according to claim 1, wherein the heat conductive layer is provided in contact with the recording layer. 3. An optical recording medium having a first recording layer and a reproduction layer on which information is recorded on a substrate, wherein at least one of recording and reproduction of information is performed by irradiating light, a heat conductivity of the optical recording medium is reduced. An optical recording medium, comprising a nonmagnetic heat conductive layer having a power of 20 Wm ^-1 K ^-1 or more in contact with the reproducing layer. 4. The optical recording medium according to claim 3, wherein the heat conductive layer is provided on a light incident side of the reproducing layer. 5. The optical recording medium according to claim 1, wherein the heat conduction layer has an extinction coefficient at the wavelength of the irradiated light of 3.0 or less. . 6. The heat conductive layer has a wavelength of 300 nm to 60 nm.
The optical recording medium according to any one of claims 1 to 4, having a light reflection end in a light reflection spectrum between 0 nm. 7. The heat conductive layer is made of Au, Cu, Ag, S
i and 1 selected from the group consisting of
The optical recording medium according to any one of claims 1 to 5, comprising a seed. 8. The wavelength of the irradiated light is 300 nm.
2. The method according to claim 1, wherein the wavelength is within a range of about 600 nm.
The optical recording medium according to any one of claims 1 to 7. 9. The heat conductive layer has a thickness of 1 nm to 200 nm.
The optical recording medium according to any one of claims 1 to 8, wherein the optical recording medium is in the range of nm. 10. The heat conductive layer is further provided on a side of the recording layer opposite to the light incident side.
The optical recording medium according to any one of the above. 11. The optical recording medium according to claim 1, further comprising a second recording layer on which information is recorded, on a light incident side of the heat conductive layer.