JP2003242677A - Multilayer recording medium and system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new configuration for a mass multilayer recording medium by utilizing light reflection on an adjoining interface between materials with different refractive indexes, and to provide a recording and reproducing method and a recording system in a mass multilayer recording medium. <P>SOLUTION: A multilayer recording medium provided with at least two or more recording layers is constituted so that a recording layer is formed in a laminated structure of different types of materials with different refractive indexes, and interfacial reflection of the different types of materials is used for at least either reading of recorded information or reading focus information and tracking information. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to multi-layer recording,
The present invention relates to a structure of a multi-layer recording medium that can be a large-capacity optical recording medium and an information recording / reproducing system using the same.

[0002]

2. Description of the Related Art There is a demand for a recording system having a large capacity and easy handling as a part of a computer system or a part of home entertainment equipment. In this application, there is an optical medium that is easy to handle and compatible with a high-speed, large-capacity hard disk, and competition for development is being developed.

The optical disc with the largest capacity, which is becoming widespread at present, is the DVD, and the DVD has a standard having two recording layers as a recording medium having a plurality of recording layers.
It is used for recording movies. In this system, a two-layer disc having pits transferred by a stamper is laminated after vapor deposition of an Al film as a reflection layer. In this material system, the reflectance per layer is high, and when the number of layers is increased, the number of layers increases and the S / N ratio of the read signal rapidly deteriorates.

On the other hand, there is a report of a multi-layer disc in which the reflectance per layer is lowered to an appropriately low value with good reproducibility. That is, in Japanese Patent No. 30666677, by providing an air gap between the disc layers, interface reflection (about 3.5%) between the disc (n = 1.492 for acrylic) and air (n = 1). It has been disclosed that about 10 layers can be formed by utilizing the above.

[0005]

[Patent Document 3] Patent Document 3
In the case of Japanese Patent Publication No. 066677, the number of layers is 1 at most.
The number of layers is 0, and the range of application is read-only R
Limited to OM systems.

However, in recent years, the capacity of a general hard disk has exceeded 10 GB and is about to reach 100 GB, but the storage capacity of an optical disk is about 20 GB in a single layer even in a system using a blue-violet laser, which is expected to be the next generation. Stay In such a situation, there is a demand for a large-capacity optical disc that does not impair the ease of handling and the securing of distributability, which is an advantage of the optical disc.

Therefore, the present invention has been made to solve the above-mentioned problems, and more recording layers than the above-mentioned Japanese Patent No. 30666677 can be multilayered and can be applied to a recordable medium. It is an object of the present invention to provide a structure of a large-capacity multilayer recording medium and an information recording / reproducing system.

[0008]

In order to solve the above problems, according to the invention of claim 1, in a multi-layer recording medium having at least two recording layers, the recording medium is a different material having different refractive indexes. The most main feature is that the interface reflection of the different materials is used for reading at least one of recording information and / or reading focus information and tracking information.

According to a second aspect of the invention, in the multi-layer recording medium according to the first aspect, a dye material recordable by light or heat is dispersed in one of the layers constituting the interface of different materials. It is a characteristic.

The third aspect of the present invention is characterized in that, in the multilayer recording medium according to the second aspect, the distribution of the dye in the layer in which the dye is dispersed is dispersed only on one or both surfaces. And

According to a fourth aspect of the present invention, the first to third aspects are provided.
The multi-layer recording medium according to any one of items 1 to 5, wherein the reflectance of the interface forming each recording layer is less than 3%.

According to the invention of claim 5, claims 1 to 4
The multi-layer recording medium according to any one of items 1 to 7, wherein one material constituting the different kinds of interface is a polymer containing fluorine.

According to a sixth aspect of the invention, the first to fifth aspects of the invention are provided.
The multi-layer recording medium according to any one of items 1 to 3, wherein a layer made of a polymer containing fluorine having grooves and pits on one side or both sides is formed by injection molding, and the polymer layers are laminated in multiple layers and different layers are made of different resins. The main feature is that it is filled and configured.

According to a seventh aspect of the present invention, in the multi-layer recording medium according to the fifth aspect, a layer made of a polymer containing fluorine having a groove on one side or both sides is formed by injection molding, and the surface having the groove is formed. The main feature is that after forming a membrane film layer containing a dye, the polymer layers are laminated in multiple layers and the layers are filled with different resins.

According to the invention of claim 8, the inventions of claims 1 to 7
The multi-layer recording medium according to any one of items 1 to 7, wherein the resin filling the laminated polymer layer is an ultraviolet curable resin.

The ninth aspect of the present invention is characterized mainly in that the information recording / reproducing system uses the multilayer recording medium according to any one of the first to eighth aspects.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In an optical disc, information is recorded as the presence or absence of pits formed on a recording layer.
In order to read the presence or absence of pits as a change in the intensity of light reflection, the light reflected from the reflective layer deposited on the recording layer was used to read indirectly. In this case, the merit is that the intensity of the returned light of the laser is high and a high S / N can be easily obtained due to the high reflectance of the metal vapor deposition film.

However, when a metal vapor deposition film is used as the reflective layer, the reflectance per layer is large and the transmission loss is large, so that the attenuation of the amount of laser light reaching the lower layer is large when the multilayer is formed. .

On the other hand, according to the structure of the present invention, the reflectance R when the interface reflection of different materials is used is R = (n ₁ −n) when the refractive indexes n ₁ and n ₂ of the two materials are used. ₂ ) ^ 2 /
It is represented by (n ₁ + n ₂ ) ^ 2. This means that a multilayer recording medium having a reflectance of less than several percent can be formed by forming an interface using a homogeneous material. Therefore, not only a multi-layer recording medium having more than 10 layers can be constructed, but also the transmission loss per layer is small, the attenuation of the read signal is small, and the detection system is not required to have a wide dynamic range as long as it has high sensitivity. There is an advantage that it is (it is difficult to realize a detector that satisfies both).

The dye material recordable by light or heat described in claim 2 means a material whose refractive index is changed by absorption of light or heat. Since this dye material is contained in either one of the layers of the different material interfaces constituting the present invention, the portion that has been irradiated with light or heat has no change in the refractive index in the layer containing no dye, There is a change in the refractive index in the part including. Therefore, the interface reflectance is modulated depending on the presence or absence of light or heat irradiation. Information is recorded and reproduced by utilizing this modulation of reflectance.

The constitution and operation of claim 3 are, unlike the case of claim 2, that the portion where the dye is present is limited to only the surface. If it is evenly distributed over the whole surface, it is possible to focus on either the front or back side, but since the modulation by the written information is continuous in the depth direction,
At worst, there may be interference between the two. Therefore, one of the front and back interfaces will be used as the recording layer, but if the dye is dispersed only on the surface, both interfaces will be present if there is a distance in the depth direction that can be optically resolved. It becomes possible to write information to.

In a multi-layer recording medium having more than 10 layers, the reflectance at the interface is preferably less than 3% in order to prevent abrupt attenuation of the read light quantity of the lower layer.

The polymer containing fluorine as defined in claim 5 generally has a low refractive index. Therefore, a larger refractive index difference can be provided at the interface between the fluorine-containing polymer and a general polymer such as acrylic / polycarbonate / polystyrene, and as a result, the amount of reflected light can be increased. The above structure can also be used for a part of a multilayer recording medium. For example, by using it in the lower recording layer, it becomes possible to compensate for the decrease in the amount of reflected light from the lower layer and achieve a flattened amount of reflected light.

[0024]

Embodiments of the present invention will be described in detail below with reference to the drawings.

[0025]Example 1 In Example 1, a multi-layer recording medium which is an example of the present invention is described.
Show. In Example 1, the reflectance of each recording layer satisfies claim 4.
As described above, the reflectance of the interface constituting the recording layer is less than 3%.
A layer recording medium, and an ultraviolet curable resin between the layers according to claim 8.
It is manufactured by a filling manufacturing method. In addition, in claim 9.
An example of the information reading method of the information reproducing system shown
Explain.

A method of manufacturing a multi-layer recording medium will be described with reference to FIG. In FIG. 1, the recording surface of the recording medium is enlarged, and an arbitrary shape can be adopted for the chucking portion and the like of the disc. (A) Prepare stampers 101 and 102 in which lands, grooves, and pits are carved. In this embodiment, since the recording surfaces are provided on both sides, pits are formed on both stampers 101 and 102, but a structure having only one side can be adopted. (B) The recording layer 103 is molded by injection molding using the stampers 101 and 102. Polycarbonate was used as the material of the recording layer 103, but other optical grade polymers can be used as long as the combination has a desired refractive index difference with the polymer filling the recording layer described later. In this embodiment, the recording layer was molded by injection molding, but other molding methods such as thermal polymerization in a stamper and ultraviolet curing can be adopted. (C) The recording layer 103 removed from the stamper was obtained. (D) After the recording layer 103 is laminated on the support substrate 104 with the ultraviolet curable resin 105 interposed therebetween, the protective layer 106 is laminated and irradiated with ultraviolet rays to be solidified and integrated. The ultraviolet curable resin used is an acrylic resin and is a polycarbonate recording layer 10.
There is a difference in refractive index of about 0.1 from 3 and the reflectance at the interface is about 0.1%. The multi-layer recording medium of the present invention is not limited to three layers, and the material of the different kinds of interfaces constituting the recording layer is not limited to the combination of polycarbonate and acrylic shown in Example 1, and the intended reflectance can be obtained. A combination of different materials satisfying the difference in refractive index that can be obtained can be adopted.

Next, a method of reading information from the multilayer recording medium will be described with reference to FIG. The readout light emitted from the semiconductor laser 209 is converted into parallel rays by the coupling lens 208, then passes through an optical isolator including a polarization beam splitter (PBS) 204 and a quarter wavelength plate 203, and is converted into circularly polarized light. A part of the read-out light condensed by the condensing lens 202 on a different type interface forming one of the recording surfaces of the multilayer recording medium 201 is reflected due to the difference in refractive index (in the case of the first embodiment, about 0. 1%). The direction of optical rotation of this reflected light is reversed,
It is converted into linearly polarized light having a polarization direction perpendicular to the readout light by the quarter-wave plate 203, reflected by the PBS 204, passed through a condenser lens 205 and a cylindrical lens 206, and led to a four-division avalanche photodiode (4D-APD) 207. Get burned. Focusing and track control are performed by the signal detected by the 4D-APD 207 with high sensitivity, and the recording signal is reproduced. In the present invention, by using a highly sensitive 4D-APD for the detection system, it is possible to detect a recording signal with high sensitivity, and it is possible to increase the capacity by increasing the number of layers. The information reading method described with reference to FIG. 2 is an example of the embodiment of the present invention, and it goes without saying that other configurations can be adopted. Further, the form of the medium is not limited to the disk, and other forms such as a card can be adopted.

[0028]Example 2 Example 2 shows a multi-layer recording medium which is an example of the present invention.
Show. In Example 2, the reflectance of each recording layer shown in claim 3 was
A multi-layer recording medium satisfying claim 4. In addition, the claim
Writing and reading information in the information reproducing system shown in FIG.
An example of the delivery method will be described. Fabrication of multilayer recording media
The method is shown using FIG. FIG. 3 shows the recording surface of the recording medium.
The disk chucking part is of any shape.
The shape can be adopted. (A) Stamper 30 with engraved land and groove
1 and a stamper 302 that forms the back surface that transmits ultraviolet rays
To prepare. In this embodiment, the recording surface is provided on one side.
Therefore, the land and groove are carved only on the stamper 301.
However, when it is used as a ROM, it has land on both sides.
It is also possible to have a configuration with grooves and pits formed.
It (B) UV curable resin between the stampers 301 and 302
And then cured by ultraviolet rays to form the medium 303
It Acrylic UV curable resin is used for the material of medium 303
However, the refractive index of the polymer that fills the recording layer described later
If the difference is a combination that takes a desired value, another optical gray
It is possible to use a polymer of a cord. Also, ultraviolet
In addition to molding with wire-curing resin, heat load inside the stamper
It is also possible to use other molding methods such as
is there. (C) Spin on the medium 303 removed from the stamper.
Recording consisting of polymer film containing dye by coating
The layer 304 was formed. The polymer that forms the recording layer is poly
A carbonate resin, which has a refractive index difference from that of the medium 303.
Focusing and tracking control through surface reflection
To do. (D) The support substrate 307 is described with the thermopolymerization resin 306 interposed therebetween.
After laminating the composite of the recording layer 304 and the medium 303, a protective layer
305 is laminated and solidified and integrated by thermal polymerization. The present invention
The multi-layer recording medium is not limited to three layers
The material of the different kinds of interfaces forming the layer is the same as that of the second embodiment.
Not limited to the combination of carbonate and acrylic
The refractive index difference that can obtain the desired reflectance.
It is possible to employ a combination of different materials.

Next, a method of writing information from the multi-layer recording medium will be described with reference to FIG. The readout light emitted from the semiconductor laser 409 is converted into parallel rays by the coupling lens 408, then passes through the optical isolator including the polarization beam splitter (PBS) 404 and the quarter wavelength plate 403, and is converted into circularly polarized light. A part of the reading light condensed by the condensing lens 402 on a different type interface forming one of the recording surfaces of the multilayer recording medium 401 is reflected due to the difference in refractive index (in the case of the second embodiment, about 0. 1%). The direction of optical rotation of this reflected light is reversed,
It is converted into linearly polarized light in a polarization direction perpendicular to the readout light by the quarter-wave plate 403, reflected by the PBS 404, passed through a condenser lens 405 and a cylindrical lens 406, and then becomes a four-division avalanche photodiode (4D-APD) 407. Be guided. Focusing and track control are performed by a signal detected by the 4D-APD 407 with high sensitivity. At the time of tracking, the output is controlled so that the exposure by the reading laser can be ignored, and at the time of writing, the output modulation of the semiconductor laser is performed according to the written information to form a recording pit. A change in the refractive index occurs due to the exposure of the dye, and as a result, the reflected light is modulated according to the recording pit. In the present invention, by using a highly sensitive 4D-APD for the detection system, it is possible to detect the recording signal with high sensitivity, and it is possible to detect the modulation by the writing information of the reflected light as an electric signal. As described above, it is possible to increase the capacity by increasing the number of writable recording media. The information reading method described with reference to FIG. 4 is an example of the embodiment of the present invention, and it goes without saying that other configurations can be adopted. Further, the form of the medium is not limited to the disk, and other forms such as a card can be adopted.

[0030]Example 3 In Example 3, a multi-layer recording medium that is an example of the present invention is described.
Show. The third embodiment relates to each of claims 3, 5, 6, and 7.
A multilayer recording medium in which the reflectance of the recording layer satisfies claim 4.
It A method for manufacturing the multilayer recording medium will be described with reference to FIG. Figure 5
Expands the recording surface of the recording medium, and
An arbitrary shape can be adopted for the locking portion and the like. (A) Stamper 50 with engraved land and groove
1 and the stamper 502 without the groove that forms the back side
prepare. In this embodiment, since the recording surface is provided on one side,
Only stamper 501 has engraved lands and grooves
However, when it is used as a ROM, it has land and glue on both sides.
It is also possible to adopt a configuration in which a groove and a pit are formed. (B) Fluorine-containing poly is used between the stampers 501 and 502.
Teflon (registered trademark) AF, which is a type of mer (for example,
A medium 503 is molded by injecting a refractive index of 1.35). Medium
The material of the body 503 is a polymer that fills the recording layer described later.
If the difference in refractive index between
It is possible to use the following optical grade polymers.
The medium 503 is described by injection molding in this embodiment.
Although the recording layer was molded, thermal polymerization in the stamper and ultraviolet rays
It is also possible to adopt other molding methods such as curing. (C) Spin on the medium 503 removed from the stamper.
Recording consisting of polymer film containing dye by coating
The layer 504 was formed. The polymer that forms the recording layer is poly
It is a carbonate resin and has a refractive index difference from that of the medium 503.
Focusing and tracking control through surface reflection
To do. In this case, the difference in refractive index between the two is about 0.25,
Approximately 2.5 times the combination of carbonate and acrylic
It The reflectance is about 0.7%, which is about 7 times. (D) The thermosetting resin 506 is placed on the supporting substrate 507,
After stacking the composite of the recording layer 504 and the medium 503, a protective layer
505 are laminated and solidified by thermal polymerization to be integrated. The present invention
The multi-layer recording medium is not limited to three layers
The material of the heterogeneous interface forming the layer is the same as that of the material of the third embodiment.
Limited to the combination of carbonate and Teflon AF
Not the difference in refractive index that can obtain the intended reflectance.
A combination of different materials that satisfy the requirements can be adopted.

The multi-layer recording medium created in this embodiment can record / reproduce information by the same principle and system as the multi-layer recording medium of the second embodiment. It goes without saying that the multi-layer recording medium described with reference to FIG. 5 is an example of the embodiment of the present invention and can have other configurations. Further, the form of the medium is not limited to the disk, and other forms such as a card can be adopted.

[0032]

As described above, according to the first aspect, in a multi-layer recording medium having at least two recording layers, the recording medium has a laminated structure of different materials having different refractive indexes, and Since the multi-layer recording medium is characterized in that the interface reflection of different materials is used for reading recording information and / or reading focus information and / or tracking information, the refractive index of the material is stable in the medium. The reflectance of the medium is determined, and as a result, it is possible to easily obtain a recording layer having a uniform reflectance in the layer and in the medium, and to obtain a large-capacity multilayer recording medium capable of stably reading recorded information. In addition, a wider range of reflectance can be set than when a solid-gas interface is used as the different interface. On the other hand, when a metal-based reflective layer having a high reflectance is used in the first place, a high transmittance is required to read the lower recording layer as the number of recording layers constituting the medium increases. For this reason, it is difficult to suppress variations in each layer in the recording surface or in the medium, and also between the media, because it is necessary to uniformly form a reflective film having a thickness around the wavelength of light.

According to a second aspect, in the multi-layer recording medium according to the first aspect, a dye material recordable by light or heat is dispersed in one of the layers constituting the interface of different materials. Since it is a multi-layered recording medium, in addition to the merit of the invention of claim 1, by dispersing a dye material recordable by light or heat in the recording layer,
Information can be written after the media is created. The medium of the present invention can be created as a medium that can be recorded only once or a medium that can be repeatedly recorded and erased by selecting a material according to the application.

According to a third aspect, in the multilayer recording medium according to the second aspect, the distribution of the dye in the layer in which the dye is dispersed is dispersed only on one or both surfaces. Since it is a recording medium, it is possible to design the medium in consideration of interference between reading and writing between the stacked recording layers and workability of the material. Specifically, when a material that makes it easier to form a thin layer is used, it is possible to provide the recording surface on only one side and provide a gap between the recording layers during lamination. When the recording layer is relatively thick, the number of recording layers per thickness can be increased by providing the recording layers on both sides.

According to claim 4, the multilayer recording medium according to any one of claims 1 to 3 is characterized in that the reflectance of the interface constituting each recording layer is less than 3%. Since the reflectance is low and the transmittance is high per layer, the problem of abrupt decrease in the amount of light reflected from the lower layer, which is a problem when a large number of recording layers are stacked, is avoided, and high S A read signal of / N can be obtained. In addition, even when using a high-sensitivity detection system, there is no extreme level difference in the signal intensity from the upper layer portion and the lower layer portion of the read signal, and it is possible to photoelectrically convert all signals with one detection system. Cost reduction is possible.

According to a fifth aspect of the present invention, there is provided the multilayer recording medium according to any one of the first to fourth aspects, wherein one of the materials constituting the different kinds of interfaces is a polymer containing fluorine. The fluorine-containing polymer has a lower refractive index than the polymer before adding fluorine. Therefore,
It is possible to increase the difference in refractive index forming the different kinds of interfaces, and the control range of the reflectance at the interfaces is widened. As the fluorine-containing polymer, an acrylic or epoxy UV-curable resin or the like can be selected from the materials for injection molding at present, and various methods for producing a multi-layer recording medium are possible.

According to a sixth aspect, in the multilayer recording medium according to the fifth aspect, a layer made of a polymer containing fluorine having grooves and pits on one side or both sides is formed by injection molding, and the polymer layer is formed. Since it is a multi-layer recording medium characterized in that it is configured by laminating multiple layers and filling the layers with different resins, it is possible to take a medium configuration that takes advantage of the transparency of the resin containing fluorine,
Further, a wide range of reflectance can be set by taking advantage of the low refractive index characteristic of the resin containing fluorine.

According to a seventh aspect, in the multilayer recording medium according to the fifth aspect, a layer made of a fluorine-containing polymer having a groove on one side or both sides is formed by injection molding, and the layer having a groove is formed on the surface. Since the multi-layer recording medium is characterized in that after forming a film layer containing a dye, the polymer layers are laminated in multiple layers and the layers are filled with different resins, recording in addition to the merit of claim 6 Possible media can be obtained. The large degree of freedom in setting the reflectance contributes to the improvement of the read S / N, especially in a recordable medium.

According to the eighth aspect, in the multilayer recording medium according to the sixth and seventh aspects, the resin filling the laminated polymer layer is an ultraviolet curable resin. In the coating process on the adhesive surface, the coating film thickness can be easily adjusted by spin coating or the like, and the one having a constant optical property can be obtained. In addition, the time required to complete the solidification after stacking the media is shortened, and the manufacturing cost can be reduced. The ultraviolet curable resin has a wide range of refractive index such as a fluorine-containing polymer or a sulfur-containing polymer based on the above-mentioned polymer in addition to a usual acrylic resin or epoxy resin, and has a high degree of freedom in optical design.

According to the ninth aspect, since the information recording / reproducing system uses the multilayer recording medium according to the first to eighth aspects, the conventional optical disk system is modified to be compatible. It is possible to design a capacity multi-layer recording system. In addition, when compatibility is not required for the conventional system, a system using a medium smaller than that of the conventional system is possible. The existing equipment and know-how for the coating process for optical disks can be diverted. Therefore, in terms of yield, the conventional technique can be diverted, and in terms of manufacturing, since it is a simple process of laminating multiple layers, it is a large-capacity multilayer recording system with high yield and low manufacturing cost.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an optical system according to a first embodiment of the present invention.

FIG. 3 is a process explanatory diagram according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram of an optical system according to a second embodiment of the present invention.

FIG. 5 is a process conceptual diagram according to a third embodiment of the present invention.

[Explanation of symbols]

101: Stamper 102: Stamper 103: Recording layer 104: Support substrate 105: UV curable resin 106: Protective layer 201: Multilayer recording medium 202: Condenser lens 203: 1/4 wavelength plate 204: Polarization beam splitter (PBS) 205: Condensing lens 206: Cylindrical lens 207: Quadrant avalanche photodiode (4D
-APD) 208: Coupling lens 209: Semiconductor laser 301: Stamper 302: Stamper 303: Medium 304: Recording layer 305: Protective layer 306: Thermopolymer resin 307: Support substrate 401: Multilayer recording medium 402: Condensing lens 403: Quarter wave plate 404: Polarization beam splitter (PBS) 405: Condensing lens 406: Cylindrical lens 407: Four-division avalanche photodiode (4D)
-APD) 408: Coupling lens 409: Semiconductor laser 501: Stamper 502: Stamper 503: Medium 504: Recording layer 505: Protective layer 506: Thermopolymer resin 507: Support substrate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI theme code (reference) G11B 7/24 538 G11B 7/24 538R 7/004 7/004 Z 7/007 7/007 7/09 7 / 09 AF term (reference) 5D029 HA07 JA04 JB06 JB13 JB33 JC06 JC11 MA03 NA03 NA06 NA12 NA22 NA25 5D090 AA01 BB02 BB07 BB12 BB17 CC01 CC04 CC12 CC14 DD01 DD05 FF02 FF05 FF11 5D118 BA01 BB08 CD02 CD03

Claims (9)

[Claims] 1. A multi-layer recording medium having at least two recording layers, wherein the recording medium has a laminated structure of different materials having different refractive indexes, and the interface reflection of the different materials is read out or focused on the recording information. A multi-layer recording medium, which is used for at least one of reading information and tracking information. 2. The multilayer recording medium according to claim 1, wherein a dye material recordable by light or heat is dispersed in one of the layers forming the interface of different materials. 3. The multilayer recording medium according to claim 2, wherein the distribution of the dye in the layer in which the dye is dispersed is dispersed only on one or both surfaces. 4. The multilayer recording medium according to claim 1, wherein the interface of each recording layer has a reflectance of less than 3%. 5. The multilayer recording medium according to claim 1, wherein one material forming the different kinds of interfaces is a polymer containing fluorine. 6. The multi-layer recording medium according to claim 1, wherein a layer made of a fluorine-containing polymer having grooves and pits on one side or both sides is formed by injection molding, and the polymer is used. A multi-layer recording medium comprising a plurality of layers laminated and different layers filled with different resins. 7. The multilayer recording medium according to claim 5, wherein a layer made of a fluorine-containing polymer having a groove on one side or both sides is formed by injection molding, and a film containing a dye on the surface having the groove. A multilayer recording medium, characterized in that after the layers are formed, the polymer layers are laminated in multiple layers and each layer is filled with a different resin. 8. The multilayer recording medium according to claim 1, wherein the resin filling the laminated polymer layer is an ultraviolet curable resin. 9. An information recording / reproducing system comprising the multilayer recording medium according to claim 1. Description: