JPH11227334A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a crosstalk cancellation by controlling an absorptivity by one recording film. SOLUTION: A recording film 3 of the optical recording medium having the film 3 formed on a base plate 1 having a guide groove 2 is formed of a mixture of a metal and a dielectric. When a recording pulse is illuminated to the film 3, the metal is reacted with the dielectric, and hence an oxide is, for example, formed. And, since the oxide has a higher light transmittance than that of the metal, the film 3 is made of the mixture of the metal and the oxide. Thus, the light transmittance, reflectivity of the film can be easily controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel optical recording medium having a write-once recording layer and capable of increasing the capacity.

[0002]

2. Description of the Related Art Optical disks that can be recorded only once, so-called write-once disks, are roughly classified into those having a recording layer formed of an inorganic material and those having a recording layer formed of an organic dye material.

Of these, the one using an organic dye material is overwhelmingly used because it can be manufactured at low cost due to the difference in manufacturing process, and has the same reflectance as a so-called CD-ROM. That is the current situation.

A write-once medium using this organic dye material is called a CD-R, and is used as an external storage device of a computer.

In recent years, write-once media using an organic dye material has also been developed for so-called digital video discs (DVDs). Since the media has an extremely large capacity, an optical disc on which software is written is manufactured. It is used for recording of official documents and the like by using it for verification at the time and utilizing the fact that rewriting is impossible.

[0006]

By the way, in the field of optical recording, in order to realize higher-density recording, not only the guide groove is used as a recording area but also the guide groove is formed as a concave portion. To record in the area (so-called land) that becomes a convex part (land groove recording)
Has been proposed.

In this land-groove recording, a method called crosstalk cancellation has been proposed in order to achieve higher-density recording. This crosstalk cancellation is equivalent to the reflectance of the recording mark and the reflectance due to the extinction by interference of the primary light and the secondary light based on the phase difference derived from the groove depth of the guide groove. ) Is reproduced so that a signal of a concave portion (groove) is not leaked, and a signal of a convex portion is not leaked when reproducing a concave portion.

However, in a write-once medium in which a recording layer is formed of a conventional organic dye material, it is difficult to set conditions for achieving crosstalk cancellation, and it is very difficult to obtain a film configuration required for land / groove recording. .

Therefore, the present invention has been proposed in view of the above-mentioned conventional situation, and is a novel optical system capable of canceling crosstalk and capable of coping with higher NA, lower noise and higher capacity. It is an object of the present invention to provide a recording medium, in particular, a new write-once medium.

[0010]

In order to achieve the above object, an optical recording medium of the present invention comprises a recording film formed on a substrate having a guide groove, wherein the recording film is made of a metal and a dielectric. It is characterized by comprising a mixture.

When the recording film is made of a mixture of a metal and a dielectric, and is irradiated with recording light, the metal and the dielectric react to change the reflectance or the refractive index, and information is recorded.

Further, the oxide has a higher light transmittance than the metal. Therefore, by setting the recording film to a mixture of the metal and the oxide, the transmittance and the reflectance of the recording film can be easily and appropriately controlled. Thus, crosstalk cancellation can be achieved with only one recording film.

[0013]

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

FIG. 1 shows an example of an optical recording medium to which the present invention is applied.
Shown in This optical recording medium basically comprises a recording film 3 formed on an optically transparent substrate 1 on which a guide groove 2 is formed. Light is irradiated, and a part of the light is absorbed or reflected by the recording film 3.

Of course, a dielectric layer can be provided as appropriate for the enhancement effect and the like, and a reflective film can be provided. In conventional optical recording media, the properties of the recording film are affected by the surface properties of the substrate affecting the crystallinity of the reflective film, or by the interface shape formed by the particle size depending on the composition of the reflective film. Reach. In the optical recording medium of the present invention, since the recording film is made of a mixture of metal and dielectric and is made amorphous as described later, the influence derived from the crystallinity of the reflection film is eliminated.

As the transparent substrate 1, a transparent resin substrate, a glass substrate, or the like can be used. For example, a polycarbonate substrate on which the guide groove 2 is transferred by injection molding is preferable. In this case, the thickness of the transparent substrate 1 is 0.3
The range is about 1.2 mm, which is treated as a so-called rigid substrate.

In the case of the optical recording medium shown in FIG. 1, the recording / reproducing light is irradiated from the transparent substrate 1 side. Conversely, as shown in FIG. It is also possible to form the light transmitting layer 4 thereon and irradiate recording / reproducing light from the light transmitting layer 4 side.

In the optical recording medium shown in FIG. 2, by setting the thickness of the light transmitting layer 4 to 10 to 177 μm and combining it with an optical system having a high NA, an unprecedentedly high recording density can be realized.

The light transmitting layer 4 can be formed, for example, by applying an ultraviolet curing resin, or can be formed by bonding a light transmitting film with an ultraviolet curing resin. In the latter case, the total thickness is preferably set to 10 to 177 μm.

When the configuration shown in FIG. 2 is adopted, the substrate 1 only has to play a role as a supporting substrate, and does not necessarily have to be transparent.

Alternatively, a transparent sheet made by injection molding, casting, or the like can be used for the transparent substrate 1. By setting the thickness of the transparent sheet to 10 to 177 μm and combining an optical system with a high numerical aperture (NA), an optical recording medium with a much higher recording density than before can be realized. When using this transparent sheet,
The concavo-convex pattern such as the guide groove 2 and the signal pit can be easily transferred and formed by heating and pressing the master stamper at a high temperature.

When the above-mentioned transparent sheet is used for the substrate 1, a sheet-shaped optical recording medium (a so-called flexible optical disk) can be used as it is. For example, as shown in FIG. This can be bonded to the support substrate 6 via the cured resin 5 or the like to form a rigid disk. At this time, the supporting substrate 6 to be used is not necessarily transparent. For example, a substrate made of a thermoplastic resin and having a thickness of about 0.6 to 1.2 mm is used. Further, when the support substrate 6 is bonded, the surface of the recording film 3 may be subjected to silane treatment to improve the adhesion with the ultraviolet curable resin.

In the optical recording medium having the above-described structure, the recording film 3 is made of a mixture of a metal and a dielectric, and its light transmittance, reflectance and refractive index can be controlled by the ratio. Configuration.

Here, as the metal material, any metal material can be used, and Li, Be, Na, Mg, A
1, Si, K, Ca, Sc, Ti, V, Cr, Mn, F
e, Co, Ni, Cu, Zn, Ga, Ge, Se, R
b, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh,
Pd, Ag, Cd, In, Sn, Sb, Te, Cs, B
a, La, Ce, Pr, Nd, Pm, Sm, Eu, G
d, Tb, Dy, Ho, Er, Tm, Yb, Lu, H
f, Ta, W, Re, Os, Ir, Pt, or Au alone or an alloy of two or more of them can be used.

As the dielectric, Li, Be, N
a, Mg, Al, Si, K, Ca, Sc, Ti, V, C
r, Mn, Fe, Co, Ni, Cu, Zn, Ga, G
e, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc,
Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, T
e, Cs, Ba, La, Ce, Pr, Nd, Pm, S
m, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, Lu, Hf, Ta, W, Re, Os, Ir, Pt,
Oxides, nitrides, fluorides, sulfides, chlorides, bromides, iodides and the like of one or more metals selected from Au can be mentioned.

At this time, it is desirable that the mixing ratio of the metal and the dielectric is such that the concentration of the metal is 1 mol% or more and 80 mol% or less. When the concentration of the metal becomes less than 1 molecule%,
It cannot function as a recording film. Conversely, if the concentration of the metal exceeds 80% by mole, light transmittance is lost, and crosstalk cancellation becomes difficult.

By irradiating the recording film 3 with a recording pulse, the metal in the recording film 3 is oxidized, nitrided, sulfurized, fluorinated, chlorinated, brominated, or iodinated. Make a change.

At this time, crosstalk cancellation for high-speed recording can be realized by making the refractive index change and the reflectivity appropriate.

Specifically, assuming that the refractive index after writing is n, the relationship 1.0 ≦ n ≦ 2.0 is satisfied;
Alternatively, it is necessary that the reflectance of the recording mark be 4% or less.

Although the basic configuration of the optical recording medium to which the present invention has been applied has been described above, this is merely an example, and the present invention can be applied to optical recording media having various structures. Hereinafter, these optical recording media will be described.

First, application to an optical recording medium having a multilayer structure, an optical recording medium having a double-sided structure, and the like will be described.

FIG. 4 shows an example in which two recording media 3 are formed on a pair of transparent substrates 11 and 12 each having a thickness approximately half that of an optical recording medium to be finally obtained, thereby forming a double-sided disk. is there.

In this case, each recording film 3 is irradiated from both sides by irradiating light through the transparent substrates 11 and 12.
Can be recorded and reproduced.

FIG. 5 shows an example in which light-transmitting layers 14 and 15 each having a recording film 3 formed thereon are bonded to both surfaces of one supporting substrate 13 to form a double-sided disk.

In this case, by irradiating light from the light transmitting layers 14 and 15, recording and reproduction can be performed on each recording film 3 from both sides.

FIG. 6 shows a first recording film 2 on a transparent substrate 21.
This is an example of an optical recording medium (multi-layer optical disc) having a multilayer structure in which the second and second recording films 23 are formed via an optically transparent intermediate layer 24. In a multi-layer optical disc, the reflectance of the recording film is set to gradually decrease toward the light incident side (toward the transparent substrate 21).

In this multi-layer optical disc, recording and reproduction are performed on the recording films 22 and 23 from one side (the transparent substrate 21 side).

Although the examples of the double-sided optical disk and the multilayer optical disk have been described above, it is also possible to add layers having various functions to a single-plate optical disk.

FIG. 7 shows a skew correction layer 34 formed on the surface of the support substrate 31 opposite to the surface on which the recording film is formed in a single-plate optical disk having the recording film 32 and the light transmitting layer 33 formed on the support substrate 31 in this order. FIG.

In the single-plate disk, since the recording film 32 and the light transmitting layer 33 are formed only on one side, the warp easily occurs and the skew is a serious problem. Therefore, the skew correction layer 34 is formed by applying an ultraviolet curable resin or the like to the surface on the opposite side, and the skew is prevented by canceling the warpage.

Here, it is preferable that the ultraviolet curable resin or the like used for the skew correction layer 34 has a higher curing shrinkage than the material forming the light transmitting layer 33.

FIG. 8 shows an example in which a transparent protective layer 35 is formed on the light transmitting layer 33 for the purpose of improving the surface hardness and preventing electrification.

As described above, in the optical recording medium of the present invention, an ultraviolet ray is formed on a recording film, a dielectric layer, or a reflection film to form a light transmitting layer or to bond the optical recording medium to a supporting substrate. It may be necessary to apply a cured resin. At this time, in order to improve the adhesiveness with the ultraviolet curable resin, it is also effective to subject the surfaces of the recording film, the dielectric layer, and the reflective film to silane treatment in advance.

[0044]

EXAMPLES Hereinafter, specific examples to which the present invention is applied will be described with reference to experimental results.

Example 1 A mixed film of a metal and a dielectric was formed as a recording film by sputtering on a polycarbonate substrate having a thickness of 0.6 mm. As a material of the recording film, Zn was used as a metal, and SiO ₂ was used as a dielectric, and a mixed film having a ratio of 50 mol% was used.

On the other hand, a laser diode having a wavelength of 650 nm was used, and a lens having a numerical aperture of 0.6 was used.
When recording was performed at m / sec and a bit length of 0.38 μm, a jitter of 6% was obtained.

Example 2 A mixed film of a metal and a dielectric was formed as a recording film by sputtering on a polycarbonate substrate having a thickness of 0.6 mm. As a material of the recording film, In was used as a metal, and Al ₂ O ₃ was used as a dielectric.

On the other hand, using a laser diode having a wavelength of 650 nm and a lens having a numerical aperture of 0.6, a linear velocity of 5
When recording was performed at m / sec and a bit length of 0.38 μm, a jitter of 6% was obtained.

Example 3 A mixed film of metal and dielectric was formed as a recording film on a polycarbonate substrate having a thickness of 0.6 mm by sputtering. As a material of the recording film, Sn was used as a metal and SiO ₂ was used as a dielectric, and a mixed film having a ratio of 50 mol% was used.

On the other hand, a laser diode having a wavelength of 650 nm was used, and a lens having a numerical aperture of 0.6 was used.
When recording was performed at m / sec and a bit length of 0.38 μm, a jitter of 6% was obtained.

[0051]

As is clear from the above description, according to the present invention, the absorptance can be controlled by the recording film alone, and the crosstalk cancellation can be easily realized.

Further, according to the present invention, a novel optical recording medium capable of coping with high NA, low noise, and high capacity, in particular,
It is possible to provide new write-once media.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part showing an example of an optical disk in which a recording film is formed on a transparent substrate provided with a guide groove.

FIG. 2 forms a recording film on a transparent substrate provided with a guide groove,
FIG. 4 is a schematic cross-sectional view of a main part showing an example of an optical disk having a light transmission layer formed thereon.

FIG. 3 is a schematic cross-sectional view of a main part showing an example of an optical disk in which a light transmitting layer on which a recording film is formed is bonded to a support substrate.

FIG. 4 is a schematic sectional view showing an example of a bonded double-sided optical disc.

FIG. 5 is a schematic cross-sectional view showing an example of a double-sided optical disc in which a light-transmitting layer having a recording layer formed on both surfaces of a single substrate is bonded.

FIG. 6 is a schematic sectional view showing an example of a multilayer optical disc.

FIG. 7 is a schematic sectional view showing an example of an optical disc provided with a skew correction layer.

FIG. 8 is a schematic sectional view showing an example of an optical disc provided with a transparent protective layer.

[Explanation of symbols]

 1 transparent substrate, 2 guide groove, 3 recording film, 4 light transmission layer

Claims (11)

[Claims] 1. An optical recording medium comprising: a recording film formed on a substrate having a guide groove; wherein the recording film is made of a mixture of a metal and a dielectric. 2. The optical recording medium according to claim 1, wherein a ratio of the metal contained in the recording film is 1 to 80 molecular%. 3. A light transmitting layer having a thickness of 10 to 177 μm is formed on the recording layer, and recording and / or reproducing is performed by irradiating light from the light transmitting layer side. 2. The optical recording medium according to 1. 4. The recording and / or reproducing apparatus according to claim 1, wherein the substrate is a sheet-like substrate having a thickness of 10 to 177 μm, and recording and / or reproduction is performed by irradiating light from the sheet-like substrate side. Optical recording medium. 5. The optical recording medium according to claim 4, wherein a support substrate is bonded to said sheet substrate. 6. The optical recording medium according to claim 1, wherein a plurality of said recording layers are laminated via a light transmitting layer. 7. The optical recording medium according to claim 6, wherein the reflectance of the plurality of recording layers is set so as to gradually decrease toward the light incident side. 8. The optical recording medium according to claim 1, wherein the recording layer has a reflectance changed by a reaction between a metal and a dielectric to form a recording mark. 9. The optical recording medium according to claim 8, wherein the reflectance of the recording mark formed by the reaction is 4% or less. 10. The optical recording medium according to claim 1, wherein a refractive index of the recording layer is changed by a reaction between a metal and a dielectric to form a recording mark. 11. The optical recording medium according to claim 10, wherein the refractive index n of the recording mark formed by said reaction satisfies 1.0 ≦ n ≦ 2.0.