JP2002063735A - Optical information recording medium and optical information recording method - Google Patents

Abstract

(57) [Problem] To provide an optical information recording medium and an optical information recording method using the same, which enable high-density recording and reproduction using near-field light in a practical-level optical information recording medium. SOLUTION: On a translucent substrate 1, a dielectric layer 2, a recording layer 3, a dielectric layer 4 for converting near-field light into propagation light, a near-field light generating layer 5 for generating near-field light, An optical information recording medium formed by sequentially forming a correction layer 6 (dielectric) and a protective layer 7 for adjusting the characteristics is used, and the near-field light generating layer 5 is formed from the light transmitting substrate 1 side of the optical information recording medium. To generate near-field light, convert the near-field light into propagation light via the dielectric layer 4, and irradiate the recording layer 3 from the side opposite to the incident light to form pits.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing method, and more particularly to an optical information recording method capable of performing high-density recording using near-field light.

[0002]

2. Description of the Related Art In recent years, an optical information recording medium has been required to have a further increased storage capacity, and accordingly, an increase in the density of the optical information recording medium has been studied.

In order to improve the recording density of an optical information recording medium, it is essential to reduce the size of a recording pit. The size of the recording pit basically depends on the wavelength of a laser beam to be used and the numerical aperture of an objective lens. NA).

[0004] Therefore, conventionally, the two directions of increasing the density have been focused on (1) shortening the wavelength of the laser and (2) increasing the numerical aperture (NA) of the objective lens. .

However, there is a limit in increasing the density of an optical information recording medium by these methods, and a new method has been desired in order to further increase the capacity.

Therefore, an optical recording technique using near-field light has recently attracted attention.

In general, near-field light does not propagate like ordinary light, but is localized so as to cling to the vicinity of the medium surface.

Therefore, the spatial distribution is in accordance with the shape and dimensions of the medium.
It becomes possible to form a near-field light spot having a fine spatial distribution beyond the restriction by the wavelength.

On the basis of this principle, a scanning near-field optical microscope (SNO) which uses a fine needle probe as a near-field light generating element and aims at obtaining a resolution below the diffraction limit of light.
M: Scanning Near-Field Optical Microscope) has been developed for several years.

Recently, an experiment on the principle of optical recording using the SNOM technique has been performed, and it is possible to record a very small pit on the order of nanometers corresponding to the geometric size of the tip opening of the probe. It has been shown that ultra-high-density recording, which greatly exceeds the limitations of current optical recording technology, is possible.

[0011]

However, since the propagation distance of the near-field light is very short, about 50 nm, the distance between the optical information recording medium rotating at a high speed and the tip of the probe is fixed (~).
It is difficult to control the optical information recording medium at several tens of nanometers), causing problems such as the contact between the probe and the optical information recording medium and the destruction of the recorded data. It was difficult to apply this technology.

In addition, the process of processing the tip of the probe on the order of several tens of nanometers is complicated and unsuitable for mass production.

It is therefore an object of the present invention to provide an optical information recording medium and an optical information recording method for enabling high-density recording and reproduction using near-field light on a practical level optical information recording medium. .

[0014]

In order to achieve the above object, an optical information recording medium according to the present invention comprises a near-field light generating layer for generating near-field light by irradiating a laser beam; And a recording layer formed on the irradiation side of the laser light and recording by the near-field light.

Further, a dielectric layer for propagating the near-field light generated in the near-field light generating layer in a direction opposite to the irradiation direction of the laser light is provided between the near-field light generating layer and the recording layer. Preferably, it is formed.

The dielectric layer for propagating the near-field light is not always necessary when the near-field light generating layer is formed of an organic dye, for example. It may be determined according to the material forming the field light generating layer.

The recording layer responds to the laser light by changing its optical characteristics irreversibly or reversibly by the near-field light or the near-field light converted into the propagation light by the dielectric layer. Recording of the information to be performed.

Further, when a buffer layer is formed between the near-field light generating layer and the recording layer or between the dielectric layer and the recording layer, the recording layer has improved overwrite resistance.

Further, by forming a correction layer made of a dielectric on the side of the near-field light generating layer opposite to the side irradiated with the laser light, it is easy to adjust characteristics by transmitted light.

Further, the optical information recording medium of the present invention has a light-transmitting substrate, a first dielectric layer formed on the light-transmitting substrate, and a light-transmitting substrate formed on the first dielectric layer. A recording layer; a second dielectric layer formed on the recording layer;
And a near-field light generating layer formed on the dielectric layer of the second substrate. The near-field light generated in the near-field light generating layer by the laser light irradiated from the light-transmitting substrate side is transmitted to the second field. The information is recorded on the recording layer by the propagating light in accordance with the laser beam by the propagating light.

The recording layer records information corresponding to the laser light by changing its optical characteristics irreversibly or reversibly by near-field light propagating through the dielectric layer. And

Further, by forming a buffer layer at least between the first dielectric layer and the recording layer or between the recording layer and the second dielectric layer, Overwrite resistance is improved.

Further, by forming a correction layer made of a dielectric on the side of the near-field light generating layer opposite to the second dielectric layer, it is easy to adjust the characteristics by transmitted light.

In the optical information recording method of the present invention, the near-field light generating layer is irradiated with light via the recording layer.
Near-field light is generated from the near-field light generating layer, and information is recorded by changing the optical characteristics of the recording layer with the near-field light, or the near-field light is transmitted through a recording layer and a dielectric layer. By irradiating the generation layer with light, near-field light is generated from the near-field light generation layer, and the near-field light generated from the near-field light generation layer is propagated to the recording layer side by the dielectric layer. The information is recorded by converting the light into light and changing the optical characteristics of the recording layer with the propagating light converted by the dielectric layer.

The light applied to the near-field light generating layer through the recording layer is controlled to an intensity that does not change the optical characteristics of the recording layer.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an optical information recording medium and an optical information recording method according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of an optical information recording medium according to the present invention.

In FIG. 1, the optical information recording medium comprises a light-transmitting substrate 1, a recording layer 3, an excitation layer 5, a correction layer 6, a protective layer 7, and dielectric layers 2, 4.

The translucent substrate 1 has high transparency, heat resistance,
It is formed using a material having excellent moisture resistance and impact resistance. Specifically, polycarbonate, acrylic, or the like can be used, but is not limited thereto.

A pre-groove for controlling the position of the laser head is formed on the translucent substrate 1 as necessary at an appropriate depth and width.

A dielectric layer 2 is formed on the surface of such a translucent substrate 1, and a recording layer 3 is formed on the surface of the dielectric layer 2.

The dielectric layer 2 is made of, for example, ZnS-SiO
2, formed of Si3N4 or the like.

The recording layer 3 is made of a material whose optical characteristics change in response to light or heat. Specifically, for example, a GeSbTe alloy, an AgInSbTe alloy, or the like, which is a phase change material whose optical characteristics change reversibly, is used. A film is formed using a target obtained by alloying these, or several units are formed. It can be manufactured by forming a film separately.

Further, in order to use these alloys as the recording layer, a so-called as-deposited state immediately after the film formation may be used as it is, but before the recording, the film is formed on the translucent substrate 1. After that, once the phase is stabilized by changing the as-deposited state from a large random state to a crystalline state by light or heat, the temperature is raised again to the melting point or higher of the film by laser light or overheating, and this is performed at an ultra-high speed. It is effective to use a material that has been brought into an amorphous state by cooling at a low temperature.

On the recording layer 3, a dielectric layer 4 is formed.

The dielectric layer 4 is made of ZnS similarly to the dielectric layer 2.
-Formed of SiO2, Si3N4, etc., and has a function of converting near-field light generated on the surface of the excitation layer 5 into propagation light, as described later.

The excitation layer 5 is formed on the surface of the dielectric layer 4, and specific materials include Sb, Ag, Al, Au,
A material that generates near-field light when irradiated with light, such as Si, Ge, Mo2S, InSb, or an organic dye, is used.

Normally, near-field light generated from the surface of the excitation layer 5 opposite to the side on which the laser light is incident is used. By appropriately controlling the thickness of the excitation layer 5, the laser light Near-field light generated on the surface on the incident side of the light source can also be used.

Therefore, in the optical information recording medium of the present invention, the near-field light generated on the incident light side surface of the excitation layer 5 having an appropriate thickness is propagated through the dielectric layer 4. It is characterized in that the light is converted into light, and recording on the recording layer 3 is performed by this propagated light.

That is, the excitation layer 5 is formed behind the recording layer 3 with respect to the incident light, and near-field light generated on the surface of the excitation layer 5 on the incident light side is recorded via the dielectric layer 4. The recording is returned to the layer 3 and recording on the recording layer 3 is performed.

Further, a correction layer 6 for adjusting characteristics described later is formed on the excitation layer 5.

The correction layer 6 is made of the same material as the dielectric layer 2, and a protective layer 7 is formed on the surface of the correction layer 6.

The same material as that of the light-transmitting substrate 1 is used for the protective layer 7.

By configuring the optical information recording medium in this way, it is possible for the constituent films of the optical information recording medium to exhibit the same function as the probe in the SNOM in a self-forming manner.

FIG. 2 is a diagram showing a case where a buffer layer 8a is provided between the dielectric layer 2 and the recording layer 3 in the optical information recording medium having the above configuration. FIG. 4 is a diagram showing a case where a buffer layer 8b is provided between a recording layer 3 and a dielectric layer 4.

FIG. 4 shows a case where buffer layers 8a and 8b are provided on both surfaces of the recording layer 3. As shown in these figures, by providing a buffer layer on the surface of the recording layer 3, The overwrite characteristics of the optical information recording medium are improved.

The buffer layers 8a and 8b are made of GeN or the like.

Now, as shown in FIG. 1, the incident laser light is applied to the light transmitting substrate 1 of the optical information recording medium having the above structure.
Irradiated from the side. The incident laser light is a normal DVD-R
By using an optical head similar to that used in AM and the like, light is condensed on the interface between the excitation layer 5 and the dielectric layer 3 to form a spot.

The output of the incident laser light is controlled so as not to change the optical characteristics of the recording layer 3 when passing through the recording layer 3.

That is, for example, when a phase change recording material is used for the recording layer 3, the output of the laser beam is controlled so that the energy for giving the melting point Tm and the crystal dislocation point Tc of the phase change recording material is not supplied to the recording layer 3. Controlled.

The near-field light generated at the spot formed by the incident laser light on the excitation layer 5 is converted into propagation light by the dielectric layer 3 and irradiates the recording layer 2 from the opposite side of the incident laser light.

The recording layer 2 includes an incident laser beam and a dielectric layer 3.
A pit is formed by a synergistic effect with the near-field light propagating through the pit, and information is recorded.

According to such a method, it is not necessary to use a probe, and it is possible to solve a problem that hinders high-speed rotation, such as controlling the distance between the probe and the optical information recording medium.

Further, it is not necessary to largely change the structure of the optical system or the optical information recording medium of the conventional optical information recording apparatus, which is extremely practical.

As shown in FIG. 5, the near-field light generated on the surface of the excitation layer 5 on the side of the correction layer 6 is converted into propagation light via the correction layer 6 made of a dielectric, and , The output of the laser beam emitted from the optical pickup 93 can be adjusted, so that the recording layer 3 is formed by the near-field light generated on the surface of the excitation layer 5 on the dielectric layer 4 side. The accuracy of the pit can be improved.

[0056]

As described above, according to the present invention, since the constituent film of the optical information recording medium exhibits the same function as the probe in the SNOM in a self-forming manner, it is not necessary to use a probe. High-density recording using near-field light enables practical-level optical information recording because near-field recording is possible without the need to significantly change the optical system and optical information recording medium structure of conventional optical information recording devices. It is possible in the medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the configuration of an optical information recording medium and an example of an optical information recording method according to the present invention.

FIG. 2 is a diagram showing an example of the configuration of an optical concession recording medium according to the present invention.

FIG. 3 is a diagram showing an example of the configuration of the optical concession recording medium according to the present invention.

FIG. 4 is a diagram showing an example of the configuration of an optical concession recording medium according to the present invention.

FIG. 5 is a diagram showing an example of the optical concession recording method according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 translucent substrate 2 dielectric layer 3 recording layer 4 dielectric layer 5 near-field light generating layer 6 correction layer 7 protective layer 91 photodetector 92 LD driver 93 optical pickup

Claims (15)

[Claims] 1. A near-field light generating layer for generating near-field light by irradiating a laser beam, and a recording formed on the near-field light-generating layer on a side of the near-field light irradiating the laser beam, wherein recording is performed by the near-field light. An optical information recording medium, comprising: 2. A dielectric formed between the near-field light generating layer and the recording layer, for transmitting near-field light generated in the near-field light generating layer in a direction opposite to a direction in which the laser light is irradiated. The optical information recording medium according to claim 1, further comprising a body layer. 3. The optical information recording apparatus according to claim 1, wherein the recording layer records information corresponding to the laser beam by irreversibly changing an optical characteristic of the recording layer by the near-field light. Medium. 4. The optical information recording medium according to claim 1, wherein the recording layer records information corresponding to the laser light by reversibly changing its optical characteristics by the near-field light. . 5. The optical information recording medium according to claim 1, wherein a buffer layer is formed between the near-field light generating layer and the recording layer. 6. The optical information recording medium according to claim 2, wherein a buffer layer is formed between said dielectric layer and said recording layer. 7. The optical information recording medium according to claim 1, wherein a correction layer made of a dielectric is formed on a side of the near-field light generating layer opposite to a side irradiated with the laser beam. 8. A light-transmitting substrate, a first dielectric layer formed on the light-transmitting substrate, a recording layer formed on the first dielectric layer, and And a near-field light generating layer formed on the second dielectric layer, wherein the near-field light generating layer is formed by a laser beam irradiated from the light-transmitting substrate side. The near-field light generated in the field light generating layer is converted into propagating light by the second dielectric layer, and information is recorded on the recording layer by the propagating light in accordance with the laser light. Optical information recording medium. 9. The information recording apparatus according to claim 1, wherein the recording layer records information corresponding to the laser light by changing its optical characteristics irreversibly by near-field light propagating through the dielectric layer. 8. The optical information recording medium according to item 8. 10. The information recording apparatus according to claim 8, wherein the recording layer records information corresponding to the laser light by reversibly changing its optical characteristics by near-field light propagating through the dielectric layer. The optical information recording medium according to the above. 11. A buffer layer is formed between at least one of the first dielectric layer and the recording layer or between the recording layer and the second dielectric layer. 8. The optical information recording medium according to item 8. 12. The optical information recording medium according to claim 8, wherein a correction layer made of a dielectric is formed on a side of said near-field light generating layer opposite to said second dielectric layer. 13. The near-field light generating layer is irradiated with light through the recording layer to generate near-field light from the near-field light generating layer, and the near-field light changes the optical characteristics of the recording layer. An optical information recording method characterized in that information is recorded while being changed. 14. A near-field light generating layer is irradiated with light through a recording layer and a dielectric layer to generate near-field light from the near-field light generating layer, and is generated from the near-field light generating layer. Converting near-field light into propagating light propagating to the recording layer side by the dielectric layer, and recording information by changing optical characteristics of the recording layer by the propagating light converted by the dielectric layer. An optical information recording method comprising: 15. The method according to claim 13, wherein the light irradiated to the near-field light generating layer via the recording layer is controlled to an intensity that does not change the optical characteristics of the recording layer. Optical information recording method.