KR100571908B1 - Optical disk for near field recording/reproducing - Google Patents

Abstract

The near field optical recording and reproducing apparatus includes a light source, an objective lens for focusing light emitted from the light source, a light receiving part for receiving light reflected from the optical disk, and a light receiving lens for focusing incident light on the light receiving part. A near field recording / reproducing optical disc is disclosed.

The disclosed nearfield recording / reproducing optical disc includes a protective film having a thickness X, a first dielectric film, a recording film on which a nearfield is formed, a second dielectric film, a reflecting film and sequentially arranged from the side from which light L is incident. And a substrate, wherein the thickness X of the protective film satisfies the following equation.

Equation

Where NAO is the numerical aperture of the light receiving lens for photodetection,

          NA is the numerical aperture of the objective lens,

          h: radius of the signal beam received by the light receiving unit,

          k: Radius (H) of the light-receiving part beam reflected from the protective film and the radius of the signal beam

                (h) is the magnification (k = H / h).

Description

Optical disk for near field recording / reproducing

1 is a schematic diagram showing a general near field optical recording and reproducing apparatus.

2 is a schematic view showing an optical arrangement of a general near field optical recording and reproducing apparatus.

Fig. 3 is a schematic diagram showing a conventional nearfield recording / reproducing optical disc.

Fig. 4 is a diagram showing the optical arrangement of the nearfield optical recording / reproducing apparatus showing NA, NA0, H, h necessary for explaining the nearfield recording / reproducing optical disc of the present invention.

Fig. 5 is a schematic diagram showing an optical disc for nearfield recording / reproducing according to an embodiment of the present invention.

Fig. 6 is a schematic diagram showing an optical disc for nearfield recording / reproducing according to another embodiment of the present invention.

<Description of Symbols for Major Parts of Drawings>

51 ... light source 53 ... lens element 55 ... light receiving lens

57.Receiver 100 ... Optical disk 111 ... Protective shield

113 First dielectric film 115 Recording film 117 Second dielectric film

119 ... Reflective film 121 ... Substrate 130 ... Lubrication film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc for near field recording / reproducing, and more particularly, to a near field recording in which the structure is improved to suppress fluctuations in the amount of surface reflection light generated by the height of the lens mounted on the slider. And an optical disc for reproduction.

In general, nearfield refers to a technique for performing data recording and reproducing in a state in which the distance between the optical element and the optical disk disposed in proximity to the optical disk is about 20 to 300 nm.

1 and 2, a general near field optical recording and reproducing apparatus includes a swing arm 21 installed to reciprocally rotate with respect to a base, and an actuator 23 for providing a rotation driving force to the swing arm 21; And a slider 25 provided at the end of the swing arm 21 so that the track of the optical disk 10 can be scanned while being lifted against the optical disk 10 by pneumatic pressure, and mounted on the slider 25 and optically mounted. And an optical head 30 having an optical element 31 for forming an optical spot on the optical disc 10 so as to reproduce information. Here, the optical disk includes a phase change type optical disk and an optical magnetic disk. When the optical magnetic disk is employed as the optical disk, the optical head 30 further includes a coil 35 for magnetic field modulation.

The optical element 31 includes a reflective mirror 32, an objective lens 33, and a small lens 34 made of a solid immersion lens (SIL) or a solid immersion mirror (SIM). It is configured to include.

2 illustrates an apparatus employing a refractive-type solid-impregnated lens as the small lens 34, and the small lens 34 is configured to focus light irradiated from the transmitting and receiving part 40 onto the optical disk 10 at a large incident angle. do. As a result, the size of the light spot formed on the optical disc 10 can be reduced.

The transmitter / receiver 40 irradiates laser light having a diameter suitable for the objective lens 33, and the reflection mirror 32 reflects the light incident from the transmitter / receiver 40 toward the objective lens 33. The objective lens 33 focuses incident light onto the small lens 34, and the small lens 34 forms a near field on the optical disc 10.

The slider 25 is biased in the direction in which the suspension 26 is in contact with the optical disc 10. The slider 25 floats from the optical disc 10 by its buoyancy when the optical disc 10 starts to rotate. At this time, the air gap G between the optical element 34 and the optical disc 10 is formed. This is a close interval of about 20 to 300 nm.

Here, when the distance between the air gap (G) is greater than the wavelength of the light irradiated from the light receiving section 40, the optical disk is located in the area away from the near field, the light having a large numerical aperture by the law of refraction and total reflection Since it is totally reflected at the light exit surface of the small lens 34, it does not contribute to forming the light spot on the optical disk 10. On the other hand, when the air gap G is smaller than the wavelength of the use light, the size of the light spot formed on the optical disc 10 is close to the desired light spot size.

The conventional optical disc employed as the medium of the nearfield recording / reproducing optical recording / reproducing apparatus having such a configuration includes a substrate 11, a reflective film 12 sequentially stacked on the substrate, It consists of one dielectric film 13, recording film 14, second dielectric film 15, and protective film 16. Here, light focused through the optical element 31 passes through the passivation layer 16 and the second dielectric layer 15 to form a near field in the recording layer 14, and the recording layer 14 The reflected light is transmitted to the optical element 31 through the second dielectric film 15 and the passivation film 16 again.

The optical disc 10 has a track pitch of 0.3 to 0.4 µm, a V shape, and a groove G having a depth of 0.15 to 0.3 µm. Here, the thicknesses of the reflective film 12, the first dielectric film 13, the recording film 14, the second dielectric film 15, and the protective film 16 are expressed by Equation (1).

As described above, the configured optical disc 10 is bent so that the upper shape of the portion where the groove G is formed corresponds to the shape of the groove G. As shown in FIG. In addition, the upper surface of the protective film corresponding to the surface of the optical disk has a curve corresponding to the shape of the groove (G).

Therefore, when the high refractive index small lens 34 having a refractive index of 1.65 is focused on the optical disc 1 through the air gap G, the amount of surface reflection light generated according to the height of the floating of the optical element 31 is concentrated. There is a problem in that the signal characteristic is deteriorated because the noise light focused on the fluctuation and the light receiving unit and the desired signal light are mixed.

The present invention has been made in view of the above-mentioned, the near field recording / structure is improved to control the thickness of the protective layer to suppress the variation in the amount of surface reflection light generated according to the height of the rise of the optical element constituting the near-field optical system It is an object to provide an optical disc for reproduction.

The present invention for achieving the above object, the near field including a light source, a lens element for focusing the light irradiated from the light source, a light receiving unit for receiving the light reflected from the optical disk, and a light receiving lens for focusing the incident light to the light receiving unit In the nearfield recording / reproducing optical disc recorded and reproduced by the optical recording / reproducing apparatus, a protective film having a thickness X, a first dielectric film, and a nearfield, which are sequentially arranged from the side from which light L is incident, are formed. And a recording film, a second dielectric film, a reflecting film, and a substrate, wherein the thickness X of the protective film satisfies the following equation.

Equation

Where NAO is the numerical aperture of the light receiving lens for photodetection,

          NA is the numerical aperture of the lens element,

          h: radius of the signal beam received by the light receiving unit,

          k: Radius (H) of the light-receiving part beam reflected from the protective film and the radius of the signal beam

                (h) is the magnification (k = H / h).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The nearfield recording / reproducing optical disc according to the embodiment of the present invention is employed in the nearfield optical recording / reproducing apparatus having the optical configuration as shown in FIG.

Referring to Fig. 4, the near field optical recording and reproducing apparatus receives a light source 51, a lens element 53 for condensing light emitted from the light source 51, and a light reflected from the optical disc 100. A light receiving unit 57 and a light receiving lens 55 for focusing incident light onto the light receiving unit 57 are included. Here, the lens element 53 includes the objective lens (33 in FIG. 2) and the small lens 34 described with reference to FIG. 2, and has a numerical aperture NA. The lens element 53 floats with respect to the optical disc 100 by a predetermined air gap due to pneumatic pressure during recording and reproduction of information. The light receiving lens 55 has a numerical aperture NAO, and focuses incident parallel light to form a light spot on the light receiving unit 57. Herein, the light reflected by the recording film of the optical disc 100 has the radius h among the light received by the light receiving part 57, and the light reflected by the protective film 111 of the optical disc 100 has the radius H.

Referring to FIG. 5, an optical disk according to an exemplary embodiment of the present invention has a protective film 111 having a thickness X sequentially stacked on a surface opposite to the lens element 53 of FIG. 4, that is, the light L is incident. And a first dielectric film 113, a recording film 115 on which a near field is formed, a second dielectric film 117, a reflective film 119, and a substrate 121. As shown in FIG. The optical disc 100 is manufactured in the order of the substrate 121, the reflective film 119, the second dielectric film 117, the recording film 115, the first dielectric film 113, and the protective film 111. .

The substrate 121 is made of glass, polycarbonate (PC), polymethyl methacrylate (PMMA), an acrylate-based material, and the like. On the substrate 121, a track pitch (TP) satisfying Equation 2 below is provided. ), Grooves G are formed.

와 상기 보호막(111)의 두께에 의해 결정된다. Here, the track pitch and groove (G) is produced by the injection, 2P (photopolymer) method. Therefore, the optical groove depth is the depth of the grooves physically introduced on the substrate 121.

And the thickness of the protective film 111.

의 증가 없이, 보호막(111)의 두께 결정에 의하여 광학적 그루브 깊이를 증가시킬 수 있어서, 그루브 형성이 용이하다.Thus, the physical depth of the groove

Without increasing, the optical groove depth can be increased by determining the thickness of the protective film 111, so that groove formation is easy.

The reflective film 119 is formed on the substrate 121 on which the tracks and grooves are formed as described above, and includes aluminum (Al), nickel (Ni), copper (Cu), platinum (Pt), silver (Ag), and the like. And metals such as gold (Au).

화합물 또는

재질로 구성된다.Each of the first and second dielectric layers 113 and 117

Compound or

It is made of material.

The recording film 115 is made of a magneto-optical material or a phase change material, and the type of the optical disc is determined according to the selected material.

및,

등으로 구성된 광자기 재질을 선택한 경우는 광자기형 디스크가 되며, 상기 기록막(115)으로

등으로 구성된 상변화 재질을 선택한 경우는 상변화형 광디스크가 된다.That is, to the recording film 115

And,

In the case of selecting a magneto-optical material composed of a light source or the like, it becomes a magneto-optical disk, and the recording film 115

In the case of selecting a phase change material composed of a light source, a phase change type optical disc is used.

Here, the thicknesses of the first dielectric film 113, the recording film 115, the second dielectric film 117, and the reflective film 119 preferably satisfy the following equation (3).

로 구성된 무기물 중에서 선택된 어느 하나의 재질 또는 아크릴레이트계 또는 포토폴리머 레진으로 구성된 유기물 중에서 선택된 어느 하나의 재질로 된다.The passivation layer 111 is made of an inorganic material or an organic material. The protective layer 111 is formed of amorphous DLC, SiN and

It is made of any one material selected from inorganic materials consisting of or an organic material consisting of an acrylate-based or photopolymer resin.

When the inorganic material is selected as the passivation layer 111, it is formed through a sputtering method or an evaporation method. On the other hand, when the organic material is selected, it is formed through a spin coating method, 2P method, etc., the material properties, that is, the refractive index and the viscosity (Viscosity) of each of the protective film 111 preferably satisfy the equation (4).

In the shrinkage rate, the protective film made of the organic material may have a shrinkage rate of 7% or less.

The passivation layer 111 should be determined so that the amount of light reflected from the mirror surface of the small lens among the incident light is minimized. To this end, the thickness X of the protective film 111 is determined in a range satisfying Equation 5 below.

Here, each of NAO, NA, and h is as described with reference to FIG. 4, where k is a magnification of the radius H of the light-receiving part beam reflected from the protective film 111 and the radius h of the signal beam (k = H / h). It is shown.

More preferably, the thickness X of the protective film 111 satisfies Equation 6.

Based on Equation 5, an example of setting the protective layer thickness X is shown in Table 1.

Optical system Example 1 Example 2 NAO 0.05 0.1 NA 1.65 1.65 k 10 10 h [μm] 50 2 X [μm] 8.3 0.7

Referring to FIG. 6, the optical disk according to the present invention may further include a lubricating film 130 formed on the protective film 111 coated with a thickness of 1 to 3 nm.

As the lubricating film 130, lubricants such as Foblin Z Dol and Foblin 2001, and a mixed solvent, Galdel SV, may be used.

By coating the lubricating film 130 in this manner, the slider of the optical recording / reproducing apparatus can be smoothly moved during initial contact movement.

In the nearfield recording / reproducing optical disc according to the present invention configured as described above, the nearfield optical system is designed by designing the thickness of the optical disc protective film such that the size of the light receiving portion beam reflected by the protective film is k times the size of the signal beam reflected from the recording film. Fluctuation of the amount of surface reflection light generated according to the height of the float of the optical element constituting the is to be suppressed.

In addition, by adjusting the groove depth and filling the space in the groove with the groove protective layer, the optical depth of the deep groove can be increased by the high refractive index groove protective layer while the groove depth is shallow, thereby increasing the track signal. It facilitates the fabrication of high density optical discs.

Claims (9)

The near field optical recording and reproducing apparatus includes a light source, an objective lens for focusing light emitted from the light source, a light receiving part for receiving light reflected from the optical disk, and a light receiving lens for focusing incident light on the light receiving part. In the near field recording / reproducing optical disc, Disposed sequentially from the side from which light L is incident, A protective film having a thickness X, a first dielectric film, a recording film on which a near field is formed, a second dielectric film, a reflective film, and a substrate, And the thickness X of the protective film satisfies the following equation. Equation

Where NAO is the numerical aperture of the light receiving lens for photodetection,           NA is the numerical aperture of the objective lens,           h: radius of the signal beam received by the light receiving unit,           k: Radius (H) of the light-receiving part beam reflected from the protective film and the radius of the signal beam                 (h) is the magnification (k = H / h). The method of claim 1, wherein the protective film, Amorphous DLC, SiN and

The near-field recording / reproducing optical disc, characterized in that made of any one material selected from inorganic matter. The method of claim 1, wherein the protective film, An near field recording / reproducing optical disc, characterized in that it is made of any one material selected from organic materials composed of acrylate-based or photopolymer resins. 4. The near field recording / reproducing optical disc of claim 3, wherein each of the refractive index and the viscosity of the protective film satisfies the following conditional expression. <Conditional expression>

The method of claim 1, Each of the first and second dielectric films

Compound or

Material, The recording film

It is a magneto-optical material made of any one material selected from magneto-optical materials composed of The reflective film

An optical disc for nearfield recording / reproducing, characterized in that the material is made of any one selected from metals. The method of claim 1, Each of the first and second dielectric films

Compound or

Material, The recording film

It is made of any one material selected from phase change material consisting of The reflective film

An optical disc for nearfield recording / reproducing, characterized in that the material is made of any one selected from metals. The method of claim 1, The thickness of the first dielectric film, the recording film, the second dielectric film, and the reflective film satisfies the following equation, wherein the near field recording / reproducing optical disc. Equation

The near field recording / reproducing optical disc according to claim 1, further comprising a lubricating film formed on the protective film in a thickness of 1 to 3 nm. The method according to any one of claims 1 to 8, A near pitch recording / reproducing optical disc, wherein a track pitch (TP) and a groove are formed on the substrate. <Conditional expression>

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