JPH0540965A - Optical information recording medium - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize an optical information recording medium that does not cause tracking failure even when a laser light source for recording / reproducing optical information having a different oscillation wavelength is used. A tracking guide groove G is formed in a parallel, concentric or spiral shape, and a groove PL is intermittently formed in a part of an information track L set as an intermediate area between adjacent guide grooves in a direction orthogonal to the guide groove. The transparent substrate 10A on which the pre-format is formed is provided with a light-absorbing / reflective recording film 10B on the same surface on which the grooves G and PL are formed, and the refractive index of the transparent substrate 10A is N, The wavelengths of n (> 1) types of recording / reproducing laser light are λ ₁ , λ ₂ ,. ． ． When the lambda _n, where lambda ₁ the smallest among these wavelengths, the largest ones and lambda _n, the effective depth of the guide groove: a _{D eff, 0.075λ n / N ≦} D eff ≦ 0. The effective depth of the groove of the preformat: d _eff is set in the range of 2λ ₁ / N and the range of 0.26λ _n / N ≦ d _eff ≦ 0.45λ ₁ / N.

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 medium.

[0002]

2. Description of the Related Art A guide groove for tracking is formed in a parallel, concentric or spiral shape, and a part of an information track set as an intermediate area between adjacent guide grooves in a direction orthogonal to the guide groove is interrupted by the groove. There is known an optical information recording medium in which a light absorbing and reflecting recording film is provided on the surface of the transparent substrate on which the preformat is formed, on the same side as the groove is formed on.

The outline of the optical information recording medium will be described with reference to FIG. In FIG. 1A, reference numeral 10
Shows a part of the optical information recording medium in a sectional view.
A guide groove G for tracking is formed on one surface of the transparent substrate indicated by reference numeral 10A in a parallel, concentric, or spiral shape. Direction orthogonal to the guide groove G (see FIG. 1
The intermediate section L between the adjacent guide grooves in (a) in the left-right direction) is an information track called a land.

On this information track L, address information and the like are formed as a pre-format. In FIG. 1A, the symbol PL indicates a groove forming the preformat. That is, the preformat is formed by connecting and disconnecting the groove PL. The transparent substrate 10A is, for example, a PMMA plate,
The grooves G and PL are formed by transferring from a stamper by a photopolymer method, for example.

On the surface of the transparent substrate 10A on the side where the grooves G and PL are formed, a light absorbing / reflecting recording film 10B is formed. The recording film 10B is formed of a light absorbing / reflecting dye having a structural formula as shown in FIG. 1C, for example, by a spinner so as to have an average thickness of 650Å. When this recording film is irradiated with light, minute holes are formed in the light-irradiated portion, or a phase change with different reflectance occurs. Optical information can be recorded as such small holes or phase changes with different reflectances.

FIG. 2 shows such an optical information recording medium 1
00 shows the state in which the optical information recorded in 00 is read out. The recording / reproducing laser beam H is reflected by the polarization prism 50, enters the objective lens 70 through the quarter-wave plate 60, and is converged by the action of the objective lens 70 while the optical information recording medium 100 is provided on the transparent substrate side. Is incident on the recording film and condensed on the recording film.

The reflected light from the recording film travels backward through the objective lens 70 and the quarter-wave plate 60, passes through the polarizing prism 50, and enters the light-receiving surfaces 80A and 80B of the two-divided light-receiving element. Photoelectric conversion outputs A and B are output from the light receiving surfaces 80A and 80B, respectively, and these are input to analog adders 90A and subtractors 90B, respectively.

The adder 90A obtains an output: (A + B) corresponding to the reproduction signal: RF, the subtractor 90B obtains a tracking error signal: (AB), and the tracking error signal is set to 0. By performing the servo control so that the light spot by the objective lens 70 is
Be able to follow the information track correctly.

Now, at the stage of making an optical information recording medium, it is unavoidable that minute deformation such as "warp" occurs on the transparent substrate, and when recording / reproducing optical information,
The recording film surface is relatively inclined with respect to the optical axis of the optical pickup,
The so-called "tilt" inevitably occurs. This tilt is likely to cause tracking failure especially in the preformat forming unit in combination with a tracking servo error.

The inventor has previously stated, "By setting the depth of the guide groove / preformatting groove in accordance with the wavelength of the recording / reproducing laser beam used for recording / reproducing optical information,
A method for effectively preventing the above tracking failure has been proposed (Japanese Patent Laid-Open No. 63-32746).

By the way, in recent years, the oscillation wavelength of a semiconductor laser used as a light source for a laser beam for recording / reproducing optical information has been shortened, and accordingly, semiconductor lasers having various oscillation wavelengths have been put into practical use. In this way, when the oscillation wavelength of the semiconductor laser as the light source becomes multiple types,
Even if the tracking failure is prevented by the above method with respect to the recording / reproducing laser beam of a certain specific wavelength, the tracking failure may occur with the recording / reproducing laser beam of another oscillation wavelength. A practically very serious problem occurs that compatibility with the reproduction laser light wavelength is impaired.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical information recording medium which effectively solves the above problems.

[0013]

As shown in FIGS. 1 (a) and 1 (b), the optical information recording medium of the present invention has a "guide groove G for tracking formed in parallel, concentric or spiral shape. Then, the grooves G and PL of the transparent substrate 10 in which the preformat is formed by the interruption of the groove PL are formed in a part of the information track L set as an intermediate area between the adjacent guide grooves in the guide groove orthogonal direction. On the same side as
A recording film 10B having a light absorbing and reflecting property is provided ".
The medium is characterized by the following points.

That is, the refractive index of the transparent substrate 10 is N, n (>
1) The wavelengths of the recording / reproducing laser light (in vacuum) of λ ₁ , λ ₂ ,. ． ． Let λ _n be the minimum wavelength of these wavelengths be λ ₁ and the maximum wavelength be λ _n.
Effective depth: D _eff is set in the range of 0.075λ _n / N ≤ D _eff ≤ 0.2 λ ₁ / N, and the effective depth of the pre-formatted groove PL: d _eff is 0.26 λ _n / It is set in the range of N ≦ d _eff ≦ 0.45λ ₁ / N.

The "effective depth" means a groove G'having a V-shaped cross section (the transparent substrate 11A at the time of forming the groove, as in the optical information recording medium 10 'illustrated in FIG. 1B). (Caused by the sagging of the material), "the groove depth corrected for the influence of the groove cross-sectional shape", and in the case of a V-shaped groove, it is 1 / 1.4 of the peak depth of the groove. Is. This also applies when the cross-sectional shape of the groove PL is V-shaped.

The plurality of types of recording / reproducing laser light are, for example, wavelengths: 830 nm, 780 nm, 680 n.
m or 650 nm laser light, two or more kinds of laser light selected (claim 2), for example, wavelength: 780
nm and wavelength: 680 nm can be used. The above wavelength is a median value including the standard of variation of the oscillation wavelength of the semiconductor laser: ± 20 nm.

[0017]

In the "tracking failure prevention method" proposed in Japanese Patent Laid-Open No. 63-32746, the effective depth of the guide groove G: D _eff against the wavelength: λ ₀ of the recording / reproducing laser beam in the transparent substrate. , the effective depth of the groove PL preformat: the d _eff each _{0.075λ 0 ≦ D eff ≦ 0.2λ 0} (1) 0.25λ 0 ≦ d eff ≦ 0.45λ 0 ( preferably, 0.25 [lambda ₀ ≦ d _eff ≦ 0.38λ ₀ ) (2) The above range is established as it is even if the wavelength: λ ₀ is different.

When the refractive index of the transparent substrate is N and the wavelength of the recording / reproducing laser light in vacuum is: λ, the wavelength: λ ₀ in the transparent substrate is "λ / N". In order for the optical information recording medium to be compatible with the recording / reproducing laser light of a plurality of wavelengths (the tracking failure does not occur even if a light source having a different oscillation wavelength is used) It suffices if the above conditional expressions (1) and (2) are satisfied for each individual laser beam for use.

Therefore, the wavelengths of the plural kinds of recording / reproducing laser beams are λ ₁ , λ ₂ ,. ． ． Let λ _n be the minimum wavelength of these wavelengths be λ ₁ and the maximum wavelength be λ _n , (1) (2)
In order to satisfy the condition of, the effective depth of the guide groove G: D
_eff is in the range of 0.075λ _n / N ≦ D _eff ≦ 0.2λ ₁ / N, and the effective depth of the groove PL of the preformat is:
d _eff is 0.26λ _n / N ≦ d _eff ≦ 0.45λ ₁ / N
(Preferably 0.26λ _n / N ≦ d _eff ≦ 0.38λ ₁
/ N).

[0020]

[Example] PMMA having a refractive index of N = 1.5 as a transparent substrate
Oscillation wavelength: λ ₂ = 780 nm (± 20 nm)
Semiconductor laser light source (first light source) and oscillation wavelength: λ
An example of forming an optical information recording medium compatible with a semiconductor laser light source (second light source) of ₁ = 680 nm (± 20 nm) will be described.

Considering the refractive index of the transparent substrate: 1.5,
The wavelengths of the laser light having the oscillation wavelengths of λ ₁ and λ ₂ in the transparent substrate are 780 / 1.5 and 680 / 1.5, respectively. Therefore, the range of the effective depth D _eff of the guide groove G is: 39 to 104 nm for the first light source and 34 to 91 nm for the second light source. Further, the range of the effective depth: d _eff of the groove PL of the preformat is 135 to 234 nm for the first light source, and 11 for the second light source.
8 to 204 nm.

Therefore, in order to realize an optical information recording medium compatible with the first and second light sources, 39 to 91n is required.
The guide groove G having an effective depth in the range of m is formed, and the groove PL of the preformat has an effective depth of 135 to 234.
The thickness may be in the range of nm (preferably 135 to 172 nm).

By changing the effective depths of the grooves G and PL within this range, plural kinds of optical information recording media (arrangement pitch of the guide grooves G: P is 1.2 μm to 2.4 μm, and is formed on the recording film). Although the diameter of the focused light spot is about 1 / e ² diameter), in both cases, in the recording / reproducing apparatus using the first and second light sources as the light source of the recording / reproducing laser beam, the tracking failure is caused. It was confirmed that it was not generated and was compatible with any optical pickup using the first and second light sources.

[0024]

As described above, according to the present invention, a novel optical information recording medium can be provided. Since this optical information recording medium is configured as described above, it is possible to record / reproduce optical information without causing tracking failure even if the wavelength of the light source used for recording / reproduction is different. ..

[Brief description of drawings]

FIG. 1 is a diagram for explaining the present invention.

FIG. 2 is a diagram for explaining recording / reproduction of optical information with respect to an optical information recording medium.

[Explanation of symbols]

 10 optical information recording medium 10A transparent substrate 10B recording film G guide groove PL groove forming pre-format

Claims (3)

[Claims] 1. A tracking guide groove is formed in a parallel or concentric circle shape or a spiral shape, and a part of an information track set as an intermediate area between adjacent guide grooves in a direction orthogonal to the guide groove is interrupted by the groove. On the surface of the same side where the groove was formed of the transparent substrate on which the preformat was formed,
A recording film having light absorption and reflection properties is provided, the transparent substrate has a refractive index of N, and the wavelengths of n (> 1) kinds of recording / reproducing laser light are λ ₁ , λ ₂ ,. ． , Lambda and _n, lambda ₁ the smallest among these wavelengths, when the maximum ones and lambda _n, the effective depth of the guide groove: D _{eff is, 0.075λ n / N ≦ D eff} ≦ 0 .2λ ₁ / N, and the effective depth of the preformat groove: d _eff is set to 0.26 λ _n / N ≦ d _eff ≦ 0.45λ ₁ / N. And an optical information recording medium. 2. The method according to claim 1, wherein a plurality of kinds of recording / reproducing laser light have a wavelength of 830 nm,
An optical information recording medium, which comprises two or more kinds of laser light selected from laser light of 780 nm, 680 nm, and 650 nm. 3. The optical information recording medium according to claim 2, wherein the plurality of types of recording / reproducing laser light have wavelengths of 780 nm and 680 nm.