JP2002324320A - Optical recording medium and its recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply obtain a high recorded contrast (modulation) for an optical recording medium that has recording layer on a plate having a pre-groove at least, and provide its recording method. SOLUTION: (1) This optical recording medium has a recording layer on a plate having a pre-groove at least, and forms a recorded section changing in width of the pre-groove by irradiating a laser beam, and is characterized in that the recorded section is formed by enlarging the width of the groove bottom against the opening width of the groove on the plate. (2) This recording method is a recording method on an optical recording medium having a recording layer on a plate having a pre-groove at least, and forms a recorded section changing in width of the pre-groove by irradiating a laser beam, and featured in that the recorded section is formed by enlarging the width of the groove bottom against the opening width of the groove on the plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical recording medium and a recording method thereof.

[0002]

2. Description of the Related Art Conventionally, optical recording media having an organic material as a recording layer, such as CD-R and DVD-R, have been put to practical use. In these optical recording media, for example, “SPIE Vol. 107
8 Optical Data Storage To
pical Meeting (1989) pp. 80-
87 "and" Jpn. J. Appl. Phys. Vol.
31 (1992) pp. 484-493 "describes that the recording portion is formed by expansion (bump) of the substrate, decomposition of the recording layer material, deformation of the reflective layer, and the like. Also, "J
pn. J. Appl. Phys. Vol. 36 (199
7) pp. 403-409 "includes the CNR of the reproduced signal.
(Carrier to noise ratio, carrier to noise
Noise ratio) is described as having a correlation with the expansion height and expansion width of the substrate bottom due to recording. Furthermore,
http: // search. zdnet. co. jp
/ Magazine / cshop / 0012 / sp3
(Computer Shopper Japan H
home page), as a recording principle of CD-R,
There is a description that the reflectance of light is reduced due to the deterioration of the dye and the material of the substrate. orangef
orum. or. jp / j / cdr / cdr mech
anisml. htm (CDs conforming to the Orange Book
-The official site of the Orange Forum, a corporate organization for disseminating the R / RW standard, states that the recording principle of CD-R is that recording pits are formed due to refractive index changes due to substrate deformation and dye decomposition. There is a description.

On the other hand, as a recording method of an optical recording medium,
"Optical disc technology, supervised by Morio Onoe, Radio Engineering, 31
As described in "page 5", recording methods such as a punching type, a phase change type, a bubble type, and a texture type have been proposed as recording methods for a write-once optical disc. Patent No. 2710
No. 040 discloses a recording method for obtaining a high degree of modulation in a CD-R optical disc, in which a bump (expanded portion) is formed on a substrate, a deteriorated portion of optical characteristics is formed on a recording layer, or a recording layer is formed. A method is described in which a void is formed at the interface between the recording layer and the reflective layer, fine bubbles are dispersed in the recording layer, or a deteriorated portion having optical characteristics is formed on the substrate. JP-A-8-7275 discloses that a laser beam is applied to an optical recording medium having a recording layer made of a shape memory resin provided directly or via a dielectric layer on a transparent substrate in the vicinity of the interface of the recording layer on the substrate side. There has been proposed a recording method in which a convex pit is formed by irradiating the shape memory resin so as to be focused and thermally expanding the shape memory resin.

[0004] Other known techniques similar or related to the present invention include the following. Patent Document 1: JP-A-5-250724 A recording layer is formed by dispersing, in a rubber-like elastic material, a transparent substrate that is thermally expanded and deformed by heating and that the deformed state can be maintained by subsequent cooling. An optical recording medium is disclosed. In the specification, there is a description that the recording layer is thermally deformed (surface swelling), but there is no description about the substrate. A recording method using a phthalocyanine dye as a recording layer, forming a cavity on the substrate side by melting and sublimating the dye, and forming a capsule part covering the cavity on the recording layer side. Has been described. -JP-A-6-338059 (Patent No. 285806)
No. 7) This is an optical recording medium having a resin substrate, a recording layer containing an organic dye, and a reflective layer, wherein the dye is partially decomposed in the recording mark portion and the bottom surface of the groove is deformed (the content of the patent). Indicates the amount of deformation of the groove bottom). The deformation of the groove bottom surface is described as a deformation in the track direction (scanning direction of the laser beam), and there is no description of the deformation in the radial direction of the substrate as in the present invention.

JP-A-8-58238 (Patent No. 2)
No. 709904) A recording method in which a recording layer and a substrate are simultaneously deformed by recording using a laminated body including a resin substrate, a recording layer (a dye layer + a metal layer), and a protective layer is described. The part of the dye layer and the substrate part is greatly concavely deformed, and a space is formed inside. Patent Document 1: JP-A-8-241534 An optical recording medium in which a substrate, a recording layer, a reflective layer, and a protective layer are sequentially laminated, wherein the recording layer is composed of two or more polymers having different thermal properties and an organic dye. It describes that recording is performed by thermal deformation of a polymer. In the description,
There is a description that the recording layer is thermally deformed, but there is no description about the substrate. Further, there is no description about how the recording layer is thermally deformed. Patent Document 1: Japanese Patent Application Laid-Open No. 9-265660 This is an optical recording medium in which a composite function layer having a function of a reflective layer and a recording layer and a protective layer are sequentially formed on a substrate, and the recording is formed by bumps of the substrate and the composite function layer. Are described. -JP-A-10-124926 (Patent No. 29663)
No. 77) Describes an optical recording medium including a substrate, a metal thin film, a buffer layer, and a reflective layer, in which recording is performed by changing the thickness of the buffer layer due to expansion of the substrate.

An optical recording medium comprising a substrate, a metal thin film, a deformable buffer layer, and a reflective layer, wherein recording is performed by changing the thickness of the buffer layer due to expansion of the substrate. Is described. JP, 10-264518, A A light absorption layer consists of an organic dye which contains chlorine in at least a substituent, a counter ion or a ligand, and adsorbs free chlorine with aluminum or silver with alteration and decomposition of the organic dye. A recording method for performing recording by reacting is described. In the specification, there is a description of substrate deformation (expansion) due to recording and a description of a substrate deformation shape in a track direction (scanning direction of laser light). Patent No. 2506374 Describes an optical recording medium in which a metal thin film is laminated on a plastic substrate having a fine uneven structure on the surface, and recording is performed by deforming the metal thin film to form bubbles. . -Japanese Patent No. 2548570 Describes an optical recording medium in which an organic dye layer and a protective layer are laminated on a substrate, and which performs recording by deformation and deterioration of the recording layer.

[0007] Patent No. 2570727, Patent No. 258
No. 1036 describes that recording is performed on a recording layer formed on a substrate by thermal deformation, formation of an opening or a concave portion. -Patent No. 2591939, Patent No. 2591940 On an optical recording medium in which a light absorbing layer, a recording auxiliary layer, and a light reflecting layer are laminated on a substrate, a recording portion is formed by concave deformation of the recording auxiliary layer and the light reflecting layer. The recording method is described. Patent No. 2591941 A recording method is described in which a recording portion is formed on an optical recording medium having a light absorbing layer and a light reflecting layer laminated on a substrate by concave deformation of the light absorbing layer and the light reflecting layer.・ Patent No. 2830345 A recording method is described in which a first resin layer and a second resin layer are provided on a substrate and recording is performed by forming a gap between the first resin layer and the second resin layer. I have. Patent No. 2838558 For an optical recording medium in which a recording layer containing a dye and a reflective layer are laminated on a substrate, a decomposed product of the recording layer material is contained at the interface between the substrate and the recording layer, and the substrate material is used. A recording method is described in which a decomposed product layer that is substantially not contained is formed, and recording is performed by forming a void on the decomposed product layer.

As described above, the principle of recording is not clear in any of the conventionally proposed recording methods. because,
In the conventional open technology, a recording method that mainly focuses on substrate expansion, formation of a cavity, or decomposition of a dye is proposed and presented. However, there is no document that verifies that a sufficient degree of modulation is actually generated due to substrate expansion, cavity, or dye decomposition. That is, in an actual optical disk, the recording portion is formed by a composite of substrate expansion, cavity, dye decomposition, and the like. Therefore, for example, if recording is performed by substrate expansion, other (occurringly generated) Recording mode (recording principle)
It cannot be said that the degree of modulation is mainly caused by the deformation of the substrate as long as. In other words, even if recording is performed on an optical disc and the presence of substrate expansion, cavities, or dye decomposition is confirmed, evidence that substrate expansion, cavities, or dye decomposition, etc., is actually generating a sufficient degree of modulation. Does not. In order to show that the invention is correct, it is necessary to prove that substrate expansion, cavity, or dye decomposition actually generates a sufficient degree of modulation, for which substrate expansion, cavity, or It is necessary to verify by simulation whether or not to produce a disk in which dye decomposition or the like occurs alone.

[0009]

As described above, as a recording method (recording principle) of a write-once type optical recording medium, expansion of a substrate (bump), decomposition of a recording layer material, deformation of a reflection layer, and the like can be mentioned. However, there is a problem that a sufficient degree of modulation is not generated only by these recording principles. For example, an optical recording medium in which a recording layer and a reflective layer are sequentially laminated on a substrate,
The substrate groove shape is (A, B, C, D, ζ) = [aλ, (a +
0.2) λ, (2a + 0.2) λ, 1.14λ, 0.2
5λ] (the groove parameter is shown in FIG. 1), the substrate groove shape is not changed by recording, and the absorption coefficient of the recording layer changes from 0.05 to 0.01 due to the decomposition of the recording layer material (recording). Consider how much a reduction in absorption coefficient due to layer decomposition produces a degree of modulation). The degree of modulation at this time is determined by the refractive index n of the recording layer and the width of the substrate groove opening: Groov.
When e top width [= (2a + 0.2) λ] is calculated as a parameter, ｛a = [C− (BA)] /
2, the result shown in FIG. 7 is obtained. The degree of modulation was calculated by [(sum signal obtained from unrecorded portion)-(sum signal obtained from recorded portion)] / (sum signal obtained from unrecorded portion). The recording layer was formed such that the interface between the recording layer and the reflective layer became flat. The details of the simulation conditions are as described later (the length is shown in units of the recording / reproducing wavelength λ). However, in FIG. 7, the recording / reproducing wavelength is assumed to be 650 (nm), and the width of the substrate groove opening (groove) is assumed.
The “ve top width” was expressed in nm [nm display value = λ display value × 650 (nm)].

(Details of simulation conditions) Beam shape: Gaussian distribution Radius where amplitude is 1 / e (x direction, y direction): 500
0λ, 5000λ • Objective lens aperture radius: 3000λ • Objective lens NA (numerical aperture): 0.60 • Objective lens focal length: 5000λ • Groove shape (A, B, C, D, ζ) (see FIG. 1): [ aλ, (a + 0.2) λ, (2a + 0.2) λ, 1.
14λ, 0.25λ] substrate refractive index: 1.58 (substrate side incident) recording layer refractive index: ni−0.05 before recording, ni−0.
01 ... After recording ・ Recording layer thickness d (see FIG. 3): 0.1λ ・ Reflection layer refractive index: 0.13-i3.16 ・ Reflection layer thickness: 0.23λ ・ Detector: 4-split PD ・ Detection Radius of vessel (x direction, y direction): 3000λ, 30
00λ

As shown in the results of FIG. 7, it is apparent that in the case of an optical recording medium having an organic material as a recording layer, a sufficient modulation factor cannot be achieved by the conventionally proposed decomposition of the recording layer. is there. In addition, a write-once type optical recording medium using an inorganic material requires a recording method capable of obtaining good recording characteristics. Accordingly, an object of the present invention is to provide an optical recording medium having a recording layer provided on a substrate having at least a pre-groove and capable of easily obtaining a recording contrast (modulation degree), and a recording method thereof.

[0012]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that an optical recording medium in which a recording layer is provided on at least a substrate having a pre-groove and a recording portion is formed in a groove of the pre-groove, In a recording method (recording principle) conventionally proposed such as expansion of a substrate (bump), decomposition of a recording layer material, deformation of a reflective layer, etc., a sufficient recording contrast (modulation degree) depends on a refractive index of the recording layer material. In order to improve the problem that the recording layer cannot be obtained, the present inventors have newly found a recording method capable of obtaining a sufficient recording contrast (modulation degree) without largely depending on the refractive index of the recording layer material.

That is, the above-mentioned object is solved by the following inventions 1) to 9). 1) An optical recording medium in which a recording layer is provided on at least a substrate having a pre-groove, and a recording portion is formed in a groove of the pre-groove as a change in groove width by irradiation with a laser beam, the groove opening width of the substrate being An optical recording medium, characterized in that a recording portion is formed by making the groove bottom width increase amount larger than the increase amount. 2) An optical recording medium in which a recording layer is provided at least on a substrate having a pre-groove and a recording portion is formed as a change in groove width in a groove of the pre-groove by irradiation of a laser beam, wherein the groove opening width of the substrate is An optical recording medium characterized in that a recording portion is formed by enlarging only a groove bottom width of a substrate without changing the width of the substrate. 3) The optical recording medium according to 1) or 2), wherein a reflective layer is further provided on the recording layer. 4) The optical recording medium according to any one of 1) to 3), wherein the recording layer is made of an organic material. 5) The light according to any one of 1) to 4), wherein the thickness of the recording layer formed on the pre-groove is sufficiently thicker in the groove than in the inter-groove portion. recoding media. 6) A recording method for an optical recording medium in which a recording layer is provided on a substrate having at least a pre-groove, and a recording portion is formed as a change in groove width in a groove of the pre-groove by irradiation of a laser beam. A recording portion formed by increasing the groove bottom width increase amount with respect to the groove opening width increase amount. 7) A method for recording on an optical recording medium in which a recording layer is provided on at least a substrate having a pre-groove and a recording portion is formed as a change in groove width in a groove of the pre-groove by irradiating a laser beam. Without changing the groove opening width of
A recording method wherein a recording portion is formed by enlarging only the width of a groove bottom of a substrate. 8) The recording method according to 6) or 7), wherein the optical recording medium has a reflective layer further provided on a recording layer. 9) The recording method according to any one of 6) to 8), wherein the recording layer of the optical recording medium is made of an organic material.

Hereinafter, the present invention will be described in detail. The groove shape of the substrate in the unrecorded state of the optical recording medium having the pre-groove is, for example, as shown in FIG.
ζ, substrate groove dripping amounts: A and CB, substrate groove bottom width: BA, substrate groove top width (groove opening width): C, track pitch: D (land) A, B, C, and D are set starting from the edge of the section). In the present invention, as shown in FIG. 2A, the groove shape in the unrecorded state [width of groove bottom: (B-A), width of groove above groove (groove opening width): C] (see FIG. 2 only shows the substrate), and as shown in FIG. 2B, the width of the groove bottom of the substrate is (BA) + α by recording and the width of the upper part of the substrate groove (groove opening width) is C + β. A recording method for enlarging, where α>β>
0, or α> 0 and β ≒ 0.
With this recording method, it is possible to easily obtain a high degree of modulation.

Further, in the present invention, using this recording method,
The thickness of the recording layer in the groove portion of the pre-groove is made sufficiently thicker than the thickness of the recording layer in the inter-groove portion, whereby the degree of modulation can be greatly improved. This is because, in the present invention, when the recording layer thickness of the groove portion of the pre-groove and the recording layer thickness of the inter-groove portion approach each other, recording can be performed sufficiently, but the reflectance of the recording portion is higher than the reflectance of the unrecorded portion. It is based on the finding that it may be. In the recording method of the present invention, since the modulation degree is efficiently generated by changing the groove bottom width of the substrate, it is preferable that the groove shape at the time of forming the substrate is: substrate groove opening width> substrate groove bottom width.

The recording method of the present invention is mainly intended to increase the groove bottom width increase amount with respect to the substrate groove opening width increase amount. However, as the substrate groove width increases, the refractive index change of the recording layer material changes. Or it may involve expansion (bump) of the substrate bottom. In the present invention, an organic material is preferably used as a recording layer material, but the material is not limited thereto, and any material having an effect of absorbing a laser beam and widening a groove width may be used. Can be. The action of widening the groove width can be obtained by the temperature rise of the recording layer material, gas generation, decomposition, explosion, expansion action and the like. Although the recording layer material itself does not cause any physical change from the beginning, an effect of generating a distortion in an adjacent layer by increasing the temperature and cooling by absorption of the laser beam may be used.

[0017]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 As shown in FIG. 3A, the substrate groove shape in the unrecorded state is (A,
B, C, D, ζ) = [aλ, (a + 0.2) λ, (2a
+0.2) λ, 1.14 λ, 0.25 λ] (see FIG. 1 for the definition of the groove parameter), and the substrate groove shape by recording is changed to (A, B, C, D, ζ) = [0,
(2a + 0.2) λ, (2a + 0.2) λ, 1.14
λ, 0.25λ] when the modulation degree [a
= {(C + β)-[(BA) + α]} / 2, and α
> 0 and β = 0] were calculated using the refractive index n of the recording layer and the width of the opening of the substrate groove [= (2a + 0.2) λ] as parameters. The degree of modulation was calculated by [(sum signal obtained from unrecorded portion)-(sum signal obtained from recorded portion)] / (sum signal obtained from unrecorded portion). The recording layer was formed such that the interface between the recording layer and the reflective layer was flat, as shown in FIG. The details of the simulation conditions are as described below (the length is shown in units of the recording / reproducing wavelength λ), and the result is as shown in FIG. In FIG. 5, the recording / reproducing wavelength is assumed to be 650 (nm), and the width (groove top width) of the substrate groove opening is expressed in nm [nm display value = λ display value × 650 (nm)]. From this result, it can be seen that when the groove opening width is a certain value and the refractive index of the recording layer is about 2.2 or more, a high degree of modulation can be obtained by enlarging the groove bottom, and the effect of the present invention is confirmed. Was.

(Details of simulation conditions) Beam shape: Gaussian distribution Radius where amplitude is 1 / e (x direction, y direction): 500
0λ, 5000λ • Objective lens aperture radius: 3000λ • Objective lens NA (numerical aperture): 0.60 • Objective lens focal length: 5000λ • Groove shape (A, B, C, D, ζ) (see FIG. 1): recording Previous [aλ, (a + 0.2) λ, (2a + 0.2)
λ, 1.14λ, 0.25λ] After recording [0, (2a + 0.2) λ, (2a + 0.2)
[lambda], 1.14 [lambda], 0.25 [lambda]]-substrate refractive index: 1.58 (substrate side incidence)-recording layer refractive index: ni-0.05-recording layer thickness d (see Fig. 3): 0.1 [lambda] Reflective layer refractive index: 0.13-i3.16 Reflective layer thickness: 0.23λ Detector: 4-split PD Radius of detector (x direction, y direction): 3000λ, 30
00λ

Example 2 The effect of another embodiment of the present invention, that is, the effect of forming the recording layer formed on the pre-groove so that the film thickness in the groove was sufficiently thicker than that between the grooves was confirmed. Specifically, in Example 1, the modulation factor was calculated under the same calculation conditions as in Example 1 except that the thickness of the recording layer was made equal between the groove portions (grooves) and the inter-groove portions (lands) (see FIG. 4). Calculated. The result is as shown in FIG. In FIG. 6, the recording / reproducing wavelength is 650 (n).
m) and the width of the groove opening of the substrate (Groove to
p width) was expressed in nm [nm display value = λ display value × 650 (nm)]. From this result, when the film thickness of the recording layer is made equal between the groove portion (groove) and the inter-groove portion (land), the polarity of the modulation degree changes (the reflectance of the recorded portion increases with respect to the unrecorded portion). The effectiveness of the film thickness setting shown in No. 1 was confirmed.

[0021]

According to the optical recording medium and the recording method of the present invention, it is possible to provide a write-once optical recording medium capable of easily obtaining a high degree of modulation and a recording method thereof.

[Brief description of the drawings]

FIG. 1 is a view showing a substrate groove shape in an unrecorded state of an optical recording medium having a pregroove.

FIG. 2A is a cross-sectional view showing a groove shape of a substrate in an unrecorded state. (B) Sectional view showing the groove shape of the substrate after recording.

FIG. 3A is a sectional view of an optical recording medium according to a first embodiment in an unrecorded state. (B) Sectional view of the optical recording medium of Example 1 after recording.

FIG. 4A is a cross-sectional view of an optical recording medium according to a second embodiment in an unrecorded state. (B) A sectional view of the optical recording medium of Example 2 after recording.

FIG. 5 is a diagram showing a result of calculating a modulation degree of the optical recording medium of Example 1 using the refractive index n of the recording layer and the width of the opening of the substrate groove as parameters.

FIG. 6 is a diagram showing a result of calculating a modulation factor of the optical recording medium of Example 2 using a refractive index n of a recording layer and a width of a substrate groove opening as parameters.

FIG. 7 is an optical recording medium in which a recording layer and a reflection layer are sequentially laminated on a substrate, wherein the substrate groove shape is unchanged by recording, and the absorption coefficient of the recording layer is 0.05 to 0 due to decomposition of the recording layer material. FIG. 9 is a view showing a result of calculating a modulation degree when the modulation degree changes to .01 by using the refractive index n of the recording layer and the width of the substrate groove opening as parameters.

[Explanation of symbols]

 A: Groove amount of substrate groove CB: Groove amount of substrate groove BA: Width of groove bottom of substrate C Width of groove top of substrate (groove opening width) D Track pitch 溝 groove depth of substrate

Claims (9)

[Claims] An optical recording medium comprising: a recording layer provided on a substrate having at least a pre-groove; and a recording portion formed as a change in groove width in a groove of the pre-groove by irradiation of a laser beam. An optical recording medium, characterized in that a recording portion is formed by increasing the groove bottom width increase amount with respect to the groove opening width increase amount. 2. An optical recording medium comprising: a recording layer provided on a substrate having at least a pre-groove; and a recording portion formed as a change in groove width in a groove of the pre-groove by irradiation of a laser beam. An optical recording medium wherein a recording portion is formed by enlarging only the width of a groove bottom of a substrate without changing a groove opening width. 3. The optical recording medium according to claim 1, wherein a reflection layer is further provided on the recording layer. 4. The optical recording medium according to claim 1, wherein said recording layer is made of an organic material. 5. The recording layer according to claim 1, wherein the thickness of the recording layer formed on the pre-groove is sufficiently larger than the thickness of the inter-groove portion. The optical recording medium according to the above. 6. A method for recording on an optical recording medium wherein a recording layer is provided on at least a substrate having a pre-groove, and a recording portion is formed as a change in groove width in a groove of the pre-groove by irradiation of a laser beam. And forming the recording portion by increasing the groove bottom width increase amount with respect to the groove opening width increase amount of the substrate. 7. A method for recording on an optical recording medium wherein a recording layer is provided on at least a substrate having a pre-groove, and a recording portion is formed as a change in groove width in a groove of the pre-groove by irradiation of laser light. Forming a recording portion by enlarging only the width of the groove bottom of the substrate without changing the groove opening width of the substrate. 8. The optical recording medium according to claim 6, wherein a reflection layer is further provided on the recording layer.
Or the recording method according to 7. 9. The recording method according to claim 6, wherein the recording layer of the optical recording medium is made of an organic material.