JP2007035081A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium in which when recording is performed using organic dye by laser beam, especially by blue laser beam, this dye (especially organic dye used for recording of a blue laser) is stably held by deformation of that organic dye, recording characteristics is not spoiled, in addition intensity (amplitude) of a signal does not change with recursive reproduction, and reproduction characteristics by which reading errors cannot occur easily is not spoiled. <P>SOLUTION: In an optical information recording medium comprising a transmission layer which transmits a laser beam, and a recording layer on which information is recorded by the laser beam, the optical information recording medium is characterized in that this optical recording layer contains organic dye and is provided with an intervention layer of which principal component is Nb<SB>2</SB>O<SB>4.5-5.5</SB>between the above transmission layer and optical recording layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical information recording medium using an organic dye in an optical recording layer that can be written and reproduced at high density and high speed by blue laser light (blue laser light) in the vicinity of 350 to 500 nm (for example, around 405 nm), in particular. The present invention relates to an optical information recording medium in which recorded information does not deteriorate even when repeated reproduction is performed.

  As an optical information recording medium, a so-called write-once optical disk is first developed as a CD-R using a red laser beam having a wavelength of 750 to 830 nm of a semiconductor laser irradiated for recording and reproducing information, and then a wavelength shorter than this. DVD-R / + R (“+ R” is rewritable) using a short wavelength red laser beam of 640 to 680 nm has been developed and is widely used. In recent years, optical discs that can be recorded and reproduced using blue laser light in the vicinity of 350 to 500 nm (for example, around 405 nm) on the short wavelength side have also been developed. These optical discs use an organic dye compound in the optical recording layer, and as the laser beam becomes shorter, there is a tendency to require more precision in selecting a light-transparent substrate, an organic dye compound, and the like.

For write-once optical discs with blue lasers, various attempts have been made to apply conventional optical recording medium technologies, such as CD and DVD technologies, but blue lasers use light with a short wavelength. The type optical recording medium has a problem that signal deterioration is likely to occur during reproduction due to a structural problem, and an improvement measure is required.
That is, in order to conform to the standard as a transparent substrate, (i) a groove is formed on a 1.1 mm substrate, a reflective film is formed, a dye is formed, and a dye protective layer is sequentially formed. , A method of affixing a 0.1 mm sheet, (ii) forming a groove on a 1.1 mm substrate, forming a reflective film, forming a dye, and forming a dye protective layer in order, Two methods of forming a 0.1 mm permeable membrane by spin coating have been proposed, both of which have a thickness of 1.1 mm + 0.1 mm = 1.2 mm and 1.2 mm as in the case of CD and DVD. Become thick.

For example, Japanese Patent Application Laid-Open No. 2005-93027 describes an optical information recording medium having a structure in which a ZnS—SiO ₂ layer is interposed in a phase change type recording layer. There are also proposals for optical information recording media having the same configuration except that each of ZnO, ZnS, and SiO ₂ is used instead of ZnS—SiO ₂ , but these improve the enhancement effect and prevent light degradation. It is intended to secure the function.

JP-A-2005-93027

However, when ZnO is used as the intervening layer, the refractive index is too high and a reverse enhancement effect is likely to occur depending on the film thickness condition. When ZnS—SiO ₂ is used, S is used for the recording layer for reliability. In order to degrade organic dyes, it is not suitable for write-once type optical recording media, and when SiO ₂ is used, there is a problem that cracks are likely to occur, and any optical recording media having any photodegradation prevention layer has a thickness of 350 nm to 530 nm. When high-density recording is performed with a short-wavelength laser beam of a certain degree, there is not only a problem in the recording characteristics regarding the distinction of individual pits corresponding to each signal, but the signal strength (amplitude) is also increased by repeated reproduction. There is also a problem in the reproduction characteristics that change and are likely to cause a reading error.

  The object of the present invention is to record an organic dye with a laser beam, particularly a blue laser beam, so that the dye (especially the organic dye used for blue laser recording) is stably held by the deformation of the organic dye. It is an object of the present invention to provide an optical information recording medium that does not impair the characteristics, does not change the intensity (amplitude) of the signal even after repeated reproduction, and does not impair the reproduction characteristics that hardly cause reading errors.

As a result of intensive studies, the present inventors have found that when an intervening layer containing Nb ₂ O _4.5-5.5 is provided between a recording layer made of an organic dye film and a layer that transmits laser light (laser light transmitting layer), 350 nm When performing high-density recording with a short-wavelength laser beam of about 530 nm, the intervening layer can sufficiently follow even by deformation, so that deterioration of the dye is suppressed as much as possible, and the reliability as the recording layer is ensured, The present inventors have found that the reproduction characteristics are not deteriorated so that the recording characteristics are not deteriorated and the change in signal intensity is small even by repeated reproduction and the occurrence of reading errors is suppressed.
Accordingly, the present invention provides (1) an optical information recording medium having a transmission layer that transmits laser light and a recording layer on which information is recorded by the laser light, wherein the optical recording layer contains an organic dye. Thus, an optical information recording medium comprising an intervening layer containing Nb ₂ O _4.5-5.5 as a main component between the transmission layer and the optical recording layer is provided.
Further, the present invention is (2) the optical information recording medium of (1) above, wherein the laser beam is a blue laser beam having a wavelength of 350 to 500 nm, (3), wherein the intervening layer is formed by DC sputtering. The optical information recording medium of (1) or (2) is provided.

According to the present invention, since the intervening layer containing Nb ₂ O _4.5-5.5 is provided on the recording layer made of the organic dye film, after recording with laser light, particularly blue laser light, laser light, particularly blue laser It is possible to provide an optical information recording medium that does not deteriorate the recording characteristics and reproducing characteristics even if it is repeatedly reproduced by irradiating with light, thereby enabling high-speed, high-capacity and high-definition that can be particularly compatible with blue lasers. An optical information recording medium capable of recording and reproduction can be provided.

The optical information recording medium of the present invention is an optical information recording medium having a so-called HD DVD write-once disc structure and a so-called blue-ray write-once disc that can be recorded and reproduced using blue laser light (wavelength 350 nm to 530 nm). Although it can be applied to any optical information recording medium with a structure, the transmissive layer (substrate) that transmits laser light is very thin, and it is particularly useful for Blu-ray technology that requires stability in manufacturing and holding the laser transmissive layer. It is valid.
As shown in FIG. 1, the HD DVD write-once disc 1 has grooves formed in a translucent substrate 2 that transmits laser light, an intervening layer 3a is formed, a dye film 3b is formed, and a light reflecting layer 4 And the light transmission layer 5 are sequentially formed. The light transmissive layer 5 may be only the dye protective layer 5a. In some cases, a dummy substrate 6 having a predetermined thickness is laminated on the upper layer of the dye protective layer 5a, and the predetermined thickness required for the standard (of the substrate) The thickness may be 0.6 mm in total and the thickness of the dummy substrate 6 is 0.6 mm, for a total thickness of 1.2 mm).
As shown in FIG. 2, the intervening layer 3a may be bonded to the substrate 2 via the adhesive layer 2a. The intervening layer 3 a is firmly fixed to the substrate 2.
As shown in the figure, when the laser light 9 (recording light) is irradiated from the translucent substrate 2 (incident layer) side, the dye contained in the dye film 3 b absorbs the energy of the laser light 9. Heat is generated (or absorbed), and pits 10 are formed by thermal decomposition of the dye film 3b.

As shown in FIG. 3, the Blu-ray write-once disc 20 has a groove formed on a translucent substrate 2 having a thickness of, for example, 1.1 mm, a reflective layer 4 is formed, a dye film 3b is formed, and an intervening layer 3a is formed. And the light transmission layer 5 are sequentially formed. The light transmission layer 5 may be formed only by forming the dye protective layer 5a, but may further form a light transmission film 22 having a thickness of, for example, 0.1 mm by the adhesive layer 21 (thickness 1. of the substrate 2). 1 mm and the thickness of the light transmission film 22 is 0.1 mm, and the total thickness is 1.2 mm).
Also, as shown in FIG. 4, for example, a groove is formed in a light-transmitting substrate 2 having a thickness of 1.1 mm, a reflective film 4 is formed, a dye film 3b is formed, an intervening layer 3a is formed, and light The transmission layer 5 is sequentially formed. The light transmission layer 5 is formed with a dye protective film 5a, and then a light transmission film 22 of 0.1 mm is formed by spin coating.
As shown in the figure, when the laser beam 9 (recording light) is irradiated from the incident layer (light transmitting film 22) side of the light transmitting layer 5 as a layer that transmits the laser light to the Blu-ray write-once disc 20, the dye film 3b is irradiated. The contained dye generates heat (or absorbs heat) by absorbing the energy of the laser beam 9, and pits 10 are formed by thermal decomposition of the optical recording layer 3b.

In any of the above optical disks, the substrate 2 has a pregroove 7 formed in a spiral shape. On the left and right sides of the pregroove 7, portions other than the pregroove 7, that is, lands 8 are located.
The translucent substrate 2 is a highly transparent material having a refractive index with respect to the laser beam of, for example, about 1.5 to 1.7, and is mainly formed of a resin excellent in impact resistance, such as polycarbonate. A resin plate such as a plate, an acrylic plate, or an epoxy plate is used, but a glass plate is also used.

The intervening layer 3a is a layer containing Nb ₂ O _4.5-5.5 as a main component, and the other side of the dye film 3b with respect to the laser beam, that is, between the light transmitting layer 5 and the dye film 3b, or on the dye film 3b. When the intervening layer 3a is provided via a layer, it may be provided directly or indirectly on the front side of the dye film 3b. The intervening layer 3a needs to be a layer mainly composed of Nb ₂ O _4.5-5.5 . Nb ₂ O _4.5-5.5 is a compound composed of various ratios of Nb high oxide and low oxide, and O _4.5-5.5 means that O is 4.5 to 5.5 atoms. _It can be said that 1: 1 (molar ratio) of ₂ O ₄ and Nb ₂ O ₅ is Nb ₂ O _4.5. However, the production method can be selected by adjusting the oxygen content, and the general formula is Nb ₂ O _{4. 2} O ₅ , and the layer formation can be usually performed by using direct current sputtering (AD sputtering). However, if the amount of oxygen is reduced, high-frequency sputtering (DC sputtering) superior in manufacturing can be applied.
The thickness of the intervening layer 3a is preferably 10 nm to 150 nm, particularly preferably 20 nm to 60 nm. If it is too thin, it is easily affected by the material of the adjacent layer, and its improvement effect is difficult to be recognized. It may be reduced.

The dye film 3b is a layer made of an organic dye film (thickness: 50 nm to 120 nm) containing an organic dye material formed on the substrate 2, and generates heat, heat absorption, melting, sublimation, and deformation by irradiating laser light 9. Or it is a layer with modification | denaturation. The dye film 3b is formed by, for example, uniformly coating the surface of the substrate 2 with an organic dye material dissolved in a solvent by means such as a spin coat method.
The light reflection layer 4 is a metal film having high thermal conductivity and high light reflectivity. For example, a metal material such as gold, silver, copper, aluminum, or an alloy containing them is deposited by means such as vapor deposition or sputtering. It is formed.
The dye protective layer 5a is formed of a resin having excellent impact resistance and adhesion similar to the substrate 2. For example, it is formed by applying an ultraviolet curable resin by a spin coating method and irradiating it with ultraviolet rays to be cured.
The dummy substrate 6 is made of the same material as the substrate 2 and secures a predetermined thickness of about 1.2 mm.
The HD DVD write-once disc 1 and the Blu-ray write-once disc 20 have only one layer of the dye film 3b. However, the dye film 3b may be provided in a plurality of layers together with the accompanying layers, and may be a so-called multilayer type. Further, high density and high capacity recording can be realized.

  The above organic dyes include azo, phthalocyanine, cyanine, squalium, naphthalocyanine, quinazoline, coumarin, volphyrin, subphthalocyanine, indigo, anthraquinone, benzoquinone, styryl, and spirobiran. , Spirooxazine, Croconium, Acridine, Fluorescein, Triarylmethane, Merocyanine, Azurenium, Naphthoquinone, Indophenol, Xanthene, Oxazine, Bililium, etc. be able to. In the present invention, it is preferable to use azo, phthalocyanine, cyanine, squalium, or quinazoline from the viewpoint of improving the adhesion with the intervening layer, recording characteristics, and reproducing characteristics.

These organic dye materials and other additives as required are added to a solvent to prepare a mixed solution, which is applied to the substrate shown in FIGS. 1 to 4 using, for example, a spin coating method, and the optical recording layer 3b is formed. Form.
The solvent is preferably a fluorinated alcohol such as 2,2,3,3-tetrafluoro-1-propanol, but chloroform, dichloroethane, methyl ethyl ketone, dimethylformamide, methanol, toluene, cyclohexanone, acetylacetone, diacetone alcohol, methyl cellosolve. Such cellosolves, dioxane and the like can be used alone or in combination so that they do not erode the substrate, and can also be used in combination with one or more fluorinated alcohols.

Next, an embodiment of the present invention will be described with reference to FIGS.
Example 1
A compound of the following [Chemical Formula 1] (monomethine dye) was dissolved in TFP (2,2,3,3-tetrafluoro-1-propanol) to prepare a solution to obtain a coating solution.

(Manufacture of Blu-ray write-once discs)
As shown in FIG. 3, a silver alloy is DC-sputtered onto a disk-shaped substrate 2 made of polycarbonate and having an outer diameter of 120 mm and a thickness of 0.6 mm, and a light reflecting layer 4 having a thickness of 100 nm. Formed.
Next, the above coating solution was applied onto the light reflecting layer by a spin coating method at a predetermined rotational speed to form a dye film b consisting of a uniform thin film (thickness 20 to 60 nm).
Then, an intervening layer 3a made of Nb ₂ O ₅ was formed on the dye film 3b by DC sputtering.
Further, an adhesive was applied in advance, and a light-transmitting film 22 having the same material as that of the substrate and having a thickness of 0.1 mm and an outer diameter of 120 mm was bonded together to make a Blu-ray write-once disc 20.

(Reproduction signal recording characteristics evaluation)
About the Blu-ray write-once disc 20 thus obtained, the optical disc evaluation device (DDU-100) manufactured by Pulstec Industrial Co., Ltd. equipped with a blue laser with a wavelength of 406 nm (NA (aperture ratio) 0.85) was used. A blue laser beam is irradiated from the light transmission film 22 side, and an EFM signal is produced at a linear velocity of 5.28 m / s (seconds), a recording capacity of 23 GB, a track pitch of 0.32 μm, a data bit length of 0.153 μm, and a recording power of 5 mW. Recorded.
Next, in order to perform a reproduction light deterioration test of the recording portion, reproduction is performed with a reading power of 0.4 mW using a blue laser beam of 406 nm. This is repeated 50,000 times, and the “initial” and “after reproduction” ( The signal quality after 50,000 times reproduction) was obtained, and the “deterioration” was obtained as a numerical value (“after reproduction” − “initial”).

Comparative Example 1
In Example 1, a Blu-ray write-once disc was prepared in the same manner as in Example 1 except that a film made of SiO ₂ was provided in the same manner instead of the film made of Nb ₂ O _5. The reproduction signal recording characteristics were evaluated.

Comparative Examples 2-6
In Example 1, instead of the film made of Nb ₂ O ₅ , a film made of oxides and nitrides of SiN, ZnS—SiO ₂ , SiO ₂ , and AlN was provided in the same manner. Then, a Blu-ray write-once disc was produced, and the reproduction signal recording characteristics were also evaluated in the same manner as in Example 1.

The above examples and comparative examples were for Blu-ray write-once discs, but the HD DVD write-once discs in FIGS. 1 and 2 were also obtained according to these examples and comparative examples. Can show. In the HD DVD, the track pitch is 0.40 μm, the capacity is 15 GB, the linear velocity is 6.61 m / s, and the NA is 0.65.
The “intervening layer” stably holds the substrate and the recording layer, suppresses the deterioration of the substrate and the recording layer, and is particularly effective for a Blu-ray type recording information recording medium having a thin substrate, and may be a “deterioration suppressing layer”. .

It is principal part expanded sectional explanatory drawing of an example HD DVD write-once disc which can apply this invention. It is principal part expanded sectional explanatory drawing of the HD DVD recordable disc of the other example. 1 is an enlarged cross-sectional explanatory view of a main part of a Blu-ray write-once disc according to an embodiment of the present invention. It is principal part expanded sectional explanatory drawing of the Blu-ray write-once disc of the other Example of this invention.

Claims (3)

In an optical information recording medium having a transmission layer that transmits laser light and a recording layer on which information is recorded by the laser light, the optical recording layer is a layer containing an organic dye, and the transmission layer and the optical recording layer An optical information recording medium comprising an intervening layer containing Nb ₂ O _4.5-5.5 as a main component.   The optical information recording medium according to claim 1, wherein the laser light is blue laser light having a wavelength of 350 to 500 nm.   The optical information recording medium according to claim 1, wherein the intervening layer is formed by DC sputtering.

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