Patent Application
20100086724
1. Field of the Invention
The present invention generally relates to an optical recording medium. More particularly, the present invention relates to organic dye compound and an optical recording medium including the same.
2. Description of Related Art
Organic dye compounds are popularly used for fabricating organic optical recording media because of their advantages of low cost and excellent recording characteristics. In recent years, development of optical recording media employing laser have been remarkable. An example of the optical recording medium, such as an optical disc, is generally designed to irradiate a focused laser beam of about 1 μm to a thin recording layer formed on a disc shaped substrate to conduct information recording. The recording is implemented in a manner that upon absorption of the laser beam energy, the irradiated portion of the recording layer undergoes a thermal deformation such as decomposition, evaporation or melting. Reading the difference in the reflectance between the portion having a deformation formed by the laser beam and the portion without such deformation carries out reproduction of the recorded information. Accordingly, an optical recording medium is required to efficiently absorb the energy of the laser beam, and is also required to have a predetermined amount of absorbed light to a laser beam having a specific wavelength employed for recording and to be high in the reflectance to laser beam having a specific wavelength employed for reproduction for accurately conducting the reproduction of information.
Japanese patent JP 2007216439 belonging to Mitsubishi discloses the use of a metal complex including hydrazone ligand having a following general chemical structural formula for making the recording layer.
Japanese patent JP2007196661 belonging to Mitsubishi discloses the use of a following organic dye for making the recording layer.
International patent publication WO2006061398 belonging to Clariant discloses the use of azo metal dyes of pyridine N-oxide having a following general chemical structural formula for making the recording layer.
European patent publication EP1517316 belonging to Clariant discloses the use of a following azo type dye having a general chemical structural formula for making the recording layer.
In the present multimedia age, optical recording media such as CD-R (a write-once memory using compact disc) and DVD-R (a write-once memory using digital video disc) are now of great importance. Presently available high density television (HD-TV) is capable of storing two hours of digital information, memory has a storage capacity of about 15-50 GB, CD-R has a recording capacity of up to 650 MB and DVD-R has a recording capacity up to 4.7 GB, which is not sufficient for the ever increasing present demand to record movie and animations for six hours in image quality of standard television or for two hours even in relatively-high image quality of high definition television.
Some principles and methods of enhancement of the storage density of the optical information storage media include such as shifting of the wavelength of the laser source, for example, from red laser to blue laser, or enhancement of the objective numerical aperture (“NA”) of optical lens. Some other methods include improvement of the encoding methods of the digital signal, or a disc storage method using an extra-fine resolution near field optical structure, or a technology for increasing the storage capacity of the information storage media (e.g., a compact disc) by using stacked multiple recording layers, i.e., the recording layers of the information storage media is developed into a three dimensional space multilayer structure, to increase the storage capacity. All the methods described above may be employed to effectively increase the storage capacity of the optical recording medium.
However, since most organic dye compounds used in the conventional optical recording media cannot be used with visible light with a wavelength of 450 nm or less, they can not fulfill the need for high-storage density requirement. Therefore, if new organic dye compounds that can be used with visible light with a wavelength of 450 nm or less, it would be possible to significantly promote the recording capacity of the organic optical recording media. For example, a single-side Blue-ray Disc may be promoted up to 25 GB by employing a 405 nm blue laser source and a 0.1 mm optical transmission cover layer structure.
Thus, it is highly desirable to provide new organic dye compounds that exhibit excellent recording properties, such as exhibiting maximum absorbance at visible light with a wavelength of about 450 nm, excellent light fastness and light resistance, and better chemical and thermal stabilities.
Accordingly, the present invention is directed to an organic dye compound (I) suitable for making a recording layer that allows recording of information employing a short wavelength laser source and exhibit good write characteristics and compatible with the write-once recording medium.
According to an embodiment of the present invention, the anionic moiety of the organic dye compound (I) may enhance the recording properties, such as light fastness and light resistance, and chemical and thermal stabilities.
The present invention is also directed to an optical storage medium including a recording layer comprising the organic dye compound (I) for recording information and storing the recorded information such that good write characteristics and the compatibility with the write-once recording medium may be retained. The recording layer comprising the organic dye compound (I) exhibits excellent recording properties, such as exhibiting maximum absorbance at visible light with a shorter wavelength of 400 nm or 550, excellent light fastness and light resistance, and better chemical and thermal stabilities.
According to an embodiment of the present invention, the organic dye compound (I) comprise the following general chemical structural formulae, respectively:
wherein [A]+ includes alkaline metal ion,
wherein R1, R2, R3, R4, R5 and R6 each independently represent hydrogen, straight or branched C1-8 alkyl, C1-3 alkoxyl, halogen, nitro, benzyl group or substituted benzyl group wherein a substituent thereof is C1-2 alkyl, C1-2 alkoxyl, halogen or nitro. The above organic dye compound (I) exhibits the maximum absorbance at wavelength within a range of 400 to 550 nm, excellent light fastness and light resistance, and better chemical and thermal stabilities.
According to an embodiment of the present invention, the information may be recorded on the recording layer comprising the organic dye compound (I) employing a short wavelength laser source such as a 405 nm blue laser source. The recording layer has good write characteristics and is compatible with the write-once storage medium. The recording layer has an excellent light fastness and light resistance, and better chemical and thermal stabilities.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
The present invention provides an organic dye compound for a recording layer suitable for implementing recording of information thereon by employing short wavelength laser source, and reproduction/playback of the recorded information. The organic dye compound (I) comprises the following general chemical structural formula:
wherein [A]+ includes alkaline metal ion,
wherein R1, R2, R3, R4, R5 and R6 each independently represent hydrogen, straight or branched C1-8 alkyl, C1-3 alkoxyl, halogen, nitro, benzyl group or substituted benzyl group wherein a substituent thereof is C1-2 alkyl, C1-2 alkoxyl, halogen or nitro. The organic dye compound (I) exhibits a maximum absorbance at a wavelength range of 400-550 nm.
According to an embodiment of the present invention, the anionic moiety of the organic dye compound (I) may enhance the chemical and thermal stabilities, light resistance and light fastness.
A reaction scheme of an example synthesis process for organic dye compound (I) is presented as follows.
In the following organic cation,
R4 and R5 each independently represent hydrogen, straight or branched C1-8 alkyl, C1-3 alkoxyl, halogen, nitro, benzyl group or substituted benzyl group wherein a substituent thereof is C1-2 alkyl, C1-2 alkoxyl, halogen or nitro. The organic cation is known to persons skilled in the art. Please refer to US 20050226135A1.
Synthesis of azo compound (1): 2.95 g (42.8 mmol) of sodium nitrite was added into 100 ml flask containing 50 ml of HCl and 6.39 g (35.67 mmol) of 2-amino-4-(1,1-dimethyl-propyl)-phenol. Next, the resulting mixture was stirred for 1 hour. Next, the resulting stirred mixture was slowly poured into a flask containing 5 g (35.67 mmol) of 2-methyl-5-propyl-2,4-dihydropyrazol-3-one in 60 ml methanol. A yellowish-brown precipitate of azo compound (1) was formed, and the azo compound (1) was washed with water and then dried. Thus, 10.7 g of azo compound (1) with a yield of about 91% was obtained.
Synthesis of cobalt complex (2): 10 g of the above azo compound (1) was added into a 250 ml flask and then 5.09 g (62.04 mmol) of sodium acetate, 100 ml of methanol, 40 ml of alcoholic, and 3.77 g (15.13 mmol) cobalt acetate were added into the flask. The resulting mixture was refluxed for 24 hours. Next, dichloromethane was added to the reaction mixture to obtain brown precipitate. The brown precipitate was washed with water and then dried with MgSO4. Thus, 9.8 g of cobalt-complex (2) with a yield of 96% was obtained.
Synthesis of the organic dye compound (I-01): 3.33 g (4.91 mmol) of the above cobalt complex (2), 4.77 g (9.81 mmol) of cyanine (3) and 35 ml of methanol were added into a 100 ml flask and then mixed well. Next, the resulting mixture was heated and refluxed for 24 hours. The resulting refluxed mixture evaporated out methanol and 3.34 g of brown crystals of organic dye compound with a yield of 68.6% was obtained. The organic dye compound (I-01) has a λmax=459 nm and ∈=55,170. The reaction scheme is presented as follows.
Cyanine (3) has the following structure. Cyanine (3) is known to persons skilled in the art. Please refer to US 20050226135A1.
Hereinafter, an example synthesis process for organic dye compound (I-02) is described.
Synthesis process for organic compound (5): the process steps of this example is identical to those of the example 1 except that the reactants used in this example includes 5.49 g (35.67 mmol) of 2-amino-4-nitro-phenol, 3.2 g (46.37 mmol) of NaNO2 and 5 g (35.67 mmol) of 2-methyl-5-propyl-2,4-dihydro-pyrazol-3-one. Thus, 10.49 g of brown precipitate of organic compound (5) with a yield of 96% was obtained.
Synthesis of organic compound (6): the process steps of this example is identical to those of the example 2 except that the reactants used in this example includes 11.0 g (36.03 mmol) of organic compound (5), 4.49 g (18.02 mmol) of cobalt acetate, 6.06 g (73.86 mmol) of NaOAc and 110 ml of methanol. Thus, 10.75 g of brown precipitate of organic compound (6) with a yield of 84% was obtained.
Synthesis process for the organic dye compound (I-02) is described. The process steps of this example is identical to those of the example 3 except that the reactants used in this example includes 3.5 g (4.91 mmol) of organic compound (6), 4.77 g (9.81 mmol) of cyanine complex (3) and 35 ml of methanol. Thus, 2.95 g of organic dye compound (I-02) with a yield of 58% was obtained. The organic dye compound (I-02) has λmax=457 nm and ∈=61,602.
The reaction scheme of synthesis of the organic dye compound (I-02) is presented as follows.
In the embodiments 1 and 2, cyanine (3) replaces Na+ of the compounds (2) and (6), so as to obtain the compounds (I-01) and (I-02). Similarly, the following cation can replace Na+ of the compounds (2) and (6) to obtain different products.
In the above formula, R6 represents hydrogen, straight or branched C1-8 alkyl, C1-3 alkoxyl, halogen, nitro, benzyl group or substituted benzyl group wherein a substituent thereof is C1-2 alkyl, C1-2 alkoxyl, halogen or nitro. The organic cation is known to persons skilled in the art. Please refer to JP62-104874 or U.S. Pat. No. 3,741,982.
The synthesis of the organic dye compound (I-10) is described below. The method and steps are the same as those in EXAMPLE 3 of EMBODIMENT 1, except that the reactants used in this embodiment include 1.0 g (1.4 mmole) of the organic compound (6) (obtained from EXAMPLE 5 of EMBODIMENT 2), 1.65 g (3.59 mmole) of the organic compound (7) and 50 ml of methanol. Accordingly, 1.8 g of organic dye compound (I-10) with a yield of 95% was obtained. The organic dye compound (I-10) has λmax=454 nm and ∈=66,918. The reaction scheme of synthesis of the organic dye compound (I-10) is presented as follows.
The organic compound (7) is known to persons skilled in the art. Please refer to JP62-104874 or U.S. Pat. No. 3,741,982.
Preferred examples of the organic dye compound (I) are shown below.
The following table shows various organic dye compound and their respective maximum absorbance and extinction co-efficient measured using absorption spectroscopy.
Information may be recorded on the recording layer comprising the organic dye compound (I) with good write characteristics and compatible with the write-once storage medium.
Hereinafter, a structure of a high density HD DVD-R recording medium according to an embodiment of the present invention will be described with reference to
Hereinafter, a structure of a high density blue-ray-R recording medium according to another embodiment of the present invention will be described with reference to
According to an embodiment of the present invention, the first substrate 200, the second substrate 210 and the cover layer 207 are preferably transparent to the laser beam. The material of the first substrate 200, the second substrate 210 and the cover layer 207 may be comprised of, for example but not limited to, glass or plastic materials. From various aspects, the plastic material is preferably used. The plastic material may be comprised of, for example but not limited to, polycarbonate (PC), polymethylmethacrylate (PMMA), polymer resins, glass, acryl resin, methacryl resin, vinyl acetate resin, vinyl chloride resin, nitro cellulose, polyethylene resin, polypropylene resin, polycarbonate resin, polyimide resin, epoxy resin, polysulfone resin metallocene based cyclic olefin copolymer (mCOC) or UV curing materials.
Among the plastic materials mentioned above, an injection molded polycarbonate resin substrate may of particular interest from the viewpoint of the high productivity, low cost and moisture resistance. The thickness of the first substrate 200 may be between 0.5 mm to 1.3 mm, more preferably about 0.6 mm. The first substrate 200, for example, comprises lands, or pre-curved pits or grooves with a track pitch of less than 0.4 μm. The lands, or pre-curved pits or grooves in the first substrate 200 are used to provide a signal surface for the laser tracking of the pick-up head of the laser. The thickness of the second substrate 210 may be between 0.5 mm to 1.3 mm, more preferably about 0.6 mm.
According to an embodiment of the present invention, the recording layer 202 of the present invention including an organic dye compound (I) is formed with a thickness in a range of about 0.6 mm. The recording layer 202 may be formed by employing well known thin-film-forming methods such as a spin coating method, a roller press method, a vacuum vapor deposition method, a sputtering method, a doctor blade method, a casting method, inkjet printing method or a dipping method. However, the spin coating method is preferred from the viewpoint of the productivity and cost. A 1.5 Wt. % solution of the organic dye compound (I) of the present invention in 2,2,3,3-tetrafluoropropanol may be prepared and used for spin coating the thin film recording layer 202. It should also be noted that other solvents such as alcohol, ketone, ether, chloroform or dichloromethane may also be used to make the dye solution for forming the thin film recording layer 202. Preferred examples of alcohol include 2,2,3,3-tetrafluoropropanol, methanol, ethanol, isopropanol, diacetonalchol (DAA), ether alcohol, trichloroethanol, 2-chloroethanol, octafluoropentanol or hexafluorobutanol. Preferred examples of ketone include acetone methyl isobutyl ketone (MIBK) or dimethyl-ethyl ketone (MEK). Preferred examples of ether include ethyl ether, propylene glycol monoethyl ether or tetrahydrofuran. Still other solvents such as propylene glycol monoethyl acetate, 3-hydroxy-3-methyl-2-butanone, chloroform, dichloromethane, 1-chlorobutane, dimethylformamide (DMF), dimethylacetamide (DMA), methylcyclohexane (MCH), chitin, cellulose ester, nitrocellulose, cellulose acetate, cellulose acetate butyrate, polyvinyl butyral may also be used for preparing the solution of organic dye compound (I).
According to an embodiment of the present invention, the reflective layer 204 may be comprised of, for example but not limited to, metals such as gold, silver, copper, aluminum or platinum, titanium or a alloy thereof, or equivalents thereof, which have high reflectance in the laser wavelength region to be employed. The reflective layer 204 may be formed using vacuum sputtering.
The dielectric layer 206 may be comprised of, for example but not limited to, ZnS—SiO2, ZnS, AlN, SiN or SiC. The cover layer 207 may be comprised of, for example but not limited to, UV curing materials or plastic materials. The cover layer 207 may be formed by spin coating, screen printing, thermal gluing or roller pressing.
The recording layer 202 of the optical recording medium of the present invention may be formed on one side of the first substrate 200. According to an embodiment of the present invention, multiple recording layers 202 may be also used for fabricating a multi-layer stacked optical recording medium structure with a view of further increasing the storage capacity of the optical recording medium.
Accordingly, the information may be recorded on the recording layer comprising the organic dye compound (I) of the present invention with a good write characteristics, and the compatibility with the write-once storage medium may be retained.
According to an embodiment of the present invention, the recording layer comprising the organic dye compound (I) exhibits absorption at wavelength within a range of 400 to 550 nm, and exhibit excellent recording properties, such as light resistance, light fastness, chemical and thermal stabilities. Accordingly, it is possible to record information on the recording layer employing a short wavelength laser source such as a 405 nm blue laser source.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention covers modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
This application is a continuation-in-part of a prior application Ser. No. 12/183,049, filed Jul. 30, 2008. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12183049 | Jul 2008 | US |
| Child | 12566619 | US |
