JPH11144313A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively enable high-density recording by a laser beam by laminating a recording layer, a reflection layer, a protective layer, an adhesive layer and an upper substrate in this order on a transparent substrate and incorporating a styryl based dyestuff having a specific relation with a hydrogen atom, alkyl group, sulfur atom, arom. ring group, etc., into this recording layer. SOLUTION: This substrate is provided thereon with the recording layer, the reflection layer and the protective layer in this order. The recording layer contains a stabilizer of the styryl based dyestuff expressed by formula I. Further, the stabilizer is one kind of the compd. selected from a group consisting of the complex of copper, the complex of nickel and arom. amine and is incorporated into the recording layer at 3 to 15 wt.% of the styryl based dyestuff. The substrate is formed to a transparent disk shape of a polycarbonate resin. The recording layer is provided with prescribed patterns of grooves, etc. The reflection layer is formed of Al, Au, etc., and the protective layer is formed of a UV curing, etc. Further, the adhesive layer of an org. system and the upper substrate of the same resin as the resin of the substrate are disposed thereon. The inexpensive high-density recording with the laser beam of a wavelength of 620 to 690 nm is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical recording medium on which information can be written by laser light, and more particularly to an optical recording medium suitable for high-density recording.

[0002]

2. Description of the Related Art Conventionally, when information is written on a writable optical recording medium using a laser beam, for example, a laser beam having a wavelength of 780 nm has been used. However, a laser beam having such a wavelength cannot achieve a sufficiently high recording density of an optical recording medium. Therefore, attempts have been made to increase the recording density by reducing the spot diameter of the laser beam by shortening the wavelength. Various improvements have also been made to recording materials for optical recording media in response to the shortening of the wavelength of laser light.

As recording materials for optical recording media, for example, cyanine dyes are widely used, and in particular, asymmetric cyanine dyes whose optical properties are easily adjusted are used. However, since asymmetric cyanine dyes are expensive, it has not been easy to manufacture an optical recording medium having high recording density at low cost.

Further, Japanese Patent Application Laid-Open Nos. 5-38878 and 5-305773 propose using a styryl dye as a recording material for an optical recording medium. When the styryl dye described in these publications is used as a recording material, it can be said that the recording wavelength of the optical recording medium becomes short because the maximum absorption wavelength of the styryl dye is in the first half of the order of 400 nm. However, in order to generate such a short-wavelength laser beam, it is necessary to use a large-sized laser beam generator such as an argon laser described in the above-mentioned publication, which is used in a normal recording / reproducing drive. It is presently difficult to generate such short wavelength laser light with a semiconductor laser. Therefore, the styryl dye was not a suitable recording material for high-density recording using laser light of 620 to 690 nm, which is a wavelength range generated by a semiconductor laser which is a practical laser light generator.

Accordingly, an object of the present invention is to provide a light source having wavelengths of 620 to 6
An object of the present invention is to provide an optical recording medium that can perform high-density recording with a 90-nm laser beam and can be manufactured at low cost.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an optical recording medium which can achieve the above object can be obtained by using a styryl dye having a specific structure as a recording material. .

The present invention has been made based on the above findings. In an optical recording medium having at least a recording layer, a reflective layer and a protective layer provided in this order on a substrate, the recording layer is represented by the following formula (I). The object has been achieved by providing an optical recording medium characterized by containing a styryl dye represented by the formula (1).

[0008]

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Further, the present invention provides the optical recording medium, wherein the recording layer further comprises the styryl dye stabilizer, thereby improving the stability of the recording layer. It is a thing.

Further, the present invention provides the optical recording medium, wherein the stabilizing agent is at least one compound selected from the group consisting of a copper complex, a nickel complex and an aromatic amine. 3 to 15 for
By providing an optical recording medium containing 0.1% by weight, the stability of the recording layer is improved.

Further, the present invention provides the above optical recording medium, wherein the optical recording medium has an upper substrate laminated on the protective layer via an adhesive layer, whereby the mechanical strength of the optical recording medium is reduced. It is enhanced.

Further, the present invention provides the optical recording medium, wherein the optical recording medium has two sets of one-side recording sections each including the substrate, the recording layer, the reflective layer, and the protective layer. An optical recording medium of a double-sided recording system is provided by providing an optical recording medium integrally formed by joining the two via the adhesive layer with the protective layer side facing each other.

Further, the present invention provides an optical recording medium in which information is recorded by a laser beam having a wavelength of 620 to 690 nm in the above optical recording medium.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical recording medium according to the present invention will be described based on preferred embodiments with reference to the drawings.
Here, FIG. 1 is a schematic diagram showing the configuration of an embodiment of the optical recording medium of the present invention.

The optical disk 1 shown in FIG. 1 has a recording layer 3, a reflective layer 4, a protective layer 5, an adhesive layer 6, and an upper substrate 7 laminated in this order on a substrate 2 transparent to a laser beam to be used. It has been formed.

The substrate 2 is preferably made of a material that is transparent to the laser beam to be used, for example, a resin or glass. Particularly, the substrate 2 is made of a resin because it is easy to handle and inexpensive. preferable. Specifically, for example, a polycarbonate resin, an acrylic resin, an epoxy resin, an ABS resin, or the like can be used as the resin. The shape and dimensions of the substrate 2 are not particularly limited, and are usually disk-shaped, and the thickness is usually 0.5 to 3 m.
m and the diameter is about 40 to 360 mm. On the surface of the substrate 2 on the recording layer 3 side, a predetermined pattern 8 such as a group is provided as needed for tracking, addressing, and the like.

The reflection layer 4 is formed for the purpose of improving the reflectivity of laser light and the sensitivity during recording. As a material constituting the reflection layer 4, a material having a high reflectance with respect to a laser beam to be used and a high corrosion resistance is preferably used. Such materials include, for example, A
Metals containing l, Au or Ag as a main component are exemplified. The thickness of the reflection layer 4 is usually about 50 to 150 nm. The reflective layer 4 is formed on the recording layer 3 directly or via another layer by various vapor deposition methods such as a vacuum deposition method, a sputtering method, an ion plating method, a plasma CVD method, a photo CVD method, and an electron beam deposition method. Can be formed by

The protective layer 5 is formed for the purpose of physically and chemically protecting the recording layer 3 and the reflective layer 4.
The protective layer 5 is preferably made of a hard material such as a thermoplastic resin or an acrylic ultraviolet curable resin. The thickness of the protective layer 5 is usually about 2 to 20 μm.

The adhesive layer 6 is desirably composed of various organic substances, particularly, a thermoplastic substance, a tacky substance, a radiation-curable compound or a substance obtained by curing a composition thereof with an electron beam or radiation. Preferably.
The thickness of the adhesive layer 6 is usually about 0.1 to 100 μm. The adhesive layer 6 is formed by an optimal forming method selected according to the constituent material, for example, spin coating, gravure coating, spray coating, roll coating, or the like. Also,
The upper substrate 7 can be made of the same resin as the substrate 2 described above. The thickness of the upper substrate 7 is the same as the thickness of the substrate 2 described above. By laminating the upper substrate 7, the mechanical strength of the obtained optical recording medium is improved.

Thus, in the optical recording medium of the present invention,
The recording layer 3 contains a styryl dye represented by the above formula (I).

The styryl dye represented by the above formula (I) will be described in detail. The styryl dye constitutes a zwitter ion having both an anionic group and a cationic group in a molecule.

In the above formula (I), the alkyl group represented by R ₁ may be linear or branched, and preferably has 1 carbon atom.
-12, and more preferably 2-6. Particularly preferred alkyl groups are an ethyl group, an n-propyl group, an n-butyl group, a 1- (3-methylbutyl) group and the like.

In the above formula (I), the alkyl group represented by R ₂ may be linear or branched, and preferably has 1 carbon atom.
To 6, and more preferably 1 to 3. Also, R ₂
As the alkyl group in the alkoxyl group represented by R ₁ , the same as the alkyl group represented by R ₁ can be used.

As the halogen group represented by R ₂ , a chlorine group or a fluorine group is preferably used.

The NHR ^a group and NR ^b R represented by R ₂
R ^a group in the ^c group, R ^b group, R ^c groups (they are both an alkyl group) may be linear or branched, the preferred number of carbon atoms is 1 to 6, more preferably 1 to 3 It is. Particularly preferred alkyl groups are a methyl group, an ethyl group and the like. The R ^b group and the R ^c group may be the same or different. Particularly preferred examples of the NHR ^a group include a methylamino group and an ethylamino group. On the other hand, particularly preferred examples of the NR ^b R ^c group include a dimethylamino group and a diethylamino group.

Of the above-mentioned various groups represented by R ₂ ,
Preferred groups are a hydrogen atom, an NR ^b R ^c group, and an alkoxyl group, and particularly preferred groups are a hydrogen atom and an NR ^b R ^c group.

The above-mentioned various groups represented by R ₂ may be bonded to any position of the aromatic ring group Z.

In the above formula (I), the alkyl group, alkoxy group and halogen group represented by R ₃ are the same as the corresponding groups represented by R ₂ . Accordingly, these groups are not particularly described, but the detailed description of the corresponding groups represented by R ₂ is applied as appropriate.

Of the above-mentioned various groups represented by R ₃ ,
Preferred groups are a hydrogen atom, an alkyl group, an alkoxyl group, and a halogen group, and particularly preferred groups are a hydrogen atom, an alkoxyl group, and a halogen group.

The above-mentioned various groups represented by R ₃ may be bonded to any position on the benzene ring.

In the above formula (I), Z represents an aromatic ring group,
Preferably, a benzene ring group or a naphthalene ring group is used.

In the above formula (I), CR represented by Y^dR^e
R in the group^dGroup and R^eGroup (these are all
R) is the above-mentioned R^aGroup, R^bGroup and
R^cThe same as the groups are used. Therefore, these groups
Is not specifically described, but R^aGroup, R^bGroup and R
^cThe details described for the groups apply where appropriate. Note that R ^d
And R^eMay be the same or different.

Of the various groups represented by Y, the preferably used groups are a sulfur atom and an oxygen atom, and the particularly preferably used group is a sulfur atom.

[0034] In the above formula (I), as a minus monovalent group represented by X, -O ^- group, -COO ^- group, -SO ₄ ^-
And the like, and particularly preferably an -O ^- group.

Of the styryl dyes represented by the above formula (I), those preferably used are the following formulas (Ia) to (Ia).
c).

[0036]

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[0037]

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[0038]

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The styryl dyes are generally selected from Witti.
It is synthesized from the corresponding bromine compound and aldehyde by the g reaction.

The recording layer 3 may be composed solely of the styryl dye or may contain various additives in addition to the styryl dye. As such an additive, at least one compound selected from the group consisting of a copper complex, a nickel complex, and an aromatic amine, which are stabilizers for improving the light stability of the styryl dye, is preferably used. Such a compound has an effect of improving the light resistance and the like of the styryl dye, and is preferably contained in an amount of 3 to 15% by weight, more preferably 3 to 8% by weight, based on the styryl dye. If the content of the compound is less than 3% by weight, the light stability of the styryl dye may decrease, and if it exceeds 15% by weight, the sensitivity at the time of recording may decrease. Is preferred.

As the copper complex used as the stabilizer, for example, a copper ammonium complex such as bis (4-tert-butyl-1,2-dithiophenolate) copper-tetra-n-butylammonium is used. Is preferred. Examples of nickel complexes include, for example, bis (4-tert
It is preferable to use a nickel ammonium complex such as -butyl-1,2-dithiophenolate) nickel-tetra-n-butylammonium.

The recording layer 3 is formed by preparing a coating solution by dissolving the styryl dye and, if necessary, the additive in a solvent, and applying the coating solution onto the substrate 2. As a solvent for preparing the coating liquid, for example, a fluorine-containing alcohol, cellosolve, carbon halide,
Organic solvents such as ketones and ethers are used, and fluorine-containing alcohols such as 2,2,3,3-tetrafluoropropanol are preferably used. The concentration of the styryl dye in the coating solution is generally 1 to 4% by weight.
It is about. As a method for applying the coating liquid, a spin coating method is preferably used because a uniform thin layer can be easily formed.

The thickness of the recording layer 3 is appropriately selected in consideration of the recording sensitivity to laser light, the coefficient of performance, and the like, according to the wavelength to be used, the optical properties of the reflective layer 4, and the like.
It is about 150 nm.

As a specific application example of the optical recording medium of the present invention, a write-once type optical disk (for example, DVD-
R).

As described above, the optical recording medium of the present invention has been described based on the preferred embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention. . For example, as shown in FIG. 2, instead of the optical recording medium of the present invention having the configuration shown in FIG. 1, one-sided recording comprising a substrate 2, a recording layer 3, a reflective layer 4, and a protective layer 5, as shown in FIG. Recording unit 1 having two sets of
The two-sided recording system is configured such that the protective layers 0 and 10 are opposed to each other and bonded together via an adhesive layer 6 to form a double-sided recording system, or as shown in FIG. Therefore, a configuration in which the adhesive layer 6 and the upper substrate 7 are omitted from the configuration may be adopted. Further, between the recording layer 3 and the substrate 2 or the reflection layer 4,
If necessary, a layer for improving various performances of the optical recording medium may be provided. The surface of the reflective layer 4 on the side of the protective layer 5 may be subjected to a surface treatment with a surface treating agent such as a triazine thiol-based compound.

[0046]

The present invention will be described in more detail with reference to the following examples and the effectiveness thereof will be illustrated. However, the scope of the present invention is not limited to such an embodiment.
In the following examples, "%" means "% by weight" unless otherwise specified.
Means

Example 1 A disc-shaped substrate having a diameter of 120 mm and a thickness of 0.6 mm was molded from polycarbonate as a raw material. On one surface of this substrate, a groove width of 0.3 μ
A straight groove having a depth of 0.14 μm and a length of 0.1 m is formed. A styryl dye having a structure represented by the above formula (Ic) is dissolved in 2,2,3,3-tetrafluoropropanol, and further insoluble matter is removed through a filter.
A coating solution having a concentration of 2% was prepared. This coating solution was spin-coated on the surface of the substrate on which the grooves were formed to form a coating film. This coating film was dried at 80 ° C. for 1 hour to form a recording layer having a thickness of 120 nm. On this recording layer, a reflective layer made of aluminum and having a thickness of 100 nm was formed by sputtering. Further, on the reflective layer, a UV-curable resin SD-1700 (manufactured by Dainippon Ink and Chemicals, Inc.) is spin-coated to form a coating film.
Was formed. Further, a polycarbonate substrate having the same shape and the same size as the above-mentioned substrate was laminated on the protective layer via an adhesive. Thus, an optical disk having the structure shown in FIG. 1 was manufactured.

The reflectivity and the degree of modulation of the thus obtained optical disc in an unrecorded state were measured by using a pulse-tech DD
The measurement was performed at a wavelength of 639 nm of laser light using U-1000. As a result, the reflectance was 58%, and the linear velocity was 3.8.
When a 10T signal was written under the conditions of 4 m / sec and a recording power of 11 mW, the degree of modulation was 62%, which was a good result.

Example 2 A styryl dye having a structure represented by the above formula (Ic) and bis (4-tert-butyl-1,2-dithiophenolate) copper-tetra-n-butylammonium (stable Agent) was dissolved in 2,2,3,3-tetrafluoropropanol, and the insoluble matter was removed through a filter to prepare a coating solution having a dye concentration of 2% and a stabilizer concentration of 0.2%. An optical disc was produced in the same manner as in Example 1 except that a recording layer was formed using this coating solution. When the reflectance and the degree of modulation of the obtained optical disk in the unrecorded state were measured in the same manner as in Example 1, the reflectance was 55%, and the degree of modulation when a 10T signal was written was 61%. Almost the same results as in Example 1 were obtained.
When the optical disk was irradiated with ultraviolet light of 500 mW / m ² by using a xenon light-fastness tester manufactured by Heraeus, the light resistance was improved three times as compared with the optical disk obtained in Example 1. I understood.

Comparative Example 1 In place of the styryl dye used in Example 1, a styryl dye NK-1977 [3,3] described in Examples of JP-A-5-33878 was used.
-Dimethyl-2- (4'-dimethylaminostyryl) indolenin] (manufactured by Nippon Kosaku Dye Laboratories), except that an optical disc was produced in the same manner as in Example 1. When the reflectance and the degree of modulation in the unrecorded state of the obtained optical disk were measured in the same manner as in Example 1, the reflectance was 38%.
The degree of modulation when writing a 10T signal is 5% or less,
It was found that this styryl dye was not suitable for recording using a laser beam having a wavelength of 639 nm.

[0051]

As described above, according to the present invention,
An optical recording medium that can be recorded at high density with laser light having a wavelength of 620 to 690 nm and that can be manufactured at low cost is obtained.
In particular, by using the styryl dye in combination with a stabilizer, light resistance and the like are also improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an embodiment of an optical recording medium of the present invention.

FIG. 2 is a schematic diagram showing a configuration of another embodiment of the optical recording medium of the present invention.

FIG. 3 is a schematic diagram showing the configuration of another embodiment of the optical recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical recording medium 2 Substrate 3 Recording layer 4 Reflective layer 5 Protective layer 6 Adhesive layer 7 Upper substrate 10 One-side recording part

Claims (6)

[Claims] 1. An optical recording medium comprising a substrate provided with at least a recording layer, a reflective layer and a protective layer in this order, wherein the recording layer contains a styryl dye represented by the following formula (I). An optical recording medium characterized by the above-mentioned. Embedded image 2. The optical recording medium according to claim 1, wherein the recording layer further contains the styryl dye stabilizer. 3. The stabilizer is at least one compound selected from the group consisting of a copper complex, a nickel complex and an aromatic amine, and is contained in an amount of 3 to 15% by weight based on the styryl dye. The optical recording medium according to claim 2, wherein 4. The optical recording medium according to claim 1, further comprising an upper substrate laminated on said protective layer via an adhesive layer. 5. A two-sided recording unit including the substrate, the recording layer, the reflective layer, and the protective layer, the two recording units each including:
The optical recording medium according to any one of claims 1 to 3, wherein the protective layer side of each one-side recording portion is opposed to each other, and the two are joined together via an adhesive layer to be integrally formed. 6. The optical recording medium according to claim 1, wherein information is recorded by a laser beam having a wavelength of 620 to 690 nm.