JP2000343819A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DVD-R optical recording medium for obtaining good signal characteristics in wavelengths of both 635 and 650 nm. SOLUTION: In the optical recording medium comprising at least a substrate, a recording layer and a reflecting layer, the recording layer contains an organic material for constituting a film having optical constants of a wavelength of 635 nm of 2.6>n>2.0, 0.08>=k and an organic material for constituting a film having optical constants of a wavelength of 635 nm of 2.8>n>2.0, 0.5>k>=0.1 as main components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical recording medium.

[0002]

2. Description of the Related Art In recent years, DVDs have attracted attention as high-density information recording media used for recording and reproducing images and sounds. As a recordable medium for DVD, DVD-R
AM, DVD-R, DVD-RW, DVD + RW, and the like have been developed. Among them, DVD-R allows a user to record information, and a signal after recording satisfies the DVD standard. There is an advantage that it can be reproduced by a commercially available DVD player.

[0003] As a method for creating the above-mentioned media, a method similar to that for a CD-R can be used. That is,
A recording layer is provided by spin coating a dye on the substrate,
It has been proposed to provide a metal reflective layer behind it (Japanese Patent Laid-Open No. 10-044606). However,
This information recording medium cannot be recorded with a DVD laser wavelength. In DVD-R, 635 is used as the recording / reproducing wavelength.
nm and 650 nm are used. Usually, the wavelength of the recording / reproducing light is 635 nm, and the wavelength of the reproducing-only light is 650 n.
m is used. Therefore, in DVD-R, the above 2
It is necessary to ensure characteristics at the wavelength.

However, the dye layer used in DVD-Rs has a large wavelength dependence in a laser light wavelength range, and 635 n
It was difficult to balance the characteristics at both the wavelengths of m and 650 nm. That is, the optical characteristics (n, k) of the dye layer that affect the recording / reproducing signal tend to change depending on the light wavelength. For example, when 635 nm is used as the recording / reproducing light wavelength, there is a problem that a reproducing error occurs at 650 nm even if recording / reproducing is good.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a DVD-R optical recording medium capable of solving the above-mentioned problems and obtaining good signal characteristics at both wavelengths of 635 nm and 650 nm. . That is, an object of the present invention is to provide an information recording medium capable of recording / reproducing at a DVD laser wavelength and reproducing at 650 nm.

[0006]

The optical recording medium of the present invention comprises:
The problem was solved by using two types of organic materials having specific optical characteristics. That is, by using the organic materials (1) and (2) having the following specific optical characteristics in combination, good signal characteristics can be obtained at both the wavelengths of 635 nm and 650 nm.

As one of the recording layers of the optical recording medium of the present invention composed of a combination of the organic materials (1) and (2), the optical constant at a wavelength of 635 nm is 2.6>n> 2.
0, 0.08 ≧ k, the organic material (1) constituting the film and the optical constant at a wavelength of 635 nm are 2.8>n> 2.0,
Organic material constituting a film satisfying 0.5> k ≧ 0.1 (2)
Which are mainly composed of

[0008] As another recording layer of the optical recording medium of the present invention composed of a combination of the organic materials (1) and (2),
The optical constants at a wavelength of 650 nm, 2.4>n> 1.8, 0.
Organic material (1) constituting a film satisfying 04 ≧ k and wavelength 65
The optical constant at 0 nm is 2.6>n> 1.8, 0.2> k
A film mainly composed of the organic material (2) constituting the film satisfying ≧ 0.05 is exemplified.

The organic materials (1) and (2) can be mixed or laminated to form a recording layer. It is preferable that the ratio of the organic material (2) / (1) in the recording layer is 3 to 20% by weight. When the amount of the organic material (1) is larger than the above range, the wavelength dependency is increased, and it is difficult to obtain the effects of the present invention. On the contrary, when the amount of the organic material (1) is reduced,
Various signal intensities, such as reflectance, fall because absorption becomes large.

Specific examples of the organic dye material having specific optical characteristics according to claims 1 to 3 include, for example, a cyanine dye, an azo dye, a tetraazaporphyrazine dye, a porphyrin dye, a pyrylium / thiopyrylium dye. Dye, azulenium dye, squalilium dye, N
i, Cr and other metal complex dyes, naphthoquinone / anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, phthalocyanine dyes, aluminum / diimmonium dyes, etc. Can be mentioned.

The organic material (1) has a light absorption peak wavelength (λ) in a methanol solution of 580 nm>λ> 5.
50 nm, and the organic material (2) has a light absorption peak wavelength (λ) of 610 nm>λ> 58 in a methanol solution.
A film having a main component of 0 nm is preferable because it is easy to adjust n and k of the film.

Particularly, the organic material (1) is an asymmetric trimethine cyanine dye represented by the following general formula (1), and the organic material (2) is a symmetrical dye represented by the following general formula (2). By using a trimethine cyanine dye, an organic dye material that satisfies the optical characteristics specified in claims 1 to 3 can be easily obtained.

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The optical recording medium of the present invention will be specifically described below.

Recording Layer For the recording layer, the above-mentioned organic dye materials are used, and these dyes may further contain other third components, if necessary, such as a light quencher, a binder, a radical scavenger, and a stabilizer. Etc. can be contained. The thickness of the recording layer is 1
The range is preferably from 00 to 5000 °.

Substrate The substrate used in the present invention can be arbitrarily selected from various materials used as a base of a conventional information recording medium. Examples of substrate materials include acrylic resins such as polymethyl methacrylate, polyvinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer, epoxy resins, polycarbonate resins, amorphous polyolefin, polyester, and glass such as soda-lime glass. And ceramics. In particular, polymethyl methacrylate, polycarbonate resin, epoxy resin, amorphous polyolefin, polyester, glass and the like can be mentioned from the viewpoint of dimensional stability, transparency and flatness.

Undercoating layer On the substrate surface on which the recording layer is provided, the flatness is improved,
An undercoat layer may be provided for the purpose of improving adhesion and preventing deterioration of the light absorbing layer. As a material of the undercoat layer, for example, polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide,
Styrene / sulfonic acid copolymer, styrene / vinyltoluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin,
High-molecular substances such as polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl chloride copolymer, polyethylene, polypropylene, and polycarbonate: organic substances such as silane coupling agents: inorganic oxides (SiO ₂ , Al ₂ O ₃ etc.), inorganic fluorides (Mg
And inorganic substances such as F ₂ ). The thickness of the undercoat layer is generally 0.005 to 20 μm, preferably 0.05 to 20 μm.
1 to 10 μm.

A pre-group layer may be provided on the substrate (or undercoat layer) for the purpose of forming tracking grooves or irregularities representing information such as address signals. As the material of the pre-group layer, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetramonoester and a photopolymerization initiator can be used.

Reflective Layer A reflective layer is provided on the recording layer for the purpose of improving the S / N ratio, the reflectance, and the sensitivity during recording. The light-reflective substance that is the material of the reflection layer is a substance having a high reflectance with respect to laser light, and examples thereof include Mg, Se, Y, and T.
i, Zr, Hf, V, Nb, Ta, Cr, Mo, W, M
n, Re, Fe, Co, Ni, Ru, Rh, Pd, I
r, Pt, Cu, Ag, Au, Zn, Cd, Al, C
a, In, Si, Ge, Te, Pb, Po, Sn, Si
And metal and semimetals. These substances may be used alone, or may be used in combination of two or more kinds or as an alloy. The thickness of the reflective layer is generally in the range from 100 to 3000 °.

Protective Layer A protective layer may be provided on the recording layer (or reflective layer) for the purpose of physically and chemically protecting the recording layer and the like.
This protective layer may be provided on the side of the substrate where the light absorbing layer is not provided, for the purpose of improving the scratch resistance and the moisture resistance. Examples of the material used for the protective layer include SiO, Si
Examples include inorganic substances such as O ₂ , MgF ₂ , and SnO ₂ , thermoplastic resins, thermosetting resins, and UV-curing resins. The thickness of the protective layer is generally 500 ° to 50 μm.
In the range.

Next, a method for manufacturing the optical recording medium of the present invention will be described. The optical recording medium of the present invention can be manufactured, for example, as follows. A recording layer mainly containing the organic dyes (1) and (2) is provided by a coating film forming means directly or via another layer on a substrate having information pits and / or guide grooves formed on the surface. After a light reflecting layer is formed thereon directly or through another layer by a sputtering film forming method, and a disk body having a protective layer formed thereon is further formed, two disk bodies are recorded with an adhesive layer. Laminate with layers inside.

The optical recording medium manufacturing method comprises the following steps. (A) A step of forming a recording layer made of an organic dye on a substrate having information pits and / or guide grooves formed on its surface, directly or through another layer by a coating film forming means (recording layer forming step). (B) A step of forming a light reflecting layer on the recording layer directly or via another layer by sputtering (recording forming step). (C) A step of providing a protective layer on the light reflecting layer (light reflecting layer forming step).

Recording Layer Forming Step A dye material is dissolved in a solvent, directly or through another layer, on a substrate having information pits and / or guide grooves formed on the surface thereof. By coating, a recording layer is formed. As a solvent for preparing this coating solution, a known organic solvent (for example, alcohol, cellosolve, halogenated carbon, ketone, ether, etc.) can be used. Examples of the means for forming the organic recording layer include a vapor deposition method, a dip coating method, and a spin coating method.However, since the layer thickness can be controlled by adjusting the concentration of the recording layer, the viscosity, and the drying temperature of the solvent, the spin coating method is used. Law is preferred. The provision of an undercoat layer on the surface of the substrate on which the recording layer is provided is performed for the purpose of improving the flatness of the substrate surface, improving the adhesive strength, preventing the recording layer from being deteriorated, and the like. In this case, the undercoat layer is prepared by, for example, dissolving or dispersing the aforementioned undercoat layer material in an appropriate solvent to prepare a coating solution, and then spin coating, dip coating,
It can be formed by applying to the substrate surface by an application method such as an extruder coat.

Light Reflecting Layer Forming Step Next to the recording layer forming step, a light reflecting layer is provided on the recording layer directly or via another layer by a vacuum film forming method. Examples of the forming means include a vapor deposition method, an LB method, and a sputtering method, and a sputtering method (particularly, a single-wafer sputtering method) having a high film-forming speed and a short tact time is preferable.

Protective Layer Forming Step A protective layer is formed on the light reflecting layer. That is, the protective layer material is formed by vacuum film formation or coating film formation of the protective layer material made of the above-mentioned inorganic substance or various resins. In particular, it is preferable to use a UV-curable resin. The resin is formed by spin-coating the resin and then irradiating it with ultraviolet light.

[0025]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Practical example 1 On a surface of a polycarbonate disc having a diameter of 120 mm and a thickness of 0.6 mm, a depth of about 1700 ° and a track pitch of 0.
Prepare a substrate having a guide groove uneven pattern of 74 μm,
As the organic material (1), an asymmetric trimethinecyanine dye represented by the general formula (1) (R ₁ : CH ₃ , R ₂ :
CH ₃ , Y: CH ₃ , X: BF ₄ ) (A), and a symmetric trimethine cyanine dye represented by the general formula (2) (R ₁ : CH ₃ , R ₂ : CH) represented by the general formula (2) as the organic material (2) ₃ , X:
ClO ₄ ) (B) was dissolved in a mixed solvent of 2,2,3,3-tetrafluoropropanol and 2-ethoxyethanol at a ratio of 1: 1 and the recording layer was formed by spin-coating the mixed solvent as a coating liquid. Was. The thickness of the light absorbing layer is about 15
It was 00 $. The ratio of the organic materials (1) and (2) was (2) / (1) = 10% by weight. (1),
The optical constant of (2) in MeOH was as shown in Table 1 below. 1 and 2 show the spectrum.

[0026]

[Table 1]

Next, Ag was applied to a thickness of about 1400 ° on the recording layer by sputtering using Ar as a sputtering gas to form a reflective layer. Further, a protective layer made of an ultraviolet curable resin is provided thereon at a thickness of about 5 μm to form a disk body, and the two sheets are laminated with a hot melt adhesive,
A DVD-R optical recording medium of the present invention was obtained.

This medium has a wavelength of 635 nm and an NA of 0.2.
6. Basic DVD with a linear velocity of 3.49 m / s
(8-16) The signal was recorded. Recording strategy is 3T
top: 1.1T, 4T to: 1.05T, Tmp: 0.
63. The recorded signal was reproduced using a recording / reproducing optical system having a wavelength of 635 nm and a reproducing optical system having a wavelength of 650 nm and NA of 0 and 6, and the clock jitter and asymmetry were measured. And good characteristics were obtained. The optical properties of the dye material
The results are shown in Table 3 below.

[0029]

[Table 2]

Example 2 In Example 1, the following Table 3 was used instead of the dye material (A).
In Table 3 below, the dye material of (C) and the dye material (B) were replaced.
The procedure was performed in the same manner as in Example 1 except that the dye material (D) was used. The results are as shown in Table 2 above.
Good characteristics were obtained without change at 35 nm and 650 nm. The optical properties of the coloring material were as shown in Table 3 below.

Example 3 In Example 1, the following Table 3 was used instead of the dye material (A).
The same evaluation as in Example 1 was performed except that (E) was used. The results are as described in Table 2 above, and 635 nm,
Good characteristics were obtained at 650 nm without any change. The optical properties of the dye material were as shown in Table 3 below.

Example 4 The same evaluation as in Example 1 was performed, except that an azo dye represented by the following general formula (F) was used in place of the dye material (A). The results are as shown in Table 2 above, and 63
Good characteristics were obtained without change at 5 nm and 650 nm.
The optical properties of the dye material were as shown in Table 3 below.

[0033]

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[Table 3]

Comparative Example 1 A DVD-ROM of Comparative Example 1 was prepared in the same manner as in Example 1 except that the recording layer was formed using only the dye material (A).
An R optical recording medium was prepared and evaluated. The results are as shown in Table 2 above. The characteristics at 635 nm are good, but 650 nm.
Now the jitter value has increased. Furthermore, the asymmetry value also changed between 635 nm and 650 nm, resulting in a large signal wavelength dependence. The optical properties of the dye material
As shown in Table 3 above.

[0035]

[Effect] 1. Claims 1 and 2 The recording / reproducing light wavelength dependency is small, and good signal characteristics are obtained at wavelengths of 635 nm and 650 nm. 2. Claims 3 and 4 Since the recording layer is made of two kinds of organic materials having specific light absorption characteristics, the characteristics of claims 1 and 2 are easily obtained. 3. (5) Since the dye ratio in the recording layer is optimized, a greater effect can be obtained on reducing the wavelength dependence of recording / reproducing light.

[Brief description of the drawings]

FIG. 1 is a spectrum diagram of an organic material (1) of Example 1.

FIG. 2 is a spectrum diagram of an organic material (2) of Example 1.

Claims (5)

[Claims] 1. An optical recording medium comprising at least a substrate, a recording layer and a reflective layer, wherein the recording layer has an optical constant of 2.6>n> 2.0, 0.0 at a wavelength of 635 nm.
Organic material (1) constituting a film satisfying 8 ≧ k and wavelength 635
The optical constant in nm is 2.8>n> 2.0, 0.5> k ≧
An optical recording medium comprising an organic material (2) constituting a film having a thickness of 0.1 as a main component. 2. An optical recording medium comprising at least a substrate, a recording layer and a reflective layer, wherein the recording layer has an optical constant of 2.4>n> 1.8, 0.04 at a wavelength of 650 nm.
Organic material (1) constituting the film satisfying ≧ k and wavelength 650 n
The optical constant at m is 2.6>n> 1.8, 0.2> k ≧
An optical recording medium comprising an organic material (2) constituting a film having a thickness of 0.05 as a main component. 3. An organic material (1) having a light absorption peak wavelength (λ) in a methanol solution of 580 nm>λ> 550 nm,
The organic material (2) has a light absorption peak wavelength (λ) of 610.
The optical recording medium according to claim 1, wherein nm>λ> 580 nm. 4. An asymmetric trimethine cyanine dye represented by the following general formula (1), wherein the organic material (1) is represented by the following general formula (1), and a symmetric trimethine cyanine dye represented by the following general formula (2): The optical recording medium according to claim 1, wherein Embedded image Embedded image (Wherein, R ₁ , R ₂ , R ₃ , and R ₄ each independently represent a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, or a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms. Represents a group, Y
Represents hydrogen, halogen, NO ₂ , a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, or a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms. X is I, Cl, ClO
₄ , BF ₄ , and SbF ₆ ) 5. The ratio of the organic materials (1) and (2) is
5. The optical recording medium according to claim 1, wherein (2) / (1) is 3 to 20% by weight.