JP3435481B2 - Optical recording medium and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having improved optical characteristics and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, the development of a write-once CD (compact disc) has become active. This is a conventional CD
Unlike a CD, a user can record information and the signal after recording satisfies the standard of the conventional CD, so that a commercial CD
It has the feature that it can be played back by the player. As one of methods for realizing such a medium, Japanese Patent Laid-Open No. 2-4
In Japanese Patent No. 2652, it is proposed that a dye is spin-coated on a substrate to provide a light absorption layer, and a metal reflection layer is provided behind it. Furthermore, Japanese Patent Laid-Open No. 2-13
As described in Japanese Patent No. 2656, by appropriately selecting the complex refractive index and the film thickness of the light absorption layer, the signal after recording satisfies the CD standard, and a write-once CD can be realized.

[0003]

However, Japanese Unexamined Patent Application Publication No.
The write-once type CDs using the dyes disclosed in JP-A-42652 and JP-A-2-132656 are still insufficient in light resistance. In other words, the signal characteristics change when exposed to sunlight for a long time, and the CD
There is a drawback that the standard cannot be satisfied. This is because the dye material used for the light absorption layer, particularly the cyanine dye that has been used conventionally, changes due to light. Therefore, in order to suppress this change, JP-A-63-63
It is known to contain a light stabilizer in the light absorption layer as disclosed in Japanese Patent Publication No. 159090. But,
When the light stabilizer is added in a small amount (20% or less), sufficient light resistance cannot be obtained, and conversely, when added in a large amount (20% or more), the optical and / or heat of the light absorption layer is not increased. However, there has been a problem that various characteristics are changed and various signal qualities are deteriorated.

On the other hand, as another means for improving the light resistance,
It has also been proposed to use a phthalocyanine compound, which is a highly light-resistant dye, as a material for the light-absorbing layer (JP-A-58-18).
Nos. 3296 and 58-37851). But,
It has been difficult for the phthalocyanine compound to satisfy the optical characteristics required for the light absorption layer, particularly the high refractive index.
The optical characteristics of the light absorption layer depend on the extinction coefficient (which means the absorbance per unit film thickness) of the film in the vicinity of the laser light wavelength for recording and reproduction, and satisfy the optical characteristics required for the write-once CD. In order to achieve this, a certain degree of extinction coefficient is required, but in general, a film of a phthalocyanine compound has a smaller extinction coefficient than that of a conventional cyanine dye (about 1/3 to 1/2 of cyanine dye). It depends.

Therefore, an object of the present invention is to provide an optical recording medium having a light absorbing layer having high light resistance and required optical characteristics, and more specifically, a specific phthalocyanine compound having improved optical characteristics. The present invention provides an optical recording medium having the film as a light absorbing layer, and a method for manufacturing the same.

[0006]

As a result of earnest studies, the inventors of the present invention have found that in the above-mentioned conventional optical recording medium, the light absorption layer of the phthalocyanine compound has a small absorption coefficient. The molecule of the compound has a planar structure and is likely to undergo molecular association. When the molecule of the phthalocyanine compound is associated, the light absorption spectrum becomes broad due to the intermolecular interaction. Furthermore, in the phthalocyanine compound, the laser light wavelength range ( 760-800
In order to obtain an appropriate complex refractive index in (nm), it was found that the absorption peak wavelength (λmax) of the light absorption layer is more preferably in the range of 710 to 750 nm, and the present invention has been completed.

[0007] That is, according to the present invention, in an optical recording medium formed by providing at least a light-absorbing layer on a substrate, a metal phthalocyanine compound light absorbing layer is represented by the following formula (I), substitution of An optical recording medium comprising a nitrogen-containing compound selected from an imidazole-based compound which may be contained as a main component.

[Chemical 2] (In the formula, M and A ^{1 to} A ⁸ each represent the following. M: Mn, Fe, Co, Zn or Cd atom. A ¹ and A ² , A ³ and A ⁴ , A ⁵ and A ⁶ And A ⁷ and A ⁸ : one of them is an —OR or —SR group, and the other is a hydrogen atom.
R: an optionally substituted aromatic or alicyclic hydrocarbon group. )

Further, according to the present invention , the light absorption layer is provided with 710
Provided is an optical recording medium having a light absorption peak wavelength (λmax) in the range of ˜750 nm.

Furthermore, according to the present invention, a metal phthalocyanine compound represented by the above general formula (I) is directly or via another layer on a substrate having information pits and / or guide grooves formed on the surface thereof. If, optionally substitution imidazo
Of a nitrogen-containing compound selected from the group-based compounds is provided as a main component by a coating and film-forming means, and a light-reflecting layer is provided thereon by a vacuum film-forming means directly or through another layer. Further, there is provided a method for manufacturing an optical recording medium, which further comprises a protective layer provided thereon.

The optical recording medium of the present invention has the above general formula (I).
Since a light absorption layer containing a mixture of a metal phthalocyanine compound represented by and a nitrogen-containing compound as a main component is provided, the molecular association of the phthalocyanine compound when being thinned is suppressed, It is possible to prevent the light absorption spectrum from becoming broad and to obtain an appropriate complex refractive index in the vicinity of the laser light wavelength.

The present invention will be described in detail below. Optical recording medium of the present invention, a metal phthalocyanine compound light-absorbing layer is represented by formula (I), a nitrogen-containing compound selected from the replacement or unprotected imidazole compounds, the main component It is characterized by being. That is,
In the optical recording medium of the present invention, the mixture of the metal phthalocyanine compound represented by the general formula as light-absorbing layer (I), the nitrogen-containing compound selected from a good imidazole compounds be substitution is used. The metal phthalocyanine compound is such that the -N = or -N <group in the nitrogen-containing compound is easily coordinated to the central metal M, and the nitrogen-containing compound enters between the molecules of the metal phthalocyanine compound, whereby the metal phthalocyanine compound is introduced. The molecular association of the system compound can be prevented. As described above, in the metal phthalocyanine compound, the absorption peak wavelength (λmax) of the light absorption layer is 710 to 750 nm.
In the range of, be highly desirable to obtain appropriate complex refractive index at the laser wavelength near, but has been found by the present inventors, the phthalocyanine ring α-position (A ^1,
A ² , A ³ , A ⁴ , A ⁵ , A ⁶ , A ⁷ , A ⁸ ) OR group or S
Due to the effect of the R group, λmax of the light absorption layer film is approximately 710.
It falls within the range of ˜750 nm.

[0012] may be replacement for use in the present invention
Nitrogen-containing compounds selected from imidazole compounds,
A compound having -N = or -N <group in the molecule. Specific examples thereof include, but are not limited to, the following compounds. Among these,
Highly effective in preventing association of metal phthalocyanine compounds,
In addition, imidazole compounds are preferable because they are excellent in durability (heat resistance and light resistance). Further, from the viewpoint of maintaining the thermal stability of the light absorption layer, the nitrogen-containing compound preferably has a melting point of 150 ° C. or higher.
When the melting point is less than 150 ° C., the film characteristics (especially optical characteristics) are likely to change in a high temperature environment.

[0013] imidazole, benzimidazole, methyl benzimidazole, dimethyl benzimidazole,
Trimethyl benz imidazole, Application Benefits phenylimidazo <br/> Lumpur like.

The metal phthalocyanine compound used in the present invention has a structure represented by the above general formula (I), and as the central metal M, Mn, Fe, Co, Zn and Cd can be used. . In the phthalocyanine-based compound having these central metals, the -N = or -N <group in the nitrogen-containing compound is easily coordinated with the central metal, and the effect of preventing association is high. On the other hand, the phthalocyanine-based compound is O which may be substituted at the α-position of the phthalocyanine ring.
Has an R group or an SR group, where R is substituted
It may be an aromatic or alicyclic hydrocarbon group which may have 1 to 20 carbon atoms. OR group substituted here
Is an alkyl group or an alkoxy group as a substituent of the SR group.
I can give you something.

A mixing ratio of the nitrogen-containing compound having a group (-N = or -N <group) capable of coordinating to the metal phthalocyanine compound and the metal phthalocyanine compound is 1 / molar ratio. The range of 2 to 2/1 (ratio of nitrogen-containing compound / metal phthalocyanine compound) is preferable. If the molar ratio is less than 1/2, the effect of the nitrogen-containing compound cannot be sufficiently obtained, and conversely if the molar ratio exceeds 2/1, the dye concentration in the film becomes low, and in any case, the extinction coefficient of the film becomes small.

As the material for the light absorbing layer, not only the phthalocyanine compound but also any dye conventionally known as a recording material of an information recording medium is used in addition to the phthalocyanine compound. You can As such a dye, for example, a cyanine dye,
Pyrylium / thiopyrylium dyes, azurenium dyes, squarylium dyes, metal complex salt dyes such as Ni and Cr, naphthoquinone / anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallyl Examples thereof include methane-based dyes, aminium-based / diimmonium-based dyes, and nitroso compounds. Furthermore, if necessary, another third component,
For example, a binder, a stabilizer and the like can be contained. The thickness of the light absorption layer is preferably 100 to 5000 Å, and particularly preferably 500 to 3000 Å. If the thickness of the light absorption layer is less than this range, the recording sensitivity will decrease,
Also, as the thickness increases, the reflectance decreases.

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information recording media. Examples of substrate materials include
Examples thereof include acrylic resins such as polymethylmethacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer, epoxy resins, polycarbonate resins, amorphous polyolefins, polyesters, glasses such as soda lime glass, and ceramics. In particular, from the viewpoint of dimensional stability, transparency and flatness, polymethyl methacrylate, polycarbonate resin, epoxy resin, amorphous polyolefin, polyester, glass and the like can be mentioned.

On the surface of the substrate on which the light absorption layer is provided,
An undercoat layer may be provided for the purpose of improving flatness, improving adhesive strength, and preventing alteration of the light absorption layer. Examples of the material for the undercoat layer include polymethylmethacrylate, 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, polyester, polyimide, vinyl acetate /
Vinyl chloride copolymer, ethylene / vinyl acetate copolymer,
Polymer substances such as polyethylene, polypropylene and polycarbonate: Organic substances such as silane coupling agents: and inorganic substances such as inorganic oxides (SiO ₂ , Al ₂ O ₃ etc.) and inorganic fluorides (MgF ₂ ). it can. The layer thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably 0.01 to 10 μm.

Further, a pregroup layer may be provided on the substrate (or undercoat layer) for the purpose of forming a groove for tracking or an unevenness representing information such as an address signal. As the material for the pregroup layer, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester, and tetraester and a photopolymerization initiator can be used.

Further, a reflective layer may be provided on the light absorption layer for the purpose of improving the S / N ratio, the reflectance and the sensitivity during recording. The light-reflecting substance that is the material of the reflecting layer is a substance having a high reflectance for laser light, and examples thereof include Mg, Se, Y, Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, W, Mn, Re, Fe, C
o, Ni, Ru, Rh, Pd, Ir, Pt, Cu, A
g, Au, Zn, Cd, Al, Ca, In, Si, G
Metals and semimetals such as e, Te, Pb, Po, Sn and Si can be mentioned. Among these, preferable ones are Au, Al and Ag. These substances may be used alone or in combination of two or more or as an alloy. The layer thickness of the reflective layer is generally 100 to
It is in the range of 3000Å. Further, the reflective layer may be provided between the substrate and the light absorbing layer, and in this case, recording / reproducing of information is performed from the light absorbing layer side (the side opposite to the substrate).

Further, on the light absorption layer (or reflection layer),
A protective layer may be provided for the purpose of physically and chemically protecting the light absorbing layer and the like. This protective layer may be provided on the side of the substrate where the light absorption layer is not provided for the purpose of enhancing scratch resistance and moisture resistance. Examples of materials used for the protective layer include inorganic substances such as SiO, SiO ₂ , MgF ₂ and SnO ₂ , thermoplastic resins, thermosetting resins, and UV curable resins. The thickness of the protective layer is generally 5
It is in the range of 00Å to 50 μm.

Next, a method of manufacturing the optical recording medium of the present invention will be described. The method for producing an optical recording medium of the present invention comprises a metal phthalocyanine compound represented by the above general formula (I) directly or via another layer on a substrate having information pits and / or guide grooves formed on the surface thereof. And a light absorption layer containing the nitrogen-containing compound as a main component is provided by coating and film forming means,
It is characterized in that a light reflecting layer is provided thereon by a vacuum film-forming means directly or via another layer, and a protective layer is further provided thereon. That is, the manufacturing method of the present invention comprises the following steps. (A) A metal phthalocyanine compound represented by the general formula (I) and the nitrogen-containing compound are mainly formed on a substrate having information pits and / or guide grooves formed on the surface, directly or through another layer. A step of providing a light absorbing layer as a component by a coating film forming means, (b) a step of providing a light reflecting layer on the light absorbing layer directly or through another layer by a vacuum film forming means, and (c) a light absorbing layer The process of providing a protective layer on top.

(Light Absorbing Layer Forming Step) In the method of the present invention, first, information pits and / or
Alternatively, a light absorption layer containing the metal phthalocyanine compound and the nitrogen-containing compound as main components is provided by a coating film forming means directly or through another layer on the substrate in which the guide groove is formed. That is, a light absorbing layer is formed by coating a substrate with a mixture of the metal phthalocyanine compound and the nitrogen-containing compound as a liquid coating solution. The liquid coating solution is obtained by dissolving the two compounds in a solvent. As a solvent for preparing this coating solution, a known organic solvent (for example, alcohol, cellosolve, carbon halide, ketone, ether, etc.) can be used. Further, examples of the means for forming the light absorbing layer include vapor deposition method, LB method, spin coating method and the like. Since the layer thickness can be controlled by adjusting the concentration, viscosity and solvent drying temperature of the light absorbing layer, Spin coating is preferred.

An undercoat layer is provided on the surface of the substrate on the side where the light absorbing layer is provided for the purpose of improving the flatness of the substrate surface, improving the adhesive strength, and preventing the deterioration of the light absorbing layer. . The undercoat layer in this case is prepared by, for example, dissolving or dispersing the above-mentioned undercoat layer substance in a suitable solvent to prepare a coating solution, and then spin-coating, dip-coating the coating solution.
It can be formed by coating the substrate surface by a coating method such as extrusion coating.

(Light-Reflecting Layer Forming Step) In the method of the present invention, a light-reflecting layer is then provided on the light-absorbing layer directly or via another layer by a vacuum film forming means. That is, the above-mentioned light-reflecting substance, for example, by vapor deposition, sputtering or ion plating,
A light reflecting layer is formed on the light absorbing layer.

(Protective Layer Forming Step) In the method of the present invention, a protective layer is provided on the light reflecting layer. That is, it is formed by vacuum film formation or application 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, which is formed by spin coating the resin and then irradiating it with ultraviolet rays to cure it.

[0027]

The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 Tetraalkylthiometal phthalocyanine represented by (A) in Table 1 below and 5,6-dimethylbenzimidazole were dissolved in chloroform at a molar ratio of 1: 1 to prepare a coating solution having a diameter of 120 mm and a thickness of 120 mm. A light absorbing layer was provided by spin coating on a 1.2 mm thick glass substrate.
The light absorption spectrum of this light absorption layer is shown in FIG. Figure 1
As is clear from the above, the light absorption spectrum of this light absorption layer had a sharp shape with a high right peak (long wavelength side) of the absorption band.

Comparative Example 1 A tetraalkylthiometal phthalocyanine represented by (A) in Table 1 below was dissolved in chloroform to prepare a coating solution.
A light absorbing layer was provided by spin coating on a glass substrate having a diameter of 120 mm and a thickness of 1.2 mm. The light absorption spectrum of this light absorption layer is shown in FIG. As is apparent from FIG. 1, in the light absorption spectrum of this light absorption layer, the shape of the absorption band was broader than that of the light absorption spectrum of Example 1.

Example 2 An absorbing layer was provided in the same manner as in Example 1 except that the tetraalkylthio metal phthalocyanine in Example 1 was replaced with the tetraalkoxy metal phthalocyanine represented by (B) in Table 1 below. The light absorption spectrum of this light absorption layer is shown in FIG. As is clear from FIG. 2, the light absorption spectrum of this light absorption layer had a sharp shape with a high right peak (long wavelength side) of the absorption band.

Comparative Example 2 A light absorbing layer was provided in the same manner as in Comparative Example 1 except that the tetraalkylthio metal phthalocyanine in Comparative Example 1 was replaced with the tetraalkoxy metal phthalocyanine represented by (B) in Table 1 below. . The light absorption spectrum of this light absorption layer is shown in FIG. As is apparent from FIG. 2, in the light absorption spectrum of this light absorption layer, the shape of the absorption band was broader than that of the light absorption spectrum of Example 2.

Examples 3 to 6 Using the dyes represented by (A) to (D) in Table 1 below,
A light absorption layer was formed in the same manner as in Example 1, and λmax was obtained. Λmax of these light absorption layers is 710 to 750 μm
Was in the range (see Table 1).

Comparative Examples 3 to 5 Using the dyes represented by (F) to (H) in Table 1 below,
A light absorption layer was formed in the same manner as in Example 1, and λmax was obtained. Λmax of these light absorption layers is 710 to 750 μm
Was not within the range (see Table 1).

Examples 7 to 9 In the same manner as in Example 1, a light absorbing layer was provided using the dyes represented by (A), (B) and (D) in Table 1 below. For these light absorption layers, the refractive index in the vicinity of the wavelength of the semiconductor laser light was estimated from the reflectance of the film (see FIG. 3).

Comparative Examples 6 to 8 A light absorbing layer was provided in the same manner as in Comparative Example 1 using the dyes represented by (A), (E) and (H) in Table 1 below. For these light absorption layers, the refractive index in the vicinity of the wavelength of the semiconductor laser light was estimated from the reflectance of the film (see FIG. 4). 3 and 4
From the above, it can be seen that the light absorption layer of the present invention has a higher refractive index in the vicinity of the wavelength of the semiconductor laser light than the conventional light absorption layer.

Example 10 A substrate having a guide groove concavo-convex pattern having a depth of about 1200 Å on the surface of a polycarbonate substrate having a diameter of 120 mm and a thickness of 1.2 mm was prepared, and a dye represented by (A) in Table 1 below was prepared. A light absorbing layer was provided on the surface of the substrate by dissolving 5,6-dimethylbenzimidazole in a solvent having ethylcellosolve as a main component in a molar ratio of 1: 1 and spin-coating the solution. The thickness of the light absorption layer is about 1500Å
Met. Au is formed on the light absorption layer by Au sputtering to a thickness of about 800Å to form a reflection layer, and a protective layer made of an ultraviolet curable resin is further formed on the light absorption layer to a thickness of about 5 μm.
An optical recording medium of the present invention was produced. The wavelength of 785 nm, N.V. A. When the EFM signal was recorded and reproduced under the conditions of 0.5 and a linear velocity of 1.4 m / s, I
Top is 65%, Cl error is 220 or less, CD
The value satisfied the standard.

Example 11 An optical recording medium was prepared and evaluated in the same manner as in Example 12 except that the compound represented by (B) in Table 1 below was used as the dye.
Was 72% and the Cl error was 220 or less, which were values satisfying the CD standard.

Comparative Example 9 An optical recording medium was prepared and evaluated in the same manner as in Example 10 except that 5,6-dimethylbenzimidazole was not added, and itop was found to be 38.
%, The Cl error was 220 or more, and the CD standard could not be satisfied.

Comparative Example 10 An optical recording medium was prepared and evaluated in the same manner as in Example 10 except that the compound represented by (E) in Table 1 below was used as the dye.
Was 40% and the Cl error was 220 or more, which did not satisfy the CD standard.

[0040]

[Table 1]

[0041]

According to the optical recording medium of claim 1, the optical recording layer is composed mainly of the metal phthalocyanine compound represented by the general formula (I) and the nitrogen-containing compound. It has excellent optical characteristics that the molecular association of the compound is suppressed and the compound has an appropriate complex refractive index in the laser light wavelength range (760 to 800 nm). In addition, it has the effect of being excellent in durability (heat resistance, light resistance).
There is also a fruit.

(Delete)

According to the optical recording medium of the second aspect , the light absorption peak wavelength of the light absorption layer is in the range of 710 to 750 nm, so that an appropriate complex refractive index can be more reliably obtained at the laser light wavelength. The effect is added.

In the method of manufacturing an optical recording medium according to a third aspect of the present invention, the light absorbing layer is formed by the coating film forming means and the light reflecting layer is formed by the vacuum film forming means. The medium can be easily and stably manufactured.

[Brief description of drawings]

FIG. 1 is a light absorption spectrum diagram of a light absorption layer obtained in Example 1 and Comparative Example 1.

FIG. 2 is a light absorption spectrum diagram of a light absorption layer obtained in Example 2 and Comparative Example 2.

FIG. 3 is a graph showing the relationship between the refractive index and the wavelength in the vicinity of the semiconductor laser light wavelength of the light absorbing layers obtained in Examples 7 to 9.

FIG. 4 is a graph showing the relationship between the refractive index and the wavelength in the vicinity of the semiconductor laser light wavelength of the light absorption layers obtained in Comparative Examples 6 to 8.

Front page continuation (72) Inventor Yu Ueda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) Reference JP-A-3-215466 (JP, A) JP-A-4-226388 (JP, A) JP 4-226390 (JP, A) JP 62-39286 (JP, A) JP 59-16785 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) B41M 5/26

Claims (3)

(57) [Claims] 1. An optical recording medium comprising at least a light absorbing layer provided on a substrate, wherein the light absorbing layer has the following general formula (I):
Optical recording medium, wherein in the metal phthalocyanine compound represented, and a nitrogen-containing compound selected from substitution which may be an imidazole compound, as a primary component. [Chemical 1] (In the formula, M and A ^{1 to} A ⁸ each represent the following. M: Mn, Fe, Co, Zn or Cd atom. A ¹ and A ² , A ³ and A ⁴ , A ⁵ and A ⁶ And A ⁷ and A ⁸ : one of them is an —OR or —SR group, and the other is a hydrogen atom.
R: an optionally substituted aromatic or alicyclic hydrocarbon group. ) 2. The optical recording medium according to claim 1, wherein the light absorption layer has a light absorption peak wavelength (λmax) in a range of 710 to 750 nm. To 3. A surface information pits and / or guide grooves are formed on the substrate, a metal phthalocyanine compound represented by the general formula directly or through other layer (I), is substitution A light-absorbing layer containing a nitrogen-containing compound selected from imidazole-based compounds as a main component by coating and forming means, and a light-reflecting layer is vacuum-formed directly or through another layer thereon. provided by the means, further process for producing an optical recording medium according to claim 1 or 2, characterized in that a protective layer thereon.