JP3485769B2 - Optical recording medium - 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, and more particularly to an optical recording medium having a light reflecting layer of silver or an alloy containing silver as a main component.

[0002]

2. Description of the Related Art Conventionally, gold or aluminum alloy has been widely used for a light reflecting layer of an optical disk which is an optical recording medium. Since gold has a high reflectance and is chemically stable, it is mainly used for a write-once optical disc (CD-R or the like) having an organic dye in a recording layer. However, gold is expensive and cheaper materials are needed to reduce manufacturing costs.

On the other hand, an aluminum alloy is inexpensive, has a relatively high reflectance, and is relatively chemically stable, so that it is a read-only optical disk (CD-ROM, DVD-ROM).
Etc.) and rewritable optical discs (CD-RW, DVD-R
AM, MO, etc.). However, the light-reflecting layer of the CD-R, which is a write-once type optical disc, is required to have a sufficiently high reflectance to compensate for the attenuation of the light beam in the organic dye recording layer. Therefore, an aluminum alloy whose reflectance is not as high as that of gold is used. Not used yet.

As a light-reflecting layer material other than gold or aluminum alloy, silver having a reflectance similar to or higher than that of gold is considered (see Japanese Patent Laid-Open No. 57-212638). Moreover, since silver is much cheaper than gold, it satisfies both high reflectance and economic efficiency, and can be applied to the light reflecting layer of the CD-R which is a write-once optical disc.

[0005]

However, silver is inferior to gold in terms of color tone as compared with gold, and it is impossible to substitute silver, especially when the golden color is a part of the design.
Therefore, there is a demand for a method of using a metal having a high reflectance other than gold for the light reflecting layer and obtaining a golden color tone. Conventionally, it is known that copper-based alloys exhibit a color similar to golden color, but copper alloys easily form oxides and chlorides, and have a problem in corrosion resistance. For example, copper alloy at 80 ℃, 80% R
When stored at H for 1000 hours, it no longer exhibits a golden color.

The present invention has been made in view of the above circumstances, and has an appearance that many people can recognize as a golden color,
Moreover, it is an object of the present invention to provide an inexpensive optical recording medium whose color tone can be maintained for a long period of time.

[0007]

Therefore, in the invention according to claim 1, the optical recording medium comprises a substrate which is substantially transparent to the light beam used and silver or silver laminated on the transparent substrate. A light reflection layer made of an alloy as a main component, and light having a wavelength λ (nm) of 400 <λ ≤ 550 laminated on the light reflection layer has a light transmittance T (%) of 0. 002 × (λ−450) ² +15 <T <0.003
5 × (λ−450) ² +45, and the light transmittance T for light satisfying 550 <λ <750
(%) Of 35 <T <80, and a light-scattering layer that is laminated on the color-control layer and has a pear-like surface and that contains an organic material as a main component.

In the optical recording medium of the present invention having such a constitution, the color control layer having the above light transmittance and the light are diffusely reflected on the light reflecting layer made of silver or an alloy containing silver as a main component. Since it has a light-scattering layer whose surface is pear-like,
When viewed from the light reflection layer side, it has a color tone that looks like gold to many people. Further, as in the invention according to claim 2, when the protective layer having an organic material as a main component and substantially transparent to visible light is provided between the light reflecting layer and the color tone control layer, the light reflecting layer It becomes possible to improve the corrosion resistance of.

The optical recording medium of the present invention can be applied to any of a read-only type, a rewritable type and a write-once type optical recording medium. However, as in the invention according to claim 3, the substrate and the light reflecting layer are used. Is most effective when used as a write-once type optical recording medium which is strongly required to have high reflectance and economy.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of a write-once optical disc which is an embodiment of the optical recording medium of the present invention. On the substrate 1, the organic dye recording layer 2, the light reflection layer 3,
The protective layer 4, the color tone control layer 5, and the light scattering layer 6 are sequentially laminated.

The substrate 1 is preferably made of a material transparent to the recording light beam and the reproducing light beam, for example, resin or glass. Particularly, resin is preferable because it is easy to handle and inexpensive. . 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 size of the substrate are not particularly limited, but are usually disk-shaped, the thickness thereof is usually about 0.5 to 3 mm, and the diameter is 4 mm.
It is about 0 to 360 mm. Prepits on which information is recorded or predetermined patterns such as grooves for tracking and addresses are provided on the surface of the substrate as needed.

The dye of the dye thin film forming the organic dye recording layer 2 is not particularly limited as long as it absorbs light, for example, the energy of laser and changes its optical properties.
Specifically, organic dyes such as cyanine dyes, squarylium dyes, croconium dyes, azurenium dyes, triarylamine dyes, anthraquinone dyes, metal-containing azo dyes, dithiol metal complex salt dyes, indoaniline metal Complex dyes, phthalocyanine dyes,
Naphthalocyanine dyes, intermolecular CT complex dyes and the like are preferably used. Further, these dyes can be used alone or in combination. Further, an antioxidant, a binder and the like can be added to the dye thin film.

As a method for forming the organic dye recording layer 2, a method in which an organic dye is dissolved in an organic solvent and spin-coated on the transparent substrate 1 is preferably used, but it has a sublimation property like a phthalocyanine dye. A vapor deposition method can also be used for the dye. Regarding the film thickness of the dye thin film of the organic dye recording layer 2, the wavelength to be used, the optical physical properties of the light reflecting layer 3, and the dye are taken into consideration in consideration of the recording sensitivity to the energy of light used for recording by a laser and the performance coefficient. The thickness is appropriately selected according to the material of the thin film and the like, and is usually in the range of 120 to 150 nm.

The light reflecting layer 3 is formed of silver or an alloy containing silver as a main component. The element that forms a silver alloy when mixed with silver is not particularly limited, and examples thereof include Al, Au, and C.
u, Cr, Ni, Pt, Sn, In, Pd, Ti, Fe
, Ta, W, Zn and the like. The composition ratio of silver in the alloy is not particularly limited, but in order to obtain a high reflectance in the light reflecting layer 3, it is preferably 50 atomic% or more, particularly 80
Atom% or more is more preferable. The thickness of the light reflecting layer 3 is usually set to 10 to 200 nm. If it is thinner than this, a high reflectance cannot be obtained, and if it is thicker than this, no remarkable effect appears.

The method for forming the light reflecting layer 3 is not particularly limited, but it is preferable to use a vapor phase growth method such as a sputtering method or a vacuum deposition method, which can easily form a homogeneous film and can be easily mass-produced. The protective layer 4 is provided as necessary to improve the corrosion resistance of the light reflection layer 3 containing silver or a silver alloy as a main component.

The protective layer 4 is composed of various organic materials, and in particular, it is preferably composed of a radiation-curable compound or its composition cured by radiation such as electron beam or ultraviolet ray. Examples of the organic material include an acrylate resin, a methacrylate resin, and a polyimide resin, which have good adhesion to the metal layer. As commercially available products, DAICURE CLEAR SD-1700, SD, an overcoat agent manufactured by Dainippon Ink and Chemicals, Inc.
-101, SD-318, SD-301, etc. as the light reflection layer 3
An organic thin film that is spin-coated on top and then cured by ultraviolet light is preferably used. The thickness of the protective layer 4 is usually 0.1.
It is about 100 μm, and if it is thinner than this range, the corrosion resistance may be insufficient, and conversely, if it is thicker than this range, the corrosion resistance is not significantly improved. More preferably 1 to 10 μm
The thickness is good. However, when the surface (silver surface) of the light reflection layer 3 is chemically anticorrosion-treated in advance, or when the light reflection layer 3 is
When a highly corrosion-resistant silver alloy is used for the protective layer 4, the protective layer 4 can be omitted.

The method for forming the protective layer 4 is not particularly limited, but spin coating, gravure coating, spray coating, roll coating and the like can be used. The protective layer 4 is preferably colorless and transparent, but may be colored as long as it does not adversely affect the gold color tone. The color tone control layer 5 contains a colorant, and the light transmittance T (%) at a wavelength of light λ (nm) is 0.002 × (λ−450) ² +15 <T <when 400 nm <λ ≦ 550 nm. 0.003
5 * (λ−450) ² +45, and 35 <T <80 when 550 nm <λ <750 nm.

When the light transmittance T is out of the above range, when the color tone control layer 5 is provided on the light reflection layer 3 made of silver or silver alloy, it becomes impossible to obtain a color tone close to a golden color.
More preferable light transmittance T is 0.003 × (λ−450) ² +20 <T <0.004 when 400 nm <λ ≦ 550 nm.
It is preferable that x (λ−450) ² +40, and 50 <T <80 when 550 nm <λ <750 nm.

The light transmittance T at each wavelength is obtained by forming a color tone control layer on the surface of a transparent substrate and measuring the light transmittance of this color tone control layer. At this time, as a transparent substrate, 85 to 95% in the entire wavelength range of 400 to 750 nm
A glass plate or a resin plate showing the light transmittance of is used. Further, the color tone control layer is formed with the same thickness as that used in the optical recording medium of the present invention.

The color tone control layer 5 may be composed of a plurality of layers, or may have nonuniform composition and optical properties in the film thickness direction. At this time, the light transmittance T of the entire color tone control layer 5 composed of a plurality of layers or the color tone control layer which is not uniform in the film thickness direction must satisfy the above condition. The colorant used in the color tone control layer 5 is not particularly limited, but as the main component, an azo pigment showing an yellow color tone, an azo dye, a dioxazine pigment, an anthranone pigment, an anthranone dye, a pyrimidine reactive dye, a pyrocholine pigment. , Nitroso pigments, etc. are mainly used. Quinacridone pigment, quinophthalone pigment, quinophthalone dye, isoindoline pigment,
Perylene pigment, aniline black, carbon black,
Alkali blue or the like is added for color tone control.

The thickness of the color tone control layer 5 depends on the optical characteristics (refractive index or light absorption coefficient) of the substance forming the color tone control layer 5 so that the light transmittance T of the color tone control layer 5 satisfies the above condition. You can set it to. Although the thickness is not particularly limited, it is usually preferably 1 to 50 μm. A layer thinner than this is difficult to form, and a layer thicker than this may cause the optical recording medium not to look golden depending on the viewing direction.

The color tone control layer 5 is formed by a coating method.
Specifically, the color tone control layer is formed by applying the above-mentioned coating material containing the colorant on the surface of the light reflection layer 3 (when the protective layer 4 is omitted) or the surface of the storage layer 4. In order to increase the strength of the color tone control layer, it is preferable that the coating solution contains an ultraviolet curable resin such as an acrylic resin or an epoxy resin, and is cured by ultraviolet rays or the like after coating. The solvent used for preparing the coating material is not particularly limited, but for example, ethyl acetate, MEK, xylene and the like are preferable. If necessary, a photoreactive monomer or the like may be added to the coating solution for adjusting the viscosity.
The coating method is not particularly limited, and a method such as screen printing or spray coating may be appropriately selected according to various conditions such as the shape of the light reflection layer and the thickness of the color tone control layer. The viscosity of the coating liquid may be appropriately determined according to the coating method and the like.

In the present invention, the light-scattering layer 6 having a pear-like surface and having an organic material as a main component is provided on the color tone control layer 5.
To provide. The light-scattering layer 6 has a fine pear-shaped textured structure on the surface opposite to the substrate 1. This uneven structure
The reflected light from the light reflection layer 3 that has passed through the color tone control layer 5 is scattered. This scattering effect makes it possible to make the optical recording medium look golden when viewed from any angle.
In addition, a delicate texture is added to the color due to the scattering effect, and the pseudo golden color is given a high-class feeling. As a result,
Many people come to recognize that the silver or silver alloy used for the light reflection layer 3 is gold, which is excellent in high quality. In the present invention, the use of the light-scattering layer 6 is essentially important. Without this light-scattering layer 6, there is no sense of quality,
Further, it may not look golden depending on the viewing angle of the optical recording medium.

The size of the fine concavo-convex structure on the surface provided in the light scattering layer 6 is not particularly limited, but from the viewpoint of light scattering ability, the shortest distance between two peaks having almost the same height. It is preferable that x is distributed in the range of 0.1 μm to 500 μm. Unevenness in which the distance x is smaller than the above range may partially exist in the light scattering layer 6, but such small unevenness does not contribute to light scattering. Further, the unevenness with the distance x larger than the above range does not contribute to light scattering. In particular, the shortest distance x is preferably distributed in the range of 0.3 μm to 10 μm. Similarly, from the viewpoint of light scattering ability, the depth of the unevenness is preferably distributed in the range of 0.1 μm to 50 μm, and the unevenness exceeding this range does not contribute to light scattering. The depth of the irregularities is more preferably distributed in the range of 0.3 μm to 10 μm.

The thickness of the light scattering layer is usually 0.1 μm to 10 μm.
The thickness is about 0 μm, and it is difficult to form a film thinner than this, and conversely, even if the thickness is thicker, the light scattering ability is not significantly improved. The thickness is more preferably 1 μm to 10 μm. The light-scattering layer 6 is composed of various organic materials, and is preferably composed of a material obtained by curing a radiation-curable compound or its composition with radiation such as electron beams or ultraviolet rays.

The organic substance material forming the light scattering layer 6 is composed of, for example, an ultraviolet curable resin, a photoinitiator and an organic solvent. The ultraviolet curable resin is not particularly limited,
For example, acrylate-based monofunctional monomers such as N-vinylpyrrolidone, acrylamide, dimethylacrylamide, acroylmorpholine, ethyl carbitol acrylate, phenyl carbitol acrylate, and hydroxyethyl acrylate, or polyester acrylate, epoxy acrylate, urethane acrylate,
Examples include polyfunctional monomers such as hexamethylene bisacrylamide. As commercially available products, for example, DA250, DA314, DA321 manufactured by Nagase Kasei Co., Ltd. can be used. The photoinitiator is not particularly limited, but for example, Irgacure 651, 907 manufactured by Ciba Geigy,
184, or DICURE 1173 manufactured by Merck & Co., Inc. can be used. The organic solvent is not particularly limited as long as it dissolves the ultraviolet curable resin and the photoinitiator and has good volatility, and for example, isopropyl alcohol, ethyl cellosolve, etc. can be used.

Fine particles of various inorganic substances are added to the light-scattering layer 6 for the purpose of making the surface of the light-scattering layer 6. The inorganic material forming the fine particles is not particularly limited, and examples thereof include synthetic silica, talc, titanium oxide, calcium carbonate, calcium silicate, barium sulfate, mica, aluminum hydroxide, alumina and the like. The particle size is
It is preferably about 0.3 μm to 10 μm.

The method for forming the light-scattering layer 6 is not particularly limited, but for example, a coating solution in which the above-mentioned ultraviolet curable resin, photoinitiator, inorganic fine particles, and organic solvent are uniformly dissolved or dispersed is screen-printed or spray-coated. It is preferable that the color tone control layer 5 is coated with the above method and the coating solution is cured by irradiation with ultraviolet rays. The substance forming the light scattering layer 6 is preferably colorless and transparent, but may be colored as long as it does not adversely affect the gold color tone.

[Examples] In order to specifically show the effects of the present invention, examples and comparative examples will be shown and described in more detail. Example 1 A transparent polycarbonate substrate having a spiral guide groove (diameter 12 cm, plate thickness 1.2 mm, track pitch 1.6 μm) was used, and a cyanine organic dye was used as a recording layer and silver was used as a light reflecting layer. A write-once type optical disc having the same was produced.

First, the cyanine dye is dissolved in an organic solvent,
After filtering with a filter to remove the insoluble matter, a spin coater (manufactured by Able) was applied onto the polycarbonate substrate to form an organic dye recording layer. Then, after performing heat treatment in an oven to completely remove the solvent, a 100 nm-thickness silver light reflection layer was formed by a DC magnetron sputtering apparatus. DICURE CLEAR SD, a UV curable resin made by Dainippon Ink and Co., Ltd. on the light reflecting layer.
-1700 was applied by spin coating and then cured by ultraviolet irradiation to form a protective layer. The film thickness of the protective layer after curing was 5 μm.

On the protective layer, a color tone control layer having a light transmittance as shown in FIG. 2 was formed by silk screen printing. This light transmittance is measured by forming a color tone control layer on a glass substrate having a light transmittance as shown in FIG. 3 under the same conditions as when manufacturing an optical disc. As shown in FIG. 2, the wavelength λ of the light transmittance T (%) of this color tone control layer is
(Nm) dependence is 0.002 × (λ−450) ² +15 <T <0.003 when 400 nm <λ ≦ 550 nm
5 × (λ−450) ² +45 is satisfied, and 35 <T <80 is satisfied when 550 nm <λ <750 nm.

On the color tone control layer, DA321 (manufactured by Nagase Kasei Co., Ltd.) 70 wt% and acroylmorpholine 26 wt%
%, And 4 wt% of the photoinitiator Irgacure 651 were mixed with UV-curable resin, ethyl cellosolve, and SiO ₂ fine particles having a particle size of 5 μm at a weight ratio of 5: 5: 1, respectively, to obtain a screen printing liquid After coating by the method, it was cured by irradiation with ultraviolet rays to form a light scattering layer.

(Example 2) Ag97Au3 was used for the light reflection layer.
An optical disk was produced in the same manner as in Example 1 except that the silver alloy having the composition (composition is shown in atomic%) was used. (Example 3) An optical disk was produced in the same manner as in Example 1 except that the color tone control layer had a light transmittance as shown in FIG.

(Example 4) As a substrate, a polycarbonate substrate in which pits (unevenness) for data for 74 minutes was previously formed was used, and reproduction was performed in the same manner as in Example 1 except that the organic dye recording layer was not provided. Dedicated optical disc (CD
-ROM) was prepared. (Comparative Example 1) An optical disk was produced in the same manner as in Example 1 except that the light scattering layer was not provided.

(Comparative Example 2) As shown in FIG. 5, an optical disk was produced in the same manner as in Example 1 except that the order of laminating the light scattering layer and the color tone control layer was exchanged. (Comparative Example 3) An optical disk was produced in the same manner as in Example 1 except that SiO ₂ particles were removed from the material forming the light scattering layer. At this time, the surface of the organic layer formed on the color tone control layer is not formed with a fine satin-like fine concavo-convex structure, the organic layer does not have a light scattering ability, and does not function as a light scattering layer.

(Comparative Example 4) An optical disk was produced in the same manner as in Example 1 except that the color tone control layer had a light transmittance as shown in FIG. As shown in FIG. 6, the wavelength λ (nm) dependence of the light transmittance T (%) of this color tone control layer is 0.002 × (λ−450) ² +15 <T when 400 nm <λ ≦ 550 nm. <0.003
When 5 × (λ−450) ² +45 550 nm <λ <750 nm, the condition of 35 <T <80 is not satisfied.

Reference Example 1 An optical disk was produced in the same manner as in Example 1 except that gold was used for the light reflection layer and no color tone control layer was provided. Reference Example 2 An optical disk was produced in the same manner as in Comparative Example 1 except that gold was used for the light reflection layer and no color tone control layer was provided.

Reference Example 3 An optical disk was produced in the same manner as Comparative Example 3 except that gold was used for the light reflection layer and no color tone control layer was provided. Reference Example 3 An optical disc was produced in the same manner as in Example 4 except that gold was used for the light reflection layer and no color tone control layer was provided.

Then, Example 1 and Reference Example 1 were simultaneously shown to 50 male and female subjects of various age groups, and it was determined that which one was using gold for the light reflecting layer while keeping the optical disc film structure hidden from the subjects. I asked what you think. As a result, 52% of the subjects designated Example 1 and 48% of the subjects designated Reference Example 1. Similarly, when an experiment was performed using Example 2 and Reference Example 1, 50% of the subjects designated Example 2 and 50% of the subjects designated Reference Example 1. When Example 3 and Reference Example 1 were used, 46% of the subjects designated Example 3 and 54% of the subjects designated Reference Example 1. In addition, Example 4 and Reference Example 4
When 50% of the subjects used Example 4,
Test subject designated Reference Example 4. Thus, the subject
It was difficult to distinguish the silver or silver alloy reflective film in Examples 1 to 4 from the gold reflective film in Reference Examples 1 and 4.

On the other hand, when Comparative Example 1 and Reference Example 2 having a similar appearance to 50 male and female subjects of various age groups were simultaneously shown and the same experiment was conducted, 18% of the subjects obtained Comparative Example 1. , 82% of the subjects designated Reference Example 2. Also,
When an experiment was conducted using Comparative Example 2 and Reference Example 1 having a similar appearance, 2% of the subjects obtained Comparative Example 2 by 98%.
The test subject designated Reference Example 1. When a similar experiment was performed using Comparative Example 3 and Reference Example 3 having a similar appearance, 32% of the subjects designated Comparative Example 3 and 68% of the subjects designated Reference Example 3. Further, when a similar experiment was performed using Comparative Example 4 and Reference Example 1 having a similar appearance,
4% of the subjects are Comparative Example 4 and 76% of the subjects are Reference Example 1
Was specified. Thus, the test subject could easily distinguish between the silver or silver alloy reflective film in Comparative Examples 1 to 4 and the gold reflective film in Reference Examples 1 to 3.

Next, Examples 1 to 4 and Comparative Examples 1 to 4 are simultaneously shown to 50 male and female subjects of various age groups, and a sensory evaluation regarding a golden-colored high-class feeling is performed by a five-level evaluation of 1 to 5. It was Table 1 shows the average values of the sensory evaluation. The higher the number, the better the luxury.

[0042]

[Table 1]

From the results shown in Table 1, it can be seen that Examples 1 to 4 were highly evaluated for high-class feeling.

[0044]

According to the invention of claim 1 described above,
Since the light reflecting layer can exhibit a golden color without using gold, and the color tone control layer and the light scattering layer can be formed by a coating method, a high-quality optical recording medium can be manufactured at low cost. . Further, since the color tone control layer has good corrosion resistance, it is possible to maintain the golden color tone for a long time.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, the presence of the protective layer allows
The corrosion resistance of the light reflecting layer can be further improved. Further, according to the invention of claim 3, there is an effect that a write-once type optical recording medium having a high quality can be provided at a low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the layer structure of a write-once optical disc according to an embodiment of the present invention.

FIG. 2 is a light transmittance characteristic diagram of the color tone control layers of Examples 1 and 2.

FIG. 3 is a light transmittance characteristic diagram of the substrate used in each example.

FIG. 4 is a light transmittance characteristic diagram of the color tone control layer of Example 3.

FIG. 5 is a cross-sectional view showing the layer structure of the write-once optical disc of Comparative Example 2.

FIG. 6 is a light transmittance characteristic diagram of a color tone control layer of Comparative Example 4.

[Explanation of symbols]

1 substrate 2 Organic dye recording layer 3 Light reflection layer 4 protective layer 5 color tone control layer 6 Light scattering layer

Claims (3)

(57) [Claims] 1. A substrate which is substantially transparent to a light beam used, a light reflecting layer which is laminated on the transparent substrate and which is made of silver or an alloy containing silver as a main component, and which is laminated on the light reflecting layer. , Wavelength λ (nm) is 400 <λ
For light satisfying ≦ 550, the light transmittance T (%) is 0.002 × (λ−450) ² +15 <T <0.003.
5 × (λ−450) ² +45, and the light transmittance T for light satisfying 550 <λ <750
(%) Is 35 <T <80, and a light-scattering layer which is laminated on the color-tone controlling layer and has a pear-like textured surface and which contains an organic material as a main component. An optical recording medium characterized by the above. 2. The optical recording according to claim 1, wherein a protective layer containing an organic material as a main component and substantially transparent to visible light is provided between the light reflection layer and the color tone control layer. Medium. 3. The optical recording medium according to claim 1, wherein an organic dye recording layer is provided between the transparent substrate and the light reflecting layer.