JP3371551B2 - Optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium. More specifically, the present invention relates to an optical recording medium suitable for high-speed recording in a heat mode. 2. Description of the Related Art An optical disk has a larger recording capacity than a conventional recording medium and can be randomly accessed.
It is widely used as a reproduction-only medium such as audio software, computer software, game software, and electronic publishing. On the other hand, write-once and rewritable recordable optical disks having an organic recording layer and an inorganic recording layer based on various recording principles have been developed, and some of them have been put to practical use. [0003] One of them is a recordable compact disc (CD-WO), which is capable of additional recording and has the same reflectance as a read-only compact disc. It has the feature that it can be played back. This recordable compact disc usually has a light absorbing layer made of an organic dye on a transparent substrate having a guide groove,
A light reflecting layer made of a metal and a protective layer made of an ultraviolet curable resin are sequentially provided, and the recording is performed by a dedicated recorder using a disc of 1.2 to 1.4 m / sec.
Servo is applied to the groove while rotating at a certain constant linear velocity, and the recording pit is formed by the deformation and alteration of the light absorbing layer and the layer adjacent to it by the heat mode using the laser beam narrowed down to about 1 μm. Has been done. [0004] Usually, a recordable compact disc is recorded while rotating at a low linear speed of 1.2 to 1.4 m / sec. In the case of performing recording, it takes 1 hour / sheet or more. For this reason, there is an increasing demand for high-speed recording such as double speed, quadruple speed, and six times speed of recordable compact discs. On the other hand, when high-speed recording is performed on a recordable compact disk, if the recording is performed with the optimum recording laser power while rotating the disk at a high linear velocity, the laser power required for recording increases. There is a problem that the crosstalk of the reproduced signal is greatly increased. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical recording medium suitable for high-speed recording, which solves the above-mentioned conventional problems and does not cause deterioration in characteristics such as an increase in crosstalk even when high linear velocity recording is performed. As described above, when high-speed recording is performed on a recordable compact disc, there has been a problem that crosstalk is likely to increase. Thus, the present inventors have studied the cause of the increase in crosstalk in order to overcome the above-mentioned problems, and as a result, in an optical recording medium that records data in a groove, such as a recordable compact disc, the light is recorded on the groove. Since the formed light absorbing layer is formed in the form of tracing the groove, the contact area between the light absorbing layer and the light reflecting layer is large, and the thermal conductivity of the protective layer is low, It became clear that the heat generated during recording was easily diffused in the horizontal direction. As a result, at the time of high linear velocity recording, heat generated from a recording laser beam irradiation portion mainly due to an increase in the optimum recording laser power accompanying an increase in the recording linear velocity passes through the light reflection layer having a high thermal conductivity. Therefore, it was found that the pigment was decomposed and deteriorated even in a wider area of the area not irradiated with the laser light. this is,
This shows that the thermal interference between the recording pits increases as the recording linear velocity increases. In addition, since the light absorbing layer is preferably made of an organic substance which generates heat by being rapidly deteriorated and decomposed at a certain threshold temperature, the above-mentioned thermal interference between the recording pits occurs. In such a case, the organic matter decomposition / deterioration region in the light absorbing layer becomes larger, and the recording region becomes unclear.
Based on this knowledge, as a result of intensive studies on means for preventing the expansion of recording pits at the time of high linear velocity recording, the thermal conductivity of the protective layer was increased and excessive heat generated during the recording operation was transferred to the protective layer side. By diffusing, the area where the organic matter constituting the light absorbing layer reaches the thermal decomposition / degradation threshold temperature is limited, and sharp and suppressed recording pits are formed. The present inventors have found that the increase in the talk is suppressed and completed the present invention. The gist of the present invention is to provide an optical recording medium in which a light absorbing layer, a light reflecting layer and a protective layer are sequentially laminated on a transparent substrate, wherein the protective layer is a heat conductive layer, and the heat conductive layer is a heat conductive layer.
An optical recording medium characterized by being a resin layer containing conductive particles . Hereinafter, the optical recording medium of the present invention will be described in detail. The optical recording medium used in the present invention is a heat mode recording type in which a light absorbing layer, a light reflecting layer, and a protective layer are sequentially laminated on a transparent substrate. Usually, the transparent substrate is made of a material such as plastic, glass such as polycarbonate, polymethyl methacrylate, amorphous polyolefin or the like, and is disc-shaped with a thickness of 0.5 to 2 mm, concentrically or spirally on the surface. A guide groove is used. For the light absorbing layer, use the one that absorbs the recording laser light and converts it to heat,
Organic dyes include cyanine dyes, squarylium dyes, croconium dyes, azurenium dyes, triarylamine dyes, anthraquinone dyes, dithiol metal complex salt dyes, indoaniline metal complex dyes, phthalocyanine dyes, and naphthalocyanine dyes Azo dyes, metal-containing azo dyes, intermolecular CT dyes, and the like, preferably cyanine dyes, phthalocyanine dyes, metal-containing azo dyes, particularly metal-containing azo dyes, which may be mixed, or / Additives such as a deterioration inhibitor and a binder may be further added. The light reflecting layer is formed of a material having a high reflectivity with respect to the wavelength of the laser beam to be used, such as gold, silver, copper, aluminum or an alloy thereof, with a thickness of 50 to 200 nm. The protective layer may be made of a material having a sufficiently high thermal conductivity as compared with an ultraviolet curable resin which is usually used for the material of the protective layer.Particularly, particles of a metal, an alloy or a ceramic having a high thermal conductivity are used. It is preferable to use the contained resin. The particle components are gold, silver, copper, aluminum, cobalt, chromium, zinc, nickel, magnesium, tin, iron, osmium, tungsten, molybdenum,
Indium, gallium, iridium, tantalum, palladium, platinum, ruthenium, rhodium, thallium, silicon, diamond, graphite, boron nitride, beryllium oxide, magnesium oxide and mixtures and alloys thereof, preferably gold, silver, copper, aluminum , Iridium, magnesium, molybdenum, silicon, tungsten, zinc, brass, bronze, diamond, graphite, especially silver,
Aluminum and brass are preferred, and the resin component is an ultraviolet-curable resin, a thermosetting resin, preferably an ultraviolet-curable resin, particularly an acrylic-based ultraviolet-curable resin. The contained particles have an average particle size of 0.01 to 10 μm.
m, preferably 0.01-5 μm, especially 0.01-3 μm
m, and the content of the protective layer is preferably 20 to
95% by weight, preferably 30 to 95% by weight, especially 40 to 95% by weight
It is preferably 90% by weight, and the thermal conductivity of the protective layer is 1 W / (m · K) or more, preferably 2 W / (m · K).
K) or more, especially 5 W / (m · K) or more. The upper limit is usually 150 W / (m · K) or less. The protective layer may further contain particles for the purpose of preventing rust, coloring, matting, etc., and titanium dioxide, zinc oxide, alumina, silica and the like are preferably used. As a method for forming the protective layer, a spin coating method or a screen printing method is preferably used. The protective layer is applied after being applied to a thickness of about 0.5 to 50 μm, and then cured. Further, a second protective layer may be provided on the heat conductive layer as needed. In this case, it is not necessary to make the second protective layer heat conductive. Further, the optical recording medium of the present invention may be used by recording while cooling the optical recording medium, so that thermal interference between recording pits is suppressed, and an increase in crosstalk during high-speed recording is more effective. Can be suppressed. The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples unless it exceeds the gist thereof. Example 1 As a transparent substrate, a recording groove having a diameter of 120 mm provided with a periodically meandering tracking groove for a recordable compact disc,
A polycarbonate substrate having a thickness of 1.2 mm was used. The light absorbing layer comprises a metal-containing azo dye represented by the following structural formula:
After being dissolved in methyl cellosolve at a concentration of 4% by weight and filtered, a film was formed on the substrate by spin coating. After the dye application, drying was performed in an oven at 80 ° C. for 10 minutes to completely evaporate the solvent in the dye layer. ## STR1 ## Next, as a light reflecting layer on the light absorbing layer,
Gold having an average thickness of 100 nm was formed by DC magnetron sputtering. Further, an ultraviolet curing agent SPC-112 (manufactured by Nippon Kayaku Co., Ltd.) containing 70% by weight of aluminum particles having an average particle diameter of 0.6 μm on the light reflecting layer.
Was applied to a thickness of 4 μm by spin coating, and was cured by irradiating it with an ultraviolet ray using an ultraviolet ray irradiating apparatus to form a protective layer. The thermal conductivity of the protective layer is measured using a thin-film thermal constant measurement device PIP.
-1 (manufactured by Vacuum Riko Co., Ltd.). An EFM signal was recorded on the obtained recordable compact disk using an optical disk evaluation device DDU-1000 (manufactured by Pulstec Industrial Co., Ltd.). At this time, air-cool the disk storage unit of the optical disk evaluation device,
Recording was performed while keeping the recordable compact disc at 5 ° C., at a recording linear velocity of 4.8 m / sec and a recording laser power of 14.5 mW, which is an optimum recording laser power. The obtained recording disk was reproduced by a commercially available CD player, and the crosstalk of the reproduced signal was measured. Table 1 shows the measurement results of the thermal conductivity and the crosstalk of the thermal conductive protective layer.
It was shown to. Example 2 As a material for the protective layer, 8 silver particles having an average particle size of 0.3 μm were used.
SD-17 (manufactured by Dainippon Ink and Chemicals, Inc.) containing 0% by weight was applied in a thickness of 1 μm by a spin coating method, and was cured by irradiating ultraviolet rays with an ultraviolet irradiation device to form a protective layer. Further, a medium for SSD process (manufactured by Dainippon Ink and Chemicals, Inc.) was applied to the second protective layer in a thickness of 10 μm by a screen printing method, and was cured by irradiating ultraviolet rays with an ultraviolet irradiation device. Except for this, a recordable compact disc was produced in the same manner as in Example 1. The obtained disk was evaluated in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 1 A recordable compact disc was manufactured in the same manner as in Example 1 except that SPC-112 was used as a material for the protective layer as it was. The obtained disk was evaluated in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 2 A recordable compact disc was produced in the same manner as in Example 1, except that SD-17 was used as a material for the protective layer as it was. The obtained disk was evaluated in the same manner as in Example 1. The results are shown in Table 1. [Table 1] The following is clear from Table 1. In Comparative Examples 1 and 2 in which high-speed recording was performed at a linear velocity of 4.8 m / sec, a significant increase in crosstalk was observed. On the other hand, in Examples 1 and 2 to which the present invention is applied, even when high-speed recording is performed, an increase in crosstalk is suppressed, and good recording characteristics are obtained. According to the present invention, high-speed recording on an optical recording medium can be performed without deteriorating characteristics such as an increase in crosstalk, which is industrially very useful.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-3123 (JP, A) JP-A-6-60427 (JP, A) JP-A-4-271029 (JP, A) JP-A-6-27 162571 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 7/24

Claims (1)

(57) [Claim 1] In an optical recording medium in which a light absorbing layer, a light reflecting layer and a protective layer are sequentially laminated on a transparent substrate, the protective layer has a thermal conductivity of 1 W / (m・ K) a heat conductive layer of
An optical recording medium, wherein the heat conductive layer is a resin layer containing heat conductive particles .