JPH0620300A - Optical recording medium - Google Patents

Abstract

PURPOSE:To prevent adhesion of dust onto the surface of a substrate by providing a specified conductive layer on the surface of the substrate and then providing a protective layer of specific thickness thereon. CONSTITUTION:A recording layer 2 is provided on a substrate 1 while a conductive layer 8 is provided on the surface of the substrate 1 on the opposite side to the recording layer 2 and a surface protective layer 7 of 0.05-1.0mum thick is provided thereon. The conductive layer 8 is composed of nonmagnetic metal or metal oxide of gold, silver, copper, palladium, indium oxide, tin oxide, antimony oxide, titanium oxide, SnO2/In2O3, Sb2O5/SiO2, or the like. The surface protective layer 7 employs so-called hard coat agent composed of energy beam (e.q. ultraviolet ray curable or thermosetting resin. Surface protective layer 7 thinner than lower limit exhibits insufficient scratch resistance whereas surface protective layet thicker than upper limit exhibits too high surface resistivity and insufficient effect for preventing adhesion of dust.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical recording medium. More specifically, the present invention relates to an optical recording medium in which dust such as dust and dust is less attached to the surface of a substrate.

[0002]

2. Description of the Related Art In recent years, an optical recording medium has attracted attention as a large-capacity, high-speed memory medium. As the optical recording medium, a read-only type optical disc (CD, CD-ROM, etc.), a recording / playback type optical disc (write-once type), recording, reproducing, erasing,
A rewritable optical disc (rewritable type) and the like are known. Generally, a resin substrate (polycarbonate resin, acrylic resin, etc.) is used as a substrate for these optical recording media. Since the resin substrate itself is a poor conductor of electricity, it is easily charged by friction, and therefore the optical recording medium. During manufacture, storage and use of the recording medium, dust such as dust and dust adhered to the surface of the substrate of the optical recording medium, causing a read error. Further, when this is mounted on a disk drive mechanism, there is a problem that a high voltage discharge occurs and a reading error occurs due to noise, or the drive mechanism is damaged. For this reason, there has been proposed a method of kneading an antistatic agent on a substrate of an optical recording medium, or coating an antistatic agent on the surface of the substrate (JP-A-61-276145).

[0003]

However, the former method described above may cause the recording layer of the optical recording medium to be easily oxidized and deteriorated, and the latter method has a sufficient antistatic property on the substrate surface. However, it is hard to say that the prevention of dust adhesion is sufficient.

[0004]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems of the optical recording medium, and as a result, a specific protective layer on the surface of the substrate opposite to the side on which the recording layer is provided. It has been found that the above problems can be solved by providing the present invention, and the present invention has been solved.

That is, according to the present invention, in an optical recording medium having a recording layer provided on a substrate, a conductive material formed of a non-magnetic metal or metal oxide is formed on the surface of the substrate opposite to the side provided with the recording layer. The present invention resides in an optical recording medium in which a layer is provided and a surface protective layer made of a curable resin is provided on the surface of the layer in a thickness of 0.05 to 1.0 μm. Hereinafter, the present invention will be described in more detail. The present invention provides an optical recording medium in which a recording layer is provided on a substrate, a specific conductive layer is provided on the surface of the substrate opposite to the side on which the recording layer is provided, and a surface protective layer made of a curable resin is further provided on the surface. An overcoat layer) is provided.

From its structure, the optical recording medium is largely classified into an air sandwich structure system as shown in FIG. 1, a whole surface adhesion bonding system as shown in FIG. 2 and a single plate coating system as shown in FIG. Be separated. The present invention can be applied to any of these structures. In the figure, 1 is a substrate, 2 is a recording layer, and 3
Is a spacer, 4 is an air layer, 5 is an adhesive layer, 6 is a protective layer, 7
Indicates a surface protective layer (overcoat layer), and 8 indicates a conductive layer.

In the present invention, as the substrate 1, a resin substrate made of polycarbonate resin, acrylic resin, polystyrene resin, polymethylmethacrylate resin or the like is used.
As the recording layer 2, any layer structure generally used for publicly known optical recording can be used. For example, Al, A
A read-only recording layer made of a metal having a high reflectance such as u, and a write-once recording layer made of a metal having a low melting point such as Te. Further, for example, TbFe, TbFeCo, TbCo,
Amorphous magnetic alloy of rare earth and transition metal such as DyFeCo,
An example of the magneto-optical recording layer is a polycrystalline perpendicular magnetization film such as MnBi or MnCuBi. As the magneto-optical recording layer, a single layer may be used, or two or more recording layers such as GdTbFe / TbFe may be stacked.

Usually, in the case of the write-once type (drilling type), as shown in FIG. 1, in the case of the air sandwich type via a spacer 3 so as to form an air layer 4, the magneto-optical recording type. It is used as a bonding type in which two substrates are bonded together by an adhesive layer 5 as shown in FIG. 2 or as a coating type in which a protective layer 6 is coated on the surface of the recording layer 2 as shown in FIG. The present invention is applicable to any type of medium. The present invention is characterized in that the specific conductive layer 8 is provided on the surface of the substrate 1, and the surface protective layer 7 is provided on the surface with a specific thickness.

As the conductive layer 8, a nonmagnetic metal such as gold, silver, copper, palladium, indium oxide, tin oxide, antimony oxide, titanium oxide, SnO ₂ / In ₂ O ₃ , Sb ₂ O ₅ / SiO ₂ or the like is used. Alternatively, a metal oxide is used. Board 1
As a method of forming the conductive layer on the surface of the non-magnetic metal, a method such as a vacuum deposition method, a reactive deposition method, a sputtering method, a reactive sputtering method, or an ion plating method of the nonmagnetic metal or metal oxide is adopted. It

The layer thickness of the conductive layer 8 is not particularly limited, but the surface specific resistance of the surface of the protective layer after forming the surface protective layer 7 on the surface is 1 × 10 ⁶ Ω / port to 5 × 1.
0 ¹³ Ω / mouth Desirably 5 × 10 ⁸ Ω / mouth to 5 × 10 ¹³ Ω
A layer thickness in the range of / mouth is preferable. As the surface protective layer 7, a so-called hard coat agent made of an energy ray (for example, ultraviolet ray) curable or thermosetting curable resin is used. Energy rays (for example, ultraviolet rays (U
V)) As the curable resin, a resin composed of a single or a plurality of acrylate or methacrylate groups, for example, a resin containing epoxy acrylate or urethane acrylate as a main component is preferably used. In addition, as the thermosetting resin, silicon-based resin, epoxy-based resin, titanium-based resin, or the like is used.

The hardened resin may be provided directly on the surface of the conductive layer 8 of the disk substrate or via another layer, and the method thereof includes spin coater, dipping, spray, roll coater, flow coater method and the like. The coating method or the like can be used. In addition, for the coating film curing conditions after the coating film formation, a curing method suitable for each coating agent may be used. For example, energy curing type, that is, ultraviolet (UV)
A method of irradiating with ultraviolet rays for a curable type, an electron beam for an electron beam curable type, or a heat treatment for a thermosetting type is adopted.

Thickness of the formed surface protective layer 7 (after curing)
Is 0.05 to 1.0 μm, preferably 0.1 to 0.5 μm
If it is less than the lower limit, the scratch resistance is insufficient, and the function as a hard coat layer is insufficient.
If it is thicker than the upper limit, the surface resistivity becomes too high, and the dust adhesion preventing effect becomes insufficient.

[0013]

EXAMPLES Examples will be shown below, but the present invention is not limited to the following examples. Example 1 Diameter 1 having a hole with a diameter of 15 mm in the center as a transparent substrate
A circular flat plate-shaped polycarbonate injection-molded substrate with a guide groove having a thickness of 30 mm and a thickness of 1.2 mm was used, and a recording film having the following layer structure (the film thickness in parentheses represents the film thickness) was formed thereon by a continuous sputtering device. To produce a recording disc. Substrate / SiNx (750Å) / TbFeCo (3
00Å) / AlSi (400Å) / SiNx
(350Å)

On the surface of the transparent substrate of the above-mentioned optical recording medium (the surface on which the magnetic layer is not provided), palladium metal is used in an amount of 3 × 18 ^-8 T using a DC magnetron sputtering device.
Sputtering was performed in Ar gas under reduced pressure of orr to form a conductive layer. The surface resistivity of this conductive layer is 8 × 10.
It was ⁸ Ω / mouth. As an acrylic resin, dipentaerythritol hexaacrylate (Aronix M-400 manufactured by Toagosei Co., Ltd.) 10% by weight, N-vinylpyrrolidone (Aronix M-150 manufactured by Toagosei Co., Ltd.) 3.0% by weight, bifunctional urethane acrylate (Sartomer) A resin component consisting of 2.0% by weight of Chemlin 79504 manufactured by K.K. was used.

2-Methyl-1- [4 as a photopolymerization initiator
5.0% by weight of ((methylthio) phenyl] -2-morpholinopropane-1 (trade name Irgacure-907) as a solvent, 50% by weight of toluene, and 1 of isobutyl alcohol.
0% by weight, 10% by weight of butyl acetate, and 10% by weight of ethylene glycol monoacetate were mixed with the above resin component to obtain an overcoat agent. The obtained overcoating agent was applied using a spin coater and cured by an ultraviolet irradiation device to obtain a protective film having a thickness of 0.5 μm. The obtained optical recording medium was subjected to surface resistivity, dust adhesion test and scratch resistance test, and the results are shown in Table 1.

The evaluation method is as follows. 1) Surface resistivity Device name: SME-8310 Super Insulation Meter Device company name: Toa Denpa Kogyo Co., Ltd. Method: Place the material on the ring electrode and measure it in an atmosphere of 22 ° C / 48% RH. The value 1 minute after was read.

2) Dust adhesion test Device name: MT type dirt chem bar Device company name: Ueki Kosaku limited company Method: Before the test, measure the bite error rate of the disk. The disk together with the drive is placed in a dirt chem bar, and dust (Kanto loam powder 10 to 20 mg) is stirred at a wind speed of 0.7 m / s, taken out after 4 hours, and the bite error rate is measured again. 3) Scratch resistance After cleaning with a commercially available magneto-optical disk cleaner, the disk surface was observed visually and with an optical microscope. Cleaner: Product name MOA-D55 (manufactured by Sony Corporation) Method: A disk incorporated in a cartridge was set in a cleaner, slid (cleaned) for about 3 hours in a dry system, and then observed.

Example 2 A conductive layer was formed in the same manner as in Example 1 and an overcoating agent was applied thereon to form a protective layer having a film thickness of 0.1 μm. The optical recording medium thus obtained was tested in the same manner as in Example 1 and the results are shown in Table 1. Comparative Example 1 On the conductive layer obtained in the same manner as in Example 1, the same overcoating agent as used in Example 1 was used to form a protective layer having a thickness of 2 μm. The obtained optical recording medium was tested in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 A conductive layer was formed in the same manner as in Example 1. No overcoat layer was provided on this medium. The same test as in Example 1 was performed, and the results are shown in Table 1. Comparative Example 3 The optical recording medium obtained in the same manner as in Example 1 was provided with no conductive layer and only an overcoat layer (protective layer) having a thickness of 0.5 μm was formed on a transparent substrate. The same test as in Example 1 was performed and the results are shown in Table 1.

Comparative Example 4 An optical recording medium (having neither a conductive layer nor a protective layer) obtained in the same manner as in Example 1 was tested in the same manner as in Example 1. The results are shown in Table 1.

[0021]

[Table 1]

[0022]

The optical recording medium of the present invention has a special antistatic treatment structure on the surface of the medium, and is free from dust and the like, which is very useful in use.

[Brief description of drawings]

FIG. 1 Sectional view

FIG. 2 is a sectional view.

FIG. 3 is a sectional view.

[Explanation of symbols]

 1 substrate 2 recording layer 7 surface protective layer 8 conductive layer

Claims (1)

[Claims] 1. An optical recording medium having a recording layer provided on a substrate, wherein a conductive layer made of a non-magnetic metal or metal oxide is provided on the substrate surface opposite to the side provided with the recording layer. An optical recording medium having a surface protective layer made of a curable resin on the surface thereof in a thickness of 0.05 to 1.0 μm.