JPH05109128A - Production of optical disk - Google Patents

Abstract

PURPOSE:To obtain the optical disk which does not generate a seek error even after long-term use. CONSTITUTION:A groove layer 2 formed with grooves for tracking is formed on a glass substrate 1 and an inorg. protective film 3, a recording film 4 and an inorg. protective film 5 are laminated thereon. A release agent is then thinly applied on the end face 1a of the glass substrate 1 and is dried. A coating liquid (resin liquid) is thereafter applied by a spin coating method thereon and the coating film is cured, by which a hard coat film 6 is formed. The coating liquid hardly sticks to the substrate end face 1a if the release agent is previously applied thereon. The hard coat layer is completely removed form the end face 1a by rightly rubbing the end face 1a with a cloth (or by using an adhesive tape) after the formation of the hard coat layer 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk, and more particularly to improving a hard coat film forming process.

[0002]

2. Description of the Related Art In recent years, various optical recording media (optical disks)
1 has been developed, a general structure of a magneto-optical disk is shown in FIG. 1 as an example. In the figure, on the glass substrate 1, a light (ultraviolet) curable resin (Photo Polymer: 2
There is a groove layer 2 formed of a P resin layer), and pits (pre-pits) (not shown) formed of guide grooves for tracking and indentations indicating track numbers, sector numbers, and the like are formed. An inorganic protective film 3, a recording layer 4 made of a magnetic film, and an inorganic protective film 5 are laminated on the groove layer 2. Further, a hard coat film 6 for protecting each laminated layer is provided on the outermost surface so as to cover the end faces of each layer.

The magneto-optical disk having the above structure is conventionally manufactured by the following method. First, 2 between the master and the glass substrate 1 on which guide grooves and pit molds are formed.
The groove layer 2 is formed by sandwiching the P resin and irradiating it with ultraviolet rays.
Is formed, and an inorganic protective layer 3, a recording layer (magnetic film) 4, and an inorganic protective layer 5 are sequentially formed thereon by a method such as sputtering. After that, a coating solution made of a photocurable resin or the like is uniformly applied using a spin coater, and the coating film (hard coat film 6) is cured by irradiating light to obtain the magneto-optical disk of FIG.

[0004]

By the way, in the optical disc manufactured by the above-mentioned conventional method, when used for a long period of time, sometimes seek (movement of the optical head to a predetermined address = recording position) occurs. There was a problem that there were things that could not be done. However, the cause of this malfunction has not been clarified so far, and therefore no measures have been taken. The present invention has been made in view of the above points, and an object thereof is to obtain an optical disc that does not cause a seek error even when used for a long period of time.

[0005]

The inventor of the present application has conducted extensive studies on the cause of the above-mentioned problems, and has found that the direct cause of the inability to seek is that foreign matter is placed on the disk surface. Analysis of what this foreign substance was was found to be a part of the hard coat film. As a result of further research on why part of the hard coat film became a foreign substance, a hard coat film was actually formed on the end surface of the glass substrate (1a in Fig. 1) which should not be coated by design. This is subject to centrifugal force at every recording / reproduction, and the adhesion between the hard coat film and the glass substrate is not good from the beginning. Therefore, it may peel off from the substrate and become a foreign substance during long-term use. There was found.

Therefore, the present inventor has conceived that the above-mentioned problems can be solved by preventing the hard coat film from being formed on the end face of the substrate from the beginning, and as a result of continuing the research, the present invention has been reached. .. That is, in the present invention, the above-mentioned problems are achieved by applying a release agent to the end face of the substrate in advance before applying the protective coating liquid on the recording layer.

[0007]

As the release agent used in the present invention, for example, an organic material such as a silicon-based material, a fluorine-based material, or a paraffin-based material is dissolved in a suitable organic solvent, for example, an aromatic hydrocarbon solvent such as toluene or xylene. There is something. A thin release film can be formed by thinly applying the above-mentioned release agent to the end surface of the substrate using a roll coater or the like and drying.

When the release agent is applied in advance, the coating solution does not adhere to the end face of the substrate even if the coating solution is applied by the spin coating method, or even if it adheres, it can be easily removed. It can be easily removed by wiping the end face with a cloth or by sticking an adhesive tape or the like on the end face and peeling it off.

As the coating liquid applied to form the hard coat film, for example, a resin which is cured by energy rays (electron beam, ultraviolet rays, etc.) or a resin which is cured by heat is used. Specific examples include energy ray curable acrylic resins by radical polymerization and epoxy resins by cationic polymerization. Further, examples of thermosetting resins include those obtained by three-dimensional ring-opening polymerization of epoxy resins and silicone-based ones. As a method for applying the coating liquid, a spin coating method,
Roll coating method, spray method, etc. can be considered,
The spin coating method is preferable in that a layer having a uniform film thickness can be formed.

The form of the recording layer in the present invention is not limited to any particular one, and includes photochromic type, phase change type,
A write-once type (= write-once type), a magneto-optical recording type, or another recording format may be used. Specific examples of the constituent material of the recording layer include the following. Photochromic type: Organic dye Phase change type: Lower oxide thin film of tellurium, amorphous alloy film, etc. Write-once type: Low melting point metal thin film such as Te, Se, Bi, In etc. Magneto-optical recording type: TbFe, TbFeCo, DyFeC
o, TbDyFeCo, GdFe, GdCo, GdFe
Amorphous perpendicular magnetization film of Co, GdTbFe, GdTbFeCo, etc.

In addition, the inorganic protective films provided above and below the recording layer in FIG. 1 play a role of preventing moisture absorption of the recording layer, and are not necessarily required, but for example, SiO ₂ , An inorganic material such as Al ₂ O ₃ , ZnS, AlN, Si ₃ N ₄ is used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG.
A glass disc having a diameter of 300 mm and a thickness of 1.2 mm is used as the glass substrate 1, a 2P resin is sandwiched between the glass substrate 1 and a master, and ultraviolet rays are irradiated from the glass substrate 1 side to form a groove layer having a thickness of 50 μm. Formed 2. The grooves are for tracking, and are formed in a spiral shape with a groove width of 0.5 μm, a groove pitch of 1.6 μm, and a depth of 800 Å.

Next, on the groove layer 2, as an inorganic protective film 3, Si ₃ N _{4 having} a film thickness of 800 Å was formed by a sputtering method.
A film is provided, and the recording layer 4 is formed on the film by the same sputtering method.
As a result, an amorphous RE-TM film (rare earth-transition metal film) having a film thickness of 100 Å was laminated. Further, a Si ₃ N ₄ film having a film thickness of 1000 Å was formed on the recording layer 4 as the inorganic protective film 5.

Subsequently, as a release agent, a silicone type grease compound release agent (made by Torre Silicone, SH70
20) was thinly applied to the end surface of the glass substrate 1 using a roll coater and dried by heating at 100 ° C. for 5 minutes to form a hard release film. At this time, care was taken so that the release agent did not adhere to the surface of the peripheral edge of the glass substrate on which the recording layer 4 was formed.

Then, a photocurable resin (SD-301 manufactured by Dainippon Ink and Chemicals) was applied with a spin coater to an average film thickness of 10 μm, and the coating film was irradiated with ultraviolet rays of 1000 mJ / cm ^2. The hard coat film 6 was formed by curing. When the end surface of the glass substrate 1 was observed after forming the hard coat film 6, almost no adhesion of the hard coat film 6 was observed. Also, the adhered portion could be easily peeled off by simply rubbing with a cloth.

When an optical disk manufactured as described above was subjected to a continuous rotation reproduction test at 40 ° C., 1800 rpm and 1000 hr, no seek error was observed due to foreign matter adhering to the disk surface.

Although the above embodiments have been described by taking a magneto-optical disk as an example, the present invention can be applied to optical disks other than the magneto-optical disk as described above. It goes without saying that the membrane method itself is not limited to that of the above embodiment. Also,
The laminated structure is not limited to that shown in FIG. 1, and the inorganic protective film may be omitted, or an enhanced layer or another layer for enhancing the reproduced signal may be provided.

[0018]

As described above, in the present invention, since the release agent is applied to the substrate end surface of the optical disk in advance and the coating liquid is applied, the hard coat film does not exist on the substrate end surface. No foreign matter is generated. Therefore, according to the present invention, it is possible to solve the problem that the seek operation failure occurs when the optical disc is used for a long time.

[Brief description of drawings]

FIG. 1 is a sectional view showing a general structure of a magneto-optical disk.

[Explanation of symbols]

 1 Glass Substrate 2 Groove Layer 3 Inorganic Protective Film 4 Recording Layer 5 Inorganic Protective Film 6 Hard Coat Film

Claims (1)

[Claims] 1. A method of manufacturing an optical disc, comprising: a step of forming a recording layer on a substrate; and a step of applying a protective coating solution on the recording layer, wherein the substrate end surface is coated with the coating solution before applying the coating solution. A method for manufacturing an optical disk, characterized in that a release agent is applied to the surface of the optical disk in advance.