JPH0317843A - Optical disk and production thereof - Google Patents

Abstract

PURPOSE:To obtain excellent environmental resistance and mechanical strength by a simple technique by using a glass film forming method using a sol-gel method for formation of the film to coat the optical disk. CONSTITUTION:The magneto-optical recording medium 3 is formed on a disk substrate 1 and the entire part of the disk is coated with glassy protective films 2, 2' formed by using the sol-gel method. The medium 3 is continuously irradiated with a laser beam 4 and a switching magnetic field is impressed to the medium by a floating magnetic head 5 simultaneously therewith, by which information is recorded. The protective films 2, 2' formed in such a manner are nearly zero in water permeability and are, therefore, excellent in the environmental resistance. Since the films 2, 2' are nearly equal to glass, the mechanical strength is intensified and the high-reliability optical disk is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for achieving high reliability with excellent environmental resistance and mechanical strength using a simple method in optical recording in which recording, reproduction, or erasing is performed using laser light. This paper relates to an optical disc with a unique property and a method for manufacturing the same. [Background Art] With the recent development of an advanced information society, large-capacity, high-density file memories are attracting attention. Optical discs are attracting attention as a solution to this demand, and various types are used depending on the purpose. However, optical recording materials are prone to corrosion, lack mechanical strength, and ensuring reliability has been an issue in putting them into practical use. In particular, in magneto-optical recording, poor quality alloys of rare earth elements and iron elements are mainly used and are extremely susceptible to corrosion. In addition, in optical discs that perform recording using phase transition, the recording medium deforms due to repeated recording/erasing, which causes recording/erasing.
In some cases, the erase repeatability deteriorated. To address these problems, first of all, to address the former problem, a film was provided to protect the recording film, and the structure of the disk was devised. Regarding the latter problem, techniques have been used such as laminating a sufficiently thick base film or protective film to prevent deformation. As prior art related to these methods, Japanese Patent Application Laid-Open No. 63-113835 and Japanese Patent Application Laid-open No. 62-195743 can be mentioned.

Optical discs have an information recording film, and in order to protect the film from the external environment, control the characteristics of recording, erasing, and reproducing on the disc, and further protect the recorded recording bits, there is an information recording film. It has a shape that seals the membrane, or has a base membrane or protective membrane on one side. but,
The thickness of these films is determined within a certain range depending on the physical properties of the materials used, optical effects, internal stress of the film, thermal conductivity, etc. This Ii1■ is not necessarily sufficient to ensure the reliability of optical discs; rather, there is a contradictory relationship between disc characteristics and reliability. In order to solve the above problem, efforts have been made to ensure reliability by spin-coating a resin made of an organic polymer compound onto the surface of the recording medium and cutting it off.

However, with this spin coating, it is difficult to completely cover the edges of the disk, and there are almost no organic compounds that are completely impermeable to moisture. Furthermore, when recording from the recording medium side using a magnetic head, as in the case of magnetic field modulation recording in magneto-optical recording of optical disks, scratches occur on the recording medium side. Measures such as increasing the amount of water are essential.

On the other hand, for materials that undergo volumetric expansion and contraction during recording and erasing, such as recording methods that utilize phase transition, they do not have sufficient protection performance to follow the entire shape of the material. [Problems] The present invention provides a method for manufacturing an optical disc that is highly suitable for mass production, and also provides a highly reliable optical disc that is excellent in both environmental resistance and mechanical strength. In order to meet these requirements, it is desired that a membrane that does not absorb or permeate water, has high hardness, and can be easily formed in micron-order membranes. Moreover, the formed film is
It is important that there is no internal stress and that the coverage is good. [Means for Solving the Problems] The present invention is directed to solving the above-mentioned problems by adding sol/sol/
This method utilizes a glass membrane method using a gel method. [Operation] According to the above-mentioned sol-gel method, a glass film begins to precipitate on the substrate and the recording medium surface at the same time as the disk on which the recording medium is formed is immersed in a solution containing the raw material compound. In this way, some of the glass becomes a superficial blood-like film.

In this case, an example of the membrane shape or reaction mechanism is as follows. The raw material compound is hydrolyzed in a solution containing the raw material compound to produce a heptanomer, which subsequently undergoes a polymerization reaction to form a sol and then a gel. At this stage, when the disk is removed from the water and dried by heating, a glassy film is formed. Naturally, a film is formed on the surface that was touched by the previous solution, so it is best to mask the areas where you do not want a film to come into contact with the solution. Inorganic compounds or organic compounds are used as raw material compounds, specifically metal alkoxides. Then, the formed film consists of metal atoms Ml or Md and M2.
etc. and acid "J4 JJK fO...-M+ O
Ms O-... bond or -Mt-0-
It has the bond M x − 0−..., which forms a three-dimensional bond. here. M1 and M2 are different elements, S i , A Q , Z r , '
One selected from L' i , G e , "!". As a specific application example, a magneto-optical recording medium is formed on a disk substrate, and the entire disk is made of glass by the sol-gel method described above. When covered with a film of
It is possible to prevent scratches from occurring in the direction of the recording medium due to the collision of the magnetic head, and it is possible to increase mechanical strength. Additionally, since the glassy membrane does not allow water or oxygen to pass through, environmental resistance can be dramatically improved. Furthermore, in the case of magnetic field modulation recording, protection is extremely important because measures such as bonding two disks together cannot be taken. On the other hand, for disks other than those used for magnetic field modulation recording, normally 2
Can be used by laminating two veneers together. This applies not only to magneto-optical recording but also to any type of optical disk, and may be of either a close bonding structure or an air sandwich structure. In that case, if the sol-gel method described above is used after bonding the two disks together, and the substrate is a glass substrate, the recording medium can be sufficiently protected by forming this film only on the edges of the disk. ．． This effect is effective not only for magneto-optical recording but also for optical recording media that are susceptible to corrosion, regardless of the AD recording method, type, or assembly method. Furthermore, among optical recording materials, there are materials whose volume expands or contracts when recording or erasing, and one example is a recording/erasing method that utilizes phase transition. For these recording materials, there are methods to reduce volume changes by improving the material itself, but this is often difficult. on the one hand,
The reliability of the disk must be ensured even if the recording material changes in volume. A suitable material and disk structure for this purpose is to provide a glassy material such as quartz with an interference layer such as resin interposed therebetween. However, the film J1 often needs to be on the order of microns, and sputtering and other methods require a large amount of time to form the film, and are not practical due to lack of mass production. In such cases, the sol-gel method of the present invention is effective, and a film thickness of the original thickness can be obtained in a short time. Therefore, the method of the present invention is highly quantitative.
As described above, by forming a protective film for optical discs using the sol-gel method of the present invention, it is possible to greatly improve the mass production of optical discs, and to produce highly reliable optical discs with excellent environmental resistance and mechanical strength. Obtainable.

〔Example〕

Hereinafter, the details of the present invention will be explained using Examples 1 to 3. [Example 1] This example is a case of magneto-optical recording using a magnetic field variation, l#I recording method as an optical disk. Silicon nitride film (85 nm), TbzaFes on polycarbonate substrate
acohoNba magneto-optical IIs (2 5 nm)
, silicon nitride film (50 nm) - and A Q ss
Tix6 gold) AI'M (40 nm) was sequentially laminated by a sputtering method. This disk was placed in a sol-gel solution and then an aqueous boric acid solution was added.

Here, in addition to SiOz, '1 z H A Q p Z
Oxides such as r g V e W H Ge may also be used. The entire disk was immersed in this solution, taken out after 5 minutes, and left in the atmosphere at 80°C for 1 hour.
Dry. The thickness of the formed film was 10 μm.
Recording was performed on the disks prepared in this way using a magnetic head and a magnetic field modulation recording method. Figure 1 shows the surrounding situation at that time. A magneto-optical recording medium 3 is formed on a substrate 1, and the entire disk is covered with glass protective films 2, 2'. Then, the laser beam 4 was continuously irradiated onto the magneto-optical recording medium 3. At the same time, a switching magnetic field was applied by the floating magnetic head 5 to record information. Examining the relationship between the floating magnetic head 5 and the disk, we find that the floating magnetic head 5 and the glass protective film 2 for protecting the recording medium are in contact when the disk starts rotating.
As the rotational speed increases, the head 5 and the disk come into contact with each other through foreign matter such as dust, causing damage to the disk.

To investigate this point, we conducted a dust injection test.
That is, a disk drive was placed in a test chamber, and alumina particles of 0.5 to 4 μm were sent in using air as a carrier, and the particle density at that time was class 500,000. After 25 hours of operation in such an environment, the surface condition of the disk was examined and no changes such as scratches, cracks, or peeling of the protective IIt film were observed. In addition, this disk was heated at 80℃-90%kl-1 humidity #
Leave it in an ambient atmosphere, and check the defect rate after 100011#.
When I ran tll'J, the defect rate was 5 x 10''6 defects/bit, which was not much different from the defect rate before neglect. For comparison, we investigated the similar environmental resistance of a disk without a glassy protective film. The defect rate, which was 5XIO-' cases/bit, increased to 7x10-5 after being left unused for 1000 hours. In addition, in a comparative optical disk provided with a 10 μm thick resin layer with a water absorption rate of approximately 1%, the IXIO-' defect rate doubled. As described above, the glassy protective film formed according to the present invention has no water absorption and no film defects such as pinholes, so it has high mechanical strength against head crashes, etc., and has excellent environmental resistance. was.

Also, after forming the magneto-optical recording medium. An ultraviolet curable resin layer may be provided on the surface of the #ic body, and a vitreous protective film formed by the sol-gel method of the present invention may be further provided on the surface. This not only further increases the protective effect, but also protects the recording medium from water during the formation of the glass film by the sol-gel method.

By the way, the sol-gel solution used to form the glassy protective film may be one in which Kinku alcoholate is dispersed in an alcohol/water mixed solvent. In this case, the solution is N2 or A
Handle in an inert gas atmosphere such as r. [Embodiment 2] The present invention concerns a magneto-optical disk using an optical modulation method. The cross-sectional structure of the fabricated disk is shown in Figure 2. A magneto-optical recording medium M3 having the same structure as in Example 1 was formed on a plastic substrate 1 made of polycarbonate or the like. Further, a protective scrap 6 made of an organic compound (ultraviolet curing resin in this example) was formed to cover the entire magneto-optical recording medium 3. Two disk single plates having the same structure were assembled by applying adhesive 7 to the bonding surfaces of the disks so that the magneto-optical recording medium 3 faced each other. As the adhesive 7, epoxy resin adhesive, hot melt adhesive, etc. were used. In addition, an air sandwich structure may be used instead of glue bonding, and the method of assembly does not particularly affect the effects of this example. The entire disc was then immersed in the same sol-gel solution as in Example 1, and the entire disc was covered with a gel-like substance. Then, take it out from the solution and dry it.
Glassy IIκ2 was formed. The disk thus produced was heated at 80°C and 90% RH.
We investigated the change in defect rate over time by leaving the product in the tank. The results are shown in Figure 3. As a comparison sample, a disk was used in which the entire disk was not covered with a glassy protective film, but only two disks were bonded together.

In the comparison sample as shown in the figure. The defect rate began to increase after 2000 hours, and after 4000 hours it increased from the initial 1.5X10-8 to 9X10-''.
On the other hand, when the entire disk was coated according to this example, no change in the defect rate was observed even when the disk was left in a high temperature, high humidity environment for more than 4000 hours. Although this embodiment deals with magneto-optical recording, this effect can be obtained regardless of the type of disk. [Example 3] This example deals with the case where a material whose volume expands or contracts as recording or erasing is used.
-Te-Se-Co system was used as the recording material. This is the case with so-called phase-change optical discs, which perform recording and erasing using the phase transition between crystalline and amorphous snow. A schematic diagram showing the sectional structure of the disk is shown in FIG. The disk is made of a silicon nitride film (100 nm) and a GeTaSeCo film (60 nm) on a polycarbonate substrate 1.
nm), silicon nitride film (l O O nm'), and A (l aoN i zO alloy PIA (50 nm)
An information recording medium 8 consisting of four layers was sequentially laminated by a sputtering method. After providing an ultraviolet curable resin layer on this surface, this disk was immersed in the same sol-gel solution as in the example above! A sample was formed and, after drying, a glassy protective film 2 was obtained. Then, the disks of this quasi-plate were pasted together with adhesive 7 so that the recording media faced each other.

The disk thus prepared was repeatedly subjected to recording/playback/erasure to examine changes in the number of discs and the ClN ratio (carrier-to-noise ratio), and the results are shown in Figure 5. As a comparative example, a disk formed by the sol-gel method and not having a vitreous Ju% retention was investigated. According to this, a disc with a glassy protective film on its surface can withstand recording/playback/erasure for up to 90 seconds.
No change in career level was observed even after repeating 0 force or more times. On the other hand, the comparative example of a disk without a glassy protective film showed almost no barrage up to 10,000 cycles, but after that it gradually decreased, and after 106 cycles it suddenly decreased. ．． It was reduced by 17dBm after 9 million repetitions. The cause of this decrease is the shape of the recording medium or substrate, but the glassy protection 11 of the present invention
This could be suppressed by forming %.

[Effects of the Invention] According to the present invention, the vitreous protection 11Q has a water permeability of almost zero, so it has excellent S#t resistance. In addition, since this film is almost equivalent to glass, it can increase mechanical strength.
In addition, we were able to obtain a highly reliable optical disc. Additionally, the sol-gel method can increase mass productivity because it can process a large number of disks at once with a simple process of immersing them in a solution and drying them. Furthermore, if all tracks on the disc are soaked in '8I, it will also have the effect of hard coating.

[Brief explanation of the drawing]

Figures 1, 2, and 4 are schematic diagrams showing the fracture + trJ structure of a disc according to an embodiment of the present invention, and Figure 3 shows defects when the manufactured optical disc was left in 80°C and 90% RH. Fig. 5 is a measurement diagram of the rate deterioration over time, and is a d1 constant diagram of the change in characteristics of the playback output when recording/playback/erasing of the manufactured optical disc is repeated. 1... Disk board. 2.
2'... Glassy protective film, 3... Magneto-optical recording medium,
4... Laser light, 5... Flying magnetic head, 6...
・Organic protection film, 7...adhesive layer, 8 early 3 mouth release 17pm r91 (mmr) W/g /E armpit L group number (0)

Claims (1)

[Claims] 1. In an optical disk that records, reproduces, or erases information using a laser beam and is composed of at least a substrate and an information recording medium, a glassy film is coated with a sol or gel to cover the entire or part of the optical disk. 1. A method for manufacturing an optical disc, characterized in that the optical disc is formed by a method. 2. To form a glassy film by the sol-gel method described in claim 1, a glassy substance is precipitated on the disk surface almost at the same time as the optical disk is immersed in a solution containing the raw material compound. A method for manufacturing an optical disc, characterized by: 3. In the formation of a glassy film by the sol-gel method described in claims 1 and 2, the reaction mechanism is hydrolysis in a solution containing at least a raw material compound, and then sol formation by a polymerization reaction. A method for manufacturing an optical disc, characterized in that it uses a chemical reaction including further gelling and drying processes. 4. A method for producing an optical disc, characterized in that the raw material compound according to claims 2 and 3 is an inorganic compound or an organic metal compound, more preferably a metal alkoxide. 5. In the formation of a glassy film by the sol-gel method according to claims 1, 2, and 3, the produced film has three-dimensional bonds of -M_1-O-M_2-. and M_1 and M_2 are different, and at least S
1. A method for manufacturing an optical disc, characterized in that the optical disc is made of an element selected from i, Al, Zr, Ti, Ge, V, and W. 6. An optical disk manufactured by the manufacturing method described in claims 1 to 5, which uses magneto-optical recording, and records are recorded thereon by a magnetic field modulation recording method using a magnetic head. An optical disc and its manufacturing method characterized by: 7. An optical disc characterized by combining two optical discs manufactured by the manufacturing method according to claims 1 to 5 so that the surfaces on which recording media are formed face each other. 8. In an optical disk that performs recording, reproduction, or erasing using a laser beam and is made up of at least a substrate and an information recording medium, after combining two disks so that the surfaces containing the recording medium face each other, at least The end portions of the disk are sealed with a glassy substance produced by the sol-gel method described in claims 1 to 5, and more preferably, the end portions of the disk are sealed with a raw material compound. A method for manufacturing an optical disc, characterized in that the optical disc is formed by immersing it in a solution containing the disc and using the reaction mechanism set forth in claim 3. 9. Optical discs manufactured by the manufacturing methods described in claims 1 to 5 or claim 7
An optical disc according to item 1, characterized in that the optical disc uses magnetism and magneto-optic effects as a recording method. 10. A recording member in which the optical disc manufactured by the manufacturing method according to claims 1 to 5 or the optical disc according to claim 7 causes volumetric expansion or volumetric contraction or both upon recording. An optical disc characterized by being formed using.