JPS6398858A - Protective coating material for magneto-optical disk formed by using resin substrate - Google Patents

Abstract

PURPOSE:To obtain a protective coating material which does not generate warpage in a magneto-optical disk by coating a magnetic recording layer with a mixture composed of a resin having a specific rate of shrinkage by UV curing and low rate of shrinkage and resin having a high rate of shrinkage. CONSTITUTION:An alkali-free glass layer 2 having an antireflecting and moisture proofing effect, the recording layer 3 and a alkali-free glass layer 4 are laminat ed on a substrate 1 consisting of a polycarbonate resin; further, a protective layer 5 is formed thereon. The protective layer 5 is formed by coating the protective coating material prepd. by mixing 60wt% acrylic UV curing adhesive agent having >=5% rate of shrinkage by UV curing and 40wt% acrylic UV curing adhesive agent having >=5% rate of shrinkage by UV curing to 35mum thickness by a spin coating method, etc., and curing the coating by a high- pressure mercury lamp. The magneto-optical disk provided with such protective layer is free from warpage and is less generated with cracks and pinholes in the veneer state as it is and the durability and reliability thereof are im proved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a protective coating for a magneto-optical disk using a resin substrate. More specifically, the present invention relates to a 1V protective agent using an ultraviolet curing resin gold having a specific shrinkage rate as a protective film for a magneto-optical disk using a resin 1S substrate.

(Prior art) Conventionally, magneto-optical disks, which are used for erasable and rewritable high-density memories, are recorded by heating with light irradiation and can be read using magneto-optical effects such as magnetic force/effect and Faraday effect. be.

For recording on magneto-optical disks, especially G
It is an amorphous thin film made of C○, which has a large write efficiency and a readout efficiency for reading out written signals with a good S/N ratio.
It is ideal as a magneto-optical recording medium because the magnetic field rotates degrees when irradiated with light.

However, magneto-optical recording layers made of general materials (such as CdTbFeCo) have the disadvantage of poor corrosion resistance.In other words, when they come in contact with the atmosphere or water vapor, they are exposed to acid (acid), which deteriorates their magnetic properties, and eventually completely destroys them. It is oxidized and becomes transparent.

5j-0, S, 107, to prevent oxidation of the recording film
Si, N, , Ae, O, ノ1jlE jM 'a Shoes Hold, ,i'#)m f E fi% Membrane e -'J
A method has been proposed in which the recording film is coated with a halogenated organic resin, an ultraviolet curable acrylic resin, or a thermosetting epoxy resin, which provides moisture resistance and/or moisture resistance.

(Problem to be solved by the invention) However, the protective layer of inorganic materials such as S10, SiO, etc. must be imitated using vacuum equipment such as evaporation or sputtering, and the Because it takes time, equipment investment and personnel costs are enormous, causing an increase in the cost of recording media.

In addition, in the case of a protective layer made of an organic resin such as a halogenated organic resin, an ultraviolet curable acrylic resin, a thermosetting epoxy resin, or a resin, the recording layer can be coated with a coating method such as spraying, Coke-1 printing, spinner, or dipping. It can be applied uniformly over surfaces such as the like, and can be cured by solvent volatilization, heating, heating of two parts, UV irradiation, etc., so a protective layer is formed in a short time, the installation cost is low, and it is excellent in terms of workability. It is superior to inorganic protective layers in that it can be manufactured at low cost.

However, the magneto-optical recording film layer provided on the resin substrate has some air permeability and the adhesion between the recording film and the substrate is not strong.
The solvent contained in the 81 fat and the resin constituting the resin permeate, causing spots, spots, pinholes, etc. on the recording film layer. When a laser beam is irradiated onto such a disc to record and reproduce it, it appears as a pin/node error.

In addition, when cured by heating, ultraviolet irradiation, etc., the substrate warps (curves) due to curing shrinkage, and the head that irradiates the laser beam during recording and playback may follow, causing kissing, focus errors, tracking errors9, or in extreme cases, no recording at all. Playback becomes impossible. Normally, to correct disk warpage, two identical disks each provided with a protective film layer are glued together with the recording film inside. By doing this, the warpage is corrected, but at the time when the warp (curvature) occurs due to curing and shrinkage, stress strain is generated between the substrate, the recording film, and the protective film, and at this time, there are already many stress strains on the recording film. pinholes are occurring.

Therefore, even if you paste the two sheets together and correct the problem, pinholes will increase and the damage will occur. error is not resolved.

(Means for solving the problem) In order to solve the above-mentioned problem, the inventor of the present invention has made the following as a result of intensive studies.
The protective agent for a magneto-optical disk using a resin substrate of the present invention is a magneto-optical disk in which a magnetic recording layer for recording information is provided on a resin substrate, in which the magnetic recording layer has an ultraviolet curing shrinkage rate of 5% or less. It is coated with a mixture of a resin and a resin having an ultraviolet curing shrinkage rate of over 5%. Magneto-optical disks record and reproduce information by irradiating the magnetic recording layer with light.
It can be erased.

(Preferred mode for carrying out the invention) A magneto-optical disk using the resin substrate of the present invention.

The protective coating is an ultraviolet curable resin consisting of a mixture of a resin with a curing shrinkage of 5% or less and a resin with a curing shrinkage of more than 5%.

The coating method can be uniformly applied onto the magneto-optical recording layer provided on the resin substrate by a coating method such as spraying, applicator, wire bar, roll coater, flow coater, screen printing, spin coater, or dipping method.

The ultraviolet curable resin of the present invention has a curing shrinkage rate of 5% or less and a curing shrinkage rate of more than 5%.
It is preferable to include a compound.

Most commercially available UV curable adhesives can be used as UV curable resins with a curing shrinkage rate of 5% or less.

As an ultraviolet curing resin with a curing shrinkage rate of over 5%, Ichii
Most of the UV-curable protective film coating agents can be applied.

The mixing ratio of the two can be selected as desired depending on the type of resin the resin substrate is made of, such as polymethylmethacrylate, acrylate (PMMA), or polycarbonate (PC), the magneto-optical recording: IQ's thickness, and the thickness of the layer. For example, there is too little side fat t1'c with a curing shrinkage rate of 5% or less (a beak with a curing shrinkage rate of more than 5%;
If there are too many fingers), the disk will warp (curve) with the recording film inward (with the substrate outward).

Conversely, if the amount of resin with a curing shrinkage rate of 5% or less is more than 80 parts by weight (the amount of resin with a curing shrinkage rate of more than 5% is less than 20 parts by weight), the disc is recorded; (with the board inward) warps (curves). Finally, the mixing amount is determined to a ratio that does not cause warping on the disk. Resin with UV curing adhesive of 5% or less and UV curing shrinkage rate of 5%
The preferred proportion of the resin to the resin is 80 to 20 by weight.
: 20-80, more preferably 60-40:
It is 40-60.

The thickness of the protective layer is usually 0.5 to 100 μm, preferably 20 to 50 μm. (r, (If the taste is too little, destruction of the memorandum due to scratches will occur, and if the thickness is too thick, proper hardening will not occur).

Since the disk of the present invention has good warp (curvature), it can be used as a single disk, or it can be used by bonding two disks together with an adhesive, with the recording layer entirely inside.

The optical disc coated with the ultraviolet curable coating material of the present invention, which is made of a mixture of a resin with a low curing shrinkage rate and a resin with a high curing shrinkage rate, is a single plate without warping (curving).
Since focus errors and tracking errors do not occur, and the stress strain between the substrate, recording layer, and protective layer is small, cracks and pinholes are less likely to occur, and therefore bit errors can be reduced. In addition, the low stress strain means that the shape of the substrate recording film and protective film does not change much even during storage, which significantly improves durability and reliability.

(Example) Hereinafter, the present invention will be explained in more detail based on an example and a drawing of Koshirae 1.

Example 1 A donut-shaped substrate 1 with concentric grooves made of polycarbonate resin is coated with an alkali-free glass layer 2 having an anti-reflection and moisture-proofing effect using a magnetronne pasotaring method with a thickness of 500^ and 7 layers 4 of alkali-free glass 500^ thick. ``A'' is laminated, and then an acrylic ultraviolet curing adhesive (lNC-117, manufactured by Nippon Kayaku ■, curing shrinkage rate 3%) is used as the protective layer 5.
The protective coating of the present invention, which is a mixture of 60i (wt%) and 40 wt% of an acrylic ultraviolet curing protective coating agent (EX-1, Dainippon Ink ■, curing shrinkage rate 10%), was made into a 35 μm thick coating using a spin cord method. It was applied onto alkali-free glass, V4, and irradiated for 10 seconds using a high-pressure mercury lamp at 160 W/α and an irradiation distance of 15 α, cooled in air for 1 minute, and irradiated for an additional 10 seconds to harden the protective coating.

This magneto-optical disk had almost no warpage (curvature) and almost no increase in pinholes. Furthermore, under the condition of this discla 60°C1 relative humidity 90%,
Even after leaving it for a while, the warpage and pinhole values remained the same as before the 1-year test. The results are shown in Table 1.

Comparative Example 1 An acrylic UV-curable adhesive (N) was used as a protective coating.
A magneto-optical disk was produced in the same manner as in Example 1, except that only C-117, Nippon Kayaku (2), curing shrinkage rate: 3%) was applied as the protective layer 5 by the spin code method.

This magneto-optical disk has a substrate on the inside (recording film on the outside)
Warping (curving) and pinholes were also increasing. The results are shown in Table 1 along with the durability test.

Comparative example 2 1'l: Nupin coat as protective layer 5 using only acrylic ultraviolet curing protective film coating agent (Tagu-1, Dainippon Ink (manufactured by Shosha, cured sound absorption ratio 10%) as a wave protector) A magneto-optical disk was prepared in the same manner as in Example 1, except that the coating was performed using the same method as above.

This magneto-optical disk was warped (curved) with the recording layer inward (substrate outward), and the number of pinholes increased. The results are shown in Table 1 along with the durability test.

Note 1) Warpage: Displayed in degrees of curvature. If the recording layer warped to the inside (till), the angle is indicated by 10. If the substrate warped inward, it is indicated by the angle indicated by -.

Note 2) Hinho/L/: Only the recording layer is irradiated with a 30W circular fluorescent lamp, and the pinhole size from the opposite side is 20μ ~ 0.5$0

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a magneto-optical disk of the present invention. 1: Resin substrate 2: Anti-reflection and moisture barrier layer 3: Recording layer 4: Anti-reflection and moisture barrier layer 5: Protective layer

Claims (1)

[Claims] In a magneto-optical disk in which a magnetic recording layer for recording information is provided on a resin substrate, the magnetic recording layer is coated with a mixture of a resin having an ultraviolet and linear curing shrinkage rate of 5% or less and a resin having an ultraviolet curing shrinkage rate of more than 5%. A protective coating for a magneto-optical disk using a resin substrate.