JPH0754591B2 - Optical recording medium - Google Patents

Description

The present invention relates to the structure of an optical recording medium.

[Conventional technology]

Optical recording media that can be optically recorded / reproduced or erased
R & D has been actively carried out from the past. Particularly in recent years, magneto-optical recording media utilizing the magneto-optical effect are on the verge of practical use as erasable and rewritable optical recording media.
However, since the recording film of the magneto-optical recording medium is a rare earth transition metal film, it has poor weather resistance. Therefore, as a result of intensive research efforts, the present inventors have made a composite of a dielectric film as a protective film (Japanese Patent Application No. 61-74794) and a laminated structure (Japanese Patent Application No. 61-12276).
Through the development of 7), it has become possible to provide a long-term reliable magneto-optical recording medium that can withstand practical use.

[Problems to be solved by the invention]

However, with the above-mentioned conventional technology, although a medium with long-term reliability can be provided, a transparent resin substrate (PC, PMM
A, epoxy resin, etc.) is used, so that it has a serious defect that the humidity and temperature expansion are large and the deviation (jitter) of the signal once written becomes large. Therefore, in the past, when performing an accelerated test, the medium had to be taken out from a thermo-hygrostat and left at room temperature for one day.

Further, since the translucent resin is exposed on the surface of the substrate, there is a drawback that the scratch resistance is poor and the substrate is immediately scratched.

Therefore, the present invention solves such a problem, and an object of the present invention is to provide an optical recording medium in which the jitter amount of a signal does not change even when the operating environment humidity changes, and which is not easily scratched. It is in.

[Means for solving problems]

In an optical recording medium for recording / reproducing or erasing light by irradiating an optical recording layer formed on a translucent resin substrate, a portion of the optical recording medium that comes into contact with the outside world is cured with ultraviolet rays containing fine dielectric particles. It is characterized by being coated with a resin.

[Action]

According to the above configuration of the present invention, the portion of the optical recording medium that comes into contact with the outside world is covered with the ultraviolet curable resin containing the dielectric fine particles to prevent the intrusion of moisture (moisture) into the transparent resin substrate. . Further, the UV curable resin coating the medium has a small coefficient of thermal expansion because it contains a dielectric material (ceramic), and the change in the jitter amount of the signal is eliminated by suppressing the thermal expansion of the translucent resin substrate. It is possible. Further, since the medium surface hardness also increases, the scratch resistance improves.

Hereinafter, the present invention will be described in detail based on examples.

〔Example〕

FIG. 1 is a schematic sectional view of a magneto-optical recording medium of the present invention. Reference numeral 1 is a polycarbonate (PC) substrate with a guide groove, on which a composite dielectric film 1000 Å of aluminum nitride and silicon nitride is formed as a film 2 by a sputtering method (hereinafter, all the film formation is a sputtering method), and 3 An NdDyFeCoTi magneto-optical recording film 400Å was formed, and further a composite dielectric film 1000Å of aluminum nitride and silicon nitride 4 was formed. Then, a composite dielectric film 500Å of aluminum nitride and silicon nitride 6 is formed on the PC substrate without groove 5 and the PC substrate with the guide groove and the PC substrate without groove are coated with UV light of 7 (U / U). V) Adhesion was adhered using a cured resin. Finally, the entire surface of the laminated magneto-optical recording medium in contact with the external environment was set to 8 and a UV curable resin layer containing SiO ₂ particles was applied and covered.
The film is 15 μm thick and contains 50% by volume of SiO ₂ particles.

Using the medium of the present invention thus prepared and the conventional medium without coating, recording / reproduction was performed and the jitter amount of the signal was observed. The recording temperature is 25 ° C and the humidity is 50%. Then, FIG. 2 is a view showing the change of the jitter amount by changing the humidity under the condition that the medium of the present invention and the conventional medium are kept at 25 ° C., and the humidity dependency diagram of the jitter amount. 21 is SiO ₂ according to the invention
Ultraviolet-cured resin-coated medium containing fine particles, 22 is a conventional uncoated medium, and as is clear from this figure, the jitter of the medium of the present invention is constant at 30 nsec regardless of humidity, but the conventional medium changes with humidity. Jitter increases, because the signal shift occurs due to humidity expansion (contraction).

However, the jitter at a humidity of 50% is the same as the medium of the present invention, 30 nsec.
However, this is because the humidity at the time of recording was 50%.

Next, FIG. 3 is a graph in which the amount of jitter is measured by raising the temperature of these two media while keeping the absolute humidity constant, and is a temperature dependency diagram of the amount of jitter. Reference numeral 21 'is the coated medium of the present invention, and 22' is the conventional uncoated medium. As is clear from this figure, the medium of the present invention shows little change in the jitter amount. On the other hand, it can be seen that the conventional medium has a large temperature dependency on the jitter amount. The amount of jitter of the medium of the present invention and that of the conventional medium are the same at 25 ° C.
This is because.

It is understood from FIGS. 2 and 3 that the medium of the present invention is a medium which is extremely stable against changes in temperature and humidity of the external environment.

Next, various media in which the amount of SiO ₂ particles of the UV curable resin containing SiO ₂ particles was changed were prepared (the coating thickness was kept constant at 15 μm), and the change of the jitter amount due to the temperature rise was observed. That is, the jitter amount was measured by reproducing the signal recorded at 25 ° C at 80 ° C.

FIG. 4 is a diagram showing the dependence of the jitter amount on the SiO ₂ fine particle amount. The horizontal axis is the amount of fine particles (Vol%). What is shown in this figure is the case where the amount of fine particles is up to 80% by volume, but this is because the ultraviolet curable resin having a content rate exceeding 80% cannot be applied uniformly.

From this figure, it can be seen that there is no temperature dependence of the jitter amount if the amount of fine particles is 2 Vol% or more. However, even if it is less than 2 Vol%, the effect is large.

The average particle size of all the SiO ₂ fine particles used in this example is 1000Å
Is. The surface hardness of the medium of the present invention is pencil hardness.
It became 2H, and the scratch resistance was improved as compared with B to HB of the conventional uncoated medium.

The dielectric contained in the ultraviolet curable resin used in this example is SiO ₂ , but it is not limited to SiO ₂ and Al ₂ O ₃ , Ca
F ₂ , CeF, KBr, Kcl, LaF ₃ , NdF ₃ , SiO, ThF ₄ , WO ₃ , CsBr, CsI, Mg
Fine particles of O, NaF, ThO ₂ , MgF ₂ , AlN, Si ₃ N ₄ , SiN, ZnS, SiC, TiN, etc., or fine particles of a mixture thereof may be used.

Also, the average particle size is not limited to 1000Å, but 100Å
There is no problem even if the diameter is 1 μm. Further, the structure of the recording medium used in this example is a close-bonding structure, but the present invention is also effective with an air-sanding structure and a single plate.
The present invention is also effective not only for the magneto-optical recording medium but also for the write-once type optical recording medium. Further, the structure of the recording layer side of this example is
It has a three-layer structure in which the magneto-optical recording layer is sandwiched by a dielectric film, but a four-layer structure in which a reflection film other than this is further attached or a three-layer structure in which the third dielectric film is replaced with a reflection film. But it is effective.

〔The invention's effect〕

As described above, according to the present invention, the portion of the optical recording medium that comes into contact with the outside world is coated with the ultraviolet curable resin containing the derivative fine particles, thereby reducing the amount of signal jitter with respect to the change in temperature and humidity of the external environment. Yes, and eventually Bit Error Ra
The change in te can be reduced. Further, since the surface of the substrate becomes hard, scratch resistance is also improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a magneto-optical recording medium of the present invention. FIG. 2 is a humidity dependence diagram of the jitter amount. FIG. 3 is a temperature dependence diagram of the jitter amount. Fig. 4 is a graph of the SiO ₂ fine particle amount dependence of the jitter amount. 1 ... Polycarbonate (PC) substrate with guide groove 2 ... Composite dielectric film of aluminum nitride and silicon nitride
1000Å thickness 3 …… NdDyFeCoTi magneto-optical recording film 400Å thickness 4 …… Composite dielectric film of aluminum nitride and silicon nitride
1000Å thickness 5 …… PC board without groove 6 …… Composite dielectric film of aluminum nitride and silicon nitride
500 Å Thickness 7 …… UV (U / V) curable resin layer 8 …… SiO ₂ fine particle-containing UV curable resin layer 21 …… The SiO ₂ coated medium according to the present invention 22 …… Conventional non-coated medium 21 ′ …… The present invention By SiO ₂ coated medium by 22 '... Conventional uncoated medium.

Claims (1)

[Claims] 1. An optical recording layer formed on a translucent resin substrate,
An optical recording medium for irradiating light for recording / reproducing or erasing, wherein a portion of the optical recording medium that comes into contact with the outside is coated with an ultraviolet curable resin containing dielectric fine particles.