JP2730166B2 - Magneto-optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium capable of recording, reproducing, and erasing information using a converging laser.

[Conventional technology]

In recent years, as a recording layer of a rewritable optical recording medium, development of an amorphous perpendicular magnetization film made of a rare-earth / transition element has been advanced.

This amorphous perpendicular magnetization film is very easily oxidized, and is particularly deteriorated by oxidation during high temperature and high humidity. For this reason, when used, a structure in which the amorphous perpendicular magnetization film is sandwiched by a protective film such as SiN is used to prevent the occurrence of deterioration due to oxidation.

As the substrate on which the recording layer is formed by the amorphous perpendicular magnetization film, a PC substrate and a PMMA substrate by injection molding or 2P
A 2P epoxy substrate and a 2P glass substrate (a glass substrate covered with an ultraviolet curable resin layer) formed by a method are used.

The magneto-optical recording medium is obtained by forming a recording layer on these substrates and bonding the two substrates together with an adhesive such as a hot melt agent.

In the case of a magneto-optical recording medium in which a recording layer of an amorphous perpendicular magnetization film is formed on a resin substrate such as a PC substrate, a PMMA substrate, and a 2P epoxy substrate, moisture absorption and moisture transmission occur through the resin substrate. In many cases, corrosion or peeling of the recording layer occurs. Therefore, in a magneto-optical recording medium using this resin substrate, it is necessary to prevent long-term reliability by preventing moisture absorption and the like.

To ensure this long-term reliability, a 2P glass substrate is effective. Conventionally, as shown in FIG. 2, this type of magneto-optical recording medium has a structure in which a glass substrate 21 is covered with an ultraviolet curable resin layer 22, a recording layer 23 is formed thereon, and both surfaces are bonded with a hot melt agent 24. Was taking. That is, the use of the glass substrate 21 that is more excellent in preventing moisture absorption than the PC substrate prevents moisture absorption and the like, and attempts to ensure long-term reliability.

[Problems to be solved by the invention]

 Conventional magneto-optical recording media have the following disadvantages.

In the magneto-optical recording medium 20, since the ultraviolet curable resin layer 22 is provided on the entire upper surface of the glass substrate 21, the ultraviolet curable resin layer 22
Has an outer peripheral surface and an inner peripheral surface exposed to the outside.

The ultraviolet curable resin layer 22 itself has hygroscopicity and moisture permeability. Therefore, moisture outside the magneto-optical recording medium 20 and moisture inside the center hole 25 enter the ultraviolet curable resin layer 22 through the outer peripheral surface and the inner peripheral surface. As a result, the internal recording layer 23 is oxidized.

Actually, when the magneto-optical recording medium 20 of FIG. 2 was left under high temperature and high humidity, peeling and the like occurred on the inner peripheral surface and the outer peripheral surface of the recording layer 23.

As described above, the conventional magneto-optical recording medium cannot sufficiently secure the expected long-term reliability despite the use of the 2P glass substrate.

An object of the present invention is to provide a magneto-optical recording medium capable of sufficiently securing long-term reliability in order to solve the conventional problems.

[Means for solving the problem]

The present invention relates to a magneto-optical recording medium formed by laminating a pair of glass substrates in which an ultraviolet curable resin layer and a recording layer are sequentially laminated on one side with a hot melt agent so that the recording layers face each other. The ultraviolet curable resin layer and the recording layer therebetween are sealed between the glass substrates by the hot melt agent.

[Action]

Since the ultraviolet-curing resin layer having moisture permeability and hygroscopicity and the recording layer which is easily oxidized by moisture absorption are sealed by a hot-melt agent having moisture-proof properties, moisture outside the magneto-optical recording medium is reduced by the hot-melt agent. Intrusion into the inside is blocked. Therefore, the recording layer and the ultraviolet curable resin layer keep a certain dry state. As a result, long-term reliability for the magneto-optical recording medium is ensured.

〔Example〕

 An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a magneto-optical recording medium according to one embodiment of the present invention.

The magneto-optical recording medium 1 has a structure in which two glass substrates 2, 2 each having an ultraviolet-curing resin layer 3 and a recording layer 4 laminated on one surface are bonded together using a hot melt agent 5.

The glass substrate 2 is formed of a glass material having no moisture permeability. The glass substrate 2 is a disk having a center hole 2a.

The ultraviolet-curable resin layer 3 is formed by adhering an ultraviolet-curable resin in a film shape to a portion inside the surface of the glass substrate 2. The attachment of the ultraviolet curable resin layer 3 to the glass substrate 2 was performed as follows. First, an ultraviolet curable resin was dropped on a Ni stamper in a ring shape using a dispenser. Next, the glass substrate 2 was pressed from above the ultraviolet curable resin. Thereby, the ultraviolet curable resin was spread toward the inner edge and the outer edge of the glass substrate 2. Finally, the ultraviolet curable resin was irradiated with ultraviolet rays to cure the ultraviolet curable resin. Thereby, the ultraviolet curable resin adheres to the glass substrate 2, and the ultraviolet curable resin layer 3 is formed. Accordingly, the glass substrate 2 having the ultraviolet-curable resin layer 3 can be obtained by peeling the glass substrate 2 together with the ultraviolet-curable resin layer 3 from the Ni stamper. What should be noted here is the timing of irradiation with ultraviolet rays. As shown in the figure, the width of the ultraviolet curable resin layer 3 is
The width is sufficiently smaller than the width of the glass substrate 2 and is small enough to exhibit its function. Therefore, when the spread of the ultraviolet curing resin reaches the width shown in the figure, the ultraviolet irradiation is performed.

The recording layer 4 is made of SiN (800 Å) / TbFeCo (800 Å) / SiN (80
It is a thin film having the structure of 0Å). The recording layer 4 is formed on the ultraviolet curable resin layer 3 using a magnetron sputtering device.

The hot melt agent 5 is an adhesive having a small moisture permeability and a small hygroscopicity. As the hot melt agent 5, a polyolefin-based hot melt agent is particularly preferable from the viewpoint of moisture resistance. Bonding of the glass substrates 2, 2 using the hot melt agent 5 was performed as follows. First, the hot melt agent 5 is sufficiently applied to the glass substrate 2, the ultraviolet curable resin layer 3 and the recording layer 4 using a hot melt roll coater. Next, the glass substrates 2, 2 were brought into contact with the surfaces on which the hot melt agent 5 was applied facing each other, and pressed by a press from above and below. The application range of the hot melt agent 5 is the full width of the glass substrate 2 as shown in the figure. That is, the hot melt agent 5 divides the ultraviolet curable resin layers 3,3 and the recording layers 4,4 between the glass substrates 2,2 into the glass substrates 2,4.
Painted to seal between the two.

A reliability experiment was performed on the magneto-optical recording medium 1 configured as described above.

The magneto-optical recording medium 1 was left under the conditions of 80 ° C. and 90% RH for about 500 hours, and then observed under a microscope.

No abnormality was found in the recording layer 4. The recording / reproducing characteristics were the same as those before the experiment, showing good characteristics, and the error rate change was slight.

Next, the conventional magneto-optical recording medium 20 shown in FIG. 2 was tested.

Similarly to the magneto-optical recording medium 1 of the embodiment, the magneto-optical recording medium 20 was left under the conditions of 80 ° C. and 90% RH.

About 200 hours after the standing, peeling of the recording layer 23 from the ultraviolet curable resin layer 22 was observed. This delamination increased in size and number over time, causing a significant change in the error rate.

〔The invention's effect〕

As described above, the magneto-optical recording medium of the present invention
Since the ultraviolet curable resin layer between the glass substrates and the recording layer are sealed between the glass substrates by a hot melt agent, the following effects are obtained.

External moisture is blocked by the hot melt agent and does not enter between the glass substrates. Therefore, the recording layer having the property of being easily oxidized absorbs moisture through the ultraviolet curable resin layer and is not oxidized to cause corrosion or peeling. As a result,
Long-term reliability can be ensured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a magneto-optical recording medium according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing a conventional magneto-optical recording medium. DESCRIPTION OF SYMBOLS 1 ... Magneto-optical recording medium 2 ... Glass substrate 3 ... Ultraviolet curable resin layer 4 ... Recording layer 5 ... Hot melt agent

Claims (1)

(57) [Claims] 1. A magneto-optical recording medium formed by laminating a pair of glass substrates on which an ultraviolet-curable resin layer and a recording layer are sequentially laminated on one side with a hot melt agent so that the recording layers face each other. A magneto-optical recording medium, wherein an ultraviolet curable resin layer and a recording layer between substrates are sealed between glass substrates by the hot melt agent.