JPH02240846A - Magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium that is capable of high-speed, high-density recording and has improved C.

[Prior art and problems to be solved by the invention] Magneto-optical recording media use perpendicular magnetic recording and magneto-optical effects (Kerr effect, etc.)
It uses laser light to record and reproduce information in the same way as conventional optical recording media, so it has a large recording capacity and can be overwritten. Furthermore, recording and reproduction can be performed without contact between the head and the medium, and it is not affected by dust, so it has excellent stability. For this reason, magneto-optical recording media are currently being actively researched.
It is expected to be used for video/still image files, computer memory, etc., or as a replacement for floppy disks and hard disks, and is expected to be commercialized in the near future.

A transition metal (
Fa, Co) and rare earth metals (Tb, Dy, Gd, l
lo.

Various amorphous magnetic metal films have been proposed in combination with Er, etc.). ``A magnetic alloy film made by combining one or more of iB transfer metals and rare earth metals and fabricated on a substrate by sputtering or vapor deposition is an amorphous perpendicularly magnetized film (perpendicular to the film surface) near the compensation composition. This results in a magnetized film having an axis of easy magnetization in the direction of the magnetic field, and can be applied to magneto-optical recording media.

Overridable magnetic field modulation methods are available as recording methods for increasing the data transfer speed of magneto-optical recording media, and bit edge recording is attracting particular attention for increasing linear density. To increase the linear density with this pit edge recording, C/
Improving N is an important condition. This C/N is largely related to the length and shape of the recording bit (domain). In other words, when recording is performed using the magnetic field modulation method, the recorded bits take the shape of a feather with a trailing tail in the direction of medium movement, as shown in Figure 3, and this trailing causes a decrease in C/N. I was invited.

On the other hand, a proposal to improve recording bits by adopting a reflective film structure as a heat sink layer was presented at the Optical Memory Symposium '88.
Proceedings p. 49-50.

However, this structure requires an additional reflective layer, which poses problems in terms of cost and process.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and provide a magneto-optical recording medium that is capable of high-speed, high-density recording and has improved C.

[Means to solve the problem]

Considering the above problems, bit formation is influenced by heat conduction in the recording layer during beam irradiation. In other words, the way the recorded bit tails will change greatly depending on the cooling rate of the beam irradiation area during bit formation.As a result of extensive research, the inventor of the present invention found that the top layer (in the case of a single-plate structure Add a conductive filler to the overcoat layer (or adhesive layer in the case of a double-sided adhesive structure) to improve thermal conductivity! It has been found that by applying 11!1, the recording bit shape can be improved and the C/N ratio can be improved.

Therefore, according to the present invention, a recording layer made of an amorphous magnetic alloy thin film made of a transition metal and a rare earth metal is provided on a substrate via a first protective layer.

A magneto-optical recording medium comprising a second protective layer provided thereon, and an overcoat layer or an adhesive layer further provided thereon, characterized in that a conductive filler is mixed into the overcoat layer or the adhesive layer. A magneto-optical recording medium is provided.

Next, the present invention will be explained in detail based on the drawings.

1 and 2 are cross-sectional views showing the layer structure of the magneto-optical recording medium according to the present invention. The magneto-optical recording medium shown in FIG. 1 has a structure in which a recording layer 3 whose both sides are covered with a protective layer 2 is provided on a substrate 1, and an overcoat layer 5 is provided on the upper protective layer 2. . The magneto-optical recording medium shown in No. 2 @ is prepared by preparing a set of ellipsoids on which a recording layer 3 whose both sides are covered with a protective layer 2 is provided on a substrate L, and recording them so that the layer 3 is on the inside. Glue them facing each other)t! It has a double-sided structure that is joined via J6.

Next, the constituent materials and necessary characteristics of each of the above layers will be described.

The substrate l is made of glass or polycarbonate resin,
Plastics such as epoxy resin, polyolefin resin, and acrylic resin are used.

Protection) f42 plays the role of preventing water and oxygen from entering from outside the substrate and deteriorating the characteristics of the recording layer 3. In particular, the protection layer 2 on the substrate side has a magneto-optical effect (Kerr rotation angle) due to multiple reflections of light. As the material constituting the protective layer 2, which also plays the role of enhancing 0.), a nitride such as Si3N4 is preferably used in order to increase the reliability of the medium. Of course, other dielectric materials can also be used. The thickness of the protective layer on the substrate side is 0.01-0.5 pm, preferably 0.0 pm.
5-0.1. n, and the thickness of the protective layer above the recording layer is 0.
．． 01-0, S/js, preferably 0.04-0.07
1M, and sputtering, magnetron sputtering, vacuum evaporation, ion blating, etc. are used as a film forming method.

As the recording layer 3, an amorphous magnetic alloy film made of rare earth metals and transition metals and having perpendicular magnetic anisotropy is used. Specifically, Tb-Fe-Co, Gd-Tb-Fe, Tb-
Ternary alloy such as Dy-Fe or Tb-Dy-F
Quaternary alloys such as a-Co and Gd-Tb-Fe-Co are used. The thickness of the recording layer 3 is 0.01-0.5. ,
Preferably it is set to 0.01-0.1°. Sputtering, magnetron sputtering, etc. are used as a film forming method.

Regarding the overcoat layer 5 and the adhesive layer 6, a conductive filler is mixed into the resin binder to improve thermal conductivity. As the resin binder, acrylic resin, epoxy resin, etc. are used, and as the conductive filler, Ag,
Cu, A(1, Ni, graphite, etc.) are used.The thermal conductivity of these layers is 1.0 to 15.OJ/++
-Set in the range of s4. The value of this thermal conductivity is limited by the ratio of the amount of conductive filler to be added and the amount of resin binder, but it is preferable that the thermal conductivity is larger than 1. When it is smaller than OJ/m·s4, trailing of recording bits becomes long and high density cannot be achieved. The thickness of these layers is 0.01 to 10μ, preferably 3 to 7Is,
As a film forming method, a coating method using a spinner, a roll coater, etc. is used. These layers function to prevent heat diffusion in the protective layer 2 above the recording layer and to enhance the heat storage effect in the recording M3.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

(Example 1) Polycarbonate with a diameter of 130 mm and a thickness of 1.3 mm (
pc) plate as a substrate, Si, N4, (Tbs-iDyo-s)@
-ms (Fe, , , Co, -*)s-1s,
Si and N4 were sequentially laminated as a first protective layer, a recording layer, and a second protective layer to a thickness of 0.087 m, 0.07 μm, and 0.05 μm. Furthermore, add 10w of filler A on the second protective layer.
A resin composition mixed with acrylic resin at a ratio of t% was coated with a spinner to a thickness of 44 cm, and then cured to form an overcoat layer to produce a magneto-optical recording medium having the configuration shown in Fig. 1. did.

(Comparative Example) A magneto-optical recording medium was produced in the same manner as in Example 1 except that the conductive filler was not mixed.

Each of the magneto-optical recording media produced as described above has a linear velocity of 22
(2) After recording a signal for 1 second at a recording frequency of 14.0 MHz, the recorded signal was reproduced and the C/N and recording bit length were measured. The measurement results are shown in Table-1.

Table 1 As is clear from Table 1, the magneto-optical recording medium according to the present invention has a short bit length, improved C/N, and is suitable for high density.

(Effect of the invention) According to one aspect of the present invention, as described in detail above.

By mixing a conductive filler to adjust the thermal conductivity of the overcoat layer or adhesive layer, the heat storage effect of the recording layer is improved, the recording bit shape is improved, and high-speed, high-density recording is possible. /N magneto-optical recording medium can be provided.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing an example of the structure of a magneto-optical recording medium according to the present invention, and FIG. 3 is an enlarged view of a bit shape recorded on a conventional magneto-optical recording medium using a magnetic field modulation method. be. 1... Substrate 2... Protective layer 3... Recording layer 5... Overcoat layer 6... Adhesive layer Figure 2 Figure 3 Patent applicant Ricoh Co., Ltd. - Representative patent attorney Toshiaki Ikeura (1 other person)

Claims (1)

[Claims] (1) A recording layer composed of an amorphous magnetic alloy thin film made of transition metals and rare earth metals is provided on the substrate via a first protective layer, a second protective layer is provided on top of the recording layer, and a second protective layer is provided on top of the recording layer. 1. A magneto-optical recording medium provided with an overcoat layer or an adhesive layer, characterized in that a conductive filler is mixed in the overcoat layer or the adhesive layer.