JPH02218034A - Both-face recording type magneto-optical disk - Google Patents

Abstract

PURPOSE:To prevent the corrosion of metallic reflecting layers and to improve the aging stability by specifying the content of the alkaline metals or alkaline earth metals in an adhesive agent at the time of sticking two sheets of recording media to each other by using the hot melt adhesive agent to form the both-face recording type magneto-optical disk. CONSTITUTION:Polycarbonate, polymethyl methacrylate, glass, etc., are used for two sheets of substrates 3, 4 to be used for the magneto-optical recording medium and protective dielectric layers 8, 9 having a prescribed size are provided on the surfaces facing each other. The recording layers 10, 11 consisting of the rare earth metals and transition metals preferably in terms of C/N are provided thereon and are coated thereon with the protective dielectric layers 12, 13. Further, the metallic reflecting layers 5, 6 consisting of Al, Au, Cu, etc., are provided thereon to constitute the magneto-optical disks 1, 2. The reflecting layer 5, 6 sides are thereafter stuck to each other by the hot melt adhesive agent layer 7 consisting of an ethylene/vinyl acetate copolymer, polyamide, etc. The content of the alkali metal or alkaline earth metal incorporated therein at this time is regulated to <=100ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magneto-optical disk, and more particularly to a double-sided recording type magneto-optical disk in which a single recording medium is bonded to the sleeve.

[Prior art and its problems]

In recent years, magneto-optical recording media have been widely used for large-capacity data files, etc. as magneto-optical disks that can be written and read using laser light.

Magneto-optical recording media are usually used as a single medium, with a recording layer and a protective layer formed on a transparent substrate by film-forming methods such as e-Tuttering, and in other cases, an adhesive layer is applied with the substrate facing outside. It is sometimes used in the form of a double-sided recording type, in which four sheets are pasted together via an intermediary.

The latter double-sided recording type magneto-optical disk has a large recording capacity and is therefore widely used.

9. During recording and reproduction, light is incident from the substrate side, but in order to effectively utilize the incident light to increase C/Ni and obtain a well-symmetrical recording bit shape, a metal reflective layer is placed on the top layer opposite to the substrate. It has been proposed to provide a magneto-optical disk, and it has also been adopted in the above-mentioned double-sided recording type magneto-optical disk. (for example,
It is disclosed in Japanese Unexamined Patent Publication No. 37-7 JOJJJ. )
The metal reflective layer is usually made of a metal thin film having a high reflectance, such as a single substance or an alloy of AI, Au, Cu, Pt, Ta, and Ti, and among them, the cost is particularly low, the reflectance is low, and the reflectance is low. AI because of its relatively good thermal conductivity.

Cu is mainly being considered.

However, this AI-? There is a problem in that cu is relatively easily corroded and its reflectance gradually decreases during use or storage. This problem is particularly likely to occur when a metal reflective layer is provided on the double-sided recording type magneto-optical disk.

In order to completely improve this problem and improve the corrosion resistance of the reflective layer, methods such as alloying and treating the reflective layer with a metal surface have been proposed, but the problem has not yet been solved satisfactorily. In addition, in the case of a bonded double-sided recording type magneto-optical device, an adhesive layer is provided in contact with the reflective layer and the bond is bonded through the adhesive layer. If 10
Corrosion marks were generated on the surface of the reflective layer after about 0 hours, and as a result, the reflectance locally decreased, resulting in problems such as an increase in dropouts.

Furthermore, in order to prevent corrosion of the first reflective layer, a method of using an adhesive with a low content of halogen ions has also been proposed in Japanese Patent Application Laid-Open No.
-ta/? Although proposals have been made in the μΘ publication, etc., they are still insufficient, and there is still a problem in improving the stability over time of double-sided recording type magneto-optical disks.

[Problem that the invention seeks to solve]

The present invention has been made in consideration of the above-mentioned problems of the prior art, and an object thereof is to provide a double-sided recording type magneto-optical disk with excellent stability over time and a nine-layer reflective layer. It is said that

[Means for solving problems]

The object of the present invention is to provide at least a first ts electric layer, a recording layer, a second dielectric layer, and a metal reflective layer on one surface of the substrate, and the top layer has a magneto-optical recording layer that is the metal reflective layer. In a double-sided recording type magneto-optical disk in which a medium containing a medium is bonded to the substrate with the other side facing outward and the metal reflective layer facing inward through a hot melt adhesive layer, the alkali in the hot melt adhesive layer This is achieved by a double-sided recording type magneto-optical disk characterized in that the content of metal or alkaline earth metal is 1100 pp or less.

The double-sided recording type magneto-optical recording medium of the present invention has a layer structure as shown in FIG.
and - are bonded together via an adhesive layer 7, with the substrate 3, μ on the outermost surface, and the reflective layers j and t on the innermost surface. Then, a magneto-optical recording medium/co-Fi substrate 3, a seventh protective layer t1 on top, a recording layer 10. //First protective layer/Co,/
3 Furthermore, reflective layers j and ji are formed by sequentially forming films in this order, and have a structure in which a plurality of nine different types of thin films are laminated.

In the magneto-optical recording medium of the present invention, alkali metals or alkaline earth metals in the hot melt adhesive are removed by washing with pure water produced by ion exchange, distillation, reverse osmosis, etc. The content in the adhesive N7 is preferably 1100I)p or less, preferably 3099m or less.

As a result, even if placed under high temperature and high humidity, the reflective layer J
Pitting due to corrosion occurs on the bottom surface of the reflective layer 31t. Therefore, the reflectance of the reflective layer 31t does not decrease even after long-term use or storage, and there is no increase in dropouts, resulting in excellent stability over time. A double-sided recording type magneto-optical disk is obtained.

On the other hand, when hot-melt adhesive is used untreated as in the past, double-sided recording type magneto-optical recording media obtained by applying hot-melt adhesive and bonding one sheet of the single-plate magneto-optical recording medium are used. V to promote aging of the disc, e.g.
When exposed to high temperature and high humidity with cro oCrt<1%H,!
#I reflective layer j, i! in about 00 hours! Pitting due to corrosion can be seen on the side of i.

This advantage of the double-sided recording type magneto-optical disk of the present invention is that when the hot-melt adhesive containing an alkali metal or alkaline earth metal comes into contact with water vapor in the air, it locally becomes alkaline, promoting corrosion of the metal reflective layer. It is presumed that this was caused by the prevention of this.

As the adhesive for forming the entire adhesive layer of the magneto-optical recording medium of the present invention, a hot melt adhesive is most preferable because it is excellent in terms of mass production, instant curing, safety, and cost.

The hot melt adhesive used in the double-sided recording type magneto-optical disk of the present invention may be an adhesive resin made of a nonvolatile thermoplastic material that is solid at room temperature, such as ethylene-vinyl acetate copolymer (EVA). ),polyamide,
Polyester, etc. More specifically, Diapoint ■ #3S-≠2. #3S-Goo, Konishibo/Do■
Manufactured by #MU-i oi, 3M [J-i oa, Sekisui Kagaku ■ #ri/HirojL, Toa Kai Sei ■ gXW-3o
, j$XW-/J, gP8-i made by ACI Shirt C
Examples include base rubber base polymers such as J, $Ps-ajo-coO, and the like.

Adhesive for double-sided recording type magneto-optical disk of the present invention: 1 m7
Examples of alkali metals or alkaline earth metals to be removed include Na, Li, Ca, and Ba.

1g etc. Among them, gold JA such as Na, Ni, Ca, etc. all 1
0 (7 ppm or less) is most effective in achieving all the objectives of the present invention.

The routes through which alkali metals or alkaline earth metals may be mixed into the hot melt adhesive include the human body during storage, transportation, use, etc. after manufacturing the hot melt adhesive;
Since there is a possibility of intrusion from containers, equipment, etc., countermeasures for each of the above routes are also effective.

The reflective layer in the magneto-optical recording medium of the present invention! The material for and Δ is usually a thin film of metal with high reflectance.
For example, AI, Au, Cu, Pt.

A single element such as Ta or Ti or a base metal of Fi is used, and among them, AI and Cu are preferred because of their low cost and relatively good reflectance and thermal conductivity. Also, the reflective layer! The thickness of the and is usually 100
to 10OOA.

As the material for the recording layer 10 and /l of the double-sided recording type magneto-optical disk of the present invention, thin films of various oxides and metal magnetic substances can be used. For example, MnB1, MnAl
Ge, crystalline materials such as fncuJ3i, GdIG,
BiSmErGaIG, B18mYbCoGe IG,
single crystal materials such as 1GdCo, GdFe, T
bFe, DyFe, GdFeBi, Gd'l"
bFe, GdFeCo, TbFeCo, TbFe
It is a thin film using an amorphous material such as Nf. Among them, sensitivity
In terms of C/N, etc., a rare earth gold layer or a recording layer mainly composed of a transition metal is most preferable, and even as a single layer, a thin film made of a transition metal and a thin film made of a rare earth metal are laminated in a pomelo shape. used in

The recording layer 10 and/or the magneto-optical recording medium of the present invention
/i1 In order to increase the corrosivity, Cr is added to either or both of the transitional ultrathin film and the rare earth metal thin film.

It can also be classified into gold* grades such as Ti, Pt, and AI.

Further, in the double-sided recording type magneto-optical disk of the present invention, the content of the alkali metal or alkaline earth metal in the adhesive layer 7 is 11017 pp, which increases the corrosion resistance of the recording layer 10 and/or the metal. It contributes to the

The thickness of the recording layer 10 and /l is usually /30 to 0.
It is desirable that it is OK.

The recording fWi of the double-sided i-recording type magneto-optical disk of the present invention
Dielectric protective layer above and below 10 and //! , Otsu and Otsu are provided to improve durability and magneto-optical properties.

The limb dielectric material is AIN, SiO, S+O□.

8tNx, 81AION, etc. are used, among which Si
Nx, 5iA1ON is desirable. The thickness of this dielectric protective layer is usually 300 to 300 mm.

Polycarbonate, polymethyl methacrylate, polyolefin, epoxy, glass, etc. can be used for the substrate 3 and the binding material used in the magneto-optical recording medium of the present invention, and among resin substrates, polycarbonate is particularly preferable.

The recording layer 10 is deposited on the substrate 3 of the double-sided recording type magneto-optical disk of the present invention by a film forming method such as sputtering. ///
The dielectric protective layer j, 6, rl or the like is manufactured by forming a thin film. The oxygen content in the target used when forming these thin films is determined from the recording layer 10. /
In order to improve the stability over time of /, it is desirable that K be as low as possible.

In addition, in order to further improve durability, the reflective layer is formed into a film and coated on the next medium by a spin code method.
It is also possible to coat an ultraviolet curable resin to a thickness of 0 μm, and then apply an adhesive layer thereon for bonding. As for this UV-curable resin, the hook is S made by Dainippon Ink 11.
An example is D-/7 years old.

〔Effect of the invention〕

By setting the alkali metal or alkaline earth metal content #' in the adhesive layer of the double-sided recording type magneto-optical disk to 1100 pp or less, corrosion of the metal reflective layer is completely prevented, resulting in double-sided recording with excellent stability over time. Type magneto-optical disk gold can be obtained.

The novel effects of the double-sided recording type magneto-optical disk of the present invention will be clarified by the following examples and comparative examples.

[Example-1] Used on continuous sputtering equipment, /30φ, thickness /
Each thin film was deposited in the following order on a polycarmenate substrate of J mm to obtain a single-plate magneto-optical recording medium.

First, a SiNx thin film y2io is used as the first dielectric protective layer.
A film was formed to a thickness of ooA, and then a recording layer of TbFeCo was formed to a thickness of -ooA on the seventh dielectric protective layer. Furthermore, a first dielectric protective layer is formed on this recording layer to form a B1Nx thin f! A film of X was formed to a thickness of Jook, and a thin film of A1 was formed thereon to a thickness of JOOA as a reflective layer to obtain a single-plate magneto-optical disk.

Synthetic rubber hot melt adhesive manufactured by Toagosei #XW-t
3-@Hot melt applicator (Suntool/DP
-/LT)'t- was melted and threaded into a diameter/mm or less, and then washed by passing it through pure water of ioMΩ or more.

The alkali metal or alkaline earth metal content t in the hot melt adhesive after the above washing is XCPl! : It was found to be ioppm.

Next, the cleaned hot melt adhesive was coated on one of the AI reflective layers of the single-plate magneto-optical disk obtained in the above manner using a roll coater to a thickness of -0 .mu.m. And using a press! kf/an
A double-sided recording type magneto-optical disk was obtained by bonding the single-plate magneto-optical disk with the reflective Nl on the innermost surface and the substrate with the outermost surface at a pressure of 2.

In addition, when the content of alkali metal or alkaline earth metal in this adhesive layer after creating a double-sided recording type magneto-optical disk was measured, it was found that the content of alkali metal or alkaline earth metal was 111
-'l were identical.

[Example 2] A double-sided recording type magneto-optical disk was manufactured under the same conditions as in Example 7, except that the hot melt adhesive was not washed with pure water.

The content of alkali metal or alkaline earth metal in the hot melt) M adhesive was 1100 pp.

[Comparative example]

As a hot melt adhesive, AeI Shirtsen ■ggP
A double-sided recording type magneto-optical disk was prepared under the same conditions as in Example 1 except that s-ij was used.

The content of alkali metal or alkaline earth gold stripes in this hot melt adhesive was 1000 ppm if-J.

Each of the double-sided recording type magneto-optical disks obtained in the above manner was left in a high-humidity constant temperature bath of Coctj Chi RH, and after 300 hours and to.

The state of the metal reflective layer six times after the time and the bit error rate (BER)' were evaluated under the following measurement conditions.

Pit error relay) (BER) measurement conditions: rotation speed i
The reproduced signal obtained by recording the data modulated at tMHz@w-7 at a frequency of s at too pm was compared with the original signal and measured at two different metalwork locations.

The obtained results are shown in the first ffK.

Surface condition of metal reflective layer: 0: No change 61 Partially discolored ×; Discoloration and pinholes occur on the entire surface.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a double-sided recording type magneto-optical disk of the present invention. /, ko ... magneto-optical disk 3, ≠ ... board! , O... Metal reflective layer 7... Adhesive layer tl... Seventh dielectric protective layer 10, //
...Recording layer No./,3 ...Second dielectric protective layer Patent applicant: Fuji Photo Film Co., Ltd.

Claims (1)

[Claims] On one side of the substrate, at least a first dielectric layer, a recording layer,
There is a second dielectric layer and a metal reflective layer, and the uppermost layer is the metal reflective layer. A double-sided recording type magneto-optical disk in which the layers are bonded together with the layers facing inward, characterized in that the content of an alkali metal or alkaline earth metal in the hot-melt adhesive layer is 100 ppm or less. disk.