JPH03238636A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain the optical disk having a good signal reproducing characteristic and high reliability by specifying the modulus of elasticity of an adhesive and further adhering the end faces of substrates with a 2nd adhesive. CONSTITUTION:Many pieces of magneto-optical recording media having interference films (inorg. protective films) 2 consisting of SiOx, SiNx, etc., and having, for example, 0.07mum thickness, magneto-optical recording films 3 consisting of TbFeCo and having, for example, 0.08mum thickness, inorg. protective films 4 consisting of SiOx, and org. protective films 5 consisting of an acrylic UV resin on substrates 1 are produced. Two pieces of the media are adhered by the adhesive 6 in such a manner that the org. protective films 5 face each other; further, the outer peripheral and faces of 9 kinds of these optical disks are adhered by the adhesive 7. The modulus of elasticity G' of the adhesive 6 is specified to 1X10<6=G'20 deg.C<=1X10<7>dyne/cm<2> at 20 deg.C, 2X10<5=G'70 deg.C<=2X10<6> dyne/cm<2> at 70 deg.C, and G'20 deg.C/G'70 deg.C<=50. The high reliability is maintained in this way without deteriorating the optical disk even when the disk is placed under severe environment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk used in magneto-optical memories, magnetic recording devices, display elements, etc., and particularly relates to an optical disk suitable as a computer memory.

[Prior Art] Magneto-optical memory, which can store a large amount of information at high density and read out information at high speed, has been attracting attention in recent years. This type of optical memory is an optical disk that has a structure in which two magneto-optical recording media each having an interference layer, a magneto-optical recording layer and a protective layer sequentially formed on a transparent substrate are bonded together with an adhesive, with the protective layers facing each other. is widely used. Optical disks for computer memory are ISO/DIS.
9171, the usage environment is 10°C to 50°C, long-term storage condition -10°C to 50°C, and short-term storage condition -20°C to
The temperature is set at 55°C. However, during actual use, the temperature inside the disk drive device is expected to be around 60° C., and if it is left in a car in the summer, it is also expected to reach a high temperature of 70° C. or more.

Even under such conditions, in order to prevent deformation of the optical disc (mainly due to peeling of the bonded disc), the adhesive used has a high glass transition temperature Tg and a high modulus of elasticity at high temperatures.

[Problems to be solved by the invention] However, in the case of high-density, high-performance optical memories such as magneto-optical disks, when an adhesive with a high elastic modulus is used, an aging test of, for example, 70°C x 85% RH is performed. In this case, stress concentrates on the film laminated on the substrate, resulting in deterioration of the recording layer. That is, optical disks bonded together using adhesives with high elastic modulus have a drawback in terms of reliability.

It is an object of the present invention to solve these conventional drawbacks and provide an optical disc with high reliability.

[Means for Solving the Problems] In order to achieve the above object, the optical disk of the present invention has two magneto-optical recording layers each having an interference layer, a magneto-optical recording layer and a protective layer formed sequentially on a transparent substrate. In an optical disk in which the medium has a structure in which the respective protective layers face each other and are bonded by an adhesive, the elastic modulus G' of the adhesive is
is 1×106≦G'io・c≦l x at 20℃
10'dyne/cm", 2X at 70°C
to'≦ni'ya・e≦2 X 10@dyne/cm
'' and G's.・c/G', .°0≦50, and further, the end face portion of the substrate is bonded with a second adhesive.

[Example] The present invention will be described in detail below with reference to Examples.

First, nine types of adhesives having different elastic moduli as shown in Table 1 were prepared.

(Blank below C) [Function] In the present invention, an adhesive having an appropriate elastic modulus value is selected as the adhesive for bonding two magneto-optical media to form a double-sided optical disk. Therefore, the optical disc does not deteriorate even under harsh environments and can maintain high reliability.

The elastic modulus of the adhesive is, of course, the elastic modulus after curing, and was measured using a viscoelastic spectrometer by the shear method at a frequency of 10 Hz.

On the other hand, on a polycarbonate substrate 1 with a thickness of 1.2 mm,
0.07 μm thick interference film (inorganic protective film) made of LOII, SiNx, etc. 2, 0.08 μm thick magneto-optical recording film made of T, F, C, etc. 3 + 5 Inorganic protective film made of IOI+ 4° acrylic A number of magneto-optical recording media each having an organic protective film 5 made of UV-based resin were manufactured. Two media were bonded with the adhesive 6 shown in Table 1 with the organic protective films 5 facing each other to produce a double-sided optical disk as shown in FIG. The adhesive was applied by a heated roll coating method, and the thickness of the adhesive was 60 μm.

Nine types of optical disks manufactured using different adhesives in this manner were designated as Comparative Samples 1 to 9. Further, Example Samples 1 to 10 in which the outer peripheral end surfaces of these nine types of optical disks were adhered with adhesive 7
4 and comparative samples 10 to 16 were prepared. An epoxy adhesive is used to treat the end surfaces, and as shown in FIG.
Adhesion was made at 3 or 2 locations ranging from CII+.

After holding these various samples in a constant temperature and humidity chamber at 70°C and 85% RH for 2,000 hours, the state of corrosion of the recording film was observed.

The presence or absence of peeling of the disc was visually inspected.

Furthermore, the reproduction C/N of the recorded signal was measured and compared with the C/N before aging. These results are summarized in Table 2, and the contents of the three-level evaluation in Table 2 are as follows. In other words, regarding corrosion, compare the pinhole area with that before aging, and indicate ○ if it is 3 times or less, Δ if it is 10 times or less, and
Those exceeding 10 times were marked as ×. Regarding disc peeling and displacement, 1100 μm or less was rated as ◯, 300 μm or less as △, and over 300 μm as ×. Regarding reproduction of recorded signals, the C/N decrease due to aging, Δ
A C/N of 1 dB or less was marked ○, a C/N of 3 dB or less was marked Δ, and a C/N of more than 3 dB was marked X. In addition, 2kg/am", 5kg/ca+" and 10kg in the end face treatment tank in Table 2
/cm'' indicates the adhesive strength of the adhesive used for edge treatment.

As is clear from Table 2, after the 2,000-hour durability test, there was no corrosion of the recording film, no peeling or displacement of the disk, and the reproduction characteristics of the recorded signal were good. 2.3 and 4. Adhesives A, B, C and H used in these products all have an elastic modulus of 20°C.
In 1×106≦G'zo'e≦1 x 10'd
yne/cm", 2×10'≦G' at 70℃
ya・c≦2×10'dyne/cm", and G
's.・c/G゛7゜゜゜0≦50. That is, it is necessary that the adhesive has appropriate hardness and that the change between the value at room temperature and the value at 70° C. is small. Furthermore, as shown in Table 2, in addition to these appropriate adhesives, it is important to adhere the outer periphery of the optical disk. As is clear from the comparison between Example Sample 1 and Comparative Example Samples 11 and 12, it is desirable to use an adhesive with an adhesive strength of 5 kg/cm" or more for adhesion on the outer periphery, and to adhere at at least three points.
When using adhesives E, F, , G and I,
Even if the end face treatment is applied, it has no effect.

As a method of end face treatment, as shown in Fig. 2 (B),
(You can also glue the outer peripheries of the opposing surfaces of two media. The shallower the radial bonding range at this time, the better.)
, 1 mm or less is desirable.

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain an optical disc with good signal reproduction characteristics (and high reliability).

[Brief explanation of drawings]

FIG. 1 is a perspective view including a broken surface of an embodiment of the present invention; FIG. 2 is a sectional view illustrating end surface adhesion. l...optical disk substrate, 2... Inorganic protective film, 3... magneto-optical recording film, 4...Inorganic protective film, 5...Organic protective film, 6...Adhesive, 7... Edge adhesive, 8.9... Magneto-optical recording medium. 2:’l! H% coin 11 membrane 3X le magnetic recording pus 4; W^ Guarantee job 5. Tuned protective film 6.Tangential 41Pj 7; Akira Honjo (old row/1wTFfrJkBL needle view Figure 1) 9 (B) A map of the Zuro theater tour explaining the M-men greetings. No. figure

Claims (1)

[Scope of Claims] 1) Two magneto-optical recording media each having an interference layer, a magneto-optical recording layer and a protective layer sequentially formed on a transparent substrate,
In an optical disk having a structure in which the respective protective layers face each other and are bonded with an adhesive, the elastic modulus G' of the adhesive is 1×10^6≦G′_2_0_°C at 20°C.
≦1×10^7dyne/cm^2, 2 at 70℃
×10^5≦G′_7_0＿℃≦2×10^6dyne
/cm^2, and G'_2_0_℃/G'_7_0_℃
≦50, and further, an end surface portion of the substrate is bonded with a second adhesive. 2) The optical disk according to claim 1, wherein the adhesive force of the second adhesive is 5 kg/cm^2 or more, and the outer peripheral portion of the substrate is bonded at at least three locations. 3) The optical disc according to claim 1 or 2, wherein the recording layer contains an amorphous-rare earth transition metal alloy as a main component.