JP2882656B2 - optical disk - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical disk used for a magneto-optical memory, a magnetic recording, a display element, and the like, and particularly to an optical disk suitable as a memory for a computer.

[Prior Art] Magneto-optical memories capable of storing a large amount of information at high density and reading out information at high speed have been attracting attention in recent years. As this type of optical memory, an optical disk having a structure in which two magneto-optical recording media in which an interference layer, a magneto-optical recording layer, and a protective layer are sequentially formed on a transparent substrate, with the protective layers facing each other and bonded with an adhesive. Is often used. Optical disk for computer memory is ISO / DIS 9171, 10 ℃ ～ 50 ℃, long-term storage condition -10
℃ -50 ℃, short-term storage conditions -20 ℃ -55 ℃. However, during actual use, 60 ° C inside the disk drive
It is expected that the temperature will rise to about 70 ° C if left in a car during the summer.

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

[Problems to be Solved by the Invention] However, in the case of a high-density and high-performance optical memory such as a magneto-optical disk, if an adhesive having a high elastic modulus is used, an aging test of, for example, 70 ° C. × 85% RH is performed. In such a case, stress concentrates on the film laminated on the substrate, and as a result, the recording layer deteriorates. That is, the optical disk bonded with the adhesive having a high elastic modulus has a defect in reliability.

An object of the present invention is to solve such a conventional disadvantage and to provide an optical disk having high reliability.

[Means for Solving the Problems] In order to achieve such an object, an optical disk according to the present invention comprises two optical disks 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 a magnetic recording medium is bonded with an adhesive with the protective layers facing each other, the elastic modulus G ′ of the adhesive is 1 × 10 ⁶ ≦ G ′ _{20 ° C} ≦ 1 × at _{20 ° C.} 1
0 ⁷ dyne / cm ² , 2 × 10 ⁵ ≦ G ′ _{70 ° C} ≦ 2 × 1 at _{70 ° C.}
0 ⁶ dyne / cm ^2, and G _{'20 ° C} / G' is _{70 ° C} ≦ 50, further outer peripheral portion of the substrate is at least three places by a second adhesive bond strength is 5 kg / cm ² or more It is characterized by being adhered.

[Operation] In the present invention, an adhesive having an appropriate elastic modulus value is selected as an adhesive for forming a double-sided optical disk by bonding two magneto-optical media. Therefore, high reliability can be maintained without deterioration of the optical disk even in a severe environment.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples.

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

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

On the other hand, SiO _x ,
0.07μm thick interference film (inorganic protective film) made of SiN _x etc.
2, T _b F _e C magneto-optical recording film having a thickness of 0.08μm consisting _o 3, the inorganic protective film 4 made of SiO _x, was produced a large number of magneto-optical recording medium having an organic protective film 5 made of acrylic UV resin . Adhesive 6 shown in Table 1 with two media facing organic protective film 5
To produce a double-sided optical disk as shown in FIG. The adhesive is applied by the heated roll coating method.
The thickness of the adhesive was 60 μm.

Thus, nine kinds of optical disks produced by changing the adhesive were used as Comparative Example Samples 1 to 9. Example sample 1 in which the outer peripheral end surfaces of these nine types of optical disks were bonded with an adhesive 7
To 4 and Comparative Samples 10 to 16 were produced. An epoxy-based adhesive is used for the treatment of the end faces, and as shown in FIG.
Adhesion was made at three or two places over about m.

These various samples were placed in a thermo-hygrostat at 70 ° C and 85% RH for 2,000
After holding for a time, the state of corrosion of the recording film and the presence or absence of peeling of the disk were visually inspected. Further playback of recorded signals
C / N was measured and compared with C / N before aging. Table 2 summarizes these results. The contents of the three-level evaluation in Table 2 are as follows. That is, regarding the corrosion, the area of the pinhole was compared with that before aging, and the result was evaluated as 倍 when it was 3 times or less, Δ when it was 10 times or less, and × when it exceeded 10 times.
Regarding the peeling and displacement of the disk, を indicates 100 μm or less, Δ indicates 300 μm or less, and X indicates 300 μm or more. For playback of recorded signal, C / N due to aging
、, ΔC / N of 1 dB or less, Δ, 3 dB or less, and ΔC / N exceeding 3 dB. In addition, in the end face treatment column of Table 2,
2 kg / cm ² , 5 kg / cm ² and 10 kg / cm ² indicate the adhesive strength of the adhesive used for the end face treatment, respectively.

As is clear from Table 2, the samples of Examples 1 and 2 having good recording signal reproduction characteristics without corrosion of the recording film and peeling / displacement of the disk after the endurance test for 2,000 hours.
2, 3 and 4. Adhesive A used for these,
B, C and H all have a modulus of elasticity of 1 × 1 at 20 ° C.
0 ⁶ ≤ G '20 _{° C} ≤ 1 x 10 ⁷ dyne / cm ² , 2 x 10 at 70 ° C
⁵ ≤ G _{'70 ゜ C} ≤ 2 x 10 ⁶ dyne / cm ² and G' _{20 ゜ C} / G '
_{70 ° C} ≦ 50. That is, it is necessary that the adhesive has an appropriate hardness, and that the change between the value at normal temperature and the value at 70 ° C. is small. Further, as shown in Table 2, it is important to adhere the outer peripheral portion of the optical disk in addition to these appropriate adhesives. As is clear from the comparison between the sample of the example 1 and the samples of the comparative examples 11 and 12, an adhesive force of 5 kg / cm was applied to the outer peripheral portion.
It is desirable to use ^two or more adhesives and to adhere at at least three points. When the adhesives D, E, F, G and I are used, the end face treatment has no effect.

As an end face processing method, as shown in FIG. 2 (B), the outer peripheral portions of the opposing surfaces of the two media may be bonded instead of the outer peripheral side surfaces. At this time, the bonding range in the radial direction is preferably as small as possible, and is preferably 1 mm or less.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain an optical disk having good signal reproduction characteristics and high reliability.

[Brief description of the drawings]

 FIG. 1 is a perspective view including a broken surface of an embodiment of the present invention, and FIG. 2 is a cross-sectional view for explaining end surface bonding. DESCRIPTION OF SYMBOLS 1 ... Optical disk board, 2 ... Inorganic protective film, 3 ... Magneto-optical recording film, 4 ... Inorganic protective film, 5 ... Organic protective film, 6 ... Adhesive, 7 ... End face adhesive, 8, 9 ... Magneto-optical recording medium.

Claims (2)

(57) [Claims] 1. Two magneto-optical recording media in which an interference layer, a magneto-optical recording layer and a protective layer are sequentially formed on a transparent substrate are bonded with an adhesive with the protective layers facing each other. In an optical disk having a structure, the elastic modulus G 'of the adhesive at 20 ° C. is 1 × 10 ⁶ ≦ G ′ _{20 ° C} ≦ 1
× 10 ⁷ dyne / cm ² , 2 × 10 ⁵ ≦ G _{'70 ° C} ≦ 2 at _{70 ° C}
× 10 ⁶ dyne / cm ² , G ′ _{20 ° C} / G ′ _{70 ° C} ≦ 50, and the outer periphery of the substrate is bonded to at least three places with a second adhesive having an adhesive strength of 5 kg / cm ² or more. An optical disc characterized by being adhered by: 2. The optical disk according to claim 1, wherein said recording layer is mainly composed of an amorphous rare earth transition metal alloy.