JPS61289560A - Optical disk - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a functional film by constituting a thin inorg. glass film layer of alkali-free glass contg. a specific ratio of an alkaline metal. CONSTITUTION:The thin inorg. glass film layer of a high-density information recording carrier consisting of a transparent plastic substrate, the thin inorg. glass film layer formed on the substrate and the high-density information recording layer formed on the thin inorg. glass film layer is constituted of the alkali- free glass contg. the alkaline metal, i.e. Li, Na, K, Rb or Cs perferably at <=0.8wt% only in therms of an alkaline earth metallic oxide. The alkali-free glass exlcudes so-called silicicate glass consisting of SiO2 alone and the thickness of the thin alkali-free glass is preferably 100-2000Angstrom . Hygroscopic deformability and moisture resistance are thereby improved and the deterioration of the functional film arising from the substrate is prevented. The optical information recording carrier which is stable for a long period and has small EBR is thus obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a high-density information recording carrier used in an optical recording/reproducing device that records/reproduces information using laser light. The present invention relates to a high-density information recording carrier made of plastic that has excellent durability, and further relates to a high-density information recording carrier for magneto-optical recording and reproduction that has excellent magneto-optical properties.

(Prior Art) Regarding optical discs, the most important technical point at present is how to improve durability, that is, reliability when using a plastic substrate.

In other words, a recording layer formed on a plastic substrate, which has various advantages over a glass substrate, is subject to deterioration or deterioration due to moisture or monomer remaining in the plastic substrate, or moisture entering through the plastic substrate. There was a drawback.

The present inventor proposed a method for solving the above-mentioned drawbacks in Japanese Patent Application No. 59-32230 entitled "Optical Information Recording Carrier" filed on February 22, 1980, in which there is no gap between the plastic substrate and the recording layer. It was proposed to provide a thin film of alkali glass.

Although this method amazingly increases the durability of optical discs and is completely satisfactory, the present inventors have further developed the above invention to improve the BER (Bi Citoera+Rate) while maintaining durability. ), and completed the present invention.

(Object of the invention) The object of the present invention is to solve the above-mentioned conventional problems.
A glass-like plastic substrate is used to improve smoothness, hardness, moisture absorption deformability, and moisture resistance to prevent deterioration of the functional film based on the substrate, thereby providing an optical information recording carrier that is stable over a long period of time and has a low EBR. There's K things to do.

Another object of the present invention is to provide an optical information recording carrier that uses a rare earth-transition metal amorphous alloy as the functional film and has greatly improved magneto-optical properties.

(Structure of the Invention) The present invention provides a high-density information recording carrier comprising a transparent plastic substrate, an inorganic glass thin film layer formed on the substrate, and a high-density information recording layer formed on the inorganic glass thin film layer. In which the inorganic glass thin film layer contains an alkali metal,
That is, Li, Na, Rb, and Cs are not more than 1% by weight, preferably 0.8% by weight in terms of alkali metal oxides.
It is characterized by being composed of alkali-free glass that contains only the following:

The above-mentioned transparent plastic substrate and high-density information recording layer used in the present invention are disclosed in the above-mentioned Japanese Patent Application No. 59-322 filed by the present applicant.
Since it is explained in detail in the specification of No. 30, it will be cited here and the details will be omitted.

A feature of the present invention is that the amount of alkali metal in the alkali-free glass is 1% by weight or less, preferably 0.8% by weight or less in terms of alkali metal oxide.

In theory, the alkali-free glass thin film of the present invention can be prepared by any method, such as multiple Although each component of the above alkali-free glass may be simultaneously vapor-deposited from a vapor deposition source of It is preferable to form it on a plastic substrate using.

The amount of alkali metal is 1% by weight in terms of alkali metal oxide.
If it exceeds, cracks will occur in the recording layer and the BER will increase. The reason for this is not clear, but it is thought that the alkali metal reacts with moisture or monomer passing through the plastic substrate or with moisture in the outside air and deteriorates the recording layer. It is more preferable that the content of this alkali metal is 0.8% by weight or less in terms of alkali metal oxide, and it is preferable that the amount is less as long as the properties of the glass are not impaired. However, industrially it is difficult to reduce the alkali metal content to zero, and there is no practical problem if it is 1% by weight or less.

Note that the alkali-free glass of the present invention does not include so-called silicate glass consisting only of 5 iOz. That is,
Although it is well known that 5 iOz is deposited alone as a moisture-resistant protective layer, this silicate glass thin film has almost no moisture resistance.

The thickness of the alkali-free glass thin film of the present invention is 100 to 2.0
OOA is preferable; if it is less than 100 A, the protective role is insufficient, and if it exceeds 2,0 A, problems such as laser absorption will occur, and it is also not economical.

In the present invention, the high-density information recording layer includes, for example, Tb,
It is particularly preferable to apply this method to an optical disk using a magneto-optical recording material made of an amorphous alloy of a rare earth-transition metal such as Fe or Co, but it is susceptible to deterioration due to monomers in the plastic, moisture, and/or moisture from the outside. It is clear that it is applicable to all other high density recording carriers using recording materials.

It goes without saying that the protective layer of the alkali-free glass thin film of the present invention can also be formed on the outside of the recording layer, that is, on the opposite side to the substrate, to shield the recording layer from the outside air.

The present invention will be explained below using examples.

(Example) As plastic substrates, an acrylic substrate (PMMA) with a thickness of 1.211 m and a polycarbonate substrate (PC) were prepared. On these substrates, inorganic glasses having the compositions shown in Table 1 were formed by sputtering using a sputtering device (RF magnetron battering device manufactured by Japan Vacuum Technology Co., Ltd.) to form a thin film with a thickness of 500A, and then Gd O
, 12Tb0.12 Fe0.76 was formed to a thickness of 1000A using the sputtering apparatus described above, and the same inorganic glasses were further sputtered using the same method as above to form a thin film layer of 1000A in thickness. did.

The obtained magneto-optical disk was evaluated by heating the disk at 45℃, 9
The EBR and C/N change rate after maintaining at 0 PH% for 30 days were judged based on the results, and the results are shown in Table 1.

As can be seen from Table 1, when the alkali metal (Na) is 1% by weight or less in terms of alkali metal oxide (NazO), the EBR becomes small.

Table 1 Patent questioner Daicel Chemical Industries, Ltd. Procedural amendment 1985 July 1st, 1985 Indication of case 1985 Wu Xu Y/Tao ZI41?42, Name of invention Optical disk 3, Person making the amendment Relationship to the case Patent applicant address 1 Teppo-cho, Sakai City, Osaka Name (290) Daicel Chemical Industries, Ltd. 4 Subject of amendment Go to 'Detailed description of the invention in the specification, brief description of the drawings 5 , Details of correction 1) rEBRJ on page 3, line 17, page 8, line 1 and line 6 of the specification is corrected to rBERJ.

2) Correct r Tb, Fe, Co J on page 6, line 15 to r TbFeCo J.

3) Correct "Example" in the 7th line of page 7 to "Example 1".

4) Add the following Example 2 next to the 6th line of the 8th page.

(Example 2) The same operation as in Example 1 was repeated, but the film thickness of the glass of sample A in Table 1 of Example 1 was changed to 250.500.750.
1000.

2000X was used instead, and was formed on a polycarbonate substrate. In this case, each BER of the magneto-optical disk after being maintained at 45° C. and 90 RH for 30 days is shown in FIG. 5) Add the following after Table 1 on page 9.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the thickness of the glass protective film shown in Example 2 and the BEH of the magneto-optical disk after 30 days at 45° C. and 90 RH%. 6) Add the attached “Figure 1”.

Claims (1)

[Claims] 1) In a high-density information recording carrier comprising a transparent plastic substrate, a high-density information recording layer formed on this substrate, and an inorganic glass thin film layer provided between the substrate and the recording layer, the inorganic A high-density information recorder characterized in that the glass thin film layer is composed of alkali-free glass containing less than 1% by weight of alkali metals in terms of alkali metal oxides.