JPH03278334A - Optical information recording medium and its production - Google Patents

Abstract

PURPOSE:To reduce warpage of disk plates during use by giving warpage to the optical disk at normal temp., and normal pressure so that the warpage of the disk decreases under conditions of low temp. and high pressure or high temp. and low pressure. CONSTITUTION:The optical disk 1 is formed to have warpage at normal temp., and normal pressure so that the warpage of the disk decreases under conditions of low temp. and high pressure or high temp. and low pressure. As for the optical information recording medium of air-sandwitch sealed structure to be used under low temp. and high pressure, the disk plates are preliminarily bent outwardly in the process of assembling the medium at normal temp. and normal pressure. On the other hand, if the medium is to be used under high temp. and low pressure, the disk plates are bent inwardly. Thereby, warpage of the plates 2 can be reduced during use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording medium having a sealed air sandwich structure and a method for manufacturing the same.

[Conventional technology]

2. Description of the Related Art Conventionally, optical information recording media have been known that have a sealed air sandwich structure in which the inner and outer peripheral parts of two plate-shaped bodies each containing at least one optical disk are bonded together via a gas layer.

This type of optical information recording medium is mounted on a turntable provided in a drive device and driven to rotate, and a light beam spot emitted from an optical head placed opposite to the optical disk is directed onto a recording track formed on the optical disk. Information is recorded/reproduced by detecting the reflected light flux from the optical disc. Therefore, if the optical disc is warped during use, the reflected light beam from the optical disc will be deviated from the photodetector, making normal information recording/reproducing operations difficult. Furthermore, focusing of the light beam spot becomes difficult, and high-speed seek performance deteriorates.

Furthermore, unreasonable force acts on the optical disc, which tends to cause problems such as destruction of the optical disc.

Therefore, conventionally, two discs including at least one optical disc are used.
An optical information recording medium with a sealed air sandwich structure is assembled by making the plate-shaped bodies parallel to each other, so that the plate-shaped bodies are maintained in an unwarped state during use.

[Problems to be Solved by the Invention] The conventional sealed air sandwich structure optical information recording medium described above does not cause any special problems when used in an environment of normal temperature and normal pressure or an environment similar to this. .

However, when this optical information recording medium is used in a low temperature or high pressure environment, or in a high temperature or low pressure environment, the plate-shaped body containing the optical disk will curve due to the pressure difference between the outside pressure and the gas layer, and the plate will bend in the low temperature or high pressure environment. The body curves inward,
In a high temperature or low pressure environment, the plate-shaped body is likely to warp outward, causing the various problems described above.

The present invention has been made in order to solve the above-mentioned deficiencies of the prior art, and the present invention reduces the warpage of the plate-shaped body when used in a low temperature or high pressure environment, or in a high temperature or low pressure environment. It is an object of the present invention to provide an optical information recording medium with excellent reproduction characteristics, high-speed seek performance, and durability, and a method for manufacturing such an optical information medium with high efficiency.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides, through a gas layer,
In an optical information recording medium having a sealed air sandwich structure in which two plate-shaped bodies each containing at least one optical disc are bonded together, the warping of the optical disc is reduced in an environment of low temperature or high pressure, or high temperature or low pressure. The optical disc was warped at room temperature and pressure.

In addition, in a method for manufacturing an optical information recording medium with a sealed Asaradwitch structure in which two plate-like bodies including at least one optical disk are bonded together via a gas layer, In order to minimize the warpage of the optical disc, a manufacturing method was adopted in which each member was assembled with the optical disc warped.

In addition, as another manufacturing method, each member is assembled in a state where the optical disc is not warped so that the warpage of the optical disc is reduced in a low temperature or high pressure environment, or a high temperature or low pressure environment, and then the air pressure in the gas layer is was adjusted to give the optical disc a warp.

[Effect]

When an optical information recording medium with a sealed air sandwich structure is placed in a low-temperature or high-pressure environment, the volume of the gas layer contracts and the optical disc is pressurized by external pressure, causing the plate-like body to curve inward. On the other hand, when an optical information recording medium with a sealed air sandwich structure is placed in a high-temperature or low-pressure environment, the volume of the gas layer expands and the external pressure that presses the optical disk decreases, causing the plate-like body to curve outward. do.

Therefore, for optical information recording media with a sealed air sandwich structure that is used in low-temperature or high-pressure environments, it is necessary to curve the plate-shaped body outward in advance when assembling the optical information recording medium in an environment of normal temperature and normal pressure. By doing so, it is possible to reduce the warping of the plate-like body during use. In addition, for optical information recording media with a sealed air sandwich structure that is used in high-temperature or low-pressure environments, when assembling the optical information recording media in an environment of room temperature and normal pressure, the plate-shaped body is curved inward in advance. By doing so, it is possible to reduce the warping of the plate-like body during use.

Furthermore, considering the conditions of use and transport of optical information recording media, it is possible to use them above ground (above sea level) at 3,000 m high altitudes, or to transport them by aircraft flying at high altitudes of 10,000 m or more; 30 at most
0 m, and the warping of the optical disc is overwhelmingly greater when it is used in a low-pressure environment. Therefore, when assembling the optical information recording medium in an environment of normal temperature and normal pressure, by curving the plate-shaped body inward by a predetermined amount in advance, it is possible to reduce the warpage of the plate-shaped body at high altitudes.
Moreover, the warpage of the plate-shaped body underground can be kept within the permissible range.

In this manner, by reducing the warpage of the optical disc, it is possible to provide an optical information recording medium that is excellent in recording/reproducing characteristics, high-speed seek performance, and mechanical strength.

Embodiment First, a first embodiment of the present invention will be explained with reference to FIGS. 1 and 2. The optical information recording medium of the first embodiment is of a type suitable for use in a low pressure or high temperature environment. .

FIG. 1 is a cross-sectional view showing the shape at normal temperature and pressure,
FIG. 2 is a cross-sectional view showing the shape under a low pressure or high temperature environment, in which 1 is an optical disk, 2 is a transparent substrate, 3 is a recording layer, 4 is a center hub, 5 is an inner spacer, 6 is an outer spacer, 7 indicates a gas layer.

The optical disc 1 is formed by depositing a recording layer 3 on the signal surface (inner surface) of a transparent substrate 2.

The transparent substrate 2 is made of glass or a transparent plastic material such as polycarbonate or polymethyl methacrylate, and is formed in the shape of a circular flat plate having a center hole 8 in the center. On the signal surface of the transparent substrate 2, the signal is preformatted in the form of fine irregularities, but since this is not directly related to the gist of the present invention, illustration is omitted to prevent the diagram from becoming complicated. do.

When the optical disc 1 is placed in a low-pressure or high-temperature environment, the two transparent substrates 2 are arranged so that they are approximately parallel to each other (
(See FIG. 2), the two transparent substrates 2 are bonded together with each other being warped inward at room temperature and pressure (FIG. 1). The method of bonding the transparent substrate 2 with the transparent substrate 2 bent inward is as follows: (1) combining two optical disks via the center hub 4, inner circumferential spacer 5, and outer circumferential spacer 6; Mechanically press the opposing positions. (2) In a reduced pressure environment, the two optical discs 1 are pasted together in parallel via the center hub 4, inner circumferential spacer 5, and outer circumferential spacer 6.

■In a high temperature environment, two optical discs 1 are
(2) storing an oxygen scavenger in the gas layer 7 of the air sandwich structure at room temperature and normal pressure, and then bonding the two optical disks 1 in parallel;

According to method (2), when the bonded optical information recording medium is exposed to an environment of normal temperature and normal pressure, the transparent substrate
can be curved inward.

Furthermore, according to the method (2), when the bonded optical information recording medium is exposed to an environment of normal temperature and normal pressure, the volume of air in the gas layer 7 decreases, and the transparent substrate 1 can be warped inward. Furthermore, according to the method (2), when the bonded optical information recording medium is left at room temperature and normal pressure, the oxygen in the gas layer 7 is absorbed by the oxygen scavenger, and the air in the gas layer 7 decreases, so that the optical disc 1 can be curved inward.

The recording layer 3 is made of a so-called write-once type heat mode material that records information only once by changing the physical shape of the recording layer, such as a low melting point alloy or an organic dye material, or a magneto-optical recording material or a phase-shifting material. So-called rewritable heat mode recording materials that repeatedly record information by reversibly changing the physical properties of the recording layer, such as variable recording materials.

It can be formed using any known recording material. Note that although the recording layer 3 is shown as a single layer in the figure,
A stack of a plurality of thin films made of different materials can also be used.

The center hub 4 is made of, for example, a metal material with excellent wear resistance or a magnetic metal material, and has a spindle hole 9 in the center thereof for mounting a turntable provided in a drive device. This center hub 4 is fitted into a center hole 8 formed in the transparent substrate 2 and bonded with an adhesive 10.

The inner circumferential spacer 5 and the outer circumferential spacer 6 are formed in a ring shape with a thickness sufficient to form a gas layer 7 of a desired size between the two optical disks 1.

The gas layer 7 can be filled with air, or can be filled with an inert gas instead of air.

When filling with air, using an oxygen absorber not only reduces the pressure in the gas layer 7 as described above, but also reduces the oxygen concentration in the air layer 7, thereby preventing corrosion of the recording layer 3. can do.

Oxygen absorbers include iron, aluminum, magnesium,
Metal powders that are relatively easily oxidized, such as manganese, are inexpensive and easy to use. A method of encapsulating the oxygen absorber in the gas layer 7 is to wrap the oxygen absorber in a capsule made of a resin film that easily transmits oxygen, such as cellophane, and fix it outside the recording area in the gas layer 7 with an adhesive or the like. Alternatively, a method in which a ring-shaped member is molded from a resin mixed with an oxygen absorber and this member is fitted into the gas layer 7, or a method in which the ring-shaped member is used as an inner peripheral spacer. The optical information recording medium is assembled in such a way that the optical disc curves inward under a normal temperature and normal pressure environment, so the optical disc warps less when placed under a low pressure environment or a high temperature environment.

Therefore, if the amount of warpage of an optical disk under normal temperature and normal pressure conditions matches the amount of return of warpage under the usage environment, it is possible to eliminate the warpage of the optical disk and improve the recording/playback characteristics of the optical information recording medium and the high speed. Seekability and further mechanical strength can be improved.

Next, a second embodiment of the present invention will be described with reference to FIG.

The optical information recording medium of the second embodiment is of a type suitable for use in a high-pressure environment or a low-temperature environment.

As shown in FIG. 3, the optical information recording medium of the second embodiment is
When placed under high pressure or low temperature environment, the two transparent substrates 2
The two transparent substrates 2 are bonded to each other with the two transparent substrates 2 warped outward at room temperature and normal pressure so that they are substantially parallel to each other (see FIG. 2). As a means of pasting together the transparent substrate 2 with the transparent substrate 2 warped outward, there are two methods: Mechanically pulling the opposing positions using a vacuum suction machine, etc.; ■ Attaching the two optical discs 1 in parallel to each other via the center hub 4, inner circumferential spacer 5, and outer circumferential spacer 6 in a high-pressure environment. In a low temperature environment, through the center hub 4, inner spacer 5, and outer spacer 6,
A method such as bonding two optical discs 1 parallel to each other can be adopted.

According to method (2), when the bonded optical information recording medium is exposed to a room temperature and normal pressure environment, the transparent substrate 1 can be warped outward due to the difference between the air pressure within the gas layer 7 and the outside air pressure. Furthermore, according to the method (2), when the bonded optical information recording medium is placed in an environment at room temperature and pressure, the volume of air in the gas layer 7 expands, making it possible to warp the transparent substrate 1 outward.

The other members are the same as those in the first embodiment, so in order to avoid duplication of explanation, corresponding members will be denoted by the same reference numerals and the explanation will be omitted.

Since the optical information recording medium of the second embodiment is assembled so that the optical disk is curved outward in an environment of normal temperature and normal pressure, the warpage of the optical disk is reduced when placed in a high pressure environment or a low temperature environment. Therefore, by matching the amount of warpage of the optical disc 1 under normal temperature and normal pressure environment with the amount of warpage return under the usage environment, the warpage of the optical disc can be eliminated, and the recording/playback characteristics of the optical information recording medium and high speed can be improved. It is possible to improve sheave properties and further improve mechanical strength.

Next, a third embodiment of the present invention will be described with reference to FIG. The optical information recording medium of the third embodiment can be used not only in a high-pressure environment or a low-temperature environment, but also in a low-pressure environment or a high-temperature environment.

Permissible operating conditions (temperature and atmospheric pressure) for optical information recording media are determined by taking into consideration the weather conditions during use and transportation. For example, in consideration of use at high altitudes or deep underground, the allowable temperature condition is 10°C to 50°C, and the allowable pressure condition is 75 K.
When P a is set to 105 KPa, the optical disc bulges outward the most when the temperature is 50° C. and the atmospheric pressure is 75 KPa, and the optical disc dents inward the most when the temperature is 1.0' C and the atmospheric pressure 105 KPa. However, since optical information recording media are usually assembled so that two optical disks are parallel to each other in an environment of normal temperature and pressure of 20 degrees Celsius and atmospheric pressure of 101 KPa, when placed in an environment of 50 degrees Celsius and 75 KPa of atmospheric pressure, The amount of deformation of the optical disc is greater than the amount of deformation of the optical disc when the temperature is 10 degrees Celsius and the atmospheric pressure is 1.
This is much larger than the amount of deformation of an optical disc when placed under an environmental condition of 0.05 KPa.

Optically, whether an optical disk bulges outward or dents inward, the smaller the amount of deformation, the better.
By indenting the optical disk inward during assembly, the amount of bulge of the optical disk under high temperature and low pressure,
The amount of dent in the optical disc under low temperature and high pressure can be made equal. As a result, the amount of bulge of the optical disk under high temperature and low pressure can be reduced, and even when used under low temperature and high pressure, the amount of denting of the optical disk can be suppressed to the same level as the amount of bulge.

The optical information recording medium of the third embodiment is constructed based on the above technical idea, and as shown in FIG.
By indenting the optical disc 1 inward by a predetermined amount during assembly, the amount of bulge Q1 of the optical disc under high temperature and low pressure is made equal to the amount of denting Ω of the optical disc under low temperature and high pressure.

According to the optical information recording medium of the third embodiment, the gap G of the gas layer 7 is 0.46 mm, the outer diameter D1 of the inner spacer 5 is 93 mm, the inner diameter of the outer spacer 6 is 290 mm, and the thickness of the transparent substrate 2 t is 1° rom, and the bending rigidity of the transparent substrate 2 is 9.48 N/m.

When the Poisson's ratio of the transparent substrate 2 is 0.24, the temperature is 5.
Swelling amount Q1 of an optical disk placed under an environmental condition of 0'C atmospheric pressure 75KPa and 6Aio'c atmospheric pressure 105K
The amount of denting Q of the optical disc placed under the environmental condition of Pa,
Both can be set to 0.85 mm. The maximum tilt angle θ, θ of the transparent substrate 2 at this time is 2.85 mrad.

As a means for inwardly indenting the optical disc 1 during assembly, the means listed in Example 1 can be used.

In each of the embodiments described above, a so-called single-sided recording type optical information recording medium in which two optical discs 1 are combined via a center hub 4, an inner circumferential spacer 5, and an outer circumferential spacer 6 was explained as an example. As shown in FIG. 5, one optical disc 1 and one protective plate 11 are bonded together via a center hub 4, an inner circumferential spacer 5, and an outer circumferential spacer 6, so-called single-sided recording type optical information recording. The present invention can also be applied to media.

Furthermore, in each of the above embodiments, the optical information recording medium is assembled with the optical disc 1 warped, but first, the optical information recording medium is assembled with the optical disc 1 unwarped, and then the inside of the gas layer 7 is It is also possible to warp the optical disc 1 by adjusting the air pressure. In this case, the sixth
As shown in the figure, a through hole 12 communicates the outside air with the gas layer 7.
After assembling an optical information recording medium using the outer circumferential spacer 6 in which a The gas layer 7 can also be sealed by filling the through hole 12 with an adhesive.

In addition, the gist of the present invention is that the optical disc 1 and the protection plate 11 are curved outward or inward, and the transparent substrate 2, the center hub 4, the inner peripheral spacer 5,
The shape, material, etc. of the outer spacer 6 can be arbitrarily designed regardless of the embodiments described above.

〔Effect of the invention〕

As explained above, according to the present invention, since the optical disc is warped at room temperature and normal pressure, it is possible to reduce the warpage of the optical disc when the optical information recording medium is placed in an environment of low temperature or high pressure, or high temperature or low pressure. This makes it possible to improve the recording/reproducing characteristics, high-speed seek performance, and mechanical strength of the optical information recording medium.

Furthermore, since the optical disc is warped during assembly of the information recording medium, the optical information recording medium can be manufactured with higher efficiency than when the optical disc is warped after the information recording medium is assembled.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an optical information recording medium according to an example;
FIG. 2 is a sectional view of the optical information recording medium in use, FIG. 3 is a sectional view of the optical information recording medium according to the second embodiment, FIG. 4 is an explanatory diagram of the optical information recording medium according to the third embodiment, and FIG. 5 6 is a cross-sectional view of an optical information recording medium according to another embodiment of the present invention, and FIG. 6 is a cross-sectional view of an optical information recording medium according to still another embodiment of the present invention. l...Optical disk, 2...Transparent substrate, 3...
...Recording layer, 4... Center hub, 5...
...Inner circumference spacer, 6...Outer circumference spacer, 7...
...Gas layer, 8...Center hole, 9...
... Spindle hole, 10 ... Adhesive, 11
...Protection plate, ]2...Through hole.

Claims (9)

[Claims] (1) In an optical information recording medium with a sealed air sandwich structure in which two plate-like bodies containing at least one optical disk are bonded together via a gas layer, under a low temperature or high pressure environment, or a high temperature or low pressure environment. An optical information recording medium characterized in that the optical disc is warped at normal temperature and pressure so that the warpage of the optical disc is reduced. (2) Warpage of the optical disc according to claim 1 at the highest pressure and lowest temperature of allowable environmental conditions;
Optical information recording characterized in that the warp direction and the amount of warp of the optical disc at room temperature and normal pressure are adjusted so that the warp of the optical disc at the lowest atmospheric pressure and the highest temperature is opposite to the warp direction and has the same amount of warp. Medium. (3) In a method for manufacturing an optical information recording medium with a sealed air sandwich structure in which two plate-shaped bodies including at least one optical disk are bonded together via a gas layer, the environment is low temperature or high pressure, or high temperature or low pressure. A method for manufacturing an optical information recording medium, characterized in that each member is assembled with the optical disc being warped so that the warpage of the optical disc is reduced at the bottom. (4) Optical information according to claim 3, characterized in that mechanical addition is applied to the optical disc and the optical disc is bonded together so that warpage of the optical disc is reduced in a low temperature or high pressure environment, or in a high temperature or low pressure environment. A method for manufacturing a recording medium. (5) In claim 3, when the optical disk is bonded together in a non-warped state under a reduced pressure environment so that the warpage of the optical disk is reduced under a high temperature or low pressure environment, and the optical disk is placed in a normal temperature and normal pressure environment. A method of manufacturing an optical information recording medium, characterized in that the optical disc is warped. (6) In claim 3, when the optical disc is bonded together in a non-warped state under a high temperature environment so that the warpage of the optical disc is reduced under a high temperature or low pressure environment, and the optical disc is placed in a normal temperature and normal pressure environment. A method of manufacturing an optical information recording medium, characterized in that the optical disc is warped. (7) In claim 3, when the optical disk is bonded together in a non-warped state under a high pressure environment so that the warpage of the optical disk is reduced under a low temperature or high pressure environment, and the optical disk is placed in a normal temperature and pressure environment. A method of manufacturing an optical information recording medium, characterized in that the optical disc is warped. (8) In claim 3, when the optical disc is bonded together in a non-warped state in a low temperature environment so that the warpage of the optical disc is reduced in a low temperature or high pressure environment, and the optical disc is put out in a normal temperature and normal pressure environment. A method of manufacturing an optical information recording medium, characterized in that the optical disc is warped. (9) In a method for manufacturing an optical information recording medium with a sealed air sandwich structure in which two plate-like bodies including at least one optical disk are bonded together via a gas layer, the method is performed in a low-temperature or high-pressure environment, or in a high-temperature or low-pressure environment. Each member is assembled in a state where the optical disc is not warped so that the warpage of the optical disc is reduced at the bottom, and then the air pressure in the gas layer is adjusted to cause the optical disc to warp. A method for manufacturing an optical information recording medium.