JPH07134880A - Optical recording medium - Google Patents

Abstract

PURPOSE:To greatly improve a preservation stability of a medium to an environmental light, to lighten the medium and to make it easy to handle the medium by providing a jacket with a metallic film layer, and shutting the medium inside the jacket, from an external light. CONSTITUTION:A jacket for an optical recording medium has a medium with a recording layer reacting to the photon mode and a plastic jacket to surround and hold the medium. The jacket is provided with a metallic film layer of, e.g. Al, Cu, silver or the like to shut the medium from an external light. The metallic film layer is formed at an area where the medium can be shut from the external light, for instance, at a part where an upper shell 2 and a lower shell 3 confront surfaces of a disc 1. The metallic film layer is preferably 0.05-10mum thick, and more preferably about 0.1-0.2mum thick.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a medium having a recording layer which reacts in the photon mode, and more particularly to an optical recording medium having a plastic jacket for enclosing and holding the medium. It is about.

[0002]

2. Description of the Related Art In recent years,
Photochromic optical recording utilizing a photon mode reaction as a rewritable optical recording medium has been actively researched. When a photochromic material is irradiated with light of a predetermined wavelength, the structure of the molecule changes due to a photochemical reaction, which causes changes in optical characteristics such as absorbance and refractive index for light of a specific wavelength, as well as light and heat of other wavelengths. When added, the changed molecular structure returns to its original state. Therefore, the recording of the photochromic optical recording medium is performed by the change of the molecular structure due to the irradiation of the light of the specific wavelength, and the reproduction is performed by detecting the change of the optical characteristics, particularly the change of the absorbance. In photochromic optical recording,
It is expected that higher density recording than before can be achieved by performing multiplex recording by making the most of the flexibility of light such as wavelength and polarization.

As a method of handling such a photon mode optical recording medium, there is a method of storing the optical recording medium in a plastic jacket currently used for magneto-optical disks such as floppy disks and mini disks. Since photon mode optical recording occurs by photochemical reaction, it is necessary not only to directly expose it to sunlight but also to shield light from ordinary fluorescent lamps in a room. Conventionally, whether or not the light-shielding performance of a plastic jacket used for a floppy disk or the like is sufficient to retain the information recorded on the photon mode optical recording medium has not been examined at all.

It is an object of the present invention to provide a novel structure of a plastic jacket capable of storing information recorded on such a photon mode optical recording medium for a long time.

[0005]

The present inventor has repeatedly studied the storage stability of the recorded information of the photon mode optical recording medium and the material and characteristics of the plastic jacket, and as a result, it has been used for the conventional floppy disk, mini disk and the like. With a plastic jacket that has been
It was found that the photon mode optical recording medium is completely inadequate, and it is necessary to provide a plastic jacket with a metal film layer for blocking external light, and completed the present invention.

That is, the optical recording medium of the present invention comprises a medium having a recording layer which reacts to the photon mode and a plastic jacket for surrounding and holding the medium, and the jacket shields the medium from external light. It is characterized in that a metal film layer for the purpose is provided.

In the present invention, the material of the metal film layer formed on the plastic jacket is not particularly limited as long as it can block external light, but for example, aluminum, copper, silver, gold, titanium, etc. Can be used. The metal film layer can be formed by a vacuum vapor deposition method, a sputtering method, coating a solvent in which metal fine particles are dispersed, or the like.

In the present invention, the thickness of the metal film layer is
The thickness is preferably about 0.05 to 10 μm, more preferably about 0.1 to 0.2 μm. Further, in the present invention, the region where the metal film layer is formed is a region capable of blocking the medium from external light, and is formed on the surface of the plastic jacket facing the surface of the medium on which the recording layer is provided. Is preferred. Therefore, it is usually preferable to form the inside of the jacket, that is, the back side, but if necessary, the metal film layer may be formed outside of the jacket, that is, on the front side.

[0009]

In the present invention, the medium in the jacket is shielded from external light by providing the metal film layer on the jacket. Therefore, storage stability against light in the environment can be significantly improved.

Further, in the present invention, external light is blocked by the metal film layer, and even if the metal film layer is a very thin layer, external light can be blocked, so that the jacket itself is lightweight,
It will be easy to handle.

[0011]

EXAMPLES First, the light shielding effect of the metal film layer provided on the jacket in the present invention was examined. The light-shielding performance was measured by forming a metal film layer inside a shell on one side of a plastic jacket of a floppy disk or magneto-optical disk as shown in FIG. In FIG. 2, the disk 1 is rotatably held by being sandwiched by an upper shell 2 and a lower shell 3, and the disk 1 is supported by a clam plate 6. A shutter 4 is provided on the upper shell 2 and the lower shell 3 that sandwich the disc 1, and the shutter 4 is locked by a shutter lock 5. A write protector 7 is attached to the lower shell 3 to prevent writing. The upper shell 2 and the lower shell 3 are fixed by a fixing screw 8. In the present invention, the metal film layer can be formed, for example, on the portions of the upper shell 2 and the lower shell 3 that face the surface of the disk 1. As for the lower shell 3, the metal film layer 3 can be formed in the hatched area in FIG. Although not shown in the upper shell 2,
A metal film layer can be formed in a similar region on the back side thereof. Here, the metal film layer was provided on the back sides of the upper shell 2 and the lower shell 3 as described above, and the light shielding performance was evaluated.

The shell of the jacket used was black, which is considered to have the lowest light transmittance. First, the light-shielding performance was evaluated without providing the metal film layer. The light-shielding performance was evaluated using a device as shown in FIG. Referring to FIG. 3, light having a wavelength of about 600 nm is extracted from the halogen lamp 11 by the filter 12, and this light is applied to the surface of the sample 13 which is the shell of the jacket by about 1 mW / cm 2.
Irradiation was performed at an intensity of ^{2, and} the intensity of transmitted light was detected and measured by the detector 14. As a result, the transmitted light intensity of the shell of the jacket without the metal film layer is about 0.1 to 1 μW.
It was about.

Next, an aluminum film having a thickness of 0.1 to 0.2 μm was formed on the inside of the shell of the jacket by the vacuum deposition method, and the light shielding performance was measured in the same manner as above. As a result, it was found that the transmitted light intensity was about 0.1 to 1 nW, which was reduced to about 1/1000. As for the metal film layer, copper, silver, gold, and titanium are similarly deposited by vacuum deposition to a film thickness of 0.1 to 0.2 μm.
The same result was obtained when the light-shielding performance was measured by forming the film with a thickness of.

As is clear from the above, the light shielding performance can be greatly improved by providing the metal film layer on the jacket. Next, the recording storage performance of the optical recording medium was evaluated. As the optical recording material contained in the recording layer of the optical recording medium, a diarylethene-based photochromic material represented by the following molecular structure was used.

[0015]

[Chemical 1]

FIG. 4 shows the absorption spectrum of the photochromic material. In FIG. 4, the solid line shows the absorption spectrum of the ring-closed body, and the dotted line shows the absorption spectrum of the ring-opened body. When the ring-opened product is irradiated with blue light having a wavelength of about 450 nm, a ring-closing reaction occurs and the absorption spectrum shown by the solid line changes. Further, when a ring-closed body having an absorption spectrum as shown by a solid line is irradiated with red light having a wavelength of about 550 to 650 nm, a ring-opening reaction occurs and the state of the absorption spectrum as shown by the original dotted line is restored. Therefore, for example, an information signal can be recorded by setting the closed ring body indicated by the solid line to the initial state and irradiating the HeNe laser light having a wavelength of 633 nm with a pulse in accordance with the recording signal to cause a photochromic reaction in the photon mode. Further, it is possible to reproduce the recorded signal by irradiating the same laser light with a low power of a certain level and detecting the reflectance change.

The above photochromic material was mixed with polystyrene resin, dissolved in cyclohexanone, and applied on a glass disk substrate with a groove of 3.5 inches by spin coating to form a recording layer with a thickness of 0.3 μm. . A silver reflective film was formed on this recording layer by a vacuum vapor deposition method, and a protective film made of an ultraviolet curable resin was further formed on this silver reflective film. FIG. 5 is a sectional view showing the optical recording medium thus formed. Referring to FIG. 5, a recording layer 101 containing the photochromic material is formed on a glass disk substrate 100, and a silver reflection film 102 and a protective film 103 are formed on the recording layer 101.

The disc sample obtained as described above was incorporated into a jacket of a commercially available 3.5-inch magneto-optical disc as shown in FIG. 2 to prepare an experimental sample. As an example, a sample in which an aluminum film (film thickness 0.2 μm) was formed inside the upper shell and the lower shell of the plastic jacket, that is, on the back side, was used in the same manner as described above. Further, as a comparative example, a sample using an upper shell and a lower shell on which such an aluminum film is not formed was prepared.

The disk samples of these Examples and Comparative Examples were rotated at a relative speed of 1.4 m / sec, and a HeNe laser having a wavelength of 633 nm was intensity-modulated with a recording signal having a frequency of 400 kHz for recording. Recording power is 2
It was set to mW. With respect to the sample recorded in this way, an irradiation intensity of 10 mW /
The sample was irradiated with light under a condition of cm ² and stored for a certain period of time, and then reproduced with a reproducing power of 30 nW, and the CN ratio was measured. If the light-shielding performance is not sufficient, it is expected that the non-recorded portion gradually reacts with light irradiation, resulting in a decrease in CN ratio.
Such light irradiation and measurement of the CN ratio were repeated, and the relationship between the storage time and the CN ratio is shown in FIG.

As shown in FIG. 1, in the sample of the comparative example in which the metal film layer was not formed, the CN ratio was decreased by 3 dB, but it was about 100 minutes. In the sample of the example, the CN ratio is 3d after 5 × 10 ⁵ minutes.
It has fallen to B. Therefore, the storage time of the sample of the example is 5000 times longer than that of the comparative example. Therefore,
It can be seen that the storage stability is significantly improved when the jacket having the metal film layer of the example is used.

Although an aluminum thin film is used as the metal film layer in the above embodiment, the present invention is not limited to this, and other kinds of metals can be used. Further, in the above embodiment, the metal film layer is formed on the back surface of the plastic jacket, that is, on the disk side, but the metal film layer may be formed on the outside. Further, the same effect can be obtained by a sandwich structure in which the metal film layer is sandwiched between plastic plates.

[0022]

According to the present invention, by providing the jacket with a metal film layer for shielding the medium from external light, the storage stability of the record recorded on the medium can be greatly improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a storage time and a CN ratio in an example according to the present invention.

FIG. 2 is an exploded perspective view showing an example of a plastic jacket.

FIG. 3 is a schematic configuration diagram for explaining a method of measuring light shielding performance performed in Examples.

FIG. 4 is a diagram showing an absorption spectrum of a photochromic material used in Examples according to the present invention.

FIG. 5 is a sectional view showing a sectional structure of an optical recording medium created in an example according to the present invention.

[Explanation of symbols]

 1 ... Disc 2 ... Upper shell 3 ... Lower shell 100 ... Glass disc substrate 101 ... Recording layer 102 ... Silver reflective film 103 ... Protective film

Claims (1)

[Claims] 1. An optical recording medium comprising a medium having a recording layer which reacts in a photon mode, and a plastic jacket for surrounding and holding the medium, wherein the jacket is for shielding the medium from external light. An optical recording medium comprising a metal film layer.