JPH05274714A - Information recording medium - Google Patents

Abstract

PURPOSE:To enable exact data reproduction and tracking servo by forming a metallic film on a second information recording layer, by which incident light is mostly reflected by this metallic film and the light transmission to a protective film is eliminated. CONSTITUTION:This information recording medium is formed by successively laminating a first information recording layer 2, the second information recording layer 3 and the metallic film 4 having a high reflectivity by a sputtering method or vapor deposition method. The reflected light 7 at the boundary between a substrate 1 and the recording layer 2, the reflected light 8 at the boundary between the recording layers 2 and 3 and the reflected light 9 at the boundary between the recording layer 3 and the metallic film 4 cause multiple interferences with each other and appear as reproducing light 10 if the laser beam 6 is emitted from the substrate side. The metallic film 4 has high light absorptivity and prevents the laser beam 6 from arriving at the protective film 5 formed thereon. The metallic film prevents the interference of this light beam with the reflected light beams 7, 8, 9 even if the laser beam arrives at the protective film. Then, the noise by the reflection from the protective film 5 is not applied to the reproducing waveforms and the exact data reproduction is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium in which an information recording layer is provided on a substrate, laser light is irradiated, and information is recorded and reproduced by utilizing the change in reflectance of the irradiated portion. ..

[0002]

2. Description of the Related Art Recently, an information recording medium capable of writing and reading information by irradiating a laser beam has been proposed. This is for recording information by utilizing the optical characteristics of the material forming the information recording medium, for example, changes in reflectance, transmittance, refractive index and the like. For example, JP-A-62-53
Japanese Patent No. 886 discloses a first information recording layer made of three elements of Ge, Sb, and Te, which has a characteristic that the absorption coefficient of light changes when heated, and a reflection having a metal such as Bi, Te, Sb, or an alloy thereof. An information recording medium having a second information recording layer as a layer is disclosed.

FIG. 3 is a sectional view of a conventional information recording medium 100.

This information recording medium 100 has a light-transmitting substrate 101 on which G has a small light absorption rate for laser light.
a first information recording layer 102 formed of a compound of e, Sb, and Te, and a compound having a metal such as Bi, Te, Sb, or an alloy thereof, which has a higher light absorption property to the laser light than the information recording layer 102. The formed second information recording layer 103 is formed, and a UV-curable resin is spin-coated on the second information recording layer 103, and then a cured protective film 105 is formed.

Here, the first information recording layer 102 and the second information recording layer 103 are laminated so that the recording signal is maximized, and the transmittance of the used laser beam 106 is 7%. is there. Therefore, the laser light 106 is emitted from the substrate 101.
When irradiated from the side, 7% of this laser light passes through the first information recording layer 102 and the second information recording layer 103, and the transmitted light is reflected at the interface between the protective film 105 and air. The reflected light 110 becomes reflected light 107, 108, 1
The reproduction light 116 becomes a reproduction light 116 that is added to 09 and causes multiple interference.

Also, an adhesive is provided on the protective film 105,
Light reflected by this adhesive may be added.

As described above, in such an information recording medium, the noise caused by the reflection from the protective film 105 provided on the information recording layers 102 and 103 affects the reproduced waveform, and the data can be reproduced accurately. There was a problem that I could not.

Further, in such an information recording medium, if there is coating unevenness on the protective film 105, there is a problem that reproduction of data is adversely affected. This will be described below.

FIG. 4 is a plan view of the information recording medium with the protective film 105 formed and a partial sectional view of the substrate 101.

The protective film 105 is formed by applying a liquid coating agent to the surface of the second information recording layer 103 by a spin coating method and then shaking it off by a centrifugal force. Therefore, the foreign matter 111 is not formed on the surface of the second information recording layer 103 or in the liquid.
When such substances are mixed in, uneven coating A, B, C may occur.

By the way, the guide groove 1 is previously formed on the substrate 101.
13 is formed and the spot 115 focused by an objective lens (not shown) is scanned in the circumferential direction D. In such an information recording medium, the guide groove 11 is formed.
Only by the diffraction interference of the light in the uneven portion of 3, the reproduction light 116
Needs to change.

FIG. 5 shows the amount of reproduction light on the detector of the optical head and the push-pull signal when the focused spot 115 by the laser beam emitted from the optical head scans the guide groove 113 while tracking. is there.

The reproducing light quantity shown in FIG. 5A is a normal track sum signal, and the push-pull signal shown in FIG. 5B is a normal track difference signal.

As shown in FIG. 4, if there are coating irregularities A, B, and C on the protective film 105, in addition to the diffraction interference effect at the uneven portion of the guide groove 113, the influence of the coating irregularities is added, and the reproduction light amount ( Disturbances A1, B1, and C1 occur in the track sum signal), and at the same time, disturbances A2, B2, and C2 occur in the push-pull signal (track difference signal).

Therefore, the reflected light 110 is the reflected light 10
In addition to 7, 108, and 109, multiple interference occurs, and the reproduction light 116 fluctuates even at portions other than the uneven portion of the guide groove 113, and the tracking performance deteriorates.

[0016]

As described above, in such an information recording medium, the noise caused by the reflection from the protective film 105 provided on the information recording layers 102 and 103 affects the reproduced waveform, and the data is accurately recorded. There was a problem that could not be played.

Further, when the protective film 105 is formed of a UV curing agent by a spin coating method, if there is coating unevenness of the curing agent, the diffracted light is disturbed from the guide groove 113 and the preformat portion formed on the substrate 101. Therefore, there is a problem that the tracking servo to the guide groove and the data reproduction of the preformat section cannot be performed accurately.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an information recording medium having an information recording layer whose optical characteristics greatly change.
An object of the present invention is to provide an information recording medium in which accurate data can be reproduced without being affected by noise due to reflection from the protective film and tracking servo can be accurately performed.

[0019]

In order to achieve the above-mentioned object, the present invention is an information recording medium for recording information by irradiating light, which comprises a light-transmissive substrate and a substrate formed on the substrate. A first information recording layer, a second information recording layer formed on the first information recording layer and having a light absorption rate higher than that of the second information recording medium, and the second information recording layer The information recording medium has a metal film formed thereon and a protective film formed on the metal film, and is irradiated with light from the substrate side.

[0020]

In the present invention, since the metal film is formed on the second information recording layer, the incident light is almost reflected by this metal film, the light is hardly transmitted to the protective film, and the UV curing agent is applied. Since irregularity is not added to the diffracted light from the uneven portion of the substrate due to unevenness, accurate data can be reproduced and tracking servo can be performed accurately.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view of an information recording medium 50 according to an embodiment of the present invention.

This information recording medium 50 is formed on a light-transmissive substrate 1 by Ge, S, which has a small light absorption rate for laser light.
and a first information recording layer 2 formed of a compound of Te, and a compound having a metal such as Bi, Te, Sb or the like or an alloy thereof having a higher light absorption property to the laser light than the information recording layer 2. The second information recording layer 3 is formed, the metal film 4 having a high reflectance of 80% or more is formed on the second information recording layer 3, and the UV curable resin is further formed thereon. After the spin coating, the protective film 5 is formed by irradiating ultraviolet rays to cure the protective film 5.

Here, the first information recording layer 2, the second information recording layer 3 and the high reflectance metal film 4 are sequentially formed by laminating by a sputtering method or a vapor deposition method. The thicknesses of the first information recording layer 2, the second information recording layer 3, the metal film 4 and the protective film 5 are 450 Å and 30 Å, respectively.
0 Å, 400 Å, 5 μm
Is.

When the laser beam 6 is irradiated from the substrate 1 side,
Reflected light 7 reflected at the interface between the substrate 1 and the first information recording layer 2, reflected light 8 reflected at the interface between the first information recording layer 2 and the second information recording layer 3, The reflected light 9 reflected at the interface between the information recording layer 3 and the metal film 4 causes multiple interference with each other, and appears as reproduction light 10 of this recording medium.

The metal film 4 has a high light absorption property, and the laser beam 6 hardly reaches the protective film 5 formed thereon, and even if the metal film 4 reaches the protective film 5, it interferes with the reflected lights 7, 8, and 9. It has no effect.

Therefore, by using this information recording medium, noise due to reflection from the protective film 5 is not added to the reproduced waveform, and accurate data reproduction can be performed.

FIG. 2 shows the reproduction light amount and the waveform of the push-pull signal in this embodiment.

In the present embodiment, as shown in FIG. 4, even if coating unevenness occurs on the protective film 5, there is no light reflected by the protective film 5 as described above, so there is no effect due to coating unevenness, and the amount of reproducing light and Disturbance due to uneven coating does not occur in the push-pull signal.

In the above-mentioned embodiment, the tracking performance by the diffraction interference in the uneven portion of the guide groove is described. However, in the case of the substrate in which the preformat information is preformed in the form of a pit, the uneven portion of the pit is formed. Since the data is read by the modulated reflected light due to the diffraction interference effect in (1), uneven coating of the protective film becomes a problem, and the present invention can be applied to such an information recording medium.

[0031]

As described above in detail, according to the present invention, there is provided an information recording medium in which accurate data reproduction can be performed without the influence of noise due to reflection from the protective film and the tracking servo can be performed accurately. can do.

[Brief description of drawings]

FIG. 1 is a sectional view of an information recording medium according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of a reproduction light amount and a push-pull signal in this embodiment.

FIG. 3 is a sectional view of a conventional information recording medium.

FIG. 4 is a plan view of an information recording medium when coating unevenness occurs on the protective film 105.

FIG. 5 is a waveform diagram of a reproducing light amount and a push-pull signal in a conventional information recording medium.

[Explanation of symbols]

 1 ... substrate 2 ... first information recording layer 3 ... second information recording layer 4 ... metal film 5 ... protective film

Claims (3)

[Claims] 1. An information recording medium for recording information by irradiating light, a light-transmissive substrate, a first information recording layer formed on the substrate, and the first information recording layer. A second information recording layer formed on the second information recording medium and having a higher light absorption rate than the second information recording medium; a metal film formed on the second information recording layer; and a metal film formed on the metal film. An information recording medium having a protective film, which is irradiated with light from the substrate side. 2. The light transmittance of the first information recording layer and the second information recording layer is 5% or more, the light reflectance of the metal film is 80% or more, and the film thickness is Is 4
The information recording medium according to claim 1, wherein the information recording medium has a thickness of 00 Å or more. 3. The first information recording layer comprises Ge, Sb, T
The information recording medium according to claim 1, wherein the second information recording layer is made of a compound having e, the second information recording layer is made of a compound having Bi and Te, and the protective film is made of a UV curing agent applied by a spin coating method. ..