JP4376911B2 - Optical information recording medium and magneto-optical recording medium - Google Patents

Description

  The present invention relates to an optical information recording medium, in particular, an optical information recording medium having at least two recording layers, and an optical information recording medium.

  An optical disk such as a DVD (Digital Versatile Disc) is bonded with two transparent plastic substrates having a thickness of 0.6 mm so that a recording layer made of uneven pits formed on these substrates becomes an adhesive surface. It is produced by doing. There are several types of read-only DVDs, which are so-called double-layer discs in which different information is recorded in advance on the two substrates, and this double-layer disc is played back. In some cases, since reproduction light is incident from one of the disk surfaces, there is an advantage that two different recording layers can be accessed in a short time.

  Hereinafter, a two-layer disc will be described with reference to the drawings.

  The optical information recording medium 107, which is a two-layer disc, has a transparent substrate 102, a first recording layer 103, a transparent resin layer 104, a second recording layer 105, and a transparent or translucent protective material 106 in order from the light incident side. Is formed. The substrate 102 and the protective material 106 are made of, for example, a plastic such as polycarbonate or amorphous polyolefin, an ultraviolet curable acrylic resin, or the like.

  The first recording layer 103 is formed with, for example, a concavo-convex pattern and a guide groove corresponding to information, and includes a dielectric film 109, a recording layer 110, and a translucent film 111. On the other hand, similarly to the first recording layer 103, the second recording layer 105 is formed with a concavo-convex pattern and guide grooves according to information, and is composed of a dielectric film 112, a recording layer 113, and a translucent film 114. . Here, the translucent film 111 is designed to function as a reflective film so that the translucent film 111 partially reflects and transmits the other part.

  Then, the first recording layer 103 and the second recording layer 105 are bonded together by a transparent resin layer 104 having a predetermined thickness. As a result, an integrated optical information recording medium having two recording layers 103 and 105 (that is, two recording layers 110 and 113) is formed. As a result, the first recording layer 103 (recording layer 110) is arranged on the side on which the light 108 enters, and the second recording layer 105 (on the side opposite to the side on which the light 108 enters). The recording layer 113) is arranged.

  Next, a method for reproducing a signal from the optical information recording medium 107 will be described.

  The reproduction of the signal of the first recording layer 103 is performed by condensing the reproduction light 108 incident from the substrate 102 side on the first recording layer 103. On the other hand, the signal of the second recording layer 105 is reproduced by moving the focal position of the objective lens 101 to the second recording layer 105 and condensing the reproduction light 108 on the second recording layer 105.

  Here, in reproducing the signal of the second recording layer 105, the reproduction light 108 needs to pass through the first recording layer 103. Therefore, a so-called translucent film 111 is used for the first recording layer 103. This translucent film 111 is designed to reflect a part of incident light and transmit the other part. Therefore, the reproduction light can reach the second recording layer located at the back when viewed from the light incident side, and the reflected light from the second recording layer can pass through the first information layer again, so that the reproduction of the second recording layer can be performed. Is possible.

  As described above, by using the translucent film 111 designed to reflect a part of the incident light and transmit the other part, the first recording layer and the second recording layer are used. Can be reproduced, but the reproduction signal strength is insufficient for multi-layer recording with a recordable / reproducible recording film (magneto-optical recording film, phase change recording film, etc.) that requires the number of layers or the amount of reflected light for multilayering. There was a problem that occurred.

  Therefore, the present invention has been made for the purpose of solving the above-mentioned problems, and the optical information recording medium of the present invention is composed of a first recording layer, an intermediate layer, and a second recording layer from the light incident side. In the optical information recording medium, the first recording layer is provided with a dielectric laminated film, the second recording layer is composed of a temperature-controlled recording layer, The dielectric layered film is characterized in that the reflectance decreases as the incident angle increases.

  The optical information recording medium of the present invention is an optical information recording medium composed of a first recording layer, an intermediate layer, and a second recording layer from the light incident side. And the second recording layer is composed of a temperature control type recording layer, and the center of the laminated film functions as a reflecting film when focused on the second recording layer, It is a dielectric laminated film that becomes a transparent film around the beam.

  The dielectric laminated film includes a dielectric film A having a refractive index of 1.8 to 2.2, a dielectric film B having a refractive index of 1.3 to 1.6, and a dielectric from the light incident side. It is characterized by comprising at least three layers laminated in the order of the film A.

  The magneto-optical recording medium of the present invention is a magneto-optical recording medium comprising a first recording layer, an intermediate layer, and a second recording layer from the light incident side, wherein the first recording layer From the incident side, a dielectric film A, a magnetic film C as a recording layer, and a laminated film are formed, and the second recording layer is formed from the light incident side, the dielectric film A and a magnetic film C ′ as a reproducing layer. , Dielectric film A, magnetic film C that is a recording layer, dielectric film A, and a magnetic super-resolution layer composed of a heat dissipation layer, and the laminated film has a beam center that is focused on the second recording layer. It is a dielectric laminated film that functions as a reflective film and becomes a transparent film around the beam.

  The dielectric laminated film includes a dielectric film A having a refractive index of 1.8 to 2.2, a dielectric film B having a refractive index of 1.3 to 1.6, and a dielectric from the light incident side. It is characterized by being composed of three or more layers in the order of A.

  According to the present invention, the amount of reflected light from the focused layer can be obtained without impairing, and sufficient reproduction signal intensity can be ensured. Therefore, even if the recording film has two or more layers, it is possible to read the recording information from all the multilayer films while maintaining the signal quality at a certain level or higher.

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

  In the field of optics, by laminating transparent films having different refractive indexes, it is possible to realize a reflection enhancement effect and an antireflection effect, which are used as a polarizing beam splitter and an antireflection coating. A film in which such transparent films are laminated usually has a property that the incident angle of light is limited, and the reflectance is high only within a specific incident angle range.

  As an example, when two dielectric films A and B having a refractive index of 2.0 and 1.5 are laminated with a film thickness of about 1/4 of the wavelength, the reflectance with respect to the incident angle is as follows. Here, the dielectric A has a high refractive index of 1.8 to 2.2 such as SiN or AlN, and the dielectric B has a low refractive index of 1.3 to 1.6 such as SiO 2 or MgF. is there.

  When a laminated film designed to have a high reflectivity with respect to normal incidence is applied to a magneto-optical recording medium, it exhibits characteristics equivalent to those of a metal reflection film with respect to normal incidence light. On the other hand, it functions as a transparent film with high transmittance.

  Therefore, the present invention uses a film in which transparent films having different refractive indexes are laminated as the first recording layer, and uses a magnetic super-resolution medium as the second recording layer. In particular, the second recording layer is masked in the high temperature region. A magnetic super-resolution medium is used.

  Next, a specific example of the optical information recording medium of the present invention will be described with reference to FIG.

  The optical information recording medium includes a substrate 1, a first recording layer 2, an intermediate layer 3, a second recording layer 4, and a protective layer 5 in this order from the light incident side (not shown). Here, the board | substrate 1 uses plastics, such as a polycarbonate, an acryl, an amorphous polyolefin, and the film thickness is 0.1-1.2 mm. The intermediate layer 3 and the protective layer 4 are both made of an ultraviolet curable resin, and their film thicknesses are 30 μm and 10 μm, respectively.

The first recording layer 2 has a dielectric A21 on the light incident side of the magnetic film C22 to be a recording layer and a dielectric A23 / dielectric B24 / dielectric A25 on the opposite side, unlike a conventional translucent film. A membrane was provided. Here, the dielectric A uses AlN or SiN, and the dielectric B uses SiO ₂ . Further, TbFeCo was used as the magnetic body C. However, each of the dielectric A, the dielectric B, and the magnetic substance C is not limited to this material.
Furthermore, although three layers of dielectrics having different refractive indexes are laminated on the side opposite to the light incident here, it is needless to say that the number of layers may be five or more.

  The first recording layer 2 includes a dielectric A21 having a thickness of 25 nm, a magnetic substance C22 having a thickness of 5 nm, a dielectric A23 having a thickness of 50 nm, a dielectric B24 having a thickness of 67 nm, and a dielectric A25 film. Although the thickness is 50 nm, it is not limited to this.

  On the other hand, the second recording layer 4 is provided with a magnetic material C′42 serving as a reproducing layer and a dielectric material A41 via a dielectric A43 on the light incident side of the magnetic material C44 serving as a recording layer, which is opposite to the incidence of light. On the side, a dielectric A45 and a heat dissipation layer D46 were provided to obtain a magnetic super-resolution medium.

  Here, AlN or SiN is used as the dielectric A, TbFeCo is used as the magnetic body C, GdFeCo and GdFe are used as the magnetic body C ′, and an Al alloy or an Ag alloy is used as the heat dissipation layer D. It is not limited.

  In the second recording layer 4, the film thickness of the dielectric A41 is 35 nm, the film thickness of the magnetic substance C′42 is 25 nm, the film thickness of the dielectric A43 is 5 nm, the film thickness of the magnetic substance C44 is 40 nm, and the dielectric A45. The film thickness of the heat dissipation layer D46 is 10 nm, and the film thickness of the heat dissipation layer D46 is 20 nm, but is not limited thereto.

  As shown in FIG. 1, by configuring the first recording layer 2, the reflectance is 0.141 at an incident angle of 0 ° and 0.033 at an incident angle of 40 °.

  Therefore, as shown in FIG. 2, when the light for recording or reproducing information is condensed on the first recording layer 2, the light of the first recording layer 2 becomes a beam waist, and is perpendicularly incident locally. For this reason, the first recording layer behaves as a normal magneto-optical recording medium having a reflective structure.

  On the other hand, when the light beam is condensed on the second recording layer 4, the light beam passes through the first recording layer 2. Since the light beam is condensed, the center of the beam is in a vertically incident state, and therefore the first recording layer 2 (particularly a dielectric laminated film) functions as a reflection film near the beam center. However, the reflectivity of the first recording layer 2, specifically the dielectric A / B / A laminated film, decreases around the beam (the portion where the incident angle increases), and the intensity distribution is close to that of the transparent film. Therefore, a condensed beam profile is formed in the second recording layer in a state where the light intensity around the beam is high, and as shown in the figure, the width at the center of the beam is narrowed and the intensity around the beam is increased.

  By combining such a beam profile with a magnetic super-resolution medium, the signal around the beam is masked by magnetic super-resolution, and only the high light intensity in the center of the beam is involved in signal reproduction. . In this way, the second recording layer 4 can be reproduced, and recording or reproduction is performed with a beam smaller than usual, so that a recording density higher than usual can be achieved.

  Since the magnetic super-resolution medium is well known, a detailed description is omitted here. For this recording layer, the transmissivity varies depending on the temperature. In particular, there is a super-resolution medium of a type different from the magnetic type due to a combination of a reproducing layer and a normal recording medium that increase the transmissivity when the temperature rises. Applicable.

  Further, in such a configuration, the magneto-optical signal may appear large in a Kerr ellipse. Therefore, for reproduction of the magneto-optical signal, a λ / 4 phase plate is added before the analyzer, so that the magneto-optical signal is obtained. Can take.

  In the above, the example in which the second recording layer is configured by a magnetic super-resolution medium has been described. Next, on the basis of FIG. 3, an example in which the second recording layer is configured by a temperature-controlled magneto-optical recording medium. Will be described.

  Two recording layers C2 (53) and C3 (51) are arranged with respect to one reproducing layer C1 (55) via nonmagnetic materials E (52) and (54), and the recording layer C2 has a temperature of The composition of the recording layer C3 is determined so that a magnetic field is generated at a temperature Tb different from that of Ta. Then, when reproducing the second recording layer 4, the information of the two recording layers is selected by two types of laser power Pa at which the temperature of the second recording layer becomes Ta and laser power Pb at which the temperature becomes Tb. Can be played.

  Therefore, by configuring the second recording layer with a temperature-controlled magneto-optical recording medium, information can be reproduced from each recording layer even in an optical information recording medium having three or more recording layers.

  Although the temperature control type magneto-optical recording medium has been described here, it goes without saying that any temperature control type recording medium may be used.

It is a figure which shows the structure of the optical information recording medium of this invention. It is a figure explaining the reproduction principle of the optical information recording medium of this invention. It is a figure which shows the structure of the other optical information recording medium of this invention. It is the side view which showed an example of the conventional optical information recording medium. It is the side view which showed an example of the 1st recording layer of the conventional optical information recording medium. It is the side view which showed an example of the 2nd recording layer of the conventional optical information recording medium.

Explanation of symbols

1 Substrate 2 First recording layer 3 Intermediate layer 4 Second recording layer 5 Protective layer

Claims (5)

An optical information recording medium composed of a first recording layer, an intermediate layer, and a second recording layer from the light incident side,
The first recording layer is provided with a dielectric layer, a recording layer, and a laminated film of dielectrics from the light incident side ,
The second recording layer is composed of a recording layer capable of super-resolution reproduction by temperature ,
The optical information recording medium according to claim 1, wherein the laminated film is a dielectric laminated film whose reflectivity decreases as the incident angle of light increases. An optical information recording medium composed of a first recording layer, an intermediate layer, and a second recording layer from the light incident side,
The first recording layer is provided with a dielectric layer, a recording layer, and a laminated film of dielectrics from the light incident side ,
The second recording layer is composed of a recording layer capable of super-resolution reproduction by temperature ,
The optical information recording medium according to claim 1, wherein the laminated film is a dielectric laminated film in which a beam center functions as a reflective film when focused on the second recording layer and becomes a transparent film around the beam.   The dielectric laminated film includes a dielectric film A having a refractive index of 1.8 to 2.2, a dielectric film B having a refractive index of 1.3 to 1.6, and a dielectric film A from the light incident side. The optical information recording medium according to claim 1, wherein the optical information recording medium is composed of at least three layers stacked in this order. A magneto-optical recording medium composed of a first recording layer, an intermediate layer, and a second recording layer from the light incident side,
The first recording layer is composed of a dielectric film A, a magnetic film C as a recording layer, and a laminated film from the light incident side.
The second recording layer includes, from the light incident side, a dielectric film A, a magnetic film C ′ as a reproducing layer, a dielectric film A, a magnetic film C as a recording layer, a dielectric film A, and a heat dissipation layer. A magnetic super-resolution layer consisting of
The magneto-optical recording medium according to claim 1, wherein the laminated film is a dielectric laminated film in which the beam center functions as a reflective film when focused on the second recording layer and becomes a transparent film around the beam.   The dielectric laminated film includes, from the light incident side, a dielectric film A having a refractive index of 1.8 to 2.2, a dielectric film B having a refractive index of 1.3 to 1.6, and a dielectric A The magneto-optical recording medium according to claim 4, wherein three or more layers are laminated in order.

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