JPH06162570A - Optical information recording medium disk and its production - Google Patents

Abstract

PURPOSE:To provide an optical disk which enables high-density recording by reducing an effective spot diameter. CONSTITUTION:The optical disk 1 consists of a substrate 2 formed by extrusion molding of polycarbonate resin, and preliminarily modified signals are transferred as pits thereon. Then, a layer 4 to change transmittance is formed to have uniform thickness on the substrate having transferred pits 3, and further, a reflecting film 5 and a protective film 6 are formed thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium disk, and more particularly to an optical information recording medium disk capable of recording and reproducing high density information and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, an optical information recording medium disk (hereinafter referred to as
It is called an optical disc. ), Various studies have been conducted to achieve higher density recording. Generally, a laser is used for reading and writing information on and reading information from an optical disk. The light beam spot diameter of the laser is determined as a spatial frequency by the light source wavelength of the optical disk and the numerical aperture (NA) of the objective lens. Therefore, since the recording density is also determined by this spatial frequency, many attempts have been made to increase the recording density by reducing the beam spot diameter, and, for example, JP-A-2-969.
Japanese Patent Laid-Open No. 26-26 describes that a material layer capable of reducing the beam spot diameter is provided.

Further, as a means for forming a thin film on a substrate, a vacuum vapor deposition method, a dipping method, a spray method, a spin coating method and the like are known.

[0004]

However, in the technique disclosed in Japanese Unexamined Patent Publication No. 2-96926, the purpose is to determine how the material layer is provided for the pit row on the substrate or the guide groove for tracking. There is no mention of whether it can be reached, nor is there any mention of manufacturing methods.

Further, in the thin film forming means, the spin coating method is very advantageous in consideration of the running cost or productivity of the apparatus, but the coating material in a solution state is dropped on the disk surface and rotated. In this method of uniformly applying by centrifugal force, it is very difficult to make the film thickness of the concave portion and the convex portion equal when the unevenness such as the pit row or the guide groove is formed on the substrate. That is, there is a drawback that the film thickness at the bottom of the pit row or the guide groove, which is the concave portion, is larger than the film thickness at the substrate flat surface portion (hereinafter, referred to as the land portion), which is the convex portion.

If the thickness of the uneven portion, that is, the thickness of the light absorption layer containing a substance that reduces the beam spot diameter of the irradiated light is uneven as described above, the beam is not properly positioned on the board. It becomes difficult to focus the spot.

The present invention has been made in view of the above problems of the prior art, and its object is to improve the information recording and reading ability by effectively reducing the beam spot diameter. Then, as a result, it is to provide an optical disc capable of achieving a high recording density.

[0008]

In order to solve the above-mentioned problems, the first invention is an optical information system in which a reflective layer made of a light-reflecting substance is provided on a light-transmissive substrate having minute pit rows. In a recording medium disc, a light absorption layer containing a substance that reduces the diameter of an irradiated light beam spot between the substrate and the reflection layer, and having a constant film thickness including the bottom of the pit row. Is provided.

According to a second aspect of the invention, a recording layer for recording information and a reflective layer made of a light reflective material are provided in this order on a light transmissive substrate provided with a guide groove for tracking. In the optical information recording medium disc, between the substrate and the recording layer, a light absorbing layer containing a substance that reduces the diameter of the spot of the irradiated light beam, the film thickness including the bottom of the guide groove. Something that is constant is provided.

It is also preferable that a transparent organic material layer for improving the reflectance is provided between the substrate of the first and second inventions and the light absorbing layer.

In the method of the third invention, a light absorbing layer containing a substance for reducing the diameter of an irradiated light beam spot is formed on a light transmissive substrate having minute pit rows for information recording. A vacuum evaporation method is used to form a uniform film thickness including the bottom of the pit row, and a reflective layer made of a light reflective material is further provided thereon.

The method of the fourth aspect of the present invention is a vacuum evaporation method in which a light absorbing layer containing a substance for reducing the diameter of an irradiated light beam spot is formed on a light transmitting substrate having guide grooves for tracking formed therein. Is formed so as to have a constant film thickness including the bottom of the guide groove, and a recording layer for recording information and a reflective layer made of a light-reflecting substance are further provided thereon in this order.

It is also preferable to provide a transparent organic material layer for improving the reflectance between the substrates of the third and fourth inventions and the light absorbing layer by spin coating.

[0014]

The optical disk of the present invention is provided with a light absorption layer capable of reducing the effective spot diameter so that the film thickness becomes uniform. Therefore, the beam spot can be focused at an optimum position for detecting the pit row or the tracking guide groove.

A uniform film thickness can be easily obtained by using a vacuum deposition method as a means for forming the light absorption layer.

Further, when a transparent organic material layer is provided between the light absorption layer and the substrate, the reflectance of the optical disk can be improved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a partial sectional view showing an example of a read-only type optical disk according to the first invention. In this optical disc 1, a pre-modulated signal is transferred as pits 3 on a substrate 2 formed by injection molding of a polycarbonate resin or the like. Then, on the substrate 2 onto which the pits 3 have been transferred, the light absorption layer 4 according to the present invention is formed with a uniform thickness, and the reflection film 5 and the protection film 6 are further provided thereon.

The light absorption layer 4 according to the present invention contains a substance capable of making the effective spot diameter smaller than the beam spot diameter irradiated with light. As such a substance, a saturable absorptive substance, a substance having a nonlinear optical effect,
Alternatively, there is a phase change material or the like.

When the saturable absorptive substance is used, the effective spot diameter can be reduced because the transmittance of only a portion having a large light intensity in the light intensity distribution of the irradiated beam spot increases. Therefore, high density information can be read and written. Further, in the case of a nonlinear optical substance, when the transmittance, that is, the light absorptance changes in proportion to the cube of the light intensity, the same effect as that of the saturable absorptive substance or the like can be expected. Further, when the refractive index of the substance changes in proportion to the cube of the light intensity, the beam self-focuses and the spot diameter can be similarly reduced. Further, with respect to the phase change substance, a similar effect can be obtained by utilizing the fact that a crystalline or amorphous phase change occurs depending on the irradiation light intensity and the light absorption rate changes.

FIG. 2 is a partial cross-sectional view showing another example of the read-only optical disk according to the first invention, in which a transparent organic material layer 7 for improving the reflectance is further provided between the substrate 2 and the light absorption layer 4. Has been formed.

An example of manufacturing the optical disk 1 will be described based on the third invention. The pit 3 has, for example, a track pitch of 0.
It is transferred onto the substrate 2 with a thickness of 95 μm. Then, for example, a phthalocyanine compound which is a saturable absorber for forming the light absorption layer 4 is used, and the bottom portion of the pit 3 and the land portion have a uniform film thickness by vacuum deposition while rotating the substrate. A thin film is formed so that (the light absorption layer 4 of the optical disc 1 manufactured based on this manufacturing example
As a result of cross-sectional observation by SEM, the pits 3 and the land had uniform film thickness. ). This light absorption layer 4
Further, for example, aluminum is vapor-deposited to form a reflective film 5, and a protective film 6 made of, for example, an ultraviolet curable resin is further formed on the reflective film 5.
Cover with.

When the optical disk 1 manufactured based on the above manufacturing example was reproduced by a CD pickup having a wavelength of 780 nm and NA = 0.5, the crosstalk was about 45%. On the other hand, when an optical disc manufactured in exactly the same manner as in the above-described manufacturing example except that the light absorption layer 4 was not included was reproduced under the same conditions, the crosstalk was 55% to 60%.

A manufacturing example of the optical disc 1 having the transparent organic material layer 7 will be described based on the third invention as well. The pits 3 are transferred onto the substrate 2 with a track pitch of 0.95 μm, for example. Then, a transparent organic material layer 7 is formed thereon by a spin coater at a rotation speed of 1000 rpm, for example, and dried. Examples of the composition forming the transparent organic material layer 7 include a petroleum resin (Quinton; Nippon Zeon Co., Ltd.) dissolved in a hydrocarbon solvent such as n-hexane at 0.5% by weight.

The method of forming the light absorption layer 4, the reflection film 5 and the protective film 6 laminated on the transparent organic material layer 7 is as follows.
This is exactly the same as the above-described manufacturing example in which no is formed. When the optical disc 1 manufactured in this manner was reproduced by a CD pickup similar to the above, crosstalk was about 45%.
Met.

On the other hand, FIG. 3 is a partial sectional view showing an example of a rewritable optical disk according to the second invention. In this optical disk 8, a guide groove 10 is provided in advance in a spiral shape on a substrate 9 formed by injection molding of a polycarbonate resin or the like. And the substrate 9 provided with this guide groove 10
A light absorption layer 11 according to the present invention is formed on the above with a uniform thickness, and a recording layer 12 for recording information is further formed thereon.
A reflective film 13 and a protective film 14 are provided.

FIG. 4 is a partial cross-sectional view showing another example of the write-once read-many optical disk according to the second invention as well. A transparent organic material layer 15 for improving the reflectance is provided between the substrate 9 and the light absorption layer 11. Further formed.

Explaining an example of manufacturing the above-mentioned optical disk 8 based on the fourth invention, the guide groove 10 has a groove width of 0.4 μm, for example.
It is formed on the substrate 9 by m. Then, for example, erythrosine, which is a saturable absorptive substance, for forming the light absorption layer 11 is vacuum-deposited (the light absorption layer 11 of the optical disc 8 manufactured based on this manufacturing example is subjected to cross-sectional observation by SEM). As a result, both the guide groove 10 portion and the land portion had a uniform film thickness). Further on the light absorption layer 11,
For example, a cyanine dye, which is one of organic dyes, is dissolved in an isopropanol solvent and spin-coated to form the recording layer 12. Further, a reflective film 13 formed by sputtering gold, for example, and a protective film 14 made of an ultraviolet curable resin are coated in this order.

When a CD signal was recorded at 6 mW by a pickup having a wavelength of 780 nm and NA = 0.5 on the optical disk 8 manufactured based on the above-described manufacturing example, the crosstalk during reproduction was 44%, and the reproduced waveform There was almost no disturbance. On the other hand, when recording / reproducing was performed on an optical disc manufactured in exactly the same manner as in the above-described manufacturing example except that the light absorption layer 11 was not included, the crosstalk during reproduction was 67%, and the reproduced waveform was also extremely disturbed. Was there.

A manufacturing example of the optical disk 8 having the transparent organic material layer 15 according to the fourth invention will be described. The guide groove 10 is formed on the substrate 9 with a groove width of 0.4 μm, for example. Then, a transparent organic material layer 15 is formed thereon by a spin coater at a rotation speed of 1000 rpm, for example, and dried. As a composition for forming the transparent organic material layer 15,
For example, a polyurethane resin can be used.

The method of forming the light absorption layer 11, the recording layer 12, the reflective film 13 and the protective film 14 laminated on the transparent organic material layer 15 is exactly the same as the above-mentioned manufacturing example in which the transparent organic material layer 15 is not formed. When the optical disc 8 manufactured in this manner was reproduced by the same CD pickup as described above,
The crosstalk was 44%, and there was almost no disturbance in the reproduced waveform. On the other hand, when recording and reproducing were performed on the optical disk 7 manufactured in exactly the same manner as in the above-described manufacturing example except that the light absorption layer 11 was not included, crosstalk during reproduction was 67%.
The reproduced waveform was also very disturbed.

[0031]

As described above, since the optical information recording medium disk of the present invention has the light absorbing layer having a uniform thickness,
It is possible to focus the beam spot on the proper position. Therefore, the effective spot diameter can be reduced, and recording can be performed at a higher density than the so-called spatial frequency limited by the light wavelength and the numerical aperture of the objective lens. Further, if the light absorption layer is formed by a vacuum deposition method, the optical information recording medium disk having the uniform film thickness can be easily manufactured.

Furthermore, when a transparent organic material layer is provided between the light absorbing layer and the substrate, it is possible to improve the reflectance of the optical information recording medium disc with respect to the wavelength used.
Tracking becomes easy.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an example of a read-only optical disc according to the present invention.

FIG. 2 is a partial cross-sectional view showing another example of the read-only optical disc.

FIG. 3 is a partial cross-sectional view showing an example of the rewritable optical disk of the same.

FIG. 4 is a partial sectional view showing another example of the rewritable optical disc.

[Explanation of symbols]

1, 8 ... Optical information recording medium disk, 2, 9 ... Substrate, 3 ...
Pit, 4, 11 ... Light absorbing layer, 5, 13 ... Reflective film, 6,
14 ... Protective film, 10 ... Guide groove, 12 ... Recording layer, 7, 15
… Transparent organic material layer.

Claims (6)

[Claims] 1. An optical information recording medium disk comprising a light-transmissive substrate on which information is recorded by minute pit rows and a reflective layer made of a light-reflective substance, the substrate and the reflective layer. And a light absorption layer containing a substance that reduces the diameter of the irradiated light beam spot is formed between the two, and the light absorption layer has a constant film thickness including the bottom of the pit row. Optical information recording medium disk. 2. An optical information recording in which a recording layer for recording information and a reflective layer made of a light-reflecting substance are provided in this order on a light-transmissive substrate provided with a guide groove for tracking. In the medium disc, a light absorbing layer containing a substance that reduces the diameter of the irradiated light beam spot is formed between the substrate and the recording layer, and the light absorbing layer includes the bottom of the guide groove. An optical information recording medium disk having a uniform film thickness. 3. The optical information recording medium disk according to claim 1, further comprising a transparent organic material layer formed between the substrate and the light absorption layer for improving reflectance. . 4. A light-absorbing layer containing a substance for reducing the diameter of a light beam spot to be irradiated is formed on a light-transmissive substrate having minute pit rows for recording information by using a vacuum deposition method. A method for manufacturing an optical information recording medium disk, which is characterized in that the pit row is formed to have a constant film thickness including the bottom thereof, and a reflective layer made of a light reflective material is further provided thereon. 5. A light absorbing layer containing a substance that reduces the diameter of an irradiated light beam spot is formed on a light transmissive substrate having a guide groove for tracking formed by a vacuum deposition method.
The guide groove is formed so as to have a constant film thickness including the bottom portion, and a recording layer for recording information and a reflective layer made of a light-reflecting substance are further provided in this order on the formed film. Optical information recording medium disk manufacturing method. 6. The optical information according to claim 4, wherein a transparent organic material layer for improving reflectance is formed between the substrate and the light absorption layer by a spin coating method. Recording medium disc manufacturing method.