JPH0883443A - Production of optical information recording medium - Google Patents

Abstract

PURPOSE: To shorten initialization time, to reduce the power of laser beam and to prolong the usable time of laser by irradiating a recording layer with laser beam at the time of curing a protective layer when a phase change type medium is initialized. CONSTITUTION: The figure is a block diagram of a device for curing the UV- curing resin of a phase change type recording medium and initializing the medium. This device has a light source 8 for curing a UV-curing resin, a mechanism 9 for turning a substrate 1, a multilayered film 10 including a recording layer, a layer of an uncured UV-curing resin 11 formed by spin coating and a laser beam source 12 for initialization. At the time of curing the uncured UV-curing resin 11 forming a protective layer, laser beam from the light source 12 is converged and the recording layer in the multilayered film 10 is initialized by irradiation with the converged laser beam. The time required to initialize the recording layer is shortened, the power of laser beam is reduced and the usable time of laser is prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical information recording medium, which is capable of high speed, high density and overwriting by utilizing reversible phase change of a recording layer upon irradiation with laser light. The present invention relates to a method for manufacturing an optical information recording medium.

[0002]

2. Description of the Related Art In recent years, a recording medium capable of recording and reproducing a large amount of data at high density and at high speed has been demanded as the amount of information has increased. Optical discs are expected to meet such applications. There is. Optical disks are classified into a write-once type that allows recording only once and a rewritable type that allows recording / erasing as many times as desired.

Examples of the rewritable optical disk include a magneto-optical recording medium which utilizes the magneto-optical effect and a phase change medium which utilizes the reflectance change accompanying the reversible change of the crystalline state. The phase change medium does not require an external magnetic field, and recording / erasing can be performed only by modulating the power of the laser light, and it has an advantage that the recording / reproducing apparatus can be downsized. Furthermore, so-called 1-beam overwriting is possible, in which erasing and re-recording are performed simultaneously with a single laser light beam.

Alternatively, there is an advantage that a recording-erasable medium having a wavelength of around 800 nm, which is the mainstream at present, can be used as a high-density recording medium with a short wavelength without changing the material. A chalcogen-based alloy thin film is often used as the recording layer material of such a phase change medium capable of one-beam overwriting. For example, G
Examples thereof include eTeSb type, InSbTe type and GeSnTe type.

In practical use of such a phase change medium, the recording layer is often sandwiched between dielectric layers, and a metal reflective layer is further provided on the recording layer. With this multilayer structure, it is usual to improve the difference in reflectance (contrast) by utilizing the interference effect. Furthermore, this multi-layer structure also has the effect of preventing heat dissipation, heat storage hardening, and mechanical deformation of the recording layer.

That is, generally, in a rewritable phase change recording medium, an unrecorded / erased state is set to a crystalline state to form an amorphous bit. The amorphous bit is formed by heating the recording layer to a temperature higher than the melting point and quenching it. The dielectric layer sandwiching the recording layer functions as a heat dissipation layer for obtaining a sufficient supercooled state.

On the other hand, erasing (crystallization) is performed by heating the recording layer to a temperature higher than the crystallization temperature of the recording layer and lower than the melting point. In this case, the dielectric layer functions as a heat storage layer that keeps the temperature of the recording layer at a high temperature until crystallization is completed. On the other hand, the protective layer made of the dielectric layer is important in order to prevent deformation of the recording layer due to melting and volume expansion, thermal damage to the plastic substrate, and deterioration of the recording layer due to moisture. .

Further, in a practical phase-change medium, a light or thermosetting resin layer is provided through the dielectric protective layer or the metal reflective layer on the recording layer to provide functions such as deformation prevention and scratch prevention. It improves the reliability of the product.

[0009]

The phase-change type medium having a multi-layered structure is usually manufactured by the following steps 1 to 6. 1) Injection molding of a plastic substrate or forming a groove on a glass substrate using a photocurable or thermosetting resin.

2) A multilayer thin film layer is successively formed on the substrate in a vacuum chamber. For example, the lower dielectric layer, the recording layer, the upper dielectric layer, and the metal reflective layer are formed in this order.
For the film formation, a vapor deposition method or a sputtering method is usually used. 3) A photocurable or thermosetting resin layer is formed as a protective layer on the recording layer side surface of the substrate of the medium taken out from the vacuum chamber and, if necessary, on the opposite surface.

4) In a phase change medium using a GeSbTe recording layer which is widely used at present for initialization, the crystalline state is usually set to the initial / unrecorded state. Since it is amorphous, it needs to be initialized (crystallized). It is possible at any timing after the film formation in the vacuum chamber. 5) For double-sided media, stick together.

6) Perform a final inspection. Around this, it is packed in a cartridge. The manufacturing process of the phase change medium is almost the same as that of the magneto-optical medium. However, the time required for initialization is longer than that of the magneto-optical medium, which is a bottleneck in improving mass productivity. Since the initialization of a normal magneto-optical disk is completed only by passing the medium after film formation in the magnetic field of a large magnet, the required time is only 5 to 6 seconds or less.

For a phase change medium, the most practical currently known initialization method is to irradiate a laser beam to heat the recording layer. According to the study of the present inventors, for example, when a commercially available bulk eraser (Shiba Soku Co., Ltd., LK10 series) is used, it is 130 mm.
It takes about 30 to 40 seconds to initialize one side of the diameter disc.

Although a method using flash lamp annealing in combination has been proposed, at present, it has not been shortened more than the initialization of the magneto-optical disk.

[0015]

As a result of various studies on the initialization method of the phase change medium, the present inventors have found that it is difficult to significantly reduce the initialization time under the present circumstances. Rather, by combining the initialization step with other steps in the above steps, not only the time can be shortened, but also the required laser light power can be reduced and the usable time of the laser can be extended. I found it.

That is, the gist of the present invention is to provide at least a phase-change recording layer on a substrate and one or both of a dielectric protective layer and a metal reflective layer on the opposite side of the recording layer from the substrate, In producing an optical information recording medium having a protective layer made of a photocurable or thermosetting resin, the recording layer is irradiated with a laser beam when the photocurable or thermosetting resin of the protective layer is cured. Then, the method for manufacturing an optical information recording medium is characterized in that the recording layer is initialized.

Next, the structure of the optical recording medium according to the present invention will be described. FIG. 1 is a schematic cross-sectional view showing the layer structure of a phase change type optical information recording medium according to the present invention. In FIG. 1, a transparent resin such as polycarbonate, acrylic resin, amorphous polyolefin, or glass can be used for the substrate 1.

The thickness of each of the protective layers 2 and 4 is preferably in the range of 100Å to 5000Å. Protective layers 2, 4
If the thickness is less than 100Å, the effect of preventing the deformation of the substrate and the recording film is insufficient, and it does not serve as a protective layer. When the thickness of the protective layers 2 and 4 is 5000 Å or more, the internal stress of the protective layer itself and the difference in elastic characteristics from the substrate become remarkable, and cracks easily occur.

As the protective layers 2 and 4, materials such as metal oxides, nitrides and fluorides having a melting point of 1000 ° C. or higher are desirable. Alternatively, one of the compounds is a dielectric or semiconductor containing a chalcogen element such as ZnS, ZnO, CdS, and a metal oxide, nitride or carbide of Si, Ta, Y, Zr, Ti or the like, or MgF ₂ or the like. A material in which a fluoride is mixed as the other compound is preferably used.

For example, when ZnS is mixed with other oxides, nitrides, carbides or fluorides, the composition ratio of ZnS is usually 90 to 40 mol%.
The phase-change recording layer 3 usually has a thickness of 100Å to 1
Selected in the range of 000Å. The thickness of the recording layer 3 is 100Å
If it is thinner, sufficient contrast cannot be obtained. Further, the crystallization speed tends to be slow, and it becomes difficult to erase the record in a short time.

On the other hand, if the thickness of the recording layer 3 exceeds 1000Å, it becomes difficult to obtain optical contrast, and
It is not preferable because cracks easily occur. It should be noted that the thicknesses of the recording layer 3 and the protective layers 2 and 4 are high in absorption efficiency of laser light in consideration of the interference effect due to the multi-layer structure, and the amplitude of the recording signal, that is, the contrast between the recorded state and the unrecorded state is increased. To be chosen.

As the recording layer, GeSbTe or InSb is used.
A ternary compound such as Te is selected as the overwritable material. 0.1 to 10 atomic% of Sn, In, Pb, As, Se, Si, Bi, A is added to these ternary compounds.
It is also effective to add one or more elements from among u, Ti, Cu, Ag, Pt, Pd, Co, Ni and the like to improve the crystal acceleration, optical constants and oxidation resistance.

In the example shown in FIG. 1, a protective coating layer 5 made of light or thermosetting resin for preventing thermal deformation is provided on the protective layer 4, but an adhesive layer is further provided to provide a protective substrate or It may be attached to another recording medium. Further, FIG. 2 shows an example in which the optical reflection layer 6 and the protective coat layer 7 are provided on the protective layer 4.

The optical reflection layer is made of Al, A having a high reflectance.
A metal thin film such as u, Ag, or Ni is used. In this case, the thicknesses of the recording layer and the protective layer are determined in consideration of the interference effect including the reflective layer. The reflective layer 6 also has an effect of promoting diffusion of the thermal energy absorbed by the recording layer 3.

The recording layer 3, the protective layers 2 and 4, and the reflective layer 6 are formed by a sputtering method or the like. Target for recording film,
It is desirable to form a film with an in-line apparatus in which the target for the protective film and, if necessary, the target for the reflective layer material are installed in the same vacuum chamber in order to prevent oxidation and contamination between the layers. It is also excellent in terms of productivity.

In the present invention, the protective coat layers 5 and 7 are formed after forming the above-mentioned multilayer thin film. For the protective coat layers 5 and 7, first, a solvent containing a monomer or an oligomer is applied by spin coating, and this is cured by light or heat. Ultraviolet light is usually used for photocuring. Even in the case of photo-curing, it is general that heat is generated and heated by light irradiation.

When the substrate is made of plastic, the temperature of the substrate must be sufficiently lower than the glass transition point of the substrate (usually less than 200 ° C.), so of course during heat curing,
Even during photo-curing, sufficient energy cannot be applied to complete the curing in a short time. Further, the rapid temperature change causes cracks and the like due to the difference in coefficient of thermal expansion between the layers of the substrate and the recording medium.

Due to these restrictions, it is not uncommon for the curing reaction to take 30 seconds or longer. On the other hand, since the crystallization temperature of the recording layer is usually 150 to 250 ° C., in the present invention, the recording layer is irradiated with the laser light beam during the curing reaction of the protective coat layer 5. As an example, FIG. 3 shows a conceptual diagram of the ultraviolet curing resin curing / initializing device. Reference numeral 8 denotes a light source for ultraviolet curing, and a halogen lamp, a mercury lamp or the like is used.

Reference numeral 9 is a substrate rotating mechanism. Reference numeral 10 is a multilayer film including a recording layer, and 11 is a spin-coated uncured ultraviolet curable resin. As the initialization laser light source 12, a high output semiconductor laser, an Ar laser, or the like is used. The laser light beam is condensed, and a spot having a diameter of several tens to several hundreds of μm is irradiated on the recording layer of 10.

The recording layer is heated (above the glass transition point) by laser irradiation to be initialized (crystallized). The substrate rotates at several hundred to several thousand rpm, and the laser light beam moves to the inner and outer circumferences of the substrate so that the entire surface of the substrate can be sequentially heated. Such a laser light irradiation mechanism can be realized by using a mechanism almost equivalent to a normal optical disk drive.

In a normal drive, the beam spot diameter is focused to about 1 μm, but the initialization is different only in that a wider beam spot diameter is used. In this way, using the focused light beam to locally heat is
After all, while preventing the deformation of the substrate and the crack of the multilayer film,
This is because the recording layer is heated from 200 ° C. to a high temperature of several hundreds of ° C. in a short time. Belt conveyor 14 for the entire initialization device 13
The mechanism for carrying by is illustrated.

The present invention is not intended to simply reduce the process time by combining the two processes and the apparatus. Essential improvements in the initialization process as described below can also be achieved. First, the recording layer is heated uniformly and widely below the glass transition point of the substrate due to the heat generated during curing as described above.

Conventionally, this heating was an additional rather negative effect when a photocurable resin was used.
The present invention positively utilizes this heat generation. By heating during curing, the power required for heating with laser light is reduced. When the recording layer is heated to 300 to 400 ° C. and crystallized, a power reduction of at least 20 to 30% is possible.

The laser light for initialization is tens to hundreds of mW.
Since the laser oscillates like a direct current, the life of the laser is significantly shortened. Therefore, reduction of the DC oscillation power immediately leads to prolongation of the laser life. Further, the crystallization of the recording layer is usually divided into two stages, that is, the generation of crystal nuclei and the growth of crystal grains centering on the nuclei.

The average heat generated during the curing process promotes the formation of crystal nuclei. When the local and instantaneous heating by the laser light is overlapped, the crystal growth centered on the crystal nucleus is instantaneously completed (within about 1 μsec). The density of crystal nuclei can be controlled by controlling the temperature of the recording layer at the time of curing, but this leads to control of the final average crystal grain size.

That is, if the crystal nucleus density is high, the growth of crystal grains centering on each crystal nucleus is suppressed and the average crystal grain size can be reduced. On the other hand, if the crystal nucleus density is low, the average crystal grain size can be increased. The average crystal grain size is necessary in order to keep the erasing ratio at the time of repetitive overwriting constant and to suppress the increase of noise.

The optimum average crystal grain size is not necessarily constant because it depends on the recording layer composition, layer structure and recording conditions (mark length, linear velocity, etc.). Although it is difficult to control the particle size only by the laser light irradiation condition at the time of initialization, it becomes easy by controlling a new parameter such as the temperature at the time of curing.

[0038]

EXAMPLES Examples will be shown below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 ZnS (80 mol%)-SiO ₂ (20 mol%) was applied to a polycarbonate resin substrate having a diameter of 130 mm and a thickness of 2 mm.
The layer is 1000Å, the phase change recording layer of Ge ₂₀ Sb ₂₃ Te ₅₇ (mol%) is 200Å, ZnS (80 mol%)-S.
An io ₂ (20 mol%) layer is 200 Å, Al-Ta (1
%) Form an alloy reflection layer of 1000Å, apply UV curable resin on it, and use a commercially available initialization device (Shibasoku, L
K101) while irradiating the phase change medium with ultraviolet light,
When initialization was performed, effects such as shortening of initialization time, reduction of laser light power, and change of crystal grain size were observed. The temperature of the recording medium at the time of initialization was about 100 ° C.

[0039]

By using the initialization method according to the present invention, it is possible to greatly reduce the time required for the process and to provide a new control method for controlling the crystal grain size during initialization.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a layer structure of a medium according to the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of a medium according to the present invention.

FIG. 3 is a conceptual diagram of an ultraviolet curing resin curing / initializing device.

[Explanation of symbols]

 1 Substrate 2 Protective layer 3 Recording layer 4 Protective layer 5 Protective coat layer 6 Reflective layer 7 Protective coat layer 8 Light source for UV curing 9 Substrate rotation mechanism 10 Multilayer film including recording layer 11 Uncured UV curable resin 12 Initial Laser light source

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironori Mizuno Sanryo Kasei Co., Ltd. Research Institute, 1000, Kamoshida-cho, Midori-ku, Yokohama

Claims (1)

[Claims] 1. A phase-change recording layer on a substrate, and a photo-curable or heat-curable layer on the opposite side of the recording layer from the substrate via one or both of a dielectric protective layer and a metal reflective layer. In producing an optical information recording medium provided with a protective layer made of a resin, the recording layer is irradiated with a laser beam when the photocurable or thermosetting resin of the protective layer is cured. A method for manufacturing an optical information recording medium, characterized by performing initialization.