JP2001084653A - Manufacture of optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for manufacturing an optical information recording disk which has a small tilt and is flat even when the medium is a one-sided recording and reproduction type or both-sided recording and reproduction type constituted by stacking together two substrates having recording thin-film layers of about 0.6 mm. SOLUTION: This method for manufacturing optical information recording medium has a stage for forming a 1st substrate 11 and a 2nd substrate 12, a stage for filming at least one main surface of the 1st substrate 11 to obtain a recording layer 13 where information can be recorded by at least irradiation with a laser beam, etc., and a stage for sticking the 1st and 2nd substrates together facing each other. During the stage of pasting the substrates 11 and 12, at least the substrate 11 on which the recording layer 13 is formed is heated or cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a recordable optical information recording medium obtained by bonding two substrates.

[0002]

2. Description of the Related Art Techniques for reproducing or recording high-density information using a laser beam are known, and are mainly put to practical use as optical disks. The optical disk is a read-only type,
It can be broadly divided into write-once type and rewritable type. The reproduction-only type is commercialized as a compact disk recording music information or a laser disk recording image information, and the write-once type is commercialized as a document file or a static file.
At present, research and development are being conducted mainly on rewritable types, and are being commercialized as data files for personal computers.

[0003] The optical disk has a thickness of 1.2 mm.
In general, an information layer is provided on one main surface of a transparent resin substrate, and a protective layer such as an overcoat is provided thereon, or the same protective plate as the substrate is bonded with an adhesive.

In recent years, studies have been made to use an objective lens having a short laser wavelength and a large numerical aperture (NA) for the purpose of increasing the density of an optical disk. However, shortening the wavelength and increasing the NA decrease the allowable value of the tilt angle (tilt) of the disk with respect to the direction in which the laser beam is input. In order to increase the allowable value of tilt, it is effective to reduce the thickness of the substrate.
For example, a digital video disk (DVD) has a substrate thickness of 0.6 mm. Since the resin substrate having a thickness of 0.6 mm is a single plate having low mechanical strength, the resin substrate has a structure in which two substrates are bonded with the information recording surface inside.

[0005] As a laminating method, a method of applying an ultraviolet UV resin on a substrate, closely irradiating another substrate with UV irradiation, and curing, a method of applying a hot melt resin on the laminating surface side and then closely bonding, A method of bonding with a sheet (double-sided tape), U mainly composed of a cationic polymerization resin
There is a slow-acting UV method in which a V resin is applied to the bonding surface side with a thickness of, for example, 20 μm by screen printing or the like, irradiated with ultraviolet rays to develop adhesiveness, adhered, and cured until curing was completed. .

[0006]

However, when a thin substrate having a thickness of 0.6 mm is used, if the thin film layer is formed so as to obtain a rewritable recording medium, the warpage of the substrate is large, and the substrate varies. Turns out there are cases. This is a problem that was not observed when a substrate having a thickness of 1.2 mm was used, and was not observed when only a metal reflective layer (such as Al or Au) was formed as in a read-only type. Is a challenge.

The cause is that stress remains inside the substrate in the process of cooling the substrate after molding, but the substrate is warped because it is thin. Further, in the cooling process of the substrate after the molding, the substrate is thin due to a change in the temperature of the substrate, so that the substrate is warped. In the rewritable type, a recording film and a dielectric layer for further protecting the recording film are formed. However, it is considered that a large internal stress is generated by the formation of the dielectric layer, so that a substrate having low mechanical strength is warped. It is also considered that the substrate is warped because the substrate is thin due to a temperature change of the substrate in a cooling process after the formation of the dielectric layer.

When an optical disk is manufactured by bonding using such a substrate having a large warp, the optical disk also has a large warp (tilt), and as a result, is not practical.

The present invention has been made to solve the above-mentioned problems of the conventional optical disk, and is applicable to a single-sided recording / reproducing type and a double-sided recording / reproducing type in which two substrates having a recording thin film layer of about 0.6 mm are bonded together. It is an object of the present invention to provide a method for manufacturing a flat optical information recording medium having a small tilt.

[0010]

According to the present invention, information can be recorded by forming a first substrate and a second substrate and irradiating at least one main surface of the first substrate with a laser beam or the like. A method for manufacturing an optical information recording medium, comprising: a step of forming a recording layer; and a step of bonding the first substrate and the second substrate so as to face each other, wherein the first substrate and the second The above object is achieved by a method for manufacturing an optical information recording medium, characterized in that a substrate on which at least a recording layer is formed among two substrates is bonded in a heated state.

As a second means, a first substrate and a second substrate
Forming a recording layer on which information can be recorded by irradiating at least a laser beam or the like on at least one main surface of the first substrate; and forming the first substrate and the second substrate. A method for manufacturing an optical information recording medium, comprising: a step of bonding substrates while facing each other.
The above object is attained by a method for manufacturing an optical information recording medium, wherein a substrate on which at least a recording layer is formed of the second substrate and the second substrate is bonded in a cooled state.

As a third means, a first substrate and a second substrate
Forming a recording layer on which information can be recorded by irradiating at least a laser beam on at least one main surface of the first substrate; and forming at least a recording layer on the first substrate. A method of manufacturing an optical information recording medium, comprising the steps of: providing an overcoat on a substrate; and bonding the first substrate and the second substrate so as to face each other. The above object is achieved by a method for manufacturing an optical information recording medium, characterized in that a substrate on which at least a recording layer is formed is bonded in a heated state.

As fourth means, a first substrate and a second substrate
Forming a recording layer on which information can be recorded by irradiating at least a laser beam on at least one main surface of the first substrate; and forming at least a recording layer on the first substrate. A method of manufacturing an optical information recording medium, comprising the steps of: providing an overcoat on a substrate; and bonding the first substrate and the second substrate so as to face each other. The above object is achieved by a method for manufacturing an optical information recording medium, wherein a substrate having at least a recording layer formed thereon is bonded in a cooled state.

[0014]

Embodiments of the present invention will be described below.

[0015] If it repeats, thickness 0.6m like DVD
When a thin substrate having a thickness of m was used, it was found that when a thin film layer was formed so as to obtain a rewritable recording medium, the substrate could be greatly warped. The cause is that stress remains inside the substrate during the cooling process of the substrate after molding, but the substrate is warped because the substrate is thin. Further, in the cooling process of the substrate after the molding, the substrate is thin due to a change in the temperature of the substrate, so that the substrate is warped.
In the rewritable type, a recording film and a dielectric layer for further protecting the recording film are formed. However, it is considered that a large internal stress is generated by the formation of the dielectric layer, so that a substrate having low mechanical strength is warped. It is also considered that the substrate is warped because the substrate is thin due to a temperature change of the substrate in a cooling process after the formation of the dielectric layer.

The general structure of a rewritable recording medium is such that a recording layer is provided on a transparent substrate such as polycarbonate by sandwiching the recording layer with a dielectric layer and, if necessary, a reflective layer is provided. The dielectric layer protects the recording layer from invading moisture and oxygen, and also protects the substrate from being damaged due to the high temperature of the recording layer during signal recording. Required in most cases.

As the material of the dielectric layer, metal or semimetal
Oxides, nitrides, chalcogenides, fluorides, carbides, etc.
And mixtures thereof, specifically SiO_Two, SiO, Al_TwoO_Three, GeO
_Two, In _TwoO_Three, Ta_TwoO_Five, TeO_Two, TiO_Two, MoO_Three, WO_Three, ZrO_Two, Si_ThreeN_Four, Ge_ThreeN_Four,
AlN, BN, TiN, ZnS, CdS, CdSe, ZnSe, ZnTe, AgF, PbF_Two, MnF_Two, Ni
F_Two, SiC alone or a mixture of these,
Uses diamond thin film, diamond-like carbon, etc.
Wear.

In the case of a phase change recording material, GeSbTe, InSbTe, InSbTeAg, GaSb, InGaSb, GeSnTe, AgSb
Alloys such as Te can be used. Further, a material recorded by another mechanism may be used.

The dielectric layer and the recording layer can be formed by a sputtering method or a vacuum evaporation method.

Meanwhile, it is known that the stress in the substrate or the stress in the thin film layer can be reduced by annealing before the bonding for the above-mentioned problem. However, the warpage of the substrate could not be reduced by the annealing treatment. When an optical disc is manufactured by bonding using a substrate having such a large warp, the optical disc also has a large warp (tilt), and as a result, is not practical.

In order to solve the above-mentioned problems, the inventors have found that if a substrate having a large warp is heated or cooled and bonded together while controlling the tilt, the tilt of the manufactured optical disk can be suppressed to a small value. Was found.

That is, it has been found that the tilt of a substrate warped in the process of forming a thin film layer can be largely changed by heating or cooling. This is considered to be due to the so-called bimetal effect because the thermal expansion coefficients of the resin substrate and the thin film layer are different. In the case of bonding with a substrate whose tilt is suppressed to be small by the temperature control, the tilt of the completed disc also becomes small.

Also, when the tilt of the substrate before bonding is too small (the substrate is flat), the tilt of the finished disk may be large. In this case, too, the temperature of the substrate is controlled to give a slight When the discs are attached with a tilt (in a direction in which the thin film layer becomes convex), the tilt of the disc can sometimes be reduced.

Hereinafter, the present invention will be described in detail.

[0025]

(Example 1) Here, a structure in which at least a dielectric layer and a recording layer are laminated (hereinafter referred to as a laminated information recording layer) on a surface provided with a guide groove for signal recording is 0.6 m thick.
A method for manufacturing a single-sided recording / reproducing disk, in which a first substrate having a thickness of m and a second substrate having no laminated information recording layer are bonded while being heated, will be described.

The substrates 11 and 12 in FIG. 1 are the same, and have a thickness of 0.6 mm and a diameter of 12 manufactured by the injection method.
This is a polycarbonate substrate having a diameter of 0 mm and a center hole diameter of 15 mm, and a guide groove for signal recording is provided on the upper surface.

The laminated information recording layer 13 is provided on the substrate 11. As the laminated information recording layer 13, a ZnS—SiO ₂ layer (ZnS and S
110 nm of a dielectric layer made of a mixture of iO ₂ , and 3 of a phase-change type recording layer (GeSbTe alloy) which reversibly changes state between amorphous and crystalline by laser irradiation.
0 nm, a ZnS-SiO ₂ layer of 20 nm, and an Al film as a reflection layer of 100 nm were laminated.

The structure of the bonding apparatus includes the leveling step shown in FIG. 2 and the curing step shown in FIG. The substrate 11 is placed on the lower pallet 21 of FIG.
Put. The substrates 11 and 12 are sucked by vacuum. Thereafter, the resin application nozzle 23 is inserted between the substrate 11 and the substrate 12 while rotating the lower pallet 21 to apply the resin 231.

Thereafter, the vacuum on the upper pallet 22 is released,
Spin at a high speed to level the resin 231.

Next, the process proceeds to the curing step shown in FIG. 3, and is placed on the curing pallet 31 and irradiated with an ultraviolet lamp 32 to cure the adhesive, thereby completing the disk. In this curing step, after the curing pallet 31 is heated to 70 ° C., the substrate is placed and cured while being heated. As a heating means, a thermocouple or the like is wound and heated. Two types of disks were bonded together by a method in which the disk was bonded by the method of curing while heating and a disk in which the substrate was not heated for comparison.

Next, the warpage angles of the two types of disks were measured. Note that the warp angle is defined as shown in FIG. Substrate 41
Is held on a support table 42 so as to be horizontal near the center thereof, and a laser beam 43 shaped into parallel light having a diameter of about 1 mm is incident on the disk surface from below, and the angle formed with the reflected light 44 is changed to a warp angle α. (°). The warp angle α allowed for an optical disc differs depending on the system used, but needs to be suppressed to, for example, about 0.7 ° or less. Table 1 shows the average warp angle of each of 20 optical disks bonded by using two types of substrates. The warpage angle of the disks bonded together while heating is small.

[0032]

[Table 1] In this case, the lower pallet at the time of leveling was not heated because the warpage of the substrate was small due to vacuum suction, but the lower pallet was also provided with a heating means for leveling.

Although the heating temperature is set to 70 ° C., the same effect can be obtained if the heating temperature is in the range of 40 ° C. to 100 ° C. 40
If the temperature is lower than 100 ° C., the effect of changing the tilt of the substrate is small, and if it is higher than 100 ° C., the resin substrate may be deformed due to thermal damage. (Embodiment 2) Here, a first structure having a thickness of 0.6 mm in which at least a structure in which a dielectric layer and a recording layer are laminated (hereinafter referred to as a laminated information recording layer) is provided on a surface provided with a guide groove for signal recording is provided. A method for manufacturing a single-sided recording / reproducing disk which is bonded to a substrate while cooling a second substrate having no laminated information recording layer will be described. The substrate used this time has a very small warpage and is almost flat.

With the configuration of the bonding apparatus similar to that of the first embodiment, the pallet at the time of curing is cooled to 10 ° C., and then the substrate is placed and cooled to perform curing. As a cooling means, tap water or the like is inserted into a hardening pallet and cooled. For comparison with a disk bonded by the above-described method of curing while cooling, two types of disks without cooling the substrate were bonded.

Next, the warpage angles of the two types of disks were measured in the same manner as in the first embodiment. Table 2 shows the average warp angle of each of 20 optical disks bonded by using two types of substrates. The warpage angle of the discs bonded while heating is small

[0036]

[Table 2] Although the cooling temperature is set to 10 ° C., the same effect can be obtained in the range of −20 ° C. to 20 ° C. When the temperature is higher than 20 ° C., the effect of changing the substrate tilt is small and −20 ° C.
If the temperature is lower than ℃, cracks or the like may occur in the thin film layer. (Embodiment 3) Here, a 0.6 mm-thick first structure having a structure in which at least a dielectric layer and a recording layer are laminated on a surface provided with a guide groove for signal recording (hereinafter, a laminated information recording layer) is provided. The same laminated information recording layer as the first substrate facing the substrate;
A method for manufacturing a double-sided recording / reproducing disk to be bonded while heating the substrate will be described.

The substrates 51 and 52 shown in FIG. 5 are the same and have a thickness of 0.6 mm and a diameter of 12 mm manufactured by the injection method.
This is a polycarbonate substrate having a diameter of 0 mm and a center hole diameter of 15 mm, and a guide groove for signal recording is provided on the upper surface. Substrate 5
The laminated information recording layers 53 and 54 are provided on the layers 1 and 52. As a laminated information recording layer, a ZnS—SiO ₂ layer (ZnS and Si) serving as a dielectric layer is formed on the substrates 51 and 52 by a sputtering method.
A dielectric layer made of a mixture of O ₂ ) was 110 nm, and a phase-change recording layer (GeSbTe alloy) that reversibly changed its state between amorphous and crystalline by laser irradiation was 30 nm.
nm, the ZnS-SiO ₂ layer is 20 nm, and the reflection layer A
1 film was laminated to 100 nm.

Next, in order to protect the laminated information recording layer, an ultraviolet curable resin is formed to a thickness of 10 μm by a spin coating method, and irradiated with ultraviolet rays to provide overcoats 55 and 56. The substrates 51 and 52 were bonded by a slow-acting UV method. After applying the UV-curable adhesive mainly composed of a cation polymerization type resin to the overcoated substrate in a thickness of 20 μm by using a screen printing method, and then irradiating with ultraviolet rays to develop the adhesive to have adhesiveness. Train closely and bond.

As shown in FIG. 6, the structure of the laminating apparatus is as follows. The substrate, which has been irradiated with ultraviolet rays and has adhesiveness, is placed on the lower pallet 61 and the upper pallet 62, and the lower pallet is raised to perform superposition. After that, pressing is performed and bonding is performed. The upper pallet holds the disk by vacuum suction. The upper pallet and the lower pallet can be heated. As a result, the substrate can be heated, and the superposition can be performed while heating. As a heating means, a thermocouple or the like is wound around a pallet for heating. In this case, two types of discs that were not heated at the time of superposition were bonded for comparison with discs that were superposed at a heating temperature of 70 ° C.

Next, the warpage angles of the two types of bonded disks were measured in the same manner as in Example 1. Each one of optical disk
Table 3 shows the average warp angles of the 00 sheets. The warp angle is small when heated during superposition.

[0041]

[Table 3] Although the heating temperature is set to 70 ° C., the same effect can be obtained if the heating temperature is in the range of 40 ° C. or more and 100 ° C. or less. When the temperature is lower than 40 ° C., the effect of changing the tilt of the substrate is small and 100 ° C.
If the temperature exceeds ℃, the resin substrate may be deformed by thermal damage. (Example 4) Here, a 0.6 mm-thick first structure in which at least a structure in which a dielectric layer and a recording layer are laminated (hereinafter referred to as a laminated information recording layer) is provided on a surface where a guide groove for signal recording is provided. The same laminated information recording layer as the first substrate facing the substrate;
A method of manufacturing a double-sided recording / reproducing disk to be bonded while cooling the substrate will be described. The substrate used this time has a very small warpage and is almost flat.

With the configuration of the bonding apparatus similar to that of the third embodiment, the upper pallet and the lower pallet at the time of lamination can be cooled. As a result, the substrate can also be cooled. It can be carried out. As a cooling means, tap water or the like is inserted into a pallet for cooling. In this case, two types of discs that were not cooled at the time of superposition were bonded together for comparison with a disc superimposed at a cooling temperature of 10 ° C.

Next, the warpage angles of the two types of bonded disks were measured in the same manner as in the first embodiment. Table 4 shows the average warp angle of each of the 100 optical disks. The warp angle is small when cooled during superposition.

[0044]

[Table 4] Although the cooling temperature is set to 10 ° C., the same effect can be obtained in the range of −20 ° C. to 20 ° C. When the temperature is higher than 20 ° C., the effect of changing the substrate tilt is small and −20 ° C.
If the temperature is lower than ℃, cracks or the like may occur in the thin film layer.

[0045]

According to the present invention, a flat optical disk with a small tilt can be provided even for a single-sided recording / reproducing type and a double-sided recording / reproducing type in which two thin substrates of about 0.6 mm are bonded.

Accordingly, it is possible to shorten the wavelength of the laser and increase the NA of the objective lens, and it is possible to supply an optical disk system capable of realizing higher density recording than before.

[Brief description of the drawings]

FIG. 1 is a structural diagram of an optical disk used in an embodiment of the present invention.

FIG. 2 is a diagram showing a leveling step in one embodiment of the present invention.

FIG. 3 is a diagram showing a curing step according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating a method of measuring a warp angle.

FIG. 5 is a structural diagram of an optical disk used in an embodiment of the present invention.

FIG. 6 is a diagram showing a bonding apparatus used in one embodiment of the present invention.

[Explanation of symbols]

11, 12, 41, 51, 52 ··· Substrate 13, 53, 54 ···· Laminated information recording layer 21, 61 ··· Lower surface pallet 22, 62 ··· Upper surface pallet 23 ···・ Resin coating nozzle 31 ・ ・ ・ ・ Curing pallet 32 ・ ・ ・ ・ Ultraviolet lamp 42 ・ ・ ・ ・ Support base 43 ・ ・ ・ ・ Laser light 44 ・ ・ ・ ・ Reflection light 55, 56 ・ ・ ・ ・ Overcoat

Claims (11)

[Claims] A step of forming a first substrate and a second substrate; and a step of forming a recording layer on at least one main surface of the first substrate, on which information can be recorded by light irradiation. A method for manufacturing an optical information recording medium, comprising: a step of bonding the first substrate and the second substrate so as to face each other, wherein at least the recording of the first substrate and the second substrate is performed. A method for manufacturing an optical information recording medium, wherein the bonding is performed while the substrate on which the layer is formed is heated. 2. A step of forming a first substrate and a second substrate; and a step of forming a recording layer on at least one main surface of the first substrate, on which information can be recorded by irradiation of light. A method for manufacturing an optical information recording medium, comprising: a step of bonding the first substrate and the second substrate so as to face each other, wherein at least the recording of the first substrate and the second substrate is performed. A method for manufacturing an optical information recording medium, wherein the bonding is performed while the substrate on which the layer is formed is cooled. 3. The method for manufacturing an optical information recording medium according to claim 1, wherein said bonding is performed with a radical polymerization type ultraviolet curable adhesive. 4. A step of forming a first substrate and a second substrate, and a step of forming a recording layer on at least one main surface of the first substrate, on which information can be recorded by irradiation of light, A method for manufacturing an optical information recording medium, comprising: a step of providing at least an overcoat on the recording layer of the first substrate; and a step of bonding the first substrate and the second substrate so as to face each other. A method of manufacturing an optical information recording medium, wherein the bonding is performed in a state where at least a substrate, on which the recording layer is formed, of the first substrate and the second substrate is heated. . 5. A step of forming a first substrate and a second substrate, and a step of forming a recording layer on at least one main surface of the first substrate, on which information can be recorded by irradiation of light, A method for manufacturing an optical information recording medium, comprising: a step of providing at least an overcoat on the recording layer of the first substrate; and a step of bonding the first substrate and the second substrate so as to face each other. Wherein the bonding is performed in a state where at least the substrate on which the recording layer is formed is cooled out of the first substrate and the second substrate. . 6. The method for manufacturing an optical information recording medium according to claim 4, wherein the bonding is performed with an ultraviolet-curable adhesive mainly composed of a cationic polymerizable resin. 7. The method for manufacturing an optical information recording medium according to claim 4, wherein said bonding is performed with an adhesive sheet. 8. The optical information recording medium according to claim 1, wherein the material of the recording layer is a phase change material that changes state reversibly between amorphous and crystalline. Manufacturing method. 9. A heating temperature of the substrate is 40 ° C. or more and 100 ° C.
The method for producing an optical information recording medium according to claim 1, wherein the temperature is lower than or equal to ° C. 5. 10. The cooling temperature of the substrate is not lower than −20 ° C.
The method for producing an optical information recording medium according to claim 2, wherein the temperature is 0 ° C. or lower. 11. The method for manufacturing an optical information recording medium according to claim 1, wherein the thickness of the substrate is 0.8 mm or less.