The present invention contains subject matter related to Japanese Patent Application No.JP 2005-249379 filed on Aug. 30, 2006, and Japanese Patent Application No. JP 2006-143766 filed on May 24, 2006, the entire contents of which being incorporated herein by reference.
1. Field of the Invention
The invention relates to a manufacturing method of an optical disk and its manufacturing apparatus and, more particularly, to a manufacturing method of an optical disk and its manufacturing apparatus which are applied to, for example, a multilayer optical disk having two or more information recording layers.
2. Description of the Related Arts
In recent years, in the optical disk field, the realization of a large recording capacity is demanded. To realize the large recording capacity, it is considered that multilayer optical disks each having a plurality of information recording layers are desirable (refer to Patent Document JP-A-2003-91868). Among them, the optical disk having two information recording layers has a possibility that it is put into practical use first. In the case of a read only optical disk, a reflecting film of silver, aluminum, or the like is formed. In the case of a recordable optical disk, a recording film such as a phase-change type recording film or the like is formed. In the present specification, the reflecting film or the recording film is generally called an information recording layer.
A high-density optical disk has a recording capacity of about 25 Gbytes for a one-side single-layer or about 50 Gbytes for a one-side double-layer. In order to decrease a diameter of a spot of a beam for recording and reproduction, for example, a wavelength of a light source is set to 405 nm and a numerical aperture NA of an objective lens is set to a large value of 0.85.
In the high-density optical disk which has two information recording layers and in which information is read out of one side, an L0 layer as an information recording layer serving as a reference layer is formed at a position of a depth of 0.1 mm (100 μm) when seen from the incident direction of a laser beam and an L1 layer as an information recording layer serving as an additional layer is formed at a position of a depth of 75 μm.
In manufacturing steps of the optical disk having the two information recording layers as mentioned above, first, when a substrate is formed, concave and convex portions of the L0 layer are formed onto one principal plane of the substrate, an intermediate layer made of an ultraviolet hardening type resin is formed onto the L0 layer, and concave and convex portions of the L1 layer are formed onto the intermediate layer. In the case of the read only optical disk, concave/convex portions modulated in accordance with the information to be recorded are formed. In the case of the recordable optical disk, concave/convex portions modulated in accordance with the information to be previously recorded such as addresses, spiral groove, or the like are formed.
The concave/convex portions of the L1 layer are formed by pressing a stamper to the intermediate layer and irradiating ultraviolet rays in the pressing state. In the following explanation, the ultraviolet hardening type resin is properly called a “UV resin”.
As forming methods of the concave/convex portions of the L1 layer in the related art, for example, a roller pressure bonding method, a spin bonding method, a pad pressure bonding—pressure degassing method, an adhering method in a vacuum, and the like have been proposed.
Subsequently, a stamper 103a is overlaid onto the UV resin 102a. A pressure is applied to the stamper 103a from a position over the substrate 101a by a roller 104 serving as pressing means. Thus, the concave/convex portions of the stamper 103a are transferred to the UV resin 102a as an intermediate layer. After that, the ultraviolet rays are irradiated to the UV resin 102a by using an ultraviolet irradiator (UV irradiator) U, so that the UV resin 102a is hardened.
According to the roller pressure bonding method, if a resin of low viscosity is used, it is difficult to hold uniformity of a film thickness. Further, resin burs occur frequently in an outer rim edge portion. Moreover, in the case of using a resin of high viscosity or a PSA (Pressure Sensitive Adhesive), since bubbles are easily trapped, it is necessary to raise a pressure of the roller.
According to the spin bonding method, the resin 102b can be preferably and uniformly filled. However, a resin leakage into the outer rim edge portion, generation of burs, and the like increase. Further, there is such a problem that it is difficult to peel off the stamper 103b.
The pad pressure bonding—pressure degassing method has such an advantage that the generated bubbles can be fined by applying the pressure. However, according to the pad pressure bonding—pressure degassing method, there is such a tendency that the fine bubbles are diffused into the UV resin 102d. If such a disk is used in the atmosphere, since the fine bubbles are expanded, there is such a problem that it is liable to cause deterioration in quality of the disk such as corrosion of the recording film or the like.
According to the adhering method in the vacuum, by pressing the stamper 103d to the UV resin 102d coated onto the substrate 101d in the vacuum, the concave/convex portions of the stamper 103d are transferred, so that the number of generated bubbles can be reduced. However, there is the following problem.
Subsequently, the reflecting film or the recording film is formed as an information recording layer onto the substrate. In the film forming step of the information recording layer, as shown in
Subsequently, in a UV resin coating step, as shown in
Subsequently, in a transfer step of the concave/convex portions, as shown in
Subsequently, as shown in
After the stamper 103d and the substrate 101d were arranged as mentioned above, the stamper 103d is pressed by, for example, a center bush 121 as pressing means. The two-stage centering pin 122 is moved downward. The stamper 103d is pressed to the UV resin 102d. The concave/convex portions of the stamper 103d are transferred to the UV resin 102d.
According to the foregoing adhering method in the vacuum, the number of generated bubbles upon transfer can be reduced. However, when the stamper 103d is adhered to the substrate 101d, since there are various entering methods of the bubbles in dependence on a form of a relative deformation of a shape of the stamper 103d to the substrate 101d, there is such a problem that it is difficult to certainly suppress the generation of the bubbles.
For example, as shown in
If a surface of the stamper 103d and a surface of the UV resin 102d are simultaneously adhered as shown in
Further, as shown in
On the other hand, there is a case where forces act accidentally in the directions shown by arrows 140d as shown in
However, in the adhering method in the vacuum, since the operation of the stamper which can suppress the generation of the bubbles as shown in
It is, therefore, desirable to provide a manufacturing method of an optical disk and its manufacturing apparatus, in which the generation of bubbles can be certainly suppressed and the optical disks of high quality can be stably provided.
According to an embodiment of the present invention, there is provided a manufacturing method of an optical disk in which an information recording layer is formed onto a resin layer laminated on one surface of a substrate, comprising the steps of:
coating the resin layer onto the surface of the substrate;
arranging the substrate and a stamper into a chamber so that one surface of the resin layer and one surface of the stamper on which concave/convex portions have been formed face almost in parallel;
setting the chamber into an almost vacuum state while holding the facing state of the substrate and the stamper;
changing the chamber from the almost vacuum state to a state of an atmospheric pressure or higher, overlaying the substrate and the stamper, and pressing the stamper by a differential pressure between a pressure in the almost vacuum state and a pressure which is equal to or higher than the atmospheric pressure, thereby adhering the substrate and the stamper and transferring the concave/convex portions to the resin layer; and
hardening the resin layer to which the concave/convex portions have been transferred.
According to another embodiment of the present invention, there is provided a manufacturing apparatus of an optical disk, comprising:
supporting means holding a substrate coated with a resin layer on one surface and a stamper in a chamber so that the resin layer and one surface of the stamper on which concave/convex portions have been formed face; and
control means setting the chamber into an almost vacuum state while holding the facing state of the substrate and the stamper and changing the chamber from the almost vacuum state to a state of an atmospheric pressure or higher,
wherein by cancelling the holding state of the stamper and the substrate synchronously with the change in air pressure, the substrate and the stamper are overlaid, and by pressing the stamper by a differential pressure between a pressure in the almost vacuum state and a pressure which is equal to or higher than the atmospheric pressure, the substrate and the stamper are adhered and the concave/convex portions are transferred to the resin layer.
According to the embodiments of the present invention, there is such an effect that the generation of the bubbles can be certainly suppressed when the concave/convex portions of the stamper are transferred to an intermediate layer.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
An embodiment of the invention will be described hereinbelow with reference to the drawings. An example of a high-density optical disk to which a manufacturing method according to an embodiment of the invention can be applied will be described with reference to
In such an optical disk, an information signal is recorded and reproduced by irradiating a laser beam to an information recording layer from the side of a cover layer 15. For example, the laser beam having a wavelength of 400 to 410 nm is converged by an objective lens 16 having a numerical aperture (NA) of 0.84 to 0.86 and irradiated to either the L0 layer or the L1 layer serving as an information recording layer from the cover layer 15 side, so that the information signal is recorded or reproduced.
Such a high-density optical disk has a construction in which the L0 layer, an intermediate layer 12, the L1 layer, and the cover layer 15 are sequentially laminated onto a substrate 11. The cover layer 15 is formed by an adhesive layer 13 having a thickness of, for example, 15 μm and a polycarbonate (hereinafter, properly abbreviated to “PC”) sheet 14 having a thickness of, for example, 60 μm.
As a material of the substrate 11, a resin material such as polycarbonate resin, polyolefin resin, acrylic resin, or the like or glass may be used. It is desirable to use the resin material from a viewpoint of costs or the like. As a resin material, for example, cycloolefin polymer (“ZEONOR”, registered trademark) or PC may be used.
A molding method of the substrate 11 is not particularly limited but it is sufficient to use a method whereby a desired shape and smoothness of the surface of the substrate which is optically adequate can be obtained. For example, an injection molding method (injection method) or a photopolymer (2P method) method using an ultraviolet hardening resin may be used.
Each of the L0 layer and the L1 layer as information recording layers is a reflecting film or a recording film formed on the concave/convex portions of the substrate. If the optical disk is a read only type disk, for example, the reflecting film made of gold (Au), silver (Ag), a silver alloy, aluminum (Al), an aluminum alloy, or the like is formed. If the optical disk is a write once type disk, a recording film formed by sequentially laminating, for example, a reflecting film and a recording layer made of an organic pigment material is constructed. If the optical disk is a rewritable type disk, for example, a recording film formed by sequentially laminating a reflecting film, a lower layer dielectric layer, a phase-change recording layer, and an upper layer dielectric layer is constructed.
The intermediate layer 12 serving as a resin layer having a thickness of, for example, 25 μm is formed on the L0 layer formed on the substrate 11. The L1 layer is formed on the intermediate layer 12. As an intermediate layer 12, for example, an ultraviolet hardening resin may be used. An electron beam hardening resin may be used as an intermediate layer 12.
The cover layer 15 is formed on the L1 layer formed on the intermediate layer 12. The cover layer 15 is formed in order to protect the optical disk. The information signal is recorded and reproduced by, for example, converging the laser beam to the information recording layer through the cover layer 15.
As a cover layer 15, an adhesive layer and a PC sheet, a UV resin, or the UV resin and the PC sheet may be used. The cover layer 15 has a thickness of, for example, about 75 μm. For instance, the cover layer 15 is constructed by the adhesive layer 13 having a thickness of 15 μm and the PC sheet 14 having a thickness of 60 μm.
The manufacturing method of the optical disk according to the embodiment of the invention will now be described.
By dropping the UV resin 2 while rotating the substrate 1, a centrifugal force is caused for the UV resin 2. The UV resin 2 is uniformly spread from the middle portion to the outer rim on the substrate, so that the surface of the substrate 1 is coated flat with the UV resin 2.
In this instance, as shown in
A method of coating the UV resin 2 is not limited to the spin-coating method but another method may be used. Specifically speaking, for example, a roll-coating, a die-coating, a dip-coating, a spray-coating, a casting, or the like may be used.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
By pressing the stamper 5 to the UV resin 2 in the semi-hardening state, the concave/convex portions of the stamper 5 are transferred to the UV resin 2 and the concave/convex portions are formed on one principal plane of the UV resin 2. In the embodiment, the stamper 5 is pressed to the UV resin 2 and the concave/convex patterns are transferred by the method using a pressure difference that is caused between almost the vacuum state and the state where an air pressure which is equal or higher than the atmospheric pressure is applied (hereinafter, referred to as a differential pressure laminating method).
According to the differential pressure laminating method, as shown in
Subsequently, since the vacuum state is broken and the atmospheric pressure is applied to the stamper 5 from the upper position as shown by arrows A, the stamper 5 is pressed to the UV resin 2 and adhered to the substrate 1 through the UV resin 2. Thus, the concave/convex portions of the stamper 5 are transferred to the UV resin 2 as an intermediate layer. Since the standard atmospheric pressure is equal to 101325 Pa, the air pressure of 101275 Pa (=101325 Pa−50 Pa) presses the stamper 5 downward as shown by the arrows A. The stamper 5 is pressed by a pressure of about 2000 times. In a range from the vacuum to the atmospheric pressure, the pressure changes with a certain leading time.
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
The foregoing differential pressure laminating method will now be described with reference to
While holding the facing state of the stamper 5 and the substrate 1, they are disposed in, for example, the vacuum chamber (not shown) and, thereafter, the inside of the vacuum chamber is vacuum-evacuated by a vacuum pump. The vacuum chamber is evacuated to, for example, 5 to 500 Pa, preferably, 5 to 200 Pa. The inside of the vacuum chamber and a gap between the substrate 1 and the stamper 5 which face are set into the vacuum state.
Subsequently, as shown in
When the vacuum is broken, the holding state of the supporting mechanisms to hold the interval between the stamper 5 and the substrate 1 is cancelled simultaneously with the release of the atmospheric pressure. By the cancellation of the supporting mechanisms synchronized with the release of the atmospheric pressure, the stamper 5 is adhered onto the substrate 1 in the state where its middle portion is bent downward. When the middle portion of the stamper 5 is bent downward, the simultaneous adhesion of the substrate 1 in both directions can be executed, that is, the adhesion in the direction from the middle portion to the inner rim portion and the adhesion in the direction from the middle portion to the outer rim portion can be simultaneously executed. Thus, the capture of the bubbles can be prevented and the adhesion in which the generation of the burs in the outer rim portion is small can be performed.
The cancellation of the supporting mechanisms is made by controlling the supporting mechanism 22 of the inner rim side of the stamper 5 and the supporting mechanism 23 of the outer rim side. For example, the supporting mechanisms are controlled so as to simultaneously move the supporting mechanism 22 of the inner rim portion and the supporting mechanism 23 of the outer rim portion downward in the direction shown by arrows 24a at a predetermined speed, for example, 2 mm/sec synchronously with the release of the atmospheric pressure. The supporting mechanism 22 of the inner rim portion operates so as to be pressed downward by a centering pin depressing mechanism 26. The supporting mechanism 23 of the outer rim portion operates so as to be pressed downward by an outer rim pressure ring depressing mechanism 27.
By controlling as mentioned above, the middle portion of the stamper 5 is bent downward and come into contact with the UV resin 2. After that, the stamper 5 is adhered to the substrate 1. By forming the state where the middle portion of the stamper 5 is bent and adhering the substrate 1 and the stamper 5, the portion in the inner rim direction of the substrate 1 and the portion in the outer rim direction are simultaneously adhered and the generation of the bubbles can be reduced.
The adhering state in which the generation of the burs in the outer rim portion of the disk is small can be formed. Further, if the bubble is brought in, since the gas is compressed by the differential pressure between the vacuum and the atmospheric pressure shown by arrows 25, a volume of the mixed bubble decreases. Thus, the optical disk of high quality which does not exert an adverse influence on recording/reproducing efficiency of the signal can be manufactured.
For example, since the atmospheric pressure is equal to about 101325 Pa, the pressing pressure of about 2000 times can be applied to the stamper 5 by the differential pressure between the vacuum pressure of, for example, about 50 Pa and the atmospheric pressure. Therefore, even if the bubble was mixed between the stamper 5 and the substrate 1, since a volume of the bubble is decreased to 1/2000, no adverse influence is exerted on recording/reproducing characteristics of the signal.
Specifically speaking, for example, if the bubble having a diameter of 30 μm entered the gap between the stamper 5 and the substrate 1, the diameter is decreased to 2.5 μm by the differential pressure. Therefore, the optical disk of the high quality which does not exert an adverse influence on the stable recording and reproduction of the signal can be manufactured.
In the embodiment of the invention, the vacuum chamber is changed from almost the vacuum state to the state where the atmospheric pressure is applied. Further, the invention is not limited to the atmospheric pressure but the vacuum chamber may be forcedly pressurized to the atmospheric pressure or higher. In such a case, since a larger pressing force is generated, the volume of the entering bubble can be more decreased.
First,
Subsequently, as shown in
Subsequently, as shown in
Subsequently, as shown in
Although the flat stamper has been used as a stamper in the above example, for instance, the concave/convex portions can be also transferred by using a curved stamper.
As shown in
Thus, the apparatus can be controlled so as to generate bubbles 53 only in the outer rim portion and an optical disk 10 of high quality having excellent recording and reproducing characteristics can be manufactured. The curved stamper 40′ can be manufactured by controlling molding conditions upon injection molding.
According to the creation of the concave/convex portions using the curved stamper 40′, when the differential pressure lamination is executed, the stamper and the substrate can be easily arranged at positions suitable for suppressing the generation of the bubbles, so that the construction can be simplified.
That is, in the outer rim portion, since the UV resin 50 of the portion where the curved stamper 40′ and the substrate 30 are come into contact with each other functions like an O-ring, merely by arranging the two-stage centering pin 35 for closing a center hole portion while performing centering of both of them, they can be merely arranged at the positions suitable for suppressing the generation of the bubbles.
By moving the centering pin 35 downward as shown by an arrow 51 synchronously with the differential pressure lamination due to the release to the atmosphere, the curved stamper 40′ is adhered to the substrate 30 without generating the bubbles which exert an adverse influence on the recording/reproducing characteristics.
Although the release to the atmosphere has been performed almost from the vacuum state according to the foregoing differential pressure laminating method, in place of releasing to the atmosphere, it is also possible to introduce the compressed air (a gas other than the air can be also used) into the chamber and forcedly pressurize by the air pressure which is equal to or higher than the atmospheric pressure. As a compressed air, the air of about a middle pressure (10 to 3 kg/cm2) which is used in an air pressure system that is used in a factory or the like or the air of a low pressure (3 kg/cm2 or lower) is used. The compressed air is produced by a compressor, accumulated in a tank or the like, and supplied to the differential pressure laminating apparatus through pipes, control valves, and the like.
The differential pressure laminating method of pressurizing by the air pressure which is equal to or higher than the atmospheric pressure can be also realized by steps and an apparatus similar to those of the differential pressure laminating method of performing the release to the atmosphere mentioned above. The differential pressure laminating method of pressurizing will be described with reference to a differential pressure laminating apparatus of
In
First, the disk substrate 30 having the L0 layer is coated flat with the UV resin and, as shown in
The outer diameter of the stamper 40 is set to be slightly larger than that of the disk substrate 30. The concave/convex portions have preliminarily been formed on the stamper so that the forming surface of the concave/convex portions faces downward. The stamper 40 is set into the vacuum chamber and vacuum-evacuated. The vacuum evacuation is executed by opening the valve 45a, closing the valve 45b, and evacuating the air from the vent hole 31a in the direction shown by the arrow 37a.
Subsequently, the centering pin 35 and the outer rim ring 34 are depressed by downwardly moving the centering pin depressing mechanism 32 and the outer rim pressure ring depressing mechanism 33. By this downward depressing operation, the stamper 40 is moved to the intermediate position which is slightly lower than the initial position. In the case of using the curved stamper 40′ shown in FIGS. 7A and 7B, the curved stamper 40′ is moved until the outer rim portion of the curved stamper 40′ and the outer rim edge portion of the disk substrate 30 are come into contact with each other through the UV resin.
Subsequently, as shown in
In this instance, as shown in
Subsequently, the lower portion of the apparatus is moved downward and the substrate 30 and the stamper 40 which have been vacuum-adhered are taken out of the chamber. After that, by irradiating the ultraviolet rays through the stamper 40, the UV resin is completely hardened. Subsequently, the stamper 40 is peeled off from the substrate 30.
It is also possible to irradiate the ultraviolet rays in the holding state of the pressurization without releasing the chamber to the atmosphere after the adhesion.
As mentioned above, if the compressed air is used, the pressure of 300000 Pa which is 6000 times as large as 50 Pa can be applied from almost the vacuum state of, for example, 50 Pa, so that a volume of the mixed bubble can be reduced into 1/6000. The large pressure can be rapidly applied at the initial stage of the breakdown of the vacuum. When comparing with the release to the atmosphere, it is possible to prevent the adhesion from becoming insufficient and the adhesion can be stably and preferably performed.
Although the embodiment of the invention has been described with respect to the high-density optical disk with the construction in which the L0 layer, the intermediate layer, the L1 layer, and the cover layer have sequentially been laminated onto the substrate, the invention is not limited to such an example. For instance, as shown in
In the optical disk shown in
Although the embodiment of the invention has specifically been described above, the invention is not limited to the foregoing embodiment of the invention but many modifications and variations are possible within the scope of the invention without departing from the spirit of the invention. For example, the invention can be also applied to the case where the stamper is made of a metal material such as nickel. If the information recording layer is the recording film, since the light is hardly transmitted, it is necessary that the ultraviolet rays for hardening the resin are irradiated through a transparent stamper. However, if the information recording layer is the reflecting film, since the light is slightly transmitted, the ultraviolet rays for hardening the resin can be irradiated from the substrate side. In this case, it is unnecessary for the stamper to have the light permeability.
Although the embodiment of the invention has been described with respect to the optical disk having the two information recording layers, the invention can be also applied to an optical disk having three or more information recording layers. It is also possible to form the transfer layer onto a substrate without the signal by the method of the invention and form the disk having one information recording layer. It is also possible to form the transfer layer onto a transparent substrate without the reflecting layer and the recording film although it has the layers with the signal concave/convex portions by the method of the invention and form the disk having one information recording layer. For example, the disk having one information recording layer may be manufactured by recycling a substrate having defective signal transfer performance, a surplus substrate, or the like.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
Number | Date | Country | Kind |
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P2005-249379 | Aug 2005 | JP | national |
P2006-143766 | May 2006 | JP | national |