The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2003-343125 filed on Oct. 1, 2003. The content of the application is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a method of manufacturing a disc-shaped recording medium having single-sided two or more information layers.
2. Description of the Prior Art
DVD-9 exists as a conventional single-sided 2-layered optical disc, and there is known a disc, wherein information layers are formed on both sides of a spacer layer as disclosed in, e.g., Japanese Patent Application Post-Exam Publication No. 8-23941. A recording/reproducing system of the DVD has a numerical aperture given by NA=0.6, and hence a film (layer) thickness distribution of the spacer layer of the single-sided 2-layered optical disc exhibits a margin that is as remarkably large as 55±15 μm in comparison of the film thickness distribution. Therefore, as disclosed in Japanese Patent Application Laid-Open Publication No. 9-161329, a stamper for forming an information face is superimposed on a substrate structuring an optical recording medium with an ultraviolet curing liquid bonding agent interposed therebetween, and the liquid bonding agent may simply be, after being spun off (an outer peripheral edge), cured by irradiation of the ultraviolet rays. According to this conventional method, when forming a spacer layer that is, e.g., 25 μm in thickness, an average thickness of an inner peripheral portion is on the order of 22 μm, and an average thickness of an outer peripheral portion is 29 μm, with the result that the film thickness distribution becomes 7 μm.
In Blu-ray disc that has recently been utilized, the recording/reproducing system has a large numerical aperture such as NA=0.85, and it is therefore required that a substrate thickness be 100±2 μm for acquiring the same mechanical characteristics as the DVD has. Further, in the case of a 2-layered type Blu-ray disc, the film thickness distribution of a light transmissive layer ranging from a light incidence face down to the information layer on a deeper side, is required to be within ±2 μm. Besides, a film thickness distribution of the light transmissive layer down to the information layer on the deeper side plus a spacer layer is likewise required to be within ±2 μm. Hence, excellent uniformity is demanded of each of the light transmissive layer and the spacer layer.
Moreover, the manufacture of the Blu-ray disc needs to control the film thickness distribution that is by far more precise than the conventional DVD-9. In the Blu-ray disc including single-sided two or more information layers, if there occurs unevenness of the film (layer) thickness of the spacer layer interposed between the two information layers, this unevenness affects the recording/reproducing or the reproducing alone, and hence the excellent uniformity of the film thickness is demanded of the spacer layer of the Blu-ray disc including the single-sided two or more information layers.
On the other hand, Japanese Patent Application Laid-Open Publication No. 9-161333 discloses that for forming the light transmissive layer of the optical disc at high accuracy in a short period of time, the liquid ultraviolet curing resin is discharged as droplets over the vicinity of the central portion of the disc-shaped substrate while rotating the disc-shaped substrate, the ultraviolet curing resin is spread throughout from the central side up to the outer peripheral side thereof by dint of a centrifugal force, and the ultraviolet curing resin that has been spread throughout from the central side up to the outer peripheral side is irradiated with spot ultraviolet rays from the central side toward the outer peripheral side of the rotating substrate, thus curing the ultraviolet curing resin to a predetermined thickness sequentially from the central side toward the outer peripheral side. There are disclosed, however, none of specific methods of how the resin is cured to the predetermined thickness.
Further, Japanese Patent Application Laid-Open Publication No. 11-73691 discloses that for uniformizing the thickness of the light transmissive layer of the optical disc throughout the surface of the substrate, after spin-coating a light curing resin, a swelling of the light curing resin that is produced at an outermost peripheral portion of the disc-shaped substrate is covered with a mask so as not to be irradiated with the light, the light curing resin excluding the resin swelling is irradiated with the light and is thus cured, the light curing resin at the resin swelling is removed away by rotating the substrate once again, and the light curing resin left after being removed away is irradiated with the light and is thus cured. This method is a measure against the swelling of the light curing resin at the outermost peripheral portion but does not show any contrivance for ensuring the uniformity of the thickness throughout the surface from the inner periphery to the outer periphery.
It is an object of the present invention to provide a disc-shaped recording medium manufacturing method capable of restraining, when manufacturing a disc-shaped recording medium having a two or more information layers, an occurrence of unevenness of a film thickness of a spacer layer interposed between these inflation layers and thus forming the spacer layer exhibiting high uniformity of the film thickness.
To accomplish the above object, the present inventors acquired the following knowledge as a result of concentrated studies. Namely, a film thickness of an ultraviolet curing resin that is formed by spin-coating basically tends to be small at an inner periphery but large at an outer periphery. If a resin spinning-off time is set long, the film thickness becomes gradually small as it holds a gradient from the inner periphery toward the outer periphery. Accordingly, as partially viewed from the inner periphery toward the outer periphery, there exist time-spans defined by 25 μm at the inner periphery, 25 μm at the intermediate periphery and 25 μm at the outer periphery. Hence, when the film thickness of the ultraviolet curing resin comes to 25 μm at the inner periphery, only the inner periphery is irradiated with the ultraviolet rays and is thus cured. Next, when becoming 25 μm at the intermediate periphery, the intermediate periphery is irradiated with the ultraviolet rays and is thus cured, and sequentially the outer periphery is likewise cured.
To be specific, as shown in
Such being the case, the spin-coating is performed with a pattern shown in
As a result, a film thickness distribution as shown in
Based on this concept, the spin-coating is performed with such a pattern shown in
A method of manufacturing a disc-shaped recording medium according to the present embodiment was devised based on the knowledge acquired by the present inventors. Namely, a first method of manufacturing a disc-shaped recording medium according to the present embodiment includes a step of applying an energy beam curing resin to an inner peripheral portion of a first information layer formed on a disc-shaped substrate, and thereafter disposing a stamper member having a transfer face so that the stamper member faces the disc-shaped substrate, a step of rotating the disc-shaped substrate in order to spin-coat the energy beam curing resin between the disc-shaped substrate and the stamper member, a step of irradiating the energy beam curing resin with an energy beam while rotating the disc-shaped substrate so as to expand an irradiation range toward an outer peripheral side from an inner peripheral side of the disc-shaped substrate, a step of removing the stamper member in a way that leaves, on the disc-shaped substrate, a spacer layer made of the energy beam curing resin with the irradiation of the energy beam, a step of forming a second information layer on the surface of the spacer layer transferred from the transfer face of the stamper member, and a step of forming a light transmissive layer on the second information layer on the spacer layer, wherein the energy beam irradiating step involves keeping the number of revolutions with which the energy beam curing resin comes to have a predetermined film thickness on the inner peripheral side on the disc-shaped substrate, then starting the irradiation of the energy beam, and thereafter changing stepwise the number of revolutions and the irradiation range.
According to the first method of manufacturing the disc-shaped recording medium, when spin-coating and irradiating the energy beam curing resin with the energy beam, the predetermined film thickness is obtained by keeping the number of revolutions with which the energy beam curing resin comes to have the predetermined film thickness on the inner peripheral side on the disc-shaped substrate, then the irradiation of the energy beam is started, and thereafter the number of revolutions and the irradiation range are changed stepwise. This enables the spacer layer exhibiting high uniformity of the film thickness to be formed by restraining an occurrence of unevenness of the film thickness of the spacer layer formed by curing the energy beam curing resin.
A second method of manufacturing a disc-shaped recording medium according to the present embodiment includes a first step of applying an energy beam curing resin to an inner peripheral portion of a first information layer formed on a disc-shaped substrate, and thereafter disposing a stamper member having a transfer face so that the stamper member faces the disc-shaped substrate, a second step of rotating the disc-shaped substrate in order to spin-coat the energy beam curing resin between the disc-shaped substrate and the stamper member, a third step of irradiating the energy beam curing resin with an energy beam while rotating the disc-shaped substrate so as to expand an irradiation range toward an outer peripheral side from an inner peripheral side of the disc-shaped substrate, a fourth step of removing the stamper member in a way that leaves, on the disc-shaped substrate, a spacer layer made of the energy beam curing resin with the irradiation of the energy beam, and a fifth step of forming a second information layer on the surface of the spacer layer transferred from the transfer face of the stamper member, wherein three or more information layers are formed by repeatedly executing the first step through the fifth step so that a second spacer layer is formed of the energy beam curing resin between the first spacer layer transferred from the transfer face of the first stamper member and a second stamper member, and the energy beam irradiating step involves keeping the number of revolutions with which the energy beam curing resin comes to have a predetermined film thickness on the inner peripheral side on the disc-shaped substrate, then starting the irradiation of the energy beam, and thereafter changing stepwise the number of revolutions and the irradiation range.
According to the second method of manufacturing the disc-shaped recording medium, when spin-coating and irradiating the energy beam curing resin with the energy beam, the predetermined film thickness is obtained by keeping the number of revolutions with which the energy beam curing resin comes to have the predetermined film thickness on the inner peripheral side on the disc-shaped substrate, then the irradiation of the energy beam is started, and thereafter the number of revolutions and the irradiation range are changed stepwise. This enables the spacer layer exhibiting high uniformity of the film thickness to be formed by restraining an occurrence of unevenness of the film thickness of the spacer layer formed by curing the energy beam curing resin.
In the second method of manufacturing the disc-shaped recording medium, an information layer is formed on the surface of the spacer layer formed on an outermost side, and thereafter a light transmissive layer can be formed on the information layer.
In the first and second methods of manufacturing the disc-shaped recording medium, it is preferable that the energy beam irradiating step involves keeping the number of revolutions with which the energy beam curing resin comes to have a predetermined film thickness on the inner peripheral side on the disc-shaped substrate, then starting the irradiation of the energy beam, and increasing the number of revolutions after temporarily decreasing the kept number of revolutions while changing the irradiation range of the energy beam.
Further, it is preferable that a relationship between the number of revolutions and the film thickness of the energy beam curing resin in a radial direction which is irradiated with the energy beam, is previously obtained, and the number of revolutions in the irradiation range in the radial direction is changed based on this relationship.
Moreover, it is preferable that the number of revolutions is decreased when the irradiation range in the radial direction exists on an outer peripheral side. It is also preferable the number of revolutions is decreased when the irradiation range in the radial direction exists on an outer peripheral side, and is thereafter increased again.
According to the method of manufacturing the disc-shaped recording medium in the present embodiment, when manufacturing the disc-shaped recording medium having two or three or more information layers, it is feasible to form the spacer layer exhibiting the high uniformity of the film thickness by restraining the occurrence of the unevenness of the film thickness of the spacer layer interposed between these information layers.
A best mode for carrying out the present invention will hereinafter be described with reference to the drawings.
The present embodiment exemplifies a method of manufacturing a single-sided 2-layered type optical disc. To be specific, as shown in
As shown in
Next, as shown in
Subsequently, as shown in
The stamper member 14 is made of an olefin resin, etc. that exhibits transmissivity of ultraviolet-rays and has an easy-to-exfoliate property with respect to the ultraviolet curing resin material, and is disposed so that the transfer face 15 thereof faces the recording face 12 of the disc-shaped substrate 11. Note that the stamper member 14 may have the same diameter as the disc-shaped substrate 11 has, however, its diameter is preferably larger than the disc-shaped substrate 11 in order to ensure a gripping area in consideration of the easy-to-exfoliate property.
Next, the stage 2 is rotated together with the rotary shaft 1, thereby rotating the disc-shaped substrate 11 and the stamper member 14 as shown in
The ultraviolet light source 5 includes a diaphragm mechanism 19 shown in
When irradiated with the ultraviolet rays in
The ultraviolet curing resin 13 interposed between the recording face 12 of the disc-shaped substrate 11 and the transfer face 15 of the stamper member 14 is irradiated with the ultraviolet rays as described above and is thus cured, thereby forming a spacer layer 13a having a layer thickness (film thickness) of 25 μm. The spin-coating and the ultraviolet curing process are, however, executed in a pattern shown in
To describe it more specifically, after spinning for 11 sec at the number of revolutions of 4,000 rpm, a shutter is driven to a diameter of 68 mm in 0.1 sec, wherein the irradiation of the ultraviolet rays is started. Subsequently, the number of revolutions of 4,000 rpm is maintained for 0.3 sec and is thereafter reduced down to 3,200 rpm in 0.3 sec, and this number of revolutions is kept for 0.3 sec. Meanwhile, the shutter is driven up to a diameter of 84 mm in 0.5 sec, and this state is kept for 0.1 sec. Then, the number of revolutions is reduced from 3,200 rpm down to 150 rpm in 0.3 sec, and this number of revolutions is maintained for 0.1 sec. During this period of time, the shutter is driven up to a diameter of 96 mm from 86 mm in 0.1 sec, and this state is kept for 0.5 sec. Then, the number of revolutions is increased up to 4,000 rpm from 150 rpm in 0.3 sec, and this number of revolutions is maintained for 8.5 sec. Thus, a swelling is prevented from being formed on the outermost peripheral portion by sharply increasing the number of revolutions. In the meantime, the shutter is driven up to a diameter of 116 mm from 96 mm in 8 sec, wherein a range corresponding to this diameter is irradiated with the ultraviolet rays for 1 sec. Note that the ultraviolet light source has consecutively irradiated the range from the diameter of 68 mm up to 116 mm throughout with the ultraviolet rays.
Next, as shown in
Next, after forming an information layer as a second layer on the recording face 13c of the spacer layer 13a, a translucent layer 16 is formed of a resin material over the space layer 13a by a spin coat method. The way of how the translucent layer 16 is formed by the spin-coating will be explained with reference to
As shown in
Next, as shown in
Next, as shown in
The number of revolutions and revolution time for the spin-coating of the resin liquid can be properly determined depending on a thickness of the resin layer 51 to be formed and on a viscosity of the resin liquid. In the case of forming the translucent layer of which a thickness is on the order of 30 through 300 μm, it is preferable that the viscosity of the resin liquid is selected from a range of 100 cP through 100,000 cP, the number of revolutions is selected from a range of 500 rpm through 6,000 rpm, and the revolution time is chosen from a range of 2 sec through 30 sec, respectively.
Next, as shown in
As explained above, the recording face 12 is formed between the disc-shaped substrate 11 and the spacer layer 13a, and another recording face 13c is formed between the spacer layer 13a and the translucent layer 16, whereby the single-sided 2-layered type optical disc can be manufactured. In this type of optical disc, the spacer layer 13a has a film thickness distribution of 25±1 μm, the translucent layer 16 has a film (layer) thickness distribution of 75±1 μm, and it is possible to attain a film thickness distribution of 100±2 μm of a total film thickness of the spacer layer 13a plus the translucent layer 16.
Hence, the manufacturing method according to the present embodiment is applied to manufacturing, for example, a Blu-ray disc containing the single-sided two or more information layers, whereby the film thickness distribution of the spacer layer plus the translucent layer can be within ±2 μm and the recording/reproducing process can be therefore performed without any troubles.
Further, in the case of manufacturing the optical disc including two spacer layers by further forming another spacer layer on the spacer layer 13a in
Note that compositions of the ultraviolet curing resin used for forming the spacer layers shown in
Further, the following are materials usable in the mixtures given above.
Monofunctional:
Allyl(meta)acrylate, benzyl(meta)acrylate, butoxy-(meta)acrylate, butadiol(meta)acrylate, butoxy-triethylene glycotu(meta)acrylate, ECH denatured butyl(meta)acrylate, t-butylaminoethyl(meta)acrylate, caprolactone(meta)acrylate, 2-cyanoethyl(meta)acrylate, cyclohexyl(meta)acrylate, dicyclopentanyl(meta)acrylate, alicyclic denatured neopentylglycol(meta)acrylate, 2,3-dibromopropyl(meta)acrylate, dicyclopentenyl(meta)acrylate, dicyclopentenyloxy(meta)acrylate, N,N-diethylaminoethyl(meta)acrylate, 2-ethoxyethyl(meta)acrylate, 2-ethylhexyl(meta)acrylate, glycerol(meta)acrylate, glycidyl(meta)acrylate, heptadecaphlorodecyl(meta)acrylate, 2-hydroxyethyl(meta)acrylate, caprolactone denatured 2-2-hydroxyethyl(meta)acrylate, 2-2-hydroxypropyl(meta)acrylate, isobornyl(meta)acrylate, isodecyl(meta)acrylate, isooctyl(meta)acrylate, lauryl(meta)acrylate, methoxydietyleneglycol(meta)acrylate, methoxydipropyleneuricol(meta)acrylate, morpholine(meta)acrylate, phenoxyethyl(meta)acrylate, phenoxyhydroxypropyl(meta)acrylate, EO denatured phenoxide phosphoric acid (meta)acrylate, phynyl(meta)acrylate, EO denatured phosphoric acid (meta)acrylate, EO denatured phosphoric acid (meta)acrylate, phthalic acid (meta)acrylate, polyethylene glycol 200 (meta)acrylate, polyethylene glycol 400 (meta)acrylate, polyethylene glycol 600 (meta)acrylate, stearyl(meta)acrylate, EO denatured succinate(meta)acrylate, tetraphloroprophyl(meta)acrylate, tetrahydrofurfuryl(meta)acrylate, vinyl acetate, and N-vinylcaprolactam.
Multifunctional:
(Meta)acrylide isocyanurate, bis(acryloxyneopentyl glycol) adipate, EO denatured bis phenol A di (meta)acrylate, EO denatured bis phenol S di (meta)acrylate, EO denatured bis phenol F di (meta)acrylate, 1,4-butanediol di(meta)acrylate, 1,3-butylene glycol di(meta)acrylate, dicyclopentanyl di(meta)acrylate, diethylene glycol(meta)acrylate, dipenta erythritol hexa(meta)acrylate, dipenta erythritolmonohydroxy penta(meta)acrylate, alkyl denatured dipenta erythritol penta(meta)acrylate, alkyl denatured dipenta erythritol tetra(meta)acrylate, alkyl denatured dipenta erythritol tri(meta)acrylate, caprolactone denatured dipenta erythritol hexa(meta)acrylate, ditrimethylol propane tetra(meta)acrylate, ethylene glycol di(meta)acrylate, ECH denatured glycerol tri(meta)acrylate, 1,6-hexanediol di(meta)acrylate, long chain aliphatic series di(meta)acrylate, methoxide cyclohexyl di(meta)acrylate, neopentyl glycol di(meta)acrylate, hydroxy pivalate neopentyl glycol di(meta)acrylate, pentaerythritol tri(meta)acrylate, pentaerythritol tetra(meta)acrylate, stearic acid denatured pentaerythritol di(meta)acrylate, EO denatured phosphoric acid di(meta)acrylate, polyethylene glycol di(meta)acrylate, polypropylene glycol di(meta)acrylate, tetraethylene glycol di(meta)acrylate, triethylene glycol di(meta)acrylate, trimethylolpropane tri(meta)acrylate, EO denatured trimethylolpropane tri(meta)acrylate, PO denatured trimethylolpropane tri(meta)acrylate, tris(meta)achroxyethyl isocyanurate, caprolactone denatured tris(meta)achroxyethyl isocyanurate monofunctional, and multifunctional monomer. The composition can be composed by properly selecting and mixing those materials in accordance with performance required.
Further, oligomer may also be added thereto in terms of adjusting the viscosity and improving the property. Moreover, the curing composition may be, when used, if within a range that does not deteriorate the performance thereof, as the necessity may arise, properly mixed with known additives such as thermoplastic high polymer, a slip agent, a leveling agent, an antioxidant, an ultraviolet absorbent, a polymerization inhibitor, a silane coupling agent, an inorganic filler, an organic filler, an inorganic filler subjected to a surface organizing treatment, and so on.
Reaction Initiator:
When a wavelength of the laser beam used for reading the optical disc is within a range of, e.g., 380 nm through 500 nm, it is preferable to properly use a light polymerization initiator by properly select a type and a usage amount of this initiator so that a light transmissive layer sufficiently transmits the laser beam required for reading. In this case, it is particularly preferable to employ such a short wavelength photosensitive light polymerization initiator that the light transmissive layer obtained does not absorb blue-violet laser beams.
Given as specific examples of the short wavelength photosensitive light polymerization initiator are, for instance, benzophenone, 2,4,6-trimethyl benzophenone, methylorthobenzoyl benzoate, 4-phenyl benzophenone, diethoxyacetophenone, 2-hydroxy-2methyl-1-phenylpropaci-1-one, benzyldimethylketal, 1-hydroxycyclohexyl-phenylketone, benzoin methylether, benzoin ethylether, benzoin isoprophylether, benzoin isobutylether, methylbenzoilformate, and so forth. These materials can be used as one single body or a combination of two or more materials.
Further, in the composition of the ultraviolet curing resin to be used, the usage amount of the light polymerization initiator is not particularly limited, however, it is preferable to add the light polymerization initiator within a range of 0.0001 through 5 mass part for 100 mass part as a total amount of the resin component. It is also preferable that the usage amount thereof is equal to or larger than 0.001 mass part in terms of the curing property, and a range of being equal to or smaller than 3 mass part is more preferable in terms of a deep portion curing property and hard xanthic denaturation.
Moreover, Core9930a made by cores Co., Ltd. was used as a measuring device for measuring the film thickness of the resin, wherein the film thickness was measured at 1140 points at an interval of 2 mm in a range of 22 mm through 58 mm in the radial direction and at an interval of 6 degrees in the peripheral direction. A measurement principle of this measuring device is a method of acquiring the film thickness by calculation from a deviation amount between a surface reflection and an undersurface reflection.
The best mode for carrying out the present invention has been discussed so far, however, the present invention is not limited to what has been described above and can be modified in a variety of forms within the scope of the technical concept of the present invention. For example, the optical discs including three or more spacer layers can be similarly manufactured by the manufacturing method of the present invention. Further, electron beams, etc. other than the ultraviolet rays may also be available as the energy beams according to the present invention.
Note that the [information layer] includes other categories of layers such as the recording layer and a reflection layer, a dielectric layer and so forth. The recording layer is made of a phase-change material, a magneto-optic material and so on in the case of a rewritable recording medium (Re-writable), and is made of the phase-change material and an organic material in the case of a write-once read-many recording medium (Recordable). Moreover, in the case of a read-only medium (ROM (Read Only Memory)), a reflection layer provided on the rugged portion (pits) formed on the substrate or on the resin serves as the information layer.
Number | Date | Country | Kind |
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JP2003-343125 | Oct 2003 | JP | national |