JP2004062990A - Optical disc manufacturing method - Google Patents

Abstract

An object of the present invention is to suppress a change with time without causing an increase in manufacturing cost in a bonded optical disk.
A first substrate and a second substrate are injection-molded to form an information signal portion on at least one main surface of at least one of the first substrate and the second substrate. In a method of manufacturing an optical disc in which one principal surface of the first substrate 1 and one principal surface of the second substrate 11 are bonded to face each other, molding conditions for injection molding the first substrate 1 and the second substrate 11 Thus, the shrinkage ratio of the first substrate 1 and the second substrate 11 is controlled, and the change with time of the warp of the optical disk is suppressed.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a laminated optical disk.
[0002]
[Prior art]
2. Description of the Related Art In recent years, bonded optical discs such as DVDs (Digital Versatile Discs) have become widespread. This bonded optical disk has an advantage that a higher recording density can be achieved as compared with a single-plate optical disk such as a CD (Compact Disc).
[0003]
FIG. 7 is a cross-sectional view showing a schematic configuration of a conventional bonded optical disk. FIG. 8 is an enlarged sectional view showing the configuration of a conventional bonded optical disk. As shown in FIG. 7, this optical disk is configured by bonding a first disk substrate 100 and a second disk substrate 110 for supporting the first disk substrate 100 with an adhesive layer 120. . In the first disk substrate 100, as shown in FIG. 7, a dielectric layer 102, a recording layer 103, a dielectric layer 104, a reflective film 105, and a protective layer 106 are sequentially formed on one main surface of the first substrate 101. It is constituted by doing. On the other hand, in the second disk substrate 110, a reflective film 112 and a protective layer 113 are sequentially formed on one main surface of the second substrate 111, and a label printing layer is formed on the other main surface of the second substrate 111. It is constituted by.
[0004]
In this bonded optical disk, it is required that the warpage of the optical disk be kept smaller than that of an optical disk such as a CD. For this reason, it has been studied how to suppress the temporal change of the warpage of the bonded optical disk.
[0005]
Conventionally, in order to suppress the change over time of the warp in the bonded optical disk, the first substrate 101 and the second substrate 111 are required to maintain similar characteristics (warp, distortion, shrinkage, etc.) with each other. Is considered preferable. For this reason, in the substrate forming step of the bonded optical disk, the first substrate 101 and the second substrate 111 are manufactured under the same conditions using the same molding machine and mold, or It is general that the first substrate 101 and the second substrate 111 are manufactured under the same conditions using a mold having a cavity.
[0006]
[Problems to be solved by the invention]
However, as described above, even when the characteristics of the first substrate 101 and the second substrate 111 are the same, it is difficult to suppress the temporal change of the bonded optical disk. In fact, the accelerated test (environmental test conducted in a high-temperature and high-humidity environment) for observing the aging of the bonded optical disk is performed on the bonded optical disk to confirm the aging of the optical disk. Can be.
[0007]
According to the knowledge of the present inventor, one of the factors of the temporal change of the optical disk is curing shrinkage of the label print layer 114. This is for the following reason.
[0008]
That is, the label print layer 114 is formed by irradiating the ultraviolet curable ink applied on the second substrate 111 with ultraviolet light and curing and drying the ultraviolet curable ink. It is limited to the vicinity. That is, at the time of manufacturing the optical disk, the inside of the label print layer 114 is not completely cured. When the label print layer 114 in such a state cures and contracts in a high-temperature and high-humidity environment in an accelerated test, the optical disk warps. The reason that the ultraviolet rays cannot reach the inside of the label printing layer 114 is that the ultraviolet curing ink used for forming the label printing layer 114 is usually an ultraviolet curing ink containing a pigment or the like, that is, a colored opaque ultraviolet curing ink. Because it is.
[0009]
According to the knowledge of the present inventor, as factors of the temporal change of the optical disk, (1) in addition to (1) curing shrinkage of the label printing layer 114, (2) curing shrinkage of the protective layers 106 and 113 made of an ultraviolet curable resin, 3) curing shrinkage of the adhesive layer 120 made of a cationically polymerized ultraviolet curable resin; (4) drastic changes in ultraviolet irradiation conditions (light source, wavelength, output, temperature, etc.); and (5) others.
[0010]
Therefore, in order to suppress the change over time of the warpage of the optical disk, a warp compensation layer for keeping the stress of each substrate parallel to one of the first disk substrate 100 and the second disk substrate 110 is provided. Has been proposed. This warpage compensation layer is formed by applying and curing an ultraviolet curable resin on the substrate, or by forming an Al film on the substrate by sputtering or the like.
[0011]
However, in the method of providing the warp compensation layer, it is necessary to further add a step of forming the compensation layer to the conventional disk manufacturing method. Therefore, this method causes a problem that the manufacturing cost of the optical disk is increased and the production efficiency of the optical disk is reduced.
[0012]
Accordingly, an object of the present invention is to provide a method of manufacturing an optical disc which can suppress a change in warpage with time without causing an increase in manufacturing cost in a bonded optical disc.
[0013]
It is another object of the present invention to provide a method of manufacturing an optical disc which can suppress a change with time in warpage without causing a decrease in production efficiency.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the invention of the present application is to form an information signal portion on at least one principal surface of at least one of the first substrate and the second substrate by injection molding the first substrate and the second substrate. A method for manufacturing an optical disc, wherein one principal surface of a first substrate and one principal surface of a second substrate are bonded so as to face each other;
The shrinkage ratios of the first substrate and the second substrate are controlled by molding conditions at the time of injection molding the first substrate and the second substrate, so that a change over time of the warp of the optical disk is suppressed. This is a method for manufacturing an optical disk.
[0015]
As described above, according to the present invention, the shrinkage ratio of the first substrate and the second substrate is controlled by the molding conditions when the first substrate and the second substrate are injection-molded, and the warpage of the optical disk is controlled. In order to suppress changes over time, the mechanical properties of the optical disk can be improved only by controlling the shrinkage rates of the first substrate and the second substrate. That is, it is possible to suppress the change with time of the warp of the optical disk without providing a compensation layer on the optical disk. Further, it is possible to suppress the change with time of the warp of the optical disk without increasing the manufacturing cost of the optical disk.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for manufacturing the optical disc according to the first embodiment of the present invention will be described with reference to the drawings. 1 to 3 show a method of manufacturing the optical disc according to the first embodiment.
[0017]
First, as shown in FIG. 1A and FIG. 2A, the first substrate 1 and the second substrate 11 each having one main surface having irregularities are formed by injection molding. At this time, the ratio D1 / S1 of the contraction ratio S1 of the first substrate to the contraction ratio D1 of the second substrate is within a predetermined range, for example, 0.1 ≦ D1 / S1 ≦ 0.8 or 1.2 ≦ D1 /. The molding conditions (for example, mold temperature) of the first substrate and the second substrate are selected so as to satisfy S1 ≦ 3.0.
[0018]
FIG. 4 shows the relationship between the mold temperature of the injection molding apparatus and the contraction amount of the substrate. From FIG. 4, it can be seen that the amount of shrinkage of the substrate can be regulated by controlling the mold temperature. Therefore, by controlling the mold temperature, the ratio D1 / S1 of the shrinkage ratio S1 of the first substrate to the shrinkage ratio D1 of the second substrate is set to a predetermined range, for example, 0.1 ≦ S ≦ 0.8. Alternatively, it is possible to satisfy the range of 1.2 ≦ S ≦ 3.0.
[0019]
As a material of the first substrate 1 and the second substrate 11, a low water-absorbing resin such as polycarbonate (PC) or a cycloolefin polymer (for example, ZEONEX (registered trademark)) is used. The thickness of the substrate 1 and the substrate 2 is, for example, 0.6 mm.
[0020]
Next, as shown in FIG. 1B, a dielectric layer 2 is formed on one main surface of the first substrate 1. The dielectric layer 2 is made of, for example, ZnSSiO ₂ . The thickness of the dielectric layer 2 is, for example, 60 nm when the optical disk is a DVD-RW (Digital Versatile Disc-ReWritable), and is, for example, 80 nm when the optical disk is a DVD + RW.
[0021]
Next, as shown in FIG. 1C, a recording layer 3 is formed on the dielectric layer 2. The recording layer 3 is, for example, GeSbTe when the optical disk is a DVD-RW, and is, for example, GeInSbTe when the optical disk is a DVD + RW. The thickness of the recording layer 3 is, for example, 10 nm when the optical disk is a DVD-RW, and is, for example, 20 nm when the optical disk is a DVD + RW.
[0022]
Next, as shown in FIG. 1D, a dielectric layer 4 is formed on the recording layer 3. This dielectric layer 4 is made of, for example, ZnSSiO ₂ . The thickness of the dielectric layer 2 is, for example, 20 nm.
Next, as shown in FIG. 1E, a reflection film 5 is formed on the dielectric layer 4. The reflection film 5 is made of, for example, AlCu. The thickness of the reflection film 5 is, for example, 140 nm.
[0024]
Next, as shown in FIG. 1F, an ultraviolet curable resin is uniformly applied on the reflective film 5 and irradiated with ultraviolet light. Thereby, the ultraviolet curable resin is cured, and the protective layer 6 is formed. The thickness of the protective layer 16 is, for example, 10 μm when the optical disk is a DVD-RW, and is, for example, 15 μm when the optical disk is a DVD + RW.
[0025]
Next, as shown in FIG. 2B, a reflection film 12 is formed on the second substrate 11. The reflection film 12 is made of, for example, AlCu. The thickness of the reflection film 12 is, for example, 140 nm.
[0026]
Next, as shown in FIG. 2C, an ultraviolet curable resin is uniformly applied on the reflective film 12 and irradiated with ultraviolet light. Thereby, the ultraviolet curable resin is cured, and the protective layer 13 is formed. The thickness of the protective layer 13 is, for example, 10 μm when the optical disk is a DVD-RW, and is, for example, 15 μm when the optical disk is a DVD + RW.
[0027]
Next, as shown in FIG. 3A, an ultraviolet curable resin serving as an adhesive layer 20 is applied on one of the protective layer 6 of the first substrate 1 and the protective layer 13 of the second substrate 11, And the second substrate 11 are bonded so that the protective layer 6 and the protective layer 13 face each other. Then, after adjusting the thickness of the ultraviolet curable resin, ultraviolet light is irradiated. Thereby, the ultraviolet curable resin is cured, and the adhesive layer 20 is formed.
[0028]
Next, as shown in FIG. 3B, an ultraviolet curable ink is applied to the other main surface of the second substrate 11 and irradiated with ultraviolet light. Thereby, the ultraviolet curable ink is cured, and the label print layer 14 is formed. The label print layer 14 is for displaying a title, a logo design, and the like.
[0029]
In addition, the inventor examined the range of the ratio D1 / S1 between the shrinkage ratio S1 of the first substrate 1 and the shrinkage ratio D1 of the second substrate 11 in order to effectively suppress the change over time of the warpage of the disk. The details of this study are described below.
[0030]
First, a plurality of optical disks having different ratios D1 / S1 between the shrinkage ratio S1 of the first substrate 1 and the shrinkage ratio D1 of the second substrate 11 were manufactured. Then, for each of the manufactured optical disks, the R-skew (warpage) at a radius of 58 mm was measured.
[0031]
Next, an acceleration test (environmental test) of maintaining the optical disk in an environment of a temperature of 70 ° C. and a humidity of 50% for 96 hours was performed. Thereafter, the R-Skew (warpage) at a radius of 58 mm was measured for each of the optical disks on which the acceleration test was performed.
[0032]
Below, the amount of change (time-dependent change) of R-Skew by an acceleration test is shown by a graph. Here, for the sake of convenience, the R-Skew of the optical disk having D1 / S1 = 1.0 (shrinkage ratio S1 of the first substrate 1 = 0.0245%, shrinkage ratio D1 of the second substrate = 0.0245%) is used. (Time-dependent change) and the R- of the optical disk having D1 / S1 = 0.33 (shrinkage ratio S1 of first substrate 1 = 0.0245%, shrinkage ratio D2 of second substrate D1 = 0.00817%). Skew change (time-dependent change).
[0033]
FIG. 5 shows a change (time-dependent change) of R-Skew of the optical disk of D1 / S1 = 1.0. In this optical disc, there was a change of +0.5 [deg] at a radius of 58 mm.
[0034]
From FIG. 5, when the shrinkage ratio S1 of the first substrate 1 and the shrinkage ratio D1 of the second substrate are set to the same value, that is, when D1 / S1 = 1.0, the change with time is observed. It cannot be understood that the value of “” cannot be reduced.
[0035]
FIG. 6 shows a change (time-dependent change) of R-Skew of the optical disk of D1 / S1 = 0.33. This optical disc had a variation of -0.018 [deg] at a radius of 58 mm.
[0036]
As shown in FIG. 6, when the contraction ratio S1 of the first substrate 1 and the contraction ratio D1 of the second substrate are set to different values, that is, when D1 / S1 = 0.33, the change with time is observed. Is small.
[0037]
The present inventor has studied based on the measurement results shown in FIGS. 5 and 6 and the measurement results not shown in the drawings, and as a result, the following has been found. That is, the ratio D1 / S1 of the contraction ratio S1 of the first substrate 1 to the contraction ratio D1 of the second substrate 11 is 0.1 ≦ D1 / S1 ≦ 0.8 or 1.2 ≦ D1 / S1 ≦ 3. By satisfying the range of 0.0, it was found that R-Skew (change over time) can be effectively suppressed.
[0038]
According to the first embodiment of the present invention, the following effects can be obtained. Controlling the contraction ratios of the first substrate 11 and the second substrate 21 such that the ratio D1 / S1 of the contraction ratio S1 of the first substrate to the contraction ratio D1 of the second substrate satisfies a predetermined range; In order to suppress the warp of the optical disk, the mechanical properties of the optical disk can be improved only by controlling the contraction rates of the first substrate 1 and the second substrate 11. In other words, a step of forming a warp compensation layer (protective film, Al film) for forcibly correcting the deformation of the disk can be omitted. Therefore, the manufacturing cost of the optical disc can be reduced.
[0039]
Further, it is possible to provide an optical disk having mechanical stability even in a high-temperature and high-humidity environment without increasing the manufacturing cost of the optical disk.
[0040]
Furthermore, it is possible to manufacture a bonded optical disk having high mechanical properties without being restricted by the film forming conditions and printing conditions.
[0041]
Next, a method for manufacturing an optical disk according to the second embodiment of the present invention will be described.
[0042]
In the first embodiment described above, at the time of injection molding of the first substrate 1 and the second substrate 11, the ratio D1 / D1 of the contraction ratio S1 of the first substrate 1 and the contraction ratio D1 of the second substrate 11 is used. Although the case where the molding conditions of the first substrate 1 and the second substrate 11 are selected so that S1 falls within a predetermined range has been described, in the second embodiment of the present invention, the contraction of the first substrate 1 is performed. The molding conditions for the first substrate 1 and the second substrate 11 are selected so that the ratio S1 and the contraction ratio D1 of the second substrate 11 satisfy the following relationship.
S1 + S2 = D1 + D2
Here, S2 is a contraction rate of another factor in the first substrate 1, and D2 is a contraction rate of another factor in the second substrate 11.
[0043]
The shrinkage ratio S2 of other factors in the first substrate 1 is
1. 1. Hardening shrinkage of protective layer 11 Cure shrinkage of the adhesive layer 20 (for example, shrinkage due to polymerization of a cationic polymerization UV-curable adhesive)
3. 3. Significant changes in UV irradiation conditions (eg, light source, wavelength, power, temperature, etc.) The rate of shrinkage caused by any other factor.
[0044]
The shrinkage ratio D2 of the other factors in the second substrate 11 is
1. 1. Curing shrinkage of the label printing layer 14 2. Hardening shrinkage of the protective layer 13 Cure shrinkage of the adhesive layer 20 (shrinkage due to polymerization of the cationic polymerization UV-curable adhesive)
4. 4. Significant changes in UV irradiation conditions (eg, light source, wavelength, power, temperature, etc.) The rate of shrinkage caused by any other factor.
[0045]
The shrinkage ratio S2 of the first substrate 1 due to other factors and the shrinkage ratio D2 of the second substrate 11 due to other factors are known values when the optical disk is manufactured.
[0046]
The other points are the same as those of the above-described first embodiment, and a description thereof will not be repeated.
[0047]
According to the second embodiment of the present invention, the same effects as those of the first embodiment can be obtained.
[0048]
Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications based on the technical idea of the present invention are possible.
[0049]
For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as needed.
[0050]
Further, the present invention may be applied to a disk having a high density and asymmetric structure such as a SACD (Super Audio CD) hybrid disk.
[0051]
Further, the present invention may be applied to a read-only optical disk (for example, DVD-ROM) and a write-once optical disk (for example, DVD-R).
[0052]
Further, in the above-described embodiment, an example has been described in which the shrinkage ratio of the first substrate 1 and the second substrate 11 is controlled to suppress the change with time of the warp of the optical disk. By controlling the shrinkage ratio of the second substrate 11, warpage generated during the manufacture of the optical disc may be suppressed.
[0053]
【The invention's effect】
As described above, according to the present invention, the shrinkage ratio of the first substrate and the second substrate is controlled by the molding conditions at the time of injection molding the first substrate and the second substrate, and the warpage of the optical disc is controlled. In order to suppress the change with time, the mechanical properties of the optical disc can be improved only by controlling the shrinkage rates of the first substrate and the second substrate. That is, warpage of the optical disk can be suppressed without providing a compensation layer on the optical disk. Further, the warpage of the optical disk can be suppressed without increasing the manufacturing cost of the optical disk.
[Brief description of the drawings]
FIG. 1 is a sectional view illustrating a method for manufacturing an optical disc according to a first embodiment of the present invention.
FIG. 2 is a sectional view showing the method of manufacturing the optical disc according to the first embodiment of the present invention.
FIG. 3 is a sectional view showing the method of manufacturing the optical disc according to the first embodiment of the present invention.
FIG. 4 is a graph showing a relationship between a mold temperature of an injection molding apparatus and a contraction amount of a substrate.
FIG. 5 is a graph showing the amount of change in the warpage of an optical disk with D / S = 1.0, which is caused by an acceleration test.
FIG. 6 is a graph showing an amount of change in warpage of an optical disk having D / S = 0.33, which is caused by an acceleration test.
FIG. 7 is a schematic sectional view showing a configuration of a conventional optical disk.
FIG. 8 is a cross-sectional view showing a configuration of a conventional optical disc.
[Explanation of symbols]
1, 101: first substrate, 2: dielectric layer, 3: recording layer, 4: dielectric layer, 5: reflective layer, 6: protective layer, 11, 111: second substrate, 12: reflective layer, 13: protective layer, 14: label printing layer, 20, 120: adhesive layer

Claims (5)

Injection molding a first substrate and a second substrate, forming an information signal portion on at least one main surface of the first substrate and the second substrate, and forming an information signal portion on one main surface of the first substrate In the method for manufacturing an optical disk, wherein the optical disk is bonded so that one main surface of the second substrate is opposed to the optical disk,
The shrinkage ratio of the first substrate and the second substrate is controlled by molding conditions when the first substrate and the second substrate are injection-molded, so that a change with time of the warp of the optical disk is suppressed. A method for manufacturing an optical disk, characterized by comprising: When the contraction ratio of the first substrate is S1 and the contraction ratio of the second substrate is D1, the contraction of the first substrate and the second substrate is controlled so that D1 / S1 satisfies a predetermined range. 2. The method according to claim 1, wherein the rate is controlled. The shrinkage ratio of the first substrate and the second substrate is controlled such that D1 / S1 satisfies the range of 0.1 ≦ D1 / S1 ≦ 0.8 or 1.2 ≦ D1 / S1 ≦ 3.0. 2. The method for manufacturing an optical disk according to claim 1, wherein: 2. The method according to claim 1, wherein the molding condition is a mold temperature of an injection molding apparatus. When the shrinkage factor of the other factor in the first substrate is S2 and the shrinkage factor of the other factor in the second substrate is D2,
S1 + S2 = D1 + D2
2. The method of manufacturing an optical disk according to claim 1, wherein the contraction ratio of the first substrate and the contraction ratio of the second substrate are controlled so as to satisfy the following relationship.

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