JP2004039250A - Manufacturing method of optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical disk having a multilayer structure and superior in precision and productivity. <P>SOLUTION: After lapping a substrate 4 and a stamper 21 on both sides of radiation cured resin 22, the substrate 4 and the stamper 21 are rotated at high velocities (Fig.B). Then, as shown in the figure, the radiation cured resin 22 applied to the central section spreads to a periphery by centrifugal force. Furthermore, as shown in (Fig.C), excessive radiation cured resin 22 is shaken off to the outside and removed from the end surfaces of the substrate 4 and the stamper 21. A transparent resin layer which does not have mixed air bubble at uniform film thickness can be formed in a short-time manufacturing process by a uniform outward force in a horizontal direction by the centrifugal force of high-speed rotation. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an optical information recording medium and a method for manufacturing the same, and in particular, has a radiation-curable resin layer on a substrate made of a light-transmitting material, and forms an uneven shape on the radiation-curable resin layer to form an information recording surface. And a method for manufacturing an optical information recording medium.

2. Description of the Related Art Conventionally, there has been an optical information recording medium on which optically readable information is recorded and information recorded using a laser beam spot is read. In particular, in recent years, compact discs (hereinafter referred to as CDs) have been known. And optical disks such as CD-ROMs have become remarkably widespread. The above-mentioned CD-ROMs are not only for computers but also recently, multi-functional game CD-ROMs have appeared, and the switching from computers, game co-magnetic disks (floppy disks) or ROM cartridges to CDs is progressing.

高 密度 Also, a high-density optical disk has been proposed in which information is recorded at a high density by recording pits smaller than a CD with a narrower track pitch, and its use in multimedia other than movies has been whispered. Further, while the CD has a single-layer information recording surface on which a signal is recorded only on a certain surface on the substrate, a transparent resin layer made of a radiation-curable resin is laminated on the substrate. An optical disc having a multilayer structure having a plurality of information recording surfaces in the thickness direction has been proposed.

Hereinafter, an optical disk having the above-mentioned multilayer structure will be described with reference to FIG. FIG. 1 is a diagram showing the structure of an optical disk having a multilayer structure. FIG. 2 shows a part of a cross-sectional view of the optical disk in the track direction. For the sake of simplicity, an optical disk having a multilayer structure described below having two information recording surfaces will be described.

As shown in FIG. 1, a conventional multi-layered optical disk (hereinafter simply referred to as an optical disk) 1 has a first reflective layer 5, a transparent resin layer 6, and a second reflective layer 7, a protective film 8 is laminated in this order. An uneven pit 4A according to information is formed on the substrate 4, and an uneven pit 4B according to information is formed on the transparent resin layer 6. That is, the optical disc 1 has two information recording layers in the thickness direction of the substrate 4, the pit 4A forming surface of the light transmitting substrate 4 is the first information recording surface 2, and the transparent The pit 4B forming surface of the resin layer 6 is the second information recording surface 3.

The first reflective layer 5 formed between the first information recording surface 2 and the second information recording surface 3 has a certain degree so that light can be incident on or reflected from the second information recording surface 3. Of a material having a light transmittance of Hereinafter, the first reflective layer 5 will be described as a translucent reflective layer 5, and the second reflective layer 7 will be described as a reflective layer 7. When forming three or more information recording surfaces, a second transparent resin layer is formed on the reflective layer 7 on the transparent resin layer 6, and pits are formed on the second transparent resin layer. Thus, the third information recording surface is formed, and the fourth and subsequent information recording surfaces are similarly configured.

(4) A reproducing laser beam for reading information recorded on each of the information recording surfaces is incident from below the substrate 4. Here, the distance between the information recording surfaces of the optical disk 1 is as narrow as several tens of microns, but the optical pickup of the reproducing apparatus correctly recognizes the distance and focuses on the desired information recording surface, thereby recording each information. Surface information is read. As described above, the optical disc is provided with two or more information recording surfaces in the thickness direction of the substrate 4 to form a multi-layer structure, so that a larger amount of information can be recorded than the conventional single-layer optical disc. It becomes.

Next, a conventional method of manufacturing the optical disc 1 having the above-described configuration will be described with reference to FIG.
Note that, for simplification of description, the description will be made as a double-layer disc. First, as shown in FIG. 1A, an optical disc substrate 4 having pits 4A on its surface is formed by, for example, injection molding using a stamper (not shown) having a pattern opposite to the pits 4A on the first information recording surface. . Next, as shown in FIG. 3B, a translucent reflective layer 5 is formed on the surface of the substrate 4 on which the pits 4A are formed by a film forming method such as sputtering, ion plating, CVD, vacuum evaporation, or spin coating. Form. The translucent reflective layer 5 is a reflective layer having a certain light transmittance as described above.

Next, the second information recording surface 3 is formed on the translucent reflective layer 5. The second information recording surface 3 is formed by a conventionally known 2P method. That is, as shown in FIG. 3C, a stamper 21 having a concave and convex shape 21A having a reverse pattern of the pits 4B on the second information recording surface 3 is prepared, and an ultraviolet curing is performed on the translucent reflective layer 5 of the substrate 4. The resin 22 is dropped, and then the signal surface of the stamper 21 is pressed onto the substrate 4 on which the ultraviolet curable resin 22 has been dropped, thereby extending the ultraviolet curable resin 22 to a uniform thickness. When the stamper 21 is pressed, the resin overflowing from the outer peripheral portion of the substrate 4 is sucked by the nozzle 23 as shown in FIG. Then, as shown in FIG. 4E, the stamper 21 is peeled off by irradiating ultraviolet rays (radiation) from the substrate 4 side to cure the ultraviolet curing resin 22, and as shown in FIG. An optical disk substrate on which pits 4B serving as the information recording surface 3 are formed is obtained. Finally, a reflective layer 7 is formed on the second information recording surface 3 by depositing aluminum, gold, or the like by vacuum deposition such as sputtering or vacuum deposition, and a protective film 8 is further formed on the reflective layer 7. Is formed and a label (not shown) is printed on the protective film 8 to complete an optical disc having a multilayer structure as shown in FIG.

By the way, in the above-described optical disk having a multilayer structure, it is necessary to very strictly manage the interval between the information recording surfaces due to the restriction on the principle of reproduction. For example, with respect to the thickness of the transparent resin layer of 40 μm, only a variation of about ± 3 μm is allowed. However, in the above-described 2P method, even if the accuracy of the apparatus is improved, the limit is about ± 5 μm. Further, the 2P method has a low productivity, and it takes about two minutes per surface to form an information recording surface after the second information recording surface. It is possible to increase the molding speed by increasing the pressure or increasing the amount of resin dripping, but the accuracy of the film thickness is reduced, bubbles are involved, defects are generated, and the overflow is insufficiently absorbed. And the like. That is, when an optical disk having the above-mentioned multilayer structure is manufactured by using a conventionally known manufacturing method, there is a trade-off between accuracy and productivity.

In the case of the above-described manufacturing method, a silicon oxide film (SiOx), a silicon oxide film-based alloy, a silicon nitride film (SiNx), a silicon nitride film-based alloy, or the like is generally used as the material of the translucent reflective layer 5. However, these materials have poor adhesion to the transparent resin layer 6 made of an ultraviolet curable resin, and have a problem that cracks occur in an environmental load test or peel off in extreme cases. It is easy to introduce a special functional group in order to give the resin an adhesive force. However, if the semi-transparent reflective layer 5 is designed to have an adhesive force, an adhesive force is generated even for the stamper (nickel material). However, a disadvantage that peeling becomes difficult occurs newly. Further, it is very difficult to design an ideal resin which adheres to the translucent reflection layer 5 and does not adhere to nickel, and does not actually exist.

Accordingly, the present invention has been made in view of the above points, and an object of the present invention is to provide a method of manufacturing an optical disk having a multilayer structure excellent in accuracy, productivity, and reliability.

According to a first aspect of the present invention, a transparent resin layer having a thickness of 35 to 50 μm and a variation of the thickness of about ± 3 μm is provided between the first information recording surface and the second information recording surface. In the method for manufacturing an inserted optical information recording medium, the transparent resin layer is formed by dropping a radiation-curable resin having a viscosity of 80 to 1100 cp on the first information recording surface formed on the substrate surface, and then rotating at a rotation speed of 750 to 750. An object of the present invention is to provide a method of manufacturing an optical information recording medium, wherein the optical information recording medium is formed by rotating at 1500 rpm and then curing by irradiating the radiation-curable resin with radiation.
A second aspect of the present invention is to provide a method for manufacturing an optical information recording medium according to claim 1, wherein the radiation-curable resin is an ultraviolet-curable resin.

As described above, according to the method for manufacturing an optical information recording medium of the present invention, a radiation curable resin layer is laminated on a substrate made of a light transmissive material, and a guide groove or pit is formed on the radiation curable resin layer. In a method of manufacturing an optical information recording medium having an information recording surface for recording information by forming an uneven shape, a substrate and a stamper are opposed to each other with a radiation-curable resin therebetween, and then the substrate and the stamper are separated. Since it is rotated at a high speed in the superposed state, a radiation-curable resin layer having a uniform film thickness and free from bubbles can be formed in a short manufacturing process.

Further, a semi-transparent reflective layer and a radiation-curable resin layer are sequentially laminated on a substrate made of a light-transmitting material, and information is recorded by forming an uneven shape by guide grooves or pits on the radiation-curable resin layer. In the optical information recording medium having the information recording surface of the above, since a primer film was formed between the translucent reflective layer and the radiation-curable resin layer, cracks were formed in the radiation-curable resin layer, or the radiation-curable resin layer was Peeling can be prevented, and the reliability of the optical information recording medium can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, a case will be described in which the multi-layered optical disc 1 having the two information recording surfaces shown in FIG. 1 is manufactured. FIG. 2 is a view for explaining a first embodiment of the method for manufacturing an optical information recording medium according to the present invention. A disk substrate 4 having pits 4A formed on the surface thereof by a molding method such as injection molding is prepared, and a semitransparent reflective layer 5 is formed on the pit-formed surface of the substrate 4 by sputtering, vacuum deposition, ion plating, CVD, or spin coating. A radiation curable resin is applied to the surface of the semi-transparent reflective layer 5 of the substrate 4 or one of the stampers 21 or both surfaces to form a film (transparent substrate made of a light-transmitting material). The process up to the step of superimposing the layer 5 (FIG. 5A) is the same as the above-mentioned conventional method of manufacturing an optical disk having a multilayer structure, but the following steps are different in the present embodiment.

That is, as shown in FIG. 4B, after the substrate 4 and the stamper 21 are overlapped with the radiation-curable resin 22 therebetween, the substrate 4 and the stamper 21 are centered on the center line indicated by the one-dot chain line in FIG. Rotate horizontally at high speed. Then, as shown in the figure, the radiation-cured resin 22 applied to the central portion spreads to the outer peripheral portion due to the centrifugal force of rotation, and further, as shown in FIG. The stamper 21 is removed by being shaken outward from the end face. That is, conventionally, the thickness of the transparent resin layer 6 is controlled by the pressing force and the pressing time of the stamper 21, and the excess radiation-cured resin 22 at the time of pressing is sucked by the nozzle, but in the present embodiment, The thickness of the transparent resin layer 6 is uniformly controlled by the centrifugal force generated by the high-speed rotation, and the excess radiation-cured resin 22 is removed.

Then, after removing the excess radiation-curable resin 22, the rotation of the superposed substrate 4 and the stamper 21 is reduced or stopped, and radiation is irradiated from the substrate 4 side as shown in FIG. When the stamper 21 is peeled off after the hardening of the resin 22, the transparent resin layer 6 having the pits 4B formed on the surface can be formed (FIG. (E)). Finally, a reflective layer 7 and a protective film 8 are sequentially formed to produce a two-layer disc as shown in FIG.

As described above, while the conventional method presses the stamper 21 perpendicular to the substrate surface, in the present embodiment, the substrate 4 and the stamper 21 are both rotated at high speed with respect to the center. Here, the film thickness of the transparent resin layer 6 greatly depends on the pressure at which the stamper 21 is pressed, the pressing time, and the resin viscosity, whereas in the present embodiment, the film thickness of the transparent resin layer 6 greatly depends on the rotational speed of the high-speed rotation and the resin viscosity. Dependent. That is, in the present embodiment, since the pressure for pressing the stamper 21 and the substrate and the pressing time are almost zero, there is no factor of the film thickness variation due to the uneven pressure and the error of the pressing time. Further, in the method according to the present embodiment, the uniform outward force in the horizontal direction due to the centrifugal force causes the thickness of the radiation curable resin 22 to be reduced uniformly, so that a uniform film thickness can be easily obtained. Further, bubbles generated when the substrate 4 and the stamper 21 are superimposed are discharged from the inner circumference to the outer circumference and to the outside of the disk by high-speed rotation. do not do. Further, the processing time is shorter than that of the conventional method, and it can be made in about 30 seconds to 1 minute per one surface.

(4) Since the surplus resin is spun out, the amount of resin accumulated on the end face can be greatly reduced as compared with the above-mentioned conventional manufacturing method. In other words, the end face processing such as blotting is much easier and better. Further, the end face treatment after the high-speed rotation is necessary when the stamper 21 having the same outer diameter as the substrate 4 is used. However, when an experiment was performed using the stamper 21 having various diameters, the end face treatment became completely unnecessary. It turns out that it is also possible. That is when the outer diameter of the stamper 21 is equal to or slightly smaller than the outer diameter of the substrate 4. When such a stamper 21 is used, since the resin does not accumulate on the end face, burrs are not generated when the radiation-curable resin is cured, and a disk having a smooth end face can be obtained. Therefore, the use of such a stamper can significantly improve the productivity of the optical disk. Furthermore, the above-mentioned radiation hardening of the radiation-cured resin by high-speed rotation can be used even when a transparent resin layer is directly laminated on a flat substrate, and pits and guide grooves are formed on the surface of the transparent resin layer. is there. That is, the present invention can be used as a method for manufacturing an optical disk having a multilayer structure or an optical disk having a single-layer structure in which a transparent resin layer is laminated on a flat substrate and the surface of the transparent resin layer is used as a first information recording surface.

By the way, the radiation-curable resin 22 used in the present invention is not particularly limited as long as it can be cured by radiation, such as an ultraviolet-curable resin or an electron-beam curable resin. Viscosity is important. Next, the resin viscosity will be described with reference to FIG.
FIG. 3 is a diagram for explaining the resin viscosity of the radiation-curable resin used in the method for manufacturing an optical information recording medium of the present invention. Specifically, when radiation curable resins having various viscosities are used in the above-described production method of the present invention, how the film thickness of the formed transparent resin layer 6 changes according to the number of rotations of high speed rotation Is shown. In the optical disc having the above-mentioned multilayer structure, it is considered that the thickness of the transparent resin layer 6 is preferably about 35 to 50 μm in terms of signal reproduction. According to FIG. Shows that you can choose from a relatively wide range. On the other hand, focusing on the thickness distribution of the formed radiation-curable resin 22, the ranges of the resin viscosity and the number of rotations are limited to some extent. For example, the film thickness distribution under the condition that the thickness of the formed transparent resin layer 6 is about 40 μm is as shown in Table 1 below.

(4) As described above, the thickness distribution of the transparent resin layer 6 leads to a variation in the output of the reproduction signal. Judging from the above Table 1 the appropriate resin viscosity and rotation speed from such a viewpoint, it can be seen that a resin viscosity of 80 to 1100 cP and a rotation speed of 750 to 1500 rpm are appropriate. Here, it is not clear why the thickness distribution of the formed transparent resin layer 6 changes depending on the conditions of the resin viscosity and the number of rotations, but the rheology of the resin and the steady vibration of the substrate during high-speed rotation are related. It seems to be.

On the other hand, a problem of reliability, which was solved by performing a surface treatment on the substrate 4 and conducting intensive studies, was found to be solved by performing an appropriate primer treatment. Hereinafter, a second embodiment of the present invention relating to the improvement of the reliability of the optical disc will be described. FIG. 4 is a diagram showing the structure of one embodiment of the optical information recording medium of the present invention. As shown in the figure, the optical disc 10 is a primer in which a coupling agent is directly formed between the translucent reflective layer 5 and the transparent resin layer 6 of the optical disc 1 or a thin film of a resin containing the coupling agent is formed. The structure has a film 9.

That is, the translucent reflective layer 5 is generally composed of a silicon oxide film (SiOx), a silicon oxide film-based alloy, a silicon nitride film (SiNx), a silicon nitride film-based alloy, and the like. Since the translucent reflective layer 5 and the transparent resin layer 6 are made of different materials, such as a resin such as an ultraviolet curable resin, the adhesion is poor, and the transparent resin layer 6 is cracked during an environmental load test. Or the transparent resin layer 6 was peeled off. Therefore, in the optical disc 10, a primer film 9 that enhances the adhesion between different materials is formed between the translucent reflective layer 5 and the transparent resin layer 6 to improve the adhesion of the transparent resin layer 6. I have. If such a primer film 9 is provided, the resin constituting the transparent resin layer 6 does not require much adhesive force, and a resin having low adhesive force can be used. Therefore, if the transparent resin layer 6 is formed using such a resin having a low adhesive strength, the adhesiveness with the stamper during formation is reduced, and there is an advantage that the stamper can be easily separated.

The coupling agent of the primer film 9 is specifically selected from a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent, and the curable resin is an ultraviolet curable resin, an electron beam curable resin, a thermosetting resin. It is selected from resins and the like. The thickness of the primer film 9 is suitably in the range of a single molecule (several angstroms) to several μm. The primer film 9 is applied by a vapor coating method or a spin coating method.

As a method of forming the primer film 9 by the vapor coating method, for example, as shown in FIG. 5, the substrate 4 on which the translucent reflective layer 5 is formed is placed in a sealed container 32 in which a coupling agent 31 is placed. It is held horizontally at a distance from the coupling agent 31 so that the reflective layer 5 is on the lower side. Then, when left for a predetermined time, the vapor of the coupling agent 31 is deposited on the surface of the translucent reflection layer 5. Thus, the primer film 9 is formed. On the other hand, in the case of using the spin coating method, the coupling agent itself or a resin containing the coupling agent is dropped on the rotated substrate 4 having the translucent reflective layer, and is applied to a predetermined thickness. It is cured and formed accordingly.

Then, after forming the primer film 9 on the translucent reflection layer 5 in this manner, the primer film 9 is formed on the primer film 9 by using, for example, the optical disk manufacturing method described in the first embodiment (see FIG. 2). Then, the transparent resin layer 6 having an uneven shape formed by pits and guide grooves is formed.

The primer film 9 is provided to increase the adhesion between the radiation resin and the silicon oxide film, the silicon oxide film alloy, the silicon nitride film (SiNx), the silicon nitride film alloy, or the like. It may be provided to enhance the adhesion when the substrate 4 and the transparent resin layer 6 are directly adhered to each other like a layer disc.

Next, the present invention will be described in more detail with reference to specific examples.
<Example 1> Two stampers each having a minimum pit length of 0.451 µm and a track pitch of 0.84 µm were prepared. The first stamper (for injection molding) had an inner diameter of 35.6 mm and an outer diameter of 128 mm, and the second stamper (for 2P molding) had an inner diameter of 30 mm and an outer diameter of 120 mm. Using the first stamper, a 1.2 mm thick substrate 4 was produced by injection molding of polycarbonate. Subsequently, a translucent reflective layer 5 (500 angstrom thick) made of a silicon oxide film (SiOx) was formed thereon by sputtering.

Next, a sealed container with a lid having a diameter of 300 mm and a height of 50 mm is prepared, and as shown in FIG. 5, a silane coupling agent OAP (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is filled to a depth of about 1 cm. The structural formula of the silane coupling agent OAP is shown in the following structural formula 1.

{Circle around (2)} Then, the substrate 4 was left with the translucent reflective layer 5 facing down with a space of 3 cm from the liquid surface of the silane coupling agent OAP, and exposed to the OAP vapor for 5 minutes. As a result of this treatment, the monolayer of the primer film 9 was applied to the surface of the translucent reflective layer 5.

Subsequently, a spinner having a flat turntable having an outer diameter of 120 mm was prepared, and a second stamper was attached to the turntable so as to be flat. On the other hand, an ultraviolet curable resin composition comprising 97 parts of bifunctional acrylate R684 (manufactured by Nippon Kayaku Co., Ltd.) and 3 parts of Darocur 1173 (manufactured by Merck Japan Ltd.) as a photopolymerization initiator was prepared. This UV-curable resin composition had a viscosity of 146 cP at 23 ° C. The structural formula of the acrylate R684 is shown in the following structural formula 2, and the structural formula of the Darocur 1173 is shown in the following structural formula 3.

Next, while rotating the turntable at 30 rpm, the ultraviolet curable resin composition was dropped on the surface of the stamper at a position of 80 mm in diameter over 5 seconds, and the resin was applied in a ring shape. Next, the substrate 4 on which the primer film 9 was formed was dropped so that the rotating ring-shaped resin was opposed to the primer film 9, and the rotation speed was immediately increased to 1000 rpm and held for 15 seconds. By this high-speed rotation, excess ultraviolet curable resin and bubbles mixed into the ultraviolet curable resin were spun out together. Subsequently, the rotation of the turntable was reduced to 100 rpm, and ultraviolet rays were irradiated for 10 seconds in the atmosphere to cure the ultraviolet curable resin. Then, when the substrate was peeled from the stamper, a substrate having the transparent resin layer 6 was obtained. The obtained substrate had no bubbles and no burrs on the outer periphery. When the film thickness of the formed transparent resin layer 6 was measured, it was uniform at 38 μm ± 2 μm. On the other hand, the stamper after peeling also had no burrs on the outer peripheral portion, and had a surface state that could be reused as it was.

(4) Finally, aluminum was formed as a second reflective layer 7 on the surface of the transparent resin layer by sputtering to a thickness of 700 Å. Then, as a protective film 8, SD-1700 (manufactured by Dainippon Ink) was formed into a film having a thickness of 10 μm by spin coating to complete the two-layer disc 1 shown in FIG.

再生 The optical disk was evaluated for reproduction by a disk evaluation machine having a laser wavelength of 635 nm and an objective lens numerical aperture NA of 0.52. By changing the focus position of the pickup, the signals on the information recording surfaces 2 and 3 could be separately observed. At this time, no mutual interference between the two information recording surfaces 2 and 3 was found, and the eye patterns of both the information recording surfaces 2 and 3 were clearly opened, and stable reproduction was possible. The reproduction jitter after passing through the equalizer was 7.5% for the first information recording surface 2 and 6.8% for the second information recording surface 3, which was a practically usable level. In the environmental load test at 55 ° C., 95% RH, and 200 hours, the jitter increased by 0.6% and 0.5%, respectively, but no problem such as the peeling of the transparent resin layer 6 and the peeling of the film occurred. The reliability was confirmed.

<Example 2> The same process as in Example 1 was performed up to the point where the translucent reflective layer 5 (film thickness 500 Å) was formed by sputtering. Next, 5 parts of a silane coupling agent A-174 (manufactured by Nippon Unicar Co., Ltd.), 92 parts of a bifunctional acrylate HDDA (manufactured by Nippon Kayaku Co., Ltd.), and 92 parts of a photopolymerization initiator Darocur 1173 (manufactured by Merck Japan Ltd.) A three part primer solution was prepared. The structural formula of A-174 is shown in the following structural formula 4, and the structural formula of the HDDA is shown in the following structural formula 5.

The above-mentioned primer solution was dropped on the translucent reflection layer 5 using a spinner, and was shaken off at a high speed of 2,000 rpm. Subsequently, the rotation was reduced to 100 rpm, and ultraviolet light was irradiated for 10 seconds in the air to cure the film, thereby forming a primer film 9 (thickness: about 1 μm). Subsequently, the rotation of the spinner was reduced to 30 rpm, and an ultraviolet curable resin composition (23 ° C.) comprising 97 parts of bifunctional acrylate R551 (manufactured by Nippon Kayaku Co., Ltd.) and 3 parts of photopolymerization initiator Darocur 1173 (manufactured by Merck Japan Ltd.) Was applied in a ring shape over a period of 5 seconds to a position having a diameter of 70 mm, and the spinner was stopped. The structural formula of R551 is shown in Structural Formula 6 below.

Subsequently, a spinner having a turntable having an outer diameter of 119 mm was prepared by flatly attaching a second stamper having an inner diameter of 25 mm and an outer diameter of 119 mm. Then, the surface of the second stamper and the surface of the ring-shaped resin applied on the substrate were overlapped so as to face each other, and immediately high-speed rotation at 1500 rpm was performed for 30 seconds. As a result, the excess ultraviolet curable resin and the mixed bubbles spun out together. And finally, the ultra-high speed rotation of 5000 rpm was performed for 1 second, and the rotation was stopped. Subsequently, this set was placed in a nitrogen atmosphere and irradiated with ultraviolet rays for 5 seconds to cure the ultraviolet curable resin. Then, when the substrate was peeled from the stamper, the substrate 4 having the transparent resin layer 6 in which the pits 4B were formed was obtained.
Observation of the formed transparent resin layer 6 revealed no bubbles and no burrs on the outer periphery. Further, when the film thickness of the transparent resin layer 6 was measured, it was uniform at 40 μm ± 3 μm. On the other hand, the stamper after peeling also had no burrs on the outer peripheral portion, and had a surface state that could be reused as it was. Finally, as in Example 1, the reflective layer 7 and the protective film 8 were formed, and the optical disc 1 was completed.

The reason why the ultra-high-speed rotation of 5000 rpm is added after the high-speed rotation of 1500 rpm is that the resin having a high viscosity tends to swell at the outer peripheral edge due to surface tension. The bulge of the outer peripheral end due to the surface tension is not enough to form a burr after the radiation-curable resin is cured, but an extra releasing force is required when the stamper is peeled off. Therefore, the ultrahigh-speed rotation of 4000 to 10000 rpm was applied for a very short time to completely shake off the resin at the end swelling. The reason why the ultraviolet curing is performed in a nitrogen atmosphere is to cut off oxygen in the air and increase the curing speed. However, similar effects can be obtained not only with nitrogen but also with argon, carbon dioxide and the like.

The optical disk produced as described above was evaluated for reproduction by a disk evaluator having a laser wavelength of 635 nm and an objective lens numerical aperture NA of 0.52 in the same manner as in Example 1. As a result, stable reproduction was possible as in Example 1. . The reproduction jitter after passing through the equalizer was 7.7% for the first information recording surface 2 and 7.1% for the second information recording surface 3, which was at a sufficiently practical level. In the environmental load test at 55 ° C., 95% RH, and 200 hours, the jitter increased by 0.8% and 0.7%, respectively. However, no problem such as peeling or peeling of the transparent resin layer 6 occurred and the reliability was improved. The sex was confirmed.

Although two embodiments have been described above, the present invention is not limited to these two embodiments. For example, in the above Examples 1 and 2, an ultraviolet curable resin was used as the radiation curable resin for forming the transparent resin layer 6, but the composition is not limited to the photosensitive unsaturated resin and the photopolymerization initiator. Small amounts of additives such as accelerators, release agents and yellowing inhibitors may be added. As described above, an electron beam curable resin or the like may be used. The resin applied as the primer film 9 is not limited to an ultraviolet curable resin, but may be an electron beam curable resin or a thermosetting resin, and may be diluted with a solvent or the like as necessary. As the coupling material, a titanate coupling agent, an aluminate coupling agent, or the like can be used in addition to the silane coupling agent. Further, after the application of the primer film 9, if necessary, baking may be performed to increase the adhesion.

FIG. 3 is a diagram showing an example of the structure of an optical disc having a multilayer structure manufactured using the present invention and a conventional optical information recording medium. FIG. 4 is a diagram for explaining the first embodiment of the method for manufacturing an optical information recording medium according to the present invention. FIG. 3 is a diagram for explaining the resin viscosity of a radiation-curable resin used in the method for manufacturing an optical information recording medium of the present invention. FIG. 2 is a diagram showing the structure of an embodiment of the optical information recording medium of the present invention. FIG. 7 is a diagram for explaining a second embodiment of the method for manufacturing an optical information recording medium according to the present invention. FIG. 4 is a diagram illustrating an example of a conventional method for manufacturing an optical information recording medium.

Explanation of reference numerals

1,10 Optical disk (optical information recording medium)
2 First information recording surface 3 Second information recording surface 4 Light transmissive substrate 5 Translucent reflective layer 6 Transparent resin layer (radiation cured resin layer)
7 Reflective layer 9 Primer film 21 Stamper 22 Radiation curing resin 31 Primer solution

Claims (2)

An optical information recording medium comprising a transparent resin layer having a thickness of 35 to 50 μm and a thickness variation of about ± 3 μm inserted between the first information recording surface and the second information recording surface. In the manufacturing method,
The transparent resin layer is formed by dropping a radiation-curable resin having a viscosity of 80 to 1100 cp on the first information recording surface formed on the substrate surface, rotating the resin at a rotation speed of 750 to 1500 rpm, and then forming the radiation-cured resin. A method for manufacturing an optical information recording medium, wherein the resin is formed by irradiating a resin with radiation to cure the resin. The method according to claim 1, wherein the radiation-curable resin is an ultraviolet-curable resin.

Images