JP4965200B2 - Optical disc manufacturing method, spin coating method - Google Patents

Description

  The present invention relates to an optical disc manufacturing method and a spin coating method.

Japanese Patent Laid-Open No. 10-289489 JP 2004-95108 A JP 2006-35082 A

Conventionally, in the manufacturing process of an optical disc such as a DVD (Digital Versatile Disc) and a BD (Blu-ray Disc: registered trademark), a spin coating method is known as a method of forming a light transmission layer of a disc substrate. According to this spin coating method, an ultraviolet curable resin is dropped around the center hole of the disk substrate, the disk substrate is rotated to spread the ultraviolet curable resin, and then the ultraviolet curable resin is irradiated with ultraviolet rays. Curing is performed to form a light transmission layer. Here, when the ultraviolet curable resin is spread on the disk substrate, there may be a difference in thickness between the inner periphery and the outer periphery of the disk substrate. In order to avoid such inconvenience, a center cap that is a cap-shaped jig that covers the center hole of the disk substrate is used.
For example, in Patent Documents 1 and 2 described above, a technique for making the inner and outer peripheral thicknesses of the disk substrate uniform by using a center cap at the time of spin coating, and the resin is temporarily cured by irradiating ultraviolet rays to the periphery of the center cap Then, a technique for removing the center cap and shearing is disclosed.

FIG. 9 shows a cross-sectional structure of the manufactured disk substrate 101. The disk substrate 101 is made of, for example, polycarbonate resin, and has a center hole 104 at the center thereof. A protection ring 105 is formed around the center hole 104.
A recording layer 102 is formed on one surface of the disk substrate 101, and a light transmission layer 103 is formed so as to cover the recording layer 102.
The light transmitting layer 103 side is used as a reading surface for information recorded on the recording layer 102, and a read laser 106 by a disk reproducing device is irradiated from the light transmitting layer 103 side when reproducing the manufactured optical disk.

Here, a process of forming the light transmission layer 103 on the disk substrate 101 by spin coating using a center cap will be described with reference to FIGS. 10 (a) to 10 (c) and FIGS. 11 (a) and 11 (b).
At the time of spin coating, a center cap 107 is first placed on the disk substrate 101 so as to cover the protection ring 105 as shown in FIG.
Then, as shown in FIG. 10B, after the ultraviolet curable resin 108 is dropped on the center cap 107, the disk substrate 101 is rotated at a high speed. As a result, the ultraviolet curable resin 108 is spread on the disk substrate 101 as shown in FIG. As shown in FIG. 10C, since the ultraviolet curable resin 108 is viscous, a part of the ultraviolet curable resin 108 remains up to the upper part of the flange portion of the center cap 107.
After the ultraviolet curable resin 108 is spread on the disk substrate 101, the center cap 107 placed on the disk substrate 101 is then removed as shown in FIG.
Then, after removing the center cap 107, the above-described light transmission layer 103 is formed by irradiating the upper surface of the disk substrate 101 with ultraviolet rays and curing the ultraviolet curable resin 108 as shown in FIG. 11B. become.

By the way, there is a problem in removing the center cap 107 after the ultraviolet curable resin 108 is spread on the disk substrate 101 as described above and before the ultraviolet curable resin 108 is cured.
When the center cap 107 is lifted and removed from the disk substrate 101, if the center cap 107 is lifted as shown in FIG. 11A, the outer peripheral end of the center cap 107 lifts the ultraviolet curable resin 108. Become. This is because the ultraviolet curable resin 108 is spread on the disk substrate 101 with a certain thickness, and the ultraviolet curable resin 108 itself is viscous.
Then, the disc substrate 101 after the center cap 107 has been removed is left in a dirty shape because the inner end of the ultraviolet curable resin 108 is disturbed and then cured as shown in FIG. 11B. become.

In the prior art, when removing the center cap 107 in this way, the disturbed trace remains on the disk substrate by disturbing the shape of the ultraviolet curable resin at the end of the center cap 107, The surface on the disk substrate becomes dirty. That is, the quality of the manufactured optical disk is degraded.
Moreover, not only the trace from which the ultraviolet curable resin is removed remains, but also when the center cap is removed, the ultraviolet curable resin that has been spread to have a predetermined thickness is lifted. In addition, air is likely to be mixed and bubbles are likely to enter the ultraviolet curable resin, which also causes deterioration of the disk quality.
Therefore, an object of the present invention is to prevent disorder of the layer structure and mixing of bubbles when spin coating is performed using a center cap.

The optical disk manufacturing method of the present invention includes a substrate molding step for molding an optical disk substrate, and an outer surface of an upper surface of a circular truncated cone-shaped convex portion having an inclined surface formed around the center hole of the optical disk substrate at the center of the optical disk substrate. A frustoconical center cap composed of a flange portion formed with an upper surface having an outer peripheral edge having an outer diameter substantially the same as the diameter and an inclined surface is placed, and a layer structure material dropped onto the center cap is spin coated Forming a layer structure by spreading on an optical disk substrate , wherein in the layer formation step, the layer structure material is a continuous surface of the inclined surface of the annular convex portion and the inclined surface of the flange portion. It is spread on the inclined surface.

The spin coating method of the present invention has an outer diameter substantially coincident with the outer diameter of the upper surface of the truncated cone-shaped annular convex portion having an inclined surface formed at the center of the circular substrate at the center of the circular substrate. By placing a frustoconical center cap formed of a flange portion formed with an upper surface having an outer peripheral edge and an inclined surface , dropping a layer structure material on the center cap, and rotating the circular substrate, The layer structure material is spread on a circular substrate to form a layer structure, and the layer structure material is spread on a continuous inclined surface of the inclined surface of the annular convex portion and the inclined surface of the flange portion. The

That is, in the present invention, the center cap is placed in a positional relationship in which the outer peripheral end portion thereof substantially coincides with the outer peripheral portion of the upper portion of the annular convex portion (for example, a protection ring) formed around the center hole of the optical disc substrate. become.
By doing so, the UV curable resin layer does not remain thick at the outer peripheral edge of the center cap and the contact portion of the disk substrate in a state in which the UV curable resin is spread, so the center cap is removed. The center cap will not lift a lot of viscous UV curable resin.

According to the present invention, an ultraviolet curable resin as a layer structure material is obtained in a state where the outer diameter of the outer peripheral end of the flange portion of the center cap and the outer diameter of the upper surface of the annular convex portion formed on the optical disk substrate are substantially matched. Drop and spin coat. As a result, when removing the center cap, the center cap does not lift up much of the viscous UV curable resin, and therefore, the shape of the UV curable resin spread on the disk substrate is prevented from being disturbed. The That is, the shape of the layer structure (for example, light transmission layer) formed by subsequent curing does not become dirty. Further, since the ultraviolet curable resin is hardly lifted up, bubbles are hardly mixed.
From these things, there exists an effect that a high quality optical disk can be manufactured.

The optical disk manufacturing method of the present invention will be described below. FIG. 1 shows an optical disk manufacturing process according to the embodiment.
The optical disc manufacturing method of this example includes a substrate forming process in step F101, a reflective film forming process in step F102, a light transmission layer forming process in step F103, a hard coat forming process in step F104, a moisture-proof film forming process in step F105, and a step F106. Label printing process.

In the substrate molding process of step F101, a disk substrate is molded by injection molding of polycarbonate resin, for example.
FIG. 2 (a) schematically shows a mold for molding a disk substrate. This mold includes a lower cavity 20 and an upper cavity 22, and a stamper 21 for transferring information pits is disposed in the lower cavity 20. The stamper 21 is formed with an uneven pattern 23 of information pits. The lower cavity 20 is formed with an annular recess 24 for forming a protection ring as a ring-shaped region on the inner peripheral side of the disk.
In the manufacturing process of a read-only disk, a stamper 21 having an information pit uneven pattern 23 formed as an embossed pit is disposed. In the manufacturing process of a recordable disk (for example, a write-once disk or a rewritable disk), a recording track A stamper on which a concavo-convex pattern for forming a groove (wobbling groove) is formed is disposed.

The disk substrate 11 is formed by injection molding using such a mold, and the formed disk substrate 11 is as shown in FIG.
That is, the center of the disk substrate 11 made of polycarbonate resin is the center hole 14, and the information reading surface 13 side is a pattern of information pits 13a to which the unevenness formed on the stamper 21 in the mold is transferred. In some cases, not information pits but grooves (continuous grooves) are formed. An annular convex portion as a protection ring 15 is formed around the center hole 14 on the inner peripheral side. The protection ring 15 is formed, for example, at a height within 0.12 mm from the surface of the information reading surface 13 which is a reference surface.

The disk substrate 11 thus formed is formed with a layer structure on the information reading surface 13 side in steps F102, F103, and F104. FIGS. 3A and 3B show the layer structure in a state where the process proceeds to Step F104. FIG. 3B is an enlarged view of the layer structure on the information reading surface 13 side.
First, in step F102, a reflective film 17 made of, for example, an Ag alloy is formed on the information reading surface 13 on which the information pit pattern is formed.
In the next step F103, the light transmission layer 16 is formed by spin coating using an ultraviolet curable resin.
In the next step F104, the hard coat layer 18 is formed as a surface treatment on the information reading surface 13 side. The hard coat layer 18 may not be formed.
Further, in step F105, the moisture-proof film 19 is formed on the label surface side (the surface opposite to the information reading surface). In some cases, the moisture-proof film 19 is not formed.

  Finally, printing is performed on the label printing surface 12 on the disk substrate 11 on which the layer structure is formed as a printing process in step F106. In this printing process, as so-called offset printing, the entire surface on the label printing surface 12 side is flattened by applying a white coat, and then, for example, color printing is performed to form a printing layer 30 as shown in FIG. The

FIG. 4 shows details of the light transmission layer forming process in step F103 in such a series of optical disk manufacturing processes. In order to form the light transmission layer 16, the processing from Step F201 to Step F206 in FIG. 4 is performed.
First, in step F201, the disk substrate 11 that has undergone the processes of steps F102 and F102 of FIG. 1, that is, the disk substrate 11 that has been subjected to the formation of the reflective film 17, is placed on a spin coater. In step F202, the center cap 1 is attached to the center hole position of the disk substrate 11.
FIG. 5 schematically shows the spin coater 53 on which the disk substrate 11 is placed and the center cap 1 is mounted.
The spin coater 53 has a table unit 51 that rotates with the disk substrate 11 placed thereon. The table unit 51 is rotated by a motor 52.

The center cap 1 has a shape shown in FIGS. 6A and 6B as a plan view and a cross-sectional view. That is, the center cap 1 has a flat circular flange portion 2 whose upper surface is a dropping surface of the ultraviolet curable resin 50, a handling portion 3 protruding upward from the flange portion 2, and a fitting portion 4 protruding downward. Shaped.
The flange portion 2 has a substantially frustoconical cross-sectional shape with a thin outer peripheral portion and a thick inner peripheral portion, and the outer peripheral end portion 2a has a diameter of about 20 mm, for example, which is the outer periphery of the upper surface of the protection ring 15 of the disk substrate 11. It is substantially the same as the diameter of the end portion. Accordingly, the outer diameter of the outer peripheral end 2 a of the flange portion 2 and the outer diameter of the outer peripheral end of the upper surface of the protection ring 15 are substantially the same.
The angle β formed by the flange portion 2 and the surface on which the flange portion 2 is placed is set in a range of about 20 ° to 60 °.

FIG. 6C shows a cross section of the disk substrate 11 on which the center cap 1 is placed.
The outer peripheral diameter and inner peripheral diameter of the base portion of the protection ring 15 formed around the center hole 14 of the disk substrate 11 with the disk substrate 11 are about 21 mm and 17.5 mm, respectively. The thickness of the protection ring 15 is about 0.2 mm, and the angle α formed by the tapered side surface 15a of the protection ring 15 with respect to the substrate plane is set in the range of about 30 ° to 70 °. .
In the present embodiment, the relationship between the angles α and β is α ≧ β. This is an angular relationship suitable for smoothly spreading the ultraviolet curable resin 50 dropped on the center cap 1 onto the disk substrate 11. As an example, the angle α = 30 ° and the angle β = 25 °.
Furthermore, the outer diameter of the outer peripheral end portion of the upper surface of the protection ring 15 is 20.0 mm, and substantially coincides with the outer diameter of the outer peripheral end portion 2a of the flange portion 2 of the center cap 1 as described above.
The diameter of the center hole 14 is 15 mm, and the thickness of the disk substrate 11 is about 1.1 mm.

  In step F201, the disk substrate 11 is placed on the table unit 51 shown in FIG. 5. In step F202, the center cap 1 is moved to the spin coater 53 with the handling unit 3 held by the cap transport arm. Is mounted on the center hole 14 of the disk substrate 11 that is transferred to the center of the disk substrate 11. At this time, a fitting hole 54 is formed in the center portion of the rotary table, and the fitting portion 4 of the center cap 1 is attached so as to be fitted into the fitting hole 54. Accordingly, the center cap 1 and the disk substrate 11 are positioned so that the center positions thereof coincide.

After the disk substrate 11 and the center cap 1 are placed as shown in FIG. 5, in step F203, the UV curable resin 50 for forming the light transmission layer is dropped. That is, the ultraviolet curable resin 50 is dropped from a resin dropping nozzle 55 located above the spin coater 53 as shown in FIG. The viscosity of the UV curable resin 50 dropped is, for example, about 2000 cps.
The position of the tip of the nozzle 55 when the ultraviolet curable resin 50 is dropped is controlled so as to be on the upper surface of the flange portion 2 of the center cap 1. It collects on the upper surface of the flange portion 2.

This state is shown in FIG.
As already described, in the present embodiment, the diameter of the outer peripheral end 2a of the flange portion 2 of the center cap 1 and the diameter of the outer peripheral end of the upper surface of the protection ring 15 are substantially the same. In addition, the center position of the disk substrate 11 arranged on the spin coater 53 and the center position of the center cap 1 coincide. Therefore, as shown in FIG. 7A, the outer peripheral end 2a of the center cap 1 and the outer peripheral end of the upper plane of the protection ring 15 coincide with each other, and there is no step.
In such an arrangement state, the ultraviolet curable resin 50 dropped from the nozzle 55 is accumulated on the upper surface of the flange portion 2 of the center cap 1.

Subsequently, in step F204, the table portion 51 is rotationally driven by the motor 52, whereby the center cap 1 and the disk substrate 11 are rotated, whereby the ultraviolet curable resin 50 dropped on the center cap 1 is transferred to the disk substrate 11. It is spread over.
In addition, although the rotational speed at this time is adjusted with the thickness of the light transmission layer 16 to form, it is about 2000 rpm, for example.

FIG. 7B shows a state in which the ultraviolet curable resin 50 is spread, and the ultraviolet curable resin 50 is spread evenly to the outer peripheral edge of the disk substrate 11 by spin coating. For example, it is spread uniformly so as to have a thickness of about 100 μm.
Here, a part of the viscous UV curable resin 50 remains attached to the flange portion 2 as shown in FIG. However, the thickness of the ultraviolet curable resin 50 remaining on the flange portion 2 is much thinner than the thickness of the ultraviolet curable resin 50 spread on the disk substrate 11. In particular, the taper-shaped side surface 15a of the protection ring 15 and the flange portion 2 of the center cap 1 are inclined so that there is a contact between the outer peripheral end portion of the protection ring 15 and the outer peripheral end portion of the center cap 1. Since the step does not occur, the thickness of the ultraviolet curable resin 50 remaining around the contact portion becomes very thin. For example, it is about 2 μm to 3 μm.

After the ultraviolet curable resin 50 is spread in this manner, the center cap 1 is removed in step F205. FIG. 7C shows a state where the center cap 1 is removed from the disk substrate 11.
As described above, since the UV curable resin 50 remains only very thin at the contact portion between the outer peripheral end of the protection ring 15 and the outer peripheral end of the flange portion 2 of the center cap 1, the center cap 1 is When lifting, the UV curable resin 50 on the disk substrate 11 is hardly lifted at the same time. That is, the center cap 1 can be removed in a state where the interruption of the ultraviolet curable resin 50 is good.
Therefore, when the center cap 1 is removed, the shape of the ultraviolet curable resin 50 on the disk substrate 11 before curing is hardly disturbed. Further, since the ultraviolet curable resin 50 on the disk substrate 11 is not lifted, bubbles are not mixed into the layer of the ultraviolet curable resin 50.

After the center cap 1 is removed, the entire surface of the substrate is cured by irradiating the disk substrate 11 on which the ultraviolet curable resin 50 is spread with ultraviolet irradiation while rotating the disk substrate 11 in Step F206. .
The formation of the light transmission layer 16 is completed in the process of step F206, and the disk substrate 11 is shifted to the hard coat forming process of step F104 in FIG.

As can be understood from the above description, in this example, the center cap 1 is used in which the diameter of the outer peripheral end 2a of the flange portion 2 is substantially the same as the diameter of the outer peripheral end of the upper surface of the protection ring 15. The center cap 1 is placed at the center of the disk substrate 11. Then, the ultraviolet curable resin 50 is dropped on the center cap 1 and spin coating is performed.
As a result, when the center cap 1 is removed, the center cap 1 does not lift a large amount of the viscous UV curable resin 50. Therefore, the shape of the UV curable resin 50 spread on the disk substrate 11 is not reduced. Disturbance is prevented and the shape (appearance) of the light transmission layer 16 formed by subsequent curing does not become dirty. Also, there is almost no air bubbles.
From these things, a high quality optical disk can be manufactured.

By the way, in the present embodiment, the outer diameter of the outer peripheral end portion of the upper surface of the protection ring 15 and the outer diameter of the outer peripheral end portion 2a of the flange portion 2 of the center cap 1 have been described as being substantially the same. Therefore, as described with reference to FIG. 7, the outer peripheral end 2a of the center cap 1 and the outer peripheral end of the protection ring 15 are placed without any step, and the ultraviolet curable resin 50 is smoothly spread. .
Here, in the actual manufacturing process, due to molding errors of the center cap 1 and the disk substrate 11 and positioning errors when the center cap 1 is mounted, the outer peripheral end 2a of the center cap 1 and the outer peripheral end of the upper surface of the protection ring 15 are used. However, the outer diameter of the outer peripheral end 2a of the flange portion 2 of the center cap 1 is smaller than the outer diameter of the outer peripheral end of the upper surface of the protection ring 15, and a step is generated. It is also possible.
For example, as shown in FIG. 8, a slight step P may occur between the contact surfaces of the outer peripheral end 2 a of the flange portion 2 of the center cap 1 and the outer peripheral end of the upper surface of the protection ring 15.

However, even if there are some stepped portions P as described above, the flange portion 2 and the protection ring of the center cap 1 are used as the setting of the angle α and the angle β (for example, the angle α = 30 °, the angle β = 25 °). Since the side surface 15a on the 15 taper is continuously inclined to some extent, the ultraviolet curable resin 50 is smoothly spread.
Thus, when the inclination from the flange portion 2 of the center cap 1 to the side surface 15a of the protection ring 15 is set, the occurrence of a slight level difference P does not have a great influence. When the center cap 1 is removed, the resin on the disk substrate 11 is not disturbed or air bubbles are hardly mixed. Accordingly, a slight step P, that is, a slight step P caused by an error within a range allowed in normal manufacturing, such as a molding error of the center cap 1 and the disk substrate 11 and a positioning error when the center cap 1 is mounted. Can be considered as being within the range of substantially coincidence in the present invention.

It should be noted that the present invention should not be limited to the configuration as the embodiment described so far. The dimensions of the center cap, the disk substrate, and the protection ring are merely examples, and the optical disk manufacturing method described in the present embodiment can be applied in addition to the above dimensions. Further, it can be widely applied as a spin coating method.
In addition, the optical disc manufacturing method of the present invention can be applied to manufacture of various optical discs such as a Blu-ray disc method, a DVD method, and a CD (Compact Disc) method.

It is explanatory drawing of the process of the disc manufacturing method of embodiment of this invention. It is explanatory drawing of manufacture of the disk substrate of embodiment. It is explanatory drawing of layer structure formation of the disc board | substrate of embodiment. It is explanatory drawing of the light transmissive layer formation process of embodiment. It is explanatory drawing of the spin coater of embodiment. It is explanatory drawing of the center cap of embodiment. It is explanatory drawing of the spin coat of embodiment. It is explanatory drawing in case there exists a level | step difference in arrangement | positioning of the center cap and protection ring of embodiment. It is explanatory drawing of the conventional disc board | substrate. It is explanatory drawing of the conventional spin coat. It is explanatory drawing of the conventional spin coat.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Center cap, 2 flange part, 2a outer periphery edge part, 11 disc board | substrate, 15 protection ring, 16 light transmission layer 50 UV curable resin

Claims (2)

A substrate molding process for molding an optical disk substrate;
An upper surface and an inclined surface having an outer peripheral edge having an outer diameter substantially equal to the outer diameter of the upper surface of the truncated cone-shaped annular convex portion having an inclined surface formed around the center hole of the optical disk substrate at the center of the optical disk substrate A layer forming step of placing a truncated cone-shaped center cap formed of a flange portion formed with a layer structure and spreading a layer structure material dropped on the center cap onto an optical disk substrate by spin coating to form a layer structure; ,
Equipped with a,
In the layer forming step, the layer structure material is spread on a continuous inclined surface of the inclined surface of the annular convex portion and the inclined surface of the flange portion . In the center of the circular substrate, an upper surface and an inclined surface having an outer peripheral end having an outer diameter substantially coincident with the outer diameter of the upper surface of the circular convex portion having the inclined surface formed in the central portion of the circular substrate. A circular truncated cone-shaped center cap is placed, a layer structure material is dropped on the center cap, and the circular substrate is rotated, whereby the layer structure material is transferred to the circular substrate. Spread on top to form a layer structure ,
The spin coat method in which the layer structure material is spread on a continuous inclined surface of the inclined surface of the annular convex portion and the inclined surface of the flange portion .

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