JP2008123610A - Optical information recording medium and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical information recording medium reducing a spread of a curing resin when the resin is supplied and variation in thickness of a cover layer as a result and to provide the optical information recording medium using a substrate for attaining the method. <P>SOLUTION: In the optical information recording medium 1, a reflection layer 3 and a recording layer 4 are formed on one surface on a light incident side of a circular substrate 2 having a through hole CH in a central part and the light transmissible cover layer 5 is provided on the recording layer 4. In the substrate 2, thickness t' in a region around the through hole CH is made thinner than the thickness t of a part where the recording layer 4 is formed and a recessed part 6 is formed in the surface on the light incident side where the reflection layer 3 and the recording layer 4 are formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a substrate shape used for a next-generation optical information recording medium such as a Blu-ray disc, and a method for manufacturing an optical information recording medium using the same.

  As information recording media, optical information recording media such as optical discs are rapidly spreading. As such an optical information recording medium, there is one in which a reflective layer and a recording layer are formed on a light transmissive resin substrate having a thickness of 1.2 mm (diameter 120 mm or 80 mm) such as a CD-R. In recent years, higher information recording density has been demanded. Therefore, a method of using an objective lens having a short laser wavelength and a large numerical aperture (NA) is conceivable, and an optical information recording medium such as a DVD ± R is realized. This DVD ± R is bonded to two optically transmissive resin substrates having a thickness of 0.6 mm in order to increase the allowable value of the tilt angle (tilt) of the disc by shortening the wavelength and increasing the NA. The reflective layer and the recording layer are sandwiched between them.

  However, in recent years, a higher information recording density has been required in order to record high-definition video data. Therefore, like Blu-ray Disc, a structure in which a reflective layer and a recording layer are formed on the light incident surface side of a resin substrate having a thickness of 1.1 mm and this recording layer is covered with a light-transmitting cover layer having a thickness of 0.1 mm. Optical information recording media have been proposed.

In the case of such an optical information recording medium, in order to form a cover layer, as disclosed in Japanese Patent No. 3726759 and Japanese Patent Application Laid-Open No. 2004-288270, a light transmissive ultraviolet curable resin or radiation curable resin is used. There has been proposed a method of forming a film by spin coating. This method is a method in which a through hole at the center of the substrate is closed with a center cap, a curable resin is supplied to the center of the substrate with a nozzle or the like, and stretch coating is performed by spin coating. Since the viscosity of the curable resin before curing is relatively high at 1000 to 3000 cps, in order to make the thickness of the cover layer uniform, the curable resin is supplied while rotating the substrate in a stationary state or at a relatively low speed (for example, 60 rpm). Then, it is necessary to make it stay in the center and then apply it by stretching at a high speed (for example, 5000 rpm).

Japanese Patent No. 3762759 JP 2004-288270 A

In such a method, the curable resin stays in the center of the substrate until it is rotated and stretched, and when the substrate is rotated, there is no variation in the resin amount in the circumferential direction, that is, substantially concentric. It is desirable that the curable resin is stretched and applied. However, the center cap is actually inclined to some extent, and the curable resin is supplied with a certain amount of extra amount in addition to the necessary amount to make the coating thickness uniform. It spreads in the direction. In addition, since the curable resin has a relatively high viscosity, it takes time to discharge from the nozzle, and thus the spread of the curable resin HR varies as shown in FIG.

When the substrate 2 'is rotated and applied in such a state as shown in FIG. 8, the application of centrifugal force becomes uneven as shown in FIG. 8, and the method of extending the curable resin HR varies. In this case, the thickness of the curable resin HR varies in the circumferential direction. Since the cover layer allows recording light or reproduction light to pass therethrough, the tolerance of variation in thickness thereof is, for example, about ± 2 μm for a Blu-ray disc. The conventional method has a problem that the variation exceeds the tolerance.

The present invention relates to a method for manufacturing an optical information recording medium capable of suppressing the spread at the time of supplying a curable resin and reducing the variation in the thickness of the cover layer, and an optical information recording using a substrate for realizing the method. It proposes a medium.

  In the present invention, as a first technical means, a circular substrate having a through-hole in a central portion, a reflective layer and a recording layer formed on one side of the substrate which is a light incident side, the reflective layer and the In the optical information recording medium having a light-transmitting cover layer provided on the surface on which the recording layer is formed, the substrate has the through hole so that a region near the through hole on the light incident side becomes a recess. Proposed is an optical information recording medium characterized in that the substrate thickness in the vicinity region is thinner than the substrate thickness in the region where the reflective layer and the recording layer are formed.

  According to the first technical means described above, the spread of the curable resin can be suppressed by the recesses in the vicinity of the through-holes, and the stretch coating is performed uniformly by spin coating, so that the light with reduced variation in the thickness of the cover layer is reduced. An information recording medium can be obtained. The vicinity of the through hole refers to a region within a radius of 11.5 mm of the substrate from the edge of the through hole. That is, the concave portion is a circular concave portion having a diameter of 23 mm or less sharing a central point with the through hole.

In the present invention, as a second technical means, an optical information recording medium is proposed in which the step portion of the recess is an inclined surface. According to the second technical means, at the time of spin coating, the curable resin retained in the recesses can flow out smoothly. This makes it possible to apply uniform stretching.

  According to the present invention, there is provided a step of preparing a circular substrate having a through hole in the central portion and having a reflective layer and a recording layer formed on one surface on the light incident side, and the through hole of the substrate is provided with a center cap. And supplying a light-transmitting curable resin to the region near the through-hole on the light incident surface side, and rotating the substrate to spin the coating on the surface on which the reflective layer and the recording layer are formed. In the method for manufacturing an optical information recording medium, comprising: coating with the curable resin; and curing the curable resin to form a cover layer. An optical information recording medium using a substrate in which the thickness of the substrate in the vicinity of the through hole is thinner than the thickness of the substrate in the region where the reflective layer and the recording layer are formed so as to form a recess. We propose a method for manufacturing.

According to this manufacturing method, it is possible to suppress the spread at the time of supplying the curable resin, and it is possible to manufacture an optical information recording medium in which the variation in the thickness of the cover layer is reduced.

  According to the present invention, since the spread at the time of supplying the curable resin can be suppressed and the coating can be uniformly applied, an optical information recording medium in which the variation in the thickness of the cover layer is reduced can be obtained.

  An embodiment of the optical information recording medium of the present invention will be described with reference to the drawings, taking a single-layer optical disk as an example. FIG. 1 is a schematic cross-sectional view of the right half from the center line of the optical information recording medium of the present invention. The optical information recording medium 1 includes a circular substrate 2 having a through hole CH serving as a center of rotation at a central portion, a reflective layer 3 formed on a surface on the light incident side of the substrate 2, and the reflective layer 3 A recording layer 4 formed on the recording layer 4 and a light-transmitting cover layer 5 provided on the recording layer 4.

  The substrate 2 is a resin substrate having a diameter of 120 mm and a thickness t of 1.1 mm where the reflective layer 3 and the recording layer 4 are formed. For this substrate 2, various materials used as substrate materials for conventional optical information recording media can be arbitrarily selected and used. Specific examples include acrylic resins such as polycarbonate and polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, metals such as epoxy resins, amorphous polyolefins, polyester resins, and aluminum, and glass. These may be used together if necessary. Among the above materials, a thermoplastic resin is preferable from the viewpoint of moldability, moisture resistance, dimensional stability, and low price, and polycarbonate is particularly preferable.

  In this substrate 2, the thickness t ′ in the vicinity of the through hole CH is thinner than the thickness t of the portion where the reflective layer 3 and the recording layer 4 are formed, and the light incident side surface, that is, the recording layer 4 is formed. A recess 6 is formed on the surface. The distance L from the center line of the substrate 2 to the upper end of the stepped portion 6a of the recess 6 is 11.5 mm at the maximum, and the recess 5 is formed in a region of this radius L. The depth d of the recess 6 is 50 μm to 300 μm, preferably about 200 μm.

  The reflection layer 3 is formed of a metal thin film such as Ag or Al, and the recording layer 4 is formed of a layer having a dye such as cyanine or azo. The recording layer 4 may be a phase change type thin film instead of the dye layer in order to make a rewritable optical information recording medium. In FIG. 1, the recording layer is a single layer, but using a transflective layer, for example, from the light incident side in the order of the first recording layer-semi-transmissive reflective layer-second recording layer-reflective layer. The formed recording layer may have a multilayer structure. Further, a layer for adjusting recording characteristics, improving adhesiveness or protecting the recording layer 3 is provided between the substrate 2 and the reflective layer 3, between the reflective layer 3 and the recording layer 4, or between the recording layer 4 and the cover layer 5. You may form in between.

  The cover layer 5 is formed of a light transmissive resin, and a curable resin that is cured by ultraviolet rays or radiation is used. This curable resin has a viscosity before curing of about 1000 to 3000 cps, preferably about 2000 cps, and has a light transmittance of 0.1 mm after curing and a spectrophotometer measured with light having a wavelength of 405 nm. 70% or more, preferably 80% or more. The cover layer 5 is formed by applying this curable resin by spin coating so that the thickness on the recording layer 4 is 0.1 mm. In FIG. 1, the surface of the cover layer 5 is drawn flat for convenience, but a dent due to the recess 6 may actually be formed.

  Next, a method for manufacturing such an optical information recording medium 1 will be described. First, a polycarbonate disk substrate 2 having a diameter of 120 mm, a thickness of 1.1 mm, a through hole CH having a diameter of 15 mm and a recess 5 having a diameter of 23 mm and a depth of 200 μm is formed by injection molding. The reflective layer 3 is formed by adhering Al metal to the region having a radius of 21 mm to 58.5 mm on the surface of the substrate 2 where the recess 6 is formed by sputtering. Next, the recording layer 4 is formed on the reflective layer 3 by applying a cyanine dye solution by spin coating.

  Thus, the substrate 2 on which the reflective layer 3 and the recording layer 4 are formed is prepared. As shown in FIG. 2, the substrate 2 is placed on a rotary table (not shown) of a spin coater, and the through hole CH is placed in the center cap. Close with CC. Next, a light transmissive ultraviolet curable resin HR having a viscosity of 2000 cps is discharged from the nozzle NZ and supplied into the recess 6. At this time, the rotary table is supplied while rotating at a relatively low speed of 60 rpm. If the nozzle NZ is plural (preferably three or more) or the nozzle NZ is moved, the rotary table may be stationary. Since the supplied curable resin HR is blocked by the step portion 6a, it is retained in a circular shape as shown in FIG.

  After supplying the necessary amount + α of the curable resin HR, the rotary table is rotated at a high speed of 5000 rpm. As a result, the curable resin HR flows over the step portion 6 a and covers the reflective layer 3 and the recording layer 4. At this time, since the centrifugal force is evenly applied to the curable resin HR, as shown in FIG. 5, it is spread and applied in a substantially concentric circle shape. After application, the curable resin HR is cured by irradiating with ultraviolet rays. In this way, the cover layer 5 having a thickness of 0.1 mm is formed. The thickness of the cover layer can be controlled by the viscosity of the curable resin HR and the rotation speed of the rotary table, as well as the rotation acceleration of the rotary table. Can be set. The thickness of the cover layer of the optical information recording medium 1 obtained in this way becomes a substantially uniform thickness with a variation of ± 2 μm.

  In addition, as shown in FIG. 6, you may make the level | step-difference part 6a into an inclined surface. With such a shape, the curable resin HR can flow out smoothly during spin coating. As shown in FIG. 6 (a), it may be linearly inclined as seen in the cross section, but as shown in FIGS. 6 (b) to 6 (d), it is more effective if the R shape is seen in the cross section. . In particular, as shown in FIGS. 6C and 6D, if the upper portion of the stepped portion 6a is R-shaped, the curable resin HR can flow out more smoothly.

  The embodiment of the present invention has been described above, but manufacturing conditions, various dimensions, and the like are arbitrary, and can be appropriately adjusted within the scope of the present invention.

It is a schematic cross section of the right half toward the center line of the optical information recording medium of the present invention. It is a schematic cross section which shows the manufacturing process of the optical information recording medium of this invention. It is a schematic cross section which shows the manufacturing process of the optical information recording medium of this invention. It is a plane schematic diagram which shows the manufacturing process of the optical information recording medium of this invention. It is a plane schematic diagram which shows the manufacturing process of the optical information recording medium of this invention. It is a fragmentary sectional view showing the variation of the shape of level difference part 5a. It is a plane schematic diagram which shows the manufacturing process of the conventional optical information recording medium. It is a plane schematic diagram which shows the manufacturing process of the conventional optical information recording medium.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical information recording medium 2, 2 'board | substrate 3 Reflective layer 4 Recording layer 5 Cover layer 6 Concave part 6a Step part

Claims (3)

Provided on a circular substrate having a through-hole in the central portion, a reflective layer and a recording layer formed on one side of the substrate on the light incident side, and a surface on which the reflective layer and the recording layer are formed An optical information recording medium having a light-transmitting cover layer,
The substrate is such that the substrate thickness in the region near the through hole is thinner than the region in which the reflective layer and the recording layer are formed so that the region near the through hole on the light incident side becomes a recess. A characteristic optical information recording medium.   The optical information recording medium according to claim 1, wherein the step portion of the concave portion is an inclined surface. Providing a circular substrate having a through hole in the central portion and having a reflective layer and a recording layer formed on one surface on the light incident side;
Filling the through hole of the substrate with a center cap and supplying a light-transmitting curable resin to a region near the through hole on the light incident surface side;
Covering the surface on which the reflective layer and the recording layer are formed by spin coating and rotating the substrate with the curable resin;
Curing the curable resin to form a cover layer, and a method of manufacturing an optical information recording medium comprising:
As the substrate, the substrate thickness in the region near the through hole is made thinner than the region in which the reflective layer and the recording layer are formed so that the region near the through hole on the light incident side becomes a recess. A method for manufacturing an optical information recording medium, comprising using a substrate.

Images