JP2003085834A - Method of manufacturing optical information medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the thickness unevenness of a light transmission layer in the radial direction of an optical information medium smaller and to prevent air bubbles to be the cause of a recording/reproducing error and a servo error from mixing into the light transmission layer in forming the light transmission layer by a spin coating method in a method of manufacturing the optical information medium in which a laser beam for recording/reproducing is made incident on an information recording layer through the light transmission layer. SOLUTION: This method comprises forming the light transmission layer by disposing the information recording layer on a supporting substrate 100, then covering the central hole of the supporting substrate by blockade means 3, supplying a coating liquid 5 containing a resin to the surface of the blockade means and spreading the coating liquid 5 onto the surface of the supporting substrate 100 by spin coating, in which the center line average roughness Ra of the surface of the blockage means touched by the coating liquid is confined to <=100 nm and the ten point mean roughness Rz thereof is confined to <=1 μm or the mean inclination angle θa of the roughness is confined to <=1 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing various types of optical information media such as read-only type, write-once type and rewritable type.

[0002]

2. Description of the Related Art In recent years, in optical information media such as read-only optical disks and optical recording disks, a huge amount of information such as moving picture information is recorded or stored. Therefore, it is required to increase the recording density to increase the capacity of the medium. In order to meet the demand, research and development for higher recording density have been actively conducted.

One of them is, for example, a DVD (Di
As can be seen in the gital Versatile Disk), the recording / reproducing wavelength is shortened, and the numerical aperture (NA) of the objective lens of the recording / reproducing optical system is increased to reduce the laser beam spot diameter during recording / reproducing. It is suggested to do so.
Compared to CD with DVD, the recording / reproducing wavelength is 780 nm
To 650 nm and NA from 0.45 to 0.6, the recording capacity of 6 to 8 times (4.7 GB /
Aspect) has been achieved.

However, if the NA is increased as described above, the tilt margin becomes small. The tilt margin is
The tolerance of the tilt of the optical information medium with respect to the optical system, which is NA
Determined by In an optical information medium having an information recording layer on a transparent substrate and a recording / reproducing laser beam incident on the information recording layer through the transparent substrate, the recording / reproducing wavelength is λ, the thickness of the transparent substrate Is d, the tilt margin is proportional to λ / (d · NA ³ ). Further, when the translucent substrate is tilted with respect to the laser beam, that is, when tilt is generated, wavefront aberration (coma aberration) occurs. Assuming that the refractive index of the transparent substrate is n and the tilt angle is θ, the wavefront aberration coefficient is (1/2) · d · {n ² · sin θ · cos θ} · NA ³ / (n
² −sin ² θ) ^-5/2 . From these equations, it is understood that the thickness d of the light-transmissive substrate should be reduced in order to increase the tilt margin and suppress the occurrence of coma. In fact DV
In D, the thickness of the translucent substrate is the same as that of the CD substrate (1.2 mm
The tilt margin is secured by setting it to about half (about 0.6 mm).

By the way, in order to record a moving image of higher quality for a long time, a structure has been proposed in which the translucent substrate can be made thinner. In this structure, a substrate having a normal thickness is used as a supporting substrate for maintaining rigidity, pits and recording layers are formed on the surface thereof, and a thin transparent substrate having a thickness of 1 is formed thereon.
A light transmitting layer having a thickness of about 00 μm is provided, and recording / reproducing light is incident through this light transmitting layer. In this structure,
By making the light transmission layer extremely thin and making the distance between the objective lens and the medium surface (working distance: working distance) smaller than that of the conventional transparent substrate, an objective lens with a high NA can be used. . An optical disc system using a medium having such a structure is described in Vol. 22, No.
2-O plus E, p175-181. In this system, an aspherical second lens group with a laser wavelength of 405 nm and an NA of 0.85 is used, the light transmission layer has a thickness of 100 μm, the working distance is 130 μm, and a recording capacity of 22 GB / surface is achieved. .

As a method for forming the above-mentioned thin light-transmitting layer, there is a so-called cover sheet method in which a thin sheet of polycarbonate resin is attached to a supporting substrate side by an adhesive layer made of a pressure sensitive adhesive or an ultraviolet curable adhesive. For example, a method of forming a coating film of an ultraviolet curable resin on a supporting substrate by spin coating, which is described in, for example, JP-A-11-203724 is known.

The above-mentioned cover sheet method is a prior art D
It is relatively easy to implement by applying the VD bonding method. However, since the sheet to be bonded is manufactured by punching out a huge sheet having a uniform thickness into a circular disc shape, the loss amount per disc is large and the material cost is high. In addition, since a large amount of garbage is generated, the environmental load becomes large.

On the other hand, in the method of spin-coating an ultraviolet-curable resin, the resin shaken off during the spin-coating can be circulated in the apparatus and reused, so that the utilization efficiency of the resin is increased and the cost is reduced. It can be kept low. Further, since the thickness of the light transmitting layer can be arbitrarily set by controlling the spin coating time and the viscosity of the resin, the method of forming the light transmitting layer by the spin coating method can be applied to various optical disc systems. It is a versatile method applicable to.

When the light transmitting layer is formed by using the spin coating method, the resin is supplied to the inner peripheral portion of the supporting substrate, and then,
The support substrate is rotated and the resin is spread by centrifugal force.
Since the support base has a central hole that is used when it is loaded into the optical disk drive, the resin cannot be supplied to the center of rotation (center of the support base), and is supplied in an annular shape at an equal distance from the center of rotation. Will be done. However, the further the resin supply position is from the center of rotation, the greater the thickness unevenness of the light transmission layer in the radial direction. Specifically, the light transmission layer becomes thicker on the outer peripheral side than on the inner peripheral side of the supporting substrate. The presence of such unevenness in the thickness of the light transmission layer hinders the tracking of the optical pickup for recording / reproduction.

In order to reduce the thickness unevenness in the radial direction of the light transmitting layer formed by the spin coating method, the central hole of the supporting base (disk substrate) is provided with a plate member, a disk portion, a closing plate,
It has been proposed that the resin is closed by a closing means such as a cap and the resin is supplied near the center of the closing means, that is, near the center of rotation (Japanese Patent Laid-Open No. 10-320850).
No. 249264, No. 10-289489,
11-195250, 11-195251, 11-203724).

[0011]

In an optical disc, if there is a defect in a light-transmitting substrate through which a recording / reproducing laser beam passes, focusing of the laser beam on the information recording layer is hindered and recording / reproducing is performed. May cause problems. In the optical disc having the light transmitting layer, the signal recording density is higher than that of the conventional optical disc, so that the allowable size of the defect is small.

However, the inventors of the present invention have found that when the spin coating is performed in a state where the central hole of the disk substrate is closed by the closing means as described above, the thickness of the light transmitting layer is increased in the light transmitting layer. It has been found that bubbles with a diameter of less than 10 mm are easily caught. For example, when the recording track pitch is 0.3 μm and the bit length is 0.130 μm in the above optical disc system having a recording capacity of 22 GB / surface, 10
When air bubbles of size μm × 10 μm exist in the light transmission layer,
If a large-scale error of 76 bits at the maximum during recording / reproduction is continuous, or if one track of the disk is one track, 33
There will be large errors across tracks. In addition, such a large bubble adversely affects the tracking servo and the focus servo of the optical pickup, and becomes a factor that causes a track deviation and a focus deviation.

The present invention is a method for manufacturing an optical information medium in which a laser beam for recording / reproducing is incident on the information recording layer through the light transmitting layer, and when forming the light transmitting layer by spin coating, the radius of the medium is It is intended to reduce the thickness unevenness of the light transmitting layer in the direction and prevent the bubbles causing the recording / reproducing error and the servo error from entering the light transmitting layer.

[0014]

[Means for Solving the Problems] The above-mentioned object is as follows (1)
It is achieved by the present invention of (4). (1) An information recording layer and a resin-containing light transmitting layer are provided in this order on a disc-shaped supporting substrate having a central hole, and a laser beam for recording or reproducing passes through the light transmitting layer. A method of manufacturing an optical information medium used to enter an information recording layer, comprising: providing a central hole of the supporting base with a disc portion after providing the information recording layer on the supporting base. The coating means by covering the disk portion of the means, then supplying a coating liquid containing a radiation curable resin onto the disk portion, and then rotating the closing means and the supporting base integrally. A resin spreading step of spreading a liquid on the supporting substrate to form an annular resin layer, and a hardening step of hardening the resin layer by irradiation of radiation to form the light transmitting layer are provided. Of the surface of the disk where the liquid contacts A method of manufacturing an optical information medium using a closing means having a center line average roughness Ra of 100 nm or less at least in part. (2) An information recording layer and a light-transmitting layer containing a resin are provided in this order on a disc-shaped supporting substrate having a central hole, and a laser beam for recording or reproducing passes through the light-transmitting layer. A method of manufacturing an optical information medium used to enter an information recording layer, comprising: providing a central hole of the supporting base with a disc portion after providing the information recording layer on the supporting base. The coating means by covering the disk portion of the means, then supplying a coating liquid containing a radiation curable resin onto the disk portion, and then rotating the closing means and the supporting base integrally. A resin spreading step of spreading a liquid on the supporting substrate to form an annular resin layer, and a hardening step of hardening the resin layer by irradiation of radiation to form the light transmitting layer are provided. Of the surface of the disk where the liquid contacts A method for manufacturing an optical information medium, which uses a closing means having a ten-point average roughness Rz of 1 μm or less at least in part. (3) An information recording layer and a light-transmitting layer containing a resin are provided in this order on a disc-shaped supporting substrate having a central hole, and a laser beam for recording or reproducing passes through the light-transmitting layer. A method of manufacturing an optical information medium used to enter an information recording layer, comprising: providing a central hole of the supporting base with a disc portion after providing the information recording layer on the supporting base. The coating means by covering the disk portion of the means, then supplying a coating liquid containing a radiation curable resin onto the disk portion, and then rotating the closing means and the supporting base integrally. A resin spreading step of spreading a liquid on the supporting substrate to form an annular resin layer, and a hardening step of hardening the resin layer by irradiation of radiation to form the light transmitting layer are provided. Of the surface of the disk where the liquid contacts A method for manufacturing an optical information medium, which uses a closing means having an average inclination angle θa of roughness of 1 ° or less at least in part. (4) The method for manufacturing an optical information medium according to any one of (1) to (3) above, wherein the closing means is manufactured by injection molding of resin.

[0015]

As a result of repeated studies, the inventors of the present invention controlled the surface roughness of the area of the surface of the blocking means to which the coating liquid is supplied, and thereby the bubbles mixed in the light transmitting layer. Found that the number of

In the present invention, the spin coating method, which reduces the material cost, is used, and the blocking means capable of suppressing the thickness unevenness of the light transmitting layer in the radial direction of the medium is used. Since it is possible to suppress the inclusion of air bubbles, it is possible to provide a high-performance optical information medium at low cost.

If the surface roughness of the closing means is controlled according to the present invention, the above effect can be realized regardless of the constituent material of the closing means.

For example, by using a metal material such as stainless steel, the closing means is produced by a processing means such as shaving.
The surface roughness may be reduced by mirror-polishing the surface. However, the metal closing means, which requires machining such as shaving and surface polishing, has a high manufacturing cost and therefore is premised on repeated use. However, since the coating solution adheres to the surface of the once-used closing means, it is not preferable to reuse it as it is. Therefore, for repeated use, it is necessary to clean the closing means after each use, which results in a cleaning cost. Moreover, it is necessary to prepare a large number of closing means in order to reduce the time loss due to cleaning, which further increases the cost.

Further, in order to reduce the surface roughness of the metallic closing means, a means other than polishing can be used.
For example, the surface roughness defined by the present invention can be obtained by coating the surface of the blocking means with various resins such as an ultraviolet curable resin. When an ultraviolet curable resin is used, it may or may not be cured after coating. However, when the resin coating is performed, dust may be attached to the surface of the coating film, or the blocking means may be attached to the support base side by the resin that has flowed around the back surface of the blocking means during coating. If dust adheres to the coating film on the surface of the blocking means, it may cause defects during spin coating, and it may not be possible to obtain a uniform light transmitting layer. In addition, if the blocking means and the supporting substrate are adhered to each other by the resin that wraps around the back surface of the blocking means during coating, the spin coater may malfunction.

In the present invention, it is most preferable that the closing means is made by injection molding of resin. In injection molding method,
It is possible to mass-produce the closing means having a small surface roughness at low cost. Therefore, the closure means can be disposable. Further, the resin constituting the closing means may be the same as the supporting base constituent material (for example, a polycarbonate resin), so that the material cost can be reduced by mass-procuring the same material. Further, since the excess resin discharged when the supporting substrate is manufactured by injection molding can be reused to manufacture the closing means, it is possible to reduce waste.

[0021]

FIG. 8 shows an example of the structure of an optical information medium manufactured according to the present invention. This optical information medium is a recording medium, and has a recording layer 104 as an information recording layer on a supporting base 120, and a light transmitting layer 102 on this recording layer 104. A laser beam for recording or reproduction enters through the light transmitting layer 102.

The present invention can be applied regardless of the type of recording layer. That is, for example, even if it is a phase change recording medium,
It can be applied to both a pit formation type recording medium and a magneto-optical recording medium. Note that a dielectric layer and a reflective layer are usually provided on at least one side of the recording layer for the purpose of protecting the recording layer and optical effects, but they are not shown in FIG. Further, the present invention is applicable not only to the recordable type shown in the drawing but also to the read-only type. In that case, a pit row is provided on the surface of the supporting substrate, and a reflective layer made of a metal, a semimetal, a dielectric multilayer film or the like is provided so as to cover the pit row. This reflective layer constitutes the information recording layer.

Next, a method for forming the light transmitting layer will be described.

First, as shown in FIGS. 1 and 2, the disk substrate 100 is placed on the rotary table 2. The disc substrate 100 is a supporting base provided with an information recording layer and has a central hole 101. The disk substrate 100 is fixed by inserting the center hole 101 into the annular protrusion 21 of the turntable 2. Although these figures are sectional views, only the end faces appearing in the section are shown, and the illustration in the depth direction is omitted. The same applies to the sectional views thereafter.

Then, the central hole 101 is closed by the closing means 3. The closing means 3 has a disc portion 31 for closing the central hole 101, a support shaft 32 integrated in the center thereof, and a convex portion integrated with the disc portion 31 on the side facing the central hole 101. 33 and 33. By fitting the convex portion 33 into the inner peripheral portion of the protrusion 21, the closing means 3 is attached to the rotary table 2.
Is fixed to the disk substrate 100 and the closing means 3
Can be positioned with. However, the method of fixing the disc substrate 100 and the closing means 3 to the turntable 2 is not particularly limited. For example, the closing means 3 is fitted to the turntable 2 in a state where the disc substrate 100 and the closing means 3 are fitted to each other. It may be allowed to.

Next, as shown in FIG. 3, a coating liquid 5 made of a resin or a resin solution is discharged from a nozzle 4, and the support shaft 3 is ejected.
The coating liquid 5 is supplied to the outer peripheral surface of 2. The coating liquid 5 is supplied to the upper surface of the disc portion 31 via the surface of the support shaft 32. At this time, it is preferable that the rotary table 2 is rotated at a relatively low speed, preferably 20 to 100 rpm, so that the coating liquid 5 uniformly spreads on the disc portion 31. The resin used in the present invention is a resin that can be cured by electromagnetic waves such as ultraviolet rays and particle beams such as electron beams, and is preferably an ultraviolet curable resin. In the following, a case where an ultraviolet curable resin is used will be described as an example.

Next, as shown in FIG. 4, the coating liquid 5 is spread by rotating the rotary table 2 at a relatively high speed. As a result, the resin layer 51 is formed on the disc substrate 100.
Is formed.

The spreading condition of the coating liquid is not particularly limited. It is known that the thickness of a coating film is theoretically proportional to the square root of the viscosity of the coating liquid when the conditions other than the viscosity of the coating liquid are the same in the spin coating method. On the other hand, the larger the rotation speed and the longer the rotation time, the thinner the coating film.
Therefore, the rotation speed and rotation time during spin coating may be appropriately determined according to the thickness of the resin layer 51 to be formed and the viscosity of the coating liquid. However, as will be described later, when forming a light transmission layer having a thickness of about 30 to 300 μm,
The viscosity of the coating solution is 100-100,000 cP, the rotation speed is 5
It is preferable to select from 00 to 6,000 rpm and the rotation time from the range of 2 to 10 seconds.

Next, as shown in FIG. 5, the closing means 3 is separated from the disk substrate 100, and then, as shown in FIG. 6, ultraviolet rays are irradiated to cure the resin layer 51 to form a light transmitting layer 102. In FIG. 6, ultraviolet rays are radiated on the rotary table 2, but a curing stage is provided separately from the rotary table,
It may be cured after that. Further, the closing means 3 may be separated while rotating the disk substrate 100.

The resin layer 51 may be hardened before removing the closing means 3 from the disk substrate 100. However, when the closing means 3 is removed after curing, burrs are generated near the boundary between the resin layer existing on the disc portion 31 and the resin layer existing on the disk substrate 100, or the cured resin becomes a fragment. It is easily scattered on the disk substrate 100.
Therefore, it is preferable to cure the resin layer 51 after removing the closing means 3.

The closing means used in the present invention may be any means as long as it has at least a disk portion capable of closing the central hole 101 of the disk substrate 100, and other configurations are not particularly limited, and are described in, for example, the above-mentioned respective publications. The closure means described can be used. However, the closing means 3 as shown in FIG. 1, that is, the closing means 3 having the support shaft 32 has the advantages described below. That is, the support shaft 32
Since it can be grasped, it becomes easy to handle the closing means 3, and in particular, it becomes easy to remove the closing means 3 after spin coating. Therefore, when the closing means 3 is separated from the disk substrate 100, the inner peripheral edge of the resin layer 51 is less likely to be disturbed.

Incidentally, Japanese Patent Laid-Open No. 11-195251 discloses a closing means in which a hollow cylindrical support or a support composed of a plurality of rods is integrated with a cap. The closure means shown in FIG. 1 has the following advantages.

In Japanese Patent Laid-Open No. 11-195251, the resin is dammed by the wall of the support or the rod-shaped body, so that the coating film tends to be uneven. On the other hand, in the closing means shown in FIG. 1, since the coating liquid is supplied to the outer peripheral surface of the support shaft to perform spin coating, unevenness of the coating film is unlikely to occur. Further, in the closing means shown in FIG. 1, since the resin adheres to the outer peripheral surface of the support shaft, the above-mentioned JP-A-11-195 has been proposed.
Cleaning of the closing means is easier than that of Japanese Patent No. 251. Further, in Japanese Patent Laid-Open No. 11-195251, since a coating liquid having a relatively high viscosity is supplied inside a hollow cylindrical support, the outer diameter of the support is reduced to ensure the fluidity of the coating liquid. Can not do it. Therefore, the application start position is relatively far from the center of rotation. On the other hand,
In the closing means shown in (1), the outer diameter of the support shaft can be made significantly smaller than that in the publication, so that the coating start position can be brought closer to the rotation center. As a result, it is possible to further reduce the thickness unevenness of the light transmission layer in the radial direction.

The closing means 3 shown in FIG. 1 has a circular truncated cone-shaped disc portion 31 and a cylindrical support shaft 32. In addition to this, for example, FIGS. 7 (A) to 7 (D). It is also possible to use the closing means having the configurations shown in FIGS.

The closing means 3 shown in FIG. 7 (A) has a circular truncated cone disk portion 31 and a circular truncated cone support shaft 32. In this way, it is preferable that the support shaft 32 has a shape that expands toward the disc portion 31, because it becomes easy to remove the closing means 3 from the mold during manufacturing by injection molding.

The closing means shown in FIG.
The cross-sectional shape of is different from that in FIG. In order to spread the coating liquid evenly on the disc portion 31, it is preferable that the thickness of the disc portion 31 gradually decreases toward the outer peripheral portion. In that case,
In the cross section of the disc portion 31, the shape of the upper edge on which the coating liquid is spread may be linear as shown in FIG. 7 (A) or curved as shown in FIG. 7 (B). It may be. Further, as shown in FIG. 7C, the outer circumference of the disc portion 31 may be a vertical surface. However, in FIG. 7C, the thickness t on the outer periphery of the disc portion 31 is preferably 0.4 mm or less. If the thickness t is too large, it becomes difficult to apply the resin layer evenly. Note that the disc portion 31 may have a uniform thickness as shown in FIG.

In the closing means used in the present invention, the minimum diameter of the support shaft 32 in the vicinity of the disc portion 31 is preferably less than 4 mm, more preferably 2 mm or less. Disk part 31
If the diameter of the support shaft 32 in the vicinity is too large, the coating start position is separated from the center of the disc portion 31, and the thickness unevenness of the resin layer 51 in the radial direction becomes large. However, if the diameter of the support shaft 32 in the vicinity of the disk portion 31 is too small, the mechanical strength of the support shaft 32 becomes insufficient, so the minimum diameter is preferably 0.5 mm or more, more preferably 0.7 mm or more. Is. The length of the support shaft 32 is not particularly limited, and may be appropriately determined so as to facilitate the supply of the coating liquid to the outer peripheral surface of the support shaft 32 and considering the ease of handling when gripping, and the like. Preferably 5-100
mm, more preferably 10 to 30 mm. If the support shaft 32 is too short, it becomes difficult to supply the coating liquid to the outer peripheral surface of the support shaft 32, and it becomes difficult to hold the coating liquid. On the other hand, if the support shaft 32 is too long, the handling becomes troublesome.

The diameter of the disk portion 31 may be larger than the diameter of the center hole 101 of the disc substrate and smaller than the inner diameter of the annular information recording layer of the disc substrate. However, since the coating liquid 5 may flow around the lower surface of the disk portion 31 and contaminate the peripheral surface of the central hole 101 (inner peripheral surface of the disk substrate), the diameter of the circular disk portion 31 is equal to the diameter of the central hole 101. 4 mm or more, particularly 8 mm or more. Further, when removing the disc portion 31, the resin layer 51 in the vicinity thereof is removed.
Since the shape is likely to be disturbed, the diameter of the disc portion 31 is preferably smaller than the inner diameter of the information recording layer by 3 mm or more, particularly preferably 5 mm or more. Although the specific size varies depending on the diameter of the central hole and the inner diameter of the information recording layer, it is usually 60 to 60 mm in diameter.
When the present invention is applied to an optical disc of about 130 mm, the diameter of the disc portion 31 is 20 to 40 mm, particularly 25 to 38.
It is preferably within the range of mm.

In the present invention, at least a part of the surface of the disk portion 31 (the upper surface of the disk portion 31 in FIG. 1) with which the coating liquid 5 contacts has a center line average roughness Ra of 1 or more.
00 nm or less, preferably 70 nm or less, a ten-point average roughness Rz of 1 μm or less, preferably 0.5 μm or less, and an average inclination angle θa of 1 ° or less, preferably 0.
It is 4 ° or less. When any of Ra, Rz, and θa is out of the range defined by the present invention, a large number of large bubbles are mixed in the resin layer 51 during spin coating. In the present invention, at least one of Ra, Rz and θa is
One, and preferably all are within the above-mentioned limited range. Even if Ra, Rz, and θa are made extremely small, the effect of suppressing the inclusion of air bubbles in the resin layer is not significantly improved, and Ra, Rz, and θa are made extremely small. Then, since the manufacturing cost of the closing means 3 becomes high, it is usually not necessary to set Ra to be less than 1 nm, Rz to be set to less than 0.001 μm, and θa is set to less than 0.01 °. No need.

The center line average roughness Ra and the ten-point average roughness Rz are both defined in JIS B0601. In addition, the average inclination angle θa of roughness in the present invention is described in
It is the same as the average inclination angle θa of roughness described in JP-A-01-1006, and is a value represented by the following formula (1).

[0041]

[Equation 1]

In the above formula (1), ΔX is a measurement pitch, and in the present invention, ΔX = 2 μm. ΔYi is N obtained by dividing the standard measurement length L by the measurement pitch ΔX.
It is a vertical distance between both ends of the i-th section among the number of sections.

The means for controlling the surface roughness of the surface of the closing means 3 is not particularly limited, and may be appropriately selected depending on the constituent material of the closing means 3 and the method of making it. For example, as described above, the surface roughness can be controlled by polishing the surface of the closing means made of metal. Further, in the resin closing means produced by injection molding, the surface roughness can be controlled by controlling the surface roughness of the mold, the purity of the resin, the injection molding conditions, and the like.

The constituent material of the closing means 3 used in the present invention is not particularly limited, and may be any of metal, resin, ceramics, etc., and may be a composite material using two or more kinds thereof. Further, the disc portion 31 and the support shaft 32 may be made of different materials. However, since the cost can be reduced as described above, it is preferable to manufacture the closing means by injection molding of resin.

When the closing means 3 is produced by injection molding of a resin, the resin used is not particularly limited, and various resins such as acrylic resin, styrene resin, olefin resin, nylon resin, and rubber resin can be used at a required price. It may be appropriately selected according to the characteristics and properties (chemical resistance, flexibility, etc.), but in particular,
Any of polycarbonate resin, polyolefin resin, and fluororesin is preferable. Also, the injection molding conditions are not particularly limited, and for example, various combinations of mold temperature and resin melting temperature can be set. However, it is usually preferable that the mold temperature and the resin melting temperature are low. If these temperatures are low, the transferability of the mold surface will be low and the surface roughness will be low. Further, since the cooling speed becomes faster, the temperature at the time of taking out from the mold becomes lower, and as a result, it is hard to be deformed at the time of taking out and the flatness becomes good.

Next, the specific structure of each part of the medium manufactured according to the present invention will be described.

The support substrate 120 is provided to maintain the rigidity of the medium. The thickness of the support substrate 120 is usually
The thickness may be 0.2 to 1.2 mm, preferably 0.4 to 1.2 mm, and may be transparent or opaque. The support base 120 may be made of resin as in the usual optical recording medium, but may be made of glass. The groove (guide groove) 121 usually provided in the optical recording medium can be formed by transferring the concavo-convex pattern provided on the support substrate 120 to each layer formed thereon, as shown in the figure. The groove 121 is a region existing on the front side when viewed from the recording / reproducing beam incident side, and a region existing between adjacent grooves is called a land.

The light transmitting layer 102 has a light transmitting property for transmitting a laser beam. The thickness of the light transmitting layer is 30 to
It is preferable to select from the range of 300 μm. If the light transmission layer is thinner than this, the optical influence of dust adhering to the surface of the light transmission layer increases. On the other hand, if the light transmission layer is too thick, it becomes difficult to achieve a high recording density by increasing the NA.

[0049]

EXAMPLES Example 1 A read-only optical disk sample was manufactured by the procedure shown in FIGS.

A disk-shaped support substrate having pits for holding information {made of polycarbonate resin, outer diameter 120 mm,
A reflective layer made of Al is formed on the surface having an inner diameter (diameter of the central hole) of 15 mm and a thickness of 1.2 mm} by a sputtering method,
The disk substrate 100 was obtained.

Next, the light transmitting layer was formed by the following procedure using the method of the present invention using the closing means. The closing means 3 used was produced by shaving stainless steel and then polishing the surface. This closing means 3 is
The disk portion 31 has a diameter of 36 mm, the support shaft 32 has a diameter of 1 mm, and a length of 20 mm.

First, the closing means 3 was placed on the disk substrate 100, and the pressure in the vicinity of the central hole 101 was reduced so that the closing means 3 and the disk substrate 100 were attracted to the rotary table 2. Then, while rotating the rotary table 2 at a low speed, an ultraviolet curable resin (manufactured by Nippon Kayaku Co., Ltd., viscosity of 500 Pas at 25 ° C.) is supplied to the outer peripheral surface of the support shaft 32 so that the resin is applied onto the disk portion 31. The resin layer 51 was formed by spreading and then spreading the resin on the disk substrate 100 by rotating the rotary table 2 at 2000 rpm for 8 seconds. Next, after the blocking means 3 was separated from the disc substrate 100, the resin layer 51 was ultraviolet-cured to form a light transmitting layer 102, and an optical disc sample was obtained.

Example 2 The closing means 3 used in Example 1 was used. That is, the closing means 3 in which the surface of the disk portion 31 was coated with resin during spin coating was used. An optical disk sample was prepared in the same manner as in Example 1 except for the above.

Example 3 An optical disk sample was prepared in the same manner as in Example 1 except that the closing means 3 having the same shape as the closing means 3 used in Example 1 and made of a polycarbonate resin was used. This closing means 3 was manufactured by an injection molding method. At the time of injection molding, polycarbonate for optical discs containing few impurities that adversely affect the surface roughness was used, and the mold temperature was 30 ° C., the resin melting temperature was 320 ° C., the mold clamping force was 490 MPa, and the injection time was 1 second.

Comparative Example 1 An optical disk sample was produced in the same manner as in Example 1 except that the stainless steel closing means produced in the same manner as in Example 1 was used except that the surface was not polished.

Comparative Example 2 An optical disk sample was manufactured in the same manner as in Example 1 except that the stainless steel closing means manufactured in the same manner as in Comparative Example 1 was used. Compared with the closing means used in Comparative Example 1, this closing means has a slightly smaller surface roughness due to cutting.

Comparative Example 3 The same shape as the closing means 3 used in Example 1 and the POM
An optical disk sample was manufactured in the same manner as in Example 1 except that the closing means 3 manufactured by shaving (polyoxymethylene resin) was used.

Evaluation Regarding the clogging means 3 used in the preparation of each of the above samples, the surface roughness of the upper surface of the disk portion 31 was measured by a surface roughness measuring instrument (Surfcom SE-30H manufactured by Tokyo Seimitsu Co., Ltd., needle: PU-DH manufactured by the same company). -10/10 μm
R, cutoff frequency 0.8 mm), and a center line average roughness Ra, a ten-point average roughness Rz, and an average inclination angle θa of the roughness were obtained. The results are shown in Table 1. The standard measurement length was 2.5 mm.

Further, with respect to each of the above samples, the defects contained in the light transmitting layer were examined by an optical microscope and a general-purpose optical disc appearance defect inspection machine (manufactured by Dr.SCHENK). With an optical microscope, the size and number of bubbles were visually quantified, and with a general-purpose optical disk appearance defect inspection machine, defect inspection was performed by image processing of CCD camera data. The existence density of bubbles in each sample is shown in Table 1. The details of the defect inspection result for each sample are shown below.

In the sample of Example 1, in the region of the radius of the light transmitting layer of 18 to 30 mm, 0 to 1 bubbles / m of bubbles having a diameter of 20 to 40 μm were observed in a part of the circumferential direction by an optical microscope.
Observed at a rate of m ² . Also, a defect corresponding to this was observed in the optical disc appearance defect inspection machine.

In the sample of Example 2, in the region of the radius of the light transmitting layer of 18 to 30 mm, 1 to 5 bubbles / mm of a bubble having a diameter of 20 to 40 μm were observed in a part of the circumferential direction by an optical microscope.
Observed at a rate of ² . Also, a defect corresponding to this was observed in the optical disc appearance defect inspection machine.

In the sample of Example 3, no bubbles could be confirmed by the optical microscope in the entire area of the light transmitting layer, and no defect was detected by the optical disc appearance defect inspection machine.

In the sample of Comparative Example 1, in the region of the radius of the light transmitting layer of 18 to 30 mm, the diameter of 2 is applied to the entire region in the circumferential direction.
Bubbles of about 0 to 40 μm were observed at a rate of 10 to 20 bubbles / mm ² . Also, a defect corresponding to this was observed in the optical disc appearance defect inspection machine.

In the sample of Comparative Example 2, bubbles having a diameter of 20 to 40 μm were observed at a rate of 5 to 10 cells / mm ² in a region of the light transmitting layer having a radius of 18 to 30 mm in the circumferential direction. . Also, a defect corresponding to this was observed in the optical disc appearance defect inspection machine.

In the sample of Comparative Example 3, in the region of the radius of the light transmitting layer of 18 to 30 mm, the diameter of 2 is applied to the entire region in the circumferential direction.
Bubbles of about 0 to 40 μm were observed at a rate of 20 cells / mm ² . Also, a defect corresponding to this was observed in the optical disc appearance defect inspection machine.

[0066]

[Table 1]

The effects of the present invention are clear from the results of the above examples. That is, by controlling the surface roughness of the closing means according to the present invention, the defects of the light transmitting layer can be significantly reduced.

The thickness of the light transmission layer was measured by a laser focus displacement meter in the pit formation area (area having a radius of 23 to 58 mm) of each sample shown in Table 1. As a result, the thickness of the light transmission layer was 100 ± 2 for all samples.
It was confirmed that the thickness unevenness was extremely small in the radial direction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a manufacturing process of a light transmission layer.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of a light transmission layer.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of a light transmission layer.

FIG. 4 is a cross-sectional view illustrating a manufacturing process of a light transmission layer.

FIG. 5 is a cross-sectional view illustrating a manufacturing process of a light transmission layer.

FIG. 6 is a cross-sectional view illustrating a manufacturing process of a light transmission layer.

7 (A) to 7 (D) are cross-sectional views showing a configuration example of the closing means.

FIG. 8 is a partial cross-sectional view showing a configuration example of an optical information medium.

[Explanation of symbols]

2 turntable 21 Protrusion 3 Closing means 31 Disc part 32 support shaft 33 convex 4 nozzles 5 coating liquid 51 resin layer 100 disk substrate 101 central hole 102 light transmitting layer 120 support substrate 121 groove 104 recording layer

Continued front page    (72) Inventor Kenji Yamaya             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. (72) Inventor Takeshi Komaki             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. F-term (reference) 5D121 AA04 EE24

Claims (4)

[Claims] 1. An information recording layer and a resin-containing light-transmitting layer are provided in this order on a disk-shaped support substrate having a central hole, and a laser beam for recording or reproducing has the light-transmitting layer. A method of manufacturing an optical information medium used so as to be incident on the information recording layer through the method, comprising: providing the information recording layer on the supporting base, forming a central hole of the supporting base, and a disc portion. By covering with the disk part of the closing means having, then supplying a coating liquid containing a radiation-curable resin onto the disk part, and then rotating the closing means and the supporting base integrally. A resin spreading step of spreading the coating liquid on the supporting substrate to form an annular resin layer, and a curing step of curing the resin layer by irradiation of radiation to form the light transmitting layer are provided. The disk with which the coating liquid contacts A method for producing an optical information medium using a closing means having a center line average roughness Ra of 100 nm or less on at least a part of the surface of the part. 2. An information recording layer and a light-transmitting layer containing a resin in this order on a disk-shaped supporting substrate having a central hole, and a laser beam for recording or reproducing has the light-transmitting layer. A method of manufacturing an optical information medium used so as to be incident on the information recording layer through the method, comprising: providing the information recording layer on the supporting base, forming a central hole of the supporting base, and a disc portion. By covering with the disk part of the closing means having, then supplying a coating liquid containing a radiation-curable resin onto the disk part, and then rotating the closing means and the supporting base integrally. A resin spreading step of spreading the coating liquid on the supporting substrate to form an annular resin layer, and a curing step of curing the resin layer by irradiation of radiation to form the light transmitting layer are provided. The disk with which the coating liquid contacts A method for manufacturing an optical information medium, which uses a closing means having a ten-point average roughness Rz of 1 μm or less on at least a part of the surface of the part. 3. An information recording layer and a resin-containing light transmitting layer are provided in this order on a disc-shaped supporting substrate having a central hole, and a laser beam for recording or reproducing has the light transmitting layer. A method of manufacturing an optical information medium used so as to be incident on the information recording layer through the method, comprising: providing the information recording layer on the supporting base, forming a central hole of the supporting base, and a disc portion. By covering with the disk part of the closing means having, then supplying a coating liquid containing a radiation-curable resin onto the disk part, and then rotating the closing means and the supporting base integrally. A resin spreading step of spreading the coating liquid on the supporting substrate to form an annular resin layer, and a curing step of curing the resin layer by irradiation of radiation to form the light transmitting layer are provided. The disk with which the coating liquid contacts A method for manufacturing an optical information medium, which uses a closing means having an average inclination angle θa of roughness of 1 ° or less on at least a part of the surface of the part. 4. The method of manufacturing an optical information medium according to claim 1, wherein the closing means is manufactured by injection molding of resin.