JPH10112073A - Sticking type optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sticking type optical information recording medium which facilitates the control of the film thickness of the transparent adhesive layer of the sticking type optical information recording medium to the film thickness uniform over the entire surface and enables the stable reproduction of the information recorded on two recording layers. SOLUTION: This sticking type optical information recording medium has a first substrate 101 including a first smooth surface and a first information surface formed with a first recording region 102 and a second substrate 105 including a second smooth surface and a second information surface formed with a recording region 106 and is formed by sticking the first substrate 101 and the second substrate 105 via an adhesive layer 108 between the first information surface and the section information surface. The first substrate 108 includes discontinuous projecting parts 103 for controlling the adhesive layer 108 to a prescribed film thickness on the inner peripheral part and outer peripheral part of the first information surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated optical information recording medium in which two substrates are laminated to form one optical information recording medium.

[0002]

2. Description of the Related Art A minute pit called a pit corresponding to recorded information is formed on one surface of a substrate, a laser beam is focused on the pit through the substrate, and the recorded information is reproduced by a change in the amount of reflected laser light. A typical optical information recording medium is a compact disk (CD).

A CD has a diameter of 120 mm and a thickness of 1.2 mm.
A pit row having a shortest pit length of about 0.9 μm is formed at a track pitch of 1.6 μm on the substrate. The linear velocity during reproduction is constant at about 1.2 to 1.4 m / s, has a recording capacity of about 650 Mbytes, and records digital data such as music and video. Hereinafter, a CD is assumed to have the above specifications, and a CD-ROM (Compact Disk-Read Only Mem
ory), Video-CD (Video-Compact Disk) and the like.

On the other hand, as a next-generation medium whose recording density is increased to about 6 to 8 times that of a CD, a DVD (Digital Versatile Dispersion) is used.
Research and development of k) is in progress. The DVD employs some new technologies to increase the recording density on the optical disk as compared with a conventional CD or the like in order to secure a large capacity.
For example, the thickness of the substrate is 0.6 mm, and the two substrates are bonded to form an optical disk having a thickness of 1.2 mm. In this case, information can be recorded on each substrate and information recorded on two recording layers from one side can be reproduced (DVD-type).
9).

FIG. 4 is a sectional view of an optical disc for explaining the structure of a conventional DVD-9. In the figure, 401 is a first transparent substrate, 402 is a first recording area, 403 is a translucent film, 404 is a second transparent substrate, 405 is a second recording area, 406 is a reflective film, and 407 is a transparent adhesive. The layer 408 is an optical pickup. This is the DVD standard draft DVD-
9 shows a single-sided reproduction type two-layer type optical disk capable of reproducing two information recording layers from one side of the optical disk.

A first recording area 402 in which information is recorded as a pit row is formed on an upper surface of a first transparent substrate 401, and reflects a part of a laser beam emitted from an optical pickup 408 and transmits the rest. Is covered with a translucent film 403. A second recording area 405 in which information is recorded as a pit row is also formed on the upper surface of the second transparent substrate 404, and is covered with a reflective film 406 that reflects most of the laser light emitted from the optical pickup 408. .

First transparent substrate 401 and second transparent substrate 4
04 is attached via a transparent adhesive layer 407. Irradiated from the optical pickup 408, the translucent film 40
The first transparent substrate 4 by the laser light reflected from
01 is reproduced from the first recording area 402. The second recording area 405 of the second transparent substrate 404 is reproduced by a laser beam emitted from the optical pickup 408, transmitted through the translucent film 403 and the transparent adhesive layer 407, and reflected by the reflection film 406. . The optical pickup 40
As for No. 8, one optical pickup is usually used, and the focus point is set to the first recording area 402 and the second recording area 405.
The two recording layers can be switched for reading depending on which of the above is set.

However, as described above, DVD-9
The thickness of the transparent adhesive layer must be strictly controlled so that the first recording area and the second recording area can be reproduced from the first transparent substrate side. The thickness of the transparent adhesive layer is such that the focus point can be switched in each of the first recording area and the second recording area, that there is no crosstalk between both recording areas, and that the substrate thickness is 0.6 mm or less. It is determined by, for example, reducing the influence of aberration due to the displacement. Therefore, the deviation of the film thickness of the transparent adhesive layer per disk circumference is several μm, and the deviation of the entire disk circumference is several tens μm
m must be controlled.

Conventionally, in order to control the thickness of the transparent adhesive layer, application conditions of an ultraviolet curing resin for forming the transparent adhesive layer,
For example, it is necessary to manage a number of parameters such as the viscosity of the ultraviolet curable resin, the application amount, the application start position, the number of revolutions, the temperature, the humidity, and the like, and it is not possible to make the film thickness uniform over the entire surface of the optical disk. It was very difficult.

In order to solve the above problem, a method of mixing a spacer member into an adhesive, bonding two substrates, and equalizing the distance between the two substrates is disclosed in Japanese Patent Application Laid-Open No. Sho 62-28.
No. 1137 discloses this. An optical disc in which two substrates are bonded together via a sheet having a predetermined thickness is disclosed in Japanese Utility Model Laid-Open No. 63-47419.

[0011]

However, in the method of mixing the spacer member into the adhesive, the price of the adhesive becomes expensive, and the setting of the application conditions is more difficult than in the case of the conventional adhesive alone. And other problems. Furthermore, D
In the case of VD-9, when reproducing the second recording area, reproduction is performed through the adhesive layer. Therefore, unless a space member having a refractive index exactly the same as the refractive index of the adhesive is selected, irregular reflection or refraction of the reproduction laser light occurs at the adhesive layer, and the second recording area cannot be reproduced. there were.

Further, in a method of controlling the thickness between two substrates by using a sheet having a predetermined thickness, it is difficult to apply the sheets uniformly, and it is difficult to control the thickness of the adhesive layer to be attached to the sheets and the substrate. Unless the film thickness is strictly controlled, there is a problem that the thickness between the two substrates cannot be made uniform.

The present invention has been made to solve such a conventional problem, and it is easy to uniformly control the thickness of a transparent adhesive layer in a bonded optical information recording medium over the entire surface. It is an object of the present invention to provide a laminated optical information recording medium capable of stably reproducing information recorded in two recording layers.

[0014]

For this purpose, according to the first aspect of the present invention, there is provided a first substrate having a first smooth surface and a first information surface on which a recording area is formed; A second substrate having a smooth surface and a second information surface on which a recording area is formed, wherein the first information surface and the second information surface have an adhesive layer interposed therebetween. In a bonded optical information recording medium in which a first substrate and the second substrate are bonded to each other, the first substrate is provided with the adhesive layer on an inner peripheral portion and an outer peripheral portion of the first information surface in a predetermined manner. It is characterized by having discontinuous projections for controlling the film thickness.

According to the second aspect of the present invention, a first substrate having a first smooth surface and a first information surface on which a recording area is formed, and a second smooth surface and a recording area are formed. And a second substrate having a second information surface,
In the bonded optical information recording medium in which the first substrate and the second substrate are bonded via an adhesive layer between the information surface and the second information surface, the first substrate is An inner peripheral portion of the first information surface is provided with a discontinuous first protrusion for controlling the adhesive layer to a predetermined thickness, and the second substrate is provided on an outer peripheral portion of the second information surface; And a discontinuous second projection for controlling the adhesive layer to a predetermined thickness.

According to the third aspect of the present invention, a first substrate having a first smooth surface and a first information surface on which a recording area is formed, and a second smooth surface and a recording area are formed. And a second substrate having a second information surface,
In the bonded optical information recording medium in which the first substrate and the second substrate are bonded via an adhesive layer between the information surface and the second information surface, the first substrate is A first information surface provided with discontinuous first protrusions for controlling the thickness of the adhesive layer to a predetermined thickness on an inner peripheral portion and an outer peripheral portion of the first information surface, wherein the second substrate has the second information surface; A discontinuous second portion for controlling the adhesive layer to a predetermined thickness on the inner peripheral portion and the outer peripheral portion thereof.
Wherein the first projection and the second projection are arranged at different positions when the first substrate and the second substrate are bonded to each other. It is.

According to the bonding type optical information recording medium of the present invention, the bonding is performed.
Discontinuous projections having a height equal to the specified thickness of the adhesive layer were formed on one or both of the inner and outer peripheral portions of one or both of the substrates. Therefore, in the bonding step using the adhesive layer, the thickness of the adhesive layer is mechanically determined by the height of the protrusion, so that the adhesive layer is uniformly formed with a predetermined thickness over the entire surface of the medium. Can be.

Further, since each of the projections is formed discontinuously, when the adhesive is spin-coated to form an adhesive layer, the flow of the adhesive is not obstructed, and the adhesive is applied over the entire surface of the medium. The agent can be spread evenly.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a laminated optical information recording medium according to an embodiment of the present invention. FIG. 1 is a schematic diagram showing a cross-sectional structure of a bonded optical information recording medium of the present invention. In the figure, 101 is a first transparent substrate, 102 is a first recording area, 103 is a protrusion, 1
04 is a translucent film, 105 is a second transparent substrate, 106 is a second recording area, 107 is a reflective film, and 108 is a transparent adhesive layer.

In FIG. 1, a first transparent substrate 101 and a second transparent substrate 105 have an outer diameter of 120 mm and an inner diameter of 15 m.
m, a resin substrate made of polycarbonate resin, acrylic resin or the like having a thickness of 0.6 mm and transparent to the wavelength of the reproduction laser beam. The first transparent substrate 101 has a first recording area 102 in which information is recorded as a pit row on the bonding surface side, and the first recording area 102 emits a part of the reproduction laser beam. It is covered with a translucent film 104 made of a metal, an inorganic dielectric or the like that reflects and transmits the rest.

The second transparent substrate 105 has, on the bonding surface side, a second recording area 106 in which information is recorded as a pit row. Reflective film 107 made of metal or the like that reflects most of the light
Covered with. Then, the first transparent substrate 101 and the second
The transparent substrate 105 is bonded via a transparent adhesive layer 108 made of an ultraviolet curable resin or the like so that both the first recording area 102 and the second recording area 106 face inward.

The bonded optical information recording medium of the present embodiment has an inner peripheral portion and an outer peripheral portion of the first transparent substrate 101 or an inner peripheral portion of the first transparent substrate 101 and the second transparent substrate 105. Either the outer peripheral portion, or the inner peripheral portion or the outer peripheral portion of the first transparent substrate 101 and the second transparent substrate 105 has a height equivalent to the predetermined thickness of the transparent adhesive layer 108, and each of them has The projection 3 is provided continuously. The protrusion 3 is provided to determine the distance between the first recording area 102 of the first transparent substrate 101 and the second recording area 106 of the second transparent substrate 105, that is, the thickness of the transparent adhesive layer 108. It was done.

The thickness of the transparent adhesive layer 108 is such that the focus point can be switched in each of the first recording area and the second recording area, that there is no crosstalk between the two recording areas, and that the substrate thickness is It is determined by reducing the influence of aberration due to deviation from 0.6 mm. In this embodiment, considering the above conditions, the transparent adhesive layer 108
Was set to 50 μm.

In the case of this embodiment, if the height of the projection 103 is made equal to the predetermined thickness of the transparent resin layer, when the first transparent substrate 101 and the second transparent substrate 103 are bonded, The protrusion 103 serves as a spacer, and the transparent adhesive layer 108 is formed uniformly over the entire surface of the disk within a predetermined thickness.

FIG. 2 is a schematic view showing one embodiment of the first transparent substrate of the bonded optical information recording medium of the present invention.
The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. In the figure, 201 is a center hole, 202 is a clamp area, 2
03 is an inner mirror surface part, and 204 is an outer mirror surface part.

The first transparent substrate 101 is arranged in order from the inner periphery.
A central hole 201 for insertion into the rotating shaft of the turntable of the recording / reproducing apparatus, a clamp area 202 where the clamp unit of the recording / reproducing apparatus chucks, and information inside the lead-in area of the first recording area 102 are recorded. An inner mirror surface portion 203 that is not provided, a first recording area 102 where information is formed as pits, and an outer mirror surface portion 204 where information outside the lead-out area of the first recording area 102 is not recorded. ing.

In this embodiment, the clamp area 202, the inner peripheral mirror 203, and the outer mirror 20 of the first transparent substrate 101 are formed.
The structure was such that the protrusions 103 having a height of 50 μm were provided discontinuously in three regions 4. In this case, it is not necessary to provide the projection 103 on the second transparent substrate 105 to be bonded shown in FIG. In the case where a projection is provided on the second transparent substrate 105, the projection is formed so as to be arranged at a different position when the projection is bonded to the projection 103 of the first transparent substrate 101. In this case, the disk strength after bonding is higher than in the case where a projection is provided on the first transparent substrate 101.

Further, as another embodiment, a projection 103 is formed at one or two of a clamp area 202, an inner peripheral mirror 203, and an outer mirror 204 of the first transparent substrate 101 to form a second transparent substrate. A clamp area 202 of the substrate 105;
A configuration may be adopted in which the projections are provided at positions where the projections 103 are not formed on the first transparent substrate 101 in the inner mirror surface portion 203 and the outer mirror surface portion 204. In addition, FIG. 2 illustrates a trapezoidal shape as the protrusion 103, but is not limited to this shape, and may have a shape such as a conical shape, a cylindrical shape, or a prismatic shape. However, in order not to hinder the flow of the adhesive at the time of applying the adhesive for forming the transparent adhesive layer 108, each of the protrusions 103 needs to be formed discontinuously instead of being a wall.

The bonded optical information recording medium according to the first embodiment of the present invention is manufactured as described below. The first transparent substrate 101 and the second transparent substrate 105 are formed by an injection molding machine using a stamper in which a first recording area 102 and a second recording area 106 are formed. At this time, a portion corresponding to the position where the projection 103 of the mold or stamper to be attached to the injection molding machine is formed has 50
The protrusion 1 is formed so that the protrusion 103 having a height of μm is formed.
Form 03 is formed. In particular, the projection 10
When forming the mold No. 3, a stamper on which the first recording area 102 or the second recording area 106 is formed is manufactured from a glass master by plating or the like, and then a method such as dry etching using a mask or the like is used. Then, a method of forming the mold of the protrusion 103 is adopted. As described above, the first transparent substrate 101 and the second transparent substrate 105 on which the protrusions 103 are formed
Is prepared.

Next, the recording area 1 of the first transparent substrate 101
02, AlxNy, metal such as Au, Al,
A translucent film 104 made of an inorganic dielectric such as SixNy is formed by a sputtering method or the like. Further, a reflective film made of a metal such as Al or Au is formed by a sputtering method or the like so as to cover the recording area 106 of the second transparent substrate 105.

The first transparent substrate 101 on which the translucent film 104 is formed (the second transparent substrate 10 on which the reflective film 107 is formed)
5) place the translucent film 10 on the turntable of the spinner device.
4 is fixedly arranged so as to face upward, and an ultraviolet curable resin solution as an adhesive is dropped on the semi-transparent film 104 of the first transparent substrate 101, and the reflection film 1 of the second transparent substrate 105 is formed thereon.
07 (the translucent film 104 of the first transparent substrate 101) is overlapped with the adhesive. Subsequently, the turntable is rotated at a high speed to diffuse the adhesive over the entire surface of the disk, and further, scatter excess adhesive. At this time, since each projection 103 is formed discontinuously, the projection 103 does not hinder the flow of the adhesive when the adhesive is rotationally diffused.

Further, as the turntable continues to rotate, the weight of the second transparent substrate 105 (first transparent substrate 101) and the centrifugal force generated by the rotation of the turntable cause
The first transparent substrate 101 and the second transparent substrate 105 are in contact with each other at the projection 103. Therefore, the transparent adhesive layer 1 between the first transparent substrate 101 and the second transparent substrate 105
08 has a thickness of 50 μm, which is equivalent to the height of the protrusion 103. Then, by stopping the rotation of the turntable and irradiating the ultraviolet rays, the ultraviolet curable resin is cured, and the transparent adhesive layer 108 is formed with a thickness of 50 μm which is equal to the height of the protrusion 103.

The thickness distribution of the transparent adhesive layer 108 of the laminated optical information recording medium of the present invention produced as described above was measured. FIG. 3 is a characteristic diagram showing a result of measuring a film thickness distribution of the transparent adhesive layer of the bonded optical information recording medium of the present invention. As a comparison, the thickness of the transparent adhesive layer of the laminated optical information recording medium manufactured using a conventional transparent substrate having no projection 103 and controlling the thickness of the transparent adhesive layer only by applying the adhesive. The results of measuring the distribution are also shown.

As is clear from FIG. 3, the thickness distribution of the transparent adhesive layer 108 of the bonded optical information recording medium of the present invention has a value of about 50 μm corresponding to the height of the projection 103 over the entire surface of the disk. 50 μm ± over the entire surface
It can be seen that it is within the range of 10%. On the other hand, in the conventional example using the transparent substrate having no projection 103 as in the present invention, the thickness of the transparent adhesive layer is increased from the inner periphery to the outer periphery, and the deviation was not within ± 10%.

[0035]

According to the laminated optical information recording medium of the present invention, it is easy to uniformly control the thickness of the transparent adhesive layer over the entire surface, and the recording is stably performed on the two recording layers. It is possible to provide a bonded optical information recording medium capable of reproducing existing information.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross-sectional structure of a bonded optical information recording medium of the present invention.

FIG. 2 is a schematic view showing one embodiment of a first transparent substrate of the bonded optical information recording medium of the present invention.

FIG. 3 is a characteristic diagram showing a result of measuring a film thickness distribution of a transparent adhesive layer of the bonded optical information recording medium of the present invention.

FIG. 4 is a cross-sectional view of an optical disc for explaining the structure of a conventional DVD-9.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 1st transparent substrate 102 1st recording area 103 Projecting part 104 Translucent film 105 2nd transparent substrate 106 2nd recording area 107 Reflective film 108 Transparent resin layer 201 Center hole 202 Clamp area 203 Inner peripheral mirror part 204 Outer mirror portion 401 First transparent substrate 402 First recording region 403 Translucent film 404 Second transparent substrate 405 Second recording region 406 Reflective film 407 Transparent resin layer 408 Optical pickup

Claims (3)

[Claims] A first smooth surface and a first area having a recording area formed thereon;
And a second substrate having a second smooth surface and a second information surface on which a recording area is formed. In a bonded optical information recording medium in which the first substrate and the second substrate are bonded to each other via an adhesive layer between the second information surface and the second information surface, the first substrate has the first information A laminated optical information recording medium, comprising discontinuous protrusions for controlling the adhesive layer to a predetermined thickness on inner and outer peripheral portions of the surface. 2. A method according to claim 1, wherein a first smooth surface and a recording area are formed.
And a second substrate having a second smooth surface and a second information surface on which a recording area is formed. In a bonded optical information recording medium in which the first substrate and the second substrate are bonded to each other via an adhesive layer between the second information surface and the second information surface, the first substrate has the first information A second protrusion provided on an inner peripheral portion of the surface for controlling the adhesive layer to have a predetermined thickness, and the second substrate is provided with an adhesive layer on an outer peripheral portion of the second information surface. A laminated optical information recording medium, comprising a discontinuous second projection for controlling the thickness of the recording medium to a predetermined thickness. 3. A first device having a first smooth surface and a recording area formed thereon.
And a second substrate having a second smooth surface and a second information surface on which a recording area is formed. In a bonded optical information recording medium in which the first substrate and the second substrate are bonded to each other via an adhesive layer between the second information surface and the second information surface, the first substrate has the first information An inner peripheral portion and an outer peripheral portion of the surface are provided with discontinuous first protrusions for controlling the adhesive layer to a predetermined thickness, and the second substrate is an inner peripheral portion of the second information surface. And an outer peripheral portion having a discontinuous second protrusion for controlling the adhesive layer to a predetermined film thickness, wherein the first protrusion and the second protrusion are formed of the first substrate and the second protrusion. A bonded optical information recording medium, which is arranged at a different position when a second substrate is bonded.