JP2003257085A - Optical information medium and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which is nearly free from a defect, has a large capacity and can be manufactured with satisfactory productivity and to provide a method for manufacturing the same. <P>SOLUTION: In the method for manufacturing the optical information medium which has at least a reproducing layer for information and a light transmission layer on a substrate and wherein a laser beam is made incident from the light transmission layer side to perform recording or reproduction of information, the substrates 1 and 2 having projecting and recessed parts 1a and 2a formed on the surfaces thereof, respectively, are prepared [(a)], the substrates 1 and 2 are stuck to each other so that the rear surfaces thereof face each other by using a UV curing resin as an adhesive material and the resin is irradiated with UV to be cured [(b)]. Recording layers 3 and 4 are formed on the surfaces of both the substrates [(c), (d)], the light transmission layers 5 and 6 are formed thereon [(e), (f)]. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information medium for recording / reproducing information by irradiating a laser beam and a method for manufacturing the same, and more particularly to an optical information medium having at least an information recording layer and a light transmitting layer on a substrate. The present invention relates to an optical information medium that reproduces information, or records and reproduces information by irradiating a laser beam from the transmission layer side, and a manufacturing method thereof.

[0002]

2. Description of the Related Art As one means for improving the areal recording density of an optical disc, which is one of optical information media, the numerical aperture (NA) of an objective lens for converging laser light for recording / reproducing information is used. ) Is known to be high. By increasing the NA, the laser beam focused on the disk is narrowed, so that it is possible to record / reproduce information with higher density. The NA used to play conventional compact discs (CD) was 0.45,
Digital versatile disk (DVD)
An optical head with NA = 0.6 is used to reproduce.

Further, in recent years, an optical head having an NA increased to 0.8 or higher has been proposed. When the NA is increased, there arises a problem that an allowable amount of aberration caused by an angle (tilt angle) at which the substrate surface is deviated from the optical axis of the focused laser beam becomes small. Therefore, when the NA is high, it is desirable that the substrate thickness is as thin as possible.
The thickness of the substrate, which was m, is 0.6 mm for DVD. NA
In case of increasing to 0.85 or more, after forming the optical information recording layer on the substrate, the light transmission layer having a thickness of about 0.1 mm is formed,
A method of recording / reproducing information from the light transmitting layer side is used.

In order to further increase the capacity, it is effective to multiplex the disks in the thickness direction. In this example, the incident surface of the laser light is the same and the thickness is 10 to 30.
A so-called two-layer medium is known in which two optical information media are formed through a transparent intermediate layer of μm. However, in this case, there is a problem that it is difficult to form the intermediate layer in the medium in which the laser is incident from the light transmitting layer side. Further, in order to record / reproduce information layers existing on the far side from the incident surface, it is necessary to irradiate laser light through the optical information layer and the intermediate layer located on the side closer to the incident surface. There is a problem that it is difficult to improve the characteristics. In addition, since the optical information layer on the side closer to the incident surface requires a certain transmittance (for example, 50% or more),
There is a problem that it is difficult to secure both the transmittance and the characteristics. Therefore, the capacity that can be realized by the two-layer medium is
The capacity of the single-layer medium was 1.5 times, not twice the capacity.

As a means for multiplexing disks in the thickness direction while ensuring the capacity of one layer, a method of bonding two optical information media having one recording layer is known. 4A to 4D are cross-sectional views in order of the steps, showing the manufacturing method. First, as shown in FIG. 4A, the recording layers 3 and 4 are formed on the respective surface sides of the substrates 1 and 2. And FIG.
As shown in (b), the recording layers are laminated so that the recording layers face each other back to back and the two substrates are bonded together. Adhesion using a pressure sensitive adhesive sheet or an ultraviolet curable resin, or hot melt has been used as a means for bonding. Here, when the adhesive sheet or hot melt is used, it is necessary to press the substrate from the back surface side. The bonded substrate thus formed is irradiated with laser light 9 from the back side of the substrate to record / reproduce information on / from each recording layer 3, 4. With this method,
It is possible to realize twice the recording capacity of a single-layer medium. Also, by forming two recording layers on each substrate, it is possible to realize a maximum capacity of about three times that of a single-layer medium.

[0006]

When the NA of the objective lens is small, that is, when the laser light is incident from the back surface side of the substrate, as shown in FIG. It is possible to attach using an adhesive sheet. However, the NA becomes large, and for an optical information medium that records / reproduces information via the light transmission layer,
The conventional bonding method has the following problems. It is necessary to pressurize the disc in bonding using hot melt or adhesive sheet, and in the medium such as the conventional DVD where light is incident from the backside of the substrate, the backside of the substrate is pressed. For information media, it is necessary to pressurize the light transmissive layer. However, the light transmitting layer has a thickness of only about 100 μm and is easily scratched when pressure is applied. The optimum thickness of the light transmission layer is
Since it is determined by NA, a cover layer thickness of about 100 μm is inevitable for an optical head with NA = 0.85, and this cannot be increased. When the laser is incident from the backside of the substrate, the beam diameter on the backside of the substrate is large, so scratches on the light-incident surface do not pose a major problem, but information is recorded / reproduced by an optical head with a high NA through the light-transmitting layer. In this case, since the beam diameter on the surface of the light transmitting layer becomes small, scratches and dust on the light transmitting layer cause serious problems.

On the other hand, when the bonding is performed by using an ultraviolet curable resin, a disc having a recording layer, a reflective layer, such as a phase change optical disc, or a read-only disc having two reflective layers is formed. With respect to a two-layer medium, ultraviolet rays are reflected or absorbed by the recording layer and the reflective layer, and therefore, the ultraviolet curable resin does not reach a sufficient intensity of light, and the resin becomes uncured, resulting in a reliability problem. There is no pasting possible. It is not impossible to bond with anaerobic resin, but it takes time to cure,
Mass productivity is impaired. An object of the present invention is to solve the above-mentioned problems of the prior art, and an object thereof is to provide a large-capacity optical information medium which can be manufactured with few defects and high productivity, and a manufacturing method thereof. Is to

[0008]

In order to achieve the above-mentioned object, according to the present invention, two substrates having at least one information recording layer and a light transmitting layer on the front surface side are bonded on the back surface side. An optical information medium for recording or reproducing information by entering a laser beam from the light transmitting layer side, wherein the substrates are bonded to each other by a photocurable adhesive material. , Are provided. And, preferably, the thickness of each substrate is 0.45 mm or more and 0.55 m.
m or less. In addition, the film thickness of one layer, preferably, the light transmission layer is set to 80 μm or more and 120 μm or less.

Further, in order to achieve the above object, according to the present invention, two substrates having at least one information recording layer and a light transmitting layer on the surface side are bonded together, and the light transmitting layer side A method of manufacturing an optical information medium which records or reproduces information by irradiating laser light from (1);
Manufacture of an optical information medium comprising (2) a step of forming at least one information recording / recording layer, and (3) forming a light transmitting layer on the recording / recording layer. A method is provided. Then, preferably, an ultraviolet curable resin is used as the adhesive. Then, in the curing process, the bonding can be performed using only the weight of the substrate.

[Operation] In the present invention, first of all,
Bond the backsides of the boards together. Since nothing that blocks light is formed on the substrate, highly reliable bonding using an ultraviolet curable resin is possible. After that, the information recording layer is formed by the sputtering method or the like, and finally the light transmitting layer is formed. Since it is not necessary to pressurize the light transmitting layer after forming the light transmitting layer, a large-capacity optical information medium with few defects can be provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings. [First Embodiment] FIGS. 1A to 1C are cross-sectional views in order of the processes, showing a first embodiment of the present invention. First, the substrates 1 and 2 having the irregularities 1a and 2a formed on the substrate surface side are prepared [FIG.
(a)], The back surfaces of the substrates are bonded together with a photocurable resin (not shown) interposed therebetween (FIG. 1 (b)). Then, ultraviolet irradiation is performed to cure the photocurable resin that is the adhesive.
At this time, it is preferable to use the weight of the substrate for bonding without pressing the substrate surface. Here, the irregularities 1a and 2a formed on the surfaces of the substrates 1 and 2 are prepits or spiral grooves. Next, the recording layer 3 is formed on the surface of the substrate 1 by using a vapor deposition method, a sputtering method, or the like [FIG.
(c)]. The recording layer is either a read-only type, a write-once type, or a rewritable type. Depending on the recording type, a reflective film or a material layer for additional writing or rewriting, or a laminated film of a reflective film and a material layer. Is formed. Next, the recording layer 4 is also formed on the front surface side of the substrate 2 [FIG. 1 (d)]. Recording layer 3
The recording layer 4 and the recording layer 4 do not have to be the same type of medium. That is, one may be a read-only type and the other may be a write-once type. Next, the light transmitting layer 5 is formed on the recording layer 3 of the substrate 1 [FIG. 1 (e)], and then the light transmitting layer 6 is formed on the recording layer 3 of the substrate 2.
Are formed [FIG. 1 (f)]. NA of the light transmitting layer is 0.85
When it is about the degree or more, it is desirable to set it to 80 to 120 μm. In the above description of the present embodiment, the light transmitting layer was formed after forming the recording layers on both sides,
The recording layer and the light transmitting layer may be formed on one substrate and then the recording layer and the light transmitting layer may be formed on the other substrate.

As described above, the recording layer is a read-only type,
Although it is either a write-once type or a rewritable type, the read-only type is composed of a reflective film covering the concave and convex pits. As the reflective film, an Au film, an Al film or an alloy film thereof is used. In the case of the write-once type, an alloy material of a low melting point metal such as Te, Bi, Se, or Sn or a dye material that has absorption characteristics at the laser wavelength used is applied thinly on the substrate on which the reflective film is formed. To be done. In the rewritable type, in a magneto-optical disk, a structure in which a rare earth metal such as Tb, Gd, Dy, and Ho and an alloy thin film of a transition metal such as Fe, Co, and Ni is sandwiched between transparent protective films such as SiN, In the phase change medium, chalcogenide thin films such as GeSbTe, InSbTe, AgInSbTe, SbTe are used. Conventionally, 0.6 mm thickness or 1.
Although a substrate having a thickness of 2 mm has been used, a substrate having a thickness of 0.45 to 0.55 mm is preferably used in this embodiment. Especially when forming one recording layer on each substrate, approximately 0.5 mm
It is desirable to use a thick substrate. This is because the thickness of each light transmission layer is about 100 μm. When using a 0.6 mm substrate as in the past, the total thickness is
It becomes 1.4 mm, which increases the load on the motor during high-speed rotation and increases power consumption. vice versa
A substrate having a thickness of 0.4 mm or less causes a problem in the flatness of the substrate, which makes it difficult to perform good recording / reproducing.

[Second Embodiment] FIG. 2 shows a second embodiment of the present invention.
4A to 4D are cross-sectional views in order of the processes, showing the embodiment of. In this embodiment, the steps of the first embodiment shown in FIGS. 1A to 1D are used as they are. 1 (a)-
After forming the recording layers 3a and 4a on the surfaces of the substrates 1 and 2 through the process shown in (d) [FIG. 2 (a)], the photocuring property is applied to each of the recording layers 3a and 4a. Intermediate layers 7 and 8 are formed using a resin or the like [FIG. 2 (b)]. Then, after forming the prepits or grooves, the recording layers 3b and 4b are formed on the respective substrates [FIG. 2 (c)]. Like the first layer, the second recording layer is either a read-only type, a write-once type, or a rewritable type, and the material and structure thereof are also the same as those of the first layer. Further, the first layer and the second recording layer do not have to be substrate recording layers of the same kind. Next, the recording layer 3b of the substrate 1
The light transmitting layer 5 is formed on the upper surface, and the light transmitting layer 6 is formed on the recording layer 4b of the substrate 2 [FIG. 2 (d)].

In the above embodiment, the recording layers 3b and 4b are used.
Although the light transmitting layers 5 and 6 are formed after forming the above, the recording layer and the light transmitting layer may be formed on one substrate and then the recording layer and the light transmitting layer may be formed on the other substrate. . Further, without processing into the state shown in FIG. 2A, after forming four layers of recording layer / intermediate layer / recording layer / light transmitting layer on one substrate, recording layer / intermediate layer on the other substrate / Forming the intermediate layer / recording layer / light transmitting layer In the present embodiment, 0.4 to 0.5
It is preferable to use a substrate having a thickness of mm, and more preferably,
It is to use a substrate with a thickness of approximately 0.45 mm. This is because the thickness of the light-transmitting layer is about 100 μm and an intermediate layer with a film thickness of 30 μm, for example, is added. Therefore, when the substrate of 0.6 mm is used, the total thickness is about 1.5 mm. Because it will be.

[Third Embodiment] FIG. 3 shows a third embodiment of the present invention.
4A to 4D are cross-sectional views in order of the processes, showing the embodiment of. In this embodiment, the recording layer 3 and the light transmitting layer 5 are formed in advance on the substrate 1 before the substrates are bonded to each other. A substrate 1 on which a recording layer 3 and a light transmission layer 5 are formed and a substrate 2 on which unevenness 2a is formed on the substrate surface are prepared [FIG.
(a)] Then, the back surfaces of the substrates are bonded together with a photo-curable resin (not shown) interposed therebetween (FIG. 3 (b)). And the substrate 2
Ultraviolet irradiation is performed from the side to cure the photocurable resin as the adhesive. Next, the recording layer 4 is formed on the substrate 2 [see FIG.
(c)] Then, the light transmission layer 6 is formed on the recording layer 4 [FIG. 3 (d)].

In the above-described third embodiment, only one recording layer is formed on the substrate 1, but one substrate is previously recorded layer / intermediate layer / recording layer / light. A transparent layer and two recording layers may be formed. In that case, after bonding the substrates, the recording layer / intermediate layer /
A recording layer / light transmitting layer and two recording layers are formed.

[0017]

EXAMPLES Next, examples of the present invention will be described. [Example 1] Two substrates having a thickness of 0.5 mm, which had spirally formed pre-pit irregularities on the surface in advance, were bonded together by an ultraviolet curable resin so that the back surfaces face each other.
SD-661 manufactured by Dainippon Ink Co., Ltd. was used for bonding. SD
Not limited to -661, any ultraviolet curable resin can be used without any particular problem. After bonding, Al was deposited on the surface of each substrate by sputtering to a thickness of 150 nm, and a polycarbonate film having a thickness of 100 μm was adhered with an ultraviolet curable resin to form a light transmitting layer.

The pits (recesses) formed on the substrate have a shortest length of 0.18 μm and a radial pit spacing of 0.32 μm, and the capacity is about 25 GB in each layer and 50 GB on both sides. After forming the light transmitting layer, each layer was evaluated using an optical head with a wavelength of 405 nm and NA = 0.85, and it was confirmed that good characteristics were realized without burst errors.

[Comparative Example 1] Using the same substrate as in the above-mentioned example, an Al film having a thickness of 150 nm was formed on each substrate to form a light transmitting layer, and then bonding with an ultraviolet curable resin was tried.
Even after the UV irradiation, each substrate easily peeled off,
I couldn't bond them together.

[Comparative Example 2] Using the same substrate as in the above-mentioned example, an Al film having a thickness of 150 nm was formed on each substrate to form a light transmitting layer, and then bonding by hot melt was tried. After the bonding, each substrate was tried to be peeled, but it was difficult to peel the substrates, and it was found that the bonding itself could be performed well. However, as a result of evaluating each layer, it was confirmed that a large number of burst errors of about 50 per 1 mm ² were generated due to the scratches generated at the time of pressing.

[Embodiment 2] Two polycarbonate substrates having a thickness of 0.5 mm and having a spiral groove (guide groove) with a groove depth of 40 nm and a pitch of 0.64 μm formed in advance on the surface are UV-cured on the back surfaces. It was pasted with a resin. After that, on the surface of each substrate, Al reflection film, ZnS-SiO ₂ protective film, GeSbTe
A phase change recording layer and a ZnS-SiO ₂ protective film were sequentially formed by sputtering, and a polycarbonate film having a thickness of 100 μm was adhered using an ultraviolet curable resin to form a light transmitting layer. L / G (Land / Groove) recording was performed using an optical head with a wavelength of 400 nm and NA = 0.85, and as a result of evaluation, it was confirmed that a large capacity of 25 GB on each layer and 50 GB on both sides could be realized. did it.

[0022]

As described above, according to the present invention, the recording layer and the light transmitting layer are formed on the surface of the substrate after the back surfaces of the substrate are adhered to each other with the photo-curing resin. It is possible to manufacture a small amount of large-capacity optical information medium with high productivity and high reliability. Further, in the present invention, 0.
Since a substrate with a thickness of 4 to 0.55 mm is used, it is possible to realize a lightweight and large-capacity optical information medium without impairing mechanical strength, and realize high-speed rotation of the disk with low power consumption and transfer. It is possible to improve the rate.

[Brief description of drawings]

1A to 1C are cross-sectional views in order of a process, illustrating a manufacturing process of an optical information medium according to a first embodiment of the invention.

2A to 2D are cross-sectional views in order of the steps, for explaining the steps for manufacturing the optical information medium according to the second embodiment of the invention.

3A to 3C are cross-sectional views in order of the steps, for explaining the steps for manufacturing the optical information medium according to the third embodiment of the invention.

4A to 4C are cross-sectional views in order of the steps, for explaining the conventional steps for manufacturing an optical information medium.

[Explanation of symbols]

1, 2 substrate 1a, 2b unevenness 3, 3a, 3b, 4, 4a, 4b Recording layer 5, 6 Light transmission layer 7, 8 Middle layer 9 laser light

Claims (8)

[Claims] 1. A substrate comprising at least one information recording layer and a light transmission layer on the front surface side is bonded to each other on the back surface side, and laser light is incident from the light transmission layer side to record information. An optical information medium for reproduction, wherein the substrates are attached to each other with a photo-curable adhesive material. 2. The thickness of each substrate is 0.40 mm or more and 0.5.
The optical information medium according to claim 1, which is 5 mm or less. 3. The thickness of the light transmitting layer is 80 μm or more 1
It is 20 micrometers or less, The 1 or 2 characterized by the above-mentioned.
The optical information medium described in. 4. Two substrates, each having at least one information recording layer and a light transmission layer on the front surface side, are bonded together,
A method for manufacturing an optical information medium, in which laser light is incident from the light transmitting layer side to record or reproduce information, comprising: (1) a step of bonding two substrates to each other with adhesives on their back surfaces; A method of manufacturing an optical information medium, comprising: a step of forming at least one information recording layer; and (3) a step of forming a light transmitting layer on the recording layer. 5. The method according to claim 4, wherein at least one recording layer and a light transmitting layer are previously formed on the surface of one of the substrates, prior to the step (1). Manufacturing method of optical information medium. 6. The method for manufacturing an optical information medium according to claim 4, wherein an ultraviolet curable resin is used as the adhesive material. 7. The method for manufacturing an optical information medium according to claim 4, wherein the third step is a step of adhering a resinous film. 8. The method for manufacturing an optical information medium according to claim 4, wherein the third step is a step of adhering a polycarbonate film with a photocurable resin. .