WO2000072318A1

WO2000072318A1 - Optical disk and production method therefor

Info

Publication number: WO2000072318A1
Application number: PCT/JP2000/003327
Authority: WO
Inventors: Takeshi Yamasaki; Tomomi Yukumoto; Toshiyuki Kashiwagi
Original assignee: Sony Corporation
Priority date: 1999-05-24
Filing date: 2000-05-24
Publication date: 2000-11-30
Also published as: AU4948900A; JP2003091868A

Abstract

An optical disk consisting of a multi-layer structure in which a substrate signal layer is formed on a substrate, and at least one composite layer consisting of an intermediate layer and a signal layer is further formed on the substrate signal layer, wherein the intermediate layer consists of an ultraviolet-curable resin layer and an adhesion sheet layer.

Description

Specification

Optical disc and method of manufacturing the same

Technical field

The present invention relates to an optical disk having a multilayer structure in which a plurality of recording layers or signal layers are stacked and recording or reproduction is performed on each layer by changing the focal position of a laser beam.

Background art

In the case of an optical disk in which a plurality of recording layers or signal layers are stacked and the focus position of the laser beam is changed to perform recording or reproduction on each layer, that is, an optical disk having a multilayer structure, Conventionally, as an intermediate layer between a recording layer or a signal layer and another recording layer or a signal layer, an ultraviolet curable resin, that is, a UV resin layer has been used.

For example, in the case of a laminated DVD (Digital Versatile Disc) two-layer disc, an intermediate layer is formed by laminating two discs with a signal layer or recording layer formed on one side of the disc substrate. It is composed of:

However, in the above-described method in which two disk substrates are bonded to each other to form a multilayer structure, the intermediate layer itself does not have a concavo-convex shape or a guide groove serving as a signal layer. It is not possible to stack on top of each other.

In the case where the signal layer is formed of an ultraviolet-curable polymer or an ultraviolet-curable resin, fine irregularities or the like constituting the signal layer are transferred using a stamper. At this time, the stamper and the disk substrate are used. In the meantime, the above-mentioned UV-curable polymer or UV-curable resin is filled or applied, and after laminating, it is cured by irradiating ultraviolet rays.

UV light is emitted from the stamper or disk substrate side. Either one needs to be able to transmit ultraviolet light. However, it is very difficult to form a transparent absorber that transmits ultraviolet light, and furthermore, the productivity is remarkably reduced. Further, when curing is performed by irradiating ultraviolet rays from the disk substrate side, there are problems that the material used for the signal layer is limited or the film thickness cannot be increased. Further, there is a problem that the transmittance of ultraviolet rays is reduced according to the number of layers.

The present invention has been made in view of the above-described problems, and has been made in consideration of the above-described problem. The task is to provide optical discs.

Disclosure of the invention

In order to solve the above problems, an optical disc of the present invention has a substrate signal layer formed on a substrate, and at least one or more composite layers including an intermediate layer and a signal layer are formed on the substrate signal layer. The intermediate layer is composed of a UV-curable resin layer and an adhesive sheet layer.

It is assumed that the ultraviolet curable resin layer has an uneven shape or a guide groove which forms a data recording signal.

In this way, by stacking a plurality of recording layers or signal layers and changing the focal position of the laser beam, the productivity of a multi-layered optical disc that performs recording or reproduction on each layer is improved, and α.

□ α can be improved.

Further, in the method for manufacturing an optical disc of the present invention, a first step of forming a first signal layer made of either a reflection film or a recording film on a substrate; A second step of laminating the pressure-sensitive adhesive sheet to form an adhesive sheet layer, and applying a UV curable resin to a sheet in which a fine concavo-convex pattern of a pit or group is formed in advance. A third step of applying the composition on the stamper and irradiating it with ultraviolet light to cure the composition, the ultraviolet curable resin cured on the stamper, and the adhesive sheet layer by pressure bonding. Combining, separating from the stamper and forming an ultraviolet-curable resin layer, and forming a second signal layer comprising a reflective film or a recording film on the ultraviolet-curable resin layer. The fifth step and the step of forming a cover layer on the second signal layer are used to produce an optical disc, which is useful when producing an optical disc having a multilayer structure of more than two layers. Is to repeat the above second to fifth steps twice or more.

According to the optical disc manufacturing method of the present invention, a plurality of recording layers or signal layers are stacked, and a multi-layered optical disc that performs recording or reproduction on each by changing the focal position of a laser beam. To improve the productivity of optical discs and produce high-quality optical discs o

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram schematically showing a multilayer structure of an optical disc according to the present invention.

FIG. 2 is a diagram schematically showing a method for manufacturing an optical disc of the present invention.

FIG. 3 schematically shows a specific embodiment of the optical disk of the present invention, together with FIGS. 4 to 8, and this figure has a multilayer structure having a thin cover layer and one surface of the disk. FIG. 3 is a diagram showing a structure of an optical disc adapted to perform recording and reproduction from a side of a cover layer.

FIG. 4 is a diagram showing a structure of an optical disc having a thin cover layer and a multilayer structure on both sides of the disc, and recording and reproducing data from both sides of the disc.

Fig. 5 shows a multi-layer structure of one side of the disk and a protective layer made of UV-curable resin for protecting the signal layer. FIG. 3 is a diagram showing a structure of an optical disc adapted to perform reproduction.

FIG. 6 is a diagram showing a structure of an optical disc which is a laminated type and has a multilayer structure on one side of a disc, and can perform recording and reproduction from both sides of the disc.

Fig. 7 shows a laminated type with a multilayer structure on both sides of the disk.

FIG. 2 is a diagram showing a structure of an optical disc capable of performing recording and reproduction from both sides of the disc.

FIG. 8 is a diagram showing a structure of an optical disc which is a laminated type and has a multilayer structure on both sides of a disc, and performs recording and reproduction from both sides of the disc.

FIG. 9 is a view showing a supply form of a pressure-sensitive adhesive sheet in the method for producing an optical disc of the present invention.

FIG. 10 is a view showing a step of bonding the pressure-sensitive adhesive sheet supplied by the supply mode shown in FIG. 9 to a disk substrate.

FIG. 11 is a diagram showing a step of forming a cover layer in the method of manufacturing an optical disc of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of an optical disc and a method of manufacturing the same according to the present invention will be described with reference to the accompanying drawings.

First, the basic structure of a multilayer structure of an optical disc according to the present invention will be described.

That is, as shown in FIG. 1, the optical disc 1 has a first signal layer 3 (substrate signal layer) on at least one surface of the disc substrate 2 on an uneven shape or a guide groove. And a multilayer structure 4 in which a composite layer 20 is further laminated thereon.

The structure of one layer of the multilayer structure 4 is such that a pressure-sensitive adhesive sheet layer 5 is provided on the first signal layer 3, an ultraviolet curable resin (UV resin) layer 6 is provided thereon, and a second layer is provided thereon. Of signal layers 7 Further, an optically transparent cover layer 8 is laminated on the multilayer structure 4 and on the uppermost part of the optical disc.

The irregular shape or the guide groove can be formed by applying a UV resin 6a to a stamper and curing it in advance, as shown in FIG. Then, the intermediate layer 20 is formed by bonding to the disk substrate 2 or the like.

According to this method, it is not necessary to allow the disk substrate 2 or the stamper to transmit ultraviolet light, and a multilayer optical disk having two or more layers can be easily manufactured.

Next, a method of manufacturing the optical disc 1 having the multilayer structure 4 will be described. That is, as shown in FIG. 2, a disc having a spiral or concentric concavo-convex shape or a guide groove is formed. The first signal layer 3 is formed by forming a reflective film or a reversible or irreversible recording thin film on the substrate 2 (Step A), and the pressure-sensitive adhesive sheet 5a is formed thereon. Then, the adhesive sheet layer 5 is formed (Step B).

The concavo-convex shape or the guide groove is formed by transferring this from the stamper 9 with an ultraviolet curable resin, that is, a UV resin 6a. That is, the UV resin layer 6a is applied to the stamper 9 and cured by irradiating ultraviolet rays to form the UV resin layer 6 (step C). Thereafter, the pressure-sensitive adhesive sheet 5a of the disk substrate 2 is formed. The side on which is adhered to the stamper 9 is pressed and adhered to the stamper 9 and separated, whereby the intermediate layer 10 is constituted by the adhesive sheet layer 5 and the UV resin layer 6 (step D). The second signal layer 7 is formed by further forming a reflection film or a recording film on the intermediate layer 10 (step E). In step D, the pressure-sensitive adhesive sheet 5a can be attached to the stamper 9 side. Further, when the signal layer is further laminated to produce an optical disc having three or more layers, the above-mentioned step B to step E or the above steps C to E may be performed two or more times. Repeat this number of times.

Finally, an optically transparent cover layer 8 is formed on the second signal layer 7, whereby the optical disc 1 having a multilayer structure can be manufactured (step F). The cover layer 8 has a role as a protective layer of each layer thereunder, in particular, the second signal layer 7, and a function of reducing the influence of dust and scratches during recording and reproduction.

The recording and reproduction of the optical disc 1 can be performed by irradiating a laser beam from the cover layer 8 side.

In the optical disc 1, the first signal layer 3 and the second signal layer 7 are stacked in the vertical direction (the thickness direction of the optical disc 1 or the irradiation direction of the recording / reproducing laser beam). By changing the focus position of the objective lens of the recording / reproducing device, the recording / reproducing is performed only for a specific signal layer.

Note that return light from other signal layers that are not the target of recording / reproduction is out of focus by separating each signal layer by the thickness of the intermediate layer 11, and does not return to the light receiver efficiently. The effects can be avoided.

Therefore, it is important that the thickness of the intermediate layer 10 be at least 10 times the focal depth of the objective lens of the recording / reproducing apparatus. This depth of focus is determined by the laser wavelength and the numerical aperture of the lens. For example, when the wavelength is 633 nm and the numerical aperture is 0.85, it is 2.8 μm.

The pressure-sensitive adhesive sheet layer 5 and the UV resin layer 6 constituting the intermediate layer 10 can be constituted as long as they have a film thickness of 5 m or more and 0.1 l m or more, respectively. Does not matter. However, general In general, the UV resin layer 6 has a higher hardness than the adhesive sheet layer 5 and thus tends to generate stress, so that the optical disc 1 is likely to warp. Further, since the transmittance when using a laser in the ultraviolet region to the blue region is low, it is desirable that the intermediate layer 10 be as thin as possible. According to the method of manufacturing the optical disc 1, the intermediate layer 10 between the first signal layer 3 and the second signal layer 7 is constituted by the adhesive sheet layer 5 and the ultraviolet curable resin layer 6. Therefore, it is possible to effectively prevent the disk from being warped or undulated, and to improve the quality of the optical disk. That is, the intermediate layer 10 is usually formed to have a thickness of about 25 m, but if it is formed only of an ultraviolet-curable resin, it is difficult to apply uniformly, so that the intermediate layer The thickness unevenness occurs in 10 and furthermore, the disk warps due to the influence of curing shrinkage and the like, and it is difficult to make uniform contact between the stamper 9 and the disk. According to the present invention, the unevenness of the film thickness of the adhesive sheet layer 5 is approximately plus or minus 5%, and the film thickness is pressure-bonded onto the disc substrate to make the intermediate layer 10 uniform. Therefore, the quality of the optical disc can be improved.

The reflectance of the first signal layer 3 and the second signal layer 7 and the like is adjusted according to the number of layers of the multilayer structure 4 and the reflectance, transmittance, absorptance, and the like of each layer. When it is desired to make the intensity of the return light from each signal layer uniform, it is possible to increase the reflectance of each signal layer in order from the laser beam incident side. For this reason, the direction in which recording and reproduction are performed (the direction in which a laser beam is irradiated) is limited.

The first signal layer 3 and the second signal layer 7 do not need to be made of the same material film, and can be read by combining with a reflective film made of pits or the like or a reversible or irreversible recording film. Dedicated (read only), rewritable (rewritable), appendable (write It is also possible to manufacture an optical disc in which various signal layers (such as attance) are mixed.

Further, a film having wavelength selectivity may be combined with the first signal layer 3, the second signal layer 7, and the like. For example, if a red laser light transmitting and blue laser light reflecting film is used for the second signal layer 7, the first signal layer 3 can record and reproduce with a red laser, and the second signal layer 7 This makes it possible to manufacture discs with a structure that allows recording and reproduction with a laser. The specific structures of various optical discs taking into account the multilayer structure by the above manufacturing method are shown below.

That is, as shown in FIG. 3, in the optical disk 1A having a thin cover layer 8, a multilayer structure 4 is provided on the disk substrate 2, and finally, a cover layer 8 for protecting the multilayer structure 4 is provided. Is provided. Therefore, recording and reproduction are performed from the side of the cover layer 8 as indicated by arrows in the irradiation direction of the laser beam.

As shown in FIG. 4, if multi-layer structures 4 and 4 are provided on both sides of the disc substrate 2, the laser beam irradiation direction is indicated by the arrow, and the optical disc of the double-sided recording / reproduction evening is indicated. 1 B.

In addition, as shown in FIG. 5, in an existing single-plate optical disc (for example, a CD (Compact Disc)) 1 C, the direction of laser beam irradiation is indicated by an arrow on the disc substrate 2. In order to perform recording and reproduction from the side, instead of the cover layer, a layer for protecting the signal layer having a multilayer structure, for example, an ultraviolet curable resin or the like is applied to form the protective layer 11, so that the double-sided configuration is Can not.

Furthermore, in the case of a bonded type such as a so-called DVD, there are two types of structures for an optical disc that performs recording and reproduction from one side.

That is, one of the optical discs for recording / reproducing from one side of the above-mentioned laminated type has a multilayer structure 4 as shown in FIG. The optical disc 1D has a structure in which the disc substrate 2 and the disc substrate 12 on which no signal layer is formed are bonded. In the optical disc 1D, when recording / reproducing by irradiating a laser beam from the side of the disc substrate 2 having the multilayer structure 4, the material and thickness of the disc substrate 12 having no signal layer are required. Is a disk substrate with multilayer structure 4

There is no need to be the same as 2 and it is not necessary to be optically transparent (transmit the laser beam).

Recording and reproduction from the disk substrate 12 side are also possible. In this case, for example, a multilayer structure 4 may be formed on a polycarbonate disk substrate 2 and a glass disk substrate 12 may be bonded thereto.

As shown in FIG. 7, the other of the above-mentioned bonded type optical discs for recording and reproducing from one side is composed of two disk substrates 2 each having a multilayer structure 4 and a multilayer structure 4. By laminating on the formed side and using the lamination layer 13 as an optical intermediate layer, recording and reproduction can be performed on all signal layers by irradiating a laser beam from one side. This is the optical disk 1E.

Furthermore, as shown in FIG. 8, in a bonded optical disk 1F for recording and reproducing from both sides of the disk, a multilayer structure 4 is formed in the same manner as the optical disk 1E. It has a structure in which two disk substrates 2 are bonded together on the surface on the side where the multilayer structure 4 is formed, and the bonding layer 13 is used as an intermediate layer. A laser beam is irradiated from both sides of F, and recording / reproducing is performed from each disk substrate 2 side.

Lastly, a process for producing an optical disc having a thin cover layer 8, for example, the above-described optical disc 1A will be described more specifically. In other words, as shown in FIG. 2, the disk substrate 2 had a diameter of 120 mm in which a pit shape was previously transferred by injection molding. It is made of polycarbonate with a thickness of 1.2 mm. Then, as a first signal layer 3, an aluminum reflection film is formed to a thickness of 6 O nm by sputtering (step A).

In addition, as a material of the disc substrate 2, a thermoplastic resin, a thermosetting resin, a glass substrate, or the like can be considered. Further, when recording / reproducing is not performed from the disk substrate 2 side, the disk substrate 2 does not need to be optically transparent, and may have uneven refractive index or birefringence.

Next, a urethane-acrylic UV resin 6a is dropped on the stano at 99, and the thickness is made uniform by spin coating (30 000 rpm for 30 seconds). At this time, the thickness of the UV resin 6a is, for example, 2 m. Thereafter, ultraviolet rays are irradiated for 5 seconds with a mercury lamp or a halogen lamp to cure the UV resin 6a (step C). A pressure-sensitive adhesive sheet 5a having a thickness of 25 m is attached to the disk substrate 2 (step B). As shown in FIG. 9, this pressure-sensitive adhesive sheet 5a is obtained by attaching a protective cover 14 to a sheet of the pressure-sensitive adhesive sheet 5a previously punched into a predetermined disc shape. A large number of polyethylene sheet mounts (transportation sheets) are arranged on the sheet 15 and are bonded to the disk substrate 2 by pressure bonding with a silicon rubber pad described later ( Process B

) o

As shown in Fig. 10, the pressure-sensitive adhesive sheet 5a is pressed and adhered to the disk substrate 2 by a silicone pad 16, and then the transfer sheet 15 isされる Released (Step D). If there are bubbles in the pressure-sensitive adhesive sheet 5a, pressurized defoaming treatment (for example,

(Leave it in compressed air at 10 atm for several minutes).

Then, as the second signal layer 7, an aluminum film is formed by sputtering while adjusting the transmittance with a film thickness of 20 to 40 nm. (Step E).

At this time, the thickness of the intermediate layer 10 composed of the adhesive sheet layer 5 and the UV resin layer 6 was 27 // m, and the thickness unevenness was not more than + Z minus 2 / z m.

Then, the above steps B to E are repeated again to form the intermediate layer 10 and the new signal layer 17 on the second signal layer 7, thereby obtaining a three-layer structure.

Finally, a polycarbonate plate 18 having a thickness of 70 m is laminated as a cover layer 8 (process F). That is, as shown in FIG. 11 in order, a UV resin 6a is applied on the signal layer 17 in a circular pattern, and then a polycarbonate plate 18 is installed. By rotating the resin at 00 rpm for 30 seconds, the UV resin 6a between the signal layer 17 and the polycarbonate plate 18 is thinly and evenly spread, and then irradiated with ultraviolet light to emit UV resin. When 6a is hardened, an optical disk 1A is formed.

As described above, the optical disc and the method of manufacturing the same according to the present invention aim to obtain an optical disc having a multilayer structure in which two or more signal layers are formed. Intermediate layer between signal layers Force By using an adhesive sheet and UV curable resin, it is possible to effectively prevent the warpage and distortion of the disc, and to improve the productivity of large-capacity optical discs. Therefore, it can be easily provided.

Further, since the thickness unevenness of the intermediate layer 10 is uniform, it is also possible to form an optical disc having a multilayer structure corresponding to high NA, high speed recording and Z reproduction.

Also, by changing each of the stacked signal layers to various types, it becomes possible to provide an optical disk in which read-only, light-at-a-time, and rewritable are mixed. Further, by changing the wavelength of the laser beam, it is possible to give selectivity to an arbitrary signal layer to be recorded / reproduced.

It should be noted that the specific shapes and structures of the respective parts shown in the above-described embodiment are merely specific examples for embodying the present invention, and the technical The scope should not be construed as limiting.

As described above, in the optical disc of the present invention, a signal layer is formed on at least one surface of the disc substrate, and at least one new signal layer is formed on the signal layer via the intermediate layer. In an optical disc in which a multilayer structure is formed by laminating, and data is recorded or reproduced on two or more signal layers, an intermediate layer is formed by an ultraviolet curable resin layer and an adhesive sheet layer. However, the UV curable resin layer is formed with a concave / convex shape or a guide groove that constitutes a data recording signal, so that it is possible to easily form a multilayer of two or more layers, and to use a large-capacity optical disk. It can be easily provided with good productivity.

Further, in the optical disc manufacturing method of the present invention, a signal layer is formed on at least one surface of the disc substrate, and at least one new signal layer is laminated on the signal layer via an intermediate layer. In a method for manufacturing an optical disc in which a multi-layer structure is formed by which data is recorded or reproduced on two or more signal layers, the intermediate layer is formed in advance with the uneven shape of the stamper or guide. Since the UV-cured resin layer with the transferred grooves is bonded to the disk substrate with a pressure-sensitive adhesive sheet, it can be easily formed into two or more layers. Large-capacity optical discs can be easily provided with good productivity.

According to the invention described in claims 3 and 5, a cover layer is formed on a multilayer structure, and a signal layer is recorded by using one cover layer as a light transmitting layer. Since reproduction is performed, large-capacity optical discs can be easily provided with good productivity.

In the invention described in claim 4, since the multilayer structure is formed on both sides of the disc substrate, a larger capacity can be achieved as compared with the case of one side.

In the invention described in claims 5 to 8, one of the disks is formed by bonding disk substrates provided with a multilayer structure to each other and using a layer formed by bonding as an intermediate layer. Since recording and reproduction to all signal layers are performed from the side of, the capacity can be increased as compared with the case where the multilayer structure is single-sided.

Claims

The scope of the claims

1. A substrate signal layer is formed on the substrate,

In an optical disc having a multilayer structure in which a composite layer composed of an intermediate layer and a signal layer is further formed on the substrate signal layer,

An optical disc characterized in that the intermediate layer comprises an ultraviolet curable resin layer and an adhesive sheet layer.

2. The optical disc according to claim 1, wherein the ultraviolet curable resin layer is formed by transfer of a stamper.

3. A cover layer is formed on the multilayer structure, and the signal layer is recorded / reproduced by irradiating a laser beam from the cover layer forming surface side. An optical disc according to item 1.

4. The optical disc according to claim 1, wherein the multilayer structure is formed on both sides of the substrate.

5. The optical disc according to claim 3, wherein the multilayer structure is formed on both sides of the substrate.

6. The substrate on which the multilayer structure is formed is attached to each other, and recording and reproduction of the signal layer is performed by irradiating a laser beam from one side of the substrate. Term

Optical disc according to 1.

7. The substrate on which the multilayer structure is formed is bonded to each other, and a laser beam is irradiated from one side of the substrate to perform recording / reproduction of the signal layer. An optical disc according to item 3.

8. The substrate on which the multilayer structure is formed is stuck together, and a laser beam is irradiated from one side of the substrate to perform recording / reproduction of the signal layer. Term Optical disc according to 4.

9. A first step of forming a first signal layer made of either a reflective film or a recording film on a substrate;

A second step of laminating a pressure-sensitive adhesive sheet on the first signal layer to form an adhesive sheet layer;

A third step of applying a UV-curable resin on the stamper and irradiating with UV light to cure the resin;

A fourth step of pressing and bonding the ultraviolet-curable resin cured on the stamper and the adhesive sheet layer, separating from the stamper, and forming an ultraviolet-curable resin layer;

A fifth step of forming a second signal layer made of either a reflective film or a recording film on the ultraviolet curable resin layer;

Forming a cover layer on the second signal layer. A method for manufacturing an optical disc, comprising:

10. The method of manufacturing an optical disc according to claim 9, wherein the steps from the second step to the fifth step are repeated at least twice.