JP3338660B2 - optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk having a light transmitting layer provided on a substrate and recording and reproducing information by irradiating a laser beam from the light transmitting layer side.

[0002]

2. Description of the Related Art Conventionally, as an optical disk, a replica substrate made of a light-transmitting plastic having irregularities formed on one surface is manufactured, and a reflection film or a recording film is provided on the irregularities formed surface to form a signal recording surface. It is widely known that a protective film is formed on a signal recording surface, and recording and reproduction are performed by irradiating a laser beam from a substrate surface side (a surface opposite to the signal recording surface).

In such an optical disk, since the substrate plays a role of a light transmitting layer, it is required to reduce the thickness of the substrate in order to increase the capacity, for example, to 8 GB or more.

In the above-mentioned optical disk, the substrate is usually formed by injection molding, and there is a limit to the reduction in thickness.

[0005] For example, when a substrate having a diameter of 120 mm is manufactured, when it is intended to ensure the transferability of irregularities at a normal level (the level of a conventional optical disk), a thickness of 3 mm is required.
The limit is about 00 μm. In order to accurately transfer irregularities in response to an increase in capacity, a thickness of about 500 μm is the limit.

For this reason, it is very difficult to produce an optical disk substrate having a thickness of about 100 μm and fine irregularities accurately transferred thereon by injection molding.

This is due to a problem inherent in injection molding. For example, unevenness in the flow state of the injection material in the mold, ie, the molten resin, unevenness in the cooling rate of the mold (uneven temperature and viscosity of the molten resin). ) Etc.

[0008]

In such a situation,
The present applicant has proposed an optical disc in which a light transmitting layer of 177 μm or less is formed on a signal recording surface of a substrate, and recording and reproduction are performed by irradiating a laser beam from the light transmitting layer side.

In this optical disk, since the substrate can have a normal thickness (for example, 1.2 mm or 0.6 mm), it is possible to transfer irregularities with high precision by injection molding. On the other hand, laser light for recording and reproduction is applied from the light transmitting layer side having a small thickness, so that it is possible to cope with an increase in capacity.

When recording and reproduction are performed by irradiating laser light from the light transmitting layer side, how to form the light transmitting layer is a major problem. This is because a change in the thickness of the light transmitting layer or the like greatly affects the characteristics.

As a method of forming the light transmitting layer, for example, a method of applying an ultraviolet curable resin by a spin coating method or the like can be considered, but in this case, it is difficult to form a film having a uniform thickness.

Accordingly, an object of the present invention is to provide an optical disc having a light transmitting layer having a small thickness and a uniform thickness.

[0013]

In order to achieve the above object, an optical disk according to the present invention has a substrate, and a transparent film bonded to one surface of the substrate by a pressure-sensitive adhesive sheet. And / or a signal recording surface is formed on a bonding surface of the transparent film, the transparent film is a polycarbonate film, the polycarbonate film is bonded via the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive sheet is , At least 3
The transparent film has a light transmittance of 90% or more in a wavelength region of 00 nm or more, and the transparent film has at least 30%.
The light-transmitting layer has a light transmittance of 80% or more in a wavelength region of 0 nm or more, and has a thickness of 3 μm to 177 μm formed by the pressure-sensitive adhesive sheet and the transparent film. 300 nm to 800 nm
The light transmission layer has a light transmittance of 70% or more in the region, and recording and / or reproduction is performed on the signal recording surface from the light transmission layer side.

The optical disk according to the present invention comprises a substrate having a signal recording surface formed on one surface thereof, and a pressure-sensitive adhesive sheet as a light transmitting layer laminated on the signal recording surface. The pressure-sensitive adhesive sheet has at least 300
It has a light transmittance of 90% or more in a wavelength region of nm or more, and is configured to perform recording and / or reproduction on the signal recording surface from the light transmission layer side.

The pressure-sensitive adhesive sheet used in the present invention is in the form of a sheet itself, and is different from the case where an ultraviolet curable resin is applied, and is previously formed as a layer (sheet) having a constant thickness. If used for the adhesive layer or the light transmitting layer itself, a light transmitting layer having a very small thickness and no thickness unevenness can be easily formed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical disc according to the present invention will be described with reference to the drawings.

First, as shown in FIG. 1, the basic structure of the optical disk of the present invention is as follows.
A substrate in which a transparent film 2 is adhered to one surface of a substrate 1 having a thickness of about 6 mm via an adhesive layer 3 may be used.

Here, on one or both of the substrate 1 and the transparent film 2, a concavo-convex pattern such as a pit or a groove is formed, and is used as a signal recording surface.

For example, FIG. 2 shows that a concavo-convex pattern is formed on the surface of the substrate 1 on the side to be bonded to the transparent film 2,
This shows an example in which the signal recording surface 1a is used.

FIG. 3 shows an example in which a signal recording surface 2a is formed by forming a concavo-convex pattern on the surface of the transparent film 2 on the side to be bonded to the substrate 1, on the contrary.

FIG. 4 shows a substrate 1 and a transparent film 2.
1 shows an example in which signal recording surfaces 1a and 2a are formed on both of them, and the signal recording surface has a two-layer structure.

In any of the examples, the substrate 1 is made by, for example, injection molding a plastic material, but the plastic material used does not necessarily have to be optically transparent. Further, it may be formed of a material other than the plastic material, for example, glass, ceramics, metal and the like.

When the substrate 1 is injection-molded, the substrate 1
If the thickness of the layer is too thin, it is difficult to transfer the unevenness precisely. Therefore, when a signal recording surface is formed on the substrate 1, the thickness of the substrate 1 is preferably 0.3 mm or more. Thereby, a highly accurate signal recording surface can be formed.

The signal recording surface 1a provided on the substrate 1
For example, a metal reflective film, a translucent signal layer, a signal recording layer, or various recording layers are formed on a signal recording surface 2a provided on the transparent film 2 and an information signal is read by reading reflected light from these layers. Is played. At this time,
In particular, when a signal recording surface is formed on both the substrate 1 and the transparent film 2 as in the example shown in FIG. 4, a translucent signal layer and a signal recording layer should be formed on the signal recording surface 2a on the transparent film 2 side. Is preferred.

The recording layer includes a magneto-optical recording layer, a phase change recording layer,
Organic dye layer or the like, or a combination thereof,
It may be laminated with a dielectric film or the like for enhancement.

On the other hand, the material of the transparent film 2 to be bonded to the substrate 1 needs to be optically transparent and preferably has a small birefringence. From such a viewpoint, for example, polycarbonate, polyester, amorphous polyolefin and the like are suitable.

On the surface of the transparent film 2, a protective layer made of an inorganic substance or an organic resin may be formed. Examples of the inorganic substance include SiN, SiO ₂ , and SiC, and these may be formed into a film having a thickness of about 10 to 2000 ° to form a protective layer.

A feature of the present invention is that a pressure-sensitive adhesive sheet is used as the adhesive layer 3. The pressure-sensitive adhesive sheet is made of, for example, an acrylic adhesive,
This is a double-sided PSA sheet with excellent transparency and uniformity of thickness.
Brand names DA-8320, DA-8310 manufactured by Nitto Denko Corporation
Etc. are preferred. The pressure-sensitive adhesive sheet is a sheet having a uniform thickness. Unlike the case where the adhesive layer is formed by coating, the adhesive layer 3 having a uniform thickness can be easily formed. The bonding step 2 can be greatly simplified.

The adhesive layer 3 composed of the transparent film 2 and the pressure-sensitive adhesive sheet serves as a light transmitting layer.
At the time of recording or reproduction, a laser beam is applied to the signal recording surface formed on the substrate 1 or the transparent film 2 from the transparent film 2 and the adhesive layer 3 side. Therefore,
It is important to make the thicknesses of the transparent film 2 and the adhesive layer 3 appropriate.

Specifically, when the signal recording surface of the substrate 1 is considered, the total thickness of the transparent film 2 and the adhesive layer 3 is:
It is preferable to be within the range of 3 μm to 177 μm. When the signal recording surface of the transparent film 2 is taken into consideration, it is preferable that the thickness of the transparent film 2 is in the range of μm3 to 177 μm.

In consideration of the function of the light transmitting layer, the thinner the thickness, the more it is possible to cope with a higher NA for higher density recording, which is advantageous. Since this light transmitting layer also serves as a protective layer, if it is too thin, the protective function cannot be secured. Considering the reliability of the optical disc and the impact of the objective lens on the light transmitting layer surface, etc., 3 μm
Is the lower limit. On the other hand, as the wavelength of laser light or the like is becoming shorter, the upper limit is 177 μm in order to support not only red lasers but also blue lasers.

In this total thickness, the transparent film 2
And the thickness occupied by the adhesive layer 3 are arbitrary. For example, the thickness of the adhesive layer 3 may be any thickness as long as the adhesive strength can be sufficiently secured.

On the contrary, the thickness of the adhesive layer 3 may be arbitrarily large as long as the total thickness is within the above range. In an extreme case, the light transmitting layer may be formed only of the adhesive layer 3.

FIG. 5 shows an example of an optical disk in which the light transmitting layer comprises only the adhesive layer 3 made of a pressure-sensitive adhesive sheet. This is another example of the optical disk of the present invention. This optical disk has a very simple structure in which an adhesive layer 3 is simply attached on a signal recording surface (recording layer 4) formed on a substrate 1.

All of the above-mentioned optical disks aim at higher density recording than ever, and therefore, it is desired that the light transmitting layer has a high light transmittance in a laser wavelength range used for recording and reproduction. .

From such a viewpoint, in the optical disk having the structure shown in FIGS. 1 to 4, it is preferable to use a polycarbonate film for the transparent film 2 and a pressure-sensitive adhesive sheet for the adhesive layer 3. Polycarbonate film is
By increasing the purity by devising the manufacturing method, etc., good light transmittance is shown in a wide wavelength range. FIG. 6 shows a thickness of 100 μm.
It shows the wavelength dependence of the transmittance of the polycarbonate film of the m.
% Or more.

Similarly, the pressure-sensitive adhesive sheet also shows good optical properties. For example, DA-831 (trade name, manufactured by Nitto Denko Corporation)
For a light transmittance of 0, a spectrophotometer (Jasco V750)
FIG. 7 shows the results of the measurement using. As a result of the measurement, 30
It shows a light transmittance of 90% or more in a wavelength range of up to 0 nm, and it can be seen that it has good transparency comparable to a glass plate.

In reading information, it is preferable that the birefringence of the adhesive layer 3 as the intermediate layer is as small as possible. When the birefringence is large, astigmatism increases even if an attempt is made to focus the reading laser beam, and the laser beam cannot be completely stopped. As a result of measuring the birefringence of the pressure-sensitive adhesive sheet, it was within the measurement error range (almost zero).

Therefore, it can be said that the pressure-sensitive adhesive sheet has no problem as the adhesive layer 3 in terms of optical characteristics.

If a polycarbonate film is used as the transparent film 2 and a pressure-sensitive adhesive sheet is used as the adhesive layer 3, the light transmittance of the light transmitting layer can be increased to 70% or more at a wavelength of 300 nm to 800 nm, and a wide wavelength range can be obtained. As a result, it is possible to realize recording and reproduction as good as a compact disc. This is very advantageous in realizing a high-density recording optical disk.

On the other hand, when the light transmitting layer is formed using an ultraviolet curable resin, as shown in FIG. 8, the light transmittance sharply decreases in a short wavelength region. It drops to 50% or less. Therefore, it is not possible to sufficiently cope with short-wavelength recording.

As a method of manufacturing the above-mentioned optical disk, various manufacturing methods can be mentioned.

For example, in order to manufacture an optical disk having the signal recording surface 1a formed on the substrate 1 side as shown in FIG. 2, a raw roll of the film 112 on which the adhesive layer 201 made of a pressure-sensitive adhesive sheet is formed is used. As shown in FIG. 9, the signal recording unit 103 of the substrate 101 (this signal recording unit 1
A recording film or a reflective film 103a is formed on the substrate 03. ) The film 112 is overlaid with the adhesive layer 201 interposed therebetween.

In this state, the film 112 is pressure-bonded to the substrate 101 by the pressure roller 202, and the film 112 is brought into close contact with the information recording portion 103 so that the adhesive layer 201 enters.

After the adhesive layer 201 is pressed against the information recording section 103, air (bubbles) in the film / adhesive layer or in the adhesive layer is removed by performing an autoclave treatment using a pressure cooker or a defoaming treatment under reduced pressure. It may be excluded.

Finally, the film 112 and the adhesive layer 2
01 is punched into the shape of the substrate 101 to complete the optical disk.

Specifically, a polycarbonate film (thickness: 50 μm) on which a pressure-sensitive adhesive sheet (thickness: DA-8310, manufactured by Nitto Denko Corporation) having a thickness of 50 μm is stuck to the substrate 101, pressed, and then punched out By performing trimming in the process, an optical disc having a light transmitting layer having a thickness of 100 μm was completed. After that, foaming was significantly reduced by performing an autoclave treatment.

In the above manufacturing apparatus and manufacturing method, both the polycarbonate film 112 and the adhesive layer 201 are used as the light transmitting layer. However, when the pressure-sensitive adhesive sheet is used, only the adhesive layer 201 is used as the light transmitting layer. You can also.

FIG. 10 shows this step. The process shown in FIG. 10 is basically the same as the process shown in FIG. 9, but the process shown in FIG. 9 is greatly different from the process shown in FIG. 9 in that the support 205 of the adhesive layer 201 is peeled off after pressure bonding.

As a result, only the adhesive layer 201
It remains on top and functions as a light transmitting layer. Therefore, it is not necessary to use a film having excellent light transmittance such as a polycarbonate film for the support 205,
Any material, such as release paper, can be used.

For example, the thickness of the adhesive layer 201 is 50 μm.
Pressure-sensitive adhesive sheet (trade name: DA-83, manufactured by Nitto Denko Corporation)
The optical disk having a light transmitting layer having a thickness of 50 μm can be obtained by removing the support 205 after attaching the substrate to the substrate 101 by using the method 10).

By repeating these processes,
A light transmitting layer having a thickness that is a multiple of the thickness of the adhesive layer 201 is obtained.

When producing an optical disk having the signal recording surface 2a formed on the transparent film 2 side as shown in FIG. 3, the signal recording surface 2a is formed on the transparent film 2 by 2P (Photo Polymerization). Or a direct embossing method.

FIG. 11 shows an example of a process for forming a signal recording surface on a transparent film by the 2P method. In this example, a signal recording surface is continuously formed on the transparent film 302 fed from the roll 301. In this method, first, as shown in step A, a stamper 303 having an inverted concavo-convex pattern on the signal recording surface is prepared, and in step B, an ultraviolet curable resin 304 is applied thereon.

Next, in step C, the transparent film 302 is pressed against the stamper 303 to which the ultraviolet curable resin 304 has been applied. This crimping is performed by stamper 3
03 is transferred, and here, roller pressing is performed using a roller 305. In this state, ultraviolet rays are irradiated from the transparent film 302 side (Step D), and after the ultraviolet curable resin 304 is cured, the stamper 303 is peeled off from the ultraviolet curable resin 304 (Step E).

Finally, a semi-transparent signal layer or signal recording layer made of SiN or the like is formed by a method such as sputtering (Step F), and is punched out in a disk shape (Step G) to obtain an ultraviolet curable resin. Signal recording surface 304 on the surface of 304
A transparent film 302 on which a is formed is obtained.

FIG. 12 shows an example of a process for forming a signal recording surface on a transparent film by an embossing method. In the case of the embossing method, a concavo-convex pattern is directly transferred to a transparent film by a stamper.

First, the point that a signal recording surface is continuously formed on the transparent film 402 fed from the roll 401 is the same as in the case of the 2P method. Next, as shown in Step A, a stamper 403 on which an inverted concavo-convex pattern of the signal recording surface is formed is prepared.
To the transparent film 402 (step B).
At this time, the transparent film 402 is
It is preferable to heat to an appropriate temperature so that the concave / convex pattern is transferred.

After cooling (Step C), the stamper 403 is peeled from the transparent film 402 (Step D), and the
A semi-transparent signal layer, a signal recording layer, and the like are formed by a technique such as sputtering (step E). This is punched out in a disk shape (step F) to obtain a transparent film 402 on which a signal recording surface 402a is formed.

Next, a method for continuously forming an optical disk having two signal recording surfaces as shown in FIG. 4 by applying the embossing method will be described.

FIG. 13 shows an example of a continuous forming step, in which a transparent film 402 unwound from a roll 401 is shown.
On the other hand, the point that the signal recording surface 402a is continuously formed by transferring and forming a concavo-convex pattern by the stamper 403 conforms to the embossing method described above.

Next, an adhesive film 406 made of a pressure-sensitive adhesive sheet formed on release paper 405 is
7 and bonded on the signal recording surface 402a of the transparent film 402. The release paper 405 is peeled off from the adhesive film 406 while being taken up by the take-up roll 408, and the signal recording surface 40 is placed on the exposed adhesive film 406.
The substrate 409 on which 9a is formed is bonded using a roller 410. By punching this into a disk, an optical disk having two layers of signal recording surfaces can be obtained.

As a modified example, as shown in FIG. 14, for example, an adhesive film 406 was pasted on a signal recording surface 409a of a substrate 409 by a pressure roll 411, and this was formed on the transparent film 402. You may make it join on the signal recording surface 402a.

Although the method for forming the light transmitting layer and the method for forming the optical disk using the pressure-sensitive adhesive sheet have been described above, it goes without saying that various changes can be made in the process.

[0065]

As is clear from the above description, according to the present invention, it is possible to provide an optical disc having a light transmitting layer with a small thickness and a uniform thickness. It is possible to provide an optical disk capable of recording at a much higher density.

Also, by using a pressure-sensitive adhesive sheet for the adhesive layer, an optical disc having high light transmittance in a wide wavelength range can be obtained. Particularly, when considering high-density recording by short-wavelength recording, Very advantageous.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part showing a basic configuration of an optical disc to which the present invention is applied.

FIG. 2 is a schematic cross-sectional view of a main part showing an example of an optical disk having a signal recording surface formed on a substrate.

FIG. 3 is a schematic cross-sectional view of a main part showing an example of an optical disk having a signal recording surface formed on a transparent film.

FIG. 4 is a schematic cross-sectional view of a main part showing an example of an optical disc having a signal recording surface formed on both a substrate and a transparent film.

FIG. 5 is a schematic sectional view of a main part showing another configuration example of an optical disc to which the present invention is applied.

FIG. 6 is a characteristic diagram showing spectral optical characteristics of a polycarbonate film.

FIG. 7 is a characteristic diagram showing spectral optical characteristics of the pressure-sensitive adhesive sheet.

FIG. 8 is a characteristic diagram showing spectral optical characteristics of an ultraviolet curable resin.

FIG. 9 is a schematic view illustrating an example of a manufacturing process of an optical disc having a signal recording surface formed on a substrate.

FIG. 10 is a schematic view showing another example of a manufacturing process of an optical disc having a signal recording surface formed on a substrate.

FIG. 11 is a schematic view showing an example of a step of forming a signal recording surface on a transparent film by a 2P method.

FIG. 12 is a schematic view showing an example of a process for forming a signal recording surface on a transparent film by an embossing method.

FIG. 13 is a schematic view illustrating an example of a manufacturing process of an optical disc having two signal recording surfaces.

FIG. 14 is a schematic view illustrating another example of a manufacturing process of an optical disc having two layers of signal recording surfaces.

[Explanation of symbols]

1 substrate, 1a signal recording surface, 2 transparent film,
2a Signal recording surface, 3 adhesive layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Motohiro Furuki 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Toshiyuki Kashiwagi 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo (56) References JP-A-9-147417 (JP, A) JP-A-8-203126 (JP, A) JP-A-60-125945 (JP, A) JP-A-7-334866 ( JP, A)

Claims (10)

(57) [Claims] 1. A substrate comprising: a substrate; and a transparent film bonded to one surface of the substrate with a pressure-sensitive adhesive sheet;
A signal recording surface is formed on a bonding surface of the substrate and / or the transparent film, and the transparent film is a polycarbonate film,
The polycarbonate foil is applied via the pressure-sensitive adhesive sheet.
The pressure-sensitive adhesive sheet has a light transmittance of 90% or more in a wavelength region of at least 300 nm, and the transparent film has a light transmittance of 80% or more in a wavelength region of at least 300 nm. Having a thickness of 3 by the pressure-sensitive adhesive sheet and the transparent film.
A light transmission layer of μm to 177 μm is formed.
Light transmission layer is in the wavelength range of 300 nm to 800 nm.
An optical disc having a light transmittance of 70% or more, and recording and / or reproduction from / to the signal recording surface from the light transmitting layer side. 2. The optical disk according to claim 1, wherein said substrate is an injection molded substrate. 3. The optical disk according to claim 1, wherein said substrate has a thickness of 0.3 mm or more. 4. The optical disk according to claim 1, wherein a protective layer is formed on a surface of said transparent film. 5. The optical disk according to claim 1, wherein the signal recording surface is formed on a bonding surface of the substrate. 6. The optical disk according to claim 1, wherein the signal recording surface is formed on a surface to which the transparent film is bonded. 7. A substrate having a signal recording surface formed on one surface thereof,
A pressure-sensitive adhesive sheet as a light-transmitting layer bonded to the signal recording surface, wherein the pressure-sensitive adhesive sheet has a 90%
An optical disc having the above light transmittance, wherein recording and / or reproduction is performed on the signal recording surface from the light transmission layer side. 8. The light transmitting layer has a thickness of 3 μm to 177 μm.
The optical disk according to claim 7, wherein m is m. 9. The optical disk according to claim 7, wherein said substrate is an injection molded substrate. 10. The optical disk according to claim 7, wherein said substrate has a thickness of 0.3 mm or more.