JPH08306077A - Optical recording medium having multilayered structure and its production - Google Patents

Abstract

PURPOSE: To simplify processes by sticking a transparent resin layer to a 1st information recording layer and interposing a transparent middle layer between the transparent resin layer and a 2nd informal recording layer. CONSTITUTION: A transparent resin layer 32 is stuck to a 1st information recording layer 1, a transparent middle layer with an adhered transparent sheet spacer 31 is disposed on the resin layer 32 and a 2nd information recording layer 2 is formed on the sheet spacer. An optical disk part 11 with the formed 1st information recording layer 1 is produced by injection-molding a resin having light transmittance, e.g. a transparent resin such as polycarbonate. Since the transparent sheet spacer is interposed between the 1st and 2nd information recording layers, the middle layer can be made sufficiently thick and entirely uniform in thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer optical recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art As an optical recording medium for recording various information such as audio, video, etc., the amount of information that can be recorded on an optical recording medium such as an optical disk or a card for recording or / and reproducing the light In order to increase the size, it is desired that the information recording layer has a multilayer structure.

[0003]

As a multilayer structure optical recording medium, as shown in a schematic sectional view of FIG. 5, at least a first information recording layer 1 and a second information recording layer 2 are an intermediate layer 3. Are stacked through. In this case, it is possible to simplify the drive device so that the optical recording or / and reproduction of the information can be performed by irradiation from the same side of the recording medium by, for example, one set of optical heads.
And it is desirable for increasing the access speed in continuous recording or / and reproducing of both information recording layers 1 and 2.

In this case, optical recording or / and
For example, the first information recording layer 1 located on the side where the reproduction light is irradiated has a structure having a required reflectance and a required transmittance, and the second information recording layer 2 has a high reflectance information recording. In the optical recording or / and reproducing on the first information recording layer 1, the irradiation light 21L from the optical head is focused to record or / and reproduce the second information recording. In the optical recording and / or reproducing on the layer 2, the recording light and / or reproducing is performed by focusing the irradiation light 22L on the second information recording layer.

However, in this case, when the distance between the first information recording layer 1 and the second information recording layer 2 is small, there arises a problem of interference of irradiation light. Therefore, it is desired that the distance between the first information recording layer 1 and the second information recording layer 2 be made somewhat larger than the wavelength of the irradiation light. For example, when the wavelength of the irradiation light is 630 nm, It is desired that the thickness of the intermediate layer 3 be as thick as about 40 μm.

For example, the recorded information is recorded as concave and convex pits, and the recorded information is read out by light irradiation in a ROM (Re
When constructing an ad-only memory type multi-layered optical disc, the first information recording layer 1 is constituted by, for example, an injection-molded optical disc section 11, and a transparent intermediate layer is formed on the first recorded information section 1 of the optical disc section 11. It is conceivable to form the information recording layer 2 of the second recording via the layer 3 by, for example, a photopolymerization method. In this case, the intermediate layer 3 may be formed by, for example, applying an ultraviolet curable resin by a spin coating method. In the case of such a spin coating method, the entire surface of the disk is covered with the central portion and the outer peripheral portion. In particular, it is difficult to apply it uniformly and uniformly and with a sufficient thickness, which causes problems such as deterioration of optical characteristics of the finally manufactured recording medium and decrease of yield.

In order to form a thick intermediate layer, it is conceivable to repeatedly apply, for example, an ultraviolet curable resin, but in this case, the number of coating steps becomes large, which hinders mass productivity.

It is also conceivable to interpose only a transparent sheet spacer as an intermediate layer, but in this case, there is a problem in selecting a material for the sheet spacer that is well adhered to both the first and second information recording layers. Yes, and both the first and second information recording layers are ROM (Read O
nly Memory) type configuration, for example, the first
It is more effective to fill the uneven pits of the information recording layer of No. 2 with a sheet spacer without leaving a void and to uniformly maintain a required thickness, and further to form the other second information recording layer on this sheet spacer. It is difficult to select the material, and therefore sufficient reliability may not be obtained.

In the present invention, in the above-mentioned multilayer structure optical recording medium having at least the first and second information recording layers, the intermediate layer between the respective information recording layers is sufficiently thick,
Moreover, it has a structure that can be formed uniformly and uniformly in a simple process, and has excellent optical characteristics, and thus excellent S / N and C / N characteristics, and / or recording and / or reproducing characteristics. An optical recording medium having a good multi-layer structure is provided.

[0010]

A multi-layered optical recording medium according to the present invention comprises at least a first information recording layer and a second information recording layer, which are laminated between the first and second information recording layers. , A transparent resin layer is deposited on the first information recording layer side, and a transparent intermediate layer in which a transparent sheet spacer is adhered is interposed on the transparent resin layer, and the second information recording layer is formed on the transparent sheet spacer. The configuration is

Further, in the method for manufacturing a multi-layered optical recording medium according to the present invention, a step of producing by injection molding an optical disk portion on which the first information recording layer is formed by concave and convex pits, and the first optical disk portion is formed on the optical disk portion. The step of forming a transparent resin layer whose surface is flattened by a photopolymerization method using a flat stamper having a flat surface by filling the uneven pits of the information recording layer with a transparent sheet spacer on the transparent resin layer. The second information recording layer is formed on the transparent sheet spacer by the photopolymerization method by the concavo-convex pits on the transparent sheet spacer, or the second information recording layer is formed on the surface of the transparent sheet spacer by the pressing process by the concavo-convex pits. And the step of forming the information recording layer of (1) to produce a desired multilayer optical recording medium.

[0012]

As described above, in the structure of the present invention, since the transparent sheet spacer is interposed between the first and second information recording layers, the thickness thereof, and hence the intermediate layer interposed between both information recording layers, should be sufficiently large. In addition, even if the thickness is increased by using the sheet spacer, it is possible to form a uniform thickness over the entire surface. In addition, the process can be simplified as compared with the case where the resin layer or the like is repeatedly applied despite the increase in the thickness.

Further, the transparent intermediate layer interposed between the two information recording layers is not limited to the sheet spacer, but the transparent resin layer is interposed on the first information recording layer side. , For example, even if the first information recording layer is recording by concave-convex pits, it is filled with a material suitable for filling, and by a resin material having excellent adhesiveness between the first information recording layer and the sheet spacer. And for the sheet spacer, such filling properties,
Since it is not necessary to consider adhesiveness and the like, a sheet having a necessary and sufficient thickness and excellent flatness can be used.

[0014]

FIG. 1 is a schematic sectional view of an example of a multilayer optical recording medium according to the present invention. In this example, various information is recorded as concave and convex pits, and the so-called ROM-type multi-layered optical recording medium for audio and video other than that for reading the recorded information by light irradiation, especially the information recording layer is the first information. The case where the recording layer 1 and the second information recording layer 2 have a two-layer structure in which a transparent intermediate layer 3 is laminated is shown.

In the present invention, the transparent resin layer 32 is adhered to the first information recording layer 1 side, and the transparent intermediate layer 3 in which the transparent sheet spacers 31 are closely adhered is interposed on the transparent resin layer 32 to form the transparent sheet. The second information recording layer 2 is formed on the spacer.
Is formed.

In this example, the first information recording layer 1 is composed of the optical disk unit 11, and the second information recording layer 2 is composed of this by the photopolymerization method (hereinafter referred to as 2P method).

In order to facilitate understanding of this embodiment, an example of the manufacturing method thereof will be described with reference to the process chart of FIG. As shown in FIG. 2A, the optical disc section 11 on which the first information recording layer 1 is formed is manufactured by injection molding using a resin having a light transmitting property, for example, a transparent resin such as PC (polycarbonate). In this injection molding, for example, as shown in a sectional view of an example in FIG. 3, a metal stamper 41 in which an information uneven pattern corresponding to information to be recorded as a first information recording layer is formed in a cavity of a mold 40. That is, the master stamper is arranged, and the heat-melted PC is injection-molded in this cavity.

The optical disk unit 11 thus formed
On the first information recording layer 1, as shown in FIG. 2B, an optical layer 12 such as a SiN layer for controlling the first information recording layer 1 to have a required transmittance and reflectance is formed by, for example, sputtering. Formed by.

Thereafter, as shown in FIG. 2C, on the first information recording layer 1 of the optical disc section 11, the entire surface is excellent in adherence (adhesiveness) to the first information recording layer 1, and a transparent sheet spacer to be described later. 31 is coated with a transparent resin, for example, an ultraviolet curable resin, and a flat stamper having a flat surface, a so-called mirror stamper (not shown) is pressed from the surface side of the resin layer to remove the first resin. The concave and convex pits of the information recording layer are buried and filled with this transparent resin layer 32, and the surface thereof is flattened. Then, on the transparent resin layer 32, a light-transmissive sheet spacer 31 having a required thickness, for example, a film of polyethylene, polyester, or the like is entirely abutted, and from the surface thereof, for example,
The roller 50 heated to 0 ° C. is pressed and rolled over the entire surface so that the roller 50 is uniformly pressed and brought into close contact with the optical disk unit 11.

Thereafter, as shown in FIG. 2D, a second information recording layer is formed on the sheet spacer 31 by, for example, the 2P method. That is, in this case, for example, the stamper 14 on which the information uneven pattern corresponding to the information to be recorded as the second information recording layer is formed via the ultraviolet curable resin 33.
Is pressed against the optical disc unit 11 via the similar ultraviolet curable resin 33, and ultraviolet rays are irradiated from the back of the optical disc unit 11 to cure the ultraviolet curable resin 33. In this way, the transparent intermediate layer 3 having a thickness of, for example, 40 μm as a whole is formed by the previously formed filling layer 33, the sheet spacer 31, and the ultraviolet curable resin 33 for forming the second information recording layer 2. To do.

Then, the stamper 14 is eliminated. By doing so, as shown in FIG. 1, the second information recording layer 2 having a pattern in which the concavo-convex pattern of the stamper 14 is reversed.
Is formed. On the second information recording layer 2, a reflective film 15 made of an Al vapor deposition film or the like is formed, and a protective layer 16 made of a photocurable resin or the like is coated on the reflective film 15. In this way, the first
And the multi-layered optical recording medium according to the present invention in which the second information recording layers 1 and 2 are laminated is constituted.

When reading each record from each of the first and second information recording layers 1 and 2 of the thus obtained multi-layered optical recording medium, for example, as shown in FIG. It can be reproduced from the back surface of the same by reproducing light from the same optical pickup. For example, reproduction on the first information recording layer 1 is performed by irradiation with the irradiation light 21L focused on the first information recording layer 1, and is performed by irradiation with the irradiation light 22L focused on the second information recording layer 2. . At this time, it is desirable to select the light transmittance of the first information recording layer 1 to 30% to 80% and the reflectance of 20% to 50% by the optical layer 12 described above. The reflectance of the reflective film 15 can be selected to be 100%.

In the present specification, transparency, transmittance, reflection, reflectance and the like refer to irradiation light used for recording and / or reproducing of the finally obtained multilayer optical recording medium.

In the above-mentioned example, the second information recording layer 2 has two layers.
Although it is formed by the P method, as shown in FIG. 4, the surface of the sheet spacer 31 opposite to the first information recording layer may be formed by press working so-called embossing. In this case, the sheet spacer 31 can be made of, for example, an acrylic resin film having a certain viscosity.

In FIG. 4, portions corresponding to those in FIG. 2D are designated by the same reference numerals, and duplicate description will be omitted. Also in the example shown in FIG. 4, although not shown, a reflective film 15 such as an Al vapor deposition film similar to that described above is formed on the second information recording layer 2.
And the protective layer 16 is formed thereon.

Also in each of the above examples, the intermediate layer 3
Since the sheet spacer 31 is interposed, the sheet spacer 31 is preliminarily used as a sheet having a uniform and required thickness to make the intervals between the information recording layers uniform and to keep the intervals sufficiently large. be able to.

Further, in the above-mentioned example, the case of obtaining the multi-layered optical recording medium having the two-layer structure of the first and second information recording layers 1 and 2 is explained, but it is applied to the case of the constitution of three or more layers. Alternatively, the formation of each information recording layer is not limited to the injection molding method, the 2P method, the embossing method, or the like, and various manufacturing methods can be adopted.

In the above example, the present invention is applied to a multi-layered optical recording medium having a ROM type structure. However, a multi-layered optical recording / reproducing system such as magneto-optical recording or phase change recording is possible. The same effect can be obtained by being applied to the production of a multilayer structured optical recording medium having various structures such as being applicable to a structured optical recording medium.

[0029]

As described above, according to the configuration of the present invention,
Since the transparent sheet spacer is interposed between the first and second information recording layers, the thickness thereof, and therefore the intermediate layer interposed between both information recording layers, can be made sufficiently large, and the sheet spacer is used. By this, it is possible to form a uniform thickness over the entire surface although the thickness is increased. In addition, the process can be simplified, mass productivity can be improved, and cost can be reduced as compared with the case where the resin layer and the like are repeatedly applied despite the increase in thickness. .

Further, the transparent intermediate layer interposed between the two information recording layers is not limited to the sheet spacer, but the transparent resin layer is interposed on the first information recording layer side. , For example, even if the first information recording layer is recording by concave-convex pits, it is filled with a material suitable for filling, and by a resin material having excellent adhesiveness between the first information recording layer and the sheet spacer. And for the sheet spacer, such filling properties,
Since there is no need to consider adhesiveness, etc., a sheet with a necessary and sufficient thickness and excellent planarity can be used, and recording or / and reproduction that can avoid irradiation light interference between multiple information recording layers. A multilayer optical recording medium having excellent characteristics and high reliability can be constructed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a multilayer optical recording medium according to the present invention.

FIG. 2 is a process drawing of an example of a method for manufacturing a multilayer optical recording medium according to the present invention. A is a cross-sectional view of one step. B
[Fig. 3] is a sectional view of a step. C is a cross-sectional view of one step.
D is a cross-sectional view of one step.

FIG. 3 is a schematic cross-sectional view of an example of an injection molding apparatus used for manufacturing the multilayer optical recording medium according to the present invention.

FIG. 4 is a schematic cross-sectional view of a manufacturing process for explaining another example of the multilayer-structured optical recording medium according to the present invention.

FIG. 5 is a schematic cross-sectional view of a multi-layered optical recording medium contrasted with the present invention.

[Explanation of symbols]

 1 First Information Recording Layer 2 Second Information Recording Layer 3 Intermediate Layer 11 Optical Disc Section 12 Optical Layer 31 Sheet Spacer 15 Reflective Film 16 Protective Layer 40 Mold 41 Metal Stamper

Claims (3)

[Claims] 1. A transparent resin layer formed by laminating at least a first information recording layer and a second information recording layer, and between the first and second information recording layers and on the side of the first information recording layer. And a transparent intermediate layer in which a transparent sheet spacer is adhered to the transparent resin layer is interposed, and the second information recording layer is formed on the transparent sheet spacer. recoding media. 2. A step of producing an optical disk portion on which a first information recording layer is formed by the concave and convex pits by injection molding, and a photo-polymer using a flat stamper having a flat surface by embedding the concave and convex pits on the optical disk portion. A step of forming a transparent resin layer having a flattened surface by a malization method, a step of bringing a transparent sheet spacer into close contact with the transparent resin layer, and an uneven pit formed on the transparent sheet spacer by a photopolymerization method. And a step of forming a second information recording layer by the method described above. 3. A step of producing an optical disk portion on which a first information recording layer is formed by the concave and convex pits by injection molding, and a photo-polymer using a flat stamper having a flat surface by embedding the concave and convex pits on the optical disk portion. A step of forming a transparent resin layer whose surface is flattened by a malization method; a step of bringing a transparent sheet spacer into close contact with the transparent resin layer; A method of manufacturing a multi-layered optical recording medium, comprising the step of forming a recording layer.