JPH09147417A - Optical recording medium and manufacturing method thereof - Google Patents

Abstract

(57) An object of the present invention is to provide an optical disk having a thin light transmission layer capable of high recording density and a manufacturing method thereof. SOLUTION: The light transmissive layer 3 made of a light transmissive member has a surface opposite to a surface on which a laser beam 10 for recording / reproducing is incident, and is provided on the information recording surface of the light transmissive layer 3. The optical disc 100 is composed of the reflective film 2 and the disc substrate 1 attached to the reflective film 2 and sufficiently thicker than the light transmission layer 3. A long roll-shaped transfer sheet is used as a member of the light transmission layer 3, a step of transferring the recording information by pressing a stamper on which the recording information is formed onto the transfer sheet, and irradiating the transfer sheet with ultraviolet rays. It comprises a step of curing, a step of forming the reflective film 2 on the information recording surface of the cured transferable sheet, and a step of cutting the portion where the reflective film 2 is formed into the shape of the optical disc 100. A method for manufacturing an optical disc, which comprises the steps of applying an adhesive member 8 to the cut surface of the light transmitting layer 3 on which the reflective film 2 is formed and adhering the disc substrate 1 thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and a method for manufacturing the same, and more particularly to a structure of an optical recording medium having an extremely thin light transmitting layer for transmitting light and a method for manufacturing the same.

[0002]

2. Description of the Related Art The structure of a reproducing optical disk, which is a type of conventional optical recording medium, and the manufacturing method thereof will be described with reference to FIGS. FIG. 4 is a sectional side view showing a general conventional optical disc, and FIG. 5 is a sectional side view of an example of an optical disc having a thin light transmitting layer. FIG. 6 is a diagram showing a master disc manufacturing process in the optical disc manufacturing process. FIG. 7 is a diagram showing an injection molding process in the manufacturing process of the optical disk shown in FIG. 5, and FIG. 8 is a diagram showing a process of forming a reflective film and a light transmitting layer in the manufacturing process of the optical disk shown in FIG. FIG. 9 is a diagram for explaining the formation of the light transmitting film in the manufacture of the optical disc shown in FIG.

As shown in FIG. 4, the structure of a conventional general optical disc 110 is such that a signal recording portion is formed by carving an information pit 23 or a guide groove 24 on one surface of the light transmitting layer 3, and this signal recording portion is formed. The reflection film 2 covering the part and further the reflection film 2
A protective film 7 for protecting the reflective film 2 is applied to the outside of the structure. The thickness t _{1 of} this optical disk 110
Is about 1.2 mm, which is almost the thickness of the light transmitting layer 3. After passing through the light transmitting layer 3, the information pit 23 or the guide groove 24 is irradiated with the laser light 10 condensed by the objective lens 11 for the reproducing pickup,
Information is recorded and reproduced.

For example, in the duplication process after the mastering process in the process of manufacturing a compact disc, the stamper produced in the mastering process is attached to the molding machine, and then the resin of the substrate material such as polycarbonate is heated. While being injected into the molding machine, the resin is compression-molded to transfer the information pit 23 and the guide groove 24 onto the substrate. This substrate is the light transmission layer 3, and the surface on which the information pit 23 and the guide groove 24 are formed is coated with aluminum by a vacuum deposition method to form the reflection film 2 so that the reflection film 2 is not deteriorated. The protective film 7 is formed by being covered with resin and solidified.

Therefore, when viewed from the reproduction pickup side,
The objective lens 11 irradiates the information pit 23 with the laser light 10 through the 1.2 mm light-transmitting layer 3, and the reflected light from the information pit 23 is also condensed by the objective lens 11 to generate a photoelectric conversion element (not shown). The information is read out by converting it into an electric signal in step (d).

The thickness of the light transmitting layer 3 has a great influence on the relationship between the inclination of the optical disk 110 and the coma aberration of the laser light. When the inclination of the optical disk 110 is constant, the light transmission layer 3 has a small thickness. The transmission layer 3 forms a spot with less aberration on the information pit 23.

Now, the relationship between the thickness of the optical disk and the aberration will be described. NA of the objective lens,
When the wavelength of the irradiation laser beam that forms the reproduction spot is λ and the spot size is φ, there is a relation of φ = 1.22 × λ / NA (1). From this equation (1), it can be seen that the spot size φ can be reduced by increasing the numerical aperture NA. Therefore, by using a lens having a large numerical aperture NA, it is possible to reproduce information recorded at high density.

However, the numerical aperture NA is the spot size φ.
In addition, the tolerance for the tilt of the disc is also determined. That is, the tolerance for the inclination of the disk is proportional to λ / [t · (NA) ³ ] (2). Here, t is the thickness of the light transmission layer.

[0009] Generally, when a disk tilts, coma aberration occurs, the wavefront aberration coefficient W is, W = 1/2 · t · [(N ² -1) N ² sinθcosθ] ÷ [(N ² -sin ² θ ) ^-5/2・ NA ³ ] (3). Here, t is the thickness of the light transmitting layer, N is the refractive index of the light transmitting layer, and θ is the tilt angle.

For example, when the NA is changed from 0.45 to 0.60, the skew margin becomes 0.60 ° to 0.
It decreases to 25 °. In order to recover this margin, the thickness t of the light transmitting layer may be reduced. However, conventionally, as described above, the light transmission layer is 1.2 mm.
Therefore, it has been difficult to increase the numerical aperture NA of the objective lens from the viewpoint of working distance. That is, with this thickness of the light transmitting layer, it was difficult to realize higher density recording / reproducing with high quality.

However, with the recent advance in information technology, an optical disc having a high recording density is being demanded, and in order to cope with this, the development of an optical disc in which the numerical aperture NA of the objective lens is increased and the track pitch is reduced. Is being promoted. However, as the numerical aperture NA of the objective lens is increased, as described above, the amount of spot aberration with respect to a constant disc tilt and the resulting deterioration of the reproduction signal increase. In an optical disc having a light transmitting layer, it is necessary to use a material, such as a glass substrate, which is extremely flat and does not deform as the substrate.

On the other hand, by the inventors of the present application, Manabe, Kashiwagi and others have proposed a structure and manufacturing method of an optical disk having an extremely thin light transmitting layer in order to address the above-mentioned problems (Japanese Patent Application No. 7-37023). . Next, the structure of the proposed optical disk having an extremely thin light transmitting layer and the manufacturing method thereof will be described with reference to FIGS.

FIG. 5 is a cross-sectional side view of the optical disk 120. The disk substrate 1 occupies the thickness t ₁ (1.2 mm) of the optical disk, the information pit 23 and the guide groove 2.
4 and a thin light transmitting layer 3 formed thereon. The disc substrate 1 is made of polycarbonate, for example, and the information pits 23 and the guide grooves 24 are transferred by an injection molding method. The reflective film 2 is sputtered on the information pits 23 and the guide grooves 24 of the disc substrate 1. About 5 aluminum
The light-transmitting layer 3 has a thickness of 0 nm.
Is an ultraviolet curable resin applied on the reflective film 2 with a thickness of about t ₂ = 0.1 mm by spin coating.

Therefore, when viewed from the reproduction pickup side,
The objective lens 11 irradiates the information pit 23 with the laser beam 10 through the light transmission layer 3 having a thickness of 0.1 mm, and the reflected light from the information pit 23 is also condensed by the objective lens 11 to generate a photoelectric conversion element (not shown). The information is read out by converting it into an electric signal in step (d).

In order to manufacture the optical disk 120, the master disk manufacturing process shown in FIG. 6, the injection molding process shown in FIG. 7, and the reflection film formation and light transmission layer formation processes shown in FIG. 8 are necessary.

Next, each process will be described. First, in the master board manufacturing process, a resist 21 is applied to the glass master disk 20 shown in FIG. 6A (FIG. 6B),
After exposure with the laser beam 22 [FIG. 6 (c)], the information pits 23 and the guide grooves 24 obtained by the development processing [FIG. 6 (d)] are subjected to electroless plating treatment to form a conductive thin film. After forming 25 [FIG. 6 (e)], electrolytic plating treatment is performed to form the Ni master board 26 [FIG. 6 (e)].
(F)] process. The Ni master board 26 is used in the injection molding process which is the next step after being peeled from the glass master disk 20 [FIG. 6 (g)].

Next, the injection molding process is shown in FIG.
As shown in FIG. 1, after the Ni master plate 26 serving as a stamper is mounted in the molding machine 15 including the first molding die 15a and the second molding die 15b, the disc substrate molding portion 13 formed in the molding machine 15 is mounted. Inject the resin 5 melted at high temperature,
This is a step of forming the disk substrate 1 by compression molding as shown in FIG. The resin 5 is made of polycarbonate resin or the like.

Next, the process of forming aluminum on the disk substrate 1 by sputtering to form the reflection film 2 and then forming the light transmission layer 3 on the reflection film 2 will be described with reference to FIG. .

First, aluminum is deposited on the disk substrate 1 by sputtering to a thickness of about 50 nm [FIG.
(A)], the reflection film 2 is formed [FIG. 8 (b)]. next,
Thickness of about 0.1 mm on the reflective film 2 by spin coating
The light transmission layer 3 is formed [FIG. 8 (c)]. In particular,
A UV resin, which is an ultraviolet curable resin, is applied by a spin coating method and UV cured to form the light transmitting layer 3.

However, when the spin coating method is used, the resin 6 is placed on the reflective film 2 of the disc substrate 1 as shown in FIG. 9, the disc substrate 1 is rotated in the direction indicated by the arrow R, and the resin is centrifugally applied. 6 is applied to the reflection film 2 with a uniform thickness, but it is difficult to apply a uniform thickness because the light transmission layer 3 is extremely thin as described above.

[0021]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical recording medium capable of high density recording / reproducing of information and a method of manufacturing the same, and particularly, an extremely thin light transmission medium. It is an object of the present invention to provide an optical recording medium having layers formed uniformly and flatly, and a manufacturing method for continuously and easily forming the optical recording medium.

[0022]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and an optical recording medium in which information is recorded and reproduced by a laser beam has at least a predetermined thickness and is for recording and reproduction. The surface opposite to the surface on which the laser light is incident is an information recording surface, a light transmitting layer made of a light transmitting member, a reflection film provided on the information recording surface of the light transmitting layer, and the reflection film. An optical recording medium is composed of the adhered substrate which is sufficiently thicker than the light transmitting layer.

The thickness of the light transmitting layer should be 0.5 mm or less. Alternatively, the thickness of the light transmitting layer may be about 0.1 mm.

The light transmitting layer should be formed of an ultraviolet curable resin.

A long transfer sheet having the same thickness as the light transmission layer and having a width wider than the width or diameter of the optical recording medium is used as a member of the light transmission layer, and at least the transfer sheet is used. A step of transferring a recording information by pressing a stamper on which recording information is formed on one surface, a step of irradiating the transfer sheet with ultraviolet rays in a state where the stamper is pressed, and curing, The method includes a step of forming a reflective film on the information recording surface of the transferable sheet by a sputtering method, and a step of cutting the portion where the reflective film is formed into the shape of an optical recording medium, and these steps are performed continuously. ,
A method for manufacturing an optical recording medium is used, which comprises a step of applying an adhesive member to the cut surface of the light transmitting layer on which the reflective film is formed and attaching the substrate.

The optical recording medium produced by the above manufacturing method has a disk shape or a card shape to solve the above problems.

Since the light transmitting layer of the optical recording medium is formed by using the transferable sheet having a predetermined thickness, an extremely thin and uniform light transmitting layer can be formed, and the numerical aperture of the pickup objective lens is large. It is possible to suppress the deterioration of the reproduction signal due to the coma aberration and enable high-density recording / reproduction.

Since the optical recording medium is continuously manufactured by using the roll-shaped transfer sheet as a material, the productivity is improved.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a structure and a manufacturing method of an optical recording medium (hereinafter referred to as "optical disk") having a thin light transmitting layer, and the structure is shown in FIG.
And a manufacturing method thereof will be described with reference to FIGS.

FIG. 1 is a sectional side view showing the structure of an optical disc according to the present invention, and FIG. 2 is a diagram showing a method for manufacturing an optical disc according to the present invention. FIG. 1 (a) is a roll-like transfer sheet. Is a step of forming information pits and guide grooves with a stamper, FIG. 7B is a step of irradiating a UV lamp to cure the sheet, and FIG. 7C is a step of forming a reflective film on the sheet with a sputtering device. It is a process of forming. FIG.
2 is a step following FIG. 2, FIG. 2D is a step of cutting the sheet into a disk shape by a cutter, FIG. 2E is a step of applying an adhesive member on the reflective film, and FIG. (F)
Is a step of adhering disc substrates to complete an optical disc.

The optical disc 100 of the present embodiment is provided on the light transmitting layer 3 having the information pits 23 and the guide grooves 24, as shown in FIG. 1, and the information recording surface of the information pits 23 and the guide grooves 24. The reflective film 2 is made of aluminum, and the adhesive member 8 is applied on the reflective film 2 and is fixed to the disk substrate 1. The thickness t ₁ (1.2 mm) of the optical disc is substantially equal to the thickness of the disc substrate 1, and the light transmission layer 3 is formed of an extremely thin layer (t ₂ = about 0.1 mm).

Therefore, when viewed from the reproduction pickup side,
The objective lens 11 irradiates the information pit 23 with the laser light 10 through the light transmission layer 3 having a thickness of about 0.1 mm, and the reflected light from the information pit 23 is also condensed by the objective lens 11 to generate a photoelectric conversion element (see FIG. The information is read out by converting it into an electric signal (not shown).

Next, the optical disc 100 according to the present invention.
The manufacturing method will be described with reference to FIGS. The manufacturing method of the present invention uses the light transmitting layer 3 and the information pits 23.
The method is characterized by the formation of the guide groove 24 and the reflection film 2, and the method of integrating these with the disk substrate 1 to realize the optical disk 100 having an extremely thin light transmission layer 3. Therefore, the master disc manufacturing process of the information pit 23 and the guide groove 24 is the same as the conventional example described with reference to FIG. 6, and the detailed description thereof is omitted here.

First, as shown in FIG. 2A, the light transmission layer 3
Uses a roll-like transferable sheet 16 made of an ultraviolet curable resin having a thickness of t ₂ = about 0.1 mm. This is pressed against the stamper 12 having the information pit 23 and the guide groove 24 formed by the method described in the conventional example, and the information pit 23 and the guide groove 24 are transferred to the roll-shaped transfer sheet 16.

Next, as shown in FIG. 2 (b), the stamper 12 is pressed against the roll-shaped transfer sheet 16, and U is pressed.
The roll-shaped transfer sheet 16 is cured by irradiating the V lamp 17 to fix the information pit 23 and the guide groove 24.

Next, as shown in FIG. 2C, in the sputtering device 18, the information pit 23 and the guide groove 24 are formed.
Reflective layer 2 by sputtering aluminum on the information recording surface of
To form These steps of FIGS. 2A to 2C are performed in a state where the roll-shaped transfer sheet 16 is continuous.

Next, as shown in FIG. 3D, a sheet having the information pits 23 and the guide grooves 24 formed continuously and the reflective layer 2 formed thereon is cut into 19 pieces.
To cut into an optical disk shape.

Next, FIG. 3 (e) shows a state in which an adhesive member is thinly applied onto the reflection layer 2 of a sheet cut into an optical disc shape, and for example, a polycarbonate which is also formed into an optical disc shape thereon. Disk substrate 1
Is placed and adhered and fixed [FIG. 3 (f)] to form an optical disc.

Therefore, by using the above-described manufacturing method, it is possible to continuously and easily manufacture the optical disc 100 in which the light transmitting layer 3 is extremely thin. Further, the disc substrate 1 is not required to have optical characteristics such as transmittance and birefringence, and is not limited to polycarbonate as long as it is a material that accurately holds the information pit 23 or the guide groove 24 and has sufficient mechanical strength. However, since it may be made of metal or glass, it is possible to manufacture a disk that is thin as a whole including the light transmission layer and has a small deformation.

Further, according to the optical disc 100 of the present embodiment, the light transmission layer 3 having a thickness of about 0.1 mm can be formed uniformly and flatly, and therefore the optical disc 1 on which the light transmission layer 3 is formed.
If 00 is used, even if the numerical aperture of the pickup objective lens 11 is increased, it is possible to suppress the deterioration of the reproduction signal due to the coma aberration, and it is possible to perform high density reproduction.

The optical recording medium and the method for manufacturing the same according to the present invention are not limited to the above-mentioned optical disc, but a double-sided type optical recording medium in which a light transmitting layer and a signal layer are provided on both sides of the disc substrate and the manufacturing thereof. It may be applied to the method. In addition, it goes without saying that the present invention may be applied to an optical recordable optical disc. Further, it is needless to say that the present invention is not limited to a disc and may be applied to a card-shaped optical recording medium.

[0042]

According to the present invention, therefore, it becomes possible to continuously and easily prepare an optical recording medium having a thin light-transmitting layer which is uniform and flat.

Further, in the optical recording medium having an extremely thin light transmitting layer according to the present invention, since the working distance of the pickup objective lens has a margin, an optical pickup device having a large numerical aperture can be used and the numerical aperture can be increased. Even if it is increased, since the light transmission layer is thin, it is possible to suppress the deterioration of the reproduction signal due to the coma aberration, so that it is possible to realize high density recording and reproduction.

Further, since the optical recording medium substrate may be made of metal or glass, it is possible to manufacture an optical recording medium which is thin as a whole including the light transmitting layer and has a small deformation.

[Brief description of the drawings]

FIG. 1 is a sectional side view showing a structure of an optical disc according to the present invention.

FIG. 2 is a diagram showing a method of manufacturing an optical disc according to the present invention, in which (a) is a step of forming information pits and guide grooves with a stamper on a roll-shaped transfer sheet,
(B) is a step of irradiating a UV lamp to cure the sheet, and (c) is a step of forming a reflective film on the sheet by a sputtering apparatus.

3 is a diagram showing a method of manufacturing an optical disc according to the present invention following FIG. 2, (d) is a step of cutting a sheet into a disc shape by a cutter, and (e) is an adhesive member on the reflection film. And (f) is a step of adhering disc substrates to complete an optical disc.

FIG. 4 is a sectional side view showing the structure of a conventional optical disc.

FIG. 5 is a sectional side view of another example of the optical disc.

FIG. 6 is a diagram showing a master disc manufacturing process in an optical disc manufacturing process.

FIG. 7 is a diagram showing an injection molding process in a manufacturing process of the optical disc shown in FIG.

8 is a diagram showing a process of forming a reflective film and a light transmitting layer in a manufacturing process of the optical disc shown in FIG.

9 is a diagram for explaining formation of a light transmitting film in manufacturing the optical disc shown in FIG.

[Explanation of symbols]

 1 Disc Substrate 2 Reflective Film 3 Light Transmission Layer 4 Center Hole 5 Resin 6 Resin 7 Protective Film 8 Adhesive Member 10, 22 Laser Light 11 Objective Lens 12 Stamper 13 Disc Substrate Molding Part 15 Molding Machine 16 Roll Transfer Sheet 17 UV Lamp 18 Sputtering device 19 Cutter 20 Glass master 21 Resist 23 Information pit 24 Guide groove 25 Conductive thin film 26 Ni master disc

Claims (7)

[Claims] 1. An optical recording medium in which information is recorded / reproduced by a laser beam, wherein at least a surface having a predetermined thickness and opposite to a surface on which a recording / reproducing laser beam is incident is an information recording surface. A light-transmitting layer formed of a light-transmitting member, a reflecting film provided on the information recording surface of the light-transmitting layer, and a substrate attached to the reflecting film and sufficiently thicker than the light-transmitting layer. An optical recording medium characterized by: 2. The optical recording medium according to claim 1, wherein the thickness of the light transmitting layer is 0.5 mm or less. 3. The optical recording medium according to claim 1, wherein the thickness of the light transmitting layer is about 0.1 mm. 4. The optical recording medium according to claim 1, wherein the light transmission layer is formed of an ultraviolet curable resin. 5. A long transfer sheet having the same thickness as the light transmission layer and having a width wider than the width or diameter of the optical recording medium is used as a member of the light transmission layer, and at least the transfer sheet A step of transferring the recording information by pressing a stamper on which recording information is formed on one surface of the recording sheet; and a step of irradiating the transferable sheet with ultraviolet rays in a state where the stamper is pressed and curing the recording sheet, The method includes a step of forming a reflective film on the information recording surface of the cured transferable sheet by a sputtering method, and a step of cutting the portion where the reflective film is formed into the shape of an optical recording medium, and these steps are continuously performed. 5. The optical recording medium according to claim 1, further comprising a step of applying an adhesive member to the cut surface of the light-transmitting layer on which the reflective film is formed and adhering the substrate. Manufacturing method. 6. The method of manufacturing an optical recording medium according to claim 5, wherein the optical recording medium has a disk shape. 7. The method of manufacturing an optical recording medium according to claim 5, wherein the optical recording medium has a card shape.