JPH08124224A - Production of optical disc - Google Patents

Abstract

PURPOSE: To prevent defective reproduction characteristics by preparing a sheet- like translucent board having a thermoplastic resin layer, thermally pressing a stamper against the board thereby transferring the protrusions and recesses of information signal pit thereto. CONSTITUTION: A thermoplastic resin layer 2 is laminated onto a translucent board 1 to extrude a laminate of a sheet-like board 1 having a layer 2. A stamper 6 having protrusions and recesses 105 representative of information is then thermally pressed against the surface of the resin layer 2 in order to transfer the protrusions and recesses 105 thus forming protrusions and recesses 5 on the resin layer 2. A reflective film 3 and a protective film 4 are then formed sequentially on the resin layer 2 provided with the protrusions and recesses 5. It is aligned with reference to the protrusions and recesses 5 of information signals transferred onto the resin layer 2 and the outer circumferential part and a central hole 9 are punched by means of a cutter 10 thus producing a disc from the sheet-like board. This method eliminates lamination of the resin layer 2 on the board 1 during production process thus preventing defective reproduction characteristics or external view due to defective lamination while making uniform the birefringence.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical disk, and more specifically, it can mass-produce an optical disk having excellent optical characteristics and mechanical characteristics efficiently and at low cost. The present invention relates to a method for manufacturing an optical disc that does not need to be laminated and can prevent defective reproduction characteristics and appearance due to defective lamination of films.

[0002]

2. Description of the Related Art Optical discs that reflect irradiated laser light in accordance with recorded information signals have come to be widely used as recording media for, for example, audio and video.

For example, as shown in FIG. 5, as a structure of this optical disk, a reflection film 3 for reflecting light is formed on a light-transmissive substrate 1 on which irregularities 5 such as pits and grooves corresponding to information signals are directly formed. Is generally laminated, and a protective film 4 is further laminated on the reflective film 3 in general. And
Conventionally, in the manufacture of optical disks, a synthetic resin such as polycarbonate is used as a raw material, and injection molding is performed using a mold having a built-in stamper, which is a master for information signals, to manufacture a light-transmissive substrate and to form irregularities, which are information signals. (Duplicate)
Were going at the same time.

However, in the case of the above-mentioned manufacturing method, it is necessary to heat and melt the raw material resin, inject it into the mold containing the stamper, and cool it while applying a considerably high pressure. For this reason, the process is complicated and the manufacturing equipment becomes large-scale, the mechanical characteristics are deteriorated due to the warp of the light-transmissive substrate, and the birefringence of the molded product is caused by the flow strain and the uneven pressure distribution during the process. There is also a problem in that the optical characteristics are deteriorated due to non-uniformity and the like. In particular, when performing high-density recording / reproduction, how to improve mechanical properties and optical properties becomes more important in order to improve the performance of the optical disc.

On the other hand, if the cooling time in the injection molding process is sufficient, non-uniformity of birefringence can be reduced to some extent, but it is also necessary to shorten the process time and molding cycle to improve the production efficiency. It is required to shorten the time as much as possible.

Therefore, an optical disk transfer sheet obtained by laminating a thermoformable resin layer on a substrate and heating and pressing a stamper on the surface of the thermoformable resin layer to transfer the unevenness as an information signal is a transparent acrylic resin. A method of manufacturing an optical disk by adhering it to a light-transmissive substrate such as a plate has been proposed (Japanese Patent Laid-Open No. 1-138636). According to this method, the steps can be simplified, the scale of the manufacturing apparatus can be reduced, and the birefringence of the light transmissive substrate can be reduced.

However, in this method, bubbles are trapped between the light transmissive substrate and the optical disc transfer sheet at the stage of laminating the optical disc transfer sheet separately prepared on the light transmissive substrate. There is a problem in that the light-transmissive substrate and the optical disk transfer sheet may be poorly adhered to each other, or wrinkles may be generated in the optical disk transfer sheet, resulting in defective reproduction characteristics and appearance.

[0008]

SUMMARY OF THE INVENTION The present invention was devised in view of the above circumstances, and an object thereof is to mass-produce optical disks having excellent optical characteristics and mechanical characteristics efficiently and at low cost. It is an object of the present invention to provide a method for manufacturing an optical disc that does not require a film to be laminated on a light-transmissive substrate in the process and can prevent defective reproduction characteristics and appearance due to defective lamination of films.

[0009]

In order to solve the above-mentioned problems, in the present invention, (a) a light having a thermoplastic resin layer formed by laminating a thermoplastic resin layer on a light-transmissive substrate and having a sheet shape. The first step of producing a transparent substrate by co-extrusion lamination, and (b) transferring the irregularities by heating and pressing a stamper having irregularities on the surface of the thermoplastic resin layer. The second step,
(C) The method for producing an optical disk is configured so as to include a third step of laminating a reflective film and a protective film on the surface of the thermoplastic resin layer having the irregularities transferred in the second step.

[0010]

In the present invention, the resin for the light transmissive substrate and the resin for the thermoplastic resin layer are first prepared without simultaneously producing the light transmissive substrate and forming (reproducing) the irregularities such as pits which are information signals. By using the above as a raw material and performing co-extrusion lamination, a thermoplastic resin layer having a sheet shape and a structure in which a thermoplastic resin layer serving as an unevenness forming layer is simply laminated on a light-transmissive substrate having no unevenness and having a sheet-shaped thermoplastic resin layer After manufacturing the transparent substrate, the unevenness is transferred to the surface of the thermoplastic resin layer by heating and pressing a stamper on which information is formed in the shape of unevenness, so that the process and condition setting are simplified and the manufacturing apparatus is simplified. Can be made smaller.

Further, when the unevenness is directly formed on the light transmissive substrate, it is necessary to perform injection molding under high pressure using a complicated mold having the unevenness. In the present invention, such an injection is performed. Since there is no need to perform molding, the mechanical properties of the light transmissive substrate are not deteriorated, and on the other hand, flow distortion and uneven pressure distribution are less likely to occur during the production of the light transmissive substrate. Less likely to cause uneven refraction,
There is no need to take a long cooling time.

Therefore, it becomes possible to mass-produce optical discs having excellent optical characteristics efficiently and at low cost. Furthermore, in the present invention, since the thermoplastic resin film is not laminated on the light-transmitting substrate, but the light-transmitting substrate with the thermoplastic resin layer is produced by coextrusion lamination,
No bubbles are entrapped between the light-transmissive substrate and the thermoplastic resin layer, poor adhesion between the light-transmissive substrate and the thermoplastic resin layer occurs, or wrinkles do not occur in the thermoplastic resin layer. Therefore, it is possible to prevent defective reproduction characteristics and appearance due to defective lamination of the film that becomes the unevenness forming layer.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of an optical disc obtained by the manufacturing method of the present invention. A thermoplastic resin layer 2 having concavities and convexities 5 corresponding to information signals formed on a light-transmissive substrate 1. , The reflective film 3 and the protective layer 4 are sequentially stacked. Although FIG. 1 shows an optical disc in which pits are formed as irregularities 5 corresponding to information signals on the thermoplastic resin layer 2, grooves may be formed in the thermoplastic resin layer 2. The shape and size of the optical disc are appropriately determined according to the application of the optical disc. For example, in the case of a compact disc (CD), the diameter is 120 mm and the diameter is 15 mm at the center.
It has a disk shape with a central hole of mm, and its thickness is usually
It is about 1.2 mm.

FIG. 2 is an explanatory view showing an example of the steps of the method for manufacturing an optical disk of the present invention, more specifically an explanatory view showing the steps for manufacturing the compact disk (CD). In the method of the present invention, first, as shown in FIG. 2A, a thermoplastic resin layer-containing light-transmissive substrate having a sheet-shaped thermoplastic resin layer 2 is laminated on a light-transmissive substrate 1. , Co-extrusion lamination (first step). As a light-transmissive substrate with a thermoplastic resin layer for producing a compact disc (CD), for example, a polycarbonate substrate having a thickness of 1.1 to 1.2 mm, preferably 1.15 mm, has a thickness of 25 to 100 μm. Preferably, an acrylic polymer layer having a thickness of 50 μm is laminated, and a laminate having a sheet shape having a size capable of adjusting the outer peripheral shape into a disk shape having a diameter of 120 mm by punching or the like is produced.

The light-transmitting substrate 1 may be made of any material having light-transmitting properties, such as polycarbonate (PC) and polymethylmethacrylate (PMMA).
And transparent materials such as optical glass.
Among various transparent materials, polycarbonate (PC) is preferably used because it has excellent environment resistance and dimensional stability.

Concavities and convexities 5 corresponding to information signals such as pits are transferred to the thermoplastic resin layer 2 in the second step described later. The resin forming the thermoplastic resin layer 2 has good adhesiveness to the light-transmissive substrate 1, and the unevenness can be accurately duplicated by pressure contact of the stamper, and it is difficult for the resin to be damaged or deformed after duplication. desirable. A suitable thermoplastic resin layer has a thickness of 25 to 100 μm, preferably 5
A 0 μm acrylic polymer layer can be exemplified.
Here, the acrylic polymer is a mixture of polymethylmethacrylate resin (PMMA) and acrylic rubber-based resin, and "Acryprene HBE" manufactured by Mitsubishi Rayon Co., Ltd.
And "Acryprene HBS" etc. correspond to this. In addition,
When the unevenness forming layer is formed of a thermoplastic resin as in the present invention, unevenness such as pits on the stamper in the second step described below is transferred by thermal deformation of the surface of the thermoplastic resin layer, and after the stamper is peeled off. Since the thermoplastic resin layer is immediately cooled in the atmosphere and the unevenness which is the information signal remains on the resin layer as it is, compared with the case where the dry photocurable resin which requires the curing step by ultraviolet irradiation is used as the unevenness forming layer. Can be efficiently transferred.

In the present invention, the light transmissive substrate with the thermoplastic resin layer is produced by coextrusion lamination as described above. For example, in the case of producing the above-mentioned polycarbonate substrate with an acrylic polymer layer, an apparatus as shown in FIG. 3 is used, and a polycarbonate resin (melt flow rate according to JIS K6719 is 57.2 g / 1
0 minutes) and acrylic polymer (melt flow rate is JI
21 g / 10 min according to SK6717) was melted and extruded from the T-die to form a laminate,
It may be cut into a predetermined size. When performing co-extrusion lamination, it is desirable that the extrusion sheet molding temperature of the resin for the thermoplastic resin layer and the resin for the light-transmissive substrate are as close to each other as possible. From this point of view, a combination of an acrylic polymer (for a thermoplastic resin layer) and a polycarbonate (for a light transmissive substrate) is preferable, but other preferable combinations include vinyl chloride (for a thermoplastic resin layer) and a polycarbonate. (For transparent substrate)
And the like can be exemplified.

Next, as shown in FIG. 2B, the stamper 6 having information in the form of unevenness 105 is heated on the surface of the thermoplastic resin layer 2 laminated on the light transmissive substrate. By press contacting, unevenness is transferred (second step). In order to transfer, the both may be pressed by a suitable method to separate the stamper.

The method of pressing the stamper onto the surface of the thermoplastic resin layer 2 is not particularly limited, and other than the pressure roller method shown in FIG. 2 (b), for example, the flat pressure method shown in FIG. 4 is adopted. May be. When the transfer is performed by the pressure roller method, the light-transmissive substrate with the thermoplastic resin layer and the stamper 6 are inserted between the over roll 7 and the under roll 8 and pressure contact is gradually made linearly from the end. As a result, air is unlikely to be trapped between the two, and the appearance and reproduction characteristics are improved.

For example, in the case of the polycarbonate substrate with an acrylic polymer layer obtained in the above first step,
The surface temperature of a metal stamper such as nickel (Ni) is set to 80
To 140 ° C., preferably 80 to 120 ° C., particularly preferably 110 ° C., and a pressing force of 45 to 200 kg / cm ² ,
It is preferably 90 kg / cm ² , and thermal transfer is preferably carried out by a pressure roller method. Here, the surface temperature of the stamper 6 is set to 80 to 120 ° C. in order to ensure a sufficiently high temperature for transferring onto the acrylic polymer layer within a range not exceeding the heat deformation temperature of polycarbonate (around 140 ° C.). Is.

The uniformity of transfer depends on the surface temperature of the stamper,
It depends on the heat deformation temperature of the thermoplastic resin layer, the applied pressure, the thickness of the film, and the like. According to the above specific example,
The surface temperature of the stamper 6 needs to be high so that the thermoplastic resin layer 2 can be sufficiently deformed. However, if the surface temperature is raised too high and becomes close to or above the heat deformation temperature of the polycarbonate substrate, the light transmissivity is increased. Since the substrate (polycarbonate substrate) 1 is thermally deformed and mechanical properties such as warpage are deteriorated and birefringence is deteriorated, it is preferable to suppress the temperature to 120 ° C. or lower. The heat deformation temperature of the acrylic polymer is preferably 100 ° C. or lower from the viewpoint of sufficiently transferring at a stamper surface temperature of 120 ° C. or lower, and when the heat deformation temperature is 70 ° C. or lower, the heat resistance guarantee of the optical disk as a product is guaranteed. Since it is often impossible to clear the temperature, 7
It is preferably 0 ° C. or higher.

When the unevenness 5 is duplicated by thermal transfer, the depth of the unevenness 5 formed on the thermoplastic resin layer 2 is closely related to the stamper temperature, the transfer pressure, and the pressurizing time. And the highest value in pressurization time. Further, when the stamper 6 is peeled from the thermoplastic resin layer 2, the thermoplastic resin layer 2 undergoes thermal contraction, so that the depth of the unevenness 5 decreases. For these reasons, the reproduction signal can be optimized by adjusting the depth of the unevenness 105 of the stamper 6, which is the master, in advance.

Further, when the transfer is carried out by the plane pressing method shown in FIG. 4 to the polycarbonate substrate with the acrylic polymer layer obtained in the first step, it is heated to about 110 ° C. and is sufficiently thick. Stamper 6 on the lower flat plate 17
The light-transmitting substrate with the thermoplastic resin layer on the stamper so that the surface of the stamper 6 and the thermoplastic resin layer 2 face each other, and the pressure is released at 80 kg / cm ² or more and then the pressure is released. Then, the stamper and the light-transmissive substrate with the thermoplastic resin layer are immediately peeled off.

The temperature of the lower flat plate 17 to which the stamper adheres is preferably high enough to transfer the unevenness 5 to the surface of the acrylic polymer layer, but this temperature is near the heat deformation temperature of the polycarbonate substrate. If it is more than that, the light transmissive substrate (polycarbonate substrate) 1 is thermally deformed to cause deterioration of opportunity characteristics such as warpage and deterioration of birefringence. Pressing force and pressing time are also important factors, but when the pressing force is 80 kg / cm ² and the pressing time is 3 seconds, mechanical properties and birefringence can be obtained if the stamper surface temperature is maintained at 100 to 110 ° C. Is not seen to deteriorate.

In this method, a cushion 19 such as soft rubber is attached to the lower surface of the upper flat plate 18 so as not to scratch the surface of the light transmissive substrate 1. In particular, if a foamable resin plate that expands and contracts only in the pressing direction is used as the cushion 19, it is possible to prevent many scratches from being radially generated from the center on the reading surface of the optical disc. Examples of the foamable resin plate that expands and contracts only in the pressing direction include foamed polyurethane and the like, and the thickness thereof is usually 0.2 to 2.0 mm, preferably 0.5 to 1. It is 0 mm.

Next, as shown in FIG. 2C, a reflective film 3 is formed on the thermoplastic resin layer 2 on which the irregularities 5 of the information signal are transferred, and a protective film 4 is formed on the reflective film 3. . Reflective film 3
Examples of the forming material include aluminum (Al), aluminum (Al) alloy, gold (Au), silver (Ag), copper (Cu), and the like. Among these, aluminum (Al) and aluminum (Al) alloy are preferable. Examples of the method of forming the reflective film 3 include a sputtering method, a vacuum vapor deposition method, an ion plating method and the like. The thickness of the reflective film 3 is usually 0.03.
˜0.1 μm, preferably 0.03 to 0.05 μm.

Examples of the material for forming the protective film 4 include epoxy resin, acrylic resin, silicone resin, urethane resin, ethylene-vinyl acetate copolymer resin and the like. Further, this protective film 4 is formed by a so-called 2P (photo poly
It may be an ultraviolet curable resin applied by a marization method. The thickness of such a protective film 4 is usually 5 to 1
The thickness is 00 μm, preferably 5 to 20 μm.

In the manufacturing method of the present invention, the shape and shape of the sheet-shaped light-transmitting substrate with the thermoplastic resin layer are punched at the outer peripheral portion and the central portion at any stage after the above first step. The size is adjusted to form a disk shape having the outer diameter of the optical disk and the center hole 9 when completed. The processing of this shape and size may be performed at any stage after the sheet-shaped light-transmitting substrate with the thermoplastic resin layer is produced, but normally, as shown in FIG. In the process, after the alignment is performed with reference to the information signal transferred onto the thermoplastic resin layer 2 or the like, the outer peripheral portion and the central hole 9 are punched out by the cutter 10 or the like. For example, an outer diameter of 120 mm and a thickness of about 1. are punched by punching out the outer peripheral portion and the center hole of the polycarbonate substrate with the acrylic polymer film layer on which unevenness has been transferred, which is obtained by the pressure roller method or the flat pressure method in the second step. A disc-shaped compact disc (CD) having a central hole 9 with a diameter of 2 mm and a diameter of 15 mm in the center is obtained.

[0029]

According to the method of the present invention, a thermoplastic resin having a structure in which a thermoplastic resin layer serving as an unevenness forming layer is simply laminated on a light-transmissive substrate having no unevenness by performing coextrusion lamination. Create a light-transmitting substrate with a resin layer,
After that, since the irregularities such as pits which are information signals are transferred, there is a case where the light-transmissive substrate is produced and the irregularities are simultaneously formed on the substrate by injection molding under high pressure using a complicated mold having irregularities. In comparison, each step in the manufacturing process can be performed under advantageous conditions, the cooling time at the time of molding the substrate can be shortened, and the birefringence of the optical disk can be easily made uniform. Therefore, according to this method,
Optical disks having excellent optical characteristics can be mass-produced efficiently and at low cost.

Further, in the method of the present invention, a light-transmissive substrate in which a thermoplastic resin layer is laminated directly from a resin for a light-transmissive substrate and a resin for a thermoplastic resin layer is directly produced by coextrusion lamination, and therefore, it is separately prepared. Unlike the case where the produced thermoplastic resin film is laminated on the light transmissive substrate, it is possible to prevent the reproduction characteristics and the appearance from being defective due to the lamination failure of the film.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a layer structure of an optical disc obtained by an optical disc manufacturing method of the present invention.

FIG. 2 is an explanatory diagram showing an example of steps of the optical disc manufacturing method of the present invention.

FIG. 3 is an explanatory diagram showing an example of a co-extrusion laminating apparatus.

FIG. 4 is an explanatory diagram showing an example of a concave-convex transfer process by a pressure plate method.

FIG. 5 is a schematic sectional view showing an example of a layer structure of a conventional optical disc.

[Explanation of symbols]

 1 ... Light transmissive substrate 2 ... Thermoplastic resin layer 3 ... Reflective film 4 ... Protective film 5 ... Roughness on thermoplastic resin layer 105 ... Roughness on stamper 6 ... Stamper 7 ... Over-roll 8 ... Under-roll 9 ... Center Hole 10 ... Cutter 11 ... Extruder 12 ... Extruder 13 ... T-die 14 ... Pressure roll 15 ... Cooling roll 16 ... Guide roll 17 ... Lower metal flat plate 18 ... Upper metal flat plate 19 ... Cushion p ... Pressing force

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshitaka Nonaka 2680 Nishi Hanawa, Tatomi-cho, Nakakoma-gun, Yamanashi Pioneer Video Co., Ltd. (72) Inventor Ayumi Mimori 2680 Nishi Hanawa, Tatomi-cho, Yamanashi Prefecture Pioneer Video Within the corporation

Claims (1)

[Claims] 1. A first step of producing a light-transmitting substrate with a thermoplastic resin layer, which has a sheet shape by laminating a thermoplastic resin layer on a light-transmitting substrate, by co-extrusion lamination, and the thermoplastic resin. The second step of transferring the unevenness by heating and pressing a stamper on which information is formed in the shape of unevenness on the surface of the layer, and a reflective film on the surface of the thermoplastic resin layer to which the unevenness is transferred in the second step. And a third step of laminating a protective film, the method for producing an optical disc.