JPH0773512A - Production of optical disk - Google Patents

Abstract

PURPOSE:To improve curing performance at the time of forming a protective film, to shorten the time required to cure an uncured resin layer and to shorten the cycle time of a producing device. CONSTITUTION:A recording film is formed on a transparent substrate and a protective film of a UV-curing resin is formed on the recording film. At this time, a cup-shaped reflecting body 9 for converging light radiated from a UV radiating means 4 on the side of the peripheral part of the substrate is used, the substrate 8 is housed in the reflecting body 9 and an uncured resin layer is cured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disc having a protective film made of an ultraviolet curable resin on a recording film formed on a transparent substrate, and more particularly to improving the curing performance when the protective film is formed. .

[0002]

2. Description of the Related Art Optical discs, such as compact discs, magneto-optical discs, and mini discs, are portable (portable) media similar to floppy discs and are easy to handle, so that they can store a large amount of information. It is advantageous for processing. In recent years, the above optical disc has been widely used for audio recording and computer information recording.

This optical disc is generally constructed by forming a recording layer and a reflective layer on a transparent substrate injection-molded from a polycarbonate resin or the like, and further forming a protective film on the recording layer and the like.

The protective film is provided to protect the recording layer, and an ultraviolet curable resin is usually used as its constituent material. When forming this protective film, the spin coater method is suitable, and after supplying the above ultraviolet curable resin onto the disk substrate attached to the motor rotation shaft, the disk substrate is rotated at a high speed to form a coating film. By doing so, the resin is measured and the coating film is flattened. Next, the disc substrate is conveyed to the ultraviolet irradiation section, and the obtained coating film (uncured resin layer) is cured to form a protective film.

In such a system for forming a protective film made of an ultraviolet curable resin, if the uncured resin layer is sufficiently cured and if a resin substrate is used,
The substrate temperature after processing is lowered so as not to affect the optical characteristics (for example, about 80 in the case of a polycarbonate substrate).
It is desirable that the temperature is set to ℃ or less. ) Things are required.

[0006]

By the way, in the field of the above-mentioned optical disc, as the demand for the optical disc increases, the reduction of the price, the increase of the profit and the share of the optical disc become major problems. Therefore, it is necessary to take cost reduction measures such as shortening the cycle time of the manufacturing apparatus, improving the yield, and saving energy.

For example, when forming a protective film by the spin coater method as described above, as a means of shortening the cycle time of the protective film forming apparatus, a method of shortening the time required for curing the uncured resin layer is used. Conceivable.

However, shortening the curing time brings about a risk that the obtained protective film is not sufficiently cured. In particular, the ultraviolet beam is difficult to be focused on the resin that has wrapped around the side surface of the outer peripheral portion of the disc substrate, and therefore the curing time of the resin in this portion is slower than that of the resin on the disc surface. Therefore, there is no choice but to be careful about shortening the curing time.

Therefore, the present invention has been proposed in view of the above situation, and aims to improve the curing performance when forming a protective film, shorten the curing time of the uncured resin layer, and eventually manufacture it. An object of the present invention is to provide a method for manufacturing an optical disc that can reduce the cycle time of the device.

[0010]

The present invention has been proposed to achieve the above object. That is, the method for producing an optical disc of the present invention, when forming a protective film made of an ultraviolet curable resin on a recording film formed on a transparent substrate,
It is characterized in that the uncured resin layer is cured by disposing the transparent substrate in a cup-shaped reflector that collects the light emitted from the ultraviolet irradiation means on the side surface of the outer peripheral portion of the substrate.

In the optical disc manufacturing method of the present invention, at least a recording film is formed on a transparent substrate, and then a protective film made of an ultraviolet curable resin is formed on the recording film.
The recording film is usually formed by a method used in a method for manufacturing an optical disc of this type, and the forming method is not particularly limited. The method of forming the protective film formed on the recording film is not particularly limited, and for example, a spin coater method, a spray coater method, or the like can be applied.

In the present invention, when the protective film is formed,
A cup-shaped reflector that focuses the light emitted from the ultraviolet irradiation means on the outer peripheral side surface of the substrate is used, and the substrate is housed in this cup-shaped reflector to cure the ultraviolet curable resin supplied on the recording film. To do. As a result, the ultraviolet curable resin that has wrapped around the outer peripheral surface of the substrate is sufficiently irradiated with the ultraviolet beam, and the curing time of the uncured resin layer can be shortened.

The ultraviolet irradiation means is a lamp, a reflector,
It consists of a shutter and a cooling mechanism. Although mercury lamps, metal halide lamps, and the like are known as the above-mentioned lamps, a high-pressure mercury lamp having a relatively high ultraviolet output efficiency is suitable for forming a protective film of an optical disk.

The reflector is provided for the purpose of efficiently reflecting the ultraviolet rays emitted from the lamp and condensing the ultraviolet rays on the substrate. For example, a high-purity aluminum mirror or a heat ray transmission cold mirror specification can be mentioned. To be The shape of this reflector may be a hyperbolic shape that creates a parallel beam or an elliptical shape that creates a focused beam.

The shutter is provided to prevent the temperature of the substrate from rising and to prevent uneven curing of the ultraviolet curable resin. By opening and closing the shutter, the ultraviolet light emitted from the lamp is opened. The light intensity of is adjusted. Further, the cooling mechanism has a function of taking measures against heat such as each constituent member of the ultraviolet irradiation means and a transport mechanism for transporting the substrate.

There are two types of cooling mechanisms, an air cooling type and a water cooling type, which may be appropriately selected as necessary.

The cup-shaped reflector is arranged so that the light receiving portion thereof faces the ultraviolet irradiation means. As the cup-shaped reflector, since the disk-shaped substrate is housed therein, a cup-shaped reflector having a rotational symmetry is preferable.

Further, the side surface of the cup-shaped reflector is constructed so that the light emitted from the ultraviolet irradiation means is condensed on the side surface of the outer peripheral portion of the substrate, and has, for example, a sectional shape having a part of an elliptic curve or a parabola. However, it is preferable to make a proper selection in consideration of the light amount distribution of the ultraviolet irradiation means, the type of the reflection plate, the substrate size, the distance between the ultraviolet irradiation means and the substrate, and the like.

In the present invention, a step of forming various functional films other than the recording layer and the protective film may be added if necessary. Examples of the functional film include a reflective film and the like. In this case, the method for forming each functional film is
Any conventionally known method can be used in the method of manufacturing an optical disc of this type.

[0020]

When a protective film made of an ultraviolet curable resin is formed on a recording film formed on a transparent substrate, a cup-shaped reflector is used for concentrating the light emitted from the ultraviolet irradiating means on the outer peripheral side surface of the substrate. By accommodating the transparent substrate in the cup-shaped reflector, the ultraviolet ray is sufficiently irradiated even on the ultraviolet curable resin that has wrapped around the side surface of the outer peripheral portion of the substrate. As a result, the speed required for the ultraviolet curable resin that has wrapped around the side surface of the substrate to fully cure increases, and the curing time of the uncured resin layer is shortened.

[0021]

EXAMPLES Specific examples to which the present invention is applied will be described in detail below with reference to the drawings and experimental results. In this embodiment, a read-only optical disc (so-called mini disc) having an outer diameter of 64 mm is used as a substrate, and a UV-curable resin as a protective film material is applied onto the substrate by a spin coater method, and then a cup-shaped reflector This is an example in which the uncured resin layer is cured by using.

First, the structure of the optical disk manufactured in this embodiment will be described. That is, in this optical disc, as shown in FIG. 1, an aluminum reflective film 2 is provided on a disk-shaped transparent substrate 1 made of polycarbonate resin, and the surface of the aluminum reflective film 2 is further covered to protect it from an ultraviolet curable resin. It has a structure in which the film 3 is formed.

The transparent substrate 1 is formed by injection molding or the like using a polycarbonate resin.
As the substrate material forming the transparent substrate 1, for example, polymethylmethacrylate resin, polyolefin resin, ethylene resin or the like can be used in addition to the above polycarbonate resin.

The aluminum reflection film 2 is formed by sputtering or the like, and functions as a recording film here. In this embodiment, the thickness of the aluminum reflective film 2 is 60
nm. It should be noted that such a recording film is not particularly limited and may be arbitrarily selected according to the application. Specific examples include a perpendicular magnetization film having a magneto-optical characteristic (Kerr effect or Faraday effect), a low melting point metal thin film, a phase change film, a film containing an organic dye, and the like.

Further, the protective film 3 formed on the surface of the aluminum reflective film 2 prevents water and oxygen from entering from the transparent substrate 1, and the aluminum reflective film 2 is removed from the transparent substrate 1. It is provided in order to prevent peeling and cracks, and is made of an acrylic UV curable resin. The thickness of this protective film 3 is about 7 μm.
And

This optical disk was manufactured by the following method. First, sputtering was performed using a sputtering device to form an aluminum film on a polycarbonate substrate formed by injection molding or the like.

Next, 30 mg of a UV-curable resin was applied on the aluminum film using a spin coater, and then the substrate on which the coating film made of the UV-curable resin had been formed was conveyed to the UV-irradiating section to form an uncured resin layer. Curing was performed to form a protective film.

At the time of forming such a protective film, a cup-shaped reflector was provided in the ultraviolet irradiation section. FIG. 2 shows the configuration of the ultraviolet irradiation unit. As shown in FIG. 2, the ultraviolet ray irradiation section includes an ultraviolet ray irradiator 4 for irradiating the substrate 8 on which the coating film made of the ultraviolet curable resin is formed with ultraviolet rays, and an ultraviolet ray radiated from the ultraviolet ray irradiator 4. It is composed of a cup-shaped reflector 9 that reflects the beam and focuses it on the substrate 8.

The ultraviolet irradiator 4 comprises a lamp 5, a reflector 6, a shutter 7 and a cooling mechanism (not shown). As the lamp 5, a straight-tube high-pressure mercury lamp was used because it has a relatively high ultraviolet output efficiency, and its emission length was 250 nm and the lamp input was 120 W / cm.

The reflection plate 6 is provided for efficiently reflecting the ultraviolet rays emitted from the lamp 5 and condensing the ultraviolet rays on the substrate 8. Here, a heat ray transmitting cold mirror is used. The reflector 6 has a hyperbolic shape, and the light reflected by the reflector 6 becomes a parallel beam.

Further, the shutter 7 is arranged to prevent the temperature rise of the substrate 8 and the partial curing of the ultraviolet curable resin, and can be opened and closed by a rotating operation. .

The cup-shaped reflector 9 is arranged below the ultraviolet irradiator 4. The material of the cup-shaped reflector 9 is stainless steel, and the surface is buffed.

This cup-shaped reflector 9 is a rotationally symmetric deep dish type, and as shown in FIG. 3, the substrate 8 is housed therein. The substrate 8 housed in the cup-shaped reflector 9 is arranged on a rotary tray 10 rotatable in a clockwise direction, and its center is fixed by a center stopper 11. The substrate 8 is fixed by the center stopper 11 and then irradiated with ultraviolet rays while being rotated at a rotation speed of 200 rpm.

The distance between the substrate 8 and the lamp 5 was 15 cm.

Here, as shown in FIG. 4, the cup-shaped reflector 9 has a cross-sectional shape whose side surface has a part of an elliptic curve, and the substrate 8 is irradiated with the light emitted from the ultraviolet irradiator 4. The light is focused on the outer peripheral side surface 8a. For this reason, among the ultraviolet beams emitted from the ultraviolet irradiator 4, the ultraviolet beam applied to the light receiving portion of the cup-shaped reflector 9 has a side surface 8 a of the outer peripheral portion of the substrate 8 according to the shape of the cup-shaped reflector 9. Then, the UV curable resin that has been focused on the outer peripheral side surface 8a of the substrate 8 is effectively cured. Therefore, the curing time of the uncured resin layer can be shortened, and by extension, the cycle time of the manufacturing apparatus can be shortened.

Then, in order to investigate the effect of using the cup-shaped reflector, the following experiment was conducted.
That is, a protective film was formed by changing the ultraviolet irradiation time in the ultraviolet irradiation portion of the spin coater as shown in Table 1 below, and the obtained optical discs (Sample Nos. 1 to 4) were obtained.
The pencil hardness of each protective film was evaluated.

The pencil hardness was evaluated for this portion because the curing speed of the ultraviolet curable resin wrapping around the outer peripheral side surface of the substrate was the slowest. For comparison, two types of optical discs (Sample Nos. 5 and 6) having different UV irradiation times produced by the same method as above except that the above cup-shaped reflector was not used were similarly treated as protective films. The pencil hardness was examined.

The results are shown in Table 1 below.

[0039]

[Table 1]

As is clear from Table 1, when the protective film is formed, a cup-shaped reflector for converging the light emitted from the ultraviolet irradiator on the outer peripheral side surface of the substrate is not used. Even when the ultraviolet irradiation time (curing time) was 3 seconds, the pencil hardness was only B.

On the other hand, when the cup-shaped reflector is used as described above, the ultraviolet irradiation time (curing time)
Even after 1.5 to 3 seconds, the pencil hardness was H, and it was confirmed that the obtained protective film was sufficiently cured. Therefore, it was found that the curing time of the uncured resin layer can be significantly shortened by using the cup-shaped reflector as in this example.

[0042]

As is apparent from the above description, in the optical disc manufacturing method of the present invention, when the ultraviolet curable resin as the protective film material is cured, the light emitted from the ultraviolet irradiation means is applied to the substrate. Since the cup-shaped reflector that focuses the light on the side surface of the outer peripheral portion is used, the curing time of the uncured resin layer can be shortened, and thus the cycle time of the manufacturing apparatus can be shortened. Therefore, according to the present invention, it is possible to improve the production efficiency, reduce the price, and increase the profit / share.

Further, according to the present invention, the resin sneaking around the side surface of the outer peripheral portion of the substrate can be reliably cured, so that the corrosion resistance of the recording film is improved and the problems such as peeling of the protective film are reduced. To do. Further, according to the present invention, since the ultraviolet curable resin can be cured with low energy, the temperature rise of the substrate can be suppressed more than before, and the adverse effect on the optical characteristics of the substrate can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of an optical disc manufactured in manufacturing an optical disc to which the present invention is applied.

FIG. 2 is a schematic diagram showing a configuration example of an ultraviolet irradiation unit of a spin coater used in manufacturing an optical disc to which the present invention is applied.

FIG. 3 is an enlarged perspective view of an essential part showing a state where a substrate is housed in a cup-shaped reflector.

FIG. 4 is an enlarged sectional view of an essential part showing a configuration example of a cup-shaped reflector.

[Explanation of symbols]

 1 ... Transparent substrate 2 ... Aluminum reflective film 3 ... Protective film 4 ... UV irradiator 5 ... Lamp 8 ... Substrate 6 ... Reflector 7 ... Shutter 9 ...・ Cup-shaped reflector

Claims (2)

[Claims] 1. A cup-shaped reflector for condensing light emitted from an ultraviolet ray irradiating unit on a side surface of an outer peripheral portion of a substrate when a protective film made of an ultraviolet curable resin is formed on a recording film formed on a transparent substrate. A method for manufacturing an optical disc, comprising: arranging the transparent substrate on a substrate to cure an uncured resin layer. 2. The method of manufacturing an optical disc according to claim 1, wherein the light receiving portion of the cup-shaped reflector has a cross-sectional shape having a part of an elliptic curve or a parabola.