JPH05182251A - Reproduction of optical disk substrate - Google Patents

Abstract

PURPOSE:To enhance safety and to improve mass production efficiency by continuously executing the entire stage consisting of a series of stages or a part thereof in an inert gaseous atmosphere. CONSTITUTION:A photoresist 2 is applied on the surface of a thick glass plate 1 and is irradiated with a laser beam 3 by a desired signal to bring the resist 2 into a photosensitive reaction. The pits and sector marks indicating optical head guide grooves and addresses or the rugged patterns of recording information are formed to constitute a master disk 4. A thin film of nickel is stuck by vapor deposition onto the resist 2 to form a plating layer 5. Further, the plating 5 and the glass plate 1 are peeled and the resist 2 sticking to the peeled surface is removed by oxygen plasma etching, by which a stamper 6 is formed. The optical disk substrate is irradiated again with the peeled photosetting resin. The safety is enhanced and the mass production is enabled if the entire stage of a series of such stages or a part thereof is continuously executed in the inert gaseous atmosphere.

Description

Detailed Description of the Invention

[0001]

The present invention relates to CD, CD-I, DV-
The present invention relates to a method for replicating an optical disc used in an optical disc device such as an I, LD, and CD-ROM, and more particularly to a method for manufacturing a large amount of inexpensive products.

[0002]

2. Description of the Related Art In a conventional optical disk duplication method, an uneven pattern is transferred by nickel plating from a master plate with a photoresist having an optical head guide groove and pits indicating addresses, etc., and an uneven pattern such as sector marks or recorded information. I was making a stamper. further,
An ultraviolet curable resin (UV curable resin) is dropped on the surface of the stamper, and ultraviolet light is irradiated onto a transparent glass plate or a plastic plate laminated to cure the resin, and then the cured resin and the stamper are stacked. When separated (separated) at the boundary surface of, a replica substrate having an uneven pattern on the surface was completed. This method is a so-called 2P method and has a feature that an optical disk can be duplicated with a simple device configuration. A photo-curing resin is used in the method of replicating a replica substrate by transferring a pattern from a stamper having an uneven pattern. Generally, the curing of a resin becomes difficult when the oxygen concentration in the atmosphere during ultraviolet exposure is high, so it is necessary to perform the exposure in an atmosphere with a reduced oxygen concentration.

Therefore, in order to reduce the residual oxygen concentration and perform ultraviolet exposure, exposure in vacuum is performed in a closed container.
In the vacuum exposure method, first, the produced replica substrate is set in a vacuum container. Next, vacuum the container (1.0 to 0.7 T
The resin is irradiated with ultraviolet rays through a transparent glass plate above the exposure container and cured. After that, let air flow into the container with a slow leak to return to atmospheric pressure,
Completed when the replica substrate is taken out. Further, in order to sufficiently cure the UV resin, baking is performed at a temperature suitable for the heat resistance characteristics of the resin to complete one replica.

[0004]

The above-mentioned conventional technique is necessarily a batch processing system because there is a vacuum evacuation process during the replica substrate replication process. In order to improve mass production efficiency, the size of the container may be increased to increase the amount of treatment at one time. That is, when the vacuum container is enlarged to increase the exposure area in order to improve mass production efficiency, it is necessary to enlarge the transparent glass plate. In that case, since the transparent glass plate during the ultraviolet exposure process is constantly subjected to atmospheric pressure, there is a safety problem such that even small scratches are easily broken, and it is difficult to enlarge the transparent glass plate.

An object of the present invention is to provide a method for manufacturing a substrate for optical discs, which is highly safe and has high mass production efficiency, as well as curing a photo-curing resin in an atmosphere with reduced oxygen concentration, instead of exposure in a vacuum atmosphere. Especially.

[0006]

The above object can be achieved by exposing the atmosphere for replicating a substrate having an uneven pattern by transfer to ultraviolet rays in an inert gas atmosphere. Generally, the curing of the photo-curable resin strongly depends on the oxygen concentration during ultraviolet exposure. Therefore, in order to reduce the oxygen concentration in the container, an inert gas such as nitrogen gas is introduced into the container to replace the air to sufficiently reduce the residual oxygen concentration. The step of applying the liquid photo-curable resin to the stamper is performed in the container of the inert gas atmosphere, and further, the ultraviolet exposure is performed in the state where the stamper coated with the liquid photo-curable resin and the transparent substrate are in close contact with each other. Perform in a gas atmosphere container. Further, the re-exposure of the replica substrate peeled off after the ultraviolet exposure is also performed in the container of the inert gas atmosphere. That is, the replica substrate is duplicated in a container in an inert gas atmosphere in which the residual oxygen concentration is reduced. This is a method of continuously processing in the same container from the step of applying a liquid photo-curable resin to the stamper to the step of re-exposing the separated replica substrate.

Ar and N ₂ are preferable as the above-mentioned inert gas. The residual oxygen concentration in the container is 0.001% or more and 5%
The following range is preferable, and a range of 0.01% or more and 2% or less is more preferable. The concentration of the inert gas introduced into the container is preferably 95% or more. Furthermore, the pressure of the inert gas introduced into the container is 0.5 kg / cm ² or more and 5 k.
A range of g / cm ² or less is preferable, and 1 kg / cm ² or more and 3 kg
The range of / cm ² or less is more preferable.

For example, when argon gas is used, the pressure at the time of introduction into the container is more preferably in the range of 1 kg / cm ² or more and 3 kg / cm ² or less, and the residual oxygen concentration is in the range of 0.01% or more and 2% or less. Is more preferable. When obtaining an atmosphere having a residual oxygen concentration of less than 0.001% as described above, the temperature inside the container is raised to facilitate desorption of the adsorbed gas, and an inert gas is introduced when the gas is introduced into the container. The gas pressure must be 5 kg / cm ² or more, which requires a lot of time. Further, when the residual oxygen concentration exceeds 5%, if the components of the photocurable resin slightly change, the curing becomes insufficient and the effect is small. Furthermore, when the concentration of the inert gas introduced into the container is 95% or less, it is difficult to reduce the residual oxygen concentration in the container to 5% or less.

In the heat treatment of the formed replica substrate, it is necessary to consider the glass transition point of the resin used for replication. That is, the resin softens near the glass transition point,
The surface of the resin makes the surface of the resin smooth. Therefore,
After forming the uneven pattern, heat treatment is performed at a temperature close to the glass transition point of the resin. As a result, the fine roughness of the resin surface of the substrate is reduced by the surface shape of the resin being thermally changed. Therefore, the fine roughness (the roughness of the photoresist film surface and the roughness of the nickel plating film surface) of the master transferred to the substrate surface can be smoothed, and the noise can be reduced. These resins include, for example, acrylic UV curable resins. The heat treatment temperature has a lower limit of −50 ° C. or higher and an upper limit of + 100 ° C. or lower with respect to the glass transition point Tg of the resin of the substrate on which the uneven pattern is duplicated.
However, the range below the thermal decomposition temperature is preferable, and the lower limit is -2.
The range of 0 ° C or higher and the upper limit value of + 50 ° C or lower is more preferable. Alternatively, the lower limit value is preferably -25% or more and the upper limit value is + 20% or less, and the lower limit value is -15, with respect to the glass transition point Tg of the resin of the substrate on which the uneven pattern is duplicated.
% Or more, and the upper limit is more preferably + 10% or less.
The effect of the present invention can be obtained even at a heat treatment temperature in a range other than the above.
However, when the temperature is low, the softening of the resin is small and the effect of reducing the fine roughness is small. Further, when the temperature is high (when the temperature is higher than the thermal decomposition temperature), the molecular bond as the resin is partially broken, and the strength is impaired.

[0010]

[Function] When an optical disk substrate having a concavo-convex pattern is duplicated using a photo-curable resin by an ultraviolet exposure method, the atmosphere in the container is made an inert gas atmosphere, and the resin is exposed to ultraviolet light so that the resin is exposed to the same level as in a vacuum atmosphere. Can be cured. That is, an inert gas such as nitrogen gas is flowed into the container to replace the air, and the residual oxygen concentration in the container is set to a sufficiently low concentration that does not hinder the curing of the resin. As a result, the replica substrate is continuously processed in the same container in the inert gas atmosphere from the step of applying the liquid photo-curable resin to the stamper to the step of re-exposing the separated replica substrate. Therefore, it is possible to obtain a method of manufacturing a substrate having an uneven pattern, which has high safety and excellent mass production efficiency.

[0011]

【Example】

<Embodiment 1> A method for producing a substrate by transferring the shape of a concave / convex pattern such as pits, sector marks, or recording information representing an optical head guide groove and address according to the present invention will be described. First, the manufacturing process of the master and stamper is shown in FIG. Photoresist 2 is applied to the surface of a thick glass plate (thickness 10 mm) 1, and a laser beam 3 is applied to this to irradiate the photoresist with a desired signal so that the photosensitivity reaction of the photoresist occurs, and an optical head guide groove and a pit representing an address or the like. Or sector
An uneven pattern such as marks or recorded information is formed to form the master 4. Next, a nickel thin film was deposited on this photoresist by vapor deposition, and a nickel plating layer 5 (0.3 nm) was formed using this as an electrode. Next, plating layer 5
And the lath plate 1 were peeled off, and the photoresist 2 adhering to the peeled surface was removed by oxygen plasma etching to produce a stamper 6.

Next, FIG. 2 shows a replica manufacturing process. The surface of the stamper 6 on which the concavo-convex pattern was duplicated and the entire surface of the transparent glass plate 7 for a substrate were brought into close contact with each other through an acrylic photo-curable resin 8 and exposed to ultraviolet light 9 to cure the resin. Then, it was separated (peeled) from the interface between the resin 8 and the stamper 6, and a replica substrate 10 for an optical disk having a photocurable resin in which a guide groove and a prepit pattern were duplicated was produced on the surface. Here, in this exposure, the substrate needs to be transparent in order to allow the ultraviolet light to reach the resin and cure the resin. Then, the replica substrate 10 separated (separated) from the interface of the stamper 6 was set in a container of an inert gas (for example, nitrogen gas) atmosphere 11 and re-exposed with ultraviolet light in a low oxygen concentration atmosphere. At this time, the atmosphere is nitrogen gas with a concentration of 95% or more and the pressure is 2 k.
It was introduced under the condition of g / cm ² , and the residual oxygen concentration was 0.
It is 1% or less. Thereafter, heat treatment was carried out at 200 ° C. for 1 hour in order to promote the evaporation removal of the uncured portion and the curing reaction, and further to smooth fine irregularities on the surface. The conditions at this time are determined by the glass transition point of the resin used. With respect to the glass transition point Tg, the lower limit value is −50 ° C. or higher, the upper limit value is + 100 ° C. or lower, or the lower limit value is −25% or higher,
The upper limit value is a temperature within a range of + 20% or less. However, the temperature is in the range below the thermal decomposition temperature.

<Embodiment 2> The same applies when a transparent plastic stamper using a photocurable resin is used instead of the nickel stamper as the stamper, and will be described in detail below.
The manufacturing process of the plastic stamper is shown in FIG. Master 4
In order to prevent the change of shape due to swelling or alteration and to ensure the peeling, a metal film of Al-Ti (about 50 n
m) 12 is formed by a sputtering method. Next,
Liquid acrylic photo-curable resin 8 is dropped on the master surface,
Overlapping transparent plastic plate 13 and exposing it to ultraviolet rays 9,
Let it harden. After that, the Al—Ti metal film 12 and the photocurable resin 8 are separated from the boundary, and the pattern of the master 4 is transferred to the transparent plastic plate 13 to manufacture the stamper 14. Further, the stamper 14 is exposed again in a nitrogen gas atmosphere having a low oxygen concentration in 11 and then heat-treated to complete the process. The heat treatment has the effect of increasing the mechanical strength in the subsequent replica production. The nitrogen gas atmosphere exposure and heat treatment conditions are the same as those for the replica substrate described above.

Next, a replica was produced using this plastic stamper. The surface of the plastic stamper 14 and the transparent glass plate 7 for the substrate are covered with an acrylic photocurable resin 8
The entire surface was brought into close contact with the resin via an ultraviolet ray and exposed to ultraviolet light 9 to cure the resin. Then, it was separated (peeled) from the interface between the resin 8 and the stamper 15, and a replica substrate 10 for an optical disk having a photocurable resin in which a guide groove and a prepit pattern were duplicated was produced on the surface. Here, at the time of exposure, at least one of the stamper and the substrate needs to be transparent in order to allow the ultraviolet light to reach the resin and cure the resin. Then, after the replica substrate separated (peeled) from the interface of the stamper is set in a container of an inert gas (for example, nitrogen gas) atmosphere 11, the ultraviolet light 9 is re-exposed in a low oxygen concentration atmosphere, Heat treatment was performed. The nitrogen gas atmosphere exposure and heat treatment conditions are the same as those for the replica substrate described above.

A part or all of the Al--Ti alloy film for surely separating from the stamper of the master is Au, Ag,
Cu, Pt, Rh, Ta, Cr, Ni, Mn, Nb, Z
The same effect can be obtained by substituting at least one selected from r and Si. Further, if necessary, a release agent (eg, silicone oil, chalcogen compound, ie, Te, S
A mixture or compound containing at least one of e and S) may be coated by a method such as vapor deposition to obtain the same effect.

<Third Embodiment> In the first and second embodiments, it is possible to continuously perform a series of steps in an atmosphere of an inert gas. The continuous production process is shown in FIG. That is, the step of dropping a liquid photo-curable resin on the surface of the stamper or the transparent substrate, the step of adhering the transparent substrate to the surface of the stamper via the photo-curable resin, and the step of applying ultraviolet light to the photo-curable resin through the transparent substrate. A series of the steps of irradiating, peeling from the interface between the stamper and the photo-curing resin, peeling from the interface between the stamper and the photo-curing resin, and irradiating the optical disc substrate having the peeled photo-curing resin again with ultraviolet rays. That is, the steps are continuously performed in an atmosphere of an inert gas.
The nitrogen gas atmosphere exposure conditions are the same as those described above.

Next, FIG. 5 shows a magneto-optical disk structure in which recording films, protective films, etc. which constitute an optical disk are laminated using the replica substrates of Examples 1, 2, and 3. After a SiN film having a thickness of 85 nm is laminated on the surface of the heat-treated substrate as a lower protective layer 17, a TbFeCo film is formed as a layer 18 for recording information.
It was laminated with a thickness of 00 nm. Further, SiN is used as the upper protective layer 19.
A film having a thickness of 85 nm is stacked and used as a reflection layer and a heat diffusion layer 20.
A 50 nm thick TiTi alloy film was laminated. Using this disc, the recording / reproducing characteristics were evaluated. As a result, the carrier-to-noise ratio C / N was 55 dB.

According to the present invention, it is possible to manufacture an optical disk substrate that is sufficiently safe and has high mass production efficiency while sufficiently curing an anaerobic photocurable resin.

[0019]

According to the present invention, by producing a replica substrate for an optical disc in a low oxygen concentration atmosphere, the photo-curing resin is sufficiently cured, and the safety of work is high and the mass production efficiency is high. A substrate can be produced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a basic master disc manufacturing process of the present invention.

FIG. 2 is a cross-sectional view showing a step of producing a replica substrate using a stamper.

FIG. 3 is a cross-sectional view showing a process of making a plastic stamper.

FIG. 4 is a cross-sectional view showing a step of continuously producing replica substrates.

FIG. 5 is a cross-sectional view showing a magneto-optical disk structure.

[Explanation of symbols]

4 ... Master, 8 ... Photocurable resin, 9 ... Ultraviolet light, 11 ... Inert gas atmosphere, 13 ... Plastic plate, 14 ... Plastic stamper.

Continuation of the front page (72) Inventor Shinkichi Horigo 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (5)

[Claims] 1. A step of dropping a liquid photo-curing resin onto a stamper surface or a transparent substrate surface having an optical head guide groove and an uneven pattern of pits or sector marks indicating addresses and the like or recording information on the surface, and the above-mentioned light. A step of adhering a transparent substrate to the surface of the stamper via a curable resin, a step of irradiating the photocurable resin with ultraviolet rays through the transparent substrate, a step of peeling from the interface between the stamper and the photocurable resin, An optical disk substrate, characterized in that all or a part of the step of irradiating the optical disk substrate having the above-mentioned peeled photocurable resin with ultraviolet rays is continuously or partially processed in an atmosphere of an inert gas. How to duplicate. 2. The method of replicating an optical disk substrate according to claim 1, wherein the residual oxygen concentration in the inert gas atmosphere is in the range of 0.001% or more and 5% or less. 3. The method for duplicating an optical disk substrate according to claim 1, wherein the concentration of the inert gas flowing into the inert gas atmosphere is 95% or more. 4. The pressure of the inert gas flowing into the inert gas atmosphere according to claim 1, 2 or 3, is 0.5 k.
A method of replicating an optical disk substrate in the range of g / cm ² or more and 5 kg / cm ² or less. 5. The method of replicating an optical disk substrate according to claim 1, 2, 3 or 4, wherein the gas in the inert gas atmosphere is Ar or N ₂ .