JP2009020931A - Transparent stamper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stamper base material of a transparent stamper which reduces irradiation time for exposure for forming an irregular pattern in a heat type resist in the transparent stamper used for manufacturing a multilayer recording medium that can be used for a plurality of times. <P>SOLUTION: The transparent stamper forms an inorganic resist in which the transparent irregular pattern is formed on a transparent substrate, and is used for a multilayer optical recording medium. In the transparent stamper, fluororesin, a COP resin, and soda lime glass are used as materials for the substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transparent stamper used for manufacturing an optical recording medium.

  Compact discs (hereinafter abbreviated as CDs) developed as optical recording media for recording audio signals as digital signals are also used as recording media for digital signals other than audio signals. As a medium for recording a digital signal, an improvement in recording density is required in response to a demand for backup of a personal computer, image recording, and the like, and a digital versatile disc (hereinafter abbreviated as DVD) has been developed.

  However, a larger recording capacity is required as a recording medium for high-quality content such as terrestrial digital broadcasting.

  In general optical recording media, a signal pattern is recorded on a recording film formed on a substrate by light energy or magnetic energy. In order to further increase the capacity, there is a multilayer optical recording medium having two or more recording films.

  The increase in the track recording density of an optical disc depends greatly on the laser wavelength λ of the optical system for recording / reproduction and the numerical aperture NA of the objective lens, and the spatial frequency at the time of signal reproduction can be detected at about NA / λ. It is a limit. Therefore, in order to realize high density with the conventional optical disc, it is possible to further increase the track recording density by shortening the laser wavelength λ of the reproducing optical system and increasing the numerical aperture NA of the objective lens.

  However, by increasing the aperture ratio, it is possible to reduce the beam spot to the wavelength limit, but the higher the aperture ratio, the shorter the focal length. For this reason, it is necessary to thin the substrate on the light incident side.

  There is a blu-ray disc (registered trademark: hereinafter abbreviated as BD) as an optical recording medium in which the wavelength of the laser is shortened and the aperture ratio is increased. In order to further increase the recording capacity of the BD, it has been proposed to increase the recording layer (Patent Documents 1 and 2).

Hereinafter, a method for producing a multilayer optical recording medium using a photopolymer method (hereinafter abbreviated as 2P method) disclosed in Patent Document 1 will be described with reference to the schematic process cross-sectional view of FIG.
(1) The signal pattern formed on the stamper 14 by the injection molding method is transferred onto the substrate 1.
(2) The first recording film 4 is formed on the signal pattern.
(3) Similar to the substrate 1, the transparent stamper 2 is manufactured by injection molding. A second-layer signal pattern is formed on the transparent stamper 2 in the same manner as the substrate 1. A 2P resin 3 made of an ultraviolet curable resin is formed on the substrate 1 by using a coating method, and a transparent stamper 2 is laminated on the 2P resin 3 and cured with ultraviolet rays, whereby a second layer signal is formed on the 2P resin 3. The pattern is transferred.
(4) The intermediate layer 6 is formed by peeling the transparent stamper 2.
(5) A second recording film 5 is further formed on the second signal pattern.
(6) Thereafter, the organic protective film 7 is formed to form a two-layer optical recording medium.

  Multi-layer media having two or more layers can also be created by this method. That is, after the recording film 5 is formed, a further multilayer optical recording medium is manufactured by repeating the process of forming the intermediate layer by the 2P method in the same manner as described above, using the transparent stamper corresponding to the upper signal pattern. Is possible.

  The transparent stamper 2 called in the process described above is a transparent resin substrate made from a precision mold by an injection molding method like the stamper 14, and the signal pattern transferred thereto is further passed through the ultraviolet curable resin 3. The signal pattern surface is transferred onto the recording film 4.

  However, in this method, when polycarbonate (PC) resin is used as the material of the transparent stamper 2, the transparent stamper 2 is used once because the transparent stamper 2 deteriorates due to UV light when the 2P resin is cured with ultraviolet rays. It is made disposable.

  For this reason, since the transparent stamper is made disposable after a single use, it has a problem of increasing industrial waste.

  On the other hand, in the case of BD, because the size of the signal pattern is small, it is applied to use a heat resist (hereinafter abbreviated as “inorganic resist”) made of an inorganic material instead of the conventional photoresist for the formation of the signal pattern. The person proposed in Japanese Patent Application No. 2006-020895.

A method for manufacturing a transparent stamper using an inorganic resist presented in Japanese Patent Application No. 2006-020895 will be described with reference to schematic process cross-sectional views in FIG.
(1) A stamper base material 13 is prepared. The stamper base material 13 is more preferably cleaned, and any method such as a wet method, a dipping method, or a dry method may be used as long as dust on the surface of the stamper base material 13 is removed.
(2) Thereafter, an inorganic resist film 8 is formed on the stamper base 13 by using a sputtering method.
(3) A predetermined uneven pattern is exposed by the light beam 9. For the exposure, an exposure apparatus having a movable optical stage in which the stamper base 13 is rotated at a constant angular velocity or a constant linear velocity by a turntable and slides at a constant speed can be used.
(4) The exposed portion 10 or the unexposed portion 11 is selectively etched to form a concavo-convex pattern on the stamper base material 13. As a material used at this time, it is possible to select an optimum material for an inorganic resist such as an alkaline solution or an acid solution, pure water, or an organic solvent, and there is no particular limitation. In some cases, it is also possible to form a concavo-convex pattern by a dry etching method, and as the etchant gas to be used, a material capable of obtaining a required selection ratio in the exposed portion 10 or the unexposed portion 11 of the inorganic resist 8 material may be selected. .
JP 2003-203402 A JP 2002-260307 A

By forming a heat-type resist that transmits ultraviolet light on a transparent substrate such as quartz glass (hereinafter sometimes referred to as SiO ₂ ), a transparent stamper that does not have to be disposable can be obtained. However, when the heat resist on the quartz glass (SiO ₂ ) is exposed with the energy of the laser when exposing the heat resist on the PC resin, it is necessary to reduce the linear velocity. When the linear velocity is slowed down, the time for exposing one substrate becomes longer, which causes a problem that the throughput of the exposure apparatus decreases.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a stamper for a transparent stamper that can shorten the irradiation time for forming a concavo-convex pattern on a heat resist in a transparent stamper used for manufacturing a multilayer recording medium that can be used a plurality of times. A substrate is provided.

The present invention is a transparent stamper used for a multilayer optical recording medium, in which an inorganic resist having a light-transmitting uneven pattern formed on a light-transmitting substrate is formed.
The transparent stamper is characterized in that the material used for the substrate is fluorine resin, COP resin, or soda lime glass.

  By using the substrate material of the present invention, it is possible to obtain a transparent stamper that can be used multiple times without reducing the throughput of the exposure apparatus.

  As a result of investigation, the present inventor has derived that the difference in the exposure conditions of the inorganic resist is due to the thermal conductivity of the substrate.

  When the thermal conductivity is high, the required uneven pattern shape cannot be obtained even if exposure is performed with the same power. This is presumably because the amount of heat necessary for the crystalline / amorphous phase change of the inorganic resist is absorbed or diffused by the material of the substrate. For this reason, it is considered that before the phase change occurs, heat escapes to the base material, and the necessary heat does not remain on the inorganic resist.

  In order to improve this, it is necessary to have a stronger exposure energy in the stamper substrate and on the inorganic resist film. This emits stronger power from the light source of the exposure apparatus, which increases the burden on the laser light source and the burden on the optical components that it makes, and at the same time, in some cases the light source itself must be replaced. . This imposes unnecessary capital investment in order to use the inorganic resist, resulting in an increase in production cost. Moreover, as a method of increasing the power of the exposure light source, the power on the inorganic resist film can be improved by reducing the linear velocity, which is one of the exposure conditions, but this will reduce the throughput of the exposure apparatus and is practical. is not.

Although the manufacturing method of the transparent stamper has been described using the schematic process cross-sectional view of FIG.
1. Regarding the thickness, it is necessary for the transparent stamper to be able to maintain rigidity, and it should be 0.3 mm or more, and more preferably 0.6 mm or more from the viewpoint of handling during production.
2. The shape of the stamper base material 13 is not particularly limited, but is desirably a circular shape or a substrate shape. In the case of a general substrate shape, the outer diameter is φ120 mm, and the inner diameter has a central hole with φ15.0 mm.

  Concentric circles or spiral concavo-convex patterns are formed by the exposure process, but the center hole or the eccentric position accuracy between the outer shape and the concavo-convex pattern is higher during exposure, so the inner / outer diameter tolerance and the chamfered portion machining accuracy are constant Something is preferable.

  Since the intermediate layer is cured by irradiating ultraviolet rays (hereinafter abbreviated as UV light) through a transparent stamper, if the substrate has low ultraviolet transmittance, the curing time becomes longer and the throughput is lowered. It is preferable that it can permeate.

  Further, the reason why the substrate made of PC resin is deteriorated by UV light is considered to be that the deterioration proceeds because the PC resin absorbs UV light. For this reason, when using organic resin, such as PC resin, as a board | substrate, it is preferable that the transmittance | permeability with respect to UV light is high.

  For this reason, it is more preferable that the transmittance of the stamper substrate in UV light is 94% or more.

  Materials satisfying these conditions include coolefin polymer resins (hereinafter sometimes abbreviated as COP resins), resin materials such as fluorine resins, or quartz glass.

  The material used as the inorganic resist is preferably a material that exhibits a crystalline / amorphous phase change by heat. For example, an alloy made of at least one kind of materials such as Te, In, Ga, Sb, Se, Pb, Ag, Au, As, Co, Ni, Mo, W, Pd, Ti, Bi, Zn, and Si, or Oxides, nitrides, etc. are widely known. Many materials already exist as well-known techniques. However, since a concavo-convex pattern is formed as a subsequent process, a material having a light-transmitting property that allows a large selection ratio between an exposed part and an unexposed part and transmits ultraviolet rays is preferable. In particular, an incomplete oxide of tungsten oxide is preferable. As a resist formation method, a vapor deposition method, a CVD method, or the like can be selected in addition to the sputtering method, and is not particularly specified.

(Example)
Using the transparent stamper 2, the signal pattern was transferred to the ultraviolet curable resin.

  The transparent stamper 2 was manufactured using the manufacturing method of FIG. The stamper base material 13 preferably has a thickness of 1.0 mm to 20 mm, a diameter of 80 to 120 mm, and a center hole diameter of 10 to 15 mm. The thickness of the resist is preferably 20 nm to 1000 nm.

As a material of the stamper substrate are shown in Table 1, the single-crystal silicon (Si), nickel (Ni), soda lime glass, quartz glass (SiO _2), PC resin, PMMA resin, COP resin, and fluorine-based The resin was used. In this embodiment, the substrate has a thickness of 5 mm, a diameter of 120 mm, and a center hole diameter of 12 mm. As the inorganic resist, an incomplete oxide of tungsten oxide having a thickness of 300 nm and formed by sputtering is used. Table 1 shows the thermal conductivity (W / m · K (300 ° K)) and transmittance of each material.

  As the exposure apparatus, an apparatus capable of laser exposure at a constant linear velocity was used, and a signal pattern composed of lands and grooves was exposed.

  For development, a solution of tetramethylammonium hydroxide (TMAH): 2.38% was immersed in a solution diluted 5 times with pure water for 3 minutes. Thereby, a concavo-convex pattern having a groove depth of 25 nm was formed.

Under the development conditions described above, the exposure conditions for each material with a groove depth of 25 nm are as follows:
Single crystal silicon: No conditions Nickel:
Quartz glass: 1400 μW 0.5 m / sec, 2400 μW 1.0 m / sec,
Soda lime glass: 2300 μW 2.0 m / sec,
PC resin: 1600 μW 1.0 m / sec, 2000 μW 2.0 m / sec, 2300 μW 2.5 m / sec, 2700 μW 3.0 m / sec,
PMMA resin: 1600 μW 1.0 m / sec, 2000 μW 2.0 m / sec, 2300 μW 2.5 m / sec, 2700 μW 3.0 m / sec,
COP resin: 1600 μW 1.0 m / sec, 2000 μW 2.0 m / sec, 2300 μW 2.5 m / sec, 2700 μW 3.0 m / sec,
Fluorine-based resin (product name Aflex (Asahi Glass Co., Ltd.)): 1600 μW 1.0 m / sec, 2000 μW 2.0 m / sec, 2300 μW 2.5 m / sec, 2700 μW 3.0 m / sec.

  In the transparent stamper 2 using quartz glass (SiO 2) as the stamper base material 13, signal pattern transfer was performed 10 times, but a signal could be obtained without any problem on any substrate. (Deleted because quartz glass is okay.) The stamper base material 13 uses a fluororesin: a sheet base material of the product name Aflex (Asahi Glass Co., Ltd.), and the transparent stamper 2 performs signal pattern transfer a plurality of times. The signal could be obtained without any problem even on the substrate. Moreover, the transparent stamper could be used without breakage.

  Table 2 shows a list of development conditions.

  When silicon was used as the material, the exposure conditions could not be found in the exposure apparatus used in this experiment.

  From Table 3, when the thermal conductivity is high, the required uneven pattern shape cannot be obtained even if exposure is performed with the same power. This is presumably because the amount of heat necessary for the crystalline / amorphous phase change of the inorganic resist is absorbed or diffused by the material of the substrate. Therefore, it is considered that before the phase change occurs, the heat escapes to the base material and the necessary heat does not remain on the inorganic resist.

  In addition, in the study by the present inventors, when a material having high thermal conductivity such as Si or Ni is used for the stamper base material as compared with the transparent base material, the heat transfer to the substrate side is more remarkable. The results are known. On the other hand, when an inorganic resist is formed on a resin material having low thermal conductivity, it was possible to carry out with a lower exposure. Further, in order to provide a function as a transparent stamper, the curing time and the ultraviolet irradiation power can be suppressed as the UV transmittance is higher. Specifically, it is preferable that the transmittance of the stamper base material of the transparent stamper with respect to ultraviolet light is 90% or more. Among these conditions, materials that satisfy both of these conditions include soda lime glass, COP resin, and fluororesin material, but are not particularly limited as long as they satisfy the above conditions.

Example of schematic diagram of manufacturing method of stamper in the present invention Example of schematic diagram of manufacturing method of multilayer optical recording medium in conventional method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Transparent stamper 3 2P resin 4 Recording film 5 Recording film 6 Intermediate layer 7 Organic protective film 8 Inorganic resist 9 Laser light 10 Exposed back part 11 Unexposed part 13 Stamper base material 14 Stamper

Claims (2)

A transparent stamper used in a multilayer optical recording medium, wherein an inorganic resist having a light-transmitting uneven pattern formed on a light-transmitting substrate is formed,
A transparent stamper, wherein a material used for the substrate is a fluorine-based resin, a COP resin, or soda lime glass.   The transparent stamper according to claim 1, wherein the inorganic resist is an incomplete oxide of tungsten.

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