JP2010080033A - Optical disk and method for manufacturing optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent warpage and distortion of a light transmissible resin sheet (a second substrate) by forming a rugged-shaped pit or groove pattern on both surfaces of the light transmissible resin sheet (the second substrate). <P>SOLUTION: There is provided an optical disk 10A including: a first substrate 16; and the second substrate which is stuck to the first substrate 16, and has a dummy pattern surface having a rugged shaped dummy pattern 11a on one surface thereof and a signal surface having a rugged shaped signal pattern 11b based on a prescribed optical disk specification on the other surface thereof opposite to the one surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical disk in which one surface is a signal surface {for example, a signal surface having a concavo-convex pattern conforming to the BD (Blu-ray Disc) standard) and another substrate and an optical disk manufacturing method. It is.

  In general, an optical disc records information signals such as video data, audio data, or computer data with high density on a signal surface having tracks formed in a spiral or concentric pattern on a disc substrate, and has been recorded. This is often used because a desired track can be accessed at a high speed when the information signal is reproduced.

  As this type of optical disc, CD (Compact Disc), DVD (Digital Versatile Disc) and the like are already on the market, and recently, a Blu-ray Disc (hereinafter referred to as a high-density optical disc) which is a type of ultra-high density optical disc with higher density. BD) is in circulation.

  As the recording capacity of the optical disc increases, the NA of the objective lens is increased to reduce the spot diameter of the laser beam emitted from the objective lens in the optical pickup. Accordingly, it is necessary to reduce the thickness of the substrate from the laser beam incident surface to the signal surface.

  By reducing the thickness of the substrate from the laser beam incident surface to the signal surface, the tilt angle at which the optical axis of the objective lens deviates from the angle perpendicular to the signal surface of the optical disk causes aberrations and birefringence due to the substrate thickness. To avoid being affected.

  More specifically, the above-described BD (Blu-ray Disc) is a laser beam obtained by narrowing a laser beam having a wavelength of about 405 nm with an objective lens having a numerical aperture (NA) of about 0.8 to 0.85. By irradiating the laser beam incident surface side, an information signal is recorded on a signal surface located at a predetermined distance from the laser beam incident surface, and a recorded information signal is reproduced. The recording capacity of the signal surface of the BD is about 5 times higher than that of DVD, and about 25 GB (gigabyte) on one side when the diameter of the disk substrate is 12 cm.

  The BD has one signal surface (single layer) and two or more signal surfaces. In the case of a BD having one signal surface, the position is approximately 0.1 mm away from the laser beam incident surface. The signal surface of the BD-LO layer is formed.

  In the case of a BD having two signal surfaces, a BD-L1 layer signal surface is formed at a position approximately 0.075 mm away from the laser beam incident surface, and 0.025 mm from the BD-L1 layer signal surface. A BD-L0 layer signal surface is formed at a separated position.

  The BD uses a light-transmitting resin sheet (transparent film) that is a thin substrate between the laser beam incident surface and the signal surface. As described above, the signal surface is In the case of one layer, the thickness of the light transmissive resin sheet is approximately 0.1 mm, and in the case of two signal surfaces, the thickness of the light transmissive resin sheet is approximately 0.075 mm. An optical disk using this light-transmitting resin sheet (transparent film) is disclosed in Patent Document 1, for example.

FIGS. 10A to 10C are longitudinal sectional views respectively showing conventional examples of an optical disk using a transparent film.
FIG. 11 is a longitudinal sectional view schematically showing a state in which the transparent film is warped when a signal surface is formed on the transparent film in the conventional example.

  The conventional example shown in FIGS. 10A to 10C is disclosed in the following Patent Document 1, and will be described briefly with reference to Patent Document 1.

  First, in the optical disc 100A of the conventional example shown in FIG. 10A, an uneven signal surface 101a is formed on one surface of the disc substrate 101, and both surfaces are formed on the signal surface 101a via an adhesive layer 102. A flat transparent film (light-transmitting resin sheet) 103 is adhered. If one surface side of the transparent film 103 is the laser beam incident surface 103a side, the conventional optical disc 100A can cope with the case where the signal surface is a single layer in the BD described above.

  Next, in the optical disc 100B of the conventional example shown in FIG. 10B, a flat laser beam incident surface 103a is formed on one surface of the transparent film 103, and the other surface opposite to the one surface. An uneven signal surface 103b is formed on the surface. A transparent film 103 having a signal surface 103b is bonded to the disk substrate 101 via an adhesive layer 102, and the conventional optical disk 100B can also handle the case where the signal surface is a single layer in the BD described above.

  Next, in the conventional optical disc 100 </ b> C shown in FIG. 10C, an uneven signal surface 101 a is formed on one surface of the disc substrate 101. Further, one surface of the transparent film 103 is a flat laser beam incident surface 103a, and an uneven signal surface 103b is formed on the other surface opposite to the one surface. A transparent film 103 having a signal surface 103b is adhered to the signal surface 101a of the disk substrate 101 via an adhesive layer 102, and the conventional optical disc 100C can cope with the case where the signal surface is two layers in the BD described above. It is.

Therefore, in the conventional optical discs 100A to 100C shown in FIGS. 10A to 10C, the transparent film 103, which is a thin substrate, is used on the incident surface side of the laser beam, so that the information signal has a very high density. It enables recording and ultra-high density reproduction of recorded information signals.
Japanese Patent Laid-Open No. 11-273147

  By the way, in the above-described conventional optical discs 100A to 100C, in the conventional optical disc 100A shown in FIG. 10A, the concave and convex signal surface 101a is formed on the disc substrate 101, and the transparent film 103 having a small thickness is formed. Since both sides are formed flat, the warp of the transparent film 103 does not occur.

  On the other hand, in the conventional optical discs 100B and 100C shown in FIGS. 10B and 10C, one surface of the thin transparent film 103 is a flat laser beam incident surface 103a, and one surface and Since an uneven signal surface 103b is formed on the other surface on the opposite side, when this transparent film 103 is manufactured, stress distortion occurs during cooling due to the difference in the shape of both surfaces 103a and 103b. Therefore, as shown in FIG. 11, there is a case where warpage or distortion occurs such that the laser beam incident surface 103a side with a small surface area becomes concave and the signal surface 103b side with a large surface area becomes convex.

  In addition, when forming the signal surface 103b on the transparent film 103, the above-described Patent Document 1 uses the well-known 2P method, although the illustration here is omitted, and the inverted concavo-convex pattern on the signal recording surface is formed. An ultraviolet curable resin is applied onto the stamper, and the concavo-convex pattern is transferred to the transparent film 103 while placing the transparent film 103 on the ultraviolet curable resin and pressing with a roller. The transparent film 103 may be warped or distorted due to a difference in shape between the flat laser beam incident surface 103a which is one surface of the film 103 and the uneven signal surface 103b which is the other surface.

  Also in the optical disc 100A described above, the signal surface 101a is formed only on one surface side of the disc substrate 101 thicker than the transparent film 103, so that the signal surface is formed only on one surface side of the transparent film 103. Although the degree is smaller than that, the disk substrate 101 may be warped or distorted.

  Therefore, for example, a substrate (for example, a light-transmitting resin sheet) that is an uneven signal surface conforming to the BD (Blu-ray Disc) standard and the other substrate are bonded to each other, An object of the present invention is to provide an optical disc and a method of manufacturing the optical disc that reduce warpage and distortion of the substrate and the bonded substrate.

The present invention has been made in view of the above problems, and the first invention includes a first substrate,
A dummy pattern surface bonded to the first substrate and having one surface having an uneven dummy pattern, and the other surface opposite to the one surface is an uneven signal conforming to a predetermined optical disc standard. A second substrate which is a signal surface having a pattern;
An optical disc comprising:

The second invention is the optical disc of the first invention described above,
In the optical disk, the second substrate has the same total surface area of the signal surface including the surface area of the signal pattern and the entire surface area of the dummy pattern surface including the surface area of the dummy pattern. It is.

The third invention is the optical disc of the first invention described above,
In the second substrate, the total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern have different values from each other, and The ratio of the total surface area of the dummy pattern surface to the total surface area is set according to the amount of warpage or distortion of the first substrate before bonding.

According to a fourth aspect of the present invention, there is provided a first step for producing a first substrate;
A concave / convex dummy pattern is formed on one surface of a second substrate different from the first substrate so that the one surface is a dummy pattern surface, which is opposite to the one surface of the second substrate. A second step of forming a concave-convex signal pattern conforming to a predetermined optical disc standard on the other surface of the second surface and using the other surface as a signal surface;
A third step of bonding the first substrate and the second substrate after the first and second steps;
It is a manufacturing method of the optical disk characterized by having.

The fifth invention is a method of manufacturing an optical disk according to the fourth invention described above,
In the second step,
In the optical disc manufacturing method, the total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern are set to the same value.

The sixth invention is a method of manufacturing the optical disk of the fourth invention described above,
In the second step,
The total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern are different from each other, and the dummy pattern surface with respect to the total surface area of the signal surface The method of manufacturing an optical disc, wherein the ratio of the total surface area is set according to a warpage amount or a distortion amount of the first substrate before bonding.

  According to the optical disk and the method for manufacturing an optical disk according to the present invention, when the first substrate and the second substrate are bonded together, in particular, the second substrate is a dummy having a concave-convex dummy pattern on one surface. This is a pattern surface, and the other surface opposite to the one surface is a signal surface having a concavo-convex signal pattern conforming to a predetermined optical disc standard, which causes warpage and distortion in the second substrate. Therefore, an optical disk in which the first substrate and the second substrate are bonded can be manufactured with high productivity.

  At this time, one surface of the second substrate is flat because the total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern have the same value. Since there is no difference in the shape of both surfaces of the second substrate compared to the conventional transparent film formed with the concave and convex signal surface on the other surface, the warp and distortion generated in the second substrate can be reduced. Can be suppressed.

  In the second substrate, the total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern have different values, and the total surface area of the signal surface is Since the ratio of the total surface area of the dummy pattern surface is set according to the warpage amount or distortion amount of the first substrate before bonding, one surface is formed flat and the other surface is uneven. Since there is no difference in the shape of both surfaces of the second substrate compared to the conventional transparent film on which the signal surface is formed, it is possible to suppress warpage and distortion generated in the second substrate and to reduce the first substrate. By setting the ratio of the total surface area on the dummy side to the total surface area on the signal side according to the warp amount and distortion amount of the substrate, it is possible to completely cancel the warpage and distortion of the bonded substrate after bonding.

  Hereinafter, an optical disc and a method for manufacturing the optical disc according to the present invention and an embodiment will be described in detail in the order of Embodiment 1 and Embodiment 2 with reference to FIGS.

FIG. 1 is a longitudinal sectional view showing an optical disk of Example 1 according to the present invention.
FIG. 2 illustrates the total surface area of each surface including the surface area of the uneven pit or groove pattern formed on one surface and the other surface of the light-transmitting resin sheet in the optical disk of Example 1 according to the present invention. It is the longitudinal cross-sectional view typically shown in order to do.
FIG. 3 is a diagram schematically showing a process for producing a light-transmitting resin sheet in the optical disc of Example 1 according to the present invention.
FIG. 4 is a diagram schematically showing the method for manufacturing the optical disc of the first embodiment according to the present invention.

  As shown in FIG. 1, an optical disc 10A according to a first embodiment of the present invention includes a light-transmitting resin sheet (second substrate) 11 which is a thin substrate formed using, for example, transparent polycarbonate, For example, it includes a bonded substrate obtained by bonding a disk substrate (first substrate) 16 formed using a transparent polycarbonate to be thicker than the light-transmitting resin sheet 11 using an adhesive.

  Further, the optical disc 10A has, for example, two signal surfaces conforming to an ultra-high density BD (Blu-ray Disc) standard, and a laser beam having a wavelength of around 405 nm has a numerical aperture (NA) of 0.8 to 0.8. By irradiating the laser beam L obtained by focusing with an objective lens (not shown) of about 0.85 from the light-transmitting resin sheet 11 side toward the disk substrate 16 side, the two-layer signal surface is irradiated. It is configured to be recordable or reproducible.

  The two-layer signal surface in the optical disk 10A of Example 1 was separated from the laser beam incident surface by approximately 0.075 mm when one surface (11a) of the light transmissive resin sheet 11 was the laser beam incident surface. A BD-L1 layer signal surface 12a is formed at the position, and a BD-L0 layer signal surface 15a is formed at a position spaced 0.025 mm from the BD-L1 layer signal surface 12a.

  Further, the BD-L1 layer signal surface 12a is formed on the other surface (11b) side opposite to the one surface (11a) of the light transmissive resin sheet 11, and the BD-L0 layer signal surface 15a is light. It is formed on one surface (16 a) of the disk substrate 16 via the transmission layer 14.

  Note that the BD-L1 layer signal surface 12a and the BD-L0 layer signal surface 15a when the optical disc 10A of the first embodiment is configured as a reproduction-only type are for reproduction on a pit pan in which uneven pits are spirally formed. On the other hand, the BD-L1 layer signal surface 12a and the BD-L0 layer signal surface 15a in the case where the optical disc 10A of Example 1 is configured to be a recording / reproducing type have concave and convex grooves. (Grooves) are formed in a spiral shape and have a structure in which a recording / reproducing film is formed on the groove pattern. In the following description, both are included for recording or reproducing. Will be described as an uneven pit or groove pattern for signals.

  Here, the optical disk 10A of the first embodiment according to the present invention will be specifically described with reference to FIGS.

  First, when the optical disk 10A of Example 1 has two signal surfaces conforming to the BD standard, the light transmissive resin sheet 11 is set to a thickness of approximately 0.075 mm.

  In addition, the light-transmitting resin sheet 11 has a signal concavo-convex pit or groove pattern (corrugated shape) on the other surface opposite to the one surface that is the incident surface side of the laser beam L. Signal pattern) 11b, and a concave-convex pit or groove pattern (protrusion-shaped dummy pattern) 11a for dummy for preventing warpage and distortion of the light-transmitting resin sheet 11 on the one surface. have. Further, a recording or reproducing transflective film 12 is formed on the other surface, and the surface of the transflective film 12 becomes a BD-L1 layer signal surface 12a.

  The dummy concavo-convex pit or groove pattern 11a formed on one surface of the light-transmitting resin sheet 11 and the signal concavo-convex pit or groove pattern 11b formed on the other surface are both used for pressing. This is transferred from the upper and lower stampers 25 and 26 (FIG. 3), which will be described later.

  Therefore, although the light-transmitting resin sheet 11 has concave and convex pits or groove patterns 11a and 11b formed on both sides, the dummy concave and convex pit or groove pattern 11a formed on one surface is light transmissive. It is formed to prevent warping or distortion of the conductive resin sheet 11 and is outside the focal range of the objective lens (not shown), and does not affect recording or reproduction. On the other hand, the concavo-convex pit or groove pattern 11b for signals conforming to the BD standard formed on the other surface is at the focal position of the objective lens (not shown) and the transflective film 12 is formed. -L1 layer signal surface 12a is obtained.

  At this time, as shown in an enlarged view in FIG. 2, in the light-transmitting resin sheet 11, the total surface area 11a-A of the one surface including the surface area of the concave and convex pits or groove patterns 11a for dummy (in FIG. 2) The surface area of the region indicated by the upper thick line) is the total surface area 11b-A of the other surface including the surface area of the signal concavo-convex pit or groove pattern 11b (the surface area of the region indicated by the lower thick line in FIG. 2). The stress distortion of the light transmissive resin sheet 11 is canceled out, and the warp and distortion of the light transmissive resin sheet 11 can be prevented.

  The total surface areas 11a-A and 11b-A described above can be set to predetermined values depending on the depths Ta and Tb of the unevenness, the shape of pits or grooves, or the number of pits or grooves.

  Therefore, when the total surface area 11a-A on one surface side of the light transmissive resin sheet 11 and the total surface area 11b-A on the other surface side are set to the same value, as described later, the light transmissive resin is used. The uneven pit or groove pattern 11b for signals formed on the other surface of the sheet 11 needs to be transferred using the upper stamper 25 (FIG. 3) functioning as a signal stamper that satisfies the BD standard.

  On the other hand, the concave and convex pits or groove patterns 11a for dummy formed on one surface of the light-transmitting resin sheet 11 do not necessarily conform to the BD standard, and other optical disk standards (for example, DVD standards and CDs). There is no need to comply with (standard). However, if transfer is performed using the lower stamper 26 (FIG. 3) that functions as a dummy stamper in exactly the same shape as the upper stamper 25 (FIG. 3) satisfying the BD standard, the depth of the unevenness Ta, pits or grooves Since the shape, the number of pits or grooves, and the like are the same as the concavo-convex pit or groove pattern 11b for signals formed on the other surface of the light-transmitting resin sheet 11, the total surface area 11a-A, 11a- on both surfaces is the same. B can be set to the same value.

  Next, the disk substrate 16 is formed in a disk shape with a thickness of approximately 1.1 mm, an outer diameter (not shown) of 120 mm, and a hole diameter of a center hole (not shown) of 15 mm, and is formed on one surface of the disk substrate 16. It has concave and convex pits or groove patterns 16a for signals conforming to the BD standard. Further, the disk substrate 16 has a BD-L0 layer signal surface 15a in which a recording or reproducing total reflection film 15 is formed on a signal concavo-convex pit or groove pattern 16a, and further, BD-L0. A light transmission layer 14 having a thickness of 0.025 mm is formed on the layer signal surface 15a.

  The signal concavo-convex pit or groove pattern 16a formed on one surface of the disk substrate 16 is transferred from the upper stamper 33 (FIG. 4) for injection molding, which will be described later.

  Then, the BD-L1 layer signal surface 12a formed on the light transmissive resin sheet 11 and the light transmissive layer 14 formed on the disk substrate 16 are bonded together by an adhesive layer 13 using an adhesive. An optical disc 10A according to the first embodiment is configured.

  In addition, the light-transmitting resin sheet 11 on which the semi-transmissive reflective film 12 was formed without providing the light transmissive layer 14 and the total reflection film 15 was formed on the other surface opposite to the one surface. The disk substrate 16 may be directly bonded to the disk substrate 16 with an adhesive layer using an adhesive. The adhesive layer in this case corresponds to a combination of the adhesive layer 13 and the light transmission layer 14 of FIG.

  Here, in the optical disk 10A of Example 1 according to the present invention, a method for producing the light transmissive resin sheet 11 which is a main part of Example 1 will be described with reference to FIG.

  As shown in FIG. 3, the pressing mold 20 is configured to be able to transfer a fine pattern using a known thermal nanoimprint method.

  In the press mold 20 described above, an upper mold 21 provided on the upper side and a lower mold 22 provided on the lower side are provided to be movable so as to face each other, and the upper and lower molds 21 are provided. , 22 are provided with heaters 23, 24 for softening the light-transmitting resin sheet 11, respectively. At this time, the upper and lower molds 21 and 22 are structured such that the two molds can move in the contacting / separating direction with each other, and the structured form in which either mold is fixed and the other mold is moved in the contacting / separating direction. Either structure may be used.

  The upper mold 21 is provided with an upper stamper (signal stamper) 25 having signal concavo-convex pits or groove patterns 25a conforming to the BD standard.

  On the other hand, a lower stamper (dummy stamper) 26 which is a replica copied from the same master as the upper stamper 25 is attached to the lower mold 22, and this lower stamper 26 is exactly the same as the upper stamper 25. It has an uneven pit or groove pattern 26a formed in a shape.

  Then, in a state where the concave and convex pits or groove patterns 25a, 26a formed on the upper and lower stampers 25, 26 are opposed to each other, and the upper and lower molds 21, 22 are separated from each other, and the molds are opened. The light-transmitting resin sheet 11 having a thickness of 0.075 mm is inserted between the uneven pit or groove pattern 25a formed on the upper stamper 25 and the uneven pit or groove pattern 26a formed on the lower stamper 26. .

  Thereafter, the upper and lower molds 21 and 22 are brought close to each other and clamped, and the heaters 23 and 24 provided in the upper and lower molds 21 and 22 are energized to cause the softening temperature Tg (which has viscosity from solid, respectively). When the upper and lower stampers 25, 26 are pressed onto the softened light transmissive resin sheet 11, the upper and lower stampers 25, The concave and convex pits or groove patterns 25 a and 26 a formed on 26 are respectively transferred to both surfaces of the light transmissive resin sheet 11.

  After the transfer, the energization of the upper and lower heaters 23 and 24 is stopped and cooled, and when the upper and lower molds 21 and 22 are opened, one surface of the light-transmitting resin sheet 11 (the lower side in FIG. 3). Pits or grooves 11a for dummy by the lower stamper 26 are transferred to the surface), and pits or grooves for signals by the upper stamper 25 are transferred to the other surface (upper surface in FIG. 3). The pattern 11b is transferred.

  At this time, since the upper stamper 25 and the lower stamper 26 have exactly the same uneven shape, as described above, the light-transmitting resin sheet 11 includes the surface area of the uneven uneven pit or groove pattern 11a. The total surface area 11a-A of one surface (the surface area of the region shown by the upper thick line in FIG. 2) and the total surface area 11b-A of the other surface including the surface area of the signal concavo-convex pit or groove pattern 11b ( Since the surface area of the region indicated by the lower thick line in FIG. 2 is exactly the same value, the stress-strain of the light-transmitting resin sheet 11 is offset and the warp and distortion of the light-transmitting resin sheet 11 are prevented. The light transmissive resin sheet 11 can be manufactured with high productivity.

  Next, a process of manufacturing the optical disc 10A of Example 1 by bonding the light transmissive resin sheet 11 and the disc substrate 16 using an adhesive will be described with reference to FIG.

  First, as described above, the light-transmitting resin sheet 11 side warps and distorts uneven pits or groove patterns 11a and 11b having the same shape on both surfaces by upper and lower stampers 25 and 26 having the same shape in accordance with the BD standard. BD-L1 layer signal surface 12a for recording or reproduction by semi-transparent reflective film 12 is formed on the concavo-convex pits or groove pattern 11b for the signal surface, and thereafter light transmission is performed. The conductive resin sheet 11 is inverted so that the BD-L1 layer signal surface 12a side faces the disk substrate 16 side.

  On the other hand, when the disk substrate 16 is manufactured, the injection mold 30 is provided such that an upper mold 31 provided on the upper side and a lower mold 32 provided on the lower side face each other so as to be movable. In addition, an upper stamper 33 having signal concavo-convex pits or groove patterns 33a conforming to the BD standard is attached to the upper die 31, but the lower die 32 is not attached with a stamper. The surface facing the upper stamper 33 is formed flat.

  After the upper and lower molds 31 and 32 are clamped, the molten resin 34 is put into a cavity (not shown) formed between the upper stamper 33 and the lower mold 32 attached to the upper mold 31. By injecting, a concave / convex pit or groove pattern 16a for signals conforming to the BD standard is formed on one surface (the upper surface in FIG. 4) of the disk substrate 16.

  Thereafter, a recording or reproducing BD-L0 layer signal surface 15a by the total reflection film 15 is formed on the concavo-convex pit or groove pattern 16a for signal formed on one surface of the disk substrate 16, and further, A transparent UV resin is applied on the reflective film 15 and spread by a high-speed spin device (not shown) to form a light transmission layer 14 having a thickness of 0.025 mm.

  Then, the BD-L1 layer signal surface 12a on the light transmissive resin sheet 11 side and the light transmissive layer 14 on the disk substrate 16 side are bonded together via the adhesive layer 13 to produce the optical disk 10A of Example 1. It can be manufactured with good performance.

FIG. 5 is a longitudinal sectional view showing an optical disk according to a second embodiment of the present invention.
FIG. 6 illustrates the total surface area of each surface including the surface area of the concavo-convex pit or groove pattern formed on one surface and the other surface of the light-transmitting resin sheet in the optical disk of Example 2 according to the present invention. It is the longitudinal cross-sectional view typically cut in order to do.
FIG. 7 is a diagram schematically showing a process for producing a light-transmitting resin sheet in the optical disc of Example 2 according to the present invention.
FIG. 8 is a diagram schematically showing the case where the total surface area 11c-A> the total surface area 11b-A when manufacturing the optical disk of Example 2 according to the present invention.
FIG. 9 is a diagram schematically showing a case where the total surface area 11c-A <the total surface area 11b-A when manufacturing the optical disc of Example 2 according to the present invention.

  The optical disc 10B of the second embodiment according to the present invention shown in FIG. 5 has the same configuration except for the configuration of the optical disc 10A of the first embodiment described above, and is shown here for convenience of explanation. The constituent members described above are given the same reference numerals, and the constituent members shown above are appropriately described as necessary, and different parts of the first embodiment are assigned different reference numerals. The explanation will be centered.

  As shown in FIG. 5, the optical disc 10B according to the second embodiment of the present invention is similar to the first embodiment in that the optically transparent resin sheet (first plate) is a thin substrate formed using, for example, transparent polycarbonate. 2) 11 and a disk substrate (first substrate) 16 formed with a thicker thickness than the light-transmitting resin sheet 11 using, for example, transparent polycarbonate, and bonded using an adhesive It has a substrate.

  The optical disc 10B has, for example, two signal surfaces conforming to the ultra-high density BD (Blu-ray Disc) standard, and laser light having a wavelength of about 405 nm is about 0.8 to about NA. By irradiating the laser beam L obtained by focusing with an objective lens (not shown) of about 0.85 from the light-transmitting resin sheet 11 side toward the disk substrate 16 side, the two-layer signal surface is irradiated. It is configured to be recordable or reproducible.

  Similarly to the first embodiment, the two-layer signal surface of the optical disc 10B of the second embodiment is also formed from the laser beam incident surface when one surface (11a) of the light transmissive resin sheet 11 is a laser beam incident surface. A BD-L1 layer signal surface 12a is formed at a position separated by approximately 0.075 mm, and a BD-L0 layer signal surface 15a is formed at a position separated by 0.025 mm from the BD-L1 layer signal surface 12a. .

  Further, the BD-L1 layer signal surface 12a is formed on the other surface (11b) side opposite to the one surface (11a) of the light transmissive resin sheet 11, and the BD-L0 layer signal surface 15a is light. It is formed on one surface (16 a) of the disk substrate 16 via the transmission layer 14.

  Here, differences from the first embodiment in the optical disc 10B of the second embodiment will be described. The light-transmitting resin sheet 11 set to a thickness of about 0.075 mm has a concave-convex pit or groove pattern (concave-concave dummy pattern) 11c for dummy on one surface 11c on the incident surface side of the laser beam L. In addition, the other surface opposite to the one surface has signal concavo-convex pits or groove patterns (concavo-convex signal pattern) 11b conforming to the BD standard and conforms to the BD standard. It has a BD-L1 layer signal surface 12a on which a recording or reproducing transflective film 12 is formed on the uneven pit or groove pattern 11b for signal.

  The dummy uneven pit or groove pattern 11c formed on one surface of the light-transmitting resin sheet 11 and the signal uneven pit or groove pattern 11b formed on the other surface are both vertically The concavo-convex pits or groove patterns 11c for dummy formed on one surface of the light-transmitting resin sheet 11 are not related to recording or reproduction. It is a pattern.

  The above points have substantially the same technical idea as the first embodiment described above.

  However, as shown in an enlarged view in FIG. 6, the second embodiment differs from the first embodiment in the light-transmitting resin sheet 11 that includes the surface area of the concave and convex pits or groove patterns 11c for dummy. The total surface area 11c-A of the surface (the surface area of the region shown by the upper thick line in FIG. 6) includes the surface area of the signal concavo-convex pit or groove pattern 11b. Is set in advance to a value different from the surface area of the region indicated by the lower bold line ΔΔ.

  A feature of the second embodiment is that a predetermined stress strain is generated in the light transmissive resin sheet 11 in accordance with the ratio of the total surface area 11c-A on the dummy side to the total surface area 11b-A on the signal side. One.

  Naturally, this stress strain is smaller than that of the dummy uneven pit or groove pattern 11c. Therefore, rather than the difference in shape between the flat laser beam incident surface 103a which is one surface and the uneven signal surface 103b formed on the other surface in the conventional transparent film 103 described above with reference to FIG. Since the difference in shape between both surfaces of the light-transmitting resin sheet 11 is small, warpage and distortion generated in the light-transmitting resin sheet 11 can be suppressed to a low level, and when the light-transmitting resin sheet 11 is bonded to the disk substrate 16. As will be described later, the bubbles of the adhesive can be eliminated by the direction of the minute warp generated in the light transmissive resin sheet 11.

  The total surface area 11c-A on the dummy side can be set to a predetermined value depending on the depths Tc and Tb of the unevenness, the shape of pits or grooves, or the number of pits or grooves.

  Note that the uneven pit or groove pattern 11c for dummy does not necessarily conform to the BD standard, and does not need to conform to other optical disc standards (for example, DVD standard and CD standard).

  Here, in the optical disk 10B of Example 2 according to the present invention, the manufacturing method of the light-transmitting resin sheet 11 which is a main part of Example 2 is mainly different from Example 1 with reference to FIG. I will explain.

  As shown in FIG. 7, the upper mold 21 provided on the upper side of the press mold 20 is provided with a concavo-convex pit or groove pattern 25a for signals conforming to the BD standard, as in the first embodiment. An upper stamper (signal stamper) 25 is attached.

  On the other hand, unlike the first embodiment, the lower mold 22 provided on the lower side of the press mold 20 is provided with an uneven pit or groove pattern 25a for signal of the upper stamper (signal stamper) 25. A lower stamper (dummy stamper) 27 having uneven pits or groove patterns 27a for dummy different from the above is attached.

  Then, with the upper and lower molds 21 and 22 spaced apart from each other, the concave and convex pits or grooves 25a formed on the upper stamper 25 and the concave and convex pits or grooves formed on the lower stamper 27 are opened. A light transmissive resin sheet 11 having a thickness of 0.075 mm is inserted between the pattern 27a.

  Thereafter, the upper and lower molds 21 and 22 are brought close to each other and clamped, and the heaters 23 and 24 provided in the upper and lower molds 21 and 22 are energized to cause the softening temperature Tg (which has viscosity from solid, respectively). When the upper and lower stampers 25, 27 are pressed onto the softened light transmissive resin sheet 11, the upper and lower stampers 25, The concavo-convex pit or groove patterns 25 a and 26 a formed on 27 are transferred to the light transmissive resin sheet 11.

  After the transfer, the energization of the upper and lower heaters 23 and 24 is stopped and cooled, and when the upper and lower molds 21 and 22 are opened, a dummy by the lower stamper 27 is formed on one surface of the light transmitting resin sheet 11. The concavo-convex pit or groove pattern 11c for transfer is transferred, and the concavo-convex pit or groove pattern 11b for signal by the upper stamper 25 is transferred to the other surface.

  At this time, since the upper stamper 25 and the lower stamper 27 have different concavo-convex shapes, as described above, in the light-transmitting resin sheet 11, the above-mentioned one including the surface area of the concavo-convex pit or groove pattern 11c for the dummy is used. Since the total surface area 11c-A (FIG. 6) of the first surface is different from the total surface area 11b-A (FIG. 6) of the other surface including the surface area of the signal concavo-convex pit or groove pattern 11b, Although warpage and distortion are less than those of the conventional transparent film 103 described with reference to FIG. 11, very slight warpage and distortion occur in the light-transmitting resin sheet 11.

  That is, the total surface area 11c-A (FIG. 6) of the one surface including the surface area of the dummy uneven pit or groove pattern 11c is changed to the other surface including the surface area of the signal uneven pit or groove pattern 11b. When the surface area is set to a value larger than the total surface area 11b-A (FIG. 6), as shown in FIG. 8, the concave and convex pits or groove patterns 11c for dummy are formed in the light transmitting resin sheet 11. The warped or distorted surface is slightly convex on the one surface and the other surface on which the signal concavo-convex pit or groove pattern 11b is formed is slightly concave.

  Then, if the disc substrate 16 side has a warp or strain that is opposite to the slight warp or strain that has occurred in the light-transmitting resin sheet 11, the warp or strain between the both 11 and 16 can be canceled together. Therefore, it is possible to prevent warpage and distortion of the optical disc 10B of Example 2 after being bonded, and to manufacture the optical disc 10B satisfactorily.

  On the other hand, as shown in FIG. 9, the total surface area 11c-A (FIG. 6) of one surface including the surface area of the dummy uneven pit or groove pattern 11c is converted into the signal uneven pit or groove pattern 11b. When the surface area 11b-A (FIG. 6) of the other surface including the surface area is set to a value smaller than that of FIG. The one surface side where the pit or groove pattern 11c is formed is slightly concave, and the other surface side where the signal concavo-convex pit or groove pattern 11b is formed is slightly convex. Distortion occurs.

  Even in the case shown in FIG. 9, if the disk substrate 16 side is warped or distorted in the opposite direction to the slight warpage or distortion generated in the light transmitting resin sheet 11, both 11 , 16 can cancel each other out of warpage and distortion, and further, a slight amount generated on the other surface (11b) side of the light transmissive resin sheet 11 when the light transmissive resin sheet 11 is bonded to the disk substrate 16. Due to the convex warpage, the light-transmitting resin sheet 11 can be adhered to the disk substrate 16 from the center to the outside, so that air bubbles of the adhesive can be improved and the optical disk 10B of Example 2 can be further improved. It can be manufactured satisfactorily.

  Accordingly, the bonding is performed by setting the ratio of the total surface area 11c-A (FIG. 6) on the dummy side to the total surface area 11b-A (FIG. 6) on the signal side in accordance with the amount of warpage and distortion of the disk substrate 16. The warp and distortion of the subsequent bonded substrate can be completely canceled.

  In the optical disks 10A and 10B according to the first and second embodiments described in detail above, the case where the signal surface conforming to the BD standard has two layers has been described. However, it is sufficient that the signal surface conforming to the BD standard has one or more layers. In addition, the optical disk may be a combination of a signal surface conforming to the BD standard and a signal surface conforming to the DVD standard.

  Further, it may be an optical disc standard other than the BD standard. For example, a first substrate in which one surface is formed flat as a laser beam incident surface and the other surface opposite to the one surface is a signal surface conforming to the DVD standard, and one surface is a dummy pattern surface. And a second substrate having a signal surface in conformity with the CD standard on the other surface opposite to the one surface, and a signal surface of the first substrate and a dummy pattern surface of the second substrate. An optical disc bonded with an adhesive may also be used. That is, each thickness of the constituent substrate may be determined according to a combination state of signal surfaces of the optical disc.

It is the longitudinal cross-sectional view which showed the optical disk of Example 1 which concerns on this invention. In the optical disk of Example 1 according to the present invention, in order to explain the total surface area of each surface including the surface area of the uneven pit or groove pattern formed on one surface and the other surface of the light-transmitting resin sheet, respectively. It is the longitudinal cross-sectional view typically shown. In the optical disk of Example 1 which concerns on this invention, it is the figure which showed typically the process of producing a transparent resin sheet. It is the figure shown typically in order to demonstrate the manufacturing method of the optical disk of Example 1 which concerns on this invention. It is the longitudinal cross-sectional view which showed the optical disk of Example 2 which concerns on this invention. In the optical disk of Example 2 according to the present invention, in order to explain the total surface area of each surface including the surface area of the concavo-convex pit or groove pattern respectively formed on one surface and the other surface of the light transmissive resin sheet It is the longitudinal cross-sectional view typically shown. In the optical disk of Example 2 which concerns on this invention, it is the figure which showed typically the process of producing a transparent resin sheet. When manufacturing the optical disk of Example 2 which concerns on this invention, it is the figure which showed typically the case where the total surface area 11c-A> total surface area 11b-A. When manufacturing the optical disk of Example 2 which concerns on this invention, it is the figure which showed typically the case where the total surface area 11c-A <total surface area 11b-A. It is the longitudinal cross-sectional view which showed the prior art example of the optical disk using a transparent film. In a prior art example, it is the longitudinal cross-sectional view which showed typically the state which a curvature produces in a transparent film when a signal surface is formed in a transparent film.

Explanation of symbols

10A: the optical disc of Example 1,
10B: optical disc of Example 2,
11 ... Light transmissive resin sheet (second substrate),
11a: uneven pit or groove pattern (dummy pattern) for dummy,
11a-A: the total surface area of the concave-convex pit or groove pattern for the dummy,
11b ... Signal concavo-convex pit or groove pattern (concavo-convex signal pattern),
11b-A: The total surface area of the concavo-convex pit or groove pattern for signals,
11c... Concave or convex pit or groove pattern (concave and convex dummy pattern),
11c-A: the total surface area of the concave-convex pit or groove pattern for the dummy,
12 ... Semi-transmissive reflective film, 12a ... BD-L1 layer signal surface, 13 ... Adhesive layer,
14 ... light transmission layer, 15 ... total reflection film, 15a ... BD-L0 layer signal surface,
16: Disc substrate (first substrate),
16a: Uneven pit or groove pattern for signals,
20 ... Die for press,
21 ... Upper mold, 22 ... Lower mold,
23, 24 ... Upper and lower heaters,
25 ... Upper stamper (signal stamper),
25a: Uneven pit or groove pattern for signals,
26 ... Lower stamper (dummy stamper),
26a: uneven pit or groove pattern for dummy,
27 ... Lower stamper (dummy stamper),
27a: concave and convex pit or groove pattern for dummy,
30 ... Injection mold,
31 ... Upper mold, 32 ... Lower mold,
33: Upper stamper, 33a: Uneven pit or groove pattern for signals,
34. Molten resin,
Ta, Tb, Tc: depth of unevenness, Tg: softening temperature.

Claims (6)

A first substrate;
A dummy pattern surface bonded to the first substrate and having one surface having an uneven dummy pattern, and the other surface opposite to the one surface is an uneven signal conforming to a predetermined optical disc standard. A second substrate which is a signal surface having a pattern;
An optical disc comprising: The optical disc according to claim 1,
In the optical disk, the second substrate has the same total surface area of the signal surface including the surface area of the signal pattern and the entire surface area of the dummy pattern surface including the surface area of the dummy pattern. . The optical disc according to claim 1,
In the second substrate, the total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern have different values from each other, and A ratio of a total surface area of the dummy pattern surface to a total surface area is set in accordance with a warp amount or a distortion amount of the first substrate before bonding. A first step of producing a first substrate;
A concave / convex dummy pattern is formed on one surface of a second substrate different from the first substrate so that the one surface is a dummy pattern surface, which is opposite to the one surface of the second substrate. A second step of forming a concave-convex signal pattern conforming to a predetermined optical disc standard on the other surface of the second surface and using the other surface as a signal surface;
A third step of bonding the first substrate and the second substrate after the first and second steps;
An optical disc manufacturing method characterized by comprising: In the second step,
5. The optical disk manufacturing according to claim 4, wherein the total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern are set to the same value. Method. In the second step,
The total surface area of the signal surface including the surface area of the signal pattern and the total surface area of the dummy pattern surface including the surface area of the dummy pattern are different from each other, and the dummy pattern surface with respect to the total surface area of the signal surface 5. The method of manufacturing an optical disc according to claim 4, wherein the ratio of the total surface area is set in accordance with a warpage amount or a distortion amount of the first substrate before bonding.

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