JP2006277919A - Stamper, die and method for manufacturing optical disk substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stamper by which substrates having uniform thickness distribution can be reproduced, in a manufacturing method of an optical disk substrate wherein a cycle time is shortened and manufacturing efficiency is high. <P>SOLUTION: The stamper 10 has an increasing shape from an inner peripheral part 13 to an outer peripheral part 14 so that the difference between thicknesses of the outer peripheral part 14 and the inner peripheral part 13 of an annular base body 11 is ≥5 μm. In the thickness distribution in a recording area of the optical disk substrate molded by a die to which the stamper 10 is attached, the difference (Smax-Smin) between the maximum value (Smax) and the minimum value (Smin) in thickness is <10 μm and the optical disk substrate can be used as a disk substrate especially for a multilayered optical recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stamper used when manufacturing an optical disk substrate, and more particularly to a stamper suitable for a manufacturing process of a multilayer optical recording medium with a short cycle time.

  Optical disc substrates such as CDs (compact discs) and DVDs (digital versatile discs) are melted in a cavity formed between a mold with a stamper on one side and the other mold. The resin is injected and filled, and after cooling, the molded product is removed from the mold.

  Specifically, a mold for manufacturing an optical disk substrate is generally installed such that a fixed mold core and a movable mold core face each other via an outer ring. In general, a stamper is attached to either the mold surface of the fixed mold core or the mold surface of the movable mold core. That is, a cavity is formed by a mold (either a fixed-side mold core or a movable-side mold core that is attached to the stamper) to which a stamper is attached, and a mold and an outer peripheral ring that face the mold.

Here, the thickness distribution of the optical disk substrate corresponding to the recording area of the optical disk is preferably uniform. For this reason, in general, the above-mentioned mold is horizontally (parallel) from the position corresponding to the innermost circumference of the recording area of the optical disk to the position corresponding to the outermost circumference, with the mold attached to the stamper and the opposite mold. It is installed to become. In other words, by using a stamper having a uniform thickness, the distance between the stamper surface and the opposing mold is uniform from a position corresponding to the innermost periphery of the recording area of the optical disc to a position corresponding to the outermost periphery. I am doing so.
By the way, as a technique for improving the characteristics of the optical disk substrate, a technique for changing the stamper thickness in the radial direction has been reported (see Patent Document 1).

Japanese Patent Laid-Open No. 6-168383

Although it is important to make the thickness distribution of the optical disk substrate constant, according to the study of the present inventor, in order to increase the productivity of the optical disk substrate, cycle time (time for manufacturing one optical disk substrate) ) Is reduced, the thickness of the substrate fluctuates in the portion corresponding to the recording area of the optical disk substrate, and the uniformity of the thickness decreases.
When an optical disc is prepared using such a substrate, there arises a problem that the recording accuracy of optical information is lowered. In particular, in a multi-layered recording medium having two or more recording layers, the above-described problem becomes more serious when a substrate having a low thickness uniformity in a portion corresponding to a recording area is used.

  That is, the optical disk substrate in the optical recording medium also plays a role of a condensing lens for recording / reproducing laser light. Therefore, if the thickness of the substrate varies, the focal length varies, and as a result, the recording accuracy of optical information decreases. Problem occurs. In the case of a multilayer optical recording medium, since a plurality of recording layers are close to each other and their focal lengths are very close, the thickness of the substrate can be increased with higher accuracy than an optical disc having a single recording layer. Need to control.

The present invention has been made to solve such problems.
That is, an object of the present invention is to provide a stamper capable of replicating a substrate having a uniform thickness distribution, particularly suitable for a multilayer optical recording medium, in a method of manufacturing an optical disc substrate with high cycle efficiency and high production efficiency. is there.
Another object of the present invention is to provide a mold for manufacturing an optical disk substrate for manufacturing a substrate having a uniform thickness distribution.
Another object of the present invention is to provide a method for manufacturing an optical disk substrate having a uniform thickness distribution.

  Therefore, as a result of intensive studies to solve the above-mentioned problems, the present inventor uses a mold attached with a predetermined stamper to mold a resin substrate with an injection molding apparatus, and the cycle time is shortened. Indeed, the difference in cooling rate between the inner and outer peripheral portions of the molded substrate increases, and the resin in the region near the inner peripheral portion of the optical disk substrate tends to be taken out of the mold in an uncured state. I understood. For this reason, it is thought that the thickness of the substrate varies due to the difference in resin shrinkage between the inner peripheral portion and the outer peripheral portion of the substrate, and the present invention has been completed based on such knowledge.

  That is, according to the present invention, an annular stamper for manufacturing an optical disk substrate, wherein the optical disk substrate is an optical disk substrate for a multilayer optical recording medium having a plurality of recording layers, and a recording area of the optical disk substrate The thickness of the outer peripheral portion is made thicker than the thickness of the inner peripheral portion of the stamper so that the difference (Smax−Smin) between the maximum value (Smax) and the minimum value (Smin) of the substrate thickness is less than 10 μm. A stamper is provided that is characterized by

  As described above, the stamper to which the present invention is applied increases the thickness of the outer peripheral portion relative to the thickness of the inner peripheral portion. A portion corresponding to the outer peripheral portion can be thinned in advance. As a result, when the optical disk substrate taken out from the mold is cooled, the thickness of the cooled optical disk substrate can be kept uniform. In addition, in this invention, an annular shape means the shape which is a disk shape and the cavity part of predetermined length is formed from the center of a circle like CD and DVD. In the present invention, the “inner peripheral portion of the stamper” refers to a radial position of the stamper corresponding to the innermost peripheral position of the recording area of the optical disk substrate. On the other hand, the “outer peripheral portion of the stamper” refers to the radial position of the stamper corresponding to the outermost peripheral position of the recording area of the optical disk substrate. That is, the “inner peripheral portion of the stamper” does not necessarily need to be the innermost periphery of the annular stamper. Similarly, the “outer peripheral portion of the stamper” is not necessarily the outermost periphery of the annular stamper.

Here, the difference between the thickness of the outer peripheral portion of the stamper and the thickness of the inner peripheral portion is preferably 5 μm or more. Further, it is preferable that the thickness of the stamper increases from the inner peripheral portion to the outer peripheral portion.
In addition, since an optical disc substrate molded using such a stamper has a thickness distribution of the substrate controlled with higher accuracy, for example, a multi-layer type light having two or more recording layers with an increased recording density. It can be applied to a recording medium.

  Next, according to the present invention, there is provided a mold for molding an annular resin optical disk substrate, the optical disk substrate being an optical disk substrate for a multilayer optical recording medium having a plurality of recording layers, and fixed. A side mold core, an outer ring for forming an outer peripheral edge of the optical disk substrate, a movable side mold core disposed so as to face the fixed side mold core via the outer ring, and a fixed side mold core Or a stamper attached to the mold surface of the movable mold core, and the stamper has a difference (Smax−) between the maximum value (Smax) and the minimum value (Smin) of the substrate thickness in the recording area of the optical disk substrate. A mold is provided in which the outer peripheral portion is thicker than the inner peripheral portion of the stamper so that (Smin) is less than 10 μm.

  Furthermore, according to the present invention, there is provided a method of manufacturing an optical disk substrate using a mold having a stamper mounted on a mold surface of a fixed mold core or a movable mold core, wherein the stamper is the optical disk substrate. Is an optical disk substrate for a multilayer optical recording medium having a plurality of recording layers, and the difference (Smax−Smin) between the maximum value (Smax) and the minimum value (Smin) of the substrate thickness in the recording area of the optical disk substrate is There is provided an optical disc substrate manufacturing method characterized in that the outer peripheral portion is formed thicker than the inner peripheral portion of the stamper so as to be less than 10 μm.

  According to the present invention, an optical disk substrate having a uniform thickness distribution can be obtained.

  Hereinafter, the best mode (embodiment) for carrying out the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Also, the drawings used are used to describe the present embodiment and do not represent the actual size.

(Stamper used for manufacturing optical disk substrates)
First, a stamper used for manufacturing an optical disk substrate will be described. In the present invention, “a stamper used for manufacturing an optical disk substrate” may be simply referred to as a “stamper”.
FIG. 1 is a diagram for explaining an example of a stamper to which the present embodiment is applied. FIG. 1A is a perspective view of the stamper, and FIG. 1B is a cross-sectional view taken along the line AA ′ in FIG. 1A. As shown in FIG. 1A, the stamper 10 includes an annular base body 11 in which an inner peripheral hole 12 is formed. Although not shown, a reverse pattern of a fine concavo-convex pattern formed on the surface of a predetermined glass master by a master cutting operation described later is transferred to the surface 11 a of the base 11. The material constituting the substrate 11 is usually a metal, preferably nickel.

  Next, as shown in FIG. 1B, the thickness of the stamper 10 increases from the inner peripheral portion 13 to the outer peripheral portion 14 along the radial direction of the annular base 11. Here, as can be seen from FIG. 1B, the inner peripheral portion 13 is a radial position corresponding to the innermost peripheral portion of the recording area of the optical disc substrate. On the other hand, the outer peripheral portion 14 is a radial position corresponding to the outermost peripheral portion of the recording area of the optical disk substrate.

In the present embodiment, the thickness (T _out ) of the outer peripheral portion 14 is larger than the thickness (T _in ) of the inner peripheral portion 13 of the base 11 (T _in <T _out ). Specifically, the difference _(T out _{-T in)} the thickness of the peripheral portion 14 _{(T out)} to the thickness of the inner peripheral portion 13 and _{(T in)} of the stamper 10 is usually, 3 [mu] m or more, 5 μm or more. However, the difference in thickness of the peripheral portion 14 _{(T out)} to the thickness of the inner peripheral portion 13 and _{(T in) (T out -T} in) is generally, 25 [mu] m or less, preferably 15μm or less, more preferably 10μm Hereinafter, it is more preferably 8 μm or less.

As described above, the stamper 10 to which the present exemplary embodiment is applied has a thickness (T _out ) of the outer peripheral portion 14 larger than the thickness (T _in ) of the inner peripheral portion 13 of the base 11 (T _in <T _out )), the difference (Smax−Smin) between the maximum value (Smax) and the minimum value (Smin) of the substrate thickness in the recording area is 10 μm by using the die attached thereto. It is possible to manufacture an optical disk substrate that is less than.

However, the above (T _out −T _in ) is a value determined in consideration of the cycle time of manufacturing the optical disk substrate. That is, when the cycle time is set to be relatively long, the thickness distribution of the disk substrate (T _out −T _in ) can be set to be relatively small. On the other hand, when the cycle time is set to be relatively short, it is preferable to set the disk substrate thickness distribution (T _out −T _in ) to be relatively large. Therefore, even if (T _out −T _in ) is set within the above specific numerical range, the thickness distribution of the disk substrate may not be good depending on the setting of the cycle time (for example, comparison described later). Example 2).

As described above, in the present invention, the thickness distribution of the optical disk substrate is determined by the balance between (T _out −T _in ) and the cycle time of manufacturing the optical disk substrate. This is considered to be because if the cycle time is made shorter than before in order to increase production efficiency, the resin in the region near the inner diameter of the optical disk substrate is taken out from the mold in an uncured state.

That is, the resin in the region close to the inner diameter of the optical disk substrate is hardened by being rapidly cooled at room temperature (about 25 ° C.) after being taken out from the mold. For this reason, the resin on the inner diameter side contracts greatly. On the other hand, the resin in the region close to the outer diameter is in a sufficiently cooled state inside the mold. For this reason, the shrinkage of the resin on the outer diameter side is reduced. As a result, a difference in shrinkage occurs between the resin in the vicinity of the outer diameter that is relatively sufficiently cooled inside the mold and the resin in the vicinity of the inner diameter that has been insufficiently cooled. If the cycle time is set to be relatively short, the shrinkage of the resin on the inner diameter side after the optical disk substrate is taken out from the mold becomes large. Therefore, it is preferable to set the (T _out -T _in ) of the stamper to be large. On the other hand, when the cycle time is set to be relatively long, the shrinkage of the resin on the inner diameter side after the optical disk substrate is taken out from the mold becomes smaller than in the case where the cycle time is short. Therefore, even if the (T _out -T _in ) of the stamper is set to be small, it becomes easy to ensure the uniformity of the thickness of the optical disk substrate.

  For example, usually, when a DVD disk substrate having a thickness of 0.6 mm is molded, if the cycle time at the time of molding the substrate is shortened in order to improve productivity, the thickness of the molded substrate is about 10 μm. It was found that the distribution often occurs. The existence of such a thickness distribution is eliminated by making the thickness of the outer peripheral portion of the stamper about 6 μm thicker than the thickness of the inner peripheral portion of the stamper.

Here, in the present embodiment, the radial thickness of the stamper 10 between the inner peripheral portion 13 and the outer peripheral portion 14 is the thickness (T _in ) of the inner peripheral portion 13 and the thickness of the outer peripheral portion 14 ( It may be a numerical value between T _out ). That is, the thickness of the stamper 10 can be arbitrarily changed so as to increase from the inner peripheral portion 13 to the outer peripheral portion 14 along the radial direction. As shown in FIG. 1B, the thickness of the stamper 10 is increased linearly from the inner peripheral portion 13 to the outer peripheral portion 14 along the radial direction of the annular base body 11, The form is not limited to such an aspect. For example, the thickness of the stamper 10 may be gradually increased so as to draw a curve from the inner peripheral portion 13 to the outer peripheral portion 14.

  In the present embodiment, the thickness of the stamper 10 is linearly increased from the inner peripheral portion 13 to the outer peripheral portion 14. However, for example, the thickness of the stamper 10 is increased to draw a quadratic curve. Thus, it is considered that the flatness of the obtained optical disk substrate can be further ensured. Therefore, the thickness distribution of the stamper 10 may be determined in consideration of manufacturing conditions such as the thermal characteristics of the resin used when molding the optical disk substrate and the cycle time (production efficiency) when molding the optical disk substrate.

  In the present embodiment, the case where the thickness of the stamper 10 “increases linearly” is not limited to the case where it increases completely linearly (linear function). It is very difficult industrially to increase the thickness of the stamper 10 completely linearly. For example, even if the thickness of the stamper 10 deviates from the linear increase, an error that inevitably causes this deviation. If it is within the range, it shall be included in “linearly increases”.

  In the present embodiment, the stamper at the innermost periphery 15 of the stamper has the smallest thickness, and the stamper at the outermost periphery 16 of the stamper has the largest thickness (FIG. 1B). However, in the present invention, for the purpose of improving the flatness of the optical disk substrate corresponding to the recording area of the optical disk, the outer peripheral portion 14 is formed thicker than the inner peripheral portion 13 of the stamper. For this reason, the thickness of the stamper on the inner diameter side with respect to the inner peripheral portion 13 can be arbitrarily set. Similarly, the thickness of the stamper on the outer peripheral side of the outer peripheral portion 14 can also be set arbitrarily. Therefore, for example, the stamper thickness may be constant on the inner diameter side of the inner peripheral portion 13 and on the outer diameter side of the outer peripheral portion 14. Further, for example, the thickness of the stamper may be gradually increased toward the innermost periphery of the stamper on the inner diameter side of the inner peripheral portion 13. Further, for example, on the outer diameter side of the outer peripheral portion 14, the stamper thickness may be gradually reduced toward the outermost periphery of the stamper.

(Manufacturing method of stamper used for manufacturing optical disk substrate)
Next, a stamper manufacturing method will be described.
The stamper to which this embodiment is applied is manufactured by the following method, for example. First, a resist is applied to a surface-polished glass substrate. Then, a desired pattern is exposed by a laser cutting machine. Thereafter, the resist is developed to prepare a resist master on which pits / grooves are formed.

  Next, nickel or the like is sputtered on the surface of the resist master to prepare a stamper master on which a nickel conductive film is formed. Thereafter, a nickel film is deposited by an electroforming process to form a stamper master having a thickness close to the final stamper.

  Subsequently, the nickel film is peeled off from the glass substrate, the resist remaining on the surface of the peeled nickel film is removed / washed with a solvent, the back surface of the nickel film is then polished and washed, and finally the inner and outer peripheral parts are processed. To prepare a stamper.

In the stamper manufacturing method to which the present embodiment is applied, for example, the following method can be used as a method for increasing the thickness of the outer peripheral portion than the thickness of the inner peripheral portion of the stamper.
That is, in the electroforming process described above, when nickel is deposited on the surface of the stamper master on which the nickel conductive film is formed, the shape of the shield in the electroformed layer is devised, etc. There is a method of changing the deposition rate of nickel metal. That is, by changing the deposition rate of nickel metal, the nickel film corresponding to the inner peripheral portion of the optical disk substrate is deposited to be thin, and the nickel film corresponding to the outer peripheral portion of the optical disk substrate is increased. Can be deposited.

  As another method for manufacturing the stamper to which the present embodiment is applied, for example, in the electroforming process described above, a nickel film having a thickness larger than the target is formed on the stamper master surface on which the nickel conductive film is formed. Thereafter, the stamper having the desired thickness distribution can be manufactured by adjusting the polishing amount between the inner peripheral side and the outer peripheral side of the stamper by a polishing operation.

(Mold used for manufacturing optical disk substrate)
Next, the metal mold | die used for manufacture of an optical disk board | substrate is demonstrated. In the present invention, the “mold used for manufacturing the optical disk substrate” may be simply referred to as “mold”.
FIG. 2 is a diagram for explaining an example of an optical disk substrate mold to which the present embodiment is applied. FIG. 2 shows a mold 20 for molding an optical disk substrate having a format on one side. A mold 20 shown in FIG. 2 is a mold for molding an annular resin optical disk substrate, and forms a fixed mold core 28 and an outer peripheral end of the molded optical disk substrate. The outer peripheral ring 23 and the movable mold core 21 disposed so as to face the fixed mold core 28 with the outer peripheral ring 23 interposed therebetween. Further, a nickel stamper 25 which is a stamper used for manufacturing an optical disk substrate is attached to the mold surface of the fixed mold core 28.

  As shown in FIG. 2, the mold 20 is filled with molten resin by the surface of the stamper 25 attached to the fixed mold core 28, the surface of the movable mold core 21, and the outer peripheral ring 23. A cavity 29 which is a space to be stored is configured. Here, as can be seen from FIG. 2, the “mold surface” in the present invention refers to surfaces facing each other in the cavity 29 in the fixed mold core 28 and the movable mold core 21.

  The fixed-side mold core 28 has a sprue bush 26 that forms a resin flow path 30 through which molten resin flows, and a fixed-side stamper inner circumferential presser 27 for attaching the stamper 25 to the fixed-side mold core 28. is doing. The movable mold core 21 has a cut punch 22 that performs gate cutting, and a protruding pin 31 provided at the center of the cut punch 22. In addition, an outer peripheral ring stopper 24 for keeping a constant distance between the surface of the stamper 25 and the outer peripheral ring 23 is attached. By using the outer peripheral ring stopper 24, contact between the stamper 25 and the outer peripheral ring 23 can be prevented even when the stamper 25 is thick.

  Here, the stamper 25 attached to the fixed mold core 28 has a shape in which the thickness of the outer peripheral portion is larger than the thickness of the inner peripheral portion of the stamper 25. Using the stamper 25 having such a thickness distribution, an optical disk substrate having an improved thickness distribution can be formed by injecting and filling molten resin into a cavity 29 having a distribution in width in advance.

  As shown in FIG. 2, the mold 20 to which the present embodiment is applied is a stamper 25 only on the mold surface on the fixed mold core 28 side in order to mold an optical disk substrate having a format on one side. Is provided. Here, when an optical disk substrate having a format on both sides is molded, a stamper (not shown) is also used on the mold surface on the movable mold core 21 side, and a movable-side stamper inner peripheral presser (not shown) is used. You can install it. In this case, the stamper to be used may be a stamper having a different thickness between the inner peripheral portion and the outer peripheral portion as described above, or may be a stamper having a constant thickness.

  In FIG. 2, the outer ring 23 and the movable mold core 21 are configured as separate bodies. However, for example, the outer ring 23 and the movable mold core 21 may be integrated.

(Manufacturing method of optical disk substrate)
Next, an example of a method for manufacturing an optical disk substrate using the mold 20 used for manufacturing the optical disk substrate will be described.
First, after setting the mold temperature of the mold 20 to about 100 ° C. to 140 ° C., the movable mold core 21 and the fixed mold core 28 are closed, and the resin flow path 30 of the sprue bush 26 is passed through the resin flow path 30. A molten resin at 300 ° C. to 400 ° C. is filled into the cavity 29 within about 0.5 seconds, the cut punch 22 is advanced to perform gate cutting, and a central portion of the molded resin is punched to form an opening.

  Here, the resin melting temperature may be a predetermined temperature depending on the synthetic resin used. For example, when the material of the optical disk substrate is polycarbonate resin, the resin melting temperature is usually set to 300 ° C. or higher and 400 ° C. or lower, preferably 350 ° C. or higher and 400 ° C. or lower. As a synthetic resin constituting the substrate, an acrylic resin, a polystyrene resin, a polyolefin resin, a liquid crystal polymer resin, and the like are used in addition to a polycarbonate resin.

Information on the stamper 25 is transferred to the resin using a predetermined clamping pressure. Here, the mold clamping force of the substrate molding surface is usually controlled to be 20 tons or more, preferably 30 tons or more, and usually 60 tons or less, preferably 40 tons or less.
Thereafter, the mold 20 is cooled, and a substrate is formed in the cavity 29. After the substrate is molded, the movable mold core 21 is opened. At that time, the stamper 25 is released from the substrate. The substrate remaining on the movable mold core 21 is taken out by a discharge device (not shown) provided separately.

These series of operations are normally performed in 10 seconds or less, but in this embodiment, from the viewpoint of improving productivity, it is preferably set to 5 seconds or less, and more preferably set to 4 seconds or less. Although it is preferable that the time required for these series of operations is short, in practice, a time of at least about 3 seconds is required.
Further, the cut punch 22 is filled with the residue of the resin filled and punched through the resin flow path 30, but this residual resin is pulled out from the fixed mold core 28 as the mold is opened. The protrusion pin 31 disposed at the center of the cut punch 22 is moved forward to be taken out from the cut punch 22.

  Here, it is preferable that the mold temperature is relatively high. By making the mold temperature relatively high, the cooling rate of the entire substrate is slowed down, and it is difficult to form a thick portion near the end surface of the outer peripheral portion of the substrate. However, when the mold temperature is increased, the mechanical properties of the substrate tend to deteriorate. A preferable mold temperature is 100 ° C to 140 ° C.

  In addition, the shape of the board | substrate shape | molded using the metal mold | die 20 mentioned above is an annular | circular shape made from a synthetic resin which has a circular opening part in the center. The diameter of the substrate and the diameter of the opening are set according to the standard.

  The optical disk substrate manufactured using the mold 20 to which this embodiment is applied is required to have a predetermined flatness. Specifically, with respect to the thickness of the substrate in the recording area of the optical disk substrate measured using a predetermined measuring device, the maximum value (Smax) and the minimum value (Smax) of the thickness from the inner peripheral part to the outer peripheral part of the recording area ( The difference (Smax−Smin) from Smin is required to be less than 10 μm, preferably 8 μm or less, more preferably 6 μm or less. An optical recording medium having an optical disk substrate in which (Smax−Smin) is within the above-described range has good signal characteristics. The lower limit value of (Smax−Smin) is ideally 0 μm (the thickness of the optical disc substrate is completely uniform).

(Multilayer type optical recording medium)
An optical disk substrate manufactured by a mold used for manufacturing an optical disk substrate to which the present embodiment is applied has improved thickness distribution in the recording area and enhanced flatness. Therefore, the optical disk substrate obtained by the present invention is preferably used as an optical disk substrate for a multilayer optical recording medium that requires higher flatness accuracy than a single-layer recording medium having a single recording layer. It is done. According to the present invention, such a high-precision optical disk substrate can be efficiently manufactured with increased productivity.
Here, the multilayer optical recording medium is an optical recording medium having a plurality of recording layers on one medium, and the number of recording layers is two or more. The number of recording layers is usually 10 or less, preferably 7 or less, more preferably 5 or less.

  Next, a multilayer optical recording medium will be described. As the multilayer optical recording medium, for example, a two-layer optical recording medium of a sticking type in which two disk substrates on which a recording layer and a reflective layer are laminated is formed and pasted through a photocurable resin layer; A two-layer type optical recording medium formed by a 2P (Photo Polymerization) method using a transparent stamper is known. Here, a sticking type two-layer optical recording medium will be described first.

  FIG. 3 is a diagram for explaining an example of a multilayer optical recording medium. In FIG. 3, a disk substrate (reverse laminate 111) in which a reflective layer and a recording layer are laminated on a transparent substrate, a disk substrate (normal laminate 112) in which a recording layer and a reflective layer are sequentially laminated on a transparent substrate, A two-layer optical recording medium 100 is shown.

  As shown in FIG. 3, the optical recording medium 100 includes a disc-shaped light-transmitting substrate (1) 101 in which grooves and lands or prepits are formed as an inverse laminated body 111, and a laser of the substrate (1) 101. It has a reflective layer (1) 102 provided on the incident surface side of the light 110, a recording layer (1) 103 containing a dye, and an intermediate layer 104. Further, as the regular laminate 112, a disc-shaped light-transmitting substrate (2) 109 having grooves and lands or pre-pits, and a recording layer (2) 108 containing a dye provided on the substrate (2) 109 are used. And a translucent reflective layer (2) 107 that distributes the power of the laser light 110 incident from the substrate (2) 109 side, and a protective coating layer 106 provided on the reflective layer (2) 107. The reverse laminated body 111 and the normal laminated body 112 are laminated via the transparent resin layer 105 so that the intermediate layer 104 and the protective coat layer 106 face each other, thereby constituting a two-layer optical recording medium 100. ing. The recording layer (1) 103 and the recording layer (2) 108 are recorded and reproduced with optical information by the laser beam 110 incident from the substrate (2) 109 side of the positive laminate 112.

(Reverse laminate)
The inverse laminated body 111 may be referred to as a substrate (1) 101, a reflective layer (1) 102, a recording layer (1) 103, and an intermediate layer 104 (hereinafter referred to as L1 layer) laminated on the substrate (1) 101. ).

(Substrate (1))
It is desirable that the material constituting the substrate (1) 101 is excellent in moldability, such as easy injection molding. Furthermore, it is desirable that the hygroscopicity is small. Furthermore, it is desirable to provide shape stability so that the optical recording medium 100 has a certain degree of rigidity. Such a material is not particularly limited, and examples thereof include acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like. Among these, polycarbonate is preferable from the viewpoints of high productivity such as optical characteristics and moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoints of chemical resistance and low hygroscopicity. The substrate (1) 101 is obtained by the method for manufacturing an optical disk substrate of the present invention.

(Reflective layer (1))
The material constituting the reflective layer (1) 102 of the reverse laminated body 111 is not particularly limited. For example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf , V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, rare earth metals, and the like It is possible to use the metal alone or as an alloy. Among these, Au, Al, and Ag are preferable, and a metal material containing 50% or more of Ag is particularly preferable from the viewpoint of low cost and high reflectance.

Moreover, it is preferable to contain 0.1 atomic% to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au, and rare earth metals. When two or more elements are included among Ti, Bi, Zn, Cu, Pd, Au, and rare earth metals, each content may be 0.1 atomic% to 15 atomic%, but the total content thereof It is preferable that the amount is 0.1 atomic% to 15 atomic%.
Examples of the method for forming the reflective layer (1) 102 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.

  It is desirable that the reflective layer (1) 102 in the reverse laminated body 111 has high reflectivity and high durability. In order to ensure a high reflectance, the thickness of the reflective layer (1) 102 is usually 30 nm or more, preferably 40 nm or more, and more preferably 50 nm or more. However, in order to shorten the production tact time and reduce the cost, it is usually 400 nm or less, preferably 300 nm or less.

(Recording layer (1))
The recording layer (1) 103 in the reverse laminated body 111 usually contains a dye having the same sensitivity as that of a recording layer used in a single-sided recording medium such as CD-R, DVD-R, DVD + R, and the like. Such a dye is preferably a dye compound having a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 nm to 900 nm and suitable for recording with a blue to near microwave laser. Among them, a near-infrared laser having a wavelength of about 770 nm to 830 nm (for example, 780 nm and 830 nm) used for a normal CD-R, and a red laser having a wavelength of about 620 nm to 690 nm for a DVD-R (for example, 635 nm, (660 nm, 680 nm), and a dye suitable for recording by a so-called blue laser or the like having a wavelength of 410 nm or 515 nm. It is also possible to use a phase change material.

  Although it does not specifically limit as a pigment | dye used for the recording layer (1) 103, Usually, an organic pigment | dye material is used. Organic dye materials include, for example, macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, azurenium And dyes containing metal, metal-containing azo dyes, metal-containing indoaniline dyes, and the like. Among these, metal-containing azo dyes are preferable because they are excellent in recording sensitivity and excellent in durability and light resistance. These dyes may be used alone or in combination.

  The film formation method of the recording layer (1) 103 is not particularly limited, but generally a thin film forming method generally performed such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spin coating method, or an immersion method is used. Although mentioned, a wet film-forming method such as a spin coat method is preferable from the viewpoint of mass productivity and cost. Moreover, the vacuum evaporation method is preferable from the point that a uniform recording layer is obtained.

  The thickness of the recording layer (1) 103 of the reverse laminate 111 is usually 50 nm or more, preferably 60 nm or more, but usually 150 nm or less, preferably 100 nm or less. When the thickness of the recording layer (1) 103 is within this range, it is possible to suppress a decrease in sensitivity while ensuring a sufficient recording signal amplitude. Further, when the thickness of the recording layer (1) 103 is excessively large, the sensitivity may be lowered.

(Middle layer)
The intermediate layer 104 is provided on the reverse stacked body 111 as necessary. In general, the intermediate layer 104 is provided between the recording layer (1) 103 and the transparent resin layer 105 in order to prevent components that ooze from the transparent resin layer 105 from contaminating or dissolving the recording layer (1) 103. It is done. The thickness of the intermediate layer 104 is usually 1 nm or more, preferably 2 nm or more. If the thickness of the intermediate layer 104 is within this range, the component that exudes from the transparent resin layer 105 can be effectively suppressed. However, the thickness of the intermediate layer 104 is preferably 2000 nm or less, and more preferably 500 nm or less. When the thickness of the intermediate layer 104 is within this range, it is possible to prevent a decrease in light transmittance. Further, in the case where the intermediate layer 104 is a layer made of an inorganic material, it may take time to form a film. Therefore, in order to suppress a decrease in productivity and increase the film stress in a favorable range, The thickness is preferably 200 nm or less. In particular, when a metal is used for the intermediate layer 104, the thickness of the intermediate layer 104 is preferably 20 nm or less in order to prevent the light transmittance from being excessively reduced.

Examples of the material constituting the intermediate layer 104 include dielectrics such as a metal thin film, silicon oxide, silicon nitride, MgF ₂ , SnO ₂ , and ZnS—SnO ₂ .
Incidentally, between the substrate (1) 101 and the recording layer (1) 103, between the substrate (2) 109 and the recording layer (2) 108, and between the recording layer (2) 108 and the reflective layer (2) 107. Alternatively, a layer made of the same material as the intermediate layer 104 may be provided.

(Transparent resin layer)
The transparent resin layer 105 in the two-layer optical recording medium 100 is made of a light-transmitting material that allows the laser light 110 incident from the substrate (2) 109 side to reach the recording layer (1) 103. Examples of the material constituting the transparent resin layer 105 include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin (including a delayed curable type), and the like. The material which comprises the transparent resin layer 105 is suitably selected from these. A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent as necessary to prepare a coating solution, applying the solution, and drying (heating). The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiating with ultraviolet light. These materials may be used alone or in combination.

  Among the materials constituting the transparent resin layer 105, an ultraviolet curable resin is preferable because of its high transparency and a short curing time, which is advantageous in manufacturing. Examples of the ultraviolet curable resin include a radical ultraviolet curable resin and a cationic ultraviolet curable resin, both of which can be used. As the radical ultraviolet curable resin, a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As an ultraviolet curable compound, monofunctional (meth) acrylate and polyfunctional (meth) acrylate can be used as a polymerizable monomer component. These can be used alone or in combination of two or more. Here, acrylate and methacrylate are collectively referred to as (meth) acrylate.

(Normal laminate)
The positive laminate 112 constituting the optical recording medium 100 includes a substrate (2) 109 having an incident surface of a laser beam 110 as recording / reproducing light, a recording layer (2) 108, and a reflective layer on the substrate (2) 109. (2) 107 and a protective coat layer 106 are sequentially laminated (hereinafter also referred to as L0 layer).
The substrate (2) 109 of the normal laminate 112 is made of the same material as the substrate (1) 101 of the reverse laminate 111. However, the substrate (2) 109 needs to be light transmissive. The substrate (2) 109 is obtained by the method for manufacturing an optical disk substrate of the present invention.

(Recording layer (2))
The recording layer (2) 108 of the normal laminate 112 contains the same dye as the recording layer (1) 103 of the reverse laminate 111. The thickness of the recording layer (2) 108 of the positive laminate 112 is not particularly limited because the suitable film thickness varies depending on the recording method or the like, but is usually 20 nm or more, preferably 30 nm, in order to obtain a sufficient degree of modulation. It is above, Especially preferably, it is 40 nm or more. However, since it is necessary to transmit light, it is usually 200 nm or less, preferably 180 nm or less, more preferably 150 nm or less.

(Reflective layer (2))
The reflective layer (2) 107 of the normal laminate 112 is made of the same material as the reflective layer (1) 102 of the reverse laminate 111. The reflective layer (2) 107 of the positive laminate 112 has a small absorption of the laser beam 110, which is recording / reproducing light incident from the substrate (2) 109 side, has a light transmittance of usually 40% or more, and is usually Therefore, it is necessary to have an appropriate light reflectance of 30% or more. For example, an appropriate transmittance can be provided by providing a thin metal with high reflectivity. Moreover, it is desirable that there is some degree of corrosion resistance. Furthermore, the recording layer (2) 108 positioned below the reflective layer (2) 107 is not affected by other components that ooze out from the upper layer (here, the transparent resin layer 105) of the reflective layer (2) 107. It is desirable to have sex.
The thickness of the reflective layer (2) 107 is usually 50 nm or less, preferably 30 nm or less, more preferably 25 nm or less in order to ensure a light transmittance of 40% or more. However, since the recording layer (2) 108 is not affected by the component exuding from the upper layer of the reflective layer (2) 107, it is usually 3 nm or more, preferably 5 nm or more.

(Protective coat layer)
The protective coating layer 106 of the regular laminate 112 is provided on the transparent resin layer 105 side of the reflective layer (2) 107 for the purpose of preventing oxidation of the reflective layer (2) 107, and preventing dust or scratches. The material of the protective coat layer 106 is not particularly limited as long as it protects the reflective layer (2) 107. Examples of the material of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of the inorganic substance include dielectric materials such as silicon oxide, silicon nitride, MgF2, and SnO2. Especially, it is preferable to laminate | stack an ultraviolet curable resin layer. The protective coat layer 106 is not necessarily provided, and the transparent resin layer 105 may be directly formed on the reflective layer (2) 107.

  As a manufacturing method of the two-layer type optical recording medium 100, for example, the light transmissive resin A is applied on the reverse laminated body 111 having the L1 layer, and on the positive laminated body 112 having the L0 layer. There is a method in which resin B is applied, resin A and resin B are brought into contact with each other and cured to prepare a two-layer disc.

  As a coating method, a method such as a spin coating method or a casting method is used, and among these, the spin coating method is preferable. High-viscosity resin can also be applied and formed by screen printing or the like. As the ultraviolet curable resin, it is preferable to use a resin that is liquid at 20 ° C. to 40 ° C. This is because productivity can be improved because it can be applied without using a solvent. The viscosity of the coating solution is preferably adjusted to be 20 mPa · s to 1000 mPa · s.

  Examples of the multilayer optical recording medium include a two-layer optical recording medium formed by the 2P method using a transparent stamper, in addition to the above-mentioned adhesive two-layer optical recording medium. For example, in the 2P method, a photocurable resin raw material is applied on a first substrate provided with a first recording layer and a first reflective layer, and a transparent stamper having an uneven shape is mounted on the coated surface. After setting, the photocurable resin raw material is cured, and then the transparent stamper is peeled off to transfer the irregularities onto the surface of the photocurable resin. Further, the second recording layer and the second reflective layer are formed on the irregular surface. Are sequentially formed, and finally a second substrate is bonded to manufacture a two-layer optical recording medium. Hereinafter, a two-layer optical recording medium formed by the 2P method will be described.

FIG. 4 is a schematic cross-sectional view showing an optical recording medium formed by the 2P method.
An optical recording medium 400 formed by the 2P method includes a first recording layer containing a dye (first dye-containing recording) on a disk-shaped transparent (light-transmitting) first substrate (first substrate) 401. Layer) 402, a translucent reflective layer (hereinafter referred to as a translucent reflective layer) 403, a transparent resin layer (intermediate layer) 404, a second recording layer containing a dye (second dye-containing recording layer) 405, and a reflective layer 406 , An adhesive layer 407, and a second substrate (second substrate) 408 in this order. The light beam is irradiated from the first substrate 401 side, and recording / reproduction is performed.

Next, each layer will be described.
(1) About the 1st board | substrate 401 The 1st board | substrate 401 is obtained by the manufacturing method of the optical disk substrate of this invention mentioned above. The material is the same as that of the substrate (2) 109 of the sticking type two-layer optical recording medium described above.
In the present optical recording medium 400, it is preferable that the groove portion of the first substrate 401, that is, the convex portion with respect to the light incident direction is the recording track 411. Here, a recessed part and a convex part say the recessed part and convex part with respect to the incident direction of light, respectively. Usually, the groove width is about 200 nm to 500 nm, and the groove depth is about 10 nm to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 μm to 2.0 μm. In addition, it may have uneven pits such as land prepits as necessary.

(2) About the 1st recording layer 402 The 1st recording layer 402 uses the material similar to the recording layer (1) 103 of the reverse laminated body 111 of the sticking type | mold 2 layer type | mold optical recording medium 100 mentioned above. The thickness of the first recording layer 402 is not particularly limited because a suitable film thickness varies depending on the recording method or the like, but is usually preferably 5 nm or more, more preferably 10 nm or more in order to obtain a sufficient degree of modulation. And particularly preferably 20 nm or more. However, in the present optical recording medium 400, since it is not necessary to be too thick in order to transmit light appropriately, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less. The film thickness of the recording layer is usually different between the groove part and the land part, but the film thickness of the recording layer in the optical recording medium 400 is the film thickness in the groove part of the substrate.
The film formation method of the first recording layer 402 is the same as that of the recording layer (1) 103 of the reverse laminate 111 of the sticking-type two-layer optical recording medium 100 described above.

(3) Translucent Reflective Layer 403 The translucent reflective layer 403 is made of the same material, film thickness, and film formation method as those of the reflective layer (2) 107 of the above-mentioned sticking type two-layer optical recording medium 100. .

(4) About the transparent resin layer 404 The transparent resin layer 404 needs to have a light transmittance that allows the laser light incident from the first substrate 401 side to reach the second recording layer 405. Grooves and pits must be able to be formed. Further, it is preferable that the adhesive strength is high and the shrinkage rate at the time of curing and bonding is small, the shape stability of the medium is high.
The transparent resin layer 404 is preferably made of a material that does not damage the second recording layer 405. However, since the transparent resin layer 404 is usually made of a resin, it is easily compatible with the second recording layer 405. In order to prevent this and prevent damage, it is desirable to provide a buffer layer described later between the two layers.

  Furthermore, the transparent resin layer 404 is preferably made of a material that does not damage the translucent reflective layer 403. However, in order to suppress damage, a buffer layer described later can be provided between both layers.

  In the present optical recording medium 400, it is preferable to accurately control the film thickness of the transparent resin layer 404. The film thickness of the transparent resin layer 404 is usually preferably 5 μm or more. In order to separately apply focus servo to the two recording layers, it is necessary to have a certain distance between the two recording layers. Although it depends on the focus servo mechanism, it is usually required to be 5 μm or more, preferably 10 μm or more. In general, the higher the numerical aperture of the objective lens, the smaller the distance tends to be. However, if it is too thick, it takes time to adjust the focus servo to the two recording layers, and the moving distance of the objective lens becomes long, which is not preferable. Moreover, since there are problems such as requiring time for curing and lowering productivity, the thickness is usually preferably 100 μm or less.

  The transparent resin layer 404 is provided with irregularities in a spiral shape or a concentric shape to form grooves and lands. Normally, information is recorded / reproduced in / from the second recording layer 405 using such grooves and / or lands as recording tracks. Usually, since the second recording layer 405 is formed by coating, it becomes thick at the groove and is suitable for recording and reproduction. In the present optical recording medium 400, it is preferable that the groove of the transparent resin layer 404, that is, the convex portion with respect to the light incident direction is the recording track 412. Here, a recessed part and a convex part say the recessed part and convex part with respect to the incident direction of light, respectively. Usually, the groove width is about 200 nm to 500 nm, and the groove depth is about 10 nm to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 μm to 2.0 μm. In addition, it may have uneven pits such as land prepits as necessary.

  From the viewpoint of cost, such irregularities are preferably produced by transferring and curing from a resin stamper having irregularities to a curable resin such as a photocurable resin.

Examples of the material of the transparent resin layer 404 include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin (including a delayed curable type), and the like.
A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent to prepare a coating solution, coating it, and drying (heating). The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiating with ultraviolet light. There are various types of ultraviolet curable resins, and any of them can be used as long as it has the above-described light transmittance. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.

  As a coating method, a method such as a spin coating method or a casting method is used as in the recording layer, and among these, the spin coating method is preferable. Alternatively, a resin having a high viscosity can be formed by screen printing or the like. It is preferable to use an ultraviolet curable resin that is liquid at 20 ° C. to 40 ° C. because the productivity can be applied without using a solvent. The viscosity is preferably adjusted to 20 mPa · s to 1000 mPa · s.

As the ultraviolet curable adhesive, there are a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, both of which can be used.
As the radical ultraviolet curable adhesive, all known compositions can be used, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, monofunctional (meth) acrylate or polyfunctional (meth) acrylate can be used as the polymerizable monomer component. These can be used alone or in combination of two or more. Here, in the present invention, acrylate and methacrylate are collectively referred to as (meth) acrylate.

  Examples of the polymerizable monomer that can be used in the optical recording medium 400 include the following. Examples of the monofunctional (meth) acrylate include methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, Nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone modified tetrahydrofurfuryl, isobornyl , (Meth) acrylate having a group such as dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like.

  Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. Di (meth) such as neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of acrylate, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, neopentyl glycol Diol di (meth) acrylate obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A, triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane Di or tri (meth) acrylate, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) Acrylate, poly (meth) acrylate of dipentaerythritol, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkylated phosphoric acid (meth) acrylate, etc. It is.

  Moreover, what can be used together with the polymerizable monomer includes polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate and the like as polymerizable oligomers.

  Further, as the photopolymerization initiator used in the present optical recording medium 400, any known one that can cure an ultraviolet curable compound represented by a polymerizable oligomer and / or a polymerizable monomer to be used can be used. As the photopolymerization initiator, a molecular cleavage type or a hydrogen abstraction type is suitable for the optical recording medium 400.

  Examples of such include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- ( 4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, etc. are preferably used, and other molecular cleavage types 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Propan-1-one and -Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one or the like may be used in combination, and further a hydrogen abstraction type photopolymerization initiator, benzophenone, 4-phenylbenzophenone, isophthalphenone 4-benzoyl-4′-methyl-diphenyl sulfide and the like can be used in combination.

  Examples of sensitizers for photopolymerization initiators include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzyl. An amine that does not cause an addition reaction with the polymerizable component, such as an amine and 4,4′-bis (diethylamino) benzophenone, can also be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that are excellent in solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.

  Further, as the cationic ultraviolet curable adhesive, all known compositions can be used, and an epoxy resin containing a cationic polymerization type photoinitiator corresponds to this. Examples of cationic polymerization type photoinitiators include sulfonium salts, iodonium salts, and diazonium salts.

  An example of an iodonium salt is as follows. Diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate, bis (dodecylphenyl) iodonium hexafluoroantimonate Bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium hexafluorophosphate, 4-methylphenyl-4 -(1-Methylethyl) phenyliodonium hexafluoroantimo Over DOO, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrakis (pentafluorophenyl) borate, and the like.

The epoxy resin can be any of various types such as bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. It doesn't matter.
As the epoxy resin, it is preferable to use an epoxy resin having a low free chlorine and chlorine ion content so as not to damage the reflective layer. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.

  The proportion of the cationic polymerization photoinitiator per 100 parts by weight of the cationic ultraviolet curable resin is usually 0.1 to 20 parts by weight, preferably 0.2 to 5 parts by weight. In addition, in order to use the near-ultraviolet region and the visible region of the ultraviolet light source more effectively, a known photosensitizer can be used in combination. Examples of the photosensitizer at this time include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, and acetophenone.

  In addition, UV curable adhesives include, as necessary, other additives such as thermal polymerization inhibitors, antioxidants typified by hindered phenols, hindered amines, phosphites, plasticizers and epoxy silanes, mercapto. Silane coupling agents represented by silane, (meth) acrylic silane and the like can also be blended for the purpose of improving various properties. These are selected from those having excellent solubility in ultraviolet curable compounds and those that do not impair ultraviolet transparency.

(5) Second Recording Layer 405 Since the material, film forming method, and the like of the second recording layer 405 are described in substantially the same manner as the first recording layer 402, only different points will be described.
The film thickness of the second recording layer 405 is not particularly limited because it varies depending on the recording method and the like. However, in order to obtain a sufficient degree of modulation, it is usually preferably 10 nm or more, more preferably 30 nm or more. And particularly preferably 50 nm or more. However, since it is not necessary to be too thick in order to obtain an appropriate reflectance, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less.
The materials used for the first recording layer 402 and the second recording layer 405 may be the same or different.

(6) About the reflective layer 406 The reflective layer 406 needs to have a high reflectance. Moreover, it is desirable that it is highly durable.
In order to ensure high reflectivity, the thickness of the reflective layer 406 is usually preferably 20 nm or more. More preferably, it is 30 nm or more. More preferably, it is 50 nm or more. However, in order to shorten the production tact time and reduce the cost, it is preferable to be thin to some extent, and is usually 400 nm or less. More preferably, it is set to 300 nm or less.
The material, the film forming method, and the film thickness of the reflective layer 406 are the same as those of the reflective layer (1) 102 of the sticking-type two-layer optical recording medium 100 described above.

(7) Adhesive layer 407 Adhesive layer 407 preferably has a high adhesive force and a low shrinkage rate during curing and adhesion because of high shape stability of the medium.
The adhesive layer 407 is preferably made of a material that does not damage the reflective layer 406. However, a known inorganic or organic protective layer may be provided between both layers in order to suppress damage.

In the present optical recording medium 400, the film thickness of the adhesive layer 407 is usually preferably 2 μm or more. In order to obtain a predetermined adhesive strength, a certain film thickness is required. More preferably, it is 5 μm or more. However, in order to make the optical recording medium 400 as thin as possible, and there is a problem that it takes time for curing and productivity is lowered.
As the material of the adhesive layer 407, the same material as that of the transparent resin layer 404 can be used, and a pressure-sensitive double-sided tape or the like can also be used. The adhesive layer 407 can be formed by sandwiching and pressing a pressure-sensitive double-sided tape between the reflective layer 406 and the second substrate 408.

(8) About the Second Substrate 408 The second substrate 408 desirably has shape stability so that the optical recording medium 400 has a certain degree of rigidity. That is, it is preferable that mechanical stability is high and rigidity is large. Further, it is desirable that the adhesiveness with the adhesive layer 407 is high. The second substrate 408 need not be transparent. Further, the second substrate 408 may be a mirror surface substrate, and it is not necessary to form irregularities, so that transferability by injection molding is not necessarily good. Further, the second substrate 408 is not necessarily produced by the method for producing an optical disk substrate of the present invention.

  As such a material, the same material that can be used for the first substrate 401 can be used. For example, an Al alloy substrate such as an Al-Mg alloy containing Al as a main component, or an Mg alloy as a main component, for example. An Mg alloy substrate such as an Mg—Zn alloy, a substrate made of any of silicon, titanium, and ceramics, a substrate that combines them, and the like can be used.

  Polycarbonate is preferred from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoint of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.

In order to give the optical recording medium 400 sufficient rigidity, the second substrate 408 is preferably thick to some extent, and the thickness is preferably 0.3 mm or more. However, the thinner one is advantageous for thinning the recording / reproducing apparatus, and it is preferably 3 mm or less. More preferably, it is 1.5 mm or less.
The second substrate 408 may be a mirror substrate that does not have unevenness, but is preferably manufactured by injection molding from the viewpoint of ease of production.

As an example of a preferable combination of the first substrate 401 and the second substrate 408, the first substrate 401 and the second substrate 408 are made of the same material and have the same thickness. Since the rigidity is equal and balanced, it is preferable that the medium is difficult to be deformed against environmental changes. In this case, it is preferable that the degree and direction of deformation when the environment changes are the same for both substrates.
In another example of the preferable combination, the first substrate 401 is as thin as about 0.1 mm, and the second substrate 408 is as thick as about 1.1 mm. The objective lens is preferable because it easily approaches the recording layer and easily increases the recording density. At this time, the first substrate 401 may have a sheet shape.

(9) Other layers In the laminated structure, any other layers may be sandwiched as necessary. Alternatively, any other layer may be provided on the outermost surface of the medium. Specifically, as an intermediate layer between the translucent reflective layer 403 and the transparent resin layer 404, between the transparent resin layer 404 and the second recording layer 405, between the reflective layer 406 and the adhesive layer 407, etc. A buffer layer may be provided.

The buffer layer prevents the two layers from mixing and prevents compatibility. The buffer layer may also serve other functions than preventing the mixing phenomenon. Further, another intermediate layer may be interposed as required.
The material of the buffer layer needs to be incompatible with the second recording layer 405 and the transparent resin layer 404 and have light transmittance, and known inorganic and organic materials can be used. In view of characteristics, an inorganic material is preferably used. For example, (1) metal or semiconductor, (2) metal or semiconductor oxide, nitride, sulfide, oxysulfide, fluoride or carbide, or (3) amorphous carbon is used. Among them, a layer made of a dielectric having λ1 light transmittance and λ2 light transmittance and a very thin metal layer (including an alloy) are preferable.

Specifically, silicon oxide, particularly silicon dioxide, oxides such as zinc oxide, cerium oxide, yttrium oxide; sulfides such as zinc sulfide and yttrium sulfide; nitrides such as silicon nitride; silicon carbide; oxide and sulfur A mixture thereof (oxysulfide); and alloys described later are suitable. Further, a mixture of about 30:70 to 90:10 (weight ratio) of silicon oxide and zinc sulfide is also suitable. A mixture of sulfur, yttrium dioxide and zinc oxide (Y ₂ O ₂ S—ZnO) is also suitable.

Examples of the metal or alloy include silver or silver containing 0.1 to 15 atomic% of at least one element selected from the group consisting of titanium, zinc, copper, palladium, and gold. Is preferred. Further, those containing silver as a main component and containing at least one kind of rare earth element in an amount of 0.1 atomic% to 15 atomic% are also suitable. As this rare earth, neodymium, praseodymium, cerium and the like are suitable.
In addition, a resin layer may be used as long as it does not dissolve the dye in the recording layer when the buffer layer is produced. In particular, a polymer film that can be produced by vacuum deposition or CVD is useful.

  The thickness of the buffer layer is preferably 2 nm or more, more preferably 5 nm or more. If the thickness of the buffer layer is excessively thin, there is a possibility that the prevention of the above mixing phenomenon will be insufficient. However, it is preferably 2000 nm or less, more preferably 500 nm or less. If the buffer layer is excessively thick, it is not only unnecessary for preventing mixing but also may reduce light transmittance. In the case of a layer made of an inorganic material, it takes a long time to form a film, and the productivity may be lowered or the film stress may be increased. In particular, in the case of a metal, about 20 nm or less is preferable because the light transmittance is excessively lowered.

A protective layer may be provided to protect the recording layer and the reflective layer. The material for the protective layer is required to have optical transparency, but is not particularly limited as long as it protects the recording layer and the reflective layer from external force. Examples of the material of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of the inorganic substance include silicon oxide, silicon nitride, MgF ₂ and SnO ₂ .

  A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent to prepare a coating solution, and applying and drying the coating solution. The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiation with UV light. As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.

As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 μm to 100 μm, but in the present optical recording medium 400, 3 μm to 50 μm is preferable.

  Furthermore, the optical recording medium 400 can be printed on a surface that is not a recording / reproducing light incident surface as required by various printers such as ink jet and thermal transfer, or various writing tools. A layer may be provided.

  Further, as an application example of this layer configuration, a medium having three or more recording layers is also possible. Alternatively, two optical recording media 400 having this layer structure and two first recording layers 401 may be bonded to form a larger capacity medium having four recording layers.

(Reason why the stamper, mold and optical disk substrate manufacturing method of the present invention are suitably used in a multilayer optical recording medium)
Here, the reason why the stamper, the mold and the optical disk substrate manufacturing method of the present invention are suitably used in a multilayer optical recording medium will be described as a two-layer optical recording medium having two recording layers (more specifically, 2). A layer type DVD) will be described as an example.

  Usually, an optical pickup of a DVD recording / reproducing apparatus is made so as to obtain an optimum condensing spot in a single layer type optical recording medium having a substrate thickness of 0.6 mm. That is, the aberration is designed to be minimized when a recording layer separated by 0.6 mm from the substrate surface is condensed through a substrate having a thickness of 0.6 mm.

  On the other hand, in a two-layer type optical recording medium that records and reproduces from one side, the first recording layer and the second recording layer near the light incident side are recorded and reproduced by the same optical pickup. In this case, since a transparent resin layer is formed between the two recording layers, it is impossible to arrange both recording layers at a position where the aberration is minimized. Therefore, in order to reduce the deviation from the optimum position in any recording layer, the substrate thickness on the light incident side is made smaller than 0.6 mm, and as a result, a transparent resin located in the middle of both recording layers. It is necessary to design so that the aberration is minimized at the position of the layer. In this case, the first recording layer is formed at a position closer than 0.6 mm from the substrate surface, and the second recording layer is formed on the transparent resin layer having the same optical characteristics as the substrate on the substrate. It is formed at a position farther than 0.6 mm from the substrate surface. Therefore, the first recording layer is condensed through a substrate thinner than 0.6 mm, and the second recording layer is condensed through a substrate substantially thicker than 0.6 mm.

  FIG. 5C is a diagram for illustrating the influence of the substrate thickness on the jitter characteristics. The data shown in FIG. 5C was obtained as follows. That is, substrates having various thicknesses were prepared, and a single-layer type optical recording medium and a two-layer type optical recording medium in which a single layer or two recording layers were provided on each substrate were manufactured. And the jitter value in the recording layer of those optical recording media was measured, and this was plotted.

  5 is the title of the article “Compatible 8.5 Gbyte double-layer recordable DVD disc” (author names: H. C. F. Martens, W. R. Koppersa, R. J. A. van den Oetelaara, H. Woollea, P.G.P. Weijenberg, Y. Noda, M. Aga, S. Furomoto, and H. Takeshima, Journal title: Optical Data Storage Topic 4 P4. ) FIG. 4 is excerpted.

  As shown in FIG. 5C, when the jitter at that time is measured by changing the substrate thickness, the jitter becomes minimum at 0.6 mm, and the spherical aberration does not increase even if the substrate thickness is thinner than 0.6 mm or thicker. It will occur and the jitter will rise. Accordingly, in order not to deteriorate the jitter, it is necessary to form the first recording layer and the second recording layer as close as possible to 0.6 mm as described above.

  On the other hand, if the transparent resin layer is thin, the signal of the second recording layer leaks when reproducing the first recording layer, and the first recording layer is reproduced when reproducing the second recording layer. Signal leaks and the playback signal is disturbed. This is called interlayer crosstalk. FIG. 5A shows the recording / reproduction signal, and FIG. 5B shows the relationship between the signal leakage into the push-pull signal and the thickness of the transparent resin layer. From this result, the transparent resin layer needs to be thick to some extent in order to suppress interlayer crosstalk.

From these results, the DVD + R dual-layer disc standard specifies as follows.
Positions of the first recording layer and the second recording layer from the substrate surface on the light incident side: 562 μm to 632 μm
-Thickness of the transparent resin layer: 45 μm to 60 μm

  The transparent resin layer is usually formed by a spin coating method and tends to have a large variation in thickness. Specifically, the thickness of the transparent resin layer tends to vary in a standard width range of 45 μm to 60 μm. In this case, the thickness allowed for the substrate is 562 μm to 572 μm (= 632 μm-60 μm), and the width of the distribution of thickness allowed for the substrate is 10 μm.

  On the other hand, in the case of a single-layer disc, the limitation on the substrate thickness is only the spherical aberration shown in FIG. 5 (c), and the standard for the substrate thickness of DVD + R single-layer discs is 580 μm to 620 μm. The width of the thickness distribution is 40 μm.

  For the above reasons, the present invention is suitably used particularly in a two-layer type optical recording medium in which the substrate thickness needs to be controlled with high accuracy. The above description has been given by taking a two-layer type optical recording medium (more specifically, a two-layer type DVD) as an example. However, it goes without saying that the above concept can be extended to the case where the number of recording layers is three or more, or the case where an optical pickup other than a DVD (for example, an optical pickup compatible with a blue laser) is used.

Hereinafter, the present embodiment will be described more specifically based on examples. The present embodiment is not limited to the following examples.
(Preparation of stamper used for manufacturing optical disk substrate)
In the stamper manufacturing method described above, a stamper master having a nickel conductive film formed on the resist master surface on which predetermined pits / grooves were formed was prepared. After that, when depositing the nickel film by the electroforming process, a donut-shaped current distribution adjusting shielding plate is installed in the middle circumference, and the position of the current distribution adjusting shielding plate is changed to change the thickness distribution of the nickel film. Adjusted. Next, the deposited nickel film was peeled off from the glass substrate, and the resist remaining on the peeled nickel film surface was removed / washed with a solvent. Further, the back surface of the nickel film was polished and cleaned, and finally the inner and outer diameters were processed to prepare a stamper.

  The thickness of the nickel stamper used in the examples and comparative examples was measured as follows. That is, the thickness of the nickel stamper was measured in 1 mm steps from a radial position of 23 mm to 58 mm using a capacitance-type non-contact thickness measuring instrument (made by ADE Corporation, USA: 6360CD). Here, the radial positions 23 mm to 58 mm on the stamper are areas corresponding to the recording area (radial positions 23 mm to 58 mm) of the optical disk substrate.

  The above measurement was performed in each of the four radial directions, and the average value was taken as the measured value. FIG. 9 shows the radial thickness of the nickel stamper used in Example 1, Comparative Example 1, and Comparative Example 2. The vertical axis in FIG. 9 indicates the increase / decrease of the stamper thickness with respect to the reference thickness.

Example 1
The thickness of the outer peripheral portion (radius position: 58 mm) is set to the inner peripheral portion (radial position) in the fixed mold core 28 of the mold 20 used for manufacturing the optical disc substrate (hereinafter also referred to as DVD substrate) shown in FIG. : A nickel stamper approximately 6 μm larger than the thickness of 23 mm). Then, using this mold 20, a polycarbonate substrate (thickness: about 0.6 mm) made of polycarbonate resin (Mitsubishi Chemical Co., Ltd .: Novarex) is produced in a molding machine with a clamping force of 35 tons in a cycle of 4 seconds. Molded.

  The DVD substrate molded after being taken out from the mold 20 was left until it was sufficiently cooled, and then the thickness of the DVD substrate was measured with a substrate measuring machine (Doctor Schenck Co., Ltd .: substrate measuring machine MT146). As a result of the measurement, the average thickness of the DVD substrate is 4 μm (distributed between 571 μm and 575 μm), the maximum value is 2 μm (distributed between 573 μm and 575 μm), and the minimum value is 4 μm (between 569 μm and 573 μm). Distribution). Further, (the maximum value of the thickness of the optical disk substrate−the minimum value of the thickness of the optical disk substrate) was 575 μm−569 μm = 6 μm. The measurement results are shown in FIG. In FIG. 6, the horizontal axis represents the radius of the DVD substrate, and the vertical axis represents the thickness of the DVD substrate (hereinafter the same in FIGS. 7 and 8).

  From the results shown in FIG. 6, a DVD having a uniform thickness distribution can be obtained in a short cycle time of 4 seconds by using a die attached with a nickel stamper whose outer peripheral thickness is 6 μm larger than the inner peripheral thickness. It can be seen that the substrate is manufactured.

(Comparative Example 1)
A DVD substrate (thickness of about 0.1 mm) was used under the same conditions as in the example, using a nickel stamper whose outer peripheral portion (radius position: 58 mm) was approximately 2 μm thicker than the inner peripheral portion (radius position: 23 mm). 6 mm) was molded and its thickness was measured. As a result of the measurement, the average thickness of the DVD substrate is 6 μm (distributed between 570 μm and 576 μm), the maximum value is 7 μm (distributed between 571 μm and 578 μm), and the minimum value is 6 μm (between 568 μm and 574 μm). Distribution). Moreover, (the maximum value of the thickness of the optical disk substrate−the minimum value of the thickness of the optical disk substrate) was 578 μm−568 μm = 10 μm. The measurement results are shown in FIG.

  From the results shown in FIG. 7, when a mold having a nickel stamper with a difference between the outer peripheral thickness and the inner peripheral thickness of 2 μm is used, the thickness of the DVD substrate to be manufactured is as short as 4 seconds. It can be seen that the height distribution increases.

(Comparative Example 2)
A DVD substrate (thickness 0.6 mm) under the same conditions as in the example, using a nickel stamper whose outer peripheral portion (radius position: 58 mm) is approximately 9 μm thicker than the inner peripheral portion (radius position: 23 mm). ) And its thickness was measured. As a result of the measurement, the average thickness of the DVD substrate is 6 μm (distributed between 577 μm and 571 μm), the maximum value is 5 μm (distributed between 573 μm and 578 μm), and the minimum value is 9 μm (between 568 μm and 577 μm). Distribution). Moreover, (the maximum value of the thickness of the optical disk substrate−the minimum value of the thickness of the optical disk substrate) was 578 μm−568 μm = 10 μm. The measurement results are shown in FIG.

  From the results shown in FIG. 8, when using a die attached with a nickel stamper whose outer peripheral portion is thicker than the inner peripheral portion, the outer peripheral portion is made thicker by about 9 μm than the inner peripheral portion. It can be seen that a DVD substrate having a large thickness distribution is produced in a short cycle time of 4 seconds.

  In the examples and comparative examples of the present application, the examination was performed with a cycle time of 4 s. As described above, this cycle time is a number close to the lower limit in the current technology, and although the productivity is high, the stability of the process control tends to be low. For this reason, production with a cycle time of about 8 s has been conventionally performed. When a conventional optical disk substrate is manufactured using a stamper with a uniform film thickness on the inner and outer circumferences under the precondition that the cycle time is 8 s, the value of (Smax−Smin) is estimated to be about 8 μm to 10 μm from past experience. Is done.

From the above estimation and the results of Examples and Comparative Examples, it can be said that the present invention has the following characteristics.
1) When a single-layer type optical disk substrate is targeted, it is possible to satisfy the standard of the optical disk substrate film thickness in a wide range of both cycle time and stamper film thickness distribution.
2) When a two-layer type optical disk substrate (further, an optical disk substrate of a multilayer optical recording medium) is targeted, the film thickness distribution standard of the optical disk substrate is satisfied under the condition that the cycle time is shortened to improve productivity. In order to achieve this, it is advantageous to use a stamper in which the outer peripheral film thickness is made somewhat thicker than the inner periphery rather than using a stamper having a uniform film thickness.

  The stamper of the present invention is effective particularly in the case of reducing the cycle time in the multilayer optical recording medium as described above. In other words, when the single layer type medium or the cycle time is long to some extent, Therefore, it is usual to use a conventional stamper having a uniform film thickness. This is because, in order to produce a stamper with the inner and outer thickness changed, it is necessary to make a new study such as devising the shape of the shield in the electroformed layer in the electroforming process described above. This is because the production yield of the stamper itself tends to decrease. In addition, when manufacturing an optical disk substrate with a more uniform thickness distribution using such a stamper, the scope of the cycle time is limited as described above, and margins for various process conditions in actual production are limited. One of the reasons is that there is a tendency.

  As described above, the optical disk stamper to which the present embodiment is applied has a cavity thickness of an optical disk substrate mold to which the optical disk stamper is attached by making the outer peripheral part thicker than the inner peripheral part. Since the portion corresponding to the outer peripheral portion of the optical disk substrate can be thinned in advance, even if the resin in the inner peripheral portion contracts when the taken-out optical disk substrate is cooled, the thickness of the cooled optical disk substrate is reduced. It can be kept uniform. As a result, it is possible to improve the accuracy and uniformity of the thickness of the optical disk substrate while maintaining high production efficiency.

Further, when a conventional molding apparatus is used, it is efficient because it can be used without replacing other mold parts or the like only by replacing the optical disk stamper to which the present embodiment is applied.
Furthermore, since the thickness distribution of the optical disk substrate obtained by the present invention can be adjusted with higher accuracy, it can be preferably applied to a multilayer optical recording medium having two or more recording layers with a high recording density.

It is a figure for demonstrating an example of the stamper to which this Embodiment is applied. It is a figure for demonstrating an example of the metal mold | die for optical disk substrates to which this Embodiment is applied. It is a figure for demonstrating an example (adhesive type 2 layer type optical recording medium) of a multilayer type optical recording medium. It is a figure for demonstrating an example (2 layer type optical recording medium formed by 2P method) of a multilayer type optical recording medium. It is a graph which shows the measurement result of the relationship between the transparent resin layer thickness, the signal leakage noise to the recording / reproducing signal (a) and the push-pull signal (b), and the relationship between the substrate thickness and the jitter (c). 3 is a graph showing the measurement results of the thickness of a DVD substrate molded in Example 1. FIG. 6 is a graph showing the measurement results of the thickness of a DVD substrate molded in Comparative Example 1. 10 is a graph showing the measurement results of the thickness of a DVD substrate molded in Comparative Example 2. It is a figure which shows the change of the thickness of the radial direction of the nickel stampers used in Example 1, Comparative Example 1, and Comparative Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Stamper, 11 ... Base | substrate, 11a ... Surface, 12 ... Inner peripheral hole, 13 ... Inner peripheral part, 14 ... Outer peripheral part, 15 ... Innermost periphery, 16 ... Outermost periphery, 20 ... Mold, 21 ... Movable side metal mold Mold core, 22 ... Cut punch, 23 ... Outer ring, 24 ... Outer ring stopper, 25 ... Stamper, 26 ... Sprue bush, 27 ... Fixed side stamper inner circumference press, 28 ... Fixed side mold core, 29 ... Cavity, 30 DESCRIPTION OF SYMBOLS ... Resin flow path, 31 ... Extrusion pin, 100, 400 ... Optical recording medium, 101 ... Substrate (1), 102 ... Reflective layer (1), 103 ... Recording layer (1), 104 ... Intermediate layer, 105 ... Transparent resin Layer 106, protective coating layer 107, reflective layer (2), 108 recording layer (2), 109 substrate (2), 110 laser light, 111 reverse layered body, 112 forward laminated body, 401 ... First substrate, 402 ... first recording layer 403 ... semi-transparent reflective layer, 404 ... transparent resin layer, 405 ... second recording layer, 406 ... reflective layer, 407 ... adhesive layer, 408 ... second substrate, 411, 412 ... recording track

Claims (7)

An annular stamper for manufacturing an optical disk substrate,
The optical disk substrate is an optical disk substrate for a multilayer optical recording medium having a plurality of recording layers,
The difference (Smax−Smin) between the maximum value (Smax) and the minimum value (Smin) of the substrate thickness in the recording area of the optical disk substrate is less than 10 μm.
The stamper is characterized in that the thickness of the outer peripheral portion is larger than the thickness of the inner peripheral portion of the stamper.   The stamper according to claim 1, wherein a difference between the thickness of the outer peripheral portion and the thickness of the inner peripheral portion of the stamper is 5 µm or more.   3. The stamper according to claim 1, wherein a thickness of the stamper increases from the inner peripheral portion to the outer peripheral portion. 4. A mold for molding an annular resin optical disk substrate,
The optical disk substrate is an optical disk substrate for a multilayer optical recording medium having a plurality of recording layers,
A fixed mold core,
An outer ring for forming an outer peripheral edge of the optical disc substrate;
A movable mold core disposed to face the fixed mold core via the outer ring;
A stamper attached to a mold surface of the fixed mold core or the movable mold core,
The stamper is arranged so that a difference (Smax−Smin) between the maximum value (Smax) and the minimum value (Smin) of the substrate thickness in the recording area of the optical disk substrate is less than 10 μm. A mold characterized in that the outer peripheral portion is thicker than the thickness.   The mold according to claim 4, wherein a difference between the thickness of the outer peripheral portion of the stamper and the thickness of the inner peripheral portion is 5 μm or more. A method of manufacturing an optical disk substrate using a mold having a stamper attached to a mold surface of a fixed mold core or a movable mold core,
The stamper is an optical disk substrate for a multilayer optical recording medium in which the optical disk substrate has a plurality of recording layers, and the maximum value (Smax) and the minimum value (Smin) of the thickness of the substrate in the recording area of the optical disk substrate A method of manufacturing an optical disc substrate, wherein the outer peripheral portion is thicker than the inner peripheral portion of the stamper so that the difference (Smax−Smin) is less than 10 μm.   7. The method of manufacturing an optical disk substrate according to claim 6, wherein a difference between the thickness of the outer peripheral portion of the stamper and the thickness of the inner peripheral portion is 5 μm or more.

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