JP2013149337A - Method of manufacturing optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical recording medium having plural intermediate layers, which can efficiently manufacture an optical recording medium having excellent recording reproduction characteristics with few defects.SOLUTION: A method of manufacturing an optical recording medium having three or more recording layers and plural intermediate layers disposed between the recording layers, made of a radiation-curable resin material and having an uneven shape, includes a step of forming the plural intermediate layers using plural stampers having, on its surface, an uneven shape for transfer corresponding to the uneven shape of the intermediate layers. The plural stampers have annular minute protrusions concentric with the center of each of the plural stampers, on the surface having the uneven shape for transfer. The radial position of a minute protrusion 205 on one stamper 204 of the plural stampers used for forming at least one of the plural intermediate layers differs from the radial position of a minute protrusion 208 on another stamper 207 of the plural stampers used for forming another intermediate layer of the plural intermediate layers.

Description

  The present invention relates to a method for manufacturing an optical recording medium. More specifically, the present invention relates to a method for manufacturing an optical recording medium having a plurality of intermediate layers.

  In general, an optical recording medium such as a CD or a DVD has a predetermined fine uneven pattern on the surface, and these uneven patterns usually use a stamper having a predetermined uneven pattern. Alternatively, it is formed by transferring to an intermediate layer.

  Here, in general, a disk master having a predetermined uneven shape is first prepared, and a stamper is manufactured by transferring the uneven pattern from the disk master. Furthermore, mass production of optical recording media is performed by using this stamper to form a substrate for optical recording media by injection molding or the like. In addition, after forming a recording / reproducing functional layer such as a recording layer on the substrate thus produced, an intermediate layer is formed using a transparent resin material or the like, and a concavo-convex shape is transferred to the intermediate layer using a transparent stamper ( Photopolymerization method (Photo Polymerization: hereinafter sometimes referred to as “2P method”)), and a recording / reproducing functional layer further laminated thereon to form a laminated optical recording medium having two recording layers Has also been made (for example, Patent Document 1).

  In the 2P method, the transparent resin material is generally applied onto a substrate by spin coating to form an intermediate layer. At this time, in order to control the thickness of the intermediate layer in the vicinity of the center hole of the optical recording medium, a technique for blocking the resin material by providing an annular protrusion in the vicinity of the center hole on the substrate has been proposed (patent) Reference 2). This technique is promising particularly in a Blu-ray disc in which a cover layer is formed on the outermost surface in that the inner circumferential end of the intermediate layer can be formed in a substantially circular shape. Because the cover layer is the same as the middle layer. It is common to apply and form a transparent resin material by spin coating. At this time, if the end of the inner peripheral side of the intermediate layer is disturbed, the cover layer material is uniformly stretched over the entire surface of the optical recording medium. This is because bubbles and the like are easily mixed into the cover layer and the uniformity of the optical characteristics of the cover layer is impaired.

  The purpose of producing the laminated optical recording medium is to increase the recording capacity per optical recording medium by providing a plurality of recording layers, and it is also used in Blu-ray discs capable of higher density recording. Blu-ray discs having two recording layers have already been put into practical use. In addition, an optical recording medium having three or more recording layers has been actively developed for realizing a higher capacity recording medium.

  In the manufacture of an optical recording medium having three recording layers, the recording / reproducing functional layer and the intermediate layer are sequentially formed on the substrate by repeating the intermediate layer forming step by the 2P method described above once more. Is common. That is, in an optical recording medium having N or more layers, an intermediate layer of N-1 layers is formed by repeating the 2P method N-1 times.

JP 2007-164967 A JP 2007-115317 A

  However, when manufacturing an optical recording medium having two or more intermediate layers, it is difficult to manufacture an optical recording medium with a high yield by simply repeating the same process. It has become clear. For example, assuming that two intermediate layers are formed by the method described in Patent Document 2, the intermediate layer formed first uses an annular protrusion on the substrate in the vicinity of the central hole, It is possible to control the thickness of the intermediate layer, but when the second intermediate layer is formed, there is a protrusion that blocks the resin material because this protrusion is already integrated with the first intermediate layer. However, the film thickness uniformity of the intermediate layer in the vicinity of the center hole is deteriorated, and the end on the inner peripheral side is likely to be disturbed. As a result, when the intermediate layer is formed, there is a tendency that a stamper peeling failure occurs or it is difficult to form a uniform intermediate layer. Furthermore, an air recording medium having sufficient recording / reproduction characteristics with few defects is produced by bubbles entering the cover layer formed on the outermost surface of the optical recording medium or by disturbing the film thickness distribution. It becomes difficult. Accordingly, in the production of an optical recording medium having two or more intermediate layers, a more efficient production method is required.

  The present invention has been made in order to solve the above-described problem, and in an optical recording medium manufacturing method having a plurality of intermediate layers, an optical recording medium having excellent recording and reproducing characteristics with few defects is efficiently manufactured. Objective.

  The gist of the present invention is that there are three or more recording layers on a disc-shaped substrate having a central hole, and a plurality of intermediate layers having a concavo-convex shape made of a radiation curable resin raw material interposed between the recording layers. A method for producing an optical recording medium comprising: a plurality of intermediate layers using a plurality of stampers having a disk-like shape and having a concavo-convex shape for transfer corresponding to the concavo-convex shape on a surface thereof. In the forming step, the plurality of stampers have annular minute protrusions concentric with the center of each of the plurality of stampers on the surface having the uneven shape for transfer, and at least one of the plurality of intermediate layers. Among the plurality of stampers used when forming one intermediate layer, the radial position of the minute protrusion on one stamper is the same as that on the other stamper among the plurality of stampers used when forming another intermediate layer. Radius position of minute protrusion It is different consists in a method of manufacturing an optical recording medium characterized.

At this time, it is preferable that the plurality of stampers have a center hole and have the minute protrusions in the vicinity of the center hole.
In the step of forming one intermediate layer of the plurality of intermediate layers, the surface of the stamper having one of the plurality of stampers and the substrate are opposed to each other, and one of the plurality of stampers. Filling the gap between the two stampers and the substrate with the radiation curable resin material, stretching the radiation curable resin material, and irradiating radiation to cure the radiation curable resin material. One stamper of the plurality of stampers is disposed in a region from the center hole of the substrate to the inner diameter of the clamp area when one of the plurality of stampers is opposed to the substrate. It is preferable that the microprotrusions above are formed.

  In addition, the radial position of the minute protrusion on one stamper among the plurality of stampers used when forming the intermediate layer that is stacked first among the plurality of intermediate layers is an intermediate layer that is stacked after the plurality of intermediate layers. Of the plurality of stampers used when forming the layer, it is preferable to be on the outer peripheral side with respect to the minute protrusions on the other stampers.

  In addition, the radial position of the minute protrusion on one stamper among the plurality of stampers used when forming the intermediate layer that is stacked first among the plurality of intermediate layers is an intermediate layer that is stacked after the plurality of intermediate layers. Of the plurality of stampers used when forming the layer, it is preferable that they are located on the inner peripheral side with respect to the minute protrusions on the other stampers.

  In addition, the substrate has annular minute protrusions concentric with the center of the substrate on a surface on which the plurality of intermediate layers are formed, and the minute protrusions on the substrate are formed on the plurality of intermediate layers. Among them, it is preferable that the plurality of stampers used for forming the last laminated intermediate layer are present at substantially the same radial position as the minute protrusions on one stamper.

Moreover, it is preferable that the minute protrusions formed on the substrate are intermittently formed in the circumferential direction.
Moreover, it is preferable that the micro protrusions formed on the plurality of stampers are intermittently formed in the circumferential direction.

  According to the present invention, it is possible to realize an intermediate layer and a cover layer with few defects and excellent uniformity in an optical recording medium having two or more intermediate layers.

It is typical sectional drawing for demonstrating the manufacturing method of the optical recording medium of this invention. It is typical sectional drawing of the center hole vicinity of the optical recording medium containing a microprotrusion which showed the process of the manufacturing method of this invention. FIG. 10 is a schematic cross-sectional view in the vicinity of the center hole of an optical recording medium including minute protrusions, showing the steps of a conventional manufacturing method.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

A. Preferred Embodiment of Manufacturing Method of Optical Recording Medium of the Present Invention FIG. 1 is a diagram for explaining a preferred example of a manufacturing method of an optical recording medium of the present invention. FIG. 1 shows a method for producing a single-sided incident type optical recording medium (three-layer BD-R) having three recording layers containing an organic dye as an example of a method for producing a multilayer multilayer optical recording medium. Yes. In FIG. 1, for convenience, only a partial cross section of the recording area of the optical recording medium is enlarged.

  A single-sided three-layer optical recording medium 100 represented by the single-sided three-layer BD-R shown in FIG. 1 includes a disc-shaped substrate 101 having a central hole, a first recording / reproducing functional layer 102, radiation A light transmissive first intermediate layer 103 made of a curable resin material, a second recording / reproducing functional layer 104, a light transmissive second intermediate layer 105 made of a radiation curable resin material, and a third recording / reproducing functional layer. 106 and a light-transmitting cover layer 107 are stacked in order. Concavities and convexities are formed on the substrate 101, the first intermediate layer 103, and the second intermediate layer 105, respectively, and constitute recording tracks. Optical information recording / reproduction of the optical recording medium 100 that is a single-sided three-layer BD-R is performed from the cover layer 107 side to the first recording / reproducing functional layer 102, the second recording / reproducing functional layer 104, and the third recording / reproducing functional layer 106. This is performed by the irradiated laser beam 123.

  In the embodiment of the present invention, “light transmission” means recording / reproducing optical information on the first recording / reproducing functional layer 102, the second recording / reproducing functional layer 104, and the third recording / reproducing functional layer 106. It means the light transmittance with respect to the wavelength of the light (laser beam 123) irradiated on the surface. Specifically, the light wavelength for recording / reproduction is usually 30% or more, preferably 50% or more, more preferably 60% or more. On the other hand, the upper limit of the transmittance with respect to the wavelength of light for recording / reproduction is ideally 100%, but usually it is a value of 99.9% or less.

  In the embodiment of the present invention, the “recording / reproducing functional layer” is defined as follows. In order to record information on an optical recording medium, it is essential to have a recording layer containing a material whose optical characteristics change as a result of light irradiation, such as a dye material or a phase change material. Further, for one recording layer (including a case where two or more layers in which different materials are laminated includes a case where it can be regarded as one recording layer functionally, the same applies to the following description). In order to assist recording, a form in which a layer having various auxiliary functions such as a reflective layer and a protective layer is further laminated is common. In the present invention, the entire various layers having the auxiliary function including one recording layer are referred to as “recording / reproducing functional layer”.

  Here, the present invention has three or more recording / reproducing functional layers on a disc-shaped substrate having a central hole, and a concavo-convex shape made of a radiation curable resin material interposed between these recording / reproducing functional layers. The present invention relates to a method of manufacturing an optical recording medium having a plurality of intermediate layers, and is characterized by the shape of the substrate and the shapes of the plurality of stampers used to form the plurality of intermediate layers. The plurality of stampers have a disk shape having a central hole like the substrate, and have a transfer convex shape corresponding to the uneven shape of the plurality of intermediate layers on the surface. Further, the plurality of stampers have annular micro-projections concentric with the centers of the plurality of stampers (hereinafter also referred to as stamper centers) on the surface having the concavo-convex shape for transfer, and the plurality of intermediate layers Among the plurality of stampers used when forming the other intermediate layer among the plurality of intermediate layers, the radial position of the minute protrusion on one stamper among the plurality of stampers used when forming at least one intermediate layer among the plurality of stampers This is different from the radial position of the minute protrusion on the stamper.

  By attaching a stamper on a substrate via a radiation curable resin raw material, curing the radiation curable resin raw material by irradiation to form an intermediate layer to which the concavo-convex shape was transferred, and then peeling the stamper, It is possible to realize an intermediate layer having a desired uneven shape.

  In the embodiment of the present invention, the material and manufacturing method of each layer excluding the substrate shape and the stamper shape are not particularly limited, and can be appropriately formed by a conventionally known technique.

  For example, as shown in FIG. 1 (a), a substrate 101 having grooves, lands, and pre-pits formed on its surface is formed by injection molding using a nickel stamper or the like using a polycarbonate resin as a raw material. can do. For the first recording / reproducing functional layer 102, when the recording layer contains an organic dye, a coating solution containing the organic dye is applied to the surface of the substrate 101 having the unevenness by spin coating or the like, and then applied. The recording layer can be formed by heating to remove the solvent used in the liquid. Further, after forming the recording layer, the reflective layer can be formed on the recording layer by sputtering or vapor-depositing an Ag alloy or the like, for example. When the recording layer is an inorganic material such as a phase change material, it can be formed by sputtering or vapor deposition as in the case of the reflective layer. The same applies to a protective layer made of a dielectric material or the like.

  After realizing the state in which the first recording / reproducing functional layer 102 is formed on the substrate 101 (hereinafter referred to as the data substrate 111) (FIG. 1A), the first intermediate layer 103 is formed by the 2P method.

  The method for forming the first intermediate layer 103 is as follows. First, the first radiation curable resin material 103a, which is the material of the first intermediate layer 103, is applied on the first recording / reproducing functional layer 102 of the data substrate 111 (FIG. 1B). Furthermore, the 1st stamper 112 is bonded together to the apply | coated 1st radiation curable resin raw material 103a, the radiation 121 is irradiated, and the 1st radiation curable resin raw material 103a is hardened (FIG.1 (c)). Thereafter, the first stamper 112 is peeled off to form the first intermediate layer 103 having a desired uneven shape. Here, when the first stamper 112 is a radiation transmissive stamper made of a radiation transmissive material, the first radiation curable resin material 103a may be cured by irradiating radiation from the first stamper 112 side, When the first recording / reproducing functional layer is not deteriorated by radiation irradiation and has sufficient radiation transparency, a metal stamper or the like may be used as the first stamper 112 and radiation may be irradiated from the data substrate 111 side.

  At this time, since it is desired to form the first intermediate layer 103 with a uniform film thickness on the data substrate 111, various methods are used. For example, after the first radiation curable resin material 103a is dropped on the inner peripheral portion of the data substrate 111, the data substrate 111 is rotated at a high speed, thereby extending the first radiation curable resin material 103a to obtain a uniform first intermediate It is common to form layer 103. Further, a gap dispensing method is also used in which the data substrate 111 and the first stamper 112 are opposed to each other, the first radiation curable resin material 103a is injected into the gap, and the stretching of the first radiation curable resin material 103a is promoted by capillary action. be able to.

  Here, the case where the first intermediate layer 103 is made of a single first radiation curable resin material 103a has been described, but the first intermediate layer 103 is a laminated structure made of two or more types of radiation curable resin materials. You may have. For example, a first transfer layer radiation curable resin raw material 103b (not shown) having a more excellent concavo-convex shape transferability is prepared, and before the first radiation curable resin raw material 103a coating and forming step, the first The stamper 112 is coated and stretched on the uneven surface of the stamper 112, and the radiation-curable resin raw material 103 b for the first transfer layer is cured by irradiation with radiation, and the first stamper 112 has the uneven surface for the first transfer layer. The formation method of the first radiation curable resin material 103a described above may be performed in a state in which a layer (hereinafter sometimes referred to as a transfer layer) formed by curing the radiation curable resin material 103b is formed. The same applies to the second intermediate layer 105.

  Next, after the step of forming the first intermediate layer 103, the second recording / reproducing functional layer 104 is formed on the first intermediate layer 103 in the same manner as the first recording / reproducing functional layer 102 (FIG. 1D). At this time, the layer configuration of the second recording / reproducing functional layer 104 may be the same as that of the first recording / reproducing functional layer 102, but usually different materials and layer configurations are applied.

  Next, after the step of forming the second recording / reproducing functional layer 104, the second radiation curable resin material 105 a is applied onto the second recording / reproducing functional layer 104 in the same manner as the first intermediate layer 103, and the second stamper is applied. The second intermediate layer 105 is formed by performing bonding of 113 and radiation 122 (FIGS. 1E and 1F). At this time, the material of the second intermediate layer 105, that is, the second radiation curable resin material 105a may be the same as the first radiation curable resin material 103a, but a different material may be used. Similarly to the first intermediate layer 103, a radiation curable resin material 105b (not shown) having a more concavo-convex shape and excellent transferability may be used as the transfer layer.

  Further, after the step of forming the second intermediate layer 105, the third recording / reproducing functional layer 106 is formed on the second intermediate layer 105 in the same manner as the first recording / reproducing functional layer 102 and the second recording / reproducing functional layer 104. At this time, the layer configuration of the third recording / reproducing functional layer 106 may be the same as that of the first recording / reproducing functional layer 102 or the second recording / reproducing functional layer 104, but usually different materials and layer configurations are applied. .

Further, the cover layer 107 is formed by applying a radiation curable resin material or the like on the third recording / reproducing functional layer by spin coating and curing by radiation irradiation (FIG. 1 (g)).
By performing the above procedure, the optical recording medium 100 can be completed.

  The feature of the present invention is that in the production of the optical recording medium having the plurality of intermediate layers, the formation state in the vicinity of the inner peripheral edge of the intermediate layer is controlled. Hereinafter, taking the case of an optical recording medium having two intermediate layers as an example, a manufacturing method including an intermediate layer forming step will be described in detail with reference to FIGS.

  2 and 3, the center hole 203 of the substrate in a state where the stamper is bonded to the state in which the first recording / reproducing functional layers 211 and 311 are formed on the substrates 201 and 301 (hereinafter referred to as a data substrate). , 303 is a cross-sectional view of the vicinity. 2 and 3, the right side in the figure is the center hole side of the optical recording medium, and the left side in the figure is the outer peripheral side of the optical recording medium.

  In FIG. 2, an annular shape concentric with the center of the substrate (hereinafter also referred to as the substrate center) is formed on the surface of the substrate 201 in the vicinity of the center hole 203 of the substrate 201 and facing the stamper when the optical recording medium is manufactured. A minute protrusion 202 is provided. Also, annular minute projections 205 and 208 concentric with the stamper center are provided on the surface of the stamper 204 and 207 near the center holes 206 and 209 and on the surface of the stamper facing the substrate when the optical recording medium is manufactured. It has been.

  In FIG. 3, an annular minute protrusion 302 concentric with the center of the substrate is provided on the surface of the substrate 301 in the vicinity of the center hole 303 and facing the stamper when the optical recording medium is manufactured. In addition, annular minute projections 305 and 308 concentric with the center of the stamper are provided on the surface of the stamper 304 and 307 near the center holes 306 and 309 and on the surface of the stamper facing the substrate when the optical recording medium is manufactured. It has been.

Hereinafter, an example of the prior art will be described in detail with reference to FIG.
FIGS. 3A to 3D also show a step of forming a first intermediate layer (first intermediate layer) formed on the substrate (first intermediate layer forming step). FIGS. 3E to 3H also show a second intermediate layer (second intermediate layer) forming step (second intermediate layer forming step) formed on the substrate.

  First, the surface of the substrate 301 provided with the first recording / reproducing functional layer 311 is provided with the surface provided with the fine protrusions 302 of the first stamper 304 provided with the transfer layer 312 in advance. FIG. 3 (a)). Here, the minute protrusions 305 on the first stamper and the minute protrusions 302 on the substrate are provided at substantially the same radial position.

  Next, the gap between the substrate 301 and the first stamper 304 is filled with the first radiation curable resin raw material 313a by the gap dispensing method, and the substrate 301 and the first stamper 304 are rotated at a low speed or a load is applied. Etc., the first radiation curable resin raw material 313a is stretched to some extent over the entire substrate surface (FIG. 3B).

Furthermore, vacuum suction is performed from the inner peripheral side, and after forming the first radiation curable resin raw material 313a to a desired radial position by blocking with the microprojections 302 on the substrate and the microprojections 305 on the first stamper, The substrate 301 and the first stamper 304 are simultaneously rotated at a high speed to extend the first radiation curable resin material 313a to the outer periphery of the substrate, and then the radiation 331 is irradiated to cure the first radiation curable resin material 313a (FIG. 3 (c)). Here, since the minute protrusion 305 on the first stamper and the minute protrusion 302 on the substrate are provided at substantially the same radial position, the first radiation curable resin material 313a can be sufficiently blocked, and the first Disturbance of the inner peripheral side end 321 of the intermediate layer 313 hardly occurs.
Next, the first stamper 304 is peeled from the substrate 301 to complete the formation of the first intermediate layer 313 on the substrate (FIG. 3D).

  FIGS. 3A to 3D show the intermediate layer forming step in the case of an optical recording medium having one intermediate layer, and no particular problem arises when only one intermediate layer is formed. .

  Thereafter, a second recording / reproducing functional layer 314 is formed on the first intermediate layer, and the surface of the substrate 301 on which the second recording / reproducing functional layer 314 is formed is provided with the fine protrusions 302 as in FIG. Then, the surface of the second stamper 307 provided with the transfer layer 315 in advance is opposed to the surface provided with the fine protrusions 308 (FIG. 3E).

  Next, as in FIG. 3B, the gap between the substrate 301 and the second stamper 307 is filled with the second radiation curable resin material 316a by the gap dispensing method, and the second radiation curable resin material 316a is filled on the inner peripheral side. To some extent (FIG. 3 (f)).

  Then, similarly to FIG. 3C, vacuum suction is performed from the inner peripheral side, and the second radiation curable resin material 316a is formed to a desired radial position by blocking with the fine protrusions 308 on the second stamper. After that, the substrate 301 and the second stamper 307 are simultaneously rotated at high speed, the second radiation curable resin material is stretched to the outer periphery of the substrate, and then the radiation 332 is irradiated to cure the second radiation curable resin material 316a ( FIG. 3 (g)).

  However, at this time, since the minute protrusions 302 on the substrate are integrated with the first intermediate layer 313, only the minute protrusions 308 on the second stamper have a small blocking effect, and the first intermediate layer 313 Since the second radiation curable resin raw material 316a is stretched to the vicinity of the formed step, the second radiation curable resin raw material 316a is partially formed on the second stamper as shown in FIG. It tends to leak into the inner peripheral side of the radial position of the protrusion 308.

  Thereafter, as in FIG. 3D, the second stamper 307 is peeled off from the substrate 301 to complete the formation of the second intermediate layer 316 on the substrate. However, due to the partial leakage of the resin material, Since the bonding state between the substrate 301 and the second stamper 307 is not uniform, there is a strong tendency to cause a disorder such as a part of the resin material remaining on the inner peripheral side end 322 of the second intermediate layer on the substrate after peeling. (FIG. 3 (h)), and in some cases, peeling may be impossible.

  Further, after that, the third recording / reproducing functional layer is formed on the second intermediate layer, and the cover layer is further formed by spin coating or the like, whereby the optical recording medium is completed. Disturbance of the peripheral end 322 also adversely affects the application state of the cover layer, causes non-uniform film thickness of the cover layer, and may generate bubbles in the cover layer.

  In contrast, the most preferred basic process of the present invention is illustrated by FIG. That is, the position of the minute protrusion 205 on the first stamper for forming the first intermediate layer 213 is provided on the outer peripheral side with respect to the position of the minute protrusion 208 on the second stamper for forming the second intermediate layer 216. This is the difference from the prior art (FIG. 3). As shown in FIG. 2, when the data substrate and the first stamper 204 are bonded to form the first intermediate layer 213, the position of the minute protrusion is shifted, and the minute protrusion 205 on the first stamper is more Present on the outer periphery. Therefore, the formation position of the inner peripheral side end 221 of the first intermediate layer is determined by the position of the minute protrusion 205 on the first stamper, and is located away from the minute protrusion 202 on the substrate.

  Next, when the second intermediate layer 216 is formed, the second stamper 207 provided with the minute protrusions 208 on the inner peripheral side of the first stamper 204 is used. By doing so, the inner peripheral end 222 of the second intermediate layer can be formed with less disturbance. At this time, it is preferable to use a substrate in which the minute protrusions 202 are provided at the same radial position as the minute protrusions 208 on the second stamper because the effect of blocking the radiation curable resin material is further strengthened.

  When the radiation curable resin raw material is blocked by only the minute protrusions 205 on the first stamper as shown in FIG. 2C, the inner peripheral side end 221 of the first intermediate layer has the same radial position on the substrate. However, the inner peripheral side end 221 of the first intermediate layer is completely covered by the second intermediate layer 216, although the inner peripheral side end tends to be slightly disturbed. Therefore, there is a low possibility that the second intermediate layer or the outermost cover layer is adversely affected.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIG. Here, a method for producing an optical recording medium having three recording / reproducing functional layers and two intermediate layers will be described in detail. Each of the intermediate layers is for a two-layer structure in which a transfer layer is provided in advance on a stamper.

2A to 2D also show a step of forming a first intermediate layer (first intermediate layer) formed on the substrate (first intermediate layer forming step). FIGS. 3E to 3H also show a second intermediate layer (second intermediate layer) forming step (second intermediate layer forming step) formed on the substrate.
The first intermediate layer forming step in FIGS. 2A to 2D is substantially the same as in FIG.

  First, the surface of the substrate 201 provided with the first recording / reproducing functional layer 211 provided with the fine protrusions 202 and the surface provided with the fine protrusions 205 of the first stamper 204 provided with the transfer layer 212 in advance are opposed to each other ( FIG. 2 (a)). Here, the minute protrusion 205 on the first stamper is provided at a radial position on the outer peripheral side of the minute protrusion 202 on the substrate.

  Next, the gap between the substrate 201 and the first stamper 204 is filled with the first radiation curable resin raw material 213a by the gap dispensing method, and the substrate 201 and the first stamper 204 are rotated at a low speed or a load is applied. Etc., the first radiation curable resin raw material 213a is stretched to some extent over the entire substrate surface (FIG. 2B).

Further, vacuum suction is performed from the inner peripheral side, and the first radiation curable resin raw material 213a is blocked by the first protrusions on the first stamper 205 to form a desired radial position, and then the substrate 201 and the first stamper 204 are formed. Are simultaneously rotated at a high speed to extend the first radiation curable resin material to the outer periphery of the substrate, and then the radiation 231 is irradiated to cure the first radiation curable resin material 213a (FIG. 2C). Here, the resin material is blocked only by the minute protrusions 205 on the first stamper. At this time, before the substrate 201 and the first stamper 204 are rotated at high speed, if only the vicinity of the inner peripheral portion is first cured by radiation using a mask or the like, bubbles are mixed from the inner peripheral side during high-speed rotation. Since it can suppress that, it is preferable.
Next, the first stamper 204 is peeled off from the substrate 201 to complete the formation of the first intermediate layer 213 on the substrate (FIG. 2D).

  After that, the second recording / reproducing functional layer 214 is formed on the first intermediate layer 213, and the surface on which the minute projections 202 of the substrate 201 on which the second recording / reproducing functional layer 214 is formed is provided as in FIG. And the surface of the second stamper 207 provided with the transfer layer 215 in advance with the surface provided with the fine protrusions 208 (FIG. 2E).

  Next, as in FIG. 2B, the gap between the substrate 201 and the second stamper 207 is filled with the second radiation curable resin raw material 216a by the gap dispensing method, and the substrate 201 and the second stamper 207 are twisted at a low speed. By rotating or applying a load, the second radiation curable resin material 216a is stretched to some extent over the entire substrate surface (FIG. 2 (f)).

  Then, similarly to FIG. 2C, vacuum suction is performed from the inner peripheral side, and the second radiation curable resin raw material 216a is blocked by the micro protrusions 202 on the substrate and the micro protrusions 208 on the second stamper. After forming to a desired radius position, the substrate 201 and the second stamper 207 are simultaneously rotated at a high speed, the second radiation curable resin material 216a is stretched to the outer periphery of the substrate, and then the radiation 232 is irradiated to perform the second radiation curing. The functional resin material 216a is cured (FIG. 2 (g)). At this time, the minute projections 202 on the substrate are present at substantially the same radial position as the minute projections 208 on the second stamper, so that the second radiation curable resin material 216a can be more reliably blocked. Become. Therefore, the inner end 222 of the second intermediate layer is unlikely to be disturbed as shown in FIG. 3G, and it is possible to reduce the probability of occurrence of defective peeling or defective cover layer formation.

Further, as in FIG. 2D, the second stamper 207 is peeled from the substrate 201, and the formation of the second intermediate layer 216 on the substrate is completed (FIG. 2H).
Thereafter, the third recording / reproducing functional layer is formed on the second intermediate layer, and the cover layer is formed by spin coating or the like, thereby completing the optical recording medium.

  As described above, the characteristics of the present invention have been described with respect to the case of the optical recording medium having two intermediate layers with reference to FIG. 2. However, the present invention is also effective for an optical recording medium having three or more intermediate layers. is there. That is, the minute protrusion on the stamper used when forming the intermediate layer that is laminated first among the plurality of intermediate layers is smaller than the minute protrusion on the other stamper used when forming the intermediate layer that is laminated later among the plurality of intermediate layers. Also, it is important that the intermediate layer and the cover layer are less likely to be disturbed at the inner peripheral side end portion of the intermediate layer, have fewer defects, and have excellent uniformity. It becomes possible. More preferably, the microprotrusions on the substrate are present at substantially the same radial position as the microprotrusions on the stamper used for forming the last intermediate layer of the plurality of intermediate layers. By doing in this way, the blocking effect of the radiation curable resin raw material in the inner peripheral part of the intermediate | middle layer laminated | stacked last becomes more effective.

  In FIG. 2, the minute protrusions on the stamper used when forming the intermediate layer that is laminated first among the plurality of intermediate layers are replaced with other stampers used when forming the intermediate layer that is laminated later among the plurality of intermediate layers. Although the aspect located on the outer peripheral side with respect to the upper microprotrusions has been described, conversely, the microprotrusions on the stamper used when forming the intermediate layer to be laminated first among the plurality of intermediate layers include the plurality of intermediate layers. Of these, an embodiment is also preferable (not shown) that is located on the inner peripheral side with respect to the minute protrusions on the other stamper used when forming the intermediate layer to be laminated later. By adopting such an aspect, the formation position of the inner peripheral side end portion of the intermediate layer to be laminated later is away from the vicinity of the step formed by the intermediate layer to be laminated first. This is because it is difficult for the radiation curable resin material to leak into the side.

  That is, in the present invention, the radial position of the minute protrusion on the stamper used when forming at least one intermediate layer among the plurality of intermediate layers is the same as the minute position on the other stamper used when forming another intermediate layer among the plurality of intermediate layers. It can be said that it is important to be different from the radial position of the protrusion.

(About minute protrusions)
Hereinafter, the present invention will be described in detail with a focus on minute protrusions.
The substrate used in the present invention has a disk shape having a central hole, but generally, an information recording area in which information is recorded is not provided on the entire surface of the substrate. At the time of recording / reproducing of the optical recording medium, a clamp area for fixing the substrate is set on the inner peripheral side of the optical recording medium in order to fix the optical recording medium by passing the center hole through the spindle. Since this clamp area is required to be substantially flat, it is not possible to form the microprojections of the present invention. That is, in the present invention, the vicinity of the center hole where the minute projections on the substrate are formed refers to a region from the center hole of the substrate to the inner diameter of the clamp area. Taking the case of a Blu-ray disc as an example, the center hole has a radius of 7.5 mm, and the clamp area is set to a radius of 11.5 mm to 16.5 mm. The radial position is preferably a region having a radius of 7.5 to 11.5 mm. The same applies to the minute protrusions on the stamper. In the intermediate layer forming step, when the surface of the stamper having the microprotrusions and the surface of the substrate having microprotrusions face each other, the microprotrusions on the stamper are formed in the region from the center hole of the substrate to the inner diameter of the clamp area. Preferably it is formed. The radius position where the microprotrusions are formed is preferably a radius of 10.0 mm to 11.0 mm for both the substrate and the stamper.

  The minute protrusions on the substrate and the stamper are formed in an annular shape in the vicinity of the respective center holes, but may not be completely continuous but may be formed intermittently. It may be partially discontinuous as long as the function of blocking the radiation curable resin raw material is exhibited. Rather, it is preferable to form the microprotrusions intermittently in order to enhance the vacuum suction effect from the center hole.

  There is no particular limitation on the radial cross-sectional shape of the minute protrusions on the substrate and the stamper, and a square shape, a trapezoidal shape, a triangular shape, a semicircular shape, or the like is used. Although the maximum width in the radial cross section of the microprotrusions can be selected as appropriate in terms of manufacturing convenience, it is usually about 0.05 mm to 1.0 mm. The height of the minute protrusions from the substrate surface or stamper surface is preferably 5 μm or more, more preferably 10 μm or more, although it depends on the thickness of the intermediate layer to be obtained. If it is lower than this, the blocking effect of the radiation curable resin material may not be sufficient. Further, the upper limit of the height of the fine protrusion is preferably lower than the thickness of the intermediate layer to be obtained, and is usually 70 μm or less, preferably 50 μm or less, and more preferably 30 μm or less.

  Here, the heights of the minute protrusions on the substrate and the stamper do not need to be uniform over the entire circumference. There may be some variation in the height, or it may be an intermittent shape in the circumferential direction in which there is a region where there is no microprojection partially. This is because the blocking effect of the radiation curable resin functions sufficiently even in such a non-uniform state. In addition, such a non-uniform state is rather preferable because the reduced pressure suction effect from the inner peripheral side becomes higher.

  When the minute protrusions are intermittently formed, the minute protrusions may be partially removed, but it is desirable to partially reduce the height of the minute protrusions. In the case of complete removal, the length in the circumferential direction of the region where the effect of blocking the microprotrusions cannot be sufficiently obtained is 1.0 mm or less, although it depends on the viscosity of the material used. It is preferable to set the degree. This is because the possibility that the radiation curable resin raw material leaks to the inner peripheral side from the radial position of the fine protrusions is reduced at this level.

  The thickness of the intermediate layer is appropriately set depending on the type of optical recording medium and the number of recording layers. In the case of a three-layer BD-R, the thickness of the first intermediate layer is 20 μm to 30 μm, The thickness is about 13 μm to 23 μm.

  In the present invention, the minute protrusions on the stamper used when forming the intermediate layer to be laminated first among the plurality of intermediate layers are the minute protrusions on the other stampers used when forming the intermediate layer to be laminated later among the plurality of intermediate layers. Although it is preferable that it is located on the outer peripheral side of the protrusion, it is preferable that the distance between the two minute protrusions in the radial direction is 0.2 mm or more because it is difficult to obtain the effect of the present invention if the distance is too close. . More preferably, it is 0.4 mm or more. The upper limit is naturally determined by the number of layers of the optical recording medium and the width near the center hole.

  Also, the fine protrusion on the stamper used when forming the intermediate layer that is laminated first among the plurality of intermediate layers is smaller than the fine protrusion on the other stamper that is used when forming the intermediate layer that is laminated later among the plurality of intermediate layers. As for the distance in the radial direction of the two microprotrusions, as described above, it is preferably 0.2 mm or more, more preferably 0.4 mm or more. Preferably, the upper limit is naturally determined by the number of layers of the optical recording medium and the width near the center hole.

  In the present invention, the fine protrusions on the stamper need only satisfy the above-mentioned relationship, and it is not necessary to have the fine protrusions on the substrate, but the substrate has the same fine protrusions as on the stamper. In addition, it is preferable that the microprotrusions on the substrate exist at substantially the same radial position as the microprotrusions on the stamper used for forming the intermediate layer to be laminated last among the plurality of intermediate layers. This is because the blocking effect of the radiation curable resin raw material for the intermediate layer that is finally laminated is further increased. Here, “substantially the same” means that the deviation of the radial position of both microprotrusions is less than ± 0.2 mm. Within this range, it is possible to effectively suppress the disturbance at the inner peripheral side end of the intermediate layer. In this case, it is preferable that a plurality of minute protrusions are provided at different radial positions on the substrate, and the positions correspond to the minute protrusion positions on each stamper. This is because by using such a substrate, the blocking effect of the radiation curable resin material is further increased.

(About stamper)
As the stamper used in the embodiment of the present invention, conventionally known ones such as a metal stamper made of a metal material such as nickel, a glass stamper made of glass, and a resin stamper made of a resin material can be appropriately used. Of the resin stampers, a stamper having radiation transparency is referred to as a radiation transmission stamper.

The “radiation transparency” of the radiation transmission stamper used in the embodiment of the present invention refers to the radiation permeability when the radiation curable resin material is cured. Specifically, it means that the radiation has a transparency of usually 30% or more, preferably 50% or more, more preferably 60% or more. On the other hand, the transmittance with respect to the radiation is ideally 100%, but usually 99.9% or less.
In the present invention, “radiation” is used to include electron beams, ultraviolet rays, visible light, and infrared rays.

  Since the radiation transmissive stamper can be irradiated with radiation from the stamper, the resin material can be cured without being affected by the radiation transmittance of the recording / reproducing functional layer, the substrate, etc., which is preferable for the present invention. Used.

  As the radiation transmissive stamper, a conventionally known material can be used as appropriate by using a known production method. As a material for the radiation transmissive stamper, for example, a nonpolar material such as a polyolefin resin or a polystyrene resin, or a general-purpose and low-cost resin such as a polycarbonate resin or an acrylic resin can be used. In addition, the material of a radiolucent stamper may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  Among these, a polycarbonate-based resin capable of realizing a highly accurate groove shape at low cost is preferable, and it is particularly preferable to use a conventionally known polycarbonate-based resin as a substrate of an optical recording medium.

  The radiation transmissive stamper can be produced by injection molding or the like using, for example, a metal stamper (for example, a nickel stamper) having a concavo-convex pattern opposite to the transfer concavo-convex shape of the radiation transmissive stamper. .

  Furthermore, the radiation transmissive stamper is usually formed in a disc shape in which a central hole penetrating the front and back is formed in the central portion. Also in the embodiment of the present invention, it is preferable to use a radiolucent stamper having a disk-like shape having a concavo-convex shape for transfer on the surface and a central hole formed in the center.

  The thickness of the radiolucent stamper used in the embodiment of the present invention is preferably 0.3 mm or more in terms of shape stability and ease of handling. However, it is usually 5 mm or less. If the thickness of the radiation transmissive stamper is within this range, the radiation curable resin material can be efficiently cured even when irradiated with radiation through the radiation transmissive stamper because it has sufficient radiation transparency. , Productivity can be improved.

  The outer diameter of the radiation transmissive stamper is preferably larger than the outer diameter of the substrate (the outer diameter of the optical recording medium). If the outer diameter of the radiation transparent stamper is designed to be larger than the outer diameter of the substrate in advance, the outer peripheral part outside the outer diameter of the optical recording medium will be formed with a margin in the injection molding. Therefore, it is possible to form a favorable concavo-convex shape over the entire region used for forming the intermediate layer of the radiation transmissive stamper.

  Further, by making the outer diameter of the radiation transmissive stamper larger than the outer diameter of the substrate, the outer diameter of the radiation transmissive stamper becomes larger than the outer diameter of the intermediate layer. If it does in this way, it will become easy to make the shape of the outer peripheral side end face of an intermediate layer good. Specifically, when the radiation transmissive stamper is placed on the radiation curable resin material, the radiation curable resin material layer resin may adhere to the outer peripheral edge of the radiation transmissive stamper or the intermediate layer, This resin may become a burr when peeling off the radiation transmissive stamper. Therefore, by making the outer diameter of the radiation transmissive stamper larger than the outer diameter of the intermediate layer, the resin that tends to become burrs exists outside the outer diameter of the intermediate layer, that is, at the outer peripheral end of the radiation transmissive stamper. It becomes. As a result, even if burrs are generated, the burrs can be removed without affecting the end face of the intermediate layer.

  Specifically, the outer diameter of the radiation transmissive stamper is preferably larger by 1.0 mm or more in diameter than the outer diameter of the substrate, more preferably 2.0 mm or more. However, the difference from the outer diameter of the substrate is usually 15 mm or less in diameter, and preferably 10 mm or less.

  Annular minute protrusions can be formed on the surface of the radiation transmissive stamper by controlling the shape of the mold and the mold jig during injection molding. For example, it is possible to form minute projections generated by the presence of a gap formed between the jig for fixing the inner peripheral portion of the stamper and the stamper at a desired height by adjusting the stamper inner diameter and the fixing jig. Alternatively, it is also possible to form a microprojection by forming a groove on the surface of the fixing jig or stamper by machining and filling the resin with resin at the time of injection molding.

  Metal stampers, glass stampers, and the like can also be appropriately manufactured by a conventionally known manufacturing method. For example, if the protrusion is formed directly on the surface, or if it is difficult to do so, the inner diameter of the stamper (the deformation during machining that occurs at the inner diameter end is diverted), or a minute protrusion is applied to the fixing jig on the inner periphery. Can be considered.

(About radiation curable resin raw materials)
The radiation curable resin material used for forming the intermediate layer is not particularly limited as long as it contains a radiation curable resin that is cured by radiation. A radiation curable resin may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the radiation curable resin include various types such as an ultraviolet curable resin and an electron beam curable resin, and among them, an ultraviolet curable resin is particularly preferable. By adopting the ultraviolet curable resin, it becomes easy to transfer the uneven shape of the stamper.

  Examples of the ultraviolet curable resin include a radical type (radical polymerization type) ultraviolet curable resin and a cationic type (cation polymerization type) ultraviolet curable resin, and these conventionally known materials can be appropriately used.

  When using radical type ultraviolet curable resin for a radiation curable resin raw material, the composition which contains an ultraviolet curable compound (radical type ultraviolet curable compound) and a photoinitiator as an essential component can be used, for example. . As the radical ultraviolet curable compound, for example, monofunctional (meth) acrylate and polyfunctional (meth) acrylate can be used as the polymerizable monomer component. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Here, acrylate and methacrylate are collectively referred to as (meth) acrylate.

Moreover, although there is no restriction | limiting in a photoinitiator, For example, a molecular cleavage type or a hydrogen abstraction type is preferable. In the present invention, it is preferable to obtain an intermediate layer by curing an uncured radiation curable resin material mainly composed of a radical polymerization type acrylic ester.
On the other hand, when a cationic ultraviolet curable resin is used as a radiation curable resin material, for example, an epoxy resin containing a cationic polymerization type photoinitiator can be used.

Examples of the epoxy resin include bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. As the epoxy resin, it is preferable to use a resin having a low content of free chlorine and chlorine ions. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.
Examples of the cationic polymerization type photoinitiator include sulfonium salts, iodonium salts, diazonium salts, and the like.

  Moreover, it is preferable to use what is a liquid in 20 to 40 degreeC as a radiation curable resin raw material. This is because when the radiation curable resin material is applied, it can be applied without using a solvent, so that productivity is improved. Moreover, it is preferable to adjust suitably the viscosity of a radiation curable resin raw material so that it may become 50 cP or more and 1000 cP or less at normal temperature. More preferably, it is 100 cP or more. Moreover, 500 cP or less is still more preferable, Especially preferably, it is 400 cP or less. The viscosity of the radiation curable resin material can be adjusted by appropriately changing the monomer content in the radiation curable resin material.

(About other layers)
In the case of a Blu-ray disc, a cover layer made of a light transmissive material is provided on the outermost surface on the incident side of recording / reproducing light. As a method for forming the cover layer, a conventionally known manufacturing method such as a spin coating method can be applied. As the cover layer material, urethane, epoxy, acrylic resin, or the like is used, and after spin coating, it is cured by irradiating with ultraviolet rays, electron beams, or radiation to accelerate radical polymerization or cationic polymerization.

  The cover layer material is preferably a composition comprising an acrylic or methacrylate oligomer and / or monomer from the viewpoints of light transmission and durability. More specifically, (meth) acrylate oligomers such as polyether (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, iso- One or more monofunctional (meth) acrylate monomers such as octyl acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl (meth) acrylate A uniformly mixed composition is preferred. Control of physical properties such as glass transition temperature Tg, tack performance (adhesive force immediately formed when contacted at low pressure), peel strength, shear holding force, etc. by adjusting the molecular weight of the oligomer and the type and amount of the monomer can do.

  Further, the cover layer may be additionally provided with a hard coat layer having a thickness of about 0.1 μm to 50 μm on the surface in order to impart functions such as scratch resistance and fingerprint resistance to the incident light side surface. . The thickness of the cover layer is appropriately set depending on the number of recording layers and the like, but is preferably 0.01 mm or more, more preferably 0.03 mm or more, and preferably 0.3 mm or less, more preferably 0.15 mm or less. . It is preferable that the entire thickness including the thickness of the adhesive layer, the hard coat layer, and the like be in an optically acceptable thickness range. For example, in a three-layer BD-R, it is preferable to control to about 57 μm ± 5 μm or less.

The recording layer material is not particularly limited as long as it can be applied to a normal optical recording medium, and the manufacturing method according to the embodiment of the present invention can be applied. For example, not only an organic dye material but also a phase change recording material, a partial nitride film, and a partial oxide film can be used. As a specific example of the phase change recording material, it is preferable to use a composition mainly composed of Sb such as SbTe, GeSbTe, InSbTe, AgSbTe, AgInSbTe, GeSbSn, InGeSbTe, or InGeSbSnTe. . Specific examples of the partial nitride film and partial oxide film include partial nitride films such as BiGeN and SnNbN, and partial oxide films such as TeOx and BiFOx.
In addition, in the design of the optical recording medium, a recording / reproducing functional layer may be configured by providing conventionally known layers having various functions such as a reflective layer and a protective layer.

B. Other Preferred Forms of Manufacturing Method of Optical Recording Medium of the Present Invention In the above description, the manufacturing method of the optical recording medium of the present invention has been described by taking a single-sided three-layer BD-R disc as an example. However, the present invention is not limited to this. is not. That is, a radiation curable resin raw material is applied on the data substrate directly or via another layer, a radiation transmissive stamper having a concavo-convex shape is fixed, and then peeled off, so that the resin has a concavo-convex shape of the radiation transmissive stamper. If it is an optical recording medium or a laminated body for an optical recording medium manufactured by a manufacturing method including a step of transferring and forming an intermediate layer a plurality of times, the effect of the present invention is exhibited well. That is, the manufacturing method of the embodiment of the present invention can be applied to optical recording media having other configurations.

  For example, the present invention can be applied to an optical recording medium having four or more recording layers and three or more intermediate layers. In this case, the manufacturing method of the embodiment of the present invention can be applied to form each of the three or more intermediate layers.

  Specific embodiments of the present invention will be described below in more detail with reference to examples. However, the present invention is not limited to these examples without departing from the gist thereof.

Example 1
An example in which a write-once three-layer Blu-ray disc is manufactured using the method of the present invention will be described.
A plurality of sputter film forming steps on the surface of a polycarbonate substrate having a thickness of 1.1 mm, a diameter of 120 mm, and a center hole diameter of 15 mm, which is produced by injection molding and has a groove with a track pitch of 0.32 μm and a depth of 20 nm transferred to the surface. After that, a write-once first recording / reproducing functional layer made of an inorganic film was formed (hereinafter referred to as “data substrate”). Separately, as a first stamper, a polycarbonate substrate having a thickness of 0.6 mm, a diameter of 124 mm, and a center hole diameter of 15 mm, in which grooves having a pitch of 0.32 μm and a depth of 20 nm were transferred to the surface by injection molding, was produced ( Hereinafter, described as “radioactive stamper A”). The grooves on the surface of the data substrate and the grooves on the surface of the radiation transmissive stamper A were made to have a concave and convex orientation opposite to each other by using the concave and convex orientation of the grooves of the nickel stamper used for injection molding.

  The data board has a circle with a height of 10 to 15 μm and a maximum width of 100 μm in the radial section by adjusting the boundary between the nickel stamper and the inner periphery fixing jig at a radius of 10.0 mm. A continuous annular microprojection was formed in the circumferential direction. In addition, the above-mentioned radiolucent stamper A has a height of 10 to 15 μm and a maximum in a radial cross section by adjusting the boundary between the nickel stamper and its inner periphery fixing jig at a radius of 11.0 mm. An annular microprotrusion that is substantially 100 μm and continuous in the circumferential direction was formed.

First, an ultraviolet curable resin material V (acrylic resin, viscosity of about 400 cP) having excellent transferability is applied to the concavo-convex shape surface of the radiation transmissive stamper A by spin coating, and cured by ultraviolet irradiation to form a transfer layer. did. The amount of ultraviolet irradiation was 76 mJ / cm ² .

  Next, the radiation transmissive stamper A on which the transfer layer was formed and the data substrate were fixed on separate turntables, and then opposed by passing the same central axis through the central hole at an interval of 3 mm.

  Next, the gap between the data substrate and the radiation transmissive stamper A is filled with an ultraviolet curable resin raw material W (acrylic resin, viscosity of about 410 cP) by the gap dispense method, the data substrate is fixed, and only the radiation transmissive stamper A is provided. The UV curable resin material W was stretched to some extent over the entire data substrate surface by rotating 180 ° at 15 rpm and twisting, applying a load of 80 g to the entire substrate.

  Next, the ultraviolet curable resin raw material W of the ultraviolet curable resin raw material W is obtained by performing vacuum suction at a pressure of −12 kPa from the vacuum suction pores provided on the side surface of the central axis penetrating the data substrate and the central hole of the radiation transmissive stamper A. A state in which the extending end on the inner peripheral side is blocked by a minute protrusion provided at a radius of 11.0 mm on the radiolucent stamper A was realized.

Next, using a light-shielding mask, ultraviolet rays were irradiated only to the inner peripheral portion within a radius of 12 mm at 180 mJ / cm ² to cure the ultraviolet curable resin raw material W only to the inner peripheral portion. Then, the data substrate and the radiation transmissive stamper A were integrally rotated at a high speed of 7800 rpm so that the first intermediate layer was formed on the entire surface of the data substrate with a substantially uniform film thickness, here 25 μm.

Thereafter, the entire surface of the data substrate was irradiated with ultraviolet rays at 544 mJ / cm ² to completely cure the ultraviolet curable resin raw material W, and then the radiation transmissive stamper A was peeled off to form a first intermediate layer on the data substrate. .
Next, a write-once type second recording / reproducing functional layer was formed on the first intermediate layer in the same manner as the first recording / reproducing functional layer.

  Next, similarly to the radiation transmissive stamper A, a radiation transmissive stamper B was produced as a second stamper. However, the annular minute protrusions on the radiolucent stamper B were formed at a position of a radius of 10.0 mm with a height of 10 to 15 μm and a maximum width of 100 μm in the radial cross section.

Further, the second intermediate layer was formed using the radiation transmissive stamper B in the same manner as the formation of the first intermediate layer. The production conditions were controlled so that the film thickness of the second intermediate layer was 18 μm.
However, since the radiolucent stamper B was used, the inner peripheral end of the second intermediate layer was formed in the vicinity of a radius of 10.0 mm.

Further, a third recording / reproducing functional layer was similarly formed on the second intermediate layer, and a cover layer was formed on the outermost surface of the data substrate using the ultraviolet curable resin raw material X (urethane resin, viscosity of about 1000 cP). .
The cover layer was formed by spin coating at a maximum rotation speed of 2000 rpm and irradiating with an ultraviolet ray of 600 mJ / cm ² to be cured to a film thickness of 54 μm.

  In the first intermediate layer forming step, which is the first intermediate layer forming step in the above steps, 5000 data substrates were introduced to manufacture an optical recording medium. Those determined to be defective in a certain process are not thrown into subsequent processes.

(Comparative Example 1)
At the time of forming the second intermediate layer, 1500 data substrates were loaded in the same process as in Example 1 except that the radiation transmissive stamper A was used as the second stamper, and an optical recording medium was manufactured.

(Evaluation method of optical recording medium)
In the manufacturing process of the optical recording medium of Example 1 and Comparative Example 1, the effect of the present invention is shown by examining the generation ratio of defective products.
Since the manufacturing steps of Example 1 and Comparative Example 1 are the same up to the formation of the second recording / reproducing functional layer, the occurrence rate of defective products in the manufacturing steps after the formation of the second intermediate layer was examined.
The evaluation items are as follows.

(1) Poor peeling of the second intermediate layer When the second intermediate layer was formed, when the second stamper was peeled from the substrate, a case where the peeling could not be completely occurred occurred. This case was regarded as a second intermediate layer peeling failure (failed).

(2) Appearance defect of 2nd intermediate | middle layer About the thing which the 2nd stamper was able to peel, the defect detection of the 2nd intermediate | middle layer was performed with the in-line scanner (Doctor Schenck ISM.blue +). The defect determination criteria for the second intermediate layer were set as appropriate based on past examinations, and when there was even one unacceptable defect, it was determined to be unacceptable.

(3) Cover layer defect defect and cover layer film thickness defect About what passed the second intermediate layer external appearance defect, the defect detection of the cover layer and the film thickness of the cover layer by an inline scanner (Doctor Schenck ISM.blue +) Inspection was performed to evaluate defect defects and film thickness defects. The defect determination criteria for the cover layer were also set as appropriate based on past studies, and when there was even one unacceptable defect, it was determined to be unacceptable. Regarding the film thickness of the cover layer, the film thickness of one circumference is measured at each of the seven radial positions in the radius range of 23.5 mm to 58.3 mm. When the average film thickness for one round of the sample exceeded the range of ± 2.5 μm even at one point, it was judged as rejected.

(Evaluation results)
The evaluation results of Example 1 and Comparative Example 1 are shown in Table 1. The rejection rate in the table is a percentage of the number of rejected sheets with respect to the number of sheets input in the second intermediate layer forming step or the cover layer forming step.

  As can be seen from Table 1, the manufacturing method of Example 1 shows a defect rate lower than that of Comparative Example 1 in all evaluation items, and the manufacturing method of the optical recording medium of the present invention has few defects and uniformity. It is clear that this is a method capable of efficiently producing an excellent optical recording medium.

DESCRIPTION OF SYMBOLS 100 Optical recording medium 101 Substrate 102 1st recording / reproducing functional layer 103 1st intermediate | middle layer 103a 1st radiation curable resin raw material 104 2nd recording / reproducing functional layer 105 2nd intermediate | middle layer 105a 2nd radiation curable resin raw material 106 3rd recording Reproduction functional layer 107 Cover layer 111 Data substrate 112 First stamper 113 Second stamper 121, 122 Radiation 123 Laser light 201, 301 Substrate 202, 302 Minute protrusion 203 on substrate 203, 303 Central hole 204, 304 First stamper 205 , 305 Minute protrusions on the first stamper 207, 307 Second stamper 208, 308 Minute protrusions on the second stamper 206, 306 Central hole of the first stamper 209, 309 Central hole of the second stamper 211, 311 First recording / reproduction Functional layer 212, 215, 312, 315 Transfer 213, 313 First intermediate layer 213a, 313a First radiation curable resin raw material 214, 314 Second recording / reproducing functional layer 216, 316 Second intermediate layer 216a, 316a Second radiation curable resin raw material 231, 232, 331, 332 Radiation 221, 321 Inner peripheral end of the first intermediate layer 222, 322 Inner peripheral end of the second intermediate layer

Claims (8)

An optical recording medium comprising a disc-shaped substrate having a central hole and three or more recording layers, and a plurality of intermediate layers having a concavo-convex shape made of a radiation curable resin material interposed between the recording layers. A manufacturing method comprising:
In the step of forming the plurality of intermediate layers using a plurality of stampers having a disk-like shape and having a concavo-convex shape for transfer corresponding to the concavo-convex shape on the surface,
The plurality of stampers have annular minute protrusions concentric with the center of each of the plurality of stampers on the surface having the uneven shape for transfer,
Among the plurality of intermediate layers, the plurality of stampers used in forming the plurality of stampers has a radial position of a minute protrusion on one stamper, and the plurality of intermediate layers used in forming another intermediate layer. A manufacturing method of an optical recording medium, characterized in that it differs from the radial position of the minute protrusions on the other stamper among the stampers. 2. The method of manufacturing an optical recording medium according to claim 1, wherein the plurality of stampers have a center hole, and the minute protrusions are provided in the vicinity of the center hole. In the step of forming one intermediate layer among the plurality of intermediate layers,
A step of making the surface of the stamper of the stamper having the fine protrusions and the substrate face each other, and filling the gap between one stamper of the plurality of stampers and the substrate with the radiation curable resin material; ,
Stretching the radiation curable resin raw material;
A step of irradiating radiation to cure the radiation curable resin raw material in this order,
When one stamper of the plurality of stampers and the substrate face each other, the micrometer on one stamper of the plurality of stampers is disposed in a region from the center hole of the substrate to the inner diameter of the clamp area. 3. A method for manufacturing an optical recording medium according to claim 1, wherein protrusions are formed. Among the plurality of intermediate layers, the radial position of the microprojections on one stamper of the plurality of stampers used when forming the intermediate layer that is laminated first,
4. The method according to claim 1, wherein the plurality of stampers used at the time of forming an intermediate layer to be laminated later among the plurality of intermediate layers are located on an outer peripheral side with respect to minute protrusions on another stamper. The method for producing an optical recording medium according to Item. Among the plurality of intermediate layers, the radial position of the microprojections on one stamper of the plurality of stampers used when forming the intermediate layer that is laminated first,
4. The method according to claim 1, wherein the plurality of stampers used when forming an intermediate layer to be laminated later among the plurality of intermediate layers are located on an inner peripheral side with respect to minute protrusions on another stamper. 5. 2. A method for producing an optical recording medium according to item 1. The substrate has an annular minute protrusion concentric with the center of the substrate on a surface where the plurality of intermediate layers are formed, and the minute protrusion on the substrate is the last of the plurality of intermediate layers. 6. The method according to claim 1, wherein the plurality of stampers used for forming the intermediate layer stacked on the substrate are present at substantially the same radial position as a minute protrusion on one stamper. Of manufacturing an optical recording medium. The method for manufacturing an optical recording medium according to claim 6, wherein the minute protrusions formed on the substrate are intermittently formed in a circumferential direction. The method for manufacturing an optical recording medium according to claim 1, wherein the minute protrusions formed on the plurality of stampers are formed intermittently in a circumferential direction. .

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