JP2006139822A - Manufacturing method of optical recording medium substrate, and optical recording medium substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably manufacture an optical recording medium substrate for BD, etc., which has a satisfied shape of corner parts of the side where recording layers of a center opening section are laminated, and has a satisfied accuracy of chucking. <P>SOLUTION: An injection molding die 2 is prepared, which includes a set of dies 20, 30 disposed to face oppositely while interposing a resin molding space section 40 to mold the optical recording medium substrate therein by being injected with polycarbonate resin, and in which a resin injection hole 21a for injecting a molten resin to the resin molding space section 40 is provided on one die 20 while a cut punch 32 for forming a center opening section on the resin injected to the resin molding space section 40 and a stamper 36 for transferring a surface irregularity pattern to the resin injected to the resin molding space section 40 are provided on another die 30, then the optical recording medium substrate is molded in such a manner that a wall surface temperature of the resin injection hole 21a is settled to be ≥60°C, a surface temperature of the cut punch 32 is to be ≥80°C, and a period from the finish of resin injection into the resin molding space section 40 to the start of formation of the center opening section by the cut punch 32 is settled to be within 0.4 sec. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical recording medium substrate for BD (Blu-ray Disc) and the like, and an optical recording medium substrate manufactured by the method, and more particularly to optimization of molding conditions.

  Optical recording media such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and BDs (Blu-ray Discs) have fine surface irregularities including information pits and grooves, and have a central opening (center hole). At least the recording layer is laminated on the surface of the formed resin optical recording medium substrate. As a raw material resin for the optical recording medium substrate, a polycarbonate resin is generally used because of transparency and non-hygroscopicity.

As a molding die for an optical recording medium substrate, an injection molding die having a sectional structure shown in FIG. 3 is widely used. This injection mold includes a fixed mold 110 and a movable mold 120 which are arranged to face each other through a resin molding space 130 into which an optical recording medium substrate is molded by injecting resin. A resin injection hole 111 for injecting resin into the molding space 130 and a stamper 112 for transferring the surface unevenness pattern to the resin injected into the resin molding space 130 are provided. A cut punch 121 for forming a central opening in the injected resin is provided (Patent Document 1, etc.).
JP-A-9-164562

  When the central opening is formed by punching the resin with a cut punch, a burr 212 is formed on the tip side of the cut punch 121 on the optical recording medium substrate 210 to be molded as shown in the enlarged cross section of FIG. Cheap. In the above-described general injection molding die, the stamper 112 is provided on the fixed die 110, and the cut punch 121 is provided on the movable die 120. Therefore, the stamper 112 side of the central opening 211 (the recording layer is laminated). The burr 212 is easily formed at the corner on the other side.

  In a CD or DVD, the optical recording medium substrate side (the side opposite to the recording layer) is chucked, and light is incident from the chucking side to perform recording / reproduction. On the other hand, as shown in FIG. 4B, in the BD 200, the recording layer 220 side is chucked, and light is incident from the chucking side to perform recording / reproduction. In the figure, reference numeral 300 denotes a spindle motor of the optical recording / reproducing apparatus.

  In the optical recording medium substrate, the corner shape on the chucking side of the central opening is important.

  In the conventional injection mold described above, it has been described that burrs are likely to be formed at the corner on the stamper side (the side where the recording layer is laminated) of the central opening, but as shown in FIG. In the BD 200, the side on which the burr 212 is easily formed is chucked. If there is a burr, the BD tilts during chucking and the chucking accuracy is lowered, and the recording / reproduction accuracy is lowered.

  Patent Document 1 also discloses an injection mold in which a movable die is provided with both a cut punch and a stamper. In an optical recording medium substrate for BD manufactured using such a mold, no burrs are formed on the chucking side, so the above problem does not occur. However, since it is not common as a conventional injection mold for an optical recording medium substrate, examination of molding conditions has not been sufficiently performed.

  As a result of studies by the present inventor, even if the molding conditions in the case of using the general injection mold shown in FIG. 3 are applied as they are, the roundness r at the corner on the recording layer side of the central opening is not changed. May exceed 0.1 mm. When the roundness r of the corner portion on the chucking side of the central opening exceeds 0.1 mm, the chucking accuracy is lowered and the recording / reproducing accuracy is lowered as in the case where there is a burr.

  The present invention has been made in view of such circumstances. An optical recording medium substrate for a BD or the like having a good corner shape on the side where the recording layer of the central opening is laminated and good chucking accuracy is stably provided. It is an object of the present invention to provide a method for manufacturing an optical recording medium substrate that is manufactured automatically.

The method for producing an optical recording medium substrate according to the present invention includes an optical recording medium substrate made of polycarbonate resin having a surface unevenness pattern and having a central opening formed thereon, and laminated on the surface unevenness pattern side of the optical recording medium substrate. In the method of manufacturing an optical recording medium substrate of an optical recording medium in which light is incident from the recording layer side and recording / reproduction is performed.
A pair of molds arranged opposite to each other with a resin molding space portion into which polycarbonate resin is injected and the optical recording medium substrate is molded, and one of the pair of molds includes the resin molding space portion; A resin injection hole for injecting a molten resin is provided on the other side, and on the other side, a cut punch for forming the central opening in the resin injected into the resin molding space, and the resin injected into the resin molding space Prepare an injection mold with a stamper to transfer the surface uneven pattern,
The wall surface temperature of the resin injection hole is set to 60 ° C. or more, the surface temperature of the cut punch is set to 80 ° C. or more, and the formation of the central opening by the cut punch is started after the resin injection into the resin molding space is completed. The optical recording medium substrate is formed for a time of 0.4 seconds or less.

  The optical recording medium substrate of the present invention is manufactured by the above-described method for manufacturing an optical recording medium substrate of the present invention.

  In the present invention, among the pair of molds arranged opposite to each other with the resin molding space interposed therebetween, an injection mold in which both a cut punch and a stamper are provided is used. No burr is formed at the corner on the side where the recording layer is laminated.

  In addition, since it is configured to specify the wall temperature of the resin injection hole, the surface temperature of the cut punch, and the time from the end of the resin injection to the resin molding space until the start of the formation of the central opening by the cut punch, the central opening The roundness r at the corner on the side where the recording layer is laminated can be stably set to 0.1 mm or less.

  Therefore, according to the present invention, it is possible to stably manufacture an optical recording medium substrate for BD or the like having a good corner shape on the side where the recording layer of the central opening is laminated and good chucking accuracy. it can.

"Example of optical recording media"
The present invention relates to a method for manufacturing an optical recording medium substrate such as a BD (Blu-ray Disc) in which light is incident from the recording layer side and recording / reproduction is performed. Prior to the description of the manufacturing method, the light to which the present invention is applied. A configuration example of the recording medium will be briefly described. FIG. 1 is a sectional view in the thickness direction.

  An optical recording medium 1 such as a BD shown in the figure has an optical recording medium substrate 11 made of polycarbonate resin having a surface unevenness pattern P on one surface and having a central opening 11a, and the surface of the optical recording medium substrate 11 The light reflection layer 12 / the recording layer 13 / the light-transmitting protective layer 14 are sequentially laminated on the concave / convex pattern P side.

  In an optical recording medium 1 such as a BD, unlike a CD or DVD, the recording layer 13 side (the upper side in the figure) is chucked and light enters from the chucking side when it is inserted into a recording / reproducing apparatus. Playback is performed. For convenience, the surface on the recording layer 13 side of the optical recording medium substrate 11 is referred to as a front surface 11x, and the opposite surface is referred to as a back surface 11y. On the surface 11x of the optical recording medium substrate 11, the surface uneven pattern P is formed at least in a region where the recording layer 13 and the like are laminated. The back surface 11y is a mirror surface.

"Method of manufacturing optical recording medium substrate"
Next, the manufacturing method of the optical recording medium substrate of the present invention will be described by taking the optical recording medium substrate 11 as an example.

  The method for manufacturing an optical recording medium substrate of the present invention uses an injection mold in which one of a cut punch and a stamper is provided on one of a pair of molds arranged to face each other with a resin molding space interposed therebetween. The optical recording medium substrate is molded, and the molding conditions at that time are specified.

(Example of injection mold)
An example of a suitable injection mold is shown in FIG. 2, and its structure will be described. FIG. 2 is a cross-sectional view corresponding to FIG.

  The injection mold 2 shown in the figure is composed of a pair of a fixed mold 20 and a movable mold 30 that are arranged opposite to each other with a resin molding space 40 into which a polycarbonate resin is injected and an optical recording medium substrate 11 is molded. . The optical recording medium substrate 11 to be molded has a back surface 11y on the fixed mold 20 side and a front surface 11x on the movable mold 30 side. Each of the fixed mold 20 and the movable mold 30 is composed of a plurality of members arranged concentrically.

  The fixed mold 20 has a sprue 21 having a resin injection hole 21a for injecting a molten resin into the resin molding space 40 from the center side, a cut punch receiving portion 22 into which a distal end portion of a cut punch 32 described later enters, and a mirror surface. The mirror blocks 23 and 24 forming the back surface 11y of the optical recording medium substrate 11 are sequentially arranged concentrically.

  The surface of the sprue 21 on the resin molding space 40 side is set to be one step lower than the surface of the cut punch receiving portion 22 on the resin molding space 40 side. A receiving space 25 is formed.

  The movable mold 30 is a mold that moves in the horizontal direction in the figure (perpendicular to the inner surface of the movable mold 30) and opens and closes the injection mold 2. The movable die 30 protrudes from the center side from the inner surface of the movable die 30 and ejects the unnecessary resin formed by the resin injection hole 21 a and the cut punch receiving space 25, and the inner surface of the movable die 30. Then, the cut punch 32 that forms the central opening 11 a in the resin injected into the resin molding space 40 and the inner surface of the movable mold 30 protrude from the inner surface of the movable mold 30 to push out the molded optical recording medium substrate 11. An ejector 33, a stamper inner holder 34 that holds the inner peripheral side of the stamper, and a mirror block 35 are sequentially arranged concentrically.

  The “inner surface of the movable mold 30” here means the inner surface of the movable mold 30 before the start of molding. FIG. 2 shows a state in which a part of the eject pin 31 and the cut punch 32 protrudes from the other constituent members of the movable mold 30, but before the start of molding, the tip of the eject pin 31 and the cut punch 32. The surface is flush with the stamper 36 and the like.

  The eject pin 31 has a shape that can be inserted into the resin injection hole 21 a of the fixed mold 20 and is incorporated in the cut punch 32. A stamper 36 for transferring the surface unevenness pattern P to the resin injected into the resin molding space 40 is attached to the stamper inner holder 34 and the mirror block 35.

  In the injection mold 2, both the cut punch 32 and the stamper 36 are provided on the movable mold 30 side of the fixed mold 20 and the movable mold 30 as described above.

  The injection mold 2 is also provided with a temperature adjustment mechanism (not shown) that adjusts the constituent members of the fixed mold 20 and the movable mold 30 to a predetermined temperature.

(Manufacturing process)
Next, the manufacturing process of the optical recording medium substrate 11 will be described.

  Prior to molding, a polycarbonate resin, which is a raw material resin of the optical recording medium substrate 11, is heated to a glass transition temperature or higher in advance to prepare a molten resin. The glass transition temperature (Tg) of the polycarbonate resin as the raw material resin is usually about 135 to 155 ° C., and the melting and heating temperature of the resin is usually set to about 300 to 390 ° C.

  First, the prepared molten resin is injected into the resin molding space 40 from the resin injection hole 21 a of the fixed mold 20. After the resin injection into the resin molding space 40 is completed, a slight pressure is applied from the resin injection side to prevent the resin from flowing backward, and this state is maintained.

  Next, the cut punch 32 is projected from the inner surface of the movable mold 30. The front end of the cut punch 32 enters the cut punch receiving space 25 of the fixed die 20, and a part of the resin injected into the resin molding space 40 is punched to form the central opening 11a. Through the above operation, the optical recording medium substrate 11 is molded in the injection mold 2.

  Finally, the ejector 33 and the eject pin 31 are projected from the inner surface of the movable mold 30 to extrude the molded optical recording medium substrate 11 and the unnecessary resin formed by the resin injection hole 21a and the cut punch receiving space 25, By taking out the optical recording medium substrate 11, the manufacture of the optical recording medium substrate 11 is completed.

(Molding condition)
Next, molding conditions will be described. The present inventor can perform good molding by specifying the wall surface temperature T _a of the resin injection hole 21 _a , the surface temperature T _{b of} the cut punch 32, and the timing of starting the formation of the central opening 11 a by the cut punch 32. It has been found that the roundness r of the corner 11b (see FIG. 1) on the recording layer 13 side of the central opening 11a can be stably set to 0.1 mm or less. Hereinafter, each condition will be described.

<Wall surface temperature T _a of resin injection hole 21a>
In the present invention, by adjusting the temperature of the sprue 21, a wall surface temperature T _a of the resin injection hole 21a as 60 ° C. or higher, carrying out the molding.

Conventionally, after injecting a molten resin heated to a temperature higher than the glass transition temperature (Tg) into a molding die, it is preferable to lower the temperature as soon as possible to solidify the resin. For this reason, conventionally, in forming an optical recording medium substrate for a CD or DVD, the temperature _Ta is usually set to about 40 ° C. (see Comparative Example 2 below). In contrast, the present inventor has higher temperature T _a than the conventional, 60 ° C. or higher, that preferably set to at least 80 ° C., it has been found to be able to implement the good molding. Temperature T _a is less than 60 ° C., and proceeds excessively solidified resin punching, resin becomes too hard, rounded r of the corner portion 11b is presumed that tends greater.

The upper limit of the temperature T _a is not limited. However, when the temperature T _a is too high, too slow solidification of the resin, because the productivity is lowered, the temperature T _a is preferably set below 120 ° C..

<Surface temperature _T b of the cut punch 32>
In the present invention, by adjusting the temperature of the cut punch 32, the surface temperature T _b of the cut punch 32 as 80 ° C. or higher, carrying out the molding.

For the same reason as the temperature T _a, is conventionally within a range Uchinukeru the resin by the cut punch, the cut punch can be set to a temperature as low as possible is to be preferred. For this reason, conventionally, in the formation of an optical recording medium substrate for CD or DVD, the temperature _Tb is usually set to about 60 ° C. (see Comparative Example 2 below). On the other hand, the present inventor has found that the molding can be carried out satisfactorily by setting the temperature _Tb to be higher than the conventional temperature, 80 ° C. or higher, preferably 100 ° C. or higher. Temperature T _b at is less than 80 ° C., and proceeds excessively solidified resin punching, resin becomes too hard, rounded r of the corner portion 11b is presumed that tends greater.

The upper limit of the temperature T _b is not limited. However, as with the temperature T _a, in consideration of productivity, the temperature T _b is preferably set below 120 ° C..

<Timing of starting formation of the central opening by the cut punch 32>
In the present invention, the molding is performed with the time T from the end of the resin injection into the resin molding space 40 to the start of the formation of the central opening 11a by the cut punch 32 within 0.4 seconds. The inventor has found that when the time T exceeds 0.4 seconds, the resin to be punched is solidified too much, the resin becomes too hard, and the roundness r of the corner portion 11b tends to increase.

  The punching of the resin by the cut punch 32 can also be started before the resin injection into the resin molding space 40 is completely completed (in this case, the time T becomes negative). However, in this case, since the punching is performed while the resin is being injected, the variation in the substrate thickness between shots tends to increase. Therefore, the time T is preferably 0 seconds or more.

  In the present invention, an injection mold in which both the cut punch 32 and the stamper 36 are provided on the movable mold 30 out of a set of the fixed mold 20 and the movable mold 30 that are opposed to each other with the resin molding space 40 interposed therebetween. 2 is used, no burr is formed at the corner 11b of the central opening 11a on the recording layer 13 side.

Also, the wall temperature T _a of the resin injection hole _21a, the surface temperature T _b of the cut punch _32, and a time T after the resin injection ends into the resin molding space portion 40 to form the start of the central opening 11a by the cut punch 32 Since the configuration is specified, as described above, the roundness r of the corner portion 11b on the recording layer 13 side of the central opening portion 11a can be stably set to 0.1 mm or less.

  Therefore, according to the present invention, it is possible to stabilize the optical recording medium substrate 11 for BD or the like having a good shape of the corner 11b on the recording layer 13 side (chucking side) of the central opening 11a and good chucking accuracy. Can be manufactured automatically. Since the optical recording medium substrate 11 obtained by the manufacturing method of the present invention has good chucking accuracy, the optical recording medium 1 such as a BD provided with this has good recording / reproducing accuracy.

  The laminated structure of the optical recording medium and the structure of the injection mold used for molding the optical recording medium substrate are not limited to the above, and can be appropriately changed within the scope of the present invention. It is.

  Next, examples and comparative examples according to the present invention will be described.

(Examples 1-4)
A polycarbonate resin (trade name “ST3000”, glass transition temperature 144 ° C.) manufactured by Teijin Bayer Polytech Co., Ltd. was used and heated to 360 ° C. to prepare a molten resin. This is injected into an injection mold having the structure shown in FIG. 2 (trade name “SD40ER” manufactured by Sumitomo Heavy Industries, Ltd.) to perform molding, and the outer diameter of the disk is 120 mmφ and the maximum thickness (reference numeral t in FIG. 1) 1 A BD substrate having a diameter of 1 mm and a central opening of 15 mmφ was manufactured. The mirror block mirror surface temperature on the fixed mold side was 120 ° C., the mirror block mirror surface temperature on the movable mold side was 118 ° C., the maximum injection speed was 120 mm / s, and the maximum mold clamping force was 392 kN.

In each example, the conditions shown in Table 1 (resin injection hole wall surface temperature T _a of _the surface temperature T _b of the cut _punch, and after the resin injection ends into the resin molding space portion to start the formation of the central opening by the cut punch The time T) was changed, and the molding was carried out with the other conditions being the same.

(Comparative Examples 1-3)
In Comparative Example 1, a BD substrate was manufactured in the same manner as in Example 1 except that an injection mold having the structure shown in FIG. 3 was used. In Comparative Examples 2 and 3, a BD substrate was manufactured in the same manner as in Example 2 except that the temperatures T _a and T _b , or the time T were set as shown in Table 1. In the table, * marks are attached to conditions that are outside the scope of the present invention.

(Evaluation)
The roundness r at the corner of the central opening of the BD substrate on which the recording layer is laminated (stamper side) was measured by “Formtracer SV-C500” manufactured by Mitutoyo Corporation. This measuring device can also evaluate burr.

(result)
The evaluation results are shown in Table 1.

Using an injection molding die which both the cut punch and the stamper is provided on the movable mold, cut the wall temperature T _a of the resin injection _hole, the surface temperature of the cut punch T _b, and after the resin injection ends into the resin molding space portion In each of Examples 1 to 4 in which the time T until the formation of the central opening by punching is within the definition of the present invention, no burr is formed at the corner on the recording layer side of the central opening. The roundness r at the corner was as good as 0.1 mm or less.

On the other hand, in Comparative Example 1 using an injection mold in which the movable die is provided with a cut punch and the fixed die is provided with a stamper, the corner portion on the recording layer side of the central opening has a height of 11 μm. A burr was formed. Further, in Comparative Example 2 in which the temperatures T _a and T _b are not defined in the present invention and in Comparative Example 3 in which the time T is not defined in the present invention, the roundness r at the corner on the recording layer side of the central opening is It was as large as 0.2 to 0.25 mm.

  The technique of the present invention can be applied to an optical recording medium such as a BD (Blu-ray Disc) in which light is incident from the recording layer side and recording / reproduction is performed.

It is a figure which shows an example of the optical recording medium with which this invention is applied. It is a figure which shows an example of the injection mold suitable for using for the manufacturing method of the optical recording medium board | substrate of this invention. It is a figure which shows the structure of the injection mold for a conventional general optical recording medium board | substrate. It is a figure which shows the conventional subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical recording medium 11 Optical recording medium board | substrate 13 Recording layer 2 Injection mold 20 Fixed mold | type 30 Movable mold | type 21a Resin injection hole 32 Cut punch 36 Stamper 40 Resin molding space part

Claims (2)

An optical recording medium substrate made of polycarbonate resin having a surface irregularity pattern and having a central opening formed thereon, and at least a recording layer laminated on the surface irregularity pattern side of the optical recording medium substrate, the recording layer In the method of manufacturing an optical recording medium substrate of an optical recording medium in which light is incident from the side and recording / reproduction is performed,
A pair of molds arranged opposite to each other with a resin molding space portion into which polycarbonate resin is injected and the optical recording medium substrate is molded, and one of the pair of molds includes the resin molding space portion; A resin injection hole for injecting a molten resin is provided on the other side, and on the other side, a cut punch for forming the central opening in the resin injected into the resin molding space, and the resin injected into the resin molding space Prepare an injection mold with a stamper to transfer the surface uneven pattern,
The wall surface temperature of the resin injection hole is set to 60 ° C. or more, the surface temperature of the cut punch is set to 80 ° C. or more, and the formation of the central opening by the cut punch is started after the resin injection into the resin molding space is completed. A method for manufacturing an optical recording medium substrate, comprising forming the optical recording medium substrate for a time of 0.4 seconds or less.   An optical recording medium substrate manufactured by the method for manufacturing an optical recording medium substrate according to claim 1.

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