JP4326047B2 - Information recording medium - Google Patents

Description

【００３５】
図４〜図６は、ディスク状の情報記録媒体の参考例を示している。この情報記録媒体１００におけるＡ−Ａの断面図は図５に示し、Ｂ−Ｂにおける断面は図６に示している。情報記録媒体１００はセンターホールＨを有し、基板１０１には光反射層１０２、記録層１０３、光透過層１０４が順次積層されている。記録層１０３と光透過層１０４には、情報信号Ｓを記録する。基板１０１の裏側には、複数本のリブ１１０が、放射方向（半径方向）にたとえば等間隔をおいて形成されている。図５と図６に示すように、基板１０１のセンターホールＨ側には、凸形状部分（チャッキング部）１０６が形成されている。
【００３６】
図４に示すように、リブ１１０が基板の裏面側に放射状に複数本形成されている。図５ではリブ１１０は見えないが、図６ではリブ１１０が見えている。つまりリブ１１０は、基板１０１の下方に突出してしかも半径方向に同じ厚みで形成されている。図５と図６に示す凸形状部分１０６、すなわちチャッキング部の厚みＬ４は、たとえば１．２ｍｍ±０．１ｍｍである。情報記録媒体１００の外周部の厚みＬ５は、たとえば０．６ｍｍ〜０．８ｍｍである。
図５と図６の例では、リブ１１０が、半径方向Ｒに沿って均一の厚さで放射状に形成されている。
これに対して、このリブ１１０が凸形状部分１０６から最外周部分に向けて順次薄くなるような構造を採用することもできる。
図４〜図６のような放射状のリブ構造を採用することにより、情報記録媒体１００の剛性の確保と軽量化が図れ、基板の慣性モーメントを少なくし、情報記録媒体１００の回転開始時のイナーシャを軽減することができる。
【００３７】
次に、図７と図８を参照して、上述した情報記録媒体１，１００を作成するための成形機と金型の例について説明する。
図７は、いわゆるディスク成形機（２色成形機）４０を示している。この成形機４０は、金型部４１と射出ユニット４２，４３を有している。射出ユニット４２の途中にはホッパー４２Ａが設けられ、射出ユニット４３の途中にはホッパー４３Ａが設けられている。金型部４１はノズル４５に対応して配置され、金型部４１は型締シリンダー４６によりピストン４７を作動させることで着脱可能に保持することができる。
【００３８】
図８は、このような金型部４１の構造例を示している。金型部４１は、固定金型４１Ａと可動金型４１Ｂを有している。固定金型４１Ａと可動金型４１Ｂの中には、樹脂が射出ユニット４２からスプルー５２を介してキャビティー内に注入されることにより、上述したような情報記録媒体１または１００の基板２または１０１を成形することができる。
この時に、固定金型４１Ａの中にはピットまたはグルーブを形成するためのスタンパー５３が配置されており、これによりディスクの基板にはピットまたはグルーブを同時に成形する。
上述したような情報記録媒体１または１００のセンターホールＨを形成するために、ディスクの基板２（１１あるいは１００）は、金型部４１内で図示しない油圧機構を有するパンチ５４により打ち抜かれるようになっている。
【００３９】
【実施例】
次に本発明のディスク状情報記録媒体のより具体的な実施例について説明する。
材料の説明：使用した材料は表１の通りである。
ＰＣ ：ポリカーボネート樹脂［帝人化成（株）製 パンライトＡＤ−５５０３、ＳＴ−３０００］
ＺＥＯＮＥＸ：アモルファスポリオレフィン樹脂［日本ゼオン（株）Ｅ−４８Ｒ、Ｌ−６］
ＡＢ ：導電性カーボンブラック［電気化学工業（株）製デンカブラック］
Ｗ ：ウィスカー［巴工業（株）ワラスナイト：サイカテックＮＮ−４］
【表１】

【００４０】
実施例１：テーパー構造ディスク
ポリカーボネート樹脂ＡＤ−５５０３の充填材無添加で下記ディスク形状で図１のテーパー構造ディスク（情報記録媒体）として、最外周厚さ０．６ｍｍと０．４ｍｍのディスクを各々作成した。
比較例として図１４の１．２ｍｍ均一厚さの従来構造と、図９と図１０のチャッキング部（クランピング部）の厚さは１．２ｍｍで直径３３ｍｍであり、直径３３ｍｍ以降から最外周の厚さが０．６ｍｍ均一のＡＳ・ＭＯ形状のディスク状の情報記録媒体２０００を、図７と図８の成形機の片側のみの射出ユニットを用い、図８の金型４１を用いて各々以下の条件で作成した。図９と図１０の情報記録媒体２０００は、基板１１、光反射層１２、記録層１３、光透過層１４を有している。
共通ディスク形状
センタークランプ部（チャッキング部）のディスク厚：１．２ｍｍ
センタークランプ部（チャッキング部）の直径 ：３３ｍｍ
ディスク直径 ：１２０ｍｍ
成形条件
金型温度：１３０℃
冷却時間：１６秒
射出速度：平均１６０ｍｍ／ｓｅｃ
【００４３】
実施例２
ディスク形状と慣性モーメントの関係を計算したのが下の表２である。
【表２】

なお、上記表２においては単位系が重量単位系となっている。ＳＩ単位系であれば、
Ｉ＝ｍｒ^２［ｋｇ・ｍ^２］
となる。重量単位系では質量ｍは
ｍ＝Ｗ／ｇ
なので、慣性モーメントは、
Ｉ＝（Ｗ／ｇ）ｒ^２＝｛（ｋｇｆ）／（ｍ／ｓ^２）｝・ｍ^２＝ｋｇｆ・ｓ^２・ｍ
となる（ｓｅｃ＝ｓ）。
テーパー形状としては、直径が１２ｃｍのディスクの最外周の厚さが０．６ｍｍであり、慣性モーメントの単位はｋｇｆ・ｓｅｃ² ・ｍ
表２よりも明らかの様に、ディスクの重量が軽いほど慣性モーメントは少ないが、テーパー形状のディスクの慣性モーメントは１．２ｍｍの均一厚さのディスクの慣性モーメントの６１．５％しかないことが解る。これらのディスクの重量比は７４．８％であり、慣性モーメントの比は、より小さくなることが解る。
【００４４】
実施例３
ディスク構造を、図３の３層のサンドイッチ構造で且つテーパー構造のディスクと、０．８ｔ（０．８ｍｍ厚）のＡＳ・ＭＯ構造のサンドイッチ３層ディスクを作成して、ディスク形状による変位と荷重の関係を測定したのが、下の表３である。
尚、３層構造のコア層は、帝人化成株式会社製のポリカーボネート樹脂に、アセチレンブラック５％にウィスカー３０％を添加した樹脂で、スキン層はポリカ系の吸水率０．１５％の帝人化成株式会社製のＳＴ−３０００樹脂を図７の２色成形機により作成した。このディスクをサンタークランプして、図１３に示す測定系でディスクの外周半径５８ｍｍに変位量を与えこの時の最大荷重を測定したのが、次の表３である。
図１３の測定系は、ロードセル４０００、変位測定系４００１、レーザ４００２、ターンテーブル４００３を有する。
【表３】

これらの結果より、ディスクの剛性はサンドイッチテーパー構造のディスクはコア層の剛性に応じた高い値を示し、従来の透明ディスク１．２ｍｍよりも剛性のあるディスクが得られた。
【００４５】
実施例４：樹脂比重の違いによるディスク重量の違い
樹脂の比重の違いにより同じ構造であっても、成形ディスクの重量は軽くなり剛性があり比重の軽いアモルファスポリオレフィン樹脂を用いた上記基板を作成し、比較例として従来光ディスク一般に使用されているポリカーボネート樹脂と比較した。
使用した樹脂は表１のゼオネックス樹脂ＺＥＯＮＥＸＥ−４８Ｒとポリカーボネート樹脂ＡＤ−５５０３であり、これらから得られたディスクの重量は、以下の表４である。
【表４】

表４に記載の様にゼオネックス樹脂とポリカ樹脂の比重の違いだけで１４％も軽量化が図れ、さらにテーパー形状では従来のＣＤ等の光ディスクに使用されるポリカ樹脂に比べ３３．３％軽量化が図れる。表１にあるように曲げ弾性率はポリカと同等である。
【００４６】
本発明では、ディスクの断面をチャッキング部は１．２ｍｍのフラットで信号部を順次テーパー構造を採る事により１．２ｍｍ単体よりも軽く剛性のある高速回転時のイナーシャの少ないディスクが得られスピンドルにかかる負担が軽減し消費電力の少ないドライブの設計が可能となった。
さらにサンドイッチ構造を採る事により剛性が向上し記録膜の成膜応力や温度湿度の環境下での応力変形に強いディスクが得られ、高ＮＡディスク様に焦点深度の浅い光学系のディスクシステムでもプラスチックディスクが適用できるようになった。プラスチック基板の材質を比重の軽い樹脂を用いると構造は同じであっても、さらに軽量化が図られる。信号部と反対側の面のディスクチャッキング部より外側からディスク最外周部にかけてディスク厚が順次薄くなるテーパー構造を採る事により、軽く剛性があって慣性モーメントが少なく回転開始時のイナーシャが低減され消費電力が少なくてすむ。
【００４７】
【発明の効果】
以上説明したように、本発明によれば、剛性を維持して軽量化を図ることができる。
【図面の簡単な説明】
【図１】 本発明のディスク状の情報記録媒体の好ましい実施の形態を示す斜視図。
【図２】 図１の情報記録媒体のＦ−Ｆにおける断面図。
【図３】 図１の情報記録媒体の別の断面構造例を示す図。
【図４】 情報記録媒体の参考例を示す斜視図。
【図５】 図４の情報記録媒体のＡ−Ａにおける断面図。
【図６】 図４の情報記録媒体のＢ−Ｂにおける断面図。
【図７】 本発明の情報記録媒体を成形する場合の成形機の一例を示す図。
【図８】 図７の成形機に取り付けられる金型部の構造例を示す図。
【図９】 比較例として示すアドバンスト・ストレージ・光磁気ディスク（情報記録媒体）を示す斜視図。
【図１０】 図９の情報記録媒体のＣ−Ｃにおける断面図。
【図１１】 振動解析測定フローチャートを示す図。
【図１２】 振動モードの例を示す図。
【図１３】 ディスク変位量と荷重の測定系の例を示す図。
【図１４】 従来の情報記録媒体の構造例を示す図。
【符号の説明】
１，１００・・・ディスク状の情報記録媒体、２，１１・・・基板、２Ｂ，１１Ｂ・・・他方の面（テーパー面）、３，１２・・・光反射層、４，１３・・・記録層、５，１４・・・光透過層、６・・・凸形状部分（チャッキング部）、１５・・・コア層、１６，１７・・・表層、１０１・・・基板、１１０・・・リブ[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a disk-shaped information recording medium for recording various information signals such as an audio signal and an image signal, and more specifically, a surface opposite to a surface on which an information signal is recorded is clamped on a drive. From the end of the section to the outermost circumference of the information recording medium, the thickness of the information recording medium is gradually reduced to a tapered structure.ThingsTherefore, the rigidity of the information recording medium is maintained to reduce the weight, and the internal loss of the information recording medium itself is increased by the type and composition of the resin and the multilayer structure to suppress resonance.,CircleReduce the moment of inertia of the board-shaped plastic substrate, Reduce the inertia (inertia) at the start of rotation of the information recording mediumThe present invention relates to an information recording medium that reduces a load applied to a rotating spindle and reduces power consumption of a drive system.
[0002]
[Prior art]
As a medium for recording various information for audio, video, and the like, a disk-shaped optical recording medium and a magnetic recording medium are known. As these recording media, there are a phase change type optical disk in which information signals are written in an uneven shape by embossed pits and grooves, a magneto-optical disk using the magneto-optical effect of a recording film, a magnetic disk for magnetically writing a signal, etc. .
[0003]
As a method of forming a recording layer for information signals having fine irregularities such as phase pits and pregrooves on which data information, tracking servo signals, etc. are recorded, injection molding of a plastic substrate is generally performed today. It has been broken. That is, an information signal is transferred from the stamper when the disk-shaped information recording medium is formed using an injection molding machine, a mold, and a stamper.
[0004]
In the formation of a conventional disc-shaped information recording medium (hereinafter also referred to as a disc) such as a CD (optical disc called a compact disc) or a DVD (optical disc called a digital versatile disc or a digital video disc), light is transmitted through the thickness of the disc. In order to read the signal, the substrate of the disk needs to be flat and close to glass and optically transparent, and be a resin with good fluidity to transfer a micro uneven signal.
[0005]
In order to obtain such a disk substrate by injection molding, the resin is injected into the mold cavity as various internal stresses generated in each process of resin melting, injection filling into the mold, and cooling solidification. That is, stress is generated due to friction with the mold when the resin is filled at the stage, pressure and temperature during injection, and the like.
Stress relaxation within a certain period of time from cooling to solidification reduces the internal stress of the substrate, but most of it is not relaxed until solidification and remains as residual stress in the substrate, which causes light birefringence and waviness, etc. This causes a skew (SKEW).
Methods for reducing these internal stresses have been devised in various fields such as molding machines, molds, molding techniques and resins, and there are many patents and literatures.
[0006]
[Problems to be solved by the invention]
However, the method of increasing the internal loss of the substrate to improve the resonance characteristics of the disk itself and improve the rigidity is not solved by these molding machines and molding techniques, but is caused by the disk structure and the polymer structure inherent to the resin. Therefore, the thickness of the disk such as the above-mentioned disk CD or DVD such as a disk substrate having a uniform thickness and having a small thickness of moment, maintaining an optical characteristic, a large internal loss and a light rigidity. The conventional structure of recording and reproducing signals through the above cannot satisfy all of them, and it has been difficult to improve the polymer.
As a means for solving this problem, the high NA disk has the multi-layer sandwich structure invented by the present inventors, but the disk structure has a conventional shape and does not necessarily achieve light weight, rigidity and internal loss.
[0007]
  With higher density, especially higher NA (numerical aperture), the spot diameter of light is reduced more than that used for discs such as CDs and DVDs. Because of the closeness, tolerances such as warping and waviness of the disk substrate are reduced. This is also apparent from the relationship between the lens NA and the disk thickness and the relationship between wavelength and NA.
f = D / 2NA> WD f: Focal length of lens
                            D: Effective diameter of objective lens
                          NA: Numerical aperture of the objective lens
                          WD: Working distance of objective lens
Depth of focus∝λ / (NA) ²
SKEW tolerance∝λ / (NA) ³
Thickness tolerance∝λ / (NA) ⁴
Disc strength∝ (t) ³
        (T: thickness)
[0008]
The relationship between NA and disk thickness is obtained from the above relational expression as follows.
When NA = 0.5 Disc thickness = 1.2mm (CD)
NA = 0.6 Disc thickness = 0.6mm (DVD)
When NA = 0.75 Disc thickness = 0.3 mm
When NA = 0.85 Disc thickness = 0.1mm
In addition, the strength of the disc is proportional to the cube of the thickness, and as the recording density increases, the mechanical properties such as bending strength become worse as the disc becomes thinner. Furthermore, in the environment of heat, film stress and temperature / humidity during film formation, bimetal deformation due to moisture absorption tends to occur remarkably in single-sided signal optical recording media, and it is virtually impossible to use optically transparent single substance. Sony has announced a disk system that records and reproduces signals from the substrate surface opposite to that of a conventional disk.
[0009]
As these high NA high density disk substrates, in addition to the use of optically transparent resin alone found in conventional disks such as CD and DVD, the inventor has already applied for a patent to form a skin layer by sandwich molding. Two-color simultaneous molding or core-back or core-rotating two-color molding method in which a conventional optical resin with good fluidity and a two-layer or three-layer structure with improved resonance characteristics and rigidity on the core layer are mounted on two injection units There is a method of forming a substrate.
[0010]
However, in any of these molding methods, the disk shape is bonded to a uniform 1.2 mm or 0.6 mm plate thickness, or the AS / MO (advanced storage / magneto-optical disk) patented by the present inventors. There is a disc having a structure in which the thickness of the disc clamp portion is 1.2 mm and the thickness of the information signal portion is 0.6 mm. Characteristics such as vibration characteristics and rigidity are inferior to those of a single disk having a thickness of 1.2 mm.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an information recording medium that solves the above-described problems and can reduce the weight while maintaining rigidity.
[0011]
[Means for Solving the Problems]
  The invention of claim 1 is an information recording medium for recording and reproducing an information signal, wherein at least a recording layer for recording the information signal and a light transmission layer are sequentially formed on a disk-shaped substrate. A chucking portion for chucking at the center, opposite to the side on which the recording layer on which the information signal is recorded and reproduced by the incidence of light from the light transmission layer side The disc-shaped substrate side of the disc-shaped substrate is gradually thinner from the end portion of the chucking portion toward the outer peripheral portion of the disc-shaped substrate.,Formed in a tapered shape,Or having a tapered structure,At least the recording area of one surface on which a recording layer on which light is incident from the light transmission layer side to record and reproduce the information signal is formed is substantially planar.And a disc-like substrate having a disc-like convex portion of 0.1 mm ± 0.05 mm inside the information signal start position on the light transmission layer side of the disc-like substrate. An optically transparent resin sheet having a thickness of 0.1 mm ± 0.05 mm that fits into a disk-shaped convex portion is laminated and bonded.This is an information recording medium characterized by the above.
  Claim 1Or 2In this invention, the side of the substrate opposite to the side on which the recording layer is formed is formed in a taper shape so that it gradually becomes thinner from the end portion of the chucking portion toward the outer peripheral portion of the substrate.Or have a tapered structureing.
  As a result, it is lighter and has the same rigidity as the board that is formed from the inner circumference side to the outer circumference side with the same thickness, and reduces the inertia and moment of inertia at the start of rotation. This reduces the burden on the spindle of the motor that attempts to rotate the information recording medium, and reduces power consumption.
[0012]
According to a second aspect of the present invention, in the information recording medium according to the first aspect, the thickness of the chucking portion of the disk-shaped substrate is 1.2 mm ± 0.1 mm, and the disk-shaped substrate has a thickness of 1.2 mm ± 0.1 mm. The thickness of the outer periphery is 0.6 mm ± 0.2 mm.
As a result, the thickness of the clamp part was 1.2 ± 0.1 mm except for compatibility with current discs such as CDs, and the outer peripheral part thickness was 0.6 ± 0.2 mm. This is because, in consideration of stress deformation during film formation and disk deformation in a temperature and humidity environment as well as productivity, if the thickness is smaller than this, the deformation becomes large.
[0013]
According to a third aspect of the present invention, in the information recording medium according to the first aspect, a disk shape of 0.1 mm ± 0.05 mm is provided on the inner side of the information signal start position on the light transmission layer side of the disk-shaped substrate. It has a convex-shaped part. As shown in the drawing, it serves to keep the eccentricity within 50 microns at the maximum together with the center guide of the sheet when a transparent sheet (100 μm) is laminated and a signal is transferred to the sheet and a recording film is attached to make a two-layer disc. It is the shape for
[0014]
According to a fourth aspect of the present invention, in the information recording medium according to the first aspect, the disk-shaped substrate is composed of a plurality of layers, and the surface layer resin on which the information signal is recorded has a water absorption rate. 0.3% or less.
If the water absorption rate of the resin on the surface layer on the light transmission layer side is 0.3% or less, there is little water absorption deformation, and warpage deformation in the high-density information recording medium can be suppressed within the standard.
If the water absorption rate of the surface layer exceeds 0.3%, a recording layer or the like is formed on the recording layer side of the substrate. However, in the environment of temperature and humidity other than the stress at the time of film formation, the substrate Water absorption and dehydration are carried out from the surface, and deformation such as warping continues until equilibrium is reached in the storage and use environment, resulting in warpage deformation exceeding the standard.
[0015]
According to a fifth aspect of the present invention, in the information recording medium according to the third aspect, the disk-shaped substrate has an optically transparent thickness of 0.1 mm ± 0.05 mm across the disk-shaped convex portion. Resin sheets are laminated and bonded.
This prevents the objective lens from colliding with the disc because it is the same height (thickness) as the disc clamp when the sheets are bonded together.
[0018]
In the present invention, the resin core layer constituting the substrate is preferably made of a rigid resin or resin composition having a large internal loss and a flexural modulus of 25000 kgf or more.
The reason why the flexural modulus is 25000 kgf or more is that the skin layer that performs signal transfer with a transparent resin including the embodiment has a fluidity resin with a flexural modulus of 24000 kgf or less, and the core layer has a flexural modulus greater than that of the skin layer. Since it is necessary to ensure rigidity and heat resistance, it is 25000 kgf. Incidentally, the flexural modulus of a single resin without a filler is as follows.
Skin layer related resin
Polycarbonate resin AD-5503 24000kgf / cm²
ZEONEX resin E28R 23,000-25000kgf / cm²
Core layer resin
Polycarbonate resin ST-3000 28500kgf / cm²
ZEONEX resin L-6 (prototype grade) 27000kgf / cm²
[0019]
  In the present invention, in order to reduce the weight while maintaining the rigidity, the disc clamping portion which is the information recording medium on the opposite side on which the information signal is recorded is 1.2 mm like the conventional disc, and the disc is viewed from the outside of the clamping portion. The outermost circumference of the taper is 0.4 mm to 0.6 mm, and during this period, the taper structure is made thinner gradually toward the outer circumference.To makeTo reduce rigidity and weight,CircleReduce the moment of inertia of the board-shaped plastic substrateComb, reduce inertia at the start of disk rotationCan do. TheFurther, as a means for suppressing resonance, a material having high internal loss and rigidity can be formed into a multilayer sandwich structure.
[0020]
In addition, in the case of a resin alone having rigidity and a large internal loss, a multi-layer sandwich structure is not required, so by obtaining a disk substrate with a conventional disk molding machine, transfer of fine signals and rigidity and weight reduction can be achieved, An excellent durable recording medium without warping (SKEW) or sink marks can be obtained.
[0021]
  In addition to the structure described so far, the rigidity according to the mixing ratio of the resin is ensured by mixing the disk molding material with a highly rigid resin or adding a filler, and the internal loss is the same. . With these disc structuresTo yenLess moment of inertia of board-shaped plastic substrateAnd reduce the inertia at the start of disk rotation.I can do it. In addition, plastic substrates have been used as conventional disc materials by selecting a resin that is easily deformed by heat and moisture absorption in the manufacturing process, user's usage environment, and storage environment, but whose surface layer (skin layer) has low water absorption and high heat deformation. For example, the moisture absorption deformation, heat resistance and rigidity of the polycarbonate resin can be improved.
[0022]
  In the present invention, the surface layer of the substrate is a resin having a water absorption of 0.3% or less. More preferably 0.15%. Thereby, when the water absorption is 0.3 or less, the water absorption deformation is small, for example, a digital versatile disk (DVD: high-density information recording medium) has a warp deformation within 0.4 degrees by the standard.ReEven with a bumped structure, it can be suppressed to disk deformation within 0.4 degrees.
[0023]
For this reason, even if water absorption deformation occurs, for example, a water absorption rate of 0.3% or less, more preferably 0.15% or less is required to keep the warp deformation (radial skew) angle within 0.4 degrees. . However, if the water absorption rate of the surface layer exceeds 0.3%, a recording film and a protective film are formed on the recording side of the disk, and water is absorbed from the surface of the disk in an environment of temperature and humidity in addition to the stress at the time of film formation. Dehydration is performed, and deformation such as warping continues until equilibrium is achieved in the storage and use environment, resulting in warpage deformation exceeding the standard, and recording / reproduction becomes impossible.
[0024]
Under this different environment, the recording film and the protective film on the opposite side of the recording film have different water absorption rates from the substrate material (generally difficult to absorb water), and the signal side warps in a concave shape at the time of water absorption. Conversely, it deforms into a convex shape when dried. In particular, during a drive operation, a rapid change is likely to occur since the temperature inside the machine is high and the humidity is low, and a focus error is likely to occur if the signal cannot be read due to deformation of the disk.
[0025]
Further, a resin having a surface layer water absorption of 0.15% or less is most preferable. As a result, even when the water absorption warp deformation angle is set to 0.4 degrees, if the disk warpage angle at the time of water absorption equilibrium is 0 degrees, the water absorption deformation is within 0.4 degrees. Considering the storage environment, etc. 0.1% disk that absorbs less water and has substantially no water absorption. It only needs to suppress deformation during manufacturing, and it is not necessary to consider water absorption deformation in the environment of use, so the system margin increases. .
[0026]
In the present invention, the material of the substrate has a multilayer structure of two or more layers in which the internal loss is increased in the core layer as means other than the taper structure in order to suppress the resonance phenomenon that occurs when the information recording medium is rotated. Accordingly, the resonance phenomenon can be reliably suppressed by repeating the attenuation every time the vibration wave generated when the information recording medium is rotated at high speed passes through the composite resin layer constituting the substrate.
[0027]
In the present invention, the material of the substrate is composed of a composite of two or more kinds of resins, and one or more of them are resin composites composed of a resin having rigidity and heat resistance. As a result of relatively high rigidity and heat resistance depending on the resin mixing ratio, not only warping deformation during manufacturing is suppressed, but also the system margin is increased by reducing warping deformation in the storage and use environment.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms.
[0029]
FIG. 1 shows a preferred embodiment of the information recording medium of the present invention, and FIG. 2 is a sectional view taken along line FF of the information recording medium 1 of FIG.
This disk-shaped information recording medium (disc-shaped information recording medium) 1 has a center hole H having a predetermined size. As shown in FIGS. 1 and 2, the information recording medium 1 is a disk having a so-called taper structure. The information recording medium 1 has a substrate 2, a light reflecting layer 3, a recording layer 4, a light transmitting layer 5, and a convex portion 6.
The substrate 2 can be made of a resin such as polycarbonate having translucency. The light reflecting layer 3 is formed on the one surface 2 </ b> A side of the substrate 2. The light reflecting layer 3 is made of a film that reflects light, such as aluminum. The recording layer 4 is formed by laminating on the light reflecting layer 3. The recording layer 4 is formed by laminating a light transmission layer 5. The light reflecting layer 3 and the recording layer 4 are portions for recording the uneven information signal S. The uneven information signal S forms a fine uneven pattern row such as pits or pregrooves.
[0030]
The light reflection layer 3, the recording layer 4, and the light transmission layer 5 are formed on the outer peripheral portion of the convex portion 6 of the substrate 2. The light transmission layer 5 guides the laser light L to the recording layer 4 side through the laser light L condensed through the lens LS. The laser beam L is used to record the uneven information signal S or to reproduce the already recorded information signal S.
As a disc-shaped information recording medium, for example, an optical information recording medium for recording audio, video, or other various information, there are various optical information recording media that perform recording or reproduction by light irradiation.
For example, the disk-shaped information recording medium includes a compact disk (CD: trade name), a rewritable magneto-optical disk, a phase change disk, and the like. The information recording layer of these disk-shaped information recording media includes data information, tracking. It is necessary to form a pattern array of fine irregularities such as pits and pregrooves so that servo signals can be recorded.
The substrate 2 may be a single resin conventionally used such as polycarbonate as described above, or a sandwich structure as shown in FIG.
[0031]
  FIG. 3 shows another example of the cross-sectional structure at FF of the information recording medium 1 of FIG. 1, and the substrate 11 has three layers of a surface layer (skin layer) 16, a core layer 15, and a surface layer (skin layer) 17. It consists of On the surface layer 17, a light reflection layer 12, a recording layer 13, and a light transmission layer 14 are laminated. An uneven information signal S is formed at the recording layer 13 and the light reflecting layer 12.
  The substrate 11 employs a multilayer sandwich structure, and the core layer 15 isIt is made of a resin or resin composition having high rigidity and internal loss. By doing in this way, the rigidity and internal loss of the board | substrate 11 can be improved, and the following examples are employ | adopted as this resin or resin composition.
  Examples of resin or resin composition
  For polycarbonate resin
                                                    Flexural modulus tan δ
                                                    kgf / cm²
  Polycarbonate resin / acrylic resin = 50:50 ... 26000 0.059
  Polycarbonate / acrylic = 55:45 with 10% graphite added. 42000 0.074
  Comparative example: Polycarbonate resin alone ... 24000 0.004
    The flexural modulus measurement method is ASTM D790.
    Tanδ measurement is JIS K7198
[0032]
  As will be apparent with reference to FIGS. 1, 2 and 3, the greatest feature of the information recording medium 1 is that the other surface 2B side of the substrate 2 or the other surface 11B side of the substrate 11 is tapered. It is that you are.
  The convex portion 6 of the information recording medium 1 in FIG. 2 is a chucking portion. This chucking portion is a portion that attaches the information recording medium 1 to the clamp portion on the spindle side of the motor in a detachable manner. Similarly, the convex portion 6 of the information recording medium 1 in FIG. 3 is also a chucking portion.
  The other surface 2 </ b> B or 11 </ b> B is formed in a tapered shape so as to become thinner gradually from the end portion of the chucking portion which is the convex portion 6 toward the outer peripheral portion of the substrate 2 or 11. That is, the other surface 2B or 11B is a tapered surface when viewed in cross section.
  Thus, by making the other surface 2B or 11B of the substrate 2 a tapered surface, weight reduction is achieved while maintaining rigidity., GroupReduce the moment of inertia of plates 2 and 11Rotate while reducing the inertia at the start of rotation of the substrates 2 and 11The load applied to the rotating spindle can be reduced, and the power consumption of the drive system can be reduced.
  In addition, by providing the surface layers 16 and 17 with respect to the core layer 15 of the substrate 11 as shown in FIG. 3, the internal loss of the substrate 11 itself can be increased to suppress resonance.
[0033]
  FIG.5These are the structural examples of the conventional information recording medium shown in order to compare with FIG. 2 and FIG. 3 which are embodiment of this invention.
  A conventional information recording medium 1000 includes a substrate 1002 also serving as a light transmission layer, a recording layer 1004, a light reflection layer 1003, and the like, and an uneven information signal S is formed. A substrate 1002 also serving as a light transmission layer is a substrate that is optically transparent and has little birefringence, and records / reproduces the information signal S by irradiating the laser beam L from the lens LS. For this reason, the light reflecting layer 1003 and the recording layer 1004 have a laminated arrangement opposite to that of the embodiment of the present invention shown in FIGS.
  The light transmission layer 1005 serves as a protective layer for the corresponding recording layer 1004 and light reflection layer 1003 and does not need to be optically transparent, but is generally coated with an ultraviolet curable resin with a thickness of several μm. Things are used
[0034]
2 and 3, the dimensional description of the embodiment of the present invention is as follows. The thickness L1 of the convex portion 6 (chucking portion) is, for example, 1.2 mm ± 0.1 mm, and the information recording medium The thickness L2 of the outermost periphery of 1 is 0.6 mm ± 2 mm. These thicknesses L1 and L2 are the same in the embodiment of FIG.
Further, the thickness L3 of the convex portion 6, that is, the thickness of the portion inside the information signal start position on the light transmission layer 5 side is a disc-like convex shape of 0.1 mm ± 0.05 mm.
In FIG. 3, the substrate 11 has a structure of two or more layers formed by the core layer 15 and the surface layers 16 and 17, but the resin of the surface layer 17 on the light transmission layer 14 side has a water absorption rate of 0.3. % And preferably the above-mentioned resins and resin compositions having a specific gravity of 1.2 or less.
The light transmission layer 14 is fitted to the convex portion 6 and is an optically transparent resin sheet having a thickness of, for example, 0.1 ± 0.05 mm.
The core layer 15 preferably has a large internal loss and examples of rigid resins and resin compositions having a flexural modulus of, for example, 25000 kgf or more are as follows.

[0035]
  4 to 6, DeDisk-shaped information recording mediumReference exampleIs shown. A cross-sectional view taken along the line AA in the information recording medium 100 is shown in FIG. 5, and a cross-sectional view taken along the line BB is shown in FIG. The information recording medium 100 has a center hole H, and a light reflecting layer 102, a recording layer 103, and a light transmitting layer 104 are sequentially laminated on a substrate 101. An information signal S is recorded on the recording layer 103 and the light transmission layer 104. On the back side of the substrate 101, a plurality of ribs 110 are formed, for example, at equal intervals in the radial direction (radial direction). As shown in FIGS. 5 and 6, a convex portion (chucking portion) 106 is formed on the center hole H side of the substrate 101.
[0036]
  As shown in FIG. 4, a plurality of ribs 110 are formed radially on the back side of the substrate. Although the rib 110 is not visible in FIG. 5, the rib 110 is visible in FIG. That is, the rib 110 protrudes below the substrate 101 and has the same thickness in the radial direction. The thickness L4 of the convex portion 106 shown in FIGS. 5 and 6, that is, the chucking portion is, for example, 1.2 mm ± 0.1 mm. A thickness L5 of the outer peripheral portion of the information recording medium 100 is, for example, 0.6 mm to 0.8 mm.
  In the example of FIGS. 5 and 6, the ribs 110 are radially formed with a uniform thickness along the radial direction R.
  On the other hand, it is also possible to adopt a structure in which the rib 110 becomes thinner gradually from the convex portion 106 toward the outermost peripheral portion.
  By employing the radial rib structure as shown in FIGS. 4 to 6, it is possible to ensure the rigidity and weight of the information recording medium 100., GroupReduce the moment of inertia of the plateComb, reducing inertia at the start of rotation of the information recording medium 100Can.
[0037]
Next, with reference to FIGS. 7 and 8, an example of a molding machine and a mold for producing the above-described information recording medium 1,100 will be described.
FIG. 7 shows a so-called disk molding machine (two-color molding machine) 40. The molding machine 40 includes a mold part 41 and injection units 42 and 43. A hopper 42 </ b> A is provided in the middle of the injection unit 42, and a hopper 43 </ b> A is provided in the middle of the injection unit 43. The mold part 41 is arranged corresponding to the nozzle 45, and the mold part 41 can be detachably held by operating the piston 47 by the mold clamping cylinder 46.
[0038]
FIG. 8 shows an example of the structure of such a mold part 41. The mold part 41 includes a fixed mold 41A and a movable mold 41B. In the fixed mold 41A and the movable mold 41B, resin is injected into the cavity from the injection unit 42 through the sprue 52, whereby the substrate 2 or 101 of the information recording medium 1 or 100 as described above. Can be molded.
At this time, a stamper 53 for forming pits or grooves is disposed in the fixed mold 41A, whereby pits or grooves are simultaneously formed on the substrate of the disk.
In order to form the center hole H of the information recording medium 1 or 100 as described above, the disk substrate 2 (11 or 100) is punched out by a punch 54 having a hydraulic mechanism (not shown) in the mold part 41. It has become.
[0039]
【Example】
  Next, a more specific embodiment of the disc-shaped information recording medium of the present invention will be described.
Material description: Table 1 shows the materials used.
PC: Polycarbonate resin [manufactured by Teijin Chemicals Ltd. Panlite AD-5503, ST-3000]
ZEONEX: amorphous polyolefin resin [Nippon Zeon Corporation E-48R, L-6]
AB: Conductive carbon black [Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.]
W: Whisker[Sakai Kogyo Co., Ltd. Wallace Night: Psytectech NN-4]
[Table 1]

[0040]
  Example 1: Tapered disk
  Disks with the outermost peripheral thickness of 0.6 mm and 0.4 mm were prepared as the taper structure disk (information recording medium) of FIG. 1 with the following disk shape without addition of a filler of polycarbonate resin AD-5503.
  As a comparative example, FIG.4The conventional structure having a uniform thickness of 1.2 mm and the chucking portion (clamping portion) of FIGS. 9 and 10 have a thickness of 1.2 mm and a diameter of 33 mm. .6 mm uniform AS / MO-shaped disc-shaped information recording medium 2000 using the injection unit on only one side of the molding machine of FIGS. 7 and 8 and using the mold 41 of FIG. did. The information recording medium 2000 shown in FIGS. 9 and 10 includes a substrate 11, a light reflection layer 12, a recording layer 13, and a light transmission layer 14.
  Common disc shape
      Center clamp part (chucking part) disc thickness: 1.2 mm
      Center clamp part (chucking part) diameter: 33 mm
      Disc diameter: 120 mm
  Molding condition
      Mold temperature: 130 ° C
      Cooling time: 16 seconds
      Injection speed: average 160mm / sec
[0043]
  Example2
  The relationship between the disk shape and the moment of inertia is calculated in Table 2 below.
[Table 2]

  In Table 2, the unit system is a weight unit system. If SI unit system,
  I = mr²[Kg · m²]
It becomes. In the weight unit system, the mass m is
  m = W / g
So the moment of inertia is
  I = (W / g) r²= {(Kgf) / (m / s²)} ・ M²= Kgf · s²・ M
(Sec = s).
  As the taper shape, the thickness of the outermost periphery of a disk having a diameter of 12 cm is 0.6 mm, and the unit of moment of inertia is kgf · sec.²・ M
  As apparent from Table 2, the smaller the weight of the disk, the smaller the moment of inertia. However, the moment of inertia of the tapered disk is only 61.5% of the moment of inertia of the disk having a uniform thickness of 1.2 mm. I understand. It can be seen that the weight ratio of these disks is 74.8%, and the ratio of the moments of inertia becomes smaller.
[0044]
  Example3
  The disc structure is the three-layer sandwich and taper disc shown in FIG. 3 and the AS / MO sandwich three-layer disc of 0.8t (0.8mm thickness). Table 3 below measured the relationship.
  The core layer with a three-layer structure is a resin made by adding Teijin Kasei Co., Ltd. polycarbonate resin to 5% acetylene black and 30% whisker, and the skin layer is a Teijin Chemicals stock with a polycarbonate water absorption of 0.15%. ST-3000 resin manufactured by company was prepared by the two-color molding machine shown in FIG. This disc is sun clamped and3Table 3 shows the maximum load at this time when the displacement is given to the outer peripheral radius of 58 mm of the disk by the measurement system shown in FIG.
  FIG.3The measurement system includes a load cell 4000, a displacement measurement system 4001, a laser 4002, and a turntable 4003.
[Table 3]

  From these results, the rigidity of the disk of the sandwich taper structure showed a high value corresponding to the rigidity of the core layer, and a disk having rigidity higher than the conventional transparent disk of 1.2 mm was obtained.
[0045]
  Example4: Difference in disc weight due to difference in resin specific gravity
  Even if it has the same structure due to the difference in specific gravity of the resin, the above-mentioned substrate is made using amorphous polyolefin resin that is light and rigid and has a low specific gravity, and a comparatively used polycarbonate resin as a comparative example. Compared with.
  The resins used were ZEONEX resin ZEONEX-48R in Table 1 and polycarbonate resin AD-5503, and the weight of the disc obtained from these was shown in Table 4 below.
[Table 4]

  As shown in Table 4, the difference in specific gravity between ZEONEX resin and polycarbonate resin can be reduced by 14%, and the tapered shape reduces weight by 33.3% compared to the polycarbonate resin used for conventional optical discs such as CDs. Can be planned. As shown in Table 1, the flexural modulus is equivalent to that of polycarbonate.The
[0046]
  In the present invention, the cross-section of the disk has a flat chucking part of 1.2 mm, and the signal part has a tapered structure in order to obtain a disk that is lighter and stiffer than a single unit of 1.2 mm and less inertia during high-speed rotation. The design of a drive that consumes less power and consumes less power is now possible.
  TheIn addition, by adopting a sandwich structure, the rigidity is improved and a disk that is strong against stress deformation under the conditions of film formation stress and temperature and humidity can be obtained. Even in a disk system with a shallow focal depth like a high NA disk Plastic discs can be applied. Even if the structure is the same, the weight of the plastic substrate can be further reduced by using a resin with a low specific gravity.It is done.By adopting a taper structure in which the disc thickness gradually decreases from the outer side of the disc chucking portion on the surface opposite to the signal portion to the outermost peripheral portion of the disc, it is light and rigid.ConventionalThere is little sex momentTimesRollstartInertia is reduced and power consumption is reduced.
[0047]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the weight while maintaining the rigidity.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a preferred embodiment of a disk-shaped information recording medium of the present invention.
2 is a cross-sectional view taken along line FF of the information recording medium in FIG.
3 is a diagram showing another example of a cross-sectional structure of the information recording medium of FIG.
[Fig. 4]AffectionInformation recording mediaReference exampleFIG.
5 is a cross-sectional view taken along line AA of the information recording medium in FIG.
6 is a cross-sectional view taken along line BB of the information recording medium in FIG.
FIG. 7 is a view showing an example of a molding machine for molding the information recording medium of the present invention.
8 is a view showing a structural example of a mold part attached to the molding machine of FIG.
FIG. 9 is a perspective view showing an advanced storage magneto-optical disk (information recording medium) shown as a comparative example.
10 is a cross-sectional view taken along the line CC of the information recording medium in FIG. 9;
FIG. 11 is a diagram showing a vibration analysis measurement flowchart.
FIG. 12 is a diagram showing an example of a vibration mode.
FIG. 13The figure which shows the example of the measurement system of a disk displacement amount and a load.
FIG. 14The figure which shows the structural example of the conventional information recording medium.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,100 ... Disc-shaped information recording medium, 2, 11 ... Substrate, 2B, 11B ... The other surface (tapered surface), 3, 12 ... Light reflection layer, 4, 13,. Recording layer 5, 14 ... Light transmission layer, 6 ... Convex part (chucking part), 15 ... Core layer, 16, 17 ... Surface layer, 101 ... Substrate, 110 ··rib

Claims (4)

An information recording medium for recording and reproducing information signals,
A recording layer for recording at least the information signal and a light transmission layer are sequentially formed on a disc-shaped substrate, and has a chucking portion for chucking in the center,
The other surface of the disk-shaped substrate opposite to the one surface on which the recording layer on which light is incident from the light transmission layer side to record and reproduce the information signal is the chucking surface. It is formed in a tapered shape that becomes thinner gradually from the end part of the part toward the outer periphery of the disk-shaped substrate,
Recording of the information signal light is incident from the light transmission layer side, at least a recording area of one surface of the recording layer which reproduction is performed is formed Ri formed by the substantially flat,
On the inner side of the information signal start position on the light transmission layer side of the disk-shaped substrate, it has a disc-shaped convex portion of 0.1 mm ± 0.05 mm,
An information recording medium in which an optically transparent resin sheet having a thickness of 0.1 mm ± 0.05 mm that is fitted to the disk-shaped convex portion is laminated and bonded to the disk-shaped substrate . An information recording medium for recording and reproducing information signals,
A recording layer for recording at least the information signal and a light transmission layer are sequentially formed on a disc-shaped substrate, and has a chucking portion for chucking in the center,
The other surface of the disk-shaped substrate opposite to the one surface on which the recording layer on which light is incident from the light transmission layer side to record and reproduce the information signal is the chucking surface. Having a taper structure that gradually decreases from the end of the portion toward the outer periphery of the disk-shaped substrate,
Recording of the information signal light is incident from the light transmission layer side, at least a recording area of one surface of the recording layer which reproduction is performed is formed Ri formed by the substantially flat,
On the inner side of the information signal start position on the light transmission layer side of the disk-shaped substrate, it has a disc-shaped convex portion of 0.1 mm ± 0.05 mm,
An optically transparent resin sheet having a thickness of 0.1 mm ± 0.05 mm that fits into the disk-shaped convex portion is laminated and bonded to the disk-shaped substrate.
Information recording medium. The thickness of the chucking portion of the disc-shaped substrate, a 1.2 mm ± 0.1 mm, according to claim 1 thickness of the outer peripheral portion of the disk-shaped substrate is 0.6 mm ± 0.2 mm Or the information recording medium of 2. Said disk-like substrate, the above light transmission layer side of the surface layer of the resin which the information signal is composed of a plurality of layers are recorded, in any one of claims 1 to 3 a water absorption rate of 0.3% or less The information recording medium described.

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