JPH023131A - Production of optical disk - Google Patents
Production of optical diskInfo
- Publication number
- JPH023131A JPH023131A JP63148112A JP14811288A JPH023131A JP H023131 A JPH023131 A JP H023131A JP 63148112 A JP63148112 A JP 63148112A JP 14811288 A JP14811288 A JP 14811288A JP H023131 A JPH023131 A JP H023131A
- Authority
- JP
- Japan
- Prior art keywords
- recording medium
- manufacturing
- disk
- recording
- optical disk
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 19
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 8
- 239000000853 adhesive Substances 0.000 claims description 4
- 230000001070 adhesive effect Effects 0.000 claims description 4
- 230000007704 transition Effects 0.000 claims description 3
- 239000004576 sand Substances 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims 1
- 239000000956 alloy Substances 0.000 claims 1
- 229910045601 alloy Inorganic materials 0.000 claims 1
- 150000004770 chalcogenides Chemical class 0.000 claims 1
- 238000002844 melting Methods 0.000 claims 1
- 230000008018 melting Effects 0.000 claims 1
- 229910052761 rare earth metal Inorganic materials 0.000 claims 1
- 238000004544 sputter deposition Methods 0.000 abstract description 3
- 239000011521 glass Substances 0.000 abstract description 2
- 239000000758 substrate Substances 0.000 abstract description 2
- 239000010408 film Substances 0.000 description 13
- 230000000694 effects Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012782 phase change material Substances 0.000 description 2
- 229910000808 amorphous metal alloy Inorganic materials 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、光ディスクの製造方法に係り、特に光ディス
クの熱安定性の向上、ひいてはディスクの信頼性向上に
好適な光ディスクの製造方法に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an optical disc, and particularly to a method of manufacturing an optical disc suitable for improving the thermal stability of an optical disc and, by extension, improving the reliability of the disc.
近年の高度情報化社会の進展に伴い、高密度大容量なフ
ァイルメモリに対するニーズが高まっており、これに応
えるメモリとして光ディスクが注目されている。一方、
光ディスクはコンパクトディスク（ＣＤ）が民生用とし
て普及しつつあり。With the recent development of an advanced information society, the need for high-density, large-capacity file memory is increasing, and optical disks are attracting attention as a memory that can meet this demand. on the other hand,
Among optical discs, compact discs (CDs) are becoming popular for consumer use.
また情報記録用ディスクとしてライトワンスディスクが
実用化の段階に入ってきている。しかしながらこれらの
ディスクは、記録した情報を消去して再び記録すること
はできない、そこでこの欠点を克服した光ディスクとし
て、光磁気ディスクや相変化型のディスクが注目されて
おり、実用化に向けて各所で研究開発が活発に行なわれ
ている。Also, write-once disks are entering the stage of practical use as disks for recording information. However, the recorded information cannot be erased and re-recorded on these disks, so magneto-optical disks and phase change disks are attracting attention as optical disks that overcome this drawback, and are being studied in various places for practical use. Research and development is being actively carried out.
これらは光ディスクは、レーザー光からの熱により記録
や消去を行い、しかも用いている記録媒体が非晶質の簿
膜であるので熱的安定性に欠けるのでディスク実用化に
おいて大きな問題となっていた。These optical discs record and erase information using heat from laser light, and the recording medium used is an amorphous film, which lacks thermal stability, which has been a major problem in putting discs into practical use. .
上記従来技術は、非晶質膜の結晶化抑制に対しての配慮
しかなされておらず、媒体の加熱により成膜時の内部応
力や原子の再配列、さらには未反応材料の反応等が生じ
る等の膜の構造緩和に対する配慮がなされていなかった
。そのため、ディスクの初期特性が安定しなかったり記
録・消去を繰り返すことにより特性が変動する為情報保
持時間が短く、かつ信頼性に欠けるという問題があった
。The above conventional technology only takes into consideration the suppression of crystallization of an amorphous film, and heating of the medium causes internal stress during film formation, rearrangement of atoms, and even reactions of unreacted materials. No consideration was given to relaxing the structure of the film. Therefore, the initial characteristics of the disk are not stable or the characteristics fluctuate due to repeated recording and erasing, resulting in a short information retention time and a lack of reliability.
本発明の目的は、ディスク製造時の構造緩和等の不安定
成分によるディスク特性の変動をなくすとともに、情報
の保持寿命を伸ばすとともに高信頼性を有する光ディス
クの生産を可能にする製造方法を提供することにある。An object of the present invention is to provide a manufacturing method that eliminates fluctuations in disk characteristics due to unstable components such as structural relaxation during disk manufacturing, extends information retention life, and makes it possible to produce optical disks with high reliability. There is a particular thing.
〔ｌｌ１１題を解決するための手段〕
上記目的は、情報記録媒体を熱処理することにより達成
される。[Means for Solving Problem ll11] The above object is achieved by heat-treating the information recording medium.
記録媒体をあらかじめ熱処理することにより、ディスク
中に残留している不安定成分、例えば、内部応力や不安
定な原子配列や結合状態に起因する構造緩和が解消でき
、媒体を準安定状態にできるので、安定した初期特性を
有するディスクが得られるとともに、記録・消去の繰り
返しによる特性変動の問題が解決でき、長い情報保持寿
命でかつ安定性に優れた光ディスクを得ることができる
。By heat-treating the recording medium in advance, unstable components remaining in the disk, such as structural relaxation caused by internal stress or unstable atomic arrangement or bonding state, can be eliminated, and the medium can be made into a metastable state. Therefore, a disk having stable initial characteristics can be obtained, the problem of characteristic fluctuation due to repeated recording and erasing can be solved, and an optical disk with a long information retention life and excellent stability can be obtained.
以下、本発明の詳細を実施例１〜３を用いて詳細に説明
する。Hereinafter, the details of the present invention will be explained in detail using Examples 1 to 3.
［実施例１］
作製した光ディスクの断面構造の模式図を第１図に示す
。このような光ディスクは以下に述べる手順で作製され
る。まず、ディスク表面に案内溝を有するガラスやプラ
スチックの基板１上に、スパッタリング法により窒化シ
リコンの下地膜２を７５０人の膜厚に形成した。この膜
の屈折率はｎ＝２．３であった。ひきつづき、記録膜３
としてＴｂｚａ、ａＦｅｅｔ、６Ｃｏｘｚ、ｏＮｂｓ非
晶質合金薄膜をスパッタリング法で形成した８その時の
膜厚は１０００人である。最後に、保護膜４とし２窒化
シリコン膜を２０００人の膜厚に形成し、光磁気ディス
クを形成した。このディスクに用いた記録膜の磁気・磁
気光学特性は、カー（Ｋｅｒｒ）回転角：θ翼＝０．３
４°、保磁カニ Ｈｃ”１２ｋｏｅ、キュリー温度：
Ｔｃ”２００℃、そして補償温度： Ｔｃｏｍｐ＝９０
℃であった。[Example 1] A schematic diagram of the cross-sectional structure of the produced optical disc is shown in FIG. Such an optical disc is manufactured by the procedure described below. First, a silicon nitride base film 2 was formed to a thickness of 750 mm on a glass or plastic substrate 1 having guide grooves on the disk surface by sputtering. The refractive index of this film was n=2.3. Continuing, recording film 3
A Tbza, aFeet, 6Coxz, and oNbs amorphous alloy thin film was formed by a sputtering method, and the film thickness at that time was 1000 mm. Finally, a di-silicon nitride film was formed as a protective film 4 to a thickness of 2,000 mm to form a magneto-optical disk. The magnetic and magneto-optical properties of the recording film used in this disk are as follows: Kerr rotation angle: θ blade = 0.3
4°, coercive crab Hc”12koe, Curie temperature:
Tc”200℃, and compensation temperature: Tcomp=90
It was ℃.
このディスクを次に熱処理した。その手法は。This disk was then heat treated. What is the method?
無磁場中で熱処理、及びディスク面に対して１４ｋｏｅ
ｌｄｉ界を印加した状態で行なった。その時の熱処理条
件は、温度１５０℃にて１０分間行なった。Heat treated in no magnetic field and 14koe on the disk surface
The experiment was conducted with an Ldi field applied. The heat treatment conditions at that time were a temperature of 150° C. for 10 minutes.
このようにして処理したディスクの特性を測定した。す
なわち消去／記Ｄ／再生を繰り返した時の搬送波対雑音
化： Ｃ／Ｎの変化及び２００℃に２加熱したときの垂
ｒｆｉ、磁気異方性エネルギーＫｕの経時変化にて評価
した。その結果を第２図及び第３図にそれぞれ示す。そ
して、本発明の効果を熱処理を施していないディスクと
比較した。その結果、Ｃ／Ｎでみても（第２図）垂直磁
気異方性エネルギー：Ｋｕで比べても（第３図）、いず
れも熱処理を施すことにより、Ｃ／Ｎ及びＫｕの変動を
大きく抑えることができることがわかる。また、無磁場
中での熱処理と磁場中での熱処理とを比へると、磁場中
での熱処理の方がＣ／Ｎ及びＫｕの変動が小さい。また
、ディスク作製初期のディスク間Ｃ／Ｎの変動は、従来
の未処理では±４０％あったのに対し、熱処理を行うと
±１％以内と著しく安定したＣ／Ｎ値を示した。この効
果は、記録膜材料によらず、また作製方法によらずみら
れるものである、
次に、この熱処理を行う温度を１５０℃から２５０℃と
キュリー温度以上の温度にて熱処理を行ない、先の実施
例と同様、記録／再生／消去を繰り返した時のＣ／Ｎの
変化を第４図に示した。The characteristics of the disk thus treated were measured. That is, carrier wave to noise conversion when erasing/recording/reproducing was repeated: Evaluation was made based on the change in C/N and the change over time in the vertical rfi and magnetic anisotropy energy Ku when heated to 200°C. The results are shown in FIGS. 2 and 3, respectively. Then, the effects of the present invention were compared with a disk that was not subjected to heat treatment. As a result, both in terms of C/N (Fig. 2) and perpendicular magnetic anisotropy energy (Ku) (Fig. 3), by applying heat treatment, fluctuations in C/N and Ku can be greatly suppressed. It turns out that you can do it. Further, when comparing heat treatment in a non-magnetic field and heat treatment in a magnetic field, the variation in C/N and Ku is smaller in the heat treatment in a magnetic field. Furthermore, the variation in C/N between disks at the initial stage of disk production was ±40% in the conventional untreated case, but when heat treated, the C/N value was extremely stable within ±1%. This effect can be seen regardless of the recording film material or manufacturing method.Next, heat treatment is performed at a temperature of 150°C to 250°C, which is higher than the Curie temperature. As in the example, FIG. 4 shows the change in C/N when recording/reproducing/erasing is repeated.
比較例は熱処理を行なっていないディスクである。The comparative example is a disk that has not been subjected to heat treatment.
その結果、キュリー温度以上で熱処理を行った実施例は
、未処理の従来例よりＣ／Ｎの変化を小さくすることが
できるが、キュリー温度以下で熱処理した実施例よりＣ
／Ｎの変化は大きい、このことがらキュリー温度以下で
熱処理を行う方がよすＣ／Ｈの変化を大きく抑制できる
ことがわがった。As a result, the examples heat-treated above the Curie temperature can have a smaller change in C/N than the untreated conventional examples, but the C/N changes are smaller than those of the examples heat-treated below the Curie temperature.
The change in C/N is large, and it has been found that it is better to perform the heat treatment at a temperature below the Curie temperature, and the change in C/H can be largely suppressed.
また、ディスクの熱処理を行うことにより、最小記録レ
ーザー出力も０ 、５ ｍ Ｗ程下げられるので、本発
明は記録感度向上にも有効である。Furthermore, by heat-treating the disk, the minimum recording laser output can be lowered by about 0.5 mW, so the present invention is also effective in improving recording sensitivity.
［実施例２］
本実施例では、実施例１と同様の手法で作製したディス
ク２枚を、接着剤により密着貼り合せによって組立てる
か、２枚のディスクをスペーサを介してエアーサンドイ
ンチ法により組み立てを行ない、その後ディスクを１４
０℃で１０分間ベーキングを行なって作製した場合であ
る。[Example 2] In this example, two disks produced in the same manner as in Example 1 were assembled by closely bonding them with an adhesive, or two disks were assembled by an air sand inch method using a spacer. , then insert the disk 14
This is a case where baking was performed at 0° C. for 10 minutes.
このようにして作製したディスクの特性として、記録／
再生／消去を繰り返したときの搬送波対雑音比： Ｃ／
Ｎの変化を調べた。その結果を第５図に示す。比較例と
して、ベーキングを行なっていないディスクを示した。As a characteristic of the disc produced in this way, recording/
Carrier-to-noise ratio when repeating playback/erasure: C/
We investigated changes in N. The results are shown in FIG. As a comparative example, a disk that was not baked was shown.
この図から、１４０℃でベーキングを行なうことにより
、記録／再生／消去を繰り返してもＣ／Ｈの劣化が著し
く抑制されていることがわかる。ベーキングの効果は、
この他に接着剤の硬化時間を短縮でき、生産性向上に一
寄与することもわがった。From this figure, it can be seen that by performing baking at 140° C., deterioration of C/H is significantly suppressed even when recording/reproducing/erasing is repeated. The effect of baking is
In addition, it was found that the curing time of the adhesive could be shortened, contributing to improved productivity.
［実施例３コ
本実施例は、記録材料にＩｎ−８ｅ、Ｇｅ−Ｔ ｅ −
Ｓ ｂ或いはＡ ｎ −Ｓ ｒ等の相転移による反射率
変化を利用して記録を行う、いわゆる相変化材料を用い
た光ディスクにおける実施例である。[Example 3] In this example, In-8e, Ge-T e -
This is an embodiment of an optical disc using a so-called phase change material, in which recording is performed using a change in reflectance due to phase transition such as S b or A n -S r.
ディスクの構造は、記録材料に相変化材料を用いた以外
、実施例１と同様で、その模式図は第１図に示すとおり
である。The structure of the disk was the same as in Example 1 except that a phase change material was used as the recording material, and its schematic diagram is shown in FIG.
このようにして作製したディスクを１８０℃にて熱処理
を行なった。このディスクの特性を、記録／再生／消去
を繰り返した時の搬送波対雑音比の変化により示した。The disk thus produced was heat treated at 180°C. The characteristics of this disk were shown by the change in carrier wave-to-noise ratio when recording/reproducing/erasing was repeated.
その結果は第６図に示すとおりである。比較例として熱
処理を行なわないディスクを用いたにの図から、熱処理
を行なうことにより、記録／再生／消去を繰り返しても
Ｃ／Ｎの変化を著しく抑制できることがわかった。The results are shown in FIG. From the figure using a disk that was not heat-treated as a comparative example, it was found that by heat-treating, changes in C/N can be significantly suppressed even when recording/reproducing/erasing is repeated.
光デイスク作製後に熱処理を行う本発明の実施によれば
成膜時の不安定要素が解消（内部応力の緩和、構造緩和
、未反応もしくは不完全反応の解消等）することができ
、レーザー光による記録や消去を繰り返した時のディス
ク特性の変動やディスク作製初期の特性のバラツキを著
しく小さくすることができる。これによりディスクの記
録情報の保持寿命を長くすることができ、かつ、情報の
記録や再生の誤りの発生を減少させ、ひいてはディスク
の信頼性を向上させることができる。さらにディスクへ
記録或いは旧情報を消去する時の最小レーザーパワーを
低くすることもできる。By implementing the present invention in which heat treatment is performed after optical disk manufacturing, unstable factors during film formation can be eliminated (relaxation of internal stress, relaxation of structure, elimination of unreacted or incomplete reactions, etc.), and It is possible to significantly reduce variations in the characteristics of the disk upon repeated recording and erasing and variations in the characteristics at the initial stage of disk manufacture. This makes it possible to extend the retention life of recorded information on the disc, reduce the occurrence of errors in recording and reproducing information, and improve the reliability of the disc. Furthermore, the minimum laser power when recording on a disk or erasing old information can also be lowered.
第１図は光ディスクの模式的断面図、第２図、第４図、
第５図、第６図は本発明の実施例と従来例の光ディスク
における記録／再生／消去を繰り返した時のＣ／Ｎの変
化曲線図、第３図は２００℃でディスクを熱処理したと
きの垂直磁気異方性エネルギーの経時変化曲線図である
。
茅
図
茅
閃
ヤ東すＪＬ回歌（回）
誉
ム
図
９決り達、しＵ３で（（回）
蔓
図
欽１吟閏
（か）
第
図
枦東ソ運ユｊコ秋（巨υFig. 1 is a schematic cross-sectional view of an optical disc, Fig. 2, Fig. 4,
Figures 5 and 6 are C/N change curves when repeated recording/reproducing/erasing is performed on optical discs of the embodiment of the present invention and the conventional example, and Figure 3 is a diagram showing the change curves of C/N when the discs are heat-treated at 200°C. FIG. 3 is a diagram showing a time-dependent change curve of perpendicular magnetic anisotropy energy. Mozuzu Kaya Senya Higashi JL round song (time) Homazu 9 decision, Shi U3 ((time) Tsunezukin 1 Ginjyu (ka) fig.
Claims (1)
、再生または消去を行う光ディスクの製造において、記
録媒体を室温より高い温度に加熱することで熱処理した
ことを特徴とする光ディスクの製造方法。 ２、記録媒体として垂直磁気異方性を有する非晶質膜を
用いたことを特徴とする特許請求の範囲第１項記載の光
ディスクの製造方法。 ３、記録媒体として、非晶質と結晶質、或いは結晶質と
結晶質との間で相転移を起す材料を用いたことを特徴と
する特許請求の範囲第１項記載の光ディスクの製造方法
。 ４、記録媒体の熱処理の手法として、ディスク円板を密
着貼り合せ法やエアーサンド法等接着剤を用いた組立て
を行なう工程で、２板の円板を組立てた後にディスクを
加熱して接着剤を硬化させると同時に記録媒体の熱処理
を行なつたことを特徴とする特許請求の範囲第１項記載
の光ディスクの製造方法。 ５、垂直磁気異方性を有する材料として、希土類元素と
鉄族元素を主体とする材料を用いたことを特徴とする特
許請求の範囲第２項記載の光ディスクの製造方法。 ６、相転移を行う材料としてカルコゲナイドを主体とす
る材料やレーザー光照射で上げることができる温度範囲
に融点を有する合金を用いたことを特徴とする特許請求
の範囲第３項記載の光ディスクの製造方法。 ７、ディスク面に対して垂直方向に磁場を印加した状態
で熱処理を行ない、かつその温度がキュリー温度以下で
あることを特徴とする特許請求の範囲第２項記載の光デ
ィスクの製造方法。[Claims] 1. In the production of optical discs that use an amorphous recording medium and perform recording, reproduction, or erasing using laser light, the recording medium is heat-treated by heating it to a temperature higher than room temperature. Characteristic optical disc manufacturing method. 2. The method of manufacturing an optical disk according to claim 1, wherein an amorphous film having perpendicular magnetic anisotropy is used as the recording medium. 3. The method of manufacturing an optical disc according to claim 1, wherein a material that causes a phase transition between an amorphous state and a crystalline state or between a crystalline state and a crystalline state is used as the recording medium. 4. As a method of heat treatment of recording media, it is a process in which disks are assembled using an adhesive such as a close bonding method or an air sand method.After assembling two disks, the disk is heated and the adhesive is applied. 2. The method of manufacturing an optical disc according to claim 1, wherein the recording medium is heat-treated at the same time as curing the recording medium. 5. The method for manufacturing an optical disk according to claim 2, characterized in that the material having perpendicular magnetic anisotropy is a material mainly containing rare earth elements and iron group elements. 6. Manufacture of an optical disk according to claim 3, characterized in that a material mainly consisting of chalcogenide or an alloy having a melting point in a temperature range that can be raised by laser beam irradiation is used as the material that undergoes a phase transition. Method. 7. The method of manufacturing an optical disk according to claim 2, wherein the heat treatment is performed with a magnetic field applied in a direction perpendicular to the disk surface, and the temperature is below the Curie temperature.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63148112A JPH023131A (en) | 1988-06-17 | 1988-06-17 | Production of optical disk |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63148112A JPH023131A (en) | 1988-06-17 | 1988-06-17 | Production of optical disk |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH023131A true JPH023131A (en) | 1990-01-08 |
Family
ID=15445517
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63148112A Pending JPH023131A (en) | 1988-06-17 | 1988-06-17 | Production of optical disk |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH023131A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5627012A (en) * | 1995-02-13 | 1997-05-06 | Tdk Corporation | Method for preparing phase change optical recording medium |
| US5965323A (en) * | 1997-02-27 | 1999-10-12 | Tdk Corporation | Method for preparing optical recording medium |
| US6242157B1 (en) | 1996-08-09 | 2001-06-05 | Tdk Corporation | Optical recording medium and method for making |
| US6537721B2 (en) | 1999-02-15 | 2003-03-25 | Tdk Corporation | Optical recording medium and method for its initialization |
| US7157848B2 (en) | 2003-06-06 | 2007-01-02 | Electrovac Fabrikation Elektrotechnischer Spezialartikel Gmbh | Field emission backlight for liquid crystal television |
-
1988
- 1988-06-17 JP JP63148112A patent/JPH023131A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5627012A (en) * | 1995-02-13 | 1997-05-06 | Tdk Corporation | Method for preparing phase change optical recording medium |
| US6242157B1 (en) | 1996-08-09 | 2001-06-05 | Tdk Corporation | Optical recording medium and method for making |
| US5965323A (en) * | 1997-02-27 | 1999-10-12 | Tdk Corporation | Method for preparing optical recording medium |
| US6537721B2 (en) | 1999-02-15 | 2003-03-25 | Tdk Corporation | Optical recording medium and method for its initialization |
| US7157848B2 (en) | 2003-06-06 | 2007-01-02 | Electrovac Fabrikation Elektrotechnischer Spezialartikel Gmbh | Field emission backlight for liquid crystal television |
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