JP4097487B2 - Phase change recording medium - Google Patents

Description

【００６９】
＜評価＞上記参考例１〜５および比較例１で作製した評価用相変化型記録媒体について、波長４０２ｎｍ、開口数ＮＡ０．８５の光学系を用いて集束光ビームを照射し、線速：６ｍ／ｓ、０．１３０μｍ／ｂｉｔの条件で、初期ジッタ（Ｊｉｔｔｅｒ）、アーカイバル特性、Ｏ／Ｗ特性を評価した。結果を表２に示す。
【００７０】
【表２】

【００７１】
評価判断基準は下記による。
アーカイバル特性：８０℃、８５％（ＲＨ）の保存でジッタ（Ｊｉｔｔｅｒ）上昇が２０％に以上となる時間（Ｈ）。
Ｏ／Ｗ特性：オーバーライト（Ｏ／Ｗ）によるジッタ（Ｊｉｔｔｅｒ）上昇が２０％に到達したオーバーライト（Ｏ／Ｗ）回数（回）。
【００７２】
上記評価試験の結果、参考例１〜５の評価用相変化型記録媒体はいずれも優れたアーカイバル特性（１０００Ｈ〜２０００Ｈ）、Ｏ／Ｗ特性（１００００回〜２００００回）を示し、比較例のそれぞれの特性１００Ｈ（アーカイバル特性）、１０００回（Ｏ／Ｗ特性）に較べていずれも１０倍以上の性能を示した。
【００７３】
【発明の効果】
本発明の、基板上に少なくとも第１の記録構成層と樹脂中間層と第２の記録構成層とを設けた層構成とし、該第１の記録構成層は基板側から順に反射放熱層、第１保護層、第１記録層、第２保護層から構成し、該第２の記録構成層は樹脂中間層側から順に第３保護層、ＡｇまたはＡｇ合金層、第４保護層、第２記録層、第５保護層から構成し、前記第１記録層と第２記録層が少なくともＳｂＴｅを含有し、前記第３保護層の線膨張係数が３．０×１０^-6〜１０×１０^-6であり、かつ光の透過率が８０％以上とする構成により、ジッタなどのノイズが発生せず、優れたＯ／Ｗ特性、アーカイバル特性、高密度記録性能を発揮する相変化型記録媒体が提供される。
また、本発明の前記第３保護層の形成成分をＢｅ₂Ｏ₃、あるいはＡｌ₂Ｏ₃とＳｉＯ₂との混合系組成、あるいはＭｇＯとＳｉＯ₂との混合系組成、あるいはＩｎ₂Ｏ₃とＺｎＯとの混合系組成、あるいはＩｎ₂Ｏ₃とＳｎＯ₂との混合系（ＩＴＯ）組成、あるいはＩｎ₂Ｏ₃とＺｎＯとＳｎＯ₂との混合系組成とすることによってＯ／Ｗ時の熱的体積変化に対応できるようにし、これによってアーカイバル特性が良好で、かつＯ／Ｗ特性が改善された高密度記録の可能な相変化型記録媒体が提供される。
【図面の簡単な説明】
【図１】本発明の相変化型記録媒体を説明するための一例を示す層構成断面図である。
【図２】本発明の実施の形態における第３保護層７の線膨張係数と第２記録層１０のＯ／Ｗ回数との関係を示す図である。
【図３】本発明の実施例における評価用相変化型記録媒体の層構成を示す断面図である。
【符号の説明】
１ 基板
２ 反射放熱層
３ 第１保護層
４ 第１記録層
５ 第２保護層
６ 樹脂中間層
７ 第３保護層
８ ＡｇまたはＡｇ合金層
９ 第４保護層
１０ 第２記録層
１１ 第５保護層
１２ 接着層
１３ カバー基板
２１ 基板（ポリカーボネート）
２２ 反射放熱層（ＡｇＣｕＰｔＰｄ）
２３ 第１保護層（ＺｎＳＳｉＯ₂）
２４ 第１記録層（Ａｇ₅Ｉｎ₅Ｓｂ₆₅Ｔｅ₂₅）
２５ 第２保護層（ＺｎＳＳｉＯ₂）
２６ 樹脂中間層（ポリカーボネート）
２７ 第３保護層（Ｂｅ₂Ｏ₃）
２８ ＡｇまたはＡｇ合金層（ＡｇＣｕＰｔＰｄ）
２９ 第４保護層（ＺｎＳＳｉＯ₂）
３０ 第２記録層（Ｇｅ₅Ａｇ₂Ｓｂ₇₀Ｔｅ₂₃）
３１ 第５保護層（ＺｎＳＳｉＯ₂）
３２ 接着層（アクリル系両面接着）
３３ カバー基板（ポリカーボネート）
１００ 第１の記録構成層
２００ 第２の記録構成層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording medium (phase change recording medium) for high density recording having a phase change recording layer such as a rewritable DVR.
[0002]
[Prior art]
In general, a compact disc (CD) or DVD is performed by recording a binary signal and detecting a tracking signal using a change in reflectance caused by interference of reflected light from the bottom and mirror surface of a concave pit. In recent years, phase-change-type rewritable compact discs (CD-RW: CD-Rewritable) are being widely used as media that have playback compatibility (compatibility) with CDs. Various possible DVDs have been proposed. Also, a system DVR has been proposed in which the recording / reproducing wavelength is shortened to 390 nm to 420 nm and the numerical aperture NA (Numerical Aperture) is increased to a capacity of 20 GB or more, whereas the capacity of the DVD is 4.7 GB. (For example, ISO Technical Digest, '00 (2000), 210).
[0003]
These phase-changeable rewritable CDs, DVDs, and DVRs detect a recording information signal by using a reflectance difference and a phase difference change caused by a difference in refractive index between an amorphous state and a crystalline state. A typical phase change medium has a structure in which a lower protective layer, a phase change recording layer, an upper protective layer, and a reflective layer are provided on a substrate, and reflectivity difference and phase difference using multiple interference of these constituent layers. Can be made compatible with CDs and DVDs. In the CD-RW, the compatibility of the CD with the recording signal and the groove signal can be ensured within the range where the reflectance is reduced to about 15 to 25%, and the CD drive with an amplification system that covers the low reflectance is added. Playback is possible. Since the phase change type recording medium can perform the erasing and re-recording processes only by intensity modulation of one focused light beam, recording in a phase change type recording medium such as a CD-RW or a rewritable DVD is recording. And overwrite (O / W) recording that simultaneously performs erasure.
[0004]
For recording information using phase change, crystalline, amorphous or mixed state can be used, and multiple crystalline phases can be used, but rewritable phase change type currently in practical use In general, recording media are recorded in an amorphous state by forming an unrecorded / erased state in a crystalline state.
[0005]
As the material for the phase change recording layer, chalcogen elements, that is, chalcogenide alloys containing S, Se, and Te are often used. For example, a GeSbTe system mainly composed of a GeTe-Sb ₂ Te ₃ pseudo binary alloy, an InSbTe system mainly composed of an InTe-Sb ₂ Te ₃ pseudo binary alloy, and an Sb _0.7 Te _0.3 eutectic alloy as a main component. AgInSbTe system, GeSbTe system and the like. Among these, GeTe-Sb ₂ Te ₃ pseudo-binary alloys added with excess Sb, especially Ge ₁ Sb ₂ Te ₄ or Ge ₂ Sb ₂ Te _{5 and} other near-intermetallic compound compositions have been mainly put into practical use. ing. These compositions are characterized by crystallization without phase separation peculiar to an intermetallic compound. Since the crystal growth rate is high, initialization is easy and recrystallization rate at the time of erasure is high. For this reason, conventionally, as a recording layer exhibiting a practical overwrite (O / W) characteristic, a pseudo binary alloy system or a composition near an intermetallic compound has been attracting attention (references Jpn. J. Appl. Phys., vol.69 (1991), p2849, or SPIE, vol.2514 (1995), pp294-301, etc.).
[0006]
Further, a GeSbTe ternary composition or a recording layer composition containing an additive element based on this ternary composition has been reported (Japanese Patent Laid-Open Nos. 61-258787, 62-53886, 62). -152786, JP-A-1-63195, 1-211249, 1-2277338). However, in order to apply a material having such a composition to an optical recording medium for high-density recording such as rewritable DVR, development has just started and there are many problems to be solved.
In particular, in the case of a short wavelength optical system such as a blue laser, the beam output is low, so that there is a drawback that noise tends to occur in the recording layer, and it is difficult to satisfy the overwrite (O / W) characteristics, and high speed and high density. It is an issue in recording.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and its purpose is to suppress noise such as jitter, excellent O / W characteristics, and archival characteristics even for low output light with a short wavelength such as a blue laser. Another object of the present invention is to provide a phase change type recording medium capable of recording at a high density.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a phase change recording medium according to the present invention comprises a layer structure in which at least a first recording structure layer, a resin intermediate layer, and a second recording structure layer are provided on a substrate, The first recording constituent layer is composed of a reflective heat dissipation layer, a first protective layer, a first recording layer, and a second protective layer in order from the substrate side, and the second recording constituent layer is third protective in order from the resin intermediate layer side. Layer, an Ag or Ag alloy layer, a fourth protective layer, a second recording layer, and a fifth protective layer, wherein the first recording layer and the second recording layer contain at least SbTe, and the third protective layer Is a mixed composition of In ₂ O ₃ and SnO ₂ , the linear expansion coefficient of the third protective layer is 3.0 × 10 ⁻⁶ to 10 × 10 ⁻⁶ , and light transmittance By setting the ratio to 80% or more, noise such as jitter is suppressed, O / W characteristics, archival characteristics, high density It is obtained by improving the recording performance.
[0009]
That is, the recording medium of claim 1 is a phase change type recording medium using a phase transition phenomenon between crystal and amorphous by light irradiation, and the constituent layers are sequentially formed. For example, a reflective heat radiation layer made of an Ag alloy is provided on a substrate on which a guide groove is formed, and the first protective layer and the second protective layer have, for example, a mixed composition of ZnS and SiO ₂ , and SbTe is a main constituent element. The first recording layer for recording on the first recording layer is provided from the so-called reflective heat dissipation layer to the second protective layer in which the first recording layer contained as a layer is laminated. The linear expansion coefficient is 3.0 × 10 ⁻⁶ to 10 × 10 ⁻⁶ , and light is transmitted through an intermediate layer in which grooves are formed of a transparent resin such as UV resin on the second protective layer. A third protective layer having a transmittance of 80% or more and an Ag or Ag alloy layer adjacent thereto are provided, and the fourth protective layer and the fifth protective layer have, for example, a mixed composition of ZnS and SiO ₂ , and SbTe is formed. The second recording layer containing the main recording element is laminated, so that the so-called third protective layer to fifth protective layer are provided as a second recording constituent layer for recording on the second recording layer. .
[0010]
As described above, the recording layer is composed of two layers, and each recording layer contains at least SbTe, thereby facilitating the formation of a small mark to cope with high-density recording, and a linear expansion coefficient between the two recording layers. A third protective layer having a light transmittance of 80% or more and an Ag or Ag alloy layer adjacent to the protective layer and having a thickness of 20 nm or less is 3.0 × 10 ⁻⁶ to 10 × 10 ⁻⁶ or less. This improves heat dissipation and absorbs deformation caused by heat. That is, by using Ag or an Ag alloy having a high light transmittance and thermal conductivity in the vicinity of a recording wavelength of 405 nm, heat dissipation is further improved, O / W characteristics are improved, and high-density recording is possible. Is.
[0011]
The mixing system the composition of the formation component of the third protective layer in a phase change type recording medium of the present invention Be ₂ O _3, or mixtures based composition of Al ₂ O ₃ and SiO _2, or MgO and SiO _2, or in ₂ mixed system composition of O ₃ and ZnO, Oh Rui by a mixed system composition of in ₂ O ₃ and ZnO and SnO _2, and to accommodate thermal volume change during O / W, As a result, O / W characteristics are improved, high-density recording is realized, and archival characteristics are improved.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 schematically shows a cross-sectional view of a layer structure showing an example of a phase change type recording medium of the present invention. Substrate 1 / reflective heat dissipation layer 2 / first protective layer 3 / first recording layer 4 / Second protective layer 5 / resin intermediate layer 6 / third protective layer 7 / Ag or Ag alloy layer 8 / fourth protective layer 9 / second recording layer 10 / fifth protective layer 11 / adhesive layer 12 / cover substrate 13 It has a configuration. The order of the layers as shown in FIG. 1 is suitable when each recording layer is irradiated with a focused light beam for recording / reproducing, for example, laser light, through the transparent cover substrate 13.
[0013]
As a material of the substrate 1 in the phase change recording medium of the present invention, a transparent resin such as polycarbonate, acrylic resin, polyolefin, or transparent glass can be used. Of these, polycarbonate resin is the most preferred material because it has a track record of being most widely used in CD and is inexpensive. The substrate 1 is usually provided with grooves having a pitch of 0.8 μm or less for guiding the recording / reproducing light. However, the grooves are not necessarily geometrically rectangular or trapezoidal grooves, and are refracted by, for example, ion implantation. Optical waveguides may be formed by forming waveguides having different rates.
[0014]
Next, the material of the first recording layer 4 and the second recording layer 10 in the phase change recording medium of the present invention is a thin film mainly composed of an alloy containing Sb and Te as main constituent elements, Examples of such an alloy include those containing Ge, Sb, and Te as constituent elements. If necessary, other elements may be added to each recording layer made of such constituent elements up to a total of about 10 atomic%. Further, the optical constant of the recording layer can be finely adjusted by adding at least one element selected from O, N or S to each recording layer in an amount of 0.1 atomic% to 5 atomic%. However, it is not preferable to add more than 5 atomic% because the crystallization speed is lowered and the erasing performance is deteriorated.
[0015]
In addition, at least one selected from V, Nb, Ta, Cr, Co, Pt or Zr is added in an amount of 8 atomic% or less in order to increase the temporal stability without reducing the crystallization rate during overwrite (O / W). More preferably, it is 0.1 atomic% or more and 5 atomic% or less. The total amount of the additive element and Ge added to SbTe is preferably 15 atomic% or less. If it is contained in excess of 15 atomic%, phase separation other than Sb is induced. In particular, when the Ge content is 3 atomic% or more and 5 atomic% or less, the effect of addition is large.
[0016]
In order to improve stability over time and finely adjust the refractive index, it is preferable to add at least one of Si, Sn, or Pb in an amount of 5 atomic% or less. The total addition amount of these additive elements and Ge is preferably 15 atomic% or less. Each element of Si, Sn, or Pb is an element having a tetracoordinate network like Ge.
[0017]
Further, by adding 8 atomic% or less of Al, Ga, and In, there is an effect of increasing the crystallization temperature and simultaneously reducing jitter and improving the recording sensitivity, but segregation is likely to occur, so 6 atomic%. The following is preferable. Each addition amount of Al, Ga, In is 15 atomic% or less, preferably 13% or less as a total addition amount combined with Ge. Adding Ag in an amount of 8 atomic% or less is effective in improving the recording sensitivity, and the effect is particularly remarkable when it is used when the Ge atomic weight exceeds 5 atomic%. However, if the addition amount of Ag exceeds 8 atomic%, it is not preferable because it increases jitter and impairs the stability of the amorphous mark. Moreover, since it is easy to produce segregation when the total addition amount combined with Ge exceeds 15 atomic%, it is not preferable. The most preferable Ag content is 5 atomic% or less.
[0018]
The first recording layer 4 and the second recording layer 10 of the phase change recording medium of the present invention are phase change recording layers, and the thickness is generally preferably in the range of 5 nm to 100 nm. If the thickness of the first recording layer 4 and the second recording layer 10 is less than 5 nm, it is difficult to obtain sufficient contrast, and the crystallization speed tends to be slow, so that erasure in a short time is likely to be difficult. On the other hand, if it exceeds 100 nm, it is difficult to obtain optical contrast, and cracks are likely to occur. The contrast needs to be compatible with a read-only disc such as a DVD.
[0019]
In high-density recording where the shortest mark length is 0.5 μm or less, the recording layer is preferably 5 nm or more and 25 nm or less. If the thickness is less than 5 nm, the reflectance is too low, and the influence of a non-uniform composition and a sparse film at the initial stage of film growth tends to appear. On the other hand, if it is thicker than 25 nm, the heat capacity becomes large and the recording sensitivity is deteriorated, and the crystal growth becomes three-dimensional, so that the edge of the amorphous mark tends to be disturbed and the jitter tends to increase. Furthermore, the volume change due to the phase change of the first recording layer 4 and the second recording layer 10 becomes remarkable, and the repeated overwrite (O / W) durability deteriorates, which is not preferable. From the viewpoint of jitter at the mark end and repeated overwriting (O / W) durability, the thickness is more preferably 20 nm or less.
[0020]
The density of each of the first recording layer 4 and the second recording layer 10 is desirably 80% or more, more preferably 90% or more of the bulk density.
In the sputtering film forming method, the density of the first recording layer 4 and the second recording layer 10 is such that the pressure of the sputtering gas (rare gas such as Ar) during film formation is lowered or the substrate is placed close to the front of the target. It is necessary to increase the amount of high energy Ar irradiated to the recording layer by arranging it. The high energy Ar is one in which Ar ions irradiated to the target for sputtering are partially rebounded and reach the substrate side, or Ar ions in the plasma are accelerated by the sheath voltage over the entire surface of the substrate and reach the substrate. Either. Such an irradiation effect of a high energy rare gas is referred to as an “atomic peening effect”. In sputtering with Ar gas that is generally used, Ar is mixed into the sputtered film by an atomic peening effect. The atomic peening effect can be estimated from the amount of Ar in the mixed film. That is, if the amount of Ar is small, it means that the effect of irradiation with high energy Ar is small, and a film with a low density is easily formed. On the other hand, if the amount of Ar is large, irradiation with high energy Ar is intense and the density becomes high, but Ar taken into the film precipitates as void during repeated overwriting (O / W), and deteriorates repeated durability. Let An appropriate amount of Ar in the recording layer film is 0.1 atomic% or more and 1.5 atomic% or less. Furthermore, it is preferable to use high frequency sputtering rather than direct current sputtering because a high density film can be obtained by reducing the amount of Ar in the film.
[0021]
In addition, the first recording layer 4 and the second recording layer 10 of the phase change recording medium of the present invention are usually amorphous after film formation. Therefore, it is necessary to crystallize the entire surface of each recording layer after film formation so as to be in an initialized state (unrecorded state). As an initialization method, initialization by annealing in a solid phase is possible, but initialization by so-called melt recrystallization in which the recording layer is once melted and gradually cooled during resolidification to be crystallized is desirable. Each of the recording layers described above has few crystal growth nuclei immediately after film formation, and crystallization in the solid phase is difficult. However, according to melt recrystallization, a few crystal nuclei are formed and then melted. Recrystallization progresses at high speed mainly by crystal growth.
The crystals produced by the melt recrystallization in the first recording layer 4 and the second recording layer 10 and the crystals produced by annealing in the solid phase have different reflectivities. In actual overwrite (O / W) recording, since the erased portion becomes a crystal by melt recrystallization, initialization is preferably performed by melt recrystallization.
[0022]
In initialization by melt recrystallization, the recording layer is preferably melted locally and in a short time of about 1 millisecond or less. This is because if the melting region is wide, or if the melting time or the cooling time is too long, each layer is destroyed by heat or the surface of the plastic substrate is deformed. In order to provide a thermal history suitable for initialization, a high-power semiconductor laser beam having a wavelength of about 600 to 1000 nm is focused and irradiated on a long axis of 100 to 300 μm and a short axis of 1 to 3 μm. It is desirable to scan at a linear velocity of 10 m / s. Even if the same focused light is close to a circle, the melted region is too wide, re-amorphization is likely to occur, and damage to the multilayer structure and the substrate is not preferable.
[0023]
It can be confirmed as follows that the initialization was performed by melt recrystallization. That is, the recording medium having the recording power Pw, which melts the recording layer focused to a spot diameter smaller than about 1.5 μm, is applied to the medium after initialization at a constant linear velocity in a direct current. If there is a guide groove, the tracking servo and the focus servo are applied to the groove or the track formed between the grooves.
After that, if the reflectance in the erased state obtained by irradiating erasing light with the erasing power Pe (≦ Pw) on the same track is almost the same as the reflectance in the unrecorded initial state, the initialization is performed. The state can be confirmed as a melt recrystallization state. This is because the recording layer is once melted by irradiation with the recording light and completely recrystallized by irradiation with the erasing light, and then undergoes a process of melting by the recording light and recrystallization by the erasing light. This is because it is in a state of being converted into a state. Note that the reflectivity Rini in the initialized state and the reflectivity in the melt recrystallized state Rcry are substantially the same as the difference in reflectivity defined by (Rini−Rcry) / {(Rini + Rcry) / 2}. Is 20% or less. Usually, the reflectance difference is larger than 20% only by solid phase crystallization such as annealing.
[0024]
As shown in FIG. 1, each of the first recording layer 4 and the second recording layer 10 of the present invention has a first recording layer 4 between the first protective layer 3 and the second protective layer 5, respectively. The second recording layer 10 is sandwiched between the fourth protective layer 9 and the fifth protective layer 11 and is provided on the surface of the substrate 1 (groove forming surface).
[0025]
Each protective layer of the first protective layer 3, the second protective layer 5, the fourth protective layer 9, and the fifth protective layer 11 of the present invention will be described below.
The first protective layer 3 of the first recording configuration layer 100 prevents mutual diffusion between the first recording layer 4 and the reflective heat radiation layer 2, and suppresses deformation of the first recording layer 4, while efficiently reducing the reflection heat radiation layer 2. It also has the function of releasing heat. The second protective layer 5 is effective mainly for preventing deformation of the surface of the resin intermediate layer 6 due to a high temperature during recording. The fourth protective layer 9 of the second recording configuration layer 200 has a function of releasing heat to the second recording layer 10, the Ag or Ag alloy layer 8, and the third protective layer 7, and the second recording layer 10 and the Ag or Ag alloy. It also has a function of preventing mutual diffusion of the layer 8. The fifth protective layer 11 is effective in adjusting the reflectance and preventing the deformation of the adhesive layer 12 and the cover substrate 13 due to the high temperature during recording.
[0026]
As materials for the first protective layer 3, the second protective layer 5, the fourth protective layer 9, and the fifth protective layer 11, attention should be paid to the refractive index, thermal conductivity, chemical stability, mechanical strength or adhesion. Determined. As a material for forming each of the protective layers, it is desirable that the heat conduction characteristic is low, but the standard is 1 × 10 ⁻³ pJ / (μm · K · nsec). Note that it is difficult to directly measure the thermal conductivity of such a low thermal conductivity material in a thin film state, and a guideline can be obtained from the measurement results of thermal simulation and actual recording sensitivity as an alternative to direct measurement. .
[0027]
As each of the above-mentioned protective layer materials having a low thermal conductivity that brings about a preferable result, it contains at least one of ZnS, ZnO, TaS ₂ or rare earth sulfides in an amount of 50 mol% or more and 90 mol% or less, has high transparency, and has a melting point or A composite dielectric containing a heat-resistant compound having a decomposition point of 1000 ° C. or higher is desirable. More specifically, a composite dielectric containing 60 mol% or more and 90 mol% or less of a rare earth sulfide such as La, Ce, Nd, or Y is desirable. Alternatively, the composition range of ZnS, ZnO or rare earth sulfide is desirably 70 to 90 mol%.
Examples of heat-resistant compound materials having a melting point or decomposition point of 1000 ° C. or higher to be mixed with these include Mg, Ca, Sr, Y, La, Ce, Ho, Er, Yb, Ti, Zr, Hf, V, Nb, Oxides such as Ta, Zn, Al, Si, Ge, and Pb, nitrides, carbides, and fluorides such as Ca, Mg, and Li can be used.
Note that the oxides, sulfides, nitrides, carbides, and fluorides do not necessarily have a stoichiometric composition, and it is also effective to control the composition or use a mixture for controlling the refractive index and the like. It is.
[0028]
As the protective layers of the first protective layer 3, the second protective layer 5, the fourth protective layer 9, and the fifth protective layer 11 of the present invention, the above noted points and the first recording layer 4 and the second recording layer of the present invention are used. In consideration of the consistency with the material constituting 10, a mixed system composition of ZnS and SiO ₂ is most preferable.
In the present invention, each protective layer is made of a mixture of ZnS and SiO ₂ as described above. However, using the same material in this way is advantageous from the viewpoint of reducing manufacturing costs.
[0029]
The function and the like of each protective layer will be further described in detail.
The layer structure of the present invention belongs to a kind of layer structure called a rapid cooling structure. The rapid cooling structure employs a layer structure that promotes heat dissipation and increases the cooling rate at the time of re-solidification of the recording layer, thereby avoiding the problem of recrystallization during the formation of amorphous marks and increasing the speed by high-speed crystallization. Realize erasure ratio.
[0030]
The film thicknesses of the first protective layer 3 and the fourth protective layer 9 of the present invention greatly affect the durability in repeated overwriting (O / W), and are particularly important for suppressing deterioration of jitter. The film thickness is generally 5 nm or more and 30 nm or less. If the thickness is less than 5 nm, the effect of delaying heat conduction in the protective layer is insufficient, and the recording sensitivity is significantly lowered. If the film thickness is greater than 30 nm, a sufficient flattening effect of the temperature distribution in the mark width direction cannot be obtained, and the temperature on the recording side and the heat dissipation layer side of the second protective layer 5 and the fifth protective layer 11 respectively during recording. The difference becomes large, and the protective layer itself is easily deformed asymmetrically due to the difference in thermal expansion between both sides of the protective layer. This repetition is not preferable because it accumulates microscopic plastic deformation inside the protective layer and causes an increase in noise.
The detailed thicknesses of the first protective layer 3 and the fourth protective layer 9 are preferably 15 nm to 25 nm when the wavelength of the recording laser light is 600 to 700 nm, preferably 5 to 20 nm when the wavelength is 350 to 600 nm, and more preferably. 5-15 nm.
[0031]
The film thickness of the second protective layer 5 and the fifth protective layer 11 needs to be 5 nm or more and 30 nm or less. If the thickness is less than 5 nm, the recording layer is likely to be destroyed due to deformation or the like at the time of melting the recording layer, and the heat dissipation effect is so great that the power required for recording becomes unnecessarily large.
[0032]
When the phase change type recording layer material as described above is used, low jitter can be realized in high-density recording with a shortest mark length of 0.3 μm or less. However, according to the study by the present inventors, in order to realize high-density recording. When a short-wavelength laser diode (for example, a wavelength of 420 nm or less) is used, further attention needs to be paid to the layer structure of the rapid cooling structure. In particular, in the study of one-beam overwrite characteristics using a small focused light beam having a wavelength of 500 nm or less and a numerical aperture NA of 0.55 or more, it is possible to flatten the temperature distribution in the mark width direction to achieve a high erase ratio and erase power. It turned out to be important for wide margins. The same tendency applies to the DVR-compatible optical system using an optical system with a wavelength of 390 to 420 nm and NA = 0.85.
[0033]
The present inventors have examined an appropriate layer structure of a phase change type recording medium having a two-layer recording structure so as to meet the above requirements, have light transmission properties and heat dissipation properties, and are capable of thermal deformation due to O / W. The third protective layer 7 was constructed so that it could withstand, and a design was made to improve recording / reproduction characteristics, particularly O / W characteristics.
[0034]
In high-density mark length modulation recording using the optical system as described above, a layer having particularly low thermal conductivity is used as the second protective layer 5, and preferably the film thickness is 7 nm or more and 25 nm or less. is important. For this reason, the third protective layer 7 provided on the second protective layer 5 needs to have a high thermal conductivity. With this configuration, heat does not escape rapidly during high-speed recording, and a thermal gradient is created. High-speed recording becomes possible. The third protective layer 7 has a function of releasing heat and preventing deformation of the surface of the resin intermediate layer 6.
[0035]
In the above, when considering only thermal conductivity, the heat radiation effect is promoted even if the thermal conductivity coefficient of the first protective layer 3 or the fourth protective layer 9 is increased, but recording is performed when the heat radiation is promoted too much. The problem is that the irradiation power required for the recording becomes high and the recording sensitivity is remarkably lowered. Therefore, it is necessary to have a low thermal conductivity.
By using a thin-film protective layer with low thermal conductivity, a time delay is given to heat conduction from the recording layer to the heat dissipation layer for several nsec to several tens of nsec at the start of recording power irradiation, and then heat dissipation to the heat dissipation layer is promoted. Therefore, the recording sensitivity is not lowered more than necessary due to the heat conduction characteristics of the protective layer. For these reasons, the conventionally known protective layer material mainly composed of SiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , AlN, SiN or the like has its own thermal conductivity that is too high. It is not preferable to use in
[0036]
In the present invention, a protective layer having a linear expansion coefficient of 3.0 × 10 ⁻⁶ to 10 × 10 ⁻⁶ is formed as the third protective layer 7, and, as will be described later, The O / W characteristic of the second recording layer 10 was improved by forming an Ag or Ag alloy layer (20 nm or less) adjacent to the protective layer. In this case, if the light transmittance of the third protective layer 7 is 80% or more, even if the transmittance of the second recording structure layer 200 is 40%, the reflectance from the first recording structure layer 100 is Since the value is higher than the reflectivity of the substrate, recording can be performed on both the first recording layer 4 and the second recording layer 10.
[0037]
As an example, a phase change recording medium comprising the third protective layer 7 (mixed composition (ITO) of In ₂ O ₃ and SnO ₂ ) having a different linear expansion coefficient and an Ag layer having a thickness of 10 nm is provided. The O / W characteristics of the second recording layer 10 are shown in FIG. The linear expansion coefficient of the third protective layer 7 is 3.0 × 10 ⁻⁶ to 10 × 10 ⁻⁶ , indicating good O / W characteristics of the second recording layer 10. From this, the linear expansion coefficient of the third protective layer 7 is controlled, and if the thickness of the Ag or Ag alloy layer 8 is 20 nm or less, the transmittance of the Ag or Ag alloy layer is 80% or more. The transmittance of the recording structure layer 200 is 40% or more, and recording / reproduction of the first recording structure layer 100 is sufficiently possible.
[0038]
When Be ₂ O ₃ is used as the third protective layer 7 and the protective layer is formed under the conditions satisfying at least the above characteristics, Be ₂ O ₃ has a high thermal conductivity. The heat generated in the third protective layer 7 is dissipated through the Ag and Ag alloy layer. As a result, the recording layer mainly composed of the phase change material SbTe that requires rapid cooling is in an optimum rapid cooling state, and a small amorphous mark can be formed.
[0039]
Further, as the third protective layer 7, a mixed system composition of Al ₂ O ₃ and SiO ₂ , a mixed system composition of MgO and SiO ₂ , a mixed system composition of In ₂ O ₃ and ZnO, In ₂ O ₃ and SnO. _When the protective layer is formed using a mixed system composition of ₂ (ITO) or a mixed system composition of In ₂ O ₃ , ZnO and SnO ₂ , the storage stability (archival characteristics) is improved. In particular, if a small amount of chlorine or the like is contained in the material of the resin intermediate layer, not only the Ag or Ag alloy layer but also the recording layer is eroded, so that it is necessary to select a material with good storage stability. In the present invention, as a result of selecting the third protective layer 7 while paying attention to archival preservation, the above materials showed good characteristics.
[0040]
However, as the heat dissipation of the second recording configuration layer 200, the heat dissipation of the third protective layer 7 is not sufficient as described above, and the Ag and Ag alloy layer 8 improves the heat dissipation of heat, and in particular, SbTe. In the recording layer based on, the first rapid cooling of heat forms an amorphous mark. Therefore, by combining the Ag and Ag alloy layer 8 and the third protective layer 7, high density and O / W characteristics and storage stability are improved.
Below, the reflective heat radiation layer 2 and Ag or Ag alloy layer 8 which bear a heat radiation function are each demonstrated.
[0041]
The reflective heat radiation layer 2 can improve the erase ratio and erase power margin by using a material having a particularly high thermal conductivity. As a result of investigation, in order to exhibit the good erasing characteristics of the recording layer of the present invention in a wide erasing power range, not only the temperature distribution in the film thickness direction and the time change but also the film surface direction (with respect to the recording beam scanning direction). It is preferable to use a layer structure that can flatten the temperature distribution in the vertical direction as much as possible. In the present invention, the thin heat dissipation layer 2 having a very high thermal conductivity and 300 nm or less is used to promote the heat dissipation effect in the lateral direction.
In general, the thermal conductivity of a thin film is greatly different from that of a bulk state and is usually small. In particular, a thin film having a thickness of less than 40 nm is not preferable because the thermal conductivity may be reduced by an order of magnitude or more due to the influence of an island-like structure at the initial stage of growth. Furthermore, the crystallinity and the amount of impurities differ depending on the film forming conditions, which causes the thermal conductivity to be different even with the same composition.
[0042]
Heat dissipation in the reflective heat dissipation layer 2 of the first recording component layer 100 can be achieved even if the thickness of the reflective heat dissipation layer 2 is increased. However, if the thickness of the reflective heat dissipation layer 2 exceeds 300 nm, the film surface direction of the first recording layer 4 Therefore, the heat conduction in the film thickness direction becomes more remarkable, and the effect of improving the temperature distribution in the film surface direction cannot be obtained. Further, the heat capacity of the reflective heat radiation layer 2 itself is increased, and it takes time to cool not only the reflective heat radiation layer 2 but also the first recording layer 4, thereby inhibiting the formation of amorphous marks. Most preferably, the reflective heat-dissipating layer 2 having high thermal conductivity is thinly provided to selectively promote heat dissipation in the lateral direction. The quenching structure conventionally used pays attention only to the one-dimensional heat escape in the film thickness direction, and is intended only to release heat from the first recording layer 4 to the reflective heat dissipation layer 2 quickly. Not enough attention was paid to the flattening of the temperature distribution in the direction.
[0043]
Examples of the material of the reflective heat radiation layer 2 suitable for the present invention include Ag or an Ag alloy, a Cu alloy, and an Al alloy.
Examples of the Ag alloy include the same Ag alloy when used for Ag or an Ag alloy layer 8 described later. When an Ag alloy is used as the reflective heat radiation layer 2, the preferable film thickness is 30 nm or more and 200 nm or less. If it is less than 30 nm, the heat dissipation effect is insufficient even with pure Ag. If it exceeds 200 nm, the heat escapes in the vertical direction from the horizontal direction and does not contribute to the improvement of the heat distribution in the horizontal direction, and an unnecessary thick film decreases the productivity. Also, the microscopic flatness of the film surface is deteriorated.
[0044]
Examples of the Cu alloy include an Al—Cu alloy containing Cu in an amount of 0.3 wt% or more and 5.0 wt% or less. In particular, in the case of a two-layer protective layer in which a mixed composition of ZnS and SiO ₂ and Ta ₂ O ₅ are combined, Al—containing Cu in an amount of 0.5 wt% or more and 4.0 wt% or less. A Cu-based alloy is desirable as a reflective heat dissipation layer that satisfies all of the corrosion resistance, adhesion, and high thermal conductivity in a well-balanced manner. Further, an Al—Mg—Si based alloy containing 0.3% by weight or more and 0.8% by weight or less of Si and 0.3% by weight or more and 1.2% by weight or less of Mg is also effective.
[0045]
As the Al alloy, for example, an alloy containing Ta, Ti, Co, Cr, Si, Sc, Hf, Pd, Pt, Mg, Zr, Mo, or Mn in an amount of 0.2 atomic% to 2 atomic% in Al, etc. These have a volume resistivity that increases in proportion to the concentration of the additive element, have improved hillock resistance, and can be used in consideration of durability, volume resistivity, film formation rate, and the like. Regarding the Al alloy, if the amount of added impurities is less than 0.2 atomic%, the hillock resistance is often insufficient, although it depends on the film forming conditions. On the other hand, when the content is more than 2 atomic%, it is difficult to obtain the low resistivity. When importance is attached to stability over time, Ta is preferred as an additive component.
[0046]
When the Al alloy is used as the reflective heat dissipation layer 2, the preferable film thickness is 150 nm or more and 300 nm or less. If the thickness is less than 150 nm, the heat dissipation effect is insufficient even with pure Al. As described above, when the thickness exceeds 300 nm, the heat escapes in the vertical direction from the horizontal direction and does not contribute to the improvement of the horizontal heat distribution, and the heat capacity of the reflective heat radiating layer itself is large, so that the cooling rate of the recording layer becomes slow. Also, the microscopic flatness of the film surface is deteriorated.
[0047]
Next, the Ag or Ag alloy layer 8 will be described.
In the second recording layer 10 of the present invention, the crystal growth at the time of resolidification in the vicinity of Tm is the rate-limiting factor for recrystallization. In order to increase the cooling rate in the vicinity of Tm as much as possible to ensure the formation of amorphous marks and their edges, the ultra-rapid cooling structure is effective, and the temperature distribution in the film surface direction is flattened. Thus, what can be erased at high speed in the vicinity of Tm can reliably ensure erasure by recrystallization up to a higher erasing power. For this reason, when a so-called “super quenching structure in consideration of the heat conduction delay effect in the third protective layer 7” is applied to the second recording composition layer 200 according to the present invention, the conventional GeTe—Sb ₂ Te ₃ recording layer is applied. It is more effective than that.
[0048]
Ag or an Ag alloy layer 8 is used as a heat dissipation component layer for such ultra-cooling. In the case of forming the Ag or Ag alloy layer 8, it is made slower than the deposited reflective heat radiation layer 2 at the time of film formation to eliminate the film thickness non-uniformity. The film thickness of the Ag or Ag alloy layer 8 is preferably 5 nm or more and 20 nm or less. 5 nm or less becomes non-uniform even when the deposition rate is slowed down.
As an Ag alloy, Cu, Ti, V, Ta, Nb, W, Co, Cr, Si, Ge, Sn, Sc, Hf, Pd, Rh, Au, Pt, Mg, Zr, Mo, or Mn are 0 in Ag. An alloy containing 2 atomic% or more and 5 atomic% or less is also desirable. When importance is attached to stability over time, Ti and Mg are preferred as the additive component.
[0049]
The present inventors confirmed that the volume resistivity of the additive element to Al or the additive element to Ag in the reflective heat radiation layer 2 and the Ag or Ag alloy layer 8 increases in proportion to the concentration of the additive element. ing. On the other hand, the addition of impurities is generally considered to reduce the crystal grain size, increase the electron scattering at the grain boundaries, and lower the thermal conductivity. It is necessary to adjust the amount of added impurities in order to obtain the original high thermal conductivity of the material by increasing the crystal grain size.
[0050]
The reflective heat dissipation layer 2 and the Ag or Ag alloy layer 8 are usually formed by sputtering or vacuum deposition. Including the total amount of impurities needs to be 2 atomic% or less. Therefore, it is desirable that the ultimate vacuum of the process chamber is 1 × 10 ⁻³ Pa or less. In the case where the film is formed at an ultimate vacuum worse than 10 ⁻⁴ Pa, it is desirable to prevent the incorporation of impurities by setting the film formation rate to 1 nm / second or more, preferably 10 nm / second or more. Alternatively, when the intentional additive element is contained in an amount of more than 1 atomic%, it is desirable to prevent the addition of additional impurities as much as possible by setting the film formation rate to 10 nm / second or more.
[0051]
The film formation conditions may affect the crystal grain size regardless of the amount of impurities. For example, in an alloy film in which about 2 atomic% of Ta is mixed in Al, an amorphous phase is mixed between crystal grains, but the ratio between the crystalline phase and the amorphous phase depends on the film forming conditions. In addition, as the sputtering is performed at a lower pressure, the proportion of the crystal portion increases, the volume resistivity decreases, and the thermal conductivity increases.
The impurity composition or crystallinity in the film depends on the manufacturing method of the alloy target used for sputtering and the sputtering gas (Ar, Ne, Xe, etc.). Thus, the volume resistivity in the thin film state is not determined only by the metal material and the composition. In order to obtain high thermal conductivity, it is desirable to reduce the amount of impurities as described above. On the other hand, pure metals such as Al and Ag tend to be inferior in corrosion resistance and hillock resistance. It is necessary to determine the optimal composition.
[0052]
In order to obtain further high heat conduction and high reliability, it is also effective to make the reflective heat radiation layer 2 and the Ag or Ag alloy layer 8 multilayer. In this case, at least one layer is made of the high thermal conductivity material (low volume resistivity material) having a film thickness of 50% or more of the total film thickness, which substantially contributes to the heat dissipation effect, and the other layers have corrosion resistance and It is configured to contribute to improvement in adhesion to the protective layer and hillock resistance.
More specifically, when Ag having the highest thermal conductivity and low volume resistivity among metals is used, if S (sulfide or the like) is contained in the protective layer adjacent to Ag, the compatibility is poor, and due to sulfurization. Corrosion tends to occur, and there is a tendency for deterioration to be somewhat rapid when overwritten (O / W) repeatedly. In addition, corrosion tends to occur in an accelerated test environment of high temperature and high humidity. Therefore, when using Ag or an Ag alloy as the low volume resistivity material, it is also effective to provide an alloy layer containing Al as a main component as an interface layer between 1 nm and 100 nm between the adjacent protective layers. If this thickness is 5 nm or more, the layer does not have an island-like structure and is easily formed uniformly.
[0053]
As described above, the Al alloy includes, for example, Ta, Ti, Co, Cr, Si, Sc, Hf, Pd, Pt, Mg, Zr, Mo, or Mn in an amount of 0.2 atomic% to 2 atomic%. An alloy is mentioned. If the thickness of the interface layer is less than 1 nm, the protective effect is insufficient, and if it exceeds 100 nm, the heat dissipation effect is sacrificed.
[0054]
Further, when an Ag alloy reflective layer and an Al alloy interface layer are used, it is more preferable to provide an interface oxide layer by oxidizing the Al surface to a thickness greater than 1 nm because Ag and Al are relatively easy to interdiffuse. If the interfacial oxide layer exceeds 5 nm, particularly 10 nm, it becomes a thermal resistance, which is not preferable because the function as a reflective heat radiating layer having a very high heat dissipation, which is the original purpose, is impaired.
[0055]
In order to define the high heat conductivity reflective heat radiation layer 2 and Ag or Ag alloy layer 8 exhibiting good characteristics in the present invention, it is possible to directly measure the respective heat conductivity, Pass / fail can be estimated using electrical resistance. This is because in a material such as a metal film in which electrons mainly control heat or electric conduction, the thermal conductivity and electric conductivity have a good proportional relationship. The electric resistance of the thin film is represented by a resistivity value normalized by the film thickness or the area of the measurement region. The volume resistivity and the area resistivity can be measured by a normal four-probe method and are defined by JIS K 7194. This method provides data that is much simpler and more reproducible than actually measuring the thermal conductivity of a thin film.
[0056]
As the characteristics of the reflective heat radiation layer 2 and the Ag or Ag alloy layer 8 that are preferable in the present invention, the volume resistivity is 20 nΩ · m or more and 150 nΩ · m or less, more preferably 20 nΩ · m or more and 100 nΩ · m or less. is there. A material having a volume resistivity of less than 20 nΩ · m is substantially difficult to obtain in a thin film state. Even if the volume resistivity is larger than 150 nΩ · m, the area resistivity can be lowered if, for example, a thick film exceeding 300 nm is used, but according to the study by the present inventors, such a high volume resistivity is obtained. Even if only the sheet resistivity is lowered with a rate material, a sufficient heat dissipation effect cannot be obtained. This is probably because the heat capacity per unit area increases in the thick film. In addition, such a thick film takes a long time to form a film and increases material costs, which is not preferable from the viewpoint of manufacturing cost, and further, the microscopic flatness of the film surface is deteriorated. It is preferable to use a low volume resistivity material that provides a sheet resistivity of 0.2 or more and 0.9Ω / □ or less at a film thickness of 300 nm or less, and most preferably 0.5Ω / □. In the case of Ag or Ag alloy layer 8, 20 nm or less is desirable from the viewpoint of transmittance.
[0057]
The multilayering of the reflective heat dissipation layer 2 or the Ag or Ag alloy layer 8 is also effective for obtaining a desired sheet resistivity with a desired film thickness by combining a high volume resistivity material and a low volume resistivity material. . The volume resistivity adjustment by alloying can simplify the sputtering process by using an alloy target, but it also increases the target manufacturing cost and consequently the raw material ratio of the medium. Accordingly, it is also effective to obtain a desired volume resistivity by multilayering a thin film of pure Al or pure Ag and a thin film of the additive element itself. If the number of layers is up to about three layers, the initial apparatus cost increases, but the individual medium costs may be suppressed. The reflective heat-dissipating layer 2 is a multilayer reflective heat-dissipating layer composed of a plurality of metal films, the total film thickness is 40 nm or more and 300 nm or less, and 50% or more of the thickness of the multilayer reflective heat-dissipating layer is 20 nΩ · m or more, 150 nΩ · It is preferable to use a metal thin film layer of m or less (may be a multilayer).
[0058]
Next, in the configuration in which the cover substrate 13 is provided as shown in FIG. 1 and a high NA objective lens is used, the thickness of the cover substrate 13 is 0.3 mm or less, more preferably 0.06 to 0.20 mm. Therefore, a sheet shape is preferable. Materials include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, etc. A polycarbonate resin and an acrylic resin, which are excellent in characteristics and cost, are preferable. Examples of a method for forming a thin substrate using the transparent sheet include a method of attaching a transparent sheet via an ultraviolet curable resin or a transparent double-sided pressure-sensitive adhesive sheet. Alternatively, an ultraviolet curable resin may be applied on the protective layer and cured to form a thin substrate.
[0059]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.
[0060]
Reference example 1
In the layer structure shown in FIG. 3, a reflective heat radiation layer 22 (AgCuPtPd), a first protective layer 23 (ZnSSiO ₂ ), a first recording layer 24 (Ag ₅ In ₅ Sb ₆₅ Te ₂₅ ), a first 2 protective layer 25 (ZnSSiO ₂ ), resin intermediate layer 26 (polycarbonate), third protective layer 27 (Be ₂ O ₃ ), Ag or Ag alloy layer 28 (AgCuPtPd), fourth protective layer 29 (ZnSSiO ₂ ), 2 For evaluation, each layer comprising a recording layer 30 (Ge ₅ Ag ₂ Sb ₇₀ Te ₂₃ ), a fifth protective layer 31 (ZnSSiO ₂ ), an adhesive layer 32 (acrylic double-sided adhesive), and a cover substrate 33 (polycarbonate) is formed. A phase change recording medium was produced. The layers other than the polycarbonate resin intermediate layer 26 and the acrylic double-sided adhesive layer 32 were formed by sequentially forming each layer from the substrate 21 side while controlling the thickness by a sputtering method.
[0061]
The thickness of each constituent layer was controlled as follows.
Substrate 21: 1.1 mm, reflective heat dissipation layer 22: 120 nm, first protective layer 23: 10 nm, first recording layer 24: 10 nm, second protective layer 25: 100 nm, resin intermediate layer 26:30 μm, third protective layer 27 : 120 nm, Ag or Ag alloy layer 28: 10 nm, fourth protective layer 29: 10 nm, second recording layer 30: 6 nm, fifth protective layer 31: 100 nm, adhesive layer 32: using acrylic double-sided adhesive, cover substrate 33: 60 μm.
[0062]
Reference example 2
In Reference Example 1 , the material of the third protective layer 27 was changed from Be ₂ O ₃ to a mixed system composition of Al ₂ O ₃ and SiO ₂ , and the configuration and thickness of Reference Example 1 were completely the same for evaluation. A phase change recording medium was produced.
[0063]
Reference example 3
In Reference Example 1 , the structure and thickness of Example 1 were exactly the same as in Example 1 except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to a mixed system composition of MgO and SiO _2. A recording medium was produced.
[0064]
Reference example 4
In the reference example 1 , except that the material of the third protective layer 27 is changed from Be ₂ O ₃ to a mixed system composition of In ₂ O ₃ and ZnO, the configuration and thickness of the reference example 1 are exactly the same, and the evaluation phase is changed. A changeable recording medium was produced.
[0065]
Reference Example 5
In Reference Example 1 , the configuration and thickness of Reference Example 1 were evaluated in exactly the same manner except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to a mixed composition of In ₂ O ₃ , ZnO, and SnO. A phase change type recording medium was prepared.
[0066]
Comparative Example 1
A phase change recording medium for evaluation was produced in the same manner as in Reference Example 1 except that the material of the third protective layer 27 was changed from Be ₂ O ₃ to ZnSSiO ₂ in Reference Example 1 . .
[0067]
Table 1 summarizes the constituent materials of each layer of the phase change recording medium for evaluation in Reference Examples 1 to 5 and Comparative Example 1.
[0068]
[Table 1]

[0069]
<Evaluation> The phase change recording medium for evaluation produced in Reference Examples 1 to 5 and Comparative Example 1 was irradiated with a focused light beam using an optical system having a wavelength of 402 nm and a numerical aperture NA of 0.85, and the linear velocity was 6 m. The initial jitter (Jitter), archival characteristics, and O / W characteristics were evaluated under the conditions of / s and 0.130 μm / bit. The results are shown in Table 2.
[0070]
[Table 2]

[0071]
Evaluation criteria are as follows.
Archival characteristics: Time (H) in which the jitter rises to 20% or more when stored at 80 ° C. and 85% (RH).
O / W characteristics: The number of overwriting (O / W) times when the jitter (Jitter) increase due to overwriting (O / W) reaches 20%.
[0072]
As a result of the evaluation test, all of the phase change recording media for evaluation of Reference Examples 1 to 5 exhibited excellent archival characteristics (1000H to 2000H) and O / W characteristics (10000 times to 20000 times). Each of the characteristics 100H (archival characteristics) and 1000 times (O / W characteristics) both showed 10 times or more performance.
[0073]
【The invention's effect】
The present invention has a layer structure in which at least a first recording structure layer, a resin intermediate layer, and a second recording structure layer are provided on a substrate, and the first recording structure layer includes a reflective heat radiation layer, The first recording layer is composed of a first protective layer, a first recording layer, and a second protective layer, and the second recording structural layer is formed in order from the resin intermediate layer side, a third protective layer, an Ag or Ag alloy layer, a fourth protective layer, and a second recording layer. A third protective layer, wherein the first recording layer and the second recording layer contain at least SbTe, and the linear expansion coefficient of the third protective layer is 3.0 × 10 ⁻⁶ to 10 × 10 ^−6. And a phase change type recording medium that exhibits excellent O / W characteristics, archival characteristics, and high-density recording performance without generating noise such as jitter due to a configuration in which the light transmittance is 80% or more. Provided.
In addition, the component for forming the third protective layer of the present invention may be Be ₂ O ₃ , a mixed system composition of Al ₂ O ₃ and SiO ₂ , a mixed system composition of MgO and SiO ₂ , or In ₂ O ₃ and Thermal composition at the time of O / W by adopting a mixed system composition of ZnO, a mixed system of In ₂ O ₃ and SnO ₂ (ITO), or a mixed system composition of In ₂ O ₃ , ZnO and SnO ₂ A phase change recording medium capable of high-density recording is provided, which can cope with volume changes, and thereby has good archival characteristics and improved O / W characteristics.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a layer structure showing an example for explaining a phase change recording medium of the present invention.
FIG. 2 is a diagram showing the relationship between the linear expansion coefficient of the third protective layer 7 and the number of O / W times of the second recording layer 10 in the embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a layer structure of a phase change recording medium for evaluation in an example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 Reflection heat radiation layer 3 1st protective layer 4 1st recording layer 5 2nd protective layer 6 Resin intermediate layer 7 3rd protective layer 8 Ag or Ag alloy layer 9 4th protective layer 10 2nd recording layer 11 5th protection Layer 12 Adhesive layer 13 Cover substrate 21 Substrate (polycarbonate)
22 Reflective heat dissipation layer (AgCuPtPd)
23 First protective layer (ZnSSiO ₂ )
24 First recording layer (Ag ₅ In ₅ Sb ₆₅ Te ₂₅ )
25 Second protective layer (ZnSSiO ₂ )
26 Resin intermediate layer (polycarbonate)
27 Third protective layer (Be ₂ O ₃ )
28 Ag or Ag alloy layer (AgCuPtPd)
29 Fourth protective layer (ZnSSiO ₂ )
30 Second recording layer (Ge ₅ Ag ₂ Sb ₇₀ Te ₂₃ )
31 Fifth protective layer (ZnSSiO ₂ )
32 Adhesive layer (acrylic double-sided adhesive)
33 Cover substrate (polycarbonate)
100 First recording composition layer 200 Second recording composition layer

Claims (1)

At least a first recording configuration layer, a resin intermediate layer, and a second recording configuration layer are sequentially provided on the substrate, and the first recording configuration layer sequentially includes a reflective heat radiation layer, a first protective layer, and a first protection layer. The recording layer is composed of a second protective layer, and the second recording constituent layer is, in order from the resin intermediate layer side, a third protective layer, an Ag or Ag alloy layer, a fourth protective layer, a second recording layer, and a fifth protective layer. A phase change type recording medium comprising: the first recording layer and the second recording layer containing at least SbTe;
The component forming the third protective layer is a mixed composition of In ₂ O ₃ and SnO ₂ ,
A phase change recording medium, wherein the third protective layer has a linear expansion coefficient of 3.0 × 10 ⁻⁶ to 10 × 10 ⁻⁶ and a light transmittance of 80% or more.

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