JP4090419B2 - Optical recording medium - Google Patents

Description

  The present invention relates to a write-once optical recording medium, and more particularly, to an optical recording medium capable of reducing a manufacturing cost while improving light resistance and obtaining a reproduction signal having a good C / N ratio. The present invention relates to a recording medium.

  Conventionally, as a recording medium for recording digital data, an optical recording medium represented by a CD or a DVD has been widely used, and in recent years, it is a next generation type having a larger capacity and a higher data transfer rate. Development of optical recording media has been actively conducted.

  These optical recording media are ROM-type optical recording media of a type in which data cannot be added or rewritten, such as CD-ROM or DVD-ROM, and data can be additionally written, such as CD-R or DVD-R. However, it can be roughly divided into a write-once type optical recording medium of a type in which data cannot be rewritten and a rewritable type optical recording medium of a type in which data can be rewritten, such as CD-RW and DVD-RW. it can.

  As is well known, in a ROM type optical recording medium, data is generally recorded by prepits formed on a substrate in the manufacturing stage. In a rewritable type optical recording medium, For example, a phase change material is used as the recording layer material, and data is generally recorded by utilizing a change in optical characteristics based on a change in the phase state.

  In the write-once type optical recording medium, organic materials such as cyanine dyes, phthalocyanine dyes, and azo dyes are used as the recording layer material, and the chemical change, physical change, or both of them are used. It is common for data to be recorded using changes in optical properties based on it.

  However, the organic dye may be deteriorated by irradiation with sunlight or the like, and when the organic dye is used as the recording layer material, it is not easy to improve the reliability for long-term storage. Therefore, in order to increase the reliability for long-term storage, it is required to use materials other than organic dyes for the recording layer of the write-once type optical recording medium. In order to meet this demand, what is described in Patent Document 1 is known as an example in which the recording layer is made of a material other than an organic dye.

In the write-once type optical recording medium described in the same patent document, two inorganic material layers are laminated to form a recording layer, and the two inorganic material layers are formed as main components by irradiating a laser beam. The elements contained are mixed, and eutectic crystallization is caused in this mixing process. In this way, when the materials of the inorganic material layer laminated in two layers are mixed and eutectic crystallized, the optical characteristics are different between the eutectic crystallized region and the other regions. Can be used to record data.
JP 62-204442 A

  However, in the write-once type optical recording medium described in Patent Document 1, two inorganic material layers are stacked, and data is recorded by using a mixture of these two inorganic material layers. Therefore, two layers are required to form one recording layer, and there is a problem that the manufacturing cost of the optical recording medium increases.

  Further, in the write-once type optical recording medium described in the patent document, there is a difference in optical characteristics between a recording mark formed by mixing two eutectic material layers and eutectic crystallization and other regions. Since it is not so large, there is also a problem that it is difficult to record data so that a reproduction signal having a good C / N ratio can be obtained.

  Especially for next-generation optical recording media that can increase the data recording density and achieve a very high data transfer rate, the beam spot diameter of the laser beam used for data recording and reproduction is extremely high. Since it is required to narrow down and the difference between the recording mark and the optical characteristics of the area other than the recording mark is sufficiently large, it is extremely possible to obtain a reproduction signal having a good C / N ratio. It was difficult.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical recording medium capable of reducing the manufacturing cost while improving the light resistance and obtaining a reproduction signal having a good C / N ratio. It is.

Such an object of the present invention includes a substrate, a light transmission layer, and a recording layer formed between the substrate and the light transmission layer, and the recording layer includes Ni, Cu, Si, Ti, Ge, Zr, At least one metal element M selected from the group consisting of Nb, Mo, In, Sn, W, Pb, Bi, Zn and La, S or O, and at least selected from the group consisting of Mg, Al and Ti This is achieved by an optical recording medium containing one kind of metal element and containing at least one kind of metal element selected from the group consisting of S or O and Mg, Al and Ti in the form of a compound .

According to the present invention, the recording layer is at least one metal element selected from the group consisting of Ni, Cu, Si, Ti, Ge, Zr, Nb, Mo, In, Sn, W, Pb, Bi, Zn, and La. At least one metal element selected from the group consisting of a simple substance of M, S or O, and Mg, Al, and Ti, and at least one metal element selected from the group consisting of S or O, Mg, Al, and Ti hints in the form of compounds, because it is composed of a single recording film formed of an inorganic material, while increasing the light resistance, it is possible and to reduce the manufacturing cost of the optical recording medium.

In the present invention, the recording layer containing a metal element M and S also O, when the laser beam is Ru is irradiated, the bonded metal elements M and S also O, crystals of the compound is produced Thus, data is recorded.

Thus, when data is recorded, in the reflectance of the recording layer with respect to the laser beam, the reflectance difference between the region where the single element of the metal element M and the S or O compound is crystallized and the other region is calculated. Therefore, according to the present invention, it is possible to obtain a reproduction signal having a good C / N ratio.

When the recording layer contains a 7B group element such as F or Cl, the reactivity is too high, so that it reacts with the metal element M without irradiating the recording laser beam. When a 5B group element such as P or P is included , the reactivity is too weak to react with the metal element M, and the recording sensitivity may be deteriorated.

In contrast, the recording layer, sometimes contain O or S are both Group 6B, if also reactive is too high, nor too weak, as desired, is reacted with a metal element M It is preferable because crystallization can occur.

  In the present invention, the recording layer further contains at least one metal element selected from the group consisting of Mg, Al, Ti and Zn.

  In the present invention, when the recording layer contains Mg, the Mg content is preferably 18.5 atomic percent to 42 atomic percent, more preferably 20 atomic percent to 37 atomic percent, and Al When Al is included, the Al content is preferably 11 atomic% to 70 atomic%, more preferably 18 atomic% to 56 atomic%, and when Ti is included, the Ti content is 8 atomic% to 38 atomic% is preferable, and 10 atomic% to 36 atomic% is more preferable.

  In a further preferred embodiment of the present invention, the recording layer is configured to record data using a laser beam having a wavelength of 380 nm to 450 nm and to reproduce the recorded data.

  Since such a recording layer exhibits good optical characteristics with respect to a laser beam having a wavelength of 380 nm to 450 nm, data is recorded using the laser beam having a wavelength of 380 nm to 450 nm, and the recorded data is reproduced. It is preferable.

  According to the present invention, it is possible to provide an optical recording medium capable of reducing the manufacturing cost while improving the light resistance and obtaining a reproduction signal having a good C / N ratio.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic perspective view of an optical recording medium 10 according to a preferred embodiment of the present invention, and FIG. 2 is a schematic enlarged view of a portion indicated by A in FIG.

  As shown in FIG. 1, the optical recording medium 10 according to the present embodiment is formed in a disc shape having an outer diameter of about 120 mm and a thickness of 1.2 mm. As shown in FIG. A support substrate 11, a recording layer 12, and a light transmission layer 13.

  The support substrate 11 functions as a support for ensuring the mechanical strength required for the optical recording medium 10.

  The material for forming the support substrate 11 is not particularly limited as long as it can function as a support for the optical recording medium 10. The support substrate 11 can be formed of glass, ceramics, resin, or the like, for example. Of these, a resin is preferably used from the viewpoint of ease of molding. Examples of such resins include polycarbonate resins, acrylic resins, epoxy resins, polystyrene resins, polyethylene resins, polypropylene resins, silicone resins, fluorine resins, ABS resins, and urethane resins. Among these, polycarbonate resin is particularly preferable from the viewpoints of processability, surface roughness, and the like. In this embodiment, the support substrate 11 is formed of polycarbonate resin. In this embodiment, since the laser beam L is irradiated through the light incident surface 13a located on the opposite side to the support substrate 11, it is necessary that the support substrate 11 has light transmittance. Not.

  In this embodiment, the support substrate 11 has a thickness of about 1.1 mm.

  As shown in FIG. 2, grooves 11 a and lands 11 b are alternately formed on the surface of the support substrate 11. The grooves 11a and / or lands 11b formed on the surface of the support substrate 11 function as a guide track for the laser beam L when recording data and reproducing data.

  The depth of the groove 11a is not particularly limited, but is preferably set to 10 nm to 40 nm, and the pitch of the groove 11a is not particularly limited, but is set to 0.2 μm to 0.4 μm. It is preferable to do.

  As shown in FIG. 2, a recording layer 12 is formed on the surface of the support substrate 11.

  The recording layer 12 is a recording layer for recording data, and is composed of a single recording film.

  In this embodiment, the recording layer 12 includes at least one metal element selected from the group consisting of Ni, Cu, Si, Ti, Ge, Zr, Nb, Mo, In, Sn, W, Pb, Bi, Zn, and La. And an element of S or O.

  The recording layer 12 preferably has a thickness of 8 nm to 60 nm, and more preferably has a thickness of 10 nm to 45 nm.

  When the thickness of the recording layer 12 is less than 8 nm, the C / N ratio of the reproduction signal when the data recorded on the recording layer 12 is reproduced becomes insufficient. On the other hand, when the thickness of the recording layer 12 exceeds 60 nm. This is not preferable because the film formation time becomes long and the productivity may be deteriorated.

  Thus, according to this embodiment, the recording layer 12 is at least selected from the group consisting of Ni, Cu, Si, Ti, Ge, Zr, Nb, Mo, In, Sn, W, Pb, Bi, Zn, and La. Since it is composed of a single type of metal element and a single recording film made of an inorganic material containing an element of S or O, the reliability of optical recording media can be improved while improving reliability for long-term storage. Manufacturing costs can be reduced.

  The light transmission layer 13 is a layer that transmits a laser beam, and one surface thereof forms a light incident surface 13a.

  The light transmission layer 13 is preferably formed to have a thickness of 10 μm to 300 μm, and more preferably formed to have a thickness of 50 μm to 150 μm.

  The material for forming the light transmission layer 13 is not particularly limited, but it is preferable to use an ultraviolet curable resin such as acrylic or epoxy.

  The light transmission layer 13 needs to have a sufficiently high light transmittance because the laser beam L passes through when recording and reproducing data.

  The optical recording medium 10 having the above configuration is manufactured as follows.

  First, a support substrate 11 having grooves 11a and lands 11b on the surface is formed by injection molding using a stamper.

  Next, the recording layer 12 is formed on the surface of the support substrate 11 on which the grooves 11a and lands 11b are formed. Here, the recording layer 12 is a simple substance of at least one metal element selected from the group consisting of Ni, Cu, Si, Ti, Ge, Zr, Nb, Mo, In, Sn, W, Pb, Bi, Zn, and La. Of these, a case where the metal element is formed so as to include a single metal element of Zn or La will be described as an example.

A target containing ZnS · SiO ₂ or La · Si · O · N as a main component and a target containing at least one metal element selected from the group consisting of Mg, Al and Ti as a main component on the surface of the support substrate 11 Is used to form the recording layer 12 by a sputtering method.

Here, in this specification, ZnS · SiO ₂ means a mixture of ZnS and SiO _{2 , and} La · Si · O · N also means a mixture of La, Si, O, and N.

Thus, using a target containing ZnS · SiO ₂ or La · Si · O · N as a main component and a target containing at least one metal element selected from the group consisting of Mg, Al and Ti as a main component, When the recording layer 12 is formed by sputtering, at least one metal element selected from the group consisting of Mg, Al, and Ti acts as a reducing agent in the film formation process of the recording layer 12, and as a result, the recording layer 12, Zn or La metal element exists in a single form.

Specifically, for example, when a target containing ZnS · SiO ₂ as a main component and a target containing Mg as a main component are used as targets, Mg is a reducing agent for ZnS contained in ZnS · SiO _2. As a result, Zn is uniformly dispersed in the recording layer 12. At this time, Mg used as the reducing agent is separated from ZnS or bonded to a part of S contained in ZnS to form MgS. Therefore, Zn is contained in the recording layer 12 in a single form.

In this embodiment, when the recording layer 12 contains ZnS · SiO ₂ as a main component, the molar ratio of ZnS to SiO ₂ in the recording layer 12 is preferably 40:60 to 80:20, and 65 : 35 to 75:25 is more preferable.

When the ZnS molar ratio is 40% or more, both the reflectance and light transmittance of the recording layer 12 with respect to the laser beam can be improved, and when the ZnS molar ratio is 80% or less. Can reliably prevent the recording layer 12 from cracking due to stress. Further, if the molar ratio of ZnS and SiO _{2 in} the recording layer 12 is set to 65:35 to 75:25, the laser of the recording layer 12 can be more effectively prevented from generating cracks. It becomes possible to further improve the reflectance and light transmittance with respect to the beam.

Further, in this embodiment, when the recording layer 12 include a sputtering target, the La · Si · O · N as main components, _SiO 2, _Si 3 _{N 4} constituting the La · Si · O · N And La ₂ O ₃ , the molar ratio of SiO ₂ to the sum of Si ₃ N ₄ and La ₂ O ₃ is preferably 10:90 to 50:50, and SiO ₂ , Si ₃ N ₄ and La ₂ More preferably, the molar ratio of O ₃ is 30:50:20.

When the molar ratio of SiO ₂ is less than 10%, the recording layer 12 tends to crack, and when the molar ratio of SiO ₂ exceeds 50%, the reflection of the recording layer 12 is reduced due to a decrease in refractive index. If the molar ratio of the sum of Si ₃ N ₄ and La ₂ O ₃ is 50% to 90%, a high refractive index can be obtained and cracking can be prevented. Because it can. Considering these, it is more preferable that the molar ratio of SiO ₂ , Si ₃ N ₄ and La ₂ O ₃ is 30:50:20 as a sputtering target.

Further, when _the molar ratio of Si ₃ N ₄ is 30% or more and the molar ratio of La ₂ O ₃ is 50% or more, the residual stress of the film generated when the recording layer 12 is formed may be reduced. Since it is possible, it is more preferable.

  Further, in this embodiment, when the recording layer 12 contains Mg, the Mg content is preferably 18.5 atomic% to 42 atomic%, and preferably 20 atomic% to 37 atomic%. More preferably, when Al is contained, the content of Al is preferably 11 atomic% to 70 atomic%, more preferably 18 atomic% to 56 atomic%, and when Ti is contained, The content of is preferably 8 atomic% to 38 atomic%, more preferably 10 atomic% to 36 atomic%.

  Further, as shown in FIG. 1, an ultraviolet curable resin is applied onto the surface of the recording layer 12 by a spin coating method to form a coating film, and the coating film is irradiated with ultraviolet rays to transmit light. Layer 13 is formed.

  Thus, the optical recording medium 10 is manufactured.

  Data is recorded on the optical recording medium 10 according to the present embodiment configured as described above as follows.

  In this embodiment, when recording data on the optical recording medium 10, a laser beam L having a wavelength λ of 380 nm to 450 nm is irradiated through the light incident surface 13a of the light transmission layer 13, and the recording layer 12 is irradiated with the laser beam L. The laser beam L is focused.

  FIG. 3 is a diagram showing a pulse train pattern of a laser power control signal for controlling the power of the laser beam L when data is recorded on the recording layer 12 of the optical recording medium 10.

  As shown in FIG. 3, the pulse train pattern of the laser power control signal used for recording data on the recording layer 12 of the optical recording medium 10 has a level corresponding to the recording power Pw, a level corresponding to the intermediate power Pm, and Between the three levels corresponding to the base power Pb, a level-modulated pulse is formed. The recording power Pw, the intermediate power Pm, and the base power Pb satisfy the relationship Pw> Pm ≧ Pb. Correspondingly, the three levels of the pulse train pattern are also determined.

  When data is recorded on the recording layer 12, a laser beam L whose power is modulated in accordance with a laser power control signal having a pulse train pattern shown in FIG. 3 is applied to the recording layer 12 via the light transmission layer 13. Irradiated.

  Thus, when the recording layer 12 is irradiated with the laser beam L, the phase state of the recording layer 12 changes and data is recorded on the recording layer 12.

That is, when the laser beam L whose power is set to the recording power Pw is irradiated, the recording layer 12 is heated, and the amorphous state contained in the recording layer 12 is heated in the heated recording layer 12 region. A metal element of Zn or La reacts with S or O to become ZnS or La ₂ O ₃ in a crystalline state, and further, ZnS in an amorphous state present around the crystalline ZnS or La ₂ O ₃ or La ₂ O ₃ grows crystal using ZnS or La ₂ O ₃ in a crystalline state as a nucleus.

Thus, the region where the crystalline ZnS or La ₂ O ₃ is generated differs greatly from the other regions in the reflectivity with respect to the laser beam L having a wavelength λ of 390 nm to 450 nm. Can be recorded.

  Therefore, according to this embodiment, it is possible to obtain a reproduction signal having a good C / N ratio when data recorded on the recording layer 12 is reproduced.

Here, the power of the recording power Pw of the laser beam L is such that, by irradiating the laser beam L, the Zn or La metal element and the S or O element contained in the recording layer are reliably combined, ZnS or La ₂ O ₃ is set to a power at which crystals are generated.

  Further, the power of the intermediate power Pm and the base power Pb is set to a low power at which the Zn or La metal element and the S or O element contained in the recording layer 12 are not combined.

  In particular, the level of the base power Pb is such that the heated region irradiated with the laser beam L of the recording power Pw is quickly cooled by switching the level of the laser beam L to the base power Pb. Set to a very low level.

  As described above, data is recorded on the recording layer 12 of the optical recording medium 10.

  As described above, according to this embodiment, the recording layer 12 is composed of a single recording film that includes a metal element of Zn or La and an element of S or O and is formed of an inorganic material. Therefore, it is possible to reduce the manufacturing cost of the optical recording medium while improving the reliability for long-term storage.

Furthermore, in this embodiment, Zn or La metal element and S or O element are combined to produce ZnS or La ₂ O ₃ crystals, whereby data is recorded on the recording layer 12. When the data is recorded in this way, the reflectance of the recording layer 12 with respect to the laser beam, the region where the ZnS or La ₂ O ₃ crystal is generated, and the other regions Therefore, it is possible to obtain a reproduction signal having a good C / N ratio.

  Examples are given below to clarify the effects of the present invention.

  First, a polycarbonate substrate having a thickness of 1.1 mm and a diameter of 120 mm and having grooves and lands formed on the surface with a groove pitch of 0.32 μm was manufactured by an injection molding method.

  Next, the polycarbonate substrate was set in a sputtering apparatus, and a recording layer having a thickness of 30 nm was formed by sputtering using both a target mainly composed of ZnS and a target mainly composed of Mg. As a result of measuring the composition of the recording layer after forming the recording layer, the contents of Zn, S and Mg were 39.1 atomic%, 47.0 atomic% and 13.9 atomic%, respectively. The contents of Zn, S and Mg contained in the recording layer were adjusted to Rh tube, tube voltage = 50 kV, tube current = 50 mA using a fluorescent X-ray apparatus “RIX2000” (trade name) manufactured by Rigaku Denki Kogyo Co., Ltd. X-rays were generated and measured by the FP method.

  Then, an ultraviolet curable acrylic resin was applied on the surface of the recording layer by a spin coating method to form a coating film, and this was irradiated with ultraviolet rays to form a 100 μm light transmission layer.

  Thus, an optical recording disk sample # 1 was produced.

  By changing the film forming power of the ZnS target and the Mg target, the contents of Zn, S and Mg contained in the recording layer were set to 35.8 atomic%, 44.2 atomic% and 20.0 atomic%, respectively. Except for the above, an optical recording disk sample # 2 was produced in the same manner as the optical recording disk sample # 1.

  Except that the contents of Zn, S and Mg contained in the recording layer were 32.9 atomic%, 42.8 atomic% and 24.3 atomic%, respectively, the same as the optical recording disk sample # 1 An optical recording disk sample # 3 was produced.

  Except that the contents of Zn, S and Mg contained in the recording layer were 28.9 atomic%, 37.6 atomic% and 33.5 atomic%, respectively, the same as the optical recording disk sample # 1 An optical recording disk sample # 4 was produced.

  Except that the contents of Zn, S and Mg contained in the recording layer were 29.9 atomic%, 30.2 atomic% and 39.9 atomic%, respectively, the same as the optical recording disk sample # 1 An optical recording disk sample # 5 was produced.

  Except that the contents of Zn, S and Mg contained in the recording layer were 25.2 atomic%, 25.7 atomic% and 49.1 atomic%, respectively, the same as the optical recording disk sample # 1 An optical recording disk sample # 6 was produced.

  Except that the contents of Zn, S and Mg contained in the recording layer were 20.4 atomic%, 20.3 atomic% and 59.3 atomic%, respectively, the same as the optical recording disk sample # 1 An optical recording disk sample # 7 was produced.

  Next, the optical recording disk sample # 1 is set in an optical recording medium evaluation apparatus “DDU1000” (trade name) manufactured by Pulstec Industrial Co., Ltd., and data is recorded on the recording layer of the optical recording disk sample # 1 under the following conditions. Was recorded.

  The laser beam was condensed on the recording layer of the optical recording disk sample # 1 through the light transmission layer to form a recording mark having a length of 8T, and data was recorded. Here, the recording power Pw of the recording laser beam was 3 mW.

  Next, the recording power Pw of the laser beam was gradually increased from 3 mW within the range of 3 mW to 12 mW, and data was sequentially recorded on the recording layer.

Modulation method: (1,7) RLL
Recording linear velocity: 5.3 m / sec Channel bit length: 0.12 μm
Channel clock: 66 MHz
Recording method: on-groove recording Next, using the above-described optical recording medium evaluation apparatus, the recording layer of the optical recording disk sample # 1 was irradiated with a laser beam set at the reproduction power, and the data recorded on the recording layer , And the C / N ratio of the reproduction signal when the recording mark having the length of 8T was reproduced was measured. Here, the reproducing power of the reproducing laser beam was set to 0.3 mW. At this time, the reproducing laser beam was used by changing the same laser power as that of the recording laser beam.

  The measurement results are shown in Table 1. Here, Table 1 shows the recording power Pw and the recording power Pw when the minimum C / N ratio is obtained when data recorded with the recording power Pw changed in the range of 3 mW to 12 mW is reproduced. The C / N ratio of the reproduction signal when reproducing the data recorded in is shown.

  Next, using the same optical recording medium evaluation apparatus, the recording layers of the optical recording disk samples # 2 to # 7 are sequentially irradiated with a laser beam, and the recording of 8T length is performed as in the optical recording disk sample # 1. Marks were formed and data was recorded.

  When recording data, the recording power Pw of the laser beam is gradually increased from 3 mW within the range of 3 mW to 12 mW as in the case of the optical recording disk sample # 1, and the data is sequentially transferred to the recording layer. Recorded.

  Next, using the same optical recording medium evaluation apparatus, the data recorded on the recording layers of the optical recording disk samples # 2 to # 7 are reproduced, and the reproduction signal C when reproducing the recording mark having a length of 8T is reproduced. The / N ratio was measured.

  The measurement results are shown in Table 1. Here, Table 1 shows the recording power Pw and the recording power Pw when the minimum C / N ratio is obtained when data recorded with the recording power Pw changed in the range of 3 mW to 12 mW is reproduced. The C / N ratio of the reproduction signal when reproducing the data recorded in is shown.

表１に示されるように、Ｍｇの含有量が２０原子％ないし４０原子％の範囲内である光記録ディスクサンプル＃２ないし＃５においては、記録層に記録したデータを再生したときの再生信号のＣ／Ｎ比が、いずれも、４０ｄＢ以上となり、きわめて高いＣ／Ｎ比の再生信号を得られることが判明した。

As shown in Table 1, in the optical recording disk samples # 2 to # 5 in which the Mg content is in the range of 20 atomic% to 40 atomic%, the reproduction signal when the data recorded on the recording layer is reproduced. The C / N ratios of both were 40 dB or more, and it was found that a reproduction signal with an extremely high C / N ratio could be obtained.

  In the optical recording disk comparative sample # 1 in which the Mg content is less than 20 atomic%, the C / N ratio of the reproduction signal when reproducing the data recorded on the recording layer is 10.6 dB, In the optical recording disk samples # 6 and # 7 whose content exceeds 40 atomic%, the C / N ratio of the reproduction signal when the data recorded on the recording layer is reproduced is 35.7 dB and 36.6 dB, respectively. In both cases, it has been found that a reproduction signal of 30 dB or more can be obtained.

  When forming the recording layer, the optical recording disc sample # 8 was prepared in the same manner as the optical recording disc sample # 1 except that a target containing Al as the main component was used instead of the target containing Mg as the main component. Produced. As a result of measuring the composition of the recording layer after forming the recording layer, the contents of Zn, S, and Al were 39.7 atomic%, 50.3% atomic%, and 10.0 atomic%, respectively.

  By changing the deposition power of the ZnS target and the Al target, the contents of Zn, S and Al contained in the recording layer were set to 35.7 atomic%, 45.4 atomic% and 18.9 atomic%, respectively. An optical recording disk sample # 9 was produced in the same manner as the optical recording disk sample # 8 except for the above points.

  Except that the contents of Zn, S and Al contained in the recording layer were 29.7 atomic%, 39.0 atomic% and 31.3 atomic%, respectively, the same as the optical recording disk sample # 8 An optical recording disk sample # 10 was produced.

  Except that the contents of Zn, S and Al contained in the recording layer were 25.3 atomic%, 33.5 atomic% and 41.2 atomic%, respectively, the same as the optical recording disk sample # 8 An optical recording disk sample # 11 was prepared.

  Except that the contents of Zn, S and Al contained in the recording layer were 22.0 atomic%, 22.4 atomic% and 55.5 atomic%, respectively, the same as the optical recording disk sample # 8 An optical recording disk sample # 12 was produced.

  Except that the contents of Zn, S and Al contained in the recording layer were 13.9 atomic%, 13.7 atomic% and 72.5 atomic%, respectively, the same as the optical recording disk sample # 8 An optical recording disk sample # 13 was produced.

  Next, in the same manner as in Example 1, 8T-long recording marks were formed on the recording layers of the optical recording disk samples # 8 to # 13 to record data. When recording data, the recording power Pw of the laser beam is gradually increased from 3 mW within the range of 3 mW to 12 mW as in the case of the optical recording disk sample # 1, and the data is sequentially transferred to the recording layer. Recorded.

  Next, in the same manner as in Example 1, the data recorded on the recording layers of the optical recording disk samples # 8 to # 13 are reproduced, and the C / W of the reproduction signal when the recording mark having the length of 8T is reproduced. The N ratio was measured.

  The measurement results are shown in Table 2. Here, Table 2 shows the recording power Pw and the recording power Pw when the minimum C / N ratio is obtained when data recorded with the recording power Pw changed in the range of 3 mW to 12 mW is reproduced. The C / N ratio of the reproduction signal when reproducing the data recorded in is shown.

表２に示されるように、Ａｌの含有量が１８原子％ないし５６原子％の範囲内である光記録ディスクサンプル＃９ないし＃１２においては、記録層に記録したデータを再生したときの再生信号のＣ／Ｎ比が、いずれも、４０ｄＢ以上となり、きわめて高いＣ／Ｎ比の再生信号を得られることが判明した。

As shown in Table 2, in the optical recording disk samples # 9 to # 12 in which the Al content is in the range of 18 atomic% to 56 atomic%, the reproduction signal when the data recorded in the recording layer is reproduced. The C / N ratios of both were 40 dB or more, and it was found that a reproduction signal with an extremely high C / N ratio could be obtained.

  Also in the optical recording disk sample # 8 in which the Al content is less than 18 atomic% and the optical recording disk sample # 13 in which the Al content exceeds 56 atomic%, reproduction when data recorded on the recording layer is reproduced. It has been found that a reproduction signal having a C / N ratio of 30 dB or more can be obtained for each of the signals.

  When forming the recording layer, the optical recording disc sample # 14 is formed in the same manner as the optical recording disc sample # 1 except that a target containing Ti as the main component is used instead of the target containing Mg as the main component. Produced. Here, as a result of measuring the composition of the recording layer after forming the recording layer, the contents of Zn, S, and Ti were 43.6 atomic%, 48.8 atomic%, and 7.6 atomic%, respectively. .

  By changing the deposition power of the ZnS target and the Ti target, the contents of Zn, S and Ti contained in the recording layer were set to 41.8 atomic%, 47.9 atomic% and 10.3 atomic%, respectively. An optical recording disk sample # 15 was produced in the same manner as the optical recording disk sample # 14 except for the above points.

  Except that the contents of Zn, S and Ti contained in the recording layer were 38.3 atomic%, 46.9 atomic% and 14.8 atomic%, respectively, the same as the optical recording disk sample # 14 An optical recording disk sample # 16 was produced.

  Except that the contents of Zn, S and Ti contained in the recording layer were 35.7 atomic%, 42.2 atomic% and 22.1 atomic%, respectively, the same as the optical recording disk sample # 14 An optical recording disk sample # 17 was produced.

  Except for the point that the contents of Zn, S and Ti contained in the recording layer were 30.8 atomic%, 33.8 atomic% and 35.4 atomic%, respectively, the same as the optical recording disk sample # 14 An optical recording disk sample # 18 was produced.

  Except for the point that the contents of Zn, S and Ti contained in the recording layer were 28.2 atomic%, 32.5 atomic% and 39.3 atomic%, respectively, the same as the optical recording disk sample # 14 An optical recording disk sample # 19 was produced.

  Next, in the same manner as in Example 1, 8T-long recording marks were formed on the recording layers of the optical recording disk samples # 14 to # 19 to record data. Here, when recording data, the recording power Pw of the laser beam is gradually increased from 3 mW within the range of 3 mW to 12 mW in the same manner as in the case of the optical recording disk sample # 1, and the recording layers are sequentially formed. Data was recorded.

  Next, in the same manner as in Example 1, the data recorded on the recording layers of the optical recording disk samples # 14 to # 19 are reproduced, and the C / W of the reproduction signal when the recording mark having the length of 8T is reproduced. The N ratio was measured.

  The measurement results are shown in Table 3. Here, Table 3 shows the recording power Pw and the recording power Pw when the minimum C / N ratio is obtained when data recorded with the recording power Pw changed in the range of 3 mW to 12 mW is reproduced. The C / N ratio of the reproduction signal when reproducing the data recorded in is shown.

表３に示されるように、Ｔｉの含有量が１０原子％ないし３６原子％の範囲内である光記録ディスクサンプル＃１５ないし＃１８においては、記録層に記録したデータを再生したときの再生信号のＣ／Ｎ比が、いずれも、４０ｄＢ以上となり、きわめて高いＣ／Ｎ比の再生信号を得られることが判明した。

As shown in Table 3, in the optical recording disk samples # 15 to # 18 in which the Ti content is in the range of 10 atomic% to 36 atomic%, the reproduction signal when the data recorded in the recording layer is reproduced. The C / N ratios of both were 40 dB or more, and it was found that a reproduction signal with an extremely high C / N ratio could be obtained.

  In the optical recording disk comparative sample # 14 in which the Ti content is less than 10 atomic%, the C / N ratio of the reproduction signal when reproducing the data recorded on the recording layer is 18.6 dB. In the optical recording disk comparative sample # 19 whose content exceeds 36 atomic%, the C / N ratio of the reproduction signal when reproducing the data recorded on the recording layer is 38.2 dB, and the C / N ratio is 30 dB or more. It has been found that a reproduction signal having can be obtained.

The optical recording disk sample # was used except that a target containing a mixture of ZnS and SiO ₂ having a molar ratio of 80:20 as a main component was used instead of the target containing ZnS as a main component in forming the recording layer. In the same manner as in Example 1, an optical recording disk sample # 20 was produced. Here, as a result of measuring the composition of the recording layer after forming the recording layer, the contents of Zn, Si, Mg, O, and S were 21.8 atomic%, 10.8 atomic%, and 18.3 atomic atom, respectively. %, 21.6 atomic%, and 27.5 atomic%. However, since O is contained in the substrate, it is difficult to measure O, and the content of O is assumed to be in the state of SiO ₂ , and the atomic% is twice the Si content. It was said that. Hereinafter, the content of O is the same.

  The contents of Zn, Si, Mg, O and S contained in the recording layer are 21.5 atomic%, 10.1 atomic%, 20.8 atomic%, 20.1 atomic% and 27.5 atomic%, respectively. An optical recording disk sample # 21 was prepared in the same manner as the optical recording disk sample # 20 except for the above points.

  The contents of Zn, Si, Mg, O and S contained in the recording layer are respectively 22.6 atomic%, 9.3 atomic%, 25.0 atomic%, 18.6 atomic% and 24.5 atomic%. Except for the above, an optical recording disk sample # 22 was produced in the same manner as the optical recording disk sample # 20.

  The contents of Zn, Si, Mg, O, and S contained in the recording layer are respectively 19.1 atomic%, 8.0 atomic%, 33.9 atomic%, 16.0 atomic%, and 23.0 atomic%. Except for the above, an optical recording disk sample # 23 was produced in the same manner as the optical recording disk sample # 20.

  The contents of Zn, Si, Mg, O and S contained in the recording layer are respectively 18.9 atomic%, 7.3 atomic%, 37.0 atomic%, 14.5 atomic% and 22.3 atomic%. An optical recording disk sample # 24 was produced in the same manner as the optical recording disk sample # 20 except for the above points.

  The contents of Zn, Si, Mg, O, and S contained in the recording layer are 16.1 atomic%, 7.1 atomic%, 42.5 atomic%, 14.2 atomic%, and 20.1 atomic%, respectively. Except for the above, an optical recording disk comparison sample # 25 was produced in the same manner as the optical recording disk sample # 20.

  Next, in the same manner as in Example 1, 8T-long recording marks were formed on the recording layers of the optical recording disk samples # 20 to # 25 to record data. Here, when recording data, the recording power Pw of the laser beam is gradually increased from 3 mW within the range of 3 mW to 12 mW in the same manner as in the case of the optical recording disk sample # 1, and the recording layers are sequentially formed. Data was recorded.

  Thus, after irradiating the recording layer of each optical recording disk sample with the laser beam having the recording power Pw, the state of the recording layer of each optical recording disk sample was confirmed using a transmission electron microscope. In the region irradiated with the laser beam, ZnS crystal growth was observed.

  Next, in the same manner as in Example 1, the recorded data C was reproduced on the recording layers of the optical recording disc samples # 20 to # 25, and the C of the reproduction signal when the recording mark having the length of 8T was reproduced. The / N ratio was measured.

  The measurement results are shown in Table 4. Table 4 shows the recording power Pw and the recording power Pw when the minimum C / N ratio can be obtained when data recorded with the recording power Pw changed in the range of 3 mW to 12 mW is reproduced. The C / N ratio of the reproduction signal when reproducing the data recorded in is shown.

表４に示されるように、Ｍｇの含有量が２０原子％ないし４０原子％の範囲内である光記録ディスクサンプル＃２１ないし＃２４においては、記録層に記録したデータを再生したときの再生信号のＣ／Ｎ比が、いずれも、４０ｄＢ以上となり、きわめて高いＣ／Ｎ比の再生信号を得られることが判明した。

As shown in Table 4, in the optical recording disk samples # 21 to # 24 in which the Mg content is in the range of 20 atomic% to 40 atomic%, the reproduction signal when the data recorded on the recording layer is reproduced. The C / N ratios of both were 40 dB or more, and it was found that a reproduction signal with an extremely high C / N ratio could be obtained.

  When the data recorded on the recording layer was reproduced also in the optical recording disk comparative sample # 20 in which the Mg content is less than 20 atomic% and the optical recording disk comparative sample # 25 in which the Mg content exceeds 40 atomic% The C / N ratio of the reproduced signal of 30.0 dB and 37.9 dB were found to be obtained, and a reproduced signal having a C / N ratio of 30 dB or more can be obtained.

When the recording layer is formed, it is the same as the optical recording disk sample # 1 except that a mixed target of ZnS and SiO ₂ having a molar ratio of 50:50 is used instead of the target containing ZnS as a main component. An optical recording disk sample # 26 was produced. As a result of measuring the composition of the recording layer after forming the recording layer, the contents of Zn, Si, Mg, O, and S were 14.5 atomic%, 16.6 atomic%, 17.8 atomic%, and 33, respectively. 2 atomic% and 17.9 atomic%.

By changing the film formation power of the ZnS and SiO ₂ mixture target and the Al target, the contents of Zn, Si, Mg, O and S contained in the recording layer were changed to 13.1 atomic% and 15.9 atoms, respectively. %, 22.3 atomic%, 31.8 atomic%, and 16.9 atomic%, except that optical recording disk sample # 27 was manufactured in the same manner as optical recording disk sample # 26.

  The contents of Zn, Si, Mg, O and S contained in the recording layer are respectively 12.9 atomic%, 15.0 atomic%, 26.1 atomic%, 30.0 atomic% and 16.0 atomic%. An optical recording disk sample # 28 was produced in the same manner as the optical recording disk sample # 26 except for the above points.

  The contents of Zn, Si, Mg, O and S contained in the recording layer are respectively 11.8 atomic%, 13.2 atomic%, 32.8 atomic%, 26.4 atomic% and 15.8 atomic%. An optical recording disk sample # 29 was produced in the same manner as the optical recording disk sample # 26 except for the above points.

  The contents of Zn, Si, Mg, O and S contained in the recording layer are respectively 9.5 atomic%, 10.7 atomic%, 46.2 atomic%, 21.4 atomic% and 12.2 atomic%. An optical recording disk sample # 30 was produced in the same manner as the optical recording disk sample # 26 except for the above points.

  Next, in the same manner as in Example 1, 8T-long recording marks were formed on the recording layers of the optical recording disk samples # 26 to # 30 to record data. When recording data, the recording power Pw of the laser beam is gradually increased from 3 mW within the range of 3 mW to 12 mW as in the case of the optical recording disk sample # 1, and the data is sequentially transferred to the recording layer. Recorded.

  Next, in the same manner as in Example 1, the data recorded on the recording layers of the optical recording disk samples # 26 to # 30 are reproduced, and the C / W of the reproduction signal when the recording mark having the length of 8T is reproduced. The N ratio was measured.

  The measurement results are shown in Table 5. Here, Table 5 shows the recording power Pw and the recording power Pw when the minimum C / N ratio is obtained when data recorded by changing the recording power Pw in the range of 3 mW to 12 mW is reproduced. The C / N ratio of the reproduction signal when reproducing the data recorded in is shown.

表５に示されるように、Ｍｇの含有量が２０原子％ないし３５原子％の範囲内である光記録ディスクサンプル＃２７ないし＃２９においては、記録層に記録したデータを再生したときの再生信号のＣ／Ｎ比が、いずれも、４０ｄＢ以上となり、非常に高いＣ／Ｎ比の再生信号を得られることが判明した。

As shown in Table 5, in the optical recording disk samples # 27 to # 29 in which the Mg content is in the range of 20 atomic% to 35 atomic%, the reproduction signal when the data recorded in the recording layer is reproduced. The C / N ratios of both were 40 dB or more, and it was found that a reproduction signal with a very high C / N ratio could be obtained.

  In the optical recording disk comparative sample # 26 in which the Mg content is less than 20 atomic%, the C / N ratio of the reproduction signal when reproducing the data recorded in the recording layer is 16.6 dB, Also in the optical recording disk sample # 30 whose content exceeds 35 atomic%, the C / N ratio of the reproduction signal when reproducing the data recorded in the recording layer is 35.0 dB, and the C / N ratio of 30 dB or more is obtained. It has been found that a reproduced signal having the same can be obtained.

In forming the recording layer, instead of a target containing ZnS as a main component, a mixed target of La ₂ O ₃ , SiO ₂ and Si ₃ N ₄ having a molar ratio of 20:30:50 was used, and An optical recording disk sample # 31 was produced in the same manner as the optical recording disk sample # 1 except that the thickness of the recording layer was 17 nm. As a result of measuring the composition of the recording layer after forming the recording layer, the contents of La, Si, Mg, O, and N were 6.2 atomic%, 24.1 atomic%, 23.1 atomic%, and 24, respectively. 0.6 atomic percent and 22.0 atomic percent.

  Next, in the same manner as in Example 1, 8T-long recording marks were formed on the recording layer of the optical recording disk sample # 31 to record data. When recording data, the recording power Pw of the laser beam is gradually increased from 3 mW within the range of 3 mW to 12 mW as in the case of the optical recording disk sample # 1, and the data is sequentially transferred to the recording layer. Recorded.

  Next, in the same manner as in Example 1, the data recorded on the recording layer of the optical recording disk sample # 31 was reproduced, and the C / N ratio of the reproduction signal when the recording mark having the length of 8T was reproduced is It was measured.

  The measurement results are shown in Table 6. Here, Table 6 shows the recording power Pw and the recording power Pw when the minimum C / N ratio is obtained when data recorded by changing the recording power Pw in the range of 3 mW to 12 mW is reproduced. The C / N ratio of the reproduction signal when reproducing the data recorded in is shown.

表６に示されるように、光記録ディスクサンプル＃３１においては、記録層に記録したデータを再生したときの再生信号のＣ／Ｎ比が、４０ｄＢ以上となり、きわめて高いＣ／Ｎ比を有する再生信号を得られることが判明した。

As shown in Table 6, in the optical recording disk sample # 31, the C / N ratio of the reproduction signal when reproducing the data recorded on the recording layer is 40 dB or more, and the reproduction has a very high C / N ratio. It turns out that a signal can be obtained.

  In the above embodiment, when the state of the recording layer was confirmed using an Auger spectroscopic analyzer, an optical film thickness measuring device, and a transmission electron microscope, the recording layer irradiated with a laser beam set to a recording power was used. In this region, the presence of the simple substance of the metal element M and the crystal growth of the compound with the metal element M were observed.

  In this embodiment, it is assumed that the metal layer M is included in the recording layer in a state where the presence of the metal element M is recognized by the following analysis and determination. Further, by the following analysis and judgment, an element that forms a crystal of the compound with the metal element M by combining the state in which the crystal growth of the compound of the metal element M and the element X is recognized with the simple substance of the metal element M X is assumed to be included in the recording layer.

  As a specific method, three optical recording disk samples were prepared under the same conditions, and data was recorded in the same manner as in Example 1 in which data was recorded on a part of the recording layers of the three optical recording disk samples. Was recorded.

Next, for one of the three optical recording disk samples on which data was recorded, the light transmissive layer was cut with a cutter and peeled off to expose the recording layer, and the exposed recording layer surface had a thickness of 20 nm. A dielectric film having a thickness (for example, Al ₂ O ₃ when the recording layer contains ZnS as a main component) and a metal film having a thickness of 100 nm (for example, Al) are sequentially formed by sputtering. did. For the metal film and the dielectric film, it is necessary to use materials other than the metal element M contained in the recording layer so as not to affect the analysis. Here, the metal film is formed in order to prevent the optical recording disk sample from being charged during the measurement using the Auger spectroscopic analyzer. Next, the surface of the metal film of the optical recording disk sample on which the dielectric film and the metal film were formed was locally sputtered to form a hole of about 2 mm so that a part of the surface of the recording layer was exposed.

  Next, in the optical recording disk sample on which the data was recorded, the energy spectrum was measured using an Auger spectroscopic analyzer for the area where the data of the recording layer was recorded and the area where the data of the recording layer was not recorded. Here, when measuring the energy spectrum, an Auger spectroscopic analyzer “SAM680” manufactured by ULVAC-PHI Co., Ltd. was used, and the measurement conditions were set to an acceleration voltage of 5 kV, a Tilt of 30 deg, a sample current of 10 nA, and an Ar ion beam sputter etching acceleration voltage of 2 kV. Set and measure.

  Thus, as a result of measuring the energy spectrum of the recording layer data recorded area and the recording layer data unrecorded area, the metal energy spectrum and the compound energy spectrum are mixed in the unrecorded area. In the region where data was recorded, only the energy spectrum of the compound was observed. From this change in the spectrum, it was determined that the recording layer contained the metal element M.

  Next, the other one of the three optical recording disk samples is cut with a cutter to separate the light transmission layer and the recording layer, and the separated light transmission layer and the recording layer are cured with ultraviolet light. Using the resin, the light transmission layer was adhered to the slide glass so as to be in contact with the slide glass.

  In the optical recording disk sample thus formed, the optical absorptance with respect to a laser beam having a wavelength of 405 nm using an optical film thickness measuring device for the recording layer data recorded area and the recording layer data unrecorded area. Was measured. Here, in measuring the light absorption rate, an optical film thickness measuring device “ETA-RT” (trade name) manufactured by steag ETA-OPTIK Co., Ltd. was used.

  Thus, as a result of measuring the optical absorptance with respect to the laser beam having a wavelength of 405 nm for the recording layer data recorded area and the recording layer data unrecorded area, 34% was obtained in the area where the data was not recorded. It has been found that it has a light absorptance, while the area where data is recorded has a light absorptance of 27%. The decrease in light absorptance is because the free electrons of the metal element M absorb a lot of light and make a compound with the element X, so that the free electrons of the metal element M decrease and the light absorption decreases. It seems that it has become smaller. Similar to the change in the energy spectrum by Auger spectroscopic analysis, it was determined that the recording film contained a single element of the metal element M due to the decrease in the light absorption rate.

  Thus, by measuring the energy spectrum by the Auger spectroscopic analyzer, the energy spectrum of the metal and the energy spectrum of the compound are mixed in the area where the data is not recorded, while the energy spectrum of the compound is mixed in the area where the data is recorded. The result that only the energy spectrum was confirmed was obtained, and the optical absorptance in the area where the data was recorded by the measurement of the optical absorptivity by the optical film thickness measurement device compared to the area where the data was not recorded. From these results, the presence of the simple substance of the metal element M in the recording layer and the region of the recording layer irradiated with the laser beam for recording indicate that the simple substance of the metal element M is the element X. It was judged that the crystals of the compound were produced by the combination.

  Next, the electron diffraction pattern of the recording mark was measured for the remaining one of the three optical recording disk samples on which the data was recorded, using a transmission electron microscope apparatus. At this time, as the transmission electron microscope, “JEM-3010” (trade name) manufactured by JEOL Ltd. was used, and the acceleration voltage was set to 300 kV.

  Here, the optical recording disk sample was cut using a microtome to prepare a sample for a transmission electron microscope. As a result of measuring the electron diffraction pattern of the recording layer in the cut section, a ZnS broad diffraction ring was observed in the area where data was not recorded, whereas a ZnS diffraction spot was observed in the area where data was recorded. Admitted. From these results, it was determined that crystallization of ZnS was generated in the region of the recording layer irradiated with the recording laser beam.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

For example, in the embodiment shown in FIG. 1 and FIG. 2, at least one metal selected from the group consisting of ZnS · SiO ₂ or La · Si · O · N as a main component and Mg, Al and Ti The recording layer 12 is formed by a sputtering method using a target containing an element as a main component. As a result of film formation, a Zn or La metal element M and a metal element M are formed on the recording layer 12. It is sufficient that the element of S or O having a property of generating a crystal of a compound with the metal element M in combination with a target of ZnS, MgS, Al The recording layer 12 is formed by sputtering using a target containing at least one metal element selected from the group consisting of Ti and Ti as a main component. You can also.

  In addition, the optical recording medium 10 according to the embodiment shown in FIGS. 1 and 2 includes the light transmission layer 13, but instead of the light transmission layer 13 or on the surface of the light transmission layer 13, A hard coat layer containing the hard coat composition as a main component may be provided, and a lubricant may be added to the hard coat layer in order to impart lubricity and antifouling functions. A lubricating layer containing a lubricant as a main component may be separately provided on the surface of the coat layer.

  Further, in the optical recording medium 10 according to the embodiment shown in FIG. 1 and FIG. 2, the laser beam L is configured to be irradiated to the recording layer 12 through the light transmission layer 13. The invention relates to a DVD type comprising a light transmissive substrate having a thickness of about 0.6 mm, a dummy substrate having a thickness of about 0.6 mm, and a recording layer between the light transmissive substrate and the dummy substrate. The present invention can also be applied to other optical recording media.

FIG. 1 is a schematic perspective view of an optical recording medium 10 according to a preferred embodiment of the present invention. FIG. 2 is a schematic enlarged view of a portion indicated by A in FIG. FIG. 3 is a diagram showing a pulse train pattern of a laser power control signal for controlling the power of the laser beam L when data is recorded on the optical recording medium 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical recording medium 11 Substrate 11a Groove 11b Land 12 Recording layer 13 Light transmission layer

Claims (6)

A recording layer formed between the substrate and the light transmission layer, wherein the recording layer is Ni, Cu, Si, Ti, Ge, Zr, Nb, Mo, In, Sn , At least one metal element M selected from the group consisting of W, Pb, Bi, Zn and La, S or O, and at least one metal element selected from the group consisting of Mg, Al and Ti, An optical recording medium comprising at least one metal element selected from the group consisting of S or O and Mg, Al and Ti in the form of a compound . 2. The optical recording medium according to claim 1, wherein the recording layer contains 18.5 atomic% to 42 atomic% of Mg. 2. The optical recording medium according to claim 1, wherein the recording layer contains 11 atomic% to 70 atomic% of Al. The optical recording medium according to claim 1, wherein the recording layer contains 8 atomic% to 38 atomic% of Ti. The optical recording medium according to any one of claims 1 to 4, wherein the recording layer has a thickness of 8 nm to 60 nm. The optical recording medium according to claim 1, wherein the light transmission layer has a thickness of 10 μm to 300 μm.

Images