JP2011034611A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium wherein recording accuracy is not deteriorated even when variation is generated in recording power. <P>SOLUTION: In the optical recording medium 1 including an information recording layer 20 which is formed on a substrate 10 and in which information is recorded, the information recording layer 20 includes: a recording film 25 whose optical characteristics are changed by irradiation with light and which consists essentially of Bi and O; and a dielectric film 23 formed in contact with the recording film 25 and consisting essentially of SiO<SB>2</SB>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical recording medium in which information is recorded on an information recording layer by irradiation with laser light.

  Conventionally, for viewing digital moving image contents and recording digital data, CD-DA, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD +/- RW, DVD-RAM, Optical recording media such as Blu-ray Disc are widely used. Among these, Blu-ray Disc (BD), which is one of the next-generation DVD standards, sets the wavelength of the laser light used for recording / reproduction to 405 nm and the numerical aperture of the objective lens to 0.85. On the optical recording medium side corresponding to the BD standard, tracks are formed at a pitch of 0.1 to 0.5 μm. In this way, recording / reproduction of 25 GB or more is possible with respect to one information recording layer of the optical recording medium.

  By the way, the capacity of moving images and data is expected to increase more and more in the future. Therefore, a method for increasing the capacity of the optical recording medium by increasing the number of information recording layers in the optical recording medium has been studied. In the BD standard optical recording medium, a technique for realizing a super-large capacity of 200 GB by providing six to eight information recording layers has been reported.

  The information storage mode of the optical recording medium includes three types: a read-only (read only memory) type in which data cannot be added or rewritten, a recordable type in which data can be added only once, and a rewritable type in which data can be rewritten. Broadly divided into types. In write-once type optical recording media, organic dyes have been widely used as recording film materials. However, since they are not suitable for blue or blue-violet short-wavelength laser light, Bi and O have recently been used as recording film materials. A method using an inorganic material containing the material has been proposed (see, for example, Patent Document 1).

Japanese Patent No. 3802040

  However, when a blue or blue-violet laser beam is used to increase the recording density, the recording mark becomes extremely small, and therefore, if the recording power fluctuates, there is a problem that the recording accuracy tends to deteriorate due to the influence. It was.

  In particular, when the information recording layer of the optical recording medium is multilayered, the information recording layer should be designed so that preferable light reflection characteristics can be obtained by appropriately adjusting the light reflectance, light absorption rate, and light transmittance of each information recording layer. I must. Along with this, since the optimum recording power of each information recording layer is different, there may occur a situation in which recording and reproduction cannot always be performed with the optimum recording power for all the information recording layers. In particular, when the number of layers is increased, the recording power is usually set to a high value. Therefore, the information recording layer near the light incident surface side has a problem that the recording power is excessive and the recording accuracy is likely to deteriorate. It was.

  According to an unknown experiment by the present inventors, when an inorganic material containing Bi and O is used as a recording film material of an optical recording medium, it is clarified that an allowable amount with respect to the fluctuation of the recording power is small. In particular, it has been known that when recording / reproduction is performed with high recording power, noise increases rapidly.

  The present invention has been made in view of the above problems, and in an optical recording medium having a recording film using an inorganic material containing Bi and O, the occurrence of noise is suppressed even when the recording power fluctuates. An object of the present invention is to provide an optical recording medium capable of reliably recording and reproducing information.

  The above-mentioned object is achieved by the following means by the inventors' extensive research.

  (1) A substrate and an information recording layer formed on the substrate on which information is recorded, the information recording layer having optical characteristics changed by light irradiation, and containing Bi and O as main components. An optical recording medium comprising: a recording film to be formed; and a dielectric film formed in contact with the recording film and mainly composed of SiO 2.

  (2) The optical recording medium according to (1), wherein the information recording layer further includes a light absorption film formed in contact with the dielectric film.

  (3) The optical recording medium according to (2), wherein the light absorption film contains Fe oxide as a main component.

  (4) The information recording layer further includes a second dielectric film formed on a side opposite to the dielectric film in the recording film, and comprising a second dielectric film mainly composed of SiO2. The optical recording medium according to 2) or (3).

  (5) The dielectric film is characterized in that the total value of the number of Si and O atoms with respect to the total number of atoms constituting the dielectric film is 80% or more. The optical recording medium according to any one of the above.

  (6) The optical recording medium as described in any one of (1) to (5) above, wherein the dielectric film has a thickness of 2 nm or more and 25 nm or less.

  (7) The optical recording according to any one of (1) to (6) above, wherein the recording film has 63% or more of O atoms with respect to all the atoms constituting the recording film. Medium.

  (8) The optical recording medium according to any one of (1) to (7), wherein the recording film contains Bi-O as a main component.

  (9) The recording film is Bi-MO (where M is Mg, Ca, Y, Dy, Ce, Tb, Ti, Zr, V, Nb, Ta, Mo, W, Mn, Fe, Zn, Selected from Al, In, Si, Ge, Sn, Sb, Li, Na, K, Sr, Ba, Sc, La, Nd, Sm, Gd, Ho, Cr, Co, Ni, Cu, Ga, Pb The optical recording medium according to any one of (1) to (8) above, comprising at least one element as a main component.

  (10) The information recording layer includes a plurality of information recording layers on which information is recorded, and the multilayer information recording layer closest to the light incident surface is configured by the information recording layer (1) The optical recording medium according to any one of (9) to (9).

  (11) The optical recording medium as described in (10) above, comprising three or more information recording layers for the multilayer.

  According to the present invention, even if the recording power is increased, an excellent effect that the deterioration of the recording accuracy can be suppressed can be obtained.

1 is a cross-sectional view of an optical recording medium according to an embodiment of the present invention. It is a figure explaining the structure of the optical recording medium in the Example and comparative example of this embodiment. It is a figure explaining the structure of the optical recording medium in the Example. It is a graph which shows the evaluation result of the Example and a comparative example. It is a graph which shows the evaluation result of the Example. It is a graph which shows the evaluation result data of the Example and a comparative example.

  Hereinafter, an optical recording medium according to an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a laminated structure of an optical recording medium 1 according to this embodiment. This optical recording medium 1 is a disc-shaped medium having an outer shape of about 120 mm and a thickness of about 1.2 mm. In the optical recording medium 1, the information recording layer 20 and the cover layer 36 are laminated in this order on one side of the substrate 10. As a data holding form of the information recording layer 20, there are a read-only type in which data is written in advance and cannot be rewritten, and a recording type in which a user can write, and a recording type is adopted here. In the case of the record type, in detail, a write-once (Recordable) type in which data cannot be written again in an area in which data has been written once, and a rewrite in which data can be erased and written again in an area in which data has been written ( Rewritable) type. In this embodiment, the case where the information recording layer 20 is a write-once type is illustrated.

  The substrate 10 is a disk-shaped member having a thickness of about 1100 μm, and various materials such as glass, ceramics, and resin can be used as the material. In addition to the polycarbonate resin, an olefin resin, an acrylic resin, an epoxy resin, a polystyrene resin, a polyethylene resin, a polypropylene resin, a silicone resin, a fluorine resin, an ABS resin, a urethane resin, or the like can be used as the resin. Among these, polycarbonate resin and olefin resin are preferable from the viewpoint of ease of processing and molding, and polycarbonate resin is used in this embodiment. Although not particularly shown, grooves, lands, pit rows, and the like are formed on the surface of the substrate 10 on the information recording layer side according to the application. The grooves and lands serve as a guide track for laser light during data recording. In addition, a recording mark is formed on the information recording layer 20 located on the groove by modulating the energy intensity of the laser light traveling along the groove. Further, the groove plays a role of specifying the medium side address, and can acquire the medium side address at a specific location from the tracking signal.

  The information recording layer 20 includes a light absorption film 22, a second dielectric film 23, a recording film 25, and a first dielectric film 27 in order from the substrate 10 side. Although not specifically shown here, a reflective film, a dielectric film, or the like may be disposed on the substrate side of the light absorption film 22.

  Here, the light absorption film 22 is formed with a film thickness of 4 nm mainly composed of Fe3O4. The light absorption film 22 has a function of absorbing laser light and supplying necessary energy to the recording film 25. In addition to Fe3O4, (Fe2O3, FeO, CrO, Cr2O3, MnO, Mn2O3, MnO2, V2O3, VO2, V2O5, NiO, Nd2O3) or the like can be used as the main component of the light absorption film 22. As will be described later, since the peroxide of Bi-MO is used as the material of the recording film 25 of the present embodiment, the recording film 25 is formed by reactive sputtering. Since the light absorption film 22 may be oxidized during the formation of the recording film 25, it is preferable to use a material having a light absorption characteristic when the light absorption film 22 is in an oxide state.

  The second dielectric film 23 is in direct contact with both the light absorption film 22 and the recording film 25, and is formed with SiO2 as a main component. In addition, it is preferable that the total number of atoms of SiO2 is larger than 60% of the total number of atoms contained in the film because SiO2 is the main component, but more preferably, the total number of atoms of SiO2 is 80% of the total number of atoms. More preferably 90% or more.

  Further, the film thickness of the second dielectric film 23 is 2 nm or more, preferably 5 nm or more, more preferably 10 nm when SiO2 is the main component. On the other hand, the film thickness is preferably 25 nm or less. Thus, by setting the film thickness to 2 nm or more, it is possible to improve the reliability with respect to the fluctuation of the recording power in the recording film 25. Further, by setting the film thickness to 25 nm or less, the energy transfer between the light absorption film 22 and the recording film 25 is not hindered.

  The recording film 25 is formed with a film thickness of 40 nm using a material containing Bi and O as a main component. The recording film 25 functions as an inorganic reaction film, and has different light reflectivity by being melted and mixed by the heat of laser light. Specifically, the recording film 25 is mainly composed of Bi-O or Bi-MO (where M is Mg, Ca, Y, Dy, Ce, Tb, Ti, Zr, V, Nb). , Ta, Mo, W, Mn, Fe, Zn, Al, In, Si, Ge, Sn, Sb, Li, Na, K, Sr, Ba, Sc, La, Nd, Sm, Gd, Ho, Cr, Co And at least one element selected from Ni, Cu, Ga and Pb).

  In particular, the ratio of the number of O atoms to the total number of atoms in the recording film 25 is preferably 62% or more, and more preferably the total number of Bi and O atoms is based on the total number of atoms. 80% or more. By doing so, the recording / reproducing characteristics of the recording film 25 itself can be improved. In the present embodiment, Bi—Ge—O (Bi: Ge: O = 19: 15: 66 at%) is used as the material of the recording film 25.

  The first dielectric film 27 is composed of SiO2 as a main component and has a thickness of 5 nm. The first dielectric film 27 also contributes to improving the reliability with respect to the recording power fluctuation in the recording film 25. The first dielectric film 27 also has a function of making it difficult for moisture in the substrate 10 and external moisture to reach the recording film 25, and suppresses alteration of the recording film 25.

  The cover layer 36 includes the hard coat layer on the outermost surface, and the thickness thereof is set to about 100 μm. As a result, the information recording layer 20 is disposed at a position of about 100 μm from the light incident surface 3A.

  When recording information on the optical recording medium 1, the information recording layer 20 is irradiated with blue or blue-violet laser light. As a result, a recording mark is formed on the recording film 25. Each recording mark has a lower reflectivity than the space portion. The recording power of the laser beam is desirably recorded with a recording power at which 8TCNR is 50 dB or more. As the characteristics of the optical recording medium 1, it is preferable that the allowable range of recording power satisfying 8TCNR of 50 dB or more is wider. This is because the recording mark can be formed with high accuracy even when recording is performed with different recording power (for example, when the recording power changes). More specifically, it is preferable that 8TCNR satisfies 50 dB or more even when recording with a recording power larger than 1.4 times based on the minimum recording power Pws in which 8TCNR satisfies 50 dB or more, More preferably, 8TCNR satisfies 50 dB or more even when recording is performed with a high recording power of 1.5 times or more the same minimum recording power Pws.

  Next, a method for manufacturing the optical recording medium 1 will be described.

  First, a disk-shaped substrate 10 having an outer diameter of about 120 mm and a thickness of about 1.1 mm is formed by injection molding. At this time, an uneven pattern for tracks is formed on one surface of the substrate 10.

  Next, the light absorption film 22 is formed on the surface of the substrate 10 on which the tracks are formed by a vapor phase growth method such as a sputtering method or a vapor deposition method. In addition, when a reflective film is temporarily formed on the substrate 10 side with respect to the light absorption film 22, the reflective film is first formed by a similar sputtering method or the like. The light absorption film 22 is formed along the uneven pattern of the substrate 10.

  Next, the second dielectric film 23 is formed by sputtering or the like. Specifically, the substrate 10 on which the light absorption film 22 is formed is placed in a chamber in which a SiO 2 target is disposed. Further, when a sputtering gas such as Ar or Xe is supplied into the chamber and collides with the SiO 2 target, Si and O 2 particles are scattered and deposited on the light absorption film 22 of the substrate 10. As a result, the second dielectric film 23 is formed with a substantially uniform thickness along the uneven pattern of the track.

  Further, the recording film 25 is formed on the second dielectric film 23 by sputtering or the like. Specifically, the substrate 10 on which the light absorption film 22 and the second dielectric film 23 are formed is placed in a chamber in which Bi and Ge targets are disposed, and O 2 gas is supplied into the chamber. Further, when a sputtering gas such as Ar or Xe is supplied into the chamber and collides with a target of Bi and Ge, particles of Bi and Ge are scattered. The scattered Bi particles and Ge particles react with O 2 in the chamber to be oxidized, and are deposited on the second dielectric film 23 of the substrate 10. Thereby, the recording film 25 is formed with a substantially uniform thickness along the uneven pattern of the track. The ratio of Bi and O in the recording film 25 can be adjusted by adjusting the sputtering conditions. The recording film 25 is preferably composed mainly of Bi and O, but other atoms, compounds, etc. may be mixed as long as the amount is small. Specifically, it is preferable to include Ge as in this embodiment, and broadly, Bi—MO (where M is Mg, Ca, Y, Dy, Ce, Tb, Ti, Zr, V, Nb). , Ta, Mo, W, Mn, Fe, Zn, Al, In, Si, Ge, Sn, Sb, Li, Na, K, Sr, Ba, Sc, La, Nd, Sm, Gd, Ho, Cr, Co , Ni, Cu, Ga, and Pb). The recording film target may be formed by using a Bi-MO mixture target.

  Next, a first dielectric film 27 is formed on the recording film 25 by sputtering, vapor deposition, or the like. The first dielectric film 27 is also formed in the same manner as the second dielectric film 23, and is formed along the uneven pattern of the track. The information recording layer 20 is completed by the light absorbing film 22, the second dielectric film 23, the recording film 25, and the first dielectric film 27.

  Finally, a cover layer 36 is formed with a thickness of 100 μm on the first dielectric film 27 by spin coating, and cured by irradiating with ultraviolet rays or the like. Note that the cover layer 36 may be formed by bonding a pre-manufactured film. Thereby, the optical recording medium 1 is completed.

  According to the optical recording medium 1 of the present embodiment, the information recording layer 20 is formed by being in contact with the recording film 25 containing as a main component a material containing Bi and O, and containing SiO 2 as the main component. Since the second dielectric film 23 is provided, information can be reliably recorded on the recording film 25 even when the recording power fluctuates.

  Further, since the light absorbing film 22 is formed in contact with the second dielectric film 23 on the opposite side of the recording film 25, the heat of the recording laser light is efficiently absorbed and the heat is absorbed. The recording film 25 can be supplied via the two dielectric films 23. In addition, in this way, the two dielectric films 23 that improve the recording power margin in the recording film 25 and the two films of the light absorption film 22 share the function, so that the recording can be performed with higher accuracy in the higher recording power region.・ Reproduction is realized. In particular, by setting the film thickness of the second dielectric film 23 to 2 nm or more, the function of improving the power margin can be sufficiently exerted. On the other hand, by setting the film thickness to 25 nm or less, the light absorption film 22 and the recording film 25. The heat transfer characteristics are not impaired. This makes it possible to achieve both power margin characteristics and highly accurate recording mark formation. Here, the case where the light absorption film 22 is arranged on the second dielectric film 23 is shown, but it is also preferable to arrange the light absorption film on the light incident surface side of the first dielectric film 27.

  Also, according to the present optical recording medium 1, the second dielectric film 23 has a total value of 80% or more of the number of Si and O atoms with respect to the number of all atoms constituting the second dielectric film 23. Power margin characteristics can be improved.

  Further, the information recording layer 20 of the present embodiment is formed in a state in which the first dielectric film 27 mainly composed of SiO 2 is in contact with the recording film 25 on the opposite side of the second dielectric film 23. As described above, by sandwiching the recording film 25 between the dielectric films 23 and 27 mainly composed of two SiO 2, the power margin characteristic of the recording film 25 can be remarkably improved.

  The light absorption film 22 is composed of Fe oxide as a main component, and this Fe oxide has a feature that the light absorption amount is large in either the Fe2O3 film or the Fe3O4 film. Therefore, it is preferable in that a film having a sufficient light absorption function can be formed even if the composition changes due to a slight change in the film formation state.

  Further, according to the present optical recording medium 1, since the recording film 23 has 63% or more of O atoms with respect to all the atoms constituting the recording film 23, blue or blue-violet laser light is used as irradiation light. Even when used, data can be recorded and reproduced reliably.

<Example>
As shown in FIGS. 2 and 3, ten types of optical recording media from Example 1 to Example 10 were manufactured by the same method as the above embodiment. In Examples 1 to 4, the information recording layer 20 has a three-layer structure of the second dielectric film 23, the recording film 25, and the first dielectric film 27 in order to clarify the effect of the dielectric film and the like. The light absorption film 22 is omitted. On the other hand, as Comparative Examples 1 to 3 corresponding thereto, an optical recording medium without a dielectric film mainly composed of SiO 2 was manufactured, and as Comparative Example 4, the atomic ratio of SiO 2 in the dielectric film was 60% or less. An optical recording medium was manufactured.

  Further, in Examples 5 to 12, the optical recording medium including the information recording layer 20 including the light absorption film 22 mainly composed of Fe, or another dielectric film mainly including Al 2 O 3 in the information recording layer 20. An optical recording medium including was manufactured.

  Specifically, as shown in FIG. 2, in the optical recording medium of Example 1, the second dielectric film 23 mainly composed of SiO 2 is 5 nm, the recording film 25 mainly composed of Bi—O is 60 nm, Another dielectric film composed mainly of Al2O3 was formed at 5 nm. The atomic ratio of Bi—O in the recording film 25 at this time was Bi: O = 32 at%: 68 at%. In the optical recording medium of Example 2, the second dielectric film 23 containing SiO2 as the main component is 5 nm, the recording film 25 containing Bi-O as the main component is 60 nm, and the first dielectric film 27 containing SiO2 as the main component. Was formed at 5 nm. The atomic ratio of Bi—O in the recording film 25 at this time was the same as that in the first example. In the optical recording medium of Example 3, the second dielectric film 23 mainly composed of SiO2 is 5 nm, the recording film 25 mainly composed of Bi-Ge-O is 60 nm, and the second dielectric body mainly composed of SiO2. Film 27 was formed at 5 nm. The atomic ratio of Bi—Ge—O in the recording film 25 at this time was Bi: Ge: O = 19 at%: 15 at%: 66 at%. In the optical recording medium of Example 4, the second dielectric film 23 containing SiO 2 as the main component is 5 nm, the recording film 25 containing Bi—Si—O as the main ingredient is 60 nm, and the second dielectric material contains SiO 2 as the main component. Film 27 was formed at 5 nm. The atomic ratio of Bi—Si—O in the recording film 25 at this time was Bi: Si: O = 19 at%: 15 at%: 66 at%.

  On the other hand, in Comparative Example 1, instead of the second dielectric film 23, another dielectric film mainly containing Al2O3 is 5 nm, the recording film 25 mainly containing Bi-O is 60 nm, and the first dielectric film 27 is used. Instead of this, another dielectric film containing Al2O3 as a main component was formed at 5 nm. In Comparative Example 2, another dielectric film containing Al2O3 as a main component instead of the second dielectric film 23 is 5 nm, a recording film containing Pt-O as a main component is used instead of the recording film 25, and the first dielectric is 15 nm. Instead of the body film 27, a dielectric film mainly composed of Al 2 O 3 was formed with a thickness of 5 nm. The atomic ratio of Pt—O in the recording film at this time was Pt: O = 53 at%: 47 at%.

  Further, in Comparative Example 3, the second dielectric film 23 mainly composed of SiO 2 is 5 nm, the recording film mainly composed of Pt—O is replaced with 15 nm instead of the recording film 25, and the first dielectric body mainly composed of SiO 2. Film 27 was formed at 5 nm. The atomic ratio of Pt—O in the recording film at this time was Pt: O = 53 at%: 47 at%.

  Further, in Comparative Example 4, the second dielectric film 23 mainly composed of ZnSSiO2 is 5 nm, the recording film 25 mainly composed of Bi-O is 60 nm, and the first dielectric film 27 mainly composed of ZnSSiO2 is 5 nm. Formed. At this time, the molar ratio of ZnSSiO2 was ZnS: SiO2 = 50%: 50%, and the atomic ratio of Bi—O in the recording film was Bi: O = 32 at%: 68 at%.

  In Example 5, the light absorption film 22 mainly composed of Fe 3 O 4 is 4 nm, the second dielectric film 23 mainly composed of SiO 2 is 5 nm, the recording film 25 mainly composed of Bi—O is 60 nm, and SiO 2 The first dielectric film containing as a main component was 5 nm. The atomic ratio of Bi—O in the recording film 25 at this time was Bi: O = 32 at%: 68 at%. In Example 6, the light absorption film 22 mainly composed of Fe 3 O 4 is 4 nm, the second dielectric film 23 mainly composed of SiO 2 is 5 nm, the recording film 25 mainly composed of Bi—Ge—O is 60 nm, and SiO 2 The first dielectric film containing as a main component was 5 nm. The atomic ratio of Bi—Ge—O in the recording film 25 at this time was Bi: Ge: O = 19 at%: 15 at%: 66 at%. Further, in Example 11 and Example 12, Fe2O3 was adopted as the material of the light absorption film 22 instead of Fe3O4 of Example 5 and Example 6.

  In Example 7, the third other dielectric film mainly composed of Al2O3 is 5 nm, the second dielectric film 23 mainly composed of SiO2 is 2 nm, and the recording film 25 mainly composed of Bi-O is 60 nm. The first dielectric film composed mainly of SiO2 was 5 nm. The atomic ratio of Bi—O in the recording film 25 at this time was Bi: O = 32 at%: 68 at%. In Example 8, compared with Example 7, the film thickness of the second dielectric film 23 was set to 5 nm, and in Example 9, the film thickness of the second dielectric film 23 was set to 10 nm. In Example 10, as compared with Example 5, the light absorption film 22 containing Fe3O4 as a main component was arranged on the cover layer side (first dielectric layer 27 side).

For these Examples 1 to 12 and Comparative Examples 1 to 4, a single signal having a length of 8T was continuously recorded while changing the recording power Pw of the laser beam. Other recording conditions were set as follows.
Laser wavelength: 405 nm
Numerical aperture NA of the objective lens: 0.85
Modulation method: (1, 7) RLL
Recording linear velocity: 4.92 m / sec
Channel bit length: 120 nm
Channel clock: 66 MHz
Recording method: On-groove recording / reproduction power: 0.7 mW
Intermediate power / recording power: 0.35 mW (changed)
Base power: 0.1 mW

Next, using an optical recording medium evaluation apparatus DDU1000 (manufactured by Pulstec Industrial Co., Ltd.), each optical recording medium is sequentially irradiated with laser light under the following conditions, and a recording with a length of 8T recorded on the information recording layer. The C / N ratio (8TCNR) of the reproduction signal when the mark was reproduced was measured. For measurement of the C / N ratio, a spectrum analyzer XK180 (manufactured by Advantest Corporation) was used. The playback conditions were set as follows.
Laser wavelength: 405 nm
Reproduction power Pr: 0.7 mW
Numerical aperture NA of the objective lens: 0.85

  Under these playback conditions, the minimum recording power Pw when 8TCNR is 50 dB is defined as the reference recording power Pws, and the signal quality when the relative recording power (Pw / Pws) is changed from 1 to 1.6. (8TCNR and 8T noise) were evaluated. By doing so, it becomes possible to evaluate the power margin of the optical recording medium when the recording power is increased. The results are shown in FIG. 4, FIG. 5 and FIG. In general, when 8TCNR is 50 dB or more, an evaluation index such as Jitter becomes a practical numerical value. Therefore, it is important to determine quality based on 50 dB.

  As is clear from FIGS. 4A and 4B, in Examples 1 to 4, even when the relative recording power is increased to 1.3 or more, deterioration of 8TCNR (a situation where it becomes less than 50 dB) is suppressed. Moreover, it turns out that the increase in 8T noise is also suppressed. On the other hand, in Comparative Example 1, it can be seen that when the relative recording power is increased to 1.3 or more, 8TCNR deteriorates and 8T noise also increases. That is, even if the relative recording power is increased by bringing the second dielectric film 23 (and the first dielectric film 27) mainly made of SiO2 into contact with the recording film 25 mainly made of Bi-O. It can be seen that the degradation of the signal quality is suppressed.

  In particular, as can be seen from a comparison between Examples 1 and 2, the recording film 25 is formed by contacting the second dielectric film 23 and the first dielectric film 27 on both surfaces of the recording film 25 mainly containing Bi-O. It can be seen that the power margin can be further improved. Further, as can be seen from a comparison between Examples 1 and 2 and Examples 3 and 4, it can be seen that the power margin is further improved when Ge or Si is contained in the recording film 25.

  Further, as can be seen from comparison between Comparative Example 2 and Comparative Example 3, the second dielectric film 23 mainly composed of SiO2 and the first dielectric film 27 are formed on both sides of the recording film mainly composed of Pt-O. However, it turns out that deterioration of signal quality cannot be prevented. That is, the SiO2 dielectric films 23 and 27 contribute to the improvement of the power margin only when the recording film is Bi-O. However, when the recording film is mainly made of a material other than Bi-O, the dielectric film It can be seen that membranes 23 and 27 do not function.

  Further, as can be seen from Comparative Example 4, when the SiO2 atomic content ratio in the dielectric films 23 and 27 is less than 60% and the molar ratio is less than 50%, the deterioration of the signal quality with respect to the increase in the relative recording power can hardly be suppressed. I understand. Further, as can be seen from Examples 7 to 9 in FIGS. 5A and 5B, it can be seen that the larger the film thickness of the second dielectric film 23, the more the recording power margin can be improved.

  Furthermore, as can be seen from a comparison between Example 5 and Example 2 (Comparative Example 1), by providing the light absorption layer 22 with respect to the second dielectric layer 23, the margin of recording power is greatly improved. I understand that Specifically, it can be seen that the margin of the recording power is improved after the relative recording power exceeds 1.4, particularly after exceeding 1.5. This is also evident by comparing Example 6 and Example 3 (Comparative Example 1). As can be seen from a comparison between Example 5 and Example 11 and Example 6 and Example 12, it can be seen that the same effect can be obtained even when Fe2O3 is employed as the material of the light absorption layer 22.

  Further, as can be seen from a comparison between Example 10 and Example 5, it can be seen that the same effect can be obtained even if the light absorption layer 22 is formed in contact with the first dielectric layer 27 side.

  In the above embodiment, the information recording layer on which information is recorded is shown only as a single layer. However, the present invention is also preferably applied to a multilayer optical recording medium having a plurality of information recording layers for multilayers. . At this time, it is desirable to apply the information recording layer shown in the above embodiment to the multilayer information recording layer closest to the light incident surface. The number of multilayer information recording layers is not particularly limited, but is preferably 3 or more, more preferably 4 or more. The optical recording medium of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

  The optical recording medium of the present invention can be applied to various media for recording information by light irradiation.

DESCRIPTION OF SYMBOLS 1 Optical recording medium 10 Substrate 20 Information recording layer 22 Light absorption film 23 1st dielectric film 25 Recording film 27 2nd dielectric film 37 Cover layer

Claims (11)

A substrate,
An information recording layer formed on the substrate and on which information is recorded,
The information recording layer is
A recording film whose optical characteristics are changed by light irradiation, the main component being Bi and O;
A dielectric film formed in contact with the recording film and mainly composed of SiO2,
An optical recording medium comprising: The information recording layer further includes
The optical recording medium according to claim 1, further comprising a light absorption film formed in contact with the dielectric film.   The optical recording medium according to claim 2, wherein the light absorption film contains Fe oxide as a main component. The information recording layer further includes
4. The optical recording medium according to claim 1, further comprising a second dielectric film formed on a side opposite to the dielectric film in the recording film and having SiO 2 as a main component. 5.   5. The dielectric film according to claim 1, wherein the total value of the number of Si and O atoms with respect to the total number of atoms constituting the dielectric film is 80% or more. 6. Optical recording media.   6. The optical recording medium according to claim 1, wherein the film thickness of the dielectric film is 2 nm or more and 25 nm or less.   7. The optical recording medium according to claim 1, wherein the recording film has 63% or more of the number of O atoms with respect to the total number of atoms constituting the recording film.   The optical recording medium according to claim 1, wherein the recording film contains Bi—O as a main component. The recording film is Bi-MO (where M is Mg, Ca, Y, Dy, Ce, Tb, Ti, Zr, V, Nb, Ta, Mo, W, Mn, Fe, Zn, Al, In, , Si, Ge, Sn, Sb, Li, Na, K, Sr, Ba, Sc, La, Nd, Sm, Gd, Ho, Cr, Co, Ni, Cu, Ga, Pb The optical recording medium according to any one of claims 1 to 8, wherein the main element is a seed element. It has a plurality of information recording layers for multiple information recording,
The optical recording medium according to claim 1, wherein the multilayer information recording layer closest to the light incident surface is constituted by the information recording layer.   The optical recording medium according to claim 10, comprising three or more information recording layers for the multilayer.

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