JP2007066403A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium wherein deformation of a substrate is reduced and recording and reproducing characteristics are enhanced. <P>SOLUTION: In the optical information recording medium 100 irradiated with a laser light L having ≤410 nm wavelength from a light transmissive substrate 11 side and having one recording layer 14 made of a phase change material and having 4 to 8 nm thickness and a reflection layer (a heat diffusion layer) 17 made of an Ag alloy and having 5 to 10 nm thickness, the recording layer has 40 to 60% transmittance to the laser light L having ≤410 nm wavelength and 3 to 10% reflectance to the laser light L having ≤410 nm wavelength in such a state that information is not recorded in the recording layer 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical information recording medium, and more particularly to an optical information recording medium having good recording / reproducing characteristics.

In recent years, the amount of information has increased and diversified, and it is desired that the recording medium responsible for this storage has a larger capacity. In particular, expectations for optical information recording media that are excellent in terms of high reliability and the like are very high. Up to now, as means for increasing the capacity of this optical information recording medium, the laser beam to be used has a smaller spot, the track to be recorded is narrower, the line density is increased by the mark edge method, etc., ZCAV (Zoned Constant Angular) The equalization of the density over the entire medium using the (Velocity) method or the like has been studied and realized.
Further, as a means for further increasing the capacity, there has been a method of increasing the recording area by forming a plurality of recording layers. By making the recording layer to be semi-transparent, it is added to the light incident side of the conventional recording layer, and the inner layer can be formed into multiple layers by recording, erasing and reproducing through this semi-transparent layer. ing.

  In general, as an optical information recording medium, a write once optical information recording medium that can be written once and a rewritable optical information recording medium that can be repeatedly written have been developed. In the write-once type optical information recording medium, a recording mark is formed by condensing laser light on a recording layer containing an organic dye compound, exothermic decomposition of the organic dye compound, and deformation of the adjacent substrate surface and reflection layer. Examples of such a recordable optical information recording medium include DVD-R / + R (DVD-Recordable). On the other hand, the rewritable optical information recording medium includes a recording layer containing a phase change material such as GeSbTe. By irradiating the recording layer with laser light, the atomic arrangement of the phase change material reversibly changes between the amorphous phase and the crystalline phase, and information is recorded according to two different atomic arrangement states (see Patent Document 1). . Examples of such a rewritable optical information recording medium include DVD-RW (DVD-ReWriteable), DVD-RAM (DVD-Random Access Memory) and the like.

JP 2005-038568 A

By the way, in the optical information recording medium, a reflection layer (or called a heat dissipation layer in Patent Document 1 or the like) having a sufficient reflectivity with respect to the laser light applied to the recording layer is provided. The reflection layer is usually formed to a thickness of about 100 nm to 150 nm by sputtering Al, Ti or the like in order to reduce the transmission of laser light and suppress energy diffusion.
However, forming a reflective layer having a thickness of about 100 nm to 150 nm by sputtering over a predetermined time is a factor that increases the manufacturing cost.
In addition, if the sputtering time for forming the reflective film having a predetermined thickness is long, the temperature of the substrate surface rises, which causes the substrate to deform and cause the recording / reproduction characteristics of the optical information recording medium to deteriorate. obtain.

The present invention has been made to solve such problems.
That is, an object of the present invention is to provide an optical information recording medium in which deformation of a substrate is reduced and recording / reproducing characteristics are improved.

Therefore, as a result of intensive studies to solve the above-mentioned problems, the present inventors have prepared a reflective layer having a thickness smaller than that of a normal optical information recording medium, and the recording / reproduction characteristics obtained from the optical information recording medium are improved. Based on this finding, the present invention has been completed.
Thus, according to the present invention, a light-transmitting substrate, one recording layer formed on the substrate directly or via another layer and recording information by light transmitted through the substrate, and directly on the recording layer Alternatively, an optical information recording medium comprising a reflective layer provided through another layer and having a light reflectance of 10% or less is provided.
The optical information recording medium to which the present invention is applied adopts such a configuration, thereby reducing the deformation of the substrate and improving the recording / reproducing characteristics.

Here, in the optical information recording medium to which the present invention is applied, it is preferable that the light transmittance of the recording layer is at least 40%.
The reflective layer is preferably formed from a silver alloy.
Further, the wavelength of light used for the optical information recording medium to which the present invention is applied is preferably 410 nm or less.

Next, according to the present invention, one recording layer provided directly on the light-transmitting substrate or via another layer, and a reflective layer laminated on the recording layer directly or via another layer are provided. And an optical information recording medium characterized in that the reflective layer has a thickness of 15 nm or less.
The optical information recording medium to which the present invention is applied preferably has a recording layer thickness of 10 nm or less.
Here, in the optical information recording medium to which the present invention is applied, it is preferable that information having one recording layer be recorded in advance in a burst cutting area (BCA). By recording information with one recording layer on the BCA, the drive device records whether the semitransparent recording layer with a thickness of 10 nm or less is a single-layer medium or a multi-layer medium. -You can know in advance before erasing and playing.

Furthermore, according to the present invention, there is provided an optical information recording medium that irradiates light having a wavelength of 410 nm or less from the light-transmitting substrate side, wherein one recording layer having a light transmittance of 40% to 60% And a reflective layer having a reflectance of 3% to 10% when no information is recorded on the recording layer.
At this time, the thickness of the reflective layer is preferably 5 nm to 10 nm. The recording layer preferably has a thickness of 4 nm to 8 nm.

  In the optical information recording medium obtained by the present invention, the deformation of the substrate is reduced and the recording / reproducing characteristics are improved.

Hereinafter, the best mode (embodiment) for carrying out the present invention will be described. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.
An optical information recording medium to which the present embodiment is applied is a substrate incident type optical information recording medium in which information is recorded / reproduced by recording / reproducing light having a wavelength of 410 nm or less incident from a light-transmitting substrate surface side. It has the following layer structure. That is, as an optical information recording medium, one recording layer formed directly or via another layer on a substrate made of a light transmissive material, and a reflectance of 10 nm or less of light transmitted through the substrate of 10 nm or less. It is characterized by having a reflective layer that is not more than%.
Next, a specific embodiment of an optical information recording medium to which this embodiment is applied will be described with reference to the drawings. The drawings used here are used only for explaining the present embodiment, and do not represent the actual size.

(Optical information recording medium)
FIG. 1 is a schematic sectional view for explaining an optical information recording medium 100 (here, an example of a DVD-RAM) to which the present embodiment is applied. 1 shows an optical information recording medium 100 formed in a physical format based on DVD-RAM standard version 2.0 (hereinafter sometimes referred to as Ver. 2). As shown in FIG. 1A, an optical information recording medium 100 has a structure in which an information recording substrate 10 having an information recording layer 10R and a dummy substrate 20 having no information recording layer are bonded by an adhesive layer 30. Have.
Next, the information recording substrate 10 will be described. As shown in FIG. 1B, the information recording substrate 10 is formed on a substrate 11 on which a laser beam L having a wavelength of 410 nm or less is incident and a surface on the substrate 11 opposite to the surface on which the laser beam L is incident. Information recording layer 10R. Here, the surface of the substrate 11 is a DVD-RAM standard Ver. 2 in a physical format. In addition, the information recording layer 10R is formed on a substrate 11 with a first protective layer 12, a first interface layer 13, a single recording layer 14 containing a phase change material, a second interface layer 15, a second protective layer 16, and a reflective layer. A layer (thermal diffusion layer) 17, a transmittance adjusting layer 18, and a UV protective layer 19 are sequentially laminated.

(Substrate 11)
Here, the substrate 11 is formed of, for example, a light transmissive resin such as polycarbonate resin, and is formed in a disk shape having an inner diameter (center hole) of 15 mm, an outer diameter of 120 mm, and a thickness of 0.6 mm. The surface of the substrate 11 is 4.7 GB DVD-RAM standard Ver. The tracking pre-groove 11a having a track pitch of 615 nm and a groove depth of 65 nm is formed in a spiral shape in a physical format based on No. 2. The pre-groove 11a is configured such that grooves and lands are alternately connected continuously. The recording method is land / groove recording in which a land and a groove are automatically switched once per round. Furthermore, an embossed pit header is formed between the land and the groove.

Although not shown, the physical format is DVD-RAM standard Ver. The data region of the substrate 11 formed based on 2 is divided into 35 zones (zone 1, zone 2, zone 3... Zone 33, zone 34, zone 35) concentrically in the radial direction. A ZCLV (Zone Constant Linear Velocity) method in which the rotation speed is constant in each zone is adopted. Each zone is divided by a plurality of sectors in which land / groove recording is performed, and a header by embossed pits is formed at the head of the sector. In the innermost zone 1, there are 17 sectors per track, and in the outermost zone 35 there are 41 sectors (DVD-RAM standard Ver. 2).
Further, the sector is divided into a header area formed at the head part, a mirror area, and a 2048-byte recording area, and one sector is constituted by these. Further, the header area is divided into four areas (first area to fourth area), and exists between the groove and the land. The first region and the second region are disposed on the outer peripheral side of the land track as viewed from the land track, and the third region and the fourth region are disposed on the inner peripheral side of the land track. The beam spot detects an address by the land / groove wobble and the embossed pit formed in the header area.

(Recording layer 14)
Examples of the phase change material included in the recording layer 14 include a SnGeSbTe alloy, a GeSbTe alloy, and a BiGeTe alloy. In the present embodiment, a BiGeTe target is sputtered in an Ar gas atmosphere and is formed with a thickness of 10 nm or less, preferably 4 nm to 8 nm. By irradiating the recording layer 14 with a laser beam L having a wavelength of 410 nm or less, the atomic arrangement of the phase change material reversibly changes between the amorphous phase and the crystalline phase, and information is recorded according to two different atomic arrangement states. .
In the present embodiment, the optical information recording medium 100 having the recording layer 14 made of a phase change material is described. However, the present invention is also applicable to, for example, a write once optical information recording medium having a recording layer containing an organic dye. can do.
In the present embodiment, the recording layer 14 has a transmittance of 40% or more, preferably 40% to 60%, more preferably 45% to 55%, for laser light L having a wavelength of 410 nm or less incident from the substrate 11. It has a special feature. When the transmittance of the recording layer 14 is within this range, the recording layer 14 can be used as a single-layer recording medium in which the amount of use of the phase change material and the like constituting the recording layer 14 is reduced, and the L0 layer has a sequentially laminated structure. Can be used as it is as the L0 layer in the single-sided incident type two-layer recording medium to which the L1 layer having the reverse laminate structure is attached.

(First protective layer 12, second protective layer 16)
The first protective layer 12 and the second protective layer 16 are layers for protecting the recording layer 14. The first protective layer 12 is usually formed with a thickness of 10 nm to 100 nm by sputtering (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%). Similarly, the second protective layer 16 is formed to a thickness of 3 nm to 15 nm by sputtering (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%).

(First interface layer 13, second interface layer 15)
The first interface layer 13 is a layer for preventing constituent elements of both layers from entering, diffusing and chemically reacting between the first protective layer 12 and the recording layer 14. The first interface layer 13 is usually formed with a thickness of 1 nm to 5 nm by sputtering (Cr—Ta—O).
The second interface layer 15 is a layer for preventing constituent elements of both layers from entering, diffusing and chemically reacting between the second protective layer 16 and the recording layer 14. The second interface layer 15 is usually formed with a thickness of 1 nm to 5 nm by sputtering a (Cr—Ta—O) target in an Ar gas atmosphere.

(Reflection layer (thermal diffusion layer) 17)
The reflection layer (thermal diffusion layer) 17 is a layer for reflecting the laser beam L having a wavelength of 410 nm or less transmitted through the substrate 11 and releasing heat generated during recording / reproduction of information. The reflective layer (thermal diffusion layer) 17 is formed by sputtering an Al alloy such as Al—Ti or an Ag alloy such as Ag—Nd—Cu or Ag—Ga—Cu. Among these, an Ag alloy is preferable, and an Ag alloy containing 90 mol% or more of Ag is more preferable.
The present embodiment is characterized in that the thickness of the reflective layer (thermal diffusion layer) 17 is 15 nm or less, preferably 5 nm to 10 nm. When the thickness of the reflective layer (thermal diffusion layer) 17 is in this range, the amount of Ag alloy used to configure the reflective layer (thermal diffusion layer) 17 is reduced, and deformation of the substrate 11 is greatly reduced. As a result, the tilt in the optical information recording medium 100 is reduced and the recording / reproducing characteristics are improved.
Further, the reflection layer (thermal diffusion layer) 17 has a reflectance of 10% or less, preferably 3%, of the laser beam L having a wavelength of 410 nm or less incident from the substrate 11 in an unrecorded state in which no information is recorded on the recording layer 14. It is characterized by being 5% to 7%. The optical information recording medium 100 prepared so that the reflectance of the reflection layer (thermal diffusion layer) 17 of the laser beam L having a wavelength of 410 nm or less is in this range includes the L0 layer of the normal stack structure and the L1 of the reverse stack structure. It can be used as the L0 layer in a single-sided incident type two-layer recording medium having a layer attached thereto.

(Transmittance adjustment layer 18),
The transmittance adjusting layer 18 is not always necessary for the optical information recording medium 100 which is originally a single-layer type recording medium. However, by providing the transmittance adjusting layer 18, the optical information recording medium 100 is formed of a normal laminate. It can be used as it is as the L0 layer in the single-sided incident type two-layer recording medium in which the L0 layer having the structure and the L1 layer having the reverse laminate structure are bonded. In the present embodiment, the transmittance adjusting layer 18 is usually formed with a thickness of 10 nm to 60 nm by sputtering (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%).

(UV protective layer 19)
The UV protection layer 19 is a layer for protecting each of the above layers. The UV protective layer 19 is usually formed of an ultraviolet curable resin with a thickness of 10 μm to 70 μm.
The dummy substrate 20 is formed of the same material as the substrate 11 of the information recording substrate 10 and has a disk-like shape (not shown) having an inner diameter (center hole) of 15 mm, an outer diameter of 120 mm, and a thickness of 0.6 mm. is doing.
The adhesive layer 30 is made of, for example, a delayed UV curable adhesive.

  As described above, in the optical information recording medium 100 to which this embodiment is applied, the transmittance of the recording layer 14 is 40% or more, and the reflectance of the laser light L having a wavelength of 410 nm or less is 10% or less. Has been prepared. The optical information recording medium 100 having such a configuration can be used alone as a single-layer recording medium in which the tilt is reduced and the recording / reproducing characteristics are improved by greatly reducing the deformation of the substrate 11. At the same time, it is characterized in that it can be used as it is as the L0 layer in the single-sided incident type two-layer recording medium to which the L1 layer having the reverse laminated structure is bonded.

By the way, in recent years, the spread of optical information recording media to home video recording has rapidly increased. Until now, tape has been the mainstream video recording medium, but by replacing the optical information recording medium, a very convenient function such as follow-up playback can be newly added. However, the price of optical information recording media is still higher than that of tape, and cost reduction is necessary for further spread. The optical information recording medium 100 to which the present embodiment is applied meets such a demand.
That is, of an information recording layer used for an optical information recording medium (hereinafter, abbreviated as a multi-layer medium) capable of reproducing a plurality of information recording layers from one side of the medium, incidence of a light beam used for recording / erasing / reproducing information Information recording of a single-layer optical information recording medium (hereinafter abbreviated as a single-layer medium) in which only one information recording layer is reproduced from one side of the medium, except for the layer located farthest from the side. By using it as a layer, it is usual to use a totally reflective opaque information recording layer in the case of a single layer medium, and to use a translucent one in front of a multi-layer medium for design, development and manufacturing. Cost can be reduced.

  In this case, it is necessary to know in advance whether the translucent information recording layer to be used is a single-layer medium or a multi-layer medium before recording / erasing / reproducing with the driving device. Therefore, if the information recording layer is a single-layer medium or a multi-layer medium, it is recorded on a part of the medium itself, and it is read and discriminated before recording / erasing / reproducing information. Good. For example, in the case of a DVD-RAM, the type of medium may be recorded using a BCA (Burst Cutting Area) zone. Specifically, in the case of a single-layer medium, information that the number of recording layers is one may be recorded.

Hereinafter, the present embodiment will be described more specifically based on examples. Note that this embodiment is not limited to the examples.
(1) Preparation of optical information recording medium An optical information recording medium (DVD-RAM) capable of land-groove recording was prepared as follows. The optical information recording medium was prepared by bonding an information recording substrate having an information recording layer and a dummy substrate with an adhesive. The information recording substrate has a first protective layer, a first interface layer, a recording layer, a second interface layer, a second protective layer, a reflective layer (thermal diffusion layer), a transmittance adjusting layer, and an ultraviolet curable protective layer on the substrate. It has a stacked structure. Here, a substrate made of polycarbonate having a thickness of 0.6 mm is used as the substrate, and grooves are formed with a track pitch of 0.34 μm from the inner periphery of the recording area to 28.6 mm to the outer periphery of 58.6 mm. The track pitch means the distance between the land and the adjacent groove. The track was wobbled with a period of 93 channel bits.
On this substrate surface, by sputtering process, (ZnS) ₈₀ (SiO ₂ ) ₂₀ is 42 nm thick as a first protective layer, Ge ₈₀ Cr ₂₀ -N is 3 nm thick as a first interface layer, and B— Ge—Te was deposited to a thickness of 6 nm, Ge ₈₀ Cr ₂₀ —N as the second interface layer was deposited to a thickness of 1.5 nm, and (ZnS) ₈₀ (SiO ₂ ) ₂₀ was deposited as the second protective layer to a thickness of 7 nm.

Next, Ag—Nd—Cu with a thickness of 8 nm was formed as a reflective layer on the second protective layer by a similar sputtering process.
Subsequently, (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 23 nm is formed as a transmittance adjusting layer on the prepared reflective layer (thermal diffusion layer), and further UV curable on the transmittance adjusting layer. A resin substrate was applied, and a transparent substrate having a thickness of 0.6 mm was bonded while being irradiated with UV to prepare an optical information recording medium having a thickness of 1.2 mm (optical information recording medium 1). The optical information recording medium 1 thus prepared was initialized by irradiating it with a laser beam having an elliptical beam having a wavelength of 810 nm, a beam major axis of 96 μm and a minor axis of 1 μm.
Here, the transmittance of the formed recording layer is 49%. Further, the reflectance of the reflective layer (thermal diffusion layer) when no information is recorded on the recording layer is 6.5%.
In order to perform a comparative experiment, an Ag-Nd-Cu film having a thickness of 15 nm was prepared as a reflective layer (thermal diffusion layer) on the second protective layer (optical information recording medium 2). At this time, the thickness of the first protective layer was adjusted so that the degree of modulation was the same as in the example.
Here, the transmittance of the recording layer formed in the optical information recording medium 2 is 38%. Further, the reflectance of the reflective layer (thermal diffusion layer) when no information is recorded on the recording layer is 12%.

(2) Information recording / reproducing apparatus Information recording / reproducing of the optical information recording medium prepared in advance and the operation of the apparatus are as follows. As a motor control method for recording / reproducing, a ZCLV method is employed in which the number of rotations of the disk is changed for each zone for recording / reproducing.
When information was recorded on the optical information recording medium, recording was performed using the mark edge method and the ETM, RLL (1, 10) modulation method. In this modulation method, information having a mark length of 2T to 11T is recorded on a medium. Note that the clock cycle T during information recording was 15.4 ns, and the recording linear velocity was 5.64 m / sec, which was 1 × speed, and 2 × speed (11.28 m / sec).
A semiconductor laser having a wavelength of 405 nm was used for the optical head mounted on the recording apparatus. In addition, information was recorded by irradiating the recording layer with a laser beam of a laser corresponding to the recording waveform with an objective lens having a numerical aperture (NA) of 0.65.
In addition, the recording apparatus corresponds to a system (land / groove recording system) for recording information in both the groove and the land (area between the grooves), and the L / G servo circuit arbitrarily selects the tracking for the land and the groove. Can do. Reproduction of recorded information was also performed using the optical head described above. When recording is performed on the optical information recording medium, the mark length of the 2T mark, which is the shortest mark, is approximately 0.17 μm, and the mark length of the 8T mark, which is the longest mark, is approximately 0.7 μm. Further, when measuring the error rate, recording and reproduction of a random pattern signal including 2T to 11T described above was performed.

(3) Evaluation Criteria for Optical Information Recording Medium The pre-adjusted optical information recording medium was evaluated for the effects of recording and erasing, signal quality, and cross erase.
(A) Error rate There are three types of error rates (after rewriting a random pattern 10 times) at the recording linear velocity of 1 × speed recording on HD DVD.
(A) Error rate 1: 1 Error rate measured after rewriting a random pattern 10 times on a track (b) Error rate 2: After a random pattern is recorded in order from the inner periphery to the outer periphery of five consecutive tracks, 5 Error rate when measured at the center track of the track (c) Error rate 3: A signal recorded on the adjacent tracks of the center track after recording a random pattern in order from the inner circumference to the outer circumference of five consecutive tracks After being erased (crystallized) by continuous light irradiation, the error rate when measured at the center track The ratio of error rate 1 and error rate 3 can be used to evaluate the degradation of the recording / reproduction characteristics due to cross erase.
(B) Test of rewrite life The error rate after 1000 rewrites in 1 × speed recording was measured.
(C) Evaluation of influence of recrystallization in recorded recording mark 8T single frequency signal at recording linear velocity equivalent to HD DVD 1 × speed and recording linear velocity equivalent to HD DVD 2 × speed is recorded, and amplitude ratio ( (1 × speed recording amplitude / 2 × speed recording amplitude) was measured. At this time, in order to eliminate the influence due to the error of the laser power setting, recording was performed with the optimum power set to 1.7 times the recording start power.
(D) Tilt measurement The mechanical characteristics are shown in Dr. The disc tilt was measured optically using an Argus from Schwab. The measurement area is a radius of 23 mm to 59 mm located in the data portion, and measurement is performed every radius of 1 mm and every 5 degrees in the circumferential direction, and the maximum and minimum tilt amounts in the radial direction and the maximum and minimum tilt amounts in the circumferential direction are determined. The larger value of the maximum and minimum absolute values was determined as the radial and circumferential tilts. The tilt amount indicates the angle between the light incident perpendicularly to the disk reference surface and the reflected light.

Since the prepared optical information recording medium employs land-groove recording, the average value when information is recorded on the land and groove is shown here. The target values for each performance are as follows.
1 × speed recording bit error rate 2: 5 × 10 ⁻⁵ or less 1 × speed recording bit error rate ratio (error rate 3 / error rate 1): 5 or less Bit error rate after 1000 rewrites: 1 × 10 ⁻⁴ or less Radial direction Tilt: 0.7
Circumferential tilt: 0.2

(Example 1, Comparative Example 1)
An optical information recording medium 1 having a thickness of 8 nm, which is a reflection layer (heat diffusion layer) prepared in advance, and an optical information recording medium 2 having a thickness of a reflection layer (heat diffusion layer), which is prepared for a comparative experiment, is 15 nm. The error rate and tilt were measured respectively. The results are shown in Table 1.

From the results shown in Table 1, in the case of the optical information recording medium 1 (Example 1) in which the thickness of the reflective layer (thermal diffusion layer) is 8 nm and the reflectance in an unrecorded state is 10% or less, the tilt (radius) Direction and circumferential direction) are greatly reduced, and as a result, it can be seen that the recording and reproducing characteristics are good. It can also be seen that the error rate shows a numerical result that optical information can be sufficiently recorded and reproduced as an information recording medium.
On the other hand, in the case of the optical information recording medium 2 (Comparative Example 1) in which the thickness of the reflective layer (thermal diffusion layer) is 15 nm and the reflectance of the unrecorded state is 12%, the tilt (radial direction and circumferential direction) is As a result, the recording / reproducing characteristics are not improved.

As described above, as described in the present embodiment, the thickness of the reflective layer (thermal diffusion layer) is reduced so that the reflectance is 10% or less, specifically, the thickness of the reflective layer (thermal diffusion layer). In the optical information recording medium having a thickness of 10 nm or less, the deformation of the substrate is greatly reduced. As a result, the tilt is reduced and the recording / reproducing characteristics are improved.
An optical information recording medium having a reflectance adjusted to 10% or less is an L0 layer in a one-sided incident type two-layer recording medium in which a L0 layer having a normal laminate structure and an L1 layer having a reverse laminate structure are attached. It can be used as it is. That is, by adjusting the reflectance to 10% or less, the transmittance of the laser light irradiated to the L0 layer is ensured, and the L1 layer is irradiated with light necessary for recording and reproduction.

Conventionally, in a single-layer medium having only one recording layer for recording information, the thickness of the reflective layer (thermal diffusion layer) is about 100 nm to 150 nm in order to ensure the reflectance necessary for recording and reproduction. An opaque structure with reduced light transmission was designed. On the other hand, the single-sided incident type two-layer recording medium has an L0 layer so that the light beam reaches the recording layer located farthest from the incident side of the light beam used for recording / erasing / reproducing information. It was necessary to design a translucent structure.
When an optical information recording medium prepared with a reflectance of 10% or less can be used as it is as the L0 layer in a single-sided incident type two-layer recording medium, both a translucent multi-layer medium and an opaque single-layer medium can be used. It is not necessary to design / develop the image, and only the translucent recording layer can be designed / developed, so that the development cost can be greatly reduced. Furthermore, since production management is simplified, the production cost can be reduced. As a result, an inexpensive optical information recording medium can be supplied to the market.

Further, the recording method for recording information on the optical information recording medium has been specifically described by way of examples. However, the present invention is not limited to this. For example, in this embodiment, recording is performed on an optical information recording medium having a constant rotation speed, but the present invention is not limited to this, and the maximum recording linear velocity is particularly high for an optical information recording medium capable of recording at a wide recording linear velocity. This is effective when recording with.
In this embodiment, the shortest mark length is 0.17 μm and the track pitch is 0.34 μm. However, the present invention is not limited to this, and the track pitch is widened or narrowed, or the shortest mark length is shortened or lengthened. But it is effective.
In this embodiment, land / groove recording is used. However, the present invention is not limited to this. Land recording or groove recording has the same effect.
In this embodiment, ETM, RLL (1, 10) modulation method is used, but other modulation methods such as 8-16 modulation method, RLL (1, 7), RLL (2, 7), NRZI, etc. are also available. Can be used.
In this embodiment, a semiconductor laser having a wavelength of 405 nm is used. However, a similar result can be obtained by using a laser having a longer wavelength, for example, a laser having a wavelength near 650 nm, 780 nm, or 830 nm.
In this embodiment, an objective lens having a numerical aperture of 0.65 is used. However, similar results can be obtained even if a lens having a numerical aperture of 0.45 to 0.85 is used. Similar results can be obtained even if two or more lenses are combined and have a numerical aperture of 0.85 or more. Further, in combination with SIL (Solid Immersion Lens) or the like, the effective numerical aperture is set to 1 or more, and the same effect can be obtained in near-field recording using evanescent light by SIL.

It is a schematic sectional drawing for demonstrating the optical information recording medium (DVD-RAM) to which this Embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Information recording substrate, 10R ... Information recording layer, 11 ... Substrate, 11a ... Pre-groove, 12 ... First protective layer, 13 ... First interface layer, 14 ... Recording layer, 15 ... Second interface layer, 16 ... First 2 protective layer, 17 ... reflective layer (thermal diffusion layer), 18 ... transmittance adjusting layer, 19 ... UV protective layer, 20 ... dummy substrate, 30 ... adhesive layer, 100 ... optical information recording medium

Claims (10)

A light transmissive substrate;
One recording layer that is formed on the substrate directly or via another layer and records information by light transmitted through the substrate;
A reflective layer provided directly or via another layer on the recording layer,
An optical information recording medium, wherein the light reflectance is 10% or less.   2. The optical information recording medium according to claim 1, wherein the recording layer has a light transmittance of at least 40%.   The optical information recording medium according to claim 1, wherein the reflective layer is made of a silver alloy.   The optical information recording medium according to claim 1, wherein the wavelength of the light is 410 nm or less. One recording layer provided directly or via another layer on a light transmissive substrate;
A reflective layer laminated on the recording layer directly or via another layer,
An optical information recording medium, wherein the reflective layer has a thickness of 15 nm or less.   6. The optical information recording medium according to claim 5, wherein the recording layer has a thickness of 10 nm or less.   6. The optical information recording medium according to claim 5, wherein information having one recording layer is recorded in advance in a burst cutting area. An optical information recording medium that irradiates light having a wavelength of 410 nm or less from a light-transmitting substrate side,
One recording layer having a light transmittance of 40% to 60%;
An optical information recording medium comprising: a reflective layer having a reflectance of 3% to 10% when no information is recorded on the recording layer.   The optical information recording medium according to claim 8, wherein the reflective layer has a thickness of 5 nm to 10 nm.   9. The optical information recording medium according to claim 8, wherein the recording layer has a thickness of 4 nm to 8 nm.

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