JP2012216267A - Recording device, recording method and optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate adjustment to a correct S/N ratio by multilayer recording and enable the device size to be reduced.SOLUTION: The refractive indices of a first layer 4 and a second layer 5 are made different by appropriately condensing laser beams onto the vicinities of interfaces of an optical recording medium in which a plurality of interfaces are formed between the first layer and the second layer and forming modulation of the refractive indices not so intense as to form a blank mark and/or forming a record mark entailing changes in the shapes of the interfaces, which are thereby caused to function as reflective faces. This enables determination of the presence or absence of any mark (reproduction of recorded signals) to be accomplished by utilizing the optical path length difference (phase difference) of reflected beams arising between any mark-formed part and elsewhere. As this is phase difference detection, it is possible to avoid a tradeoff relationship between enhancement of the reproduced signal level and restraint of crosstalk in the depthwise direction, adjustment to a correct S/N ratio is made easier than by the conventional void recording system. No laser power strong enough to record any void (blank) is needed, and both the light source and the device can be reduced in size.

Description

  The present invention relates to a recording apparatus and method for recording on an optical recording medium in which signal recording / reproduction is performed by light irradiation, and an optical recording medium.

JP 2008-135144 A JP 2008-176902 A

  As optical recording media on which signals are recorded / reproduced by light irradiation, so-called optical disks such as CD (Compact Disc), DVD (Digital Versatile Disc), and BD (Blu-ray Disc: registered trademark) are widely used. .

  Regarding the optical recording media that should be the next generation of optical recording media that are currently popular such as CDs, DVDs, and BDs, the present applicant has previously referred to the so-called Patent Document 1 and Patent Document 2 as described above. A bulk recording type optical recording medium has been proposed.

  Here, the bulk recording refers to, for example, as shown in FIG. 17, an optical recording medium having at least a cover layer 101 and a bulk layer (recording layer) 102 is irradiated with laser light while sequentially changing the focal position. This is a technique for increasing the recording capacity by performing multilayer recording in the layer 102.

  Regarding such bulk recording, the above-mentioned Patent Document 1 discloses a recording technique called a so-called micro-hologram method. In the micro-hologram method, a so-called hologram recording material is used as a recording material for the bulk layer 102. As a hologram recording material, for example, a photopolymerization type photopolymer or the like is widely known.

The micro hologram method is roughly classified into a positive micro hologram method and a negative micro hologram method.
The positive micro-hologram method is a method in which two opposing light beams are condensed at the same position to form fine interference fringes (holograms), which are used as recording marks.
The negative type micro-hologram method is a method opposite to the positive type micro-hologram method, in which interference fringes formed in advance are erased by laser light irradiation, and the erased portion is used as a recording mark. In this negative microhologram method, a process of forming interference fringes in the bulk layer in advance is required as an initialization process.

The present applicant has also proposed a recording method for forming voids (vacancy, holes) as recording marks as disclosed in Patent Document 2, for example, as a bulk recording method different from the micro-hologram method. .
This void recording method is a technique in which, for example, a bulk layer 102 made of a recording material such as a photopolymerization type photopolymer is irradiated with laser light at a relatively high power, and an empty package is recorded in the bulk layer 102. It is. As described in Patent Document 2, the vacant portion formed in this way is a portion having a refractive index different from that of the other portion in the bulk layer 102, and the light reflectance is increased at the boundary portion. become. Therefore, the empty packet portion functions as a recording mark, thereby realizing information recording by forming an empty packet mark.

Since such a void recording method does not form a hologram, it is only necessary to perform light irradiation from one side for recording. That is, there is no need to form the recording mark by condensing the two light beams at the same position as in the case of the positive microhologram method described above.
Further, in comparison with the negative type micro hologram method, there is an advantage that the initialization process can be made unnecessary.
Note that Patent Document 1 shows an example in which pre-cure light irradiation is performed before performing void recording, but void recording is possible even if such pre-cure light irradiation is omitted.

  Here, when the void recording method is employed, the recording signal is read (reproduced) by detecting the difference in reflectance between the void formed portion and the non-formed portion. Specifically, the void formed portion has a high reflectance, and the void non-formed portion has a low reflectance (zero), and a reproduction signal is obtained based on the result of detecting the difference in reflectance on the detector. .

  In the void recording method in which signal reproduction is performed by detecting such a difference in reflectance, it is effective to increase the void size in order to increase the reproduction signal level (contrast between the mark formation part and the non-formation part). It is. That is, the reflectance is increased by increasing the void size.

However, on the other hand, in consideration of performing recording of, for example, about a dozen layers or several tens of layers as multilayer recording, it is necessary to consider crosstalk in the depth direction.
FIG. 18 is an explanatory diagram of crosstalk in the depth direction.
As shown in the figure, when reproduction is performed by focusing on a void at a certain recording position (recording position in the layer direction; hereinafter also referred to as a layer position), reflected light from voids at other layer positions is detected by the detector. By leaking upward, the S / N is deteriorated. In order to prevent such crosstalk in the depth direction, it is desirable that the void reflectivity at each recording position is small, and the void size should be small.

As can be seen from the above two points, in the void recording method, if the void size is increased with the intention of increasing the signal level, the crosstalk in the depth direction increases, and the S / N deteriorates. On the contrary, if the void size is reduced and crosstalk is to be suppressed, the signal level is lowered and the S / N is deteriorated.
That is, in the void recording method, increasing the signal level and suppressing crosstalk in the depth direction have a trade-off relationship.

As a result, it is very difficult to adjust to an appropriate S / N in the void recording method in which signal reproduction is performed by detecting the difference in reflectance.
Further, when the void size is increased, the void transmittance decreases accordingly, and there is a problem that signal reproduction becomes more disadvantageous at the lower recording position. This also makes it difficult to adjust to an appropriate S / N.

  As another problem, since the void recording method forms a hole mark as a recording mark, a very high laser power is required to form the mark. Specifically, in order to form a hole mark, it is necessary to concentrate a very high power in a short time. Therefore, a light source for a recording laser requires a relatively large light source capable of realizing a high output. There is also a problem.

The present technology has been made to solve the above problems.
The recording apparatus according to an embodiment of the present technology condenses laser light as appropriate in the vicinity of the interface in an optical recording medium having a structure in which a plurality of interfaces between the first layer and the second layer are formed. In the vicinity, a recording mark that does not lead to the formation of an empty envelope mark, which is accompanied by modulation of the refractive index and / or shape change of the interface is formed.

  In addition, the optical recording medium of the present technology has a structure in which a plurality of interfaces between the first layer and the second layer are formed, and a blank mark is formed in the vicinity of each of the interfaces. Is a recording mark that does not lead to the formation of a recording mark with refractive index modulation and / or shape change of the interface.

Here, according to said structure, the said interface can be functioned as a reflective surface by varying the refractive index of a said 1st layer and a said 2nd layer. As described above, if a recording mark is formed by refractive index modulation or interface deformation as described above in the vicinity of each interface that functions as a reflective surface, the reflected light generated at the mark forming portion and other portions is reflected. By using the optical path length difference (phase difference), it is possible to determine the presence / absence of mark formation (reproduction of a recorded signal). That is, signal reproduction by so-called phase difference detection becomes possible.
In the case of phase difference detection, in order to improve the reproduction signal level, the phase difference (optical path length difference) of reflected light between the mark forming part and the non-forming part may be set appropriately. It is not necessary to increase the reflectance of the portion or increase the mark size. In other words, this makes it possible to avoid the trade-off relationship between the improvement of the reproduction signal level and the suppression of the crosstalk in the depth direction, and the adjustment to the appropriate S / N can be achieved with the conventional void recording method. It can be easier than the case.
Further, as described above, it is not necessary to increase the mark reflectivity (the same reflectivity due to the difference in refractive index between the first layer and the second layer) and the mark size in order to improve the reproduction signal level. A situation in which the amount of transmitted light on the lower layer side of the multi-layer recording is reduced in exchange for the improvement of the reproduction signal level as in the case of the system can be effectively avoided. That is, also in this point, adjustment to an appropriate S / N can be made easier.
Further, according to the present technology, the recording laser power may be at least power that promotes deformation or alteration (refractive index modulation) in the vicinity of the interface, and does not require high power to form a void mark. It is. Therefore, the recording laser light source can be made smaller than in the case of void recording. As a result, the apparatus can be reduced in size and the power consumption can be reduced.

According to the present technology, in order to increase the recording capacity by multilayer recording, it is possible to facilitate adjustment to an appropriate S / N as compared with a case where a conventional void recording method is adopted.
In addition, by reducing the recording laser power, the light source can be reduced, the apparatus size can be reduced, and the power consumption can be reduced.

  In addition, since the recording is performed on the interface, as compared with the case of recording one recording layer per recording layer as in the current multilayer recording medium, the repetitive stacking required for realizing the same recording capacity is performed. The number of times can be reduced to half.

1 is a cross-sectional structure diagram of an optical recording medium as a first embodiment. It is a figure for demonstrating the servo control technique about the optical recording medium of embodiment. It is the figure which illustrated mainly the internal structure of the optical system with which the recording device of embodiment is provided. It is the figure which illustrated the internal structure of the recording device of embodiment. It is a figure for demonstrating the recording / reproducing principle of the optical recording medium of 1st Embodiment. FIG. 5 is a cross-sectional structure diagram of an optical recording medium as a second embodiment. It is a figure for demonstrating the recording / reproducing principle of the optical recording medium of 2nd Embodiment. It is a cross-section figure of the optical recording medium as 3rd Embodiment. It is a figure for demonstrating the recording / reproducing principle of the optical recording medium of 3rd Embodiment. It is a cross-section figure of the optical recording medium as 4th Embodiment. It is a figure for demonstrating the recording / reproducing principle of the optical recording medium of 4th Embodiment. FIG. 10 is a cross-sectional structure diagram of an optical recording medium as a fifth embodiment. It is a figure for demonstrating the recording and reproducing principle of the optical recording medium of 5th Embodiment. It is sectional drawing of the optical recording medium as 6th Embodiment. It is a figure for demonstrating the recording and reproducing principle of the optical recording medium of 6th Embodiment. It is a figure for demonstrating the optical recording medium as a modification. It is a figure for demonstrating a bulk recording system. It is a figure for demonstrating the crosstalk of a depth direction.

Hereinafter, embodiments according to the present technology will be described.
The description will be given in the following order.

<1. First Embodiment>
[1-1. Optical Recording Medium of First Embodiment]
[1-2. Servo control]
[1-3. Configuration of recording device]
[1-4. Specific recording medium configuration and recording / reproducing principle]
[1-5. effect]
<2. Second Embodiment>
<3. Third Embodiment>
<4. Fourth Embodiment>
<5. Fifth embodiment>
<6. Sixth Embodiment>
<7. Modification>

<1. First Embodiment>
[1-1. Optical Recording Medium of First Embodiment]

FIG. 1 shows a cross-sectional structure diagram of an optical recording medium 1 as a first embodiment.
First, as a premise, the optical recording medium 1 of the present embodiment is a disc-shaped optical recording medium, and laser recording is performed on the optical recording medium 1 that is rotationally driven to perform mark recording (information recording). Also, the reproduction of the recorded information is performed by irradiating the optical recording medium 1 that is rotationally driven with a laser beam.

As shown in FIG. 1, in the optical recording medium 1 of the present embodiment, a cover layer 2 and a selective reflection film 3 are formed in order from the upper layer side, and an intermediate layer 4 and a recording layer are formed on the lower layer side thereof. 5 and 5 are alternately and repeatedly stacked.
Here, the “upper layer side” in this specification refers to the upper layer side when the surface on which a laser beam from the recording apparatus side described later is incident is the upper surface.
Note that the intermediate layer 4 formed at the bottom functions as a cover layer (protective layer).

The number of repeated laminations of the intermediate layer 4 and the recording layer 5 is x (x is a natural number of 2 or more).
Here, the repeated stacking number x is counted as one when returning to the stacking of the same layer. That is, x = 1 in the laminate of “intermediate layer 4 / recording layer 5 / intermediate layer 4”.
The number of repeated stacking may be set to x ≧ 2 if recording for at least three layers or more is performed as multilayer recording. In this example, it is assumed that, for example, x = about 10-15.

The intermediate layer 4 and the recording layer 5 have different refractive indexes. In other words, the optical recording medium 1 in this case has a structure in which first layers and second layers having different refractive indexes are alternately and repeatedly stacked. It has a structure in which a plurality of interfaces of the second layer are formed.
In such a structure, the interface between the intermediate layer 4 and the recording layer 5, that is, the upper surface and the lower surface of the recording layer 5 are caused to function as reflecting surfaces due to the difference in refractive index.

The specific refractive index may be, for example, the intermediate layer 4 = 1.45, the recording layer 5 = 1.65, or the like.
The reflectivity at the interface between the recording layer 5 and the intermediate layer 4 is set to about 0.5%, for example, and the transmittance at the interface is set to about 96% or more, for example.
Specific materials for the intermediate layer 4 and the recording layer 5 will be described later.

In the present embodiment, recording laser light is focused on the upper and lower surfaces of the recording layer 5 (that is, the interface between the recording layer 5 and the intermediate layer 4), and a recording mark is formed on the interface. It is one feature.
If such interface recording is performed, for example, as described above, if the number of repeated layers x is about 10 to 15, the number of interfaces that can be recorded can be doubled to about 20 to 30.
As can be understood from this, according to the present embodiment in which interface recording is performed, in order to realize the same number of recording layers (and hence recording capacity), a conventional multi-layer recording of one mark per recording layer is performed. Compared to the optical recording medium, the number of intermediate layers / recording layers to be formed on the recording medium can be reduced to half.

  Here, considering that the recording is performed on the interface of each recording layer 5 as described above, in the optical recording medium 1, the recording layer located at the bottom layer from the top surface of the recording layer 5 located at the top portion. The area up to the lower surface of 5 can be regarded as an area where mark recording is possible. Hereinafter, the area in the depth direction in which the optical recording medium 1 can perform mark recording is referred to as a recordable area 7.

The cover layer 2 is made of, for example, a resin such as polycarbonate or acrylic, and a position guide for guiding the recording / reproducing position is formed on the lower surface side thereof. In the case of this example, the position guide is formed by a groove (continuous groove) or a pit row. That is, a position guide as a guide groove is formed. For this reason, on the lower surface side of the cover layer 2, an uneven cross-sectional shape accompanying the formation of such guide grooves is given.
For example, when the guide groove is a groove, position information (address information) can be recorded based on the meandering period information by forming the groove meandering periodically. When the guide groove is a pit row, the position information can be recorded by modulating the pit length.
The cover layer 2 is generated by injection molding using a stamper in which such guide grooves (uneven shape) are formed.

A selective reflection film 3 is formed on the lower surface side of the cover layer 2.
Here, although not particularly mentioned in FIG. 17, in the conventional bulk recording method, when mark recording is performed on the bulk layer as the recording layer, the guide groove is the same as in the optical recording medium 1 shown in FIG. A reference surface Ref on which is formed is provided.
Conventionally, when performing mark recording on a bulk layer, the bulk layer is irradiated with recording light (recording laser light), and tracking and focus error signals are obtained based on the guide grooves as described above. The servo light (servo laser light) is separately irradiated on the guide groove.

At this time, if the reflective film to be formed on the reference surface Ref is a normal reflective film (a reflective film having no wavelength selectivity), the recording laser light is reflected by the reflective film, and the recording power is reduced. Attenuation occurs. For this reason, the recording light and the servo light have different wavelengths, and the selective reflection film 3 is provided. That is, the selective reflection film 3 is provided with a reflection film having wavelength selectivity that reflects light in the same wavelength band as the servo light and transmits light having other wavelengths.

[1-2. Servo control]

FIG. 2 is a diagram for explaining a servo control method for the optical recording medium 1.
As described above, the optical recording medium 1 is irradiated with a laser beam (servo laser beam) having a wavelength band different from the laser beam (recording laser beam) for forming a recording mark. It is supposed to be.
As will be described later, the recording laser beam and the servo laser beam are applied to the optical recording medium 1 through a common objective lens.

In the case of this example, the optical recording medium 1 is also irradiated with servo / playback laser light.
Here, the servo / playback laser beam is a laser beam irradiated to control the focus position of the recording laser beam at the time of recording, and to control the playback position at the time of playback and to obtain the mark reflected light, A laser beam having the same wavelength as the recording laser beam is used.
In the case of this example, a so-called pulse laser is used as the light source of the recording laser light. Since the pulse laser is a laser that obtains high power in a very short time such as picoseconds, it is difficult to use it for the purpose of obtaining reflected light for servo and reproduction light for recording marks. For this reason, in this example, a light source for servo and reproduction is provided separately from the recording light source as the pulse laser, and the optical recording medium uses the laser light from the light source as the servo / reproduction laser light. 1 is irradiated.
This servo / reproducing laser beam is also irradiated onto the optical recording medium 1 through the objective lens.

Here, in the optical recording medium 1, a position guide such as a pit or a groove is not formed at the interface that is a mark recording target position. For this reason, tracking servo using servo / playback laser light cannot be performed at the time of recording in which a mark is not yet formed.
From this point, tracking servo at the time of recording is performed using servo laser light. That is, a tracking error signal based on the reflected light of the servo laser beam focused (focused) on the selective reflection film 3 is generated, and the position control of the objective lens in the tracking direction is performed based on the tracking error signal. As a result, the spot position of the recording laser light irradiated through the same objective lens can be controlled to an appropriate position in conjunction with the spot position of the servo laser light.

On the other hand, during recording, focus servo is performed using servo / playback laser light.
That is, there is a difference in the detection intensity of the reflected light of the servo / reproducing laser beam between the state where the servo / reproducing laser beam is focused on the interface and the other state. -Focus servo control using reflected light of the reproduction laser beam is performed.

  Further, during reproduction of the optical recording medium 1 on which mark recording has already been performed, tracking servo can be performed using reflected light of servo / reproducing laser light. From this point, servo control during reproduction is performed using reflected light of servo / reproducing laser light for both tracking servo and focus servo.

Here, it should be noted that the focus servo control requires that the focus position of the servo / playback laser beam and the focus position of the servo laser beam have to be different from each other. That is, as can be understood with reference to FIG. 2, as the servo laser light, the in-focus position is the reference position so that the tracking error signal is properly generated based on the reference surface Ref on which the position guide is formed. On the other hand, the servo / reproducing laser beam (recording laser beam) should have the in-focus position corresponding to the interface to be recorded.
In consideration of such points, the control of the focus direction must be performed independently for the servo / reproducing laser beam and the servo laser beam.

  In the case of this example, the focus control of the servo laser beam is performed by controlling the common objective lens, and the focus control of the servo / playback laser beam and the recording laser beam is separately performed on the servo / reproducing laser beam. A mechanism for independently controlling the in-focus positions of the reproducing laser beam and the recording laser beam is provided, and the mechanism is driven (see the lens driving unit 19 in FIG. 3). Hereinafter, such a focus control mechanism is referred to as a “recording / reproducing light focus mechanism”.

In summary, the servo control in this example is performed as follows.

・ Servo / reproducing laser beam (and recording laser beam) During recording: Focus servo is performed by driving the recording / playback focusing mechanism using the reflected light of the servo / reproducing laser beam (About tracking servo) Is automatically performed by driving the objective lens using the reflected light of the servo laser light)
During reproduction: Both focus servo and tracking servo are performed by driving the objective lens using the reflected light of the servo / reproducing laser beam.

• Servo laser beam side During recording: Focus servo is performed by driving the objective lens using the reflected laser beam, and tracking servo is driven using the servo laser beam reflected. Do it.
During reproduction: During the recording mark reproduction, servo control based on the servo laser beam can be dispensed with.

However, it is necessary to read out the position information recorded on the reference plane Ref when seeking to start reproduction or recording. In this case, focus servo and tracking servo of the servo laser light are performed by controlling the objective lens based on the reflected light of the servo laser light.

[1-3. Configuration of recording device]

FIG. 3 mainly shows an internal configuration example of the optical system provided in the recording apparatus 10 as the embodiment. Specifically, the internal configuration of the optical pickup OP provided in the recording apparatus 10 is mainly shown.

In FIG. 3, the optical recording medium 1 loaded in the recording apparatus 10 is set so that its center hole is clamped at a predetermined position in the recording apparatus 10, and can be rotated by a spindle motor (not shown). Retained.
The optical pickup OP is provided to irradiate the optical recording medium 1 rotated by the spindle motor with a recording laser beam, a servo / playback laser beam, and a servo laser beam.

In the optical pickup OP, a recording laser 11 which is a light source of a recording laser beam for recording information by a mark, and a servo / reproduction for reproducing information recorded by the mark and controlling a recording / reproducing position. And a servo / reproducing laser 14 which is a light source of the laser light for use.
In addition, a servo laser 27 that is a light source of servo laser light that is light for performing position control using a position guide formed on the reference surface Ref is provided.
Here, as described above, the recording laser beam and the servo / reproducing laser beam are laser beams having the same wavelength, and the servo laser beam is different in wavelength band from these laser beams. In the case of this example, the wavelength of the recording laser beam and the servo / reproducing laser beam is about 405 nm (so-called blue-violet laser beam), and the wavelength of the servo laser beam is about 650 nm (red laser beam). To do.

In the optical pickup OP, an objective lens 23 serving as an output end of the recording laser beam, the servo / playback laser beam, and the servo laser beam to the optical recording medium 1 is provided.
In addition, a servo / reproducing light receiving unit 26 for receiving reflected light of the servo / reproducing laser beam from the optical recording medium 1 is provided in the optical pickup OP.
In the optical pickup OP, the recording laser beam emitted from the recording laser 11 and the servo / reproducing laser beam emitted from the servo / reproducing laser 14 are guided to the objective lens 23, and the objective lens 23. An optical system for guiding the reflected light of the servo / reproducing laser beam from the optical recording medium 1 incident on the servo / reproducing light receiving unit 26 is formed.

In such an optical system for recording laser light and servo / reproducing laser light, the recording laser light emitted from the recording laser 11 is converted into parallel light through the collimation lens 12, Incident on the half mirror 13.
Further, the servo / reproducing laser beam emitted from the servo / reproducing laser 14 is made to be parallel light through the collimation lens 15 and then enters the half mirror 13 in the same manner.
The half mirror 13 causes the recording laser light incident from the recording laser 11 side and the servo / reproducing laser light incident from the servo / reproducing laser 14 side to coincide with each other as described above. Output.

  The recording laser light and servo / reproducing laser light output from the half mirror 13 enter the polarization beam splitter 16. The polarization beam splitter 16 is configured to transmit the recording laser light and servo / reproducing laser light incident in this way.

The recording laser light and servo / reproducing laser light transmitted through the polarization beam splitter 16 are incident on a recording / reproducing light focusing mechanism including a fixed lens 17, a movable lens 18, and a lens driving unit 19. In this recording / playback light focusing mechanism, the side closer to the light source (recording laser 11, servo / playback laser 14) is the fixed lens 17, and the movable lens 18 is disposed on the side farther from the light source. When the movable lens 18 is driven in a direction parallel to the optical axis, independent focus control is performed on the recording laser beam and the servo / reproducing laser beam.
As can be understood from the above description, the lens driving unit 19 in the recording / reproducing light focus mechanism is driven based on the reflected light of the servo / reproducing laser light, and the recording laser light and the servo / reproducing light are used. It is responsible for focus servo control for laser light.

The recording laser light and servo / reproducing laser light through the fixed lens 17 and the movable lens 18 in the upper recording / relighting focus mechanism are reflected by the mirror 20 as shown in the figure, and then the quarter-wave plate 21. Then, the light enters the dichroic prism 22.
The selective reflection surface of the dichroic prism 22 is configured to reflect light in the same wavelength band as that of the recording laser light and servo / playback laser light, and transmit light having other wavelengths. Accordingly, the recording laser beam and servo / reproducing laser beam incident as described above are reflected by the dichroic prism 22.

The recording laser light reflected by the dichroic prism 22 is applied to the optical recording medium 1 through the objective lens 23 as shown in the figure.
With respect to the objective lens 23, the objective lens 23 is moved in the focus direction (the direction in which the objective lens 23 is moved toward and away from the optical recording medium 1) and the tracking direction (the direction orthogonal to the focus direction: parallel to the radial direction of the optical recording medium 1). A biaxial actuator 24 that is displaceably held in a desired direction).
The biaxial actuator 24 is provided with a focus coil and a tracking coil, and a drive signal (a drive signal FD-sv, TD-sv, or TD-sp, which will be described later) is given to each of the two-axis actuators 24, so Displace each in the tracking direction.

Here, when the servo / reproducing laser beam is irradiated onto the optical recording medium 1 as described above, reflected light is obtained from the optical recording medium 1 (interface to be reproduced). The reflected light of the servo / reproducing laser beam thus obtained is guided to the dichroic prism 22 through the objective lens 23 and reflected by the dichroic prism 22.
The reflected light of the servo / reproducing laser beam reflected by the dichroic prism 22 passes through the quarter-wave plate 21 → mirror 20 → recording / reproducing light focus mechanism (movable lens 18 → fixed lens 17), and then is a polarized beam. The light enters the splitter 16.

  Thus, the reflected light (return light) of the servo / playback laser light incident on the polarization beam splitter 16 is generated from the light source side by the action of the quarter-wave plate 21 and the action at the time of reflection on the optical recording medium 1. The direction of polarization is different from that of forward light incident on the polarization beam splitter 16 by 90 degrees. As a result, the reflected light of the servo / reproducing laser beam incident as described above is reflected by the polarization beam splitter 16.

  The reflected light of the servo / reproducing laser beam reflected by the polarization beam splitter 16 is condensed on the light receiving surface of the servo / reproducing light receiving unit 26 via the condenser lens 25. The light receiving signal obtained by the servo / reproducing light receiving unit 26 receiving the servo / reproducing laser light is expressed as a light receiving signal DT-sp as shown in the figure.

Further, in the optical pickup OP, in addition to the configuration of the optical system for the recording laser beam and the servo / reproducing laser beam described above, the servo laser beam emitted from the servo laser 27 is supplied to the objective lens 23. And an optical system for guiding the reflected light of the servo laser light from the optical recording medium 1 incident on the objective lens 23 to the light receiving portion 32 for servo light is formed.
As shown in the figure, the servo laser light emitted from the servo laser 27 is converted into parallel light through the collimation lens 28 and then enters the polarization beam splitter 29. The polarization beam splitter 29 is configured to transmit the servo laser light (outgoing light) incident from the servo laser 27 side in this way.

The servo laser light transmitted through the polarization beam splitter 29 is incident on the dichroic prism 22 via the quarter wavelength plate 30.
As described above, the dichroic prism 22 is configured to reflect light in the same wavelength band as that of the recording laser light and servo / playback laser light and transmit light of other wavelengths. The servo laser light passes through the dichroic prism 22 and is applied to the optical recording medium 1 through the objective lens 23.

In this way, in response to the servo laser light being irradiated onto the optical recording medium 1, reflected light of the servo laser light is obtained from the optical recording medium 1 (reference surface Ref). The reflected light of the servo laser light passes through the objective lens 23 and then passes through the dichroic prism 22 and enters the polarization beam splitter 29 via the quarter-wave plate 30.
As in the case of the previous servo / reproducing laser beam, the reflected light (return light) of the servo laser beam incident from the optical recording medium 1 side in this way is the action of the quarter wavelength plate 30 and the optical recording medium. Due to the action at the time of reflection at 1, the polarization direction of the forward light is 90 degrees different from that of the forward light, so that the reflected light of the servo laser light as the backward light is reflected by the polarization beam splitter 29.

  The reflected light of the servo laser beam reflected by the polarization beam splitter 29 is condensed on the light receiving surface of the servo light receiving unit 32 via the condenser lens 31. The light receiving signal obtained by the servo light receiving unit 32 receiving the reflected light of the servo laser light is represented as a light receiving signal DT-sv.

Next, an example of the overall internal configuration of the recording apparatus 10 will be described with reference to FIG.
4, the internal configuration of the optical pickup OP is shown by extracting only the recording laser 11, the servo / reproducing laser 14, the lens driving unit 19, and the biaxial actuator 24 from the configuration shown in FIG. ing.
Although not shown, in the recording apparatus 10, the entire optical pickup OP is slidable in the tracking direction by a slide mechanism. Control of the slide mechanism is performed by a servo / reproducing light servo circuit 40 or a servo light servo circuit 42 described later. More specifically, when tracking servo control of the objective lens 23 is executed by the servo light servo circuit 42 corresponding to the recording time, the servo light servo circuit 42 controls the servo lens 42 and the servo light corresponding to the reproduction time corresponds to the servo. When the tracking servo control of the objective lens 23 is executed by the reproducing light servo circuit 40, the servo / reproducing light servo circuit 40 controls the objective lens 23.

  In FIG. 4, the recording apparatus 10 includes an objective based on recording / reproduction for the recordable area 7 in the optical recording medium 1 and reflected light from an interface (and a recording mark) formed in the recordable area 7. As a configuration for performing focus / tracking control of the lens 23, a light emission drive unit 35, a recording processing unit 36, a light emission drive unit 37, a servo / reproduction light matrix circuit 38, a reproduction processing unit 39, and a servo / reproduction light servo. A circuit 40 is provided.

  Based on an instruction from the controller 43, the light emission drive unit 35 drives the servo / reproducing laser 14 to emit light by a laser drive signal D-sp.

The recording processing unit 36 generates a recording modulation code corresponding to the input recording data. Specifically, the recording processing unit 36 actually records on the optical recording medium 1 by adding an error correction code to the input recording data or performing a predetermined recording modulation encoding process, for example, “0”. A recording modulation code string that is a binary data string of “1” is obtained.
The recording processing unit 36 gives a recording signal based on the recording modulation code string generated in this way to the light emission driving unit 37.

The light emission drive unit 37 generates a laser drive signal Dr based on the recording signal input from the recording processing unit 36, and drives the recording laser 11 to emit light based on the drive signal Dr.
The light emission drive unit 37 also adjusts the laser power based on an instruction from the controller 43.

The servo / reproducing light matrix circuit 38 corresponds to the light reception signal DT-sp (output current) from the plurality of light receiving elements as the servo / reproducing light receiving unit 26 shown in FIG. An arithmetic / amplification circuit and the like are provided, and necessary signals are generated by matrix arithmetic processing.
Specifically, a high frequency signal (hereinafter referred to as a reproduction signal RF) corresponding to a reproduction signal obtained by reproducing the above-described recording modulation code string is generated.
Further, as a signal for performing tracking servo control, a tracking error signal TE-sp is generated that represents a deviation amount (tracking error) in the radial direction of the irradiation spot of the servo / playback laser beam with respect to the track as the recording mark row. Further, as a signal for performing the focus servo control, a focus error signal FE-sp representing a focus error of the servo / reproducing laser beam with respect to the target interface is generated.

The reproduction signal RF generated by the servo / reproduction light matrix circuit 38 is supplied to the reproduction processing unit 39.
The focus error signal FE-sp and the tracking error signal TE-sp are supplied to the servo / reproducing light servo circuit 40.

  The reproduction processing unit 39 performs reproduction processing for restoring the above-described recording data such as binarization processing, recording modulation code decoding / error correction processing on the reproduction signal RF, and reproduction data obtained by reproducing the recording data Get.

The servo / reproducing light servo circuit 40 includes a focus servo signal FS-sp and a tracking servo signal TS-sp based on the focus error signal FE-sp and tracking error signal TE-sp supplied from the servo / reproducing light matrix circuit 38. Are generated respectively.
Based on the focus servo signal FS-sp and the tracking servo signal TS-sp, the focus drive signal FD-sp and the tracking drive signal TD-sp for driving the focus coil and tracking coil of the biaxial actuator 24 are generated. To do.
In the case of this example, the focus drive signal FD-sp is supplied to the lens drive unit 19 as shown.
The tracking drive signal TD-sp is supplied to the switch SW.

The servo / reproducing light servo circuit 40 turns off the tracking servo loop based on an instruction from the controller 43 and applies a jump pulse to the tracking coil of the biaxial actuator 24 via the switch SW. A track jump operation for the laser beam is executed.
Also, based on an instruction from the controller 43, a focus servo pull-in process for the servo / playback laser beam targeting the interface of the predetermined recording layer 5 and a focus jump operation for the servo / playback laser beam are executed. Let

  Further, the recording apparatus 10 is provided with a servo light matrix circuit 41 and a servo light servo circuit 42 as a signal processing system for the reflected light of the servo laser light.

The servo light matrix circuit 41 corresponds to a light reception signal DT-sv (output current) from a plurality of light receiving elements as the servo light receiving unit 32 shown in FIG. Etc., and necessary signals are generated by matrix calculation processing.
Specifically, as a signal for performing tracking servo control, a tracking error indicating a deviation amount (tracking error) in the radial direction of the irradiation spot of the servo laser beam with respect to the position guide (track) formed on the reference surface Ref. A signal TE-sv is generated. Further, a focus error signal FE-sv representing a focus error of servo laser light with respect to the reference surface Ref (selective reflection film 3) is generated as a signal for performing the focus servo control.
These focus error signal FE-sv and tracking error signal TE-sv are supplied to the servo circuit 42 for servo light.

The servo light servo circuit 42 generates a focus servo signal FS-sv and a tracking servo signal TS-sv based on the focus error signal FE-sv and the tracking error signal TE-sv, respectively.
Based on the focus servo signal FS-sv and the tracking servo signal TS-sv, a focus drive signal FD-sv and a tracking drive signal TD-sv for driving the focus coil and tracking coil of the biaxial actuator 24 are generated. To do.
In the case of this example, the focus drive signal FD-sv is supplied to the biaxial actuator 24 (focus coil).
On the other hand, the tracking drive signal TD-sv is supplied to the switch SW.

  In addition, the servo light servo circuit 42 turns off the tracking servo loop based on an instruction from the controller 43 and applies a jump pulse to the tracking coil of the biaxial actuator 24 via the switch SW. A track jump operation is executed, and based on an instruction from the controller 43, a focus servo pull-in process for the servo laser light for the reference surface Ref is performed.

  Based on an instruction from the controller 43, the switch SW selectively outputs one of the tracking drive signal TD-sp and the tracking drive signal TD-sp to the biaxial actuator 24 (tracking coil). That is, it is possible to switch between tracking servo control based on the reflected light of the servo / reproducing laser beam and tracking servo control based on the reflected light of the servo laser.

The controller 43 is configured by a microcomputer including a memory (storage device) such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), for example, a program stored in the ROM or the like, for example. The overall control of the recording apparatus 10 is performed by executing control and processing according to the above.
For example, the controller 43 realizes switching of the servo control corresponding to each of the above-described recording / reproducing by giving instructions to the servo / reproducing light servo circuit 40, the servo light servo circuit 42, and the switch SW. . Specifically, at the time of recording, after generating the tracking drive signal TD-sv by the servo light servo circuit 42, the tracking drive signal TD-sv is selected by the switch SW, so that the servo drive circuit TD-sv is selected. Tracking servo control of the objective lens 23 based on the reflected light of the laser light (that is, tracking servo control based on the track of the reference surface Ref) is performed.
Also, at the time of reproduction, after the tracking drive signal TD-sp is generated by the servo / reproduction light servo circuit 40, the tracking drive signal TD-sp is selected by the switch SW. Tracking servo control of the objective lens 23 based on the reflected light of the reproduction laser beam (that is, tracking servo control based on the recording mark row) is executed.
As described above, at the time of seeking, the former control, that is, the tracking servo control of the objective lens 23 based on the reflected light of the servo laser light is executed so that the position information of the reference surface can be read. .

Further, the controller 43 instructs the servo / reproduction light servo circuit 40 of the interface to be recorded / reproduced, and executes a focus servo pull-in process for the servo / reproduction laser light targeting the interface. . That is, the selection control of the interface to be recorded / reproduced is performed.

[1-4. Specific recording medium configuration and recording / reproducing principle]

Here, in the optical recording medium 1 of the first embodiment, the recording layer 5 and the intermediate layer 4 are specifically those having the following properties.
In other words, the recording layer 5 has a property of causing expansion (thermal expansion) in the vicinity of the condensing point in response to irradiation (condensing) of the recording laser beam. Further, as the intermediate layer 4, a material having a lower Young's modulus than the recording layer 5 is used.

As a specific material of the recording layer 5 having the above properties, for example, a material mainly composed of a resin can be cited.
To give a more specific example,

1) Thermosetting resin (epoxy resin, etc.) + non-linear photosensitizing additive 2) Thermosetting resin having a non-linear photo-sensitive structure in the skeleton 3) Thermoplastic resin (polycarbonate, etc.) + Non-linear photo-sensitive additive 4) Among thermoplastic resins, those having a non-linear light-sensitive structure in the skeleton Example 1) Multiphoton absorbing material such as amorphous polyarylate resin as described in the following Reference 1 Example 2) described in the following Reference 2 2 photon absorbing material mainly composed of such resin 5) In the above 1) to 4), containing an acid generator additive material

Is mentioned.

-Reference 1 ... JP 2010-162846-Reference 2-JP 2009-274225

Regarding 2) above, HP-4032D represented by [Chemical Formula 1] is an example of the thermosetting resin, and 4-Ethynyl PA (Phthalic) represented by [Chemical Formula 2] is an example of the nonlinear photosensitive additive. Anhydride: phthalic anhydride).

When the above-listed materials are used as the recording layer 5, deformation that occurs in the vicinity of the condensing point of the laser light is caused by temperature rise due to nonlinear light absorption.
The above-mentioned material listings 1) to 5) are intended for various combinations that produce an effect by nonlinear light absorption (particularly, an effect that a mark having a smaller size than a recording beam spot can be formed).

  Moreover, as a specific material of the intermediate | middle layer 4, a thermoplastic resin can be mentioned, for example. More specifically, for example, a polycarbonate resin can be mentioned.

FIG. 5 is a diagram for explaining the recording / reproducing principle of the optical recording medium 1 as the first embodiment having the laminated structure of the recording layer 5 and the intermediate layer 4 as described above.
5A is a cross-sectional view showing a part of the layer structure in the recordable area 7 of the optical recording medium 1, and FIG. 5B is a recording mark formed on the upper surface side of the recording layer 5. FIG. 5C is an enlarged view of a recording mark formed on the lower surface side of the recording layer 5.

  As described above, in the present embodiment, the recording layer 5 expands near the condensing point of the laser beam, and the intermediate layer 4 has a lower Young's modulus than the recording layer 5. In other words, when the recording laser beam is appropriately condensed and irradiated on the interface), the laser beam irradiated portions on the upper surface and the lower surface of the recording layer 5 are convex toward the outside of the recording layer 5. Due to deformation. Such a convex surface deformation portion functions as a recording mark.

Here, as described above, since the refractive index of the intermediate layer 4 and the recording layer 5 are different from each other, their interface functions as a reflecting surface. For this reason, when the servo / playback laser beam is irradiated so as to be focused on the interface corresponding to the time of playback, in the portion where the convex deformation as described above occurs in the interface and the other portions, An optical path length difference (phase difference) occurs in the reflected light.
Due to the phase difference of the reflected light, on the detector (servo / reproducing light receiving unit 26), the level of the mark formation portion and the non-formation portion in the reproduction signal RF due to the interference of the light wave having the phase difference. There will be a difference. That is, as a result, it is possible to determine the mark formation part / non-formation part, and it is possible to determine the recording code “0” / “1”.

At this time, when the height of the convex mark as described above is ds, the refractive index of the intermediate layer 4 is n, and the refractive index of the recording layer 5 is N, the mark formation portion on the upper surface side of the recording layer 5 is not formed. As shown in FIG. 5B, the optical path length difference Do between the portions is also shown in FIG.

Do = n · ds × 2

It can be expressed as.
Further, the optical optical path length difference Do between the mark forming portion and the non-forming portion on the lower surface side of the recording layer 5 is as shown in FIG. 5C.

Do = N · ds × 2

It is expressed.

In the case of a BD-ROM (BD = Blu-ray Disc: registered trademark), the pit depth is about 50 nm, and the optical optical path length difference Do between the land and the pit is about 80 × 2 nm.
Considering this point, if the optical optical path length difference Do that can secure a sufficient reproduction signal level (contrast between the mark formation portion and the non-formation portion) is set to about 100 × 2 nm, n and N are each 1.2. Assuming that it is within a range of about 1.5 to 1.5, the required mark height ds can be estimated to be about 65 nm to 80 nm.

Here, in order to form a convex recording mark as described above, the power of the recording laser beam must not be too high. This is because if the power of the recording laser beam is excessive, a void mark is formed.
Therefore, the power of the recording laser beam in the present embodiment is set to a level that does not lead to the formation of the hole mark according to the characteristics of the recording layer 5.

  For confirmation, the hole mark means that one of the voids functions as one recording mark.

Further, the thickness of the recording layer 5 and the intermediate layer 4, that is, the distance in the depth direction between the marks, must be ensured to some extent in order to suppress crosstalk (and crosswrite) between adjacent interfaces. I must.
Specifically, the thickness of the recording layer 5 and the intermediate layer 4 is desirably at least 5 μm.
For the point that it is desirable to set the separation distance of each layer to 5 μm or more in order to suppress crosstalk between adjacent layers as described above, see Reference Document 3 below.

Reference 3 ... K. Saito and S. Kobayashi: “Analysis of Micro-Reflector 3-D optical disc recording” Proc. Of SPIE, Vol. 6282, 2007.

  The thickness of the intermediate layer 4 formed on the uppermost and lowermost portions is set in consideration of the above-described suppression of crosstalk in the sense that marks are recorded only on one side. Can be excluded from the target.

Further, when the recording mark is formed by the temperature rising deformation by nonlinear light absorption as described above, that is, when the recording layer 5 is deformed due to the heat generated by absorbing the light, the recording laser light is collected. In order to obtain better recording characteristics (reproduction characteristics), it is preferable that the light spot does not coincide with the interface and is offset to some extent from the interface in the recording layer 5.
In that case, the recording apparatus 10 may be configured such that a predetermined amount of offset is given to the focus servo loop based on the focus error signal FE-sp. As a specific configuration example, an adder is inserted in the line of the focus error signal FE-sp supplied to the servo / reproducing light servo circuit 40, and the adder adds a predetermined offset to the focus error signal FE-sp. What is necessary is just to add a value.

Further, it is desirable that the transmittance at the interface between the recording layer 5 and the intermediate layer 4 is large in order to prevent absorption and scattering by the recording mark.

[1-5. effect]

As described above, in the present embodiment, as a technique for realizing multi-layer recording / reproduction, a void mark is formed in a bulk-shaped recording layer (bulk layer 102) as in the conventional void recording method, and mark formation is performed. A method of detecting the difference in reflectance between the portion and the non-formed portion to perform signal reproduction is not adopted, and a structure having a plurality of interfaces between the first layer and the second layer having different refractive indexes (specifically, the first layer) 1 layer and the second layer are alternately and repeatedly stacked), and a deformation that does not lead to the formation of the empty mark is given to the interface between them to form a recording mark, so-called phase difference detection The signal reproduction by this is enabled.

Since the phase difference is detected, the phase difference (optical path length difference) of the reflected light between the mark formation portion and the non-formation portion may be set appropriately in order to improve the reproduction signal level. That is, it is ideal that the phase difference of the reflected light is a half wavelength of the reproduction light wavelength. In the case of phase difference detection, in order to improve the reproduction signal level, it is only necessary to optimize the occupied area of the mark formation portion and the non-formation portion in the reproduction light spot.
As described above, in the case of phase difference detection, it is not necessary to increase the reflectance of the mark portion or increase the mark size unlike the void recording method in improving the reproduction signal level. In other words, this makes it possible to avoid the trade-off relationship between the improvement of the reproduction signal level and the suppression of the crosstalk in the depth direction, and the adjustment to the appropriate S / N can be achieved with the conventional void recording method. It can be easier than the case.

  Further, as described above, it is not necessary to increase the mark reflectivity (the same reflectivity due to the difference in refractive index between the first layer and the second layer) and the mark size in order to improve the reproduction signal level. A situation in which the amount of transmitted light on the lower layer side of the multi-layer recording is reduced in exchange for improvement in the reproduction signal level as in the case of the system can be effectively avoided. That is, also in this point, adjustment to an appropriate S / N can be made easier.

  Further, it is not necessary to form up to the empty mark, and the power of the recording laser light may be at least as long as it promotes deformation of the interface. Therefore, the recording laser 11 can be made smaller than in the case of the void recording method. As a result, the recording apparatus 10 can be reduced in size, and power consumption can be reduced.

Further, according to the present embodiment in which interface recording is performed, an intermediate layer necessary for realizing the same recording capacity as compared with the case of performing recording for one recording layer per recording layer as in the current multilayer recording medium. / The number of repeated recording layers can be reduced to half.
According to this, the labor required for manufacturing the optical recording medium 1 can be reduced, and the manufacturing cost of the optical recording medium 1 can be reduced.

<2. Second Embodiment>

FIG. 6 is a cross-sectional structure diagram of an optical recording medium 45 as the second embodiment.
In the following description, parts that have already been described are assigned the same reference numerals and description thereof is omitted.
The optical recording medium 45 of the second embodiment is the same as the optical recording medium 1 of the first embodiment except that a recording layer 46 is provided instead of the recording layer 5.

The recording layer 46 has a property that a refractive index change occurs near the condensing point of the laser beam.
Specifically, the recording layer 46 in this case has a property that a refractive index change occurs due to the formation of “po” near the condensing point of the laser beam. Here, “po” refers to a state in which a large number of extremely small bubbles are formed.

  For confirmation, as described above, one hole mark forms one recording mark as described above, whereas “po” is a collection of extremely small bubbles (empty packets). It is a body, and one bubble is contained in a large number in one mark.

  As an example of a material in which such an aggregate of extremely small bubbles as “pode” is formed, the material of 5) exemplified in the first embodiment (a resin having nonlinear photosensitivity and an acid generator added) And those containing materials).

  As the intermediate layer 4, a layer having a Young's modulus lower than that of the recording layer 46 is used. Specific examples of the material include the same thermoplastic resins as those described in the first embodiment.

  The intermediate layer 4 and the recording layer 46 have different refractive indexes, and in this case also, their interface functions as a reflecting surface.

FIG. 7 is a diagram for explaining the recording / reproducing principle of the optical recording medium 45 according to the second embodiment.
7A is a cross-sectional view showing a part of the layer structure in the recordable area 7 of the optical recording medium 45, as in the case of FIG. 5, and FIG. 7C is an enlarged view of the recording mark formed on the lower surface side of the recording layer 46. FIG.

According to the optical recording medium 45 of the second embodiment described above, when recording operation is performed by appropriately condensing the recording laser beam on the upper and lower surfaces of the recording layer 46, these recording operations are performed. In the vicinity of the laser light irradiated portions on the upper and lower surfaces of the layer 46, a shape change that protrudes toward the outside of the recording layer 46 occurs due to thermal expansion, and in the vicinity of the condensing point of the laser light in the recording layer 46, A refractive index modulation portion as “pode” is formed.
That is, a convex deformation mark accompanied by “po” is formed.

In the case where the recording layer 46 is made of the material 5), when the laser beam with a certain power or more is condensed, the recording layer 46 is separated from the additive by a chemical reaction near the laser beam condensing point in the recording layer 46. A cation (acid) is generated, and gas is generated by inducing the decomposition of the surrounding molecular structure. Due to the generation of the gas, the “porosity” is formed.
At this time, if the base material is relatively hard, it is considered that the gas is moderately suppressed from becoming one large empty package, and an assembly of extremely small bubbles (that is, “po”) is formed. It is done. In this respect, the material 5) is suitable for forming a “pode”.

  In the case of using the material of 5), whether the mark is only a deformation of the interface as in the first embodiment or the deformation mark accompanied by “po” as in the second embodiment. Depending on the setting of the power of the recording laser beam. That is, the recording layer made of the above material 5) has a property that only deformation occurs in response to irradiation with a relatively low power laser beam and refractive index modulation occurs in response to irradiation with a higher power laser beam. In the case where the recording mark is configured to have the recording mark, the recording mark can be formed only by the deformation of the interface as in the first embodiment by performing the recording with the relatively low power recording laser beam. Further, if recording is performed with a higher-power recording laser beam, a deformation mark containing “po” as in the second embodiment can be formed.

For the deformation mark with the refractive index modulation portion as described above, the height of the convex deformation portion at the interface is ds, the refractive index of the intermediate layer 4 is n, the refractive index of the recording layer 46 is N, and the above-mentioned “po” When the height and refractive index of the refractive index modulation portion as the formation portion of the recording layer 46 are set to dm and N ′, respectively, the optical optical path length difference Do between the mark formation portion and the non-formation portion on the upper surface side of the recording layer 46 is As shown in FIG. 7B

Do = n · ds × 2

It can be expressed as.
Further, the optical optical path length difference Do between the mark forming portion and the non-forming portion on the lower surface side of the recording layer 46 is as shown in FIG. 7C.

Do = {(N′−N) · dm−N · ds} × 2

It is expressed.

  Here, the refractive index modulation portion by “po” is a portion where the refractive index is lower than the other portions in the recording layer 46. That is, the refractive index modulation portion by the “po” is composed of a set of extremely small bubbles (that is, the refractive index is approximately 1.0), and thus functions as a portion having a reduced refractive index as a whole.

  From this point, in the lower expression of the above two expressions, the relationship of N ′ <N is satisfied. That is, “(N′−N) · dm” is a negative value.

  Also in the second embodiment, the power of the recording laser light is set to a level that does not lead to the formation of the hole mark according to the characteristics of the recording layer 46.

  Also in the second embodiment, it is desirable that the thickness of the intermediate layer 4 and the recording layer 46 be at least 5 μm or more, as in the case of the first embodiment.

  Further, also in the second embodiment, when the recording mark is formed by the temperature rising deformation due to nonlinear light absorption, the condensing point of the recording laser beam is not made coincident with the interface, and the recording layer 46 side from the interface. A certain offset is preferable for obtaining good recording characteristics (reproduction characteristics).

In the above description, the case where “po” is formed as the refractive index modulation portion, that is, the case where the refractive index modulation portion showing a decrease in the refractive index is formed is exemplified. It may indicate an increase in rate. This is relatively easy to occur as a general deformation of the resin.
As an example of the material in which the refractive index increases near the laser beam condensing point, a material in which coloring occurs near the laser light condensing point can be given. Specific examples thereof include the materials 1) to 4) listed above.

As described above, the above lists 1) to 4) are mainly intended for various combinations that cause nonlinear light absorption.
Even when these materials 1) to 4) are used, as in the case of using the material 5) above, the recording layer only undergoes deformation in response to irradiation with a relatively low power laser beam. If it is configured so that refractive index modulation occurs in response to irradiation with a higher-power laser beam, the first embodiment is performed by performing recording with the relatively low-power recording laser beam. If the recording mark can be formed only by the deformation of the interface as in the embodiment, and the recording with the high-power recording laser beam is performed, the refractive index modulation portion and the interface deformation as in the second embodiment A recording mark with both can be formed.

<3. Third Embodiment>

FIG. 8 is a cross-sectional structure diagram of an optical recording medium 50 as the third embodiment.
The optical recording medium 50 of the third embodiment is different from the optical recording medium 45 of the second embodiment in that an intermediate layer 51 is provided instead of the intermediate layer 4.
In this case, the intermediate layer 51 has a higher Young's modulus than the recording layer 46.
As the recording layer 46, as in the second embodiment, a recording layer having a property in which a refractive index change occurs near the condensing point of the laser beam is used.
The intermediate layer 51 and the recording layer 46 have different refractive indexes, and in this case also, their interface functions as a reflecting surface.

FIG. 9 is a diagram for explaining the recording / reproducing principle of the optical recording medium 50 according to the third embodiment.
In this case, when the recording operation is performed by appropriately condensing the laser beam on the upper and lower surfaces of the recording layer 46, the upper and lower surfaces of the recording layer 46 are hardly deformed as shown in FIG. 9A. A refractive index modulation portion is formed in the vicinity of the upper surface and the lower surface in the recording layer 46 and in the vicinity of the condensing point of the laser beam.
In the present embodiment, since the Young's modulus of the intermediate layer 51 is high, the deformation of the interface of the recording layer 46 is suppressed, and the interface deformation can be suppressed to almost zero depending on the setting of the Young's modulus of the intermediate layer 51. In this case, since the same recording layer 46 as in the second embodiment is used, a refractive index modulation portion is formed near the condensing point of the laser light in the recording layer 46. .

  As described above, depending on the third embodiment, it is possible to form a refractive index modulation mark without surface deformation (nearly zero) on the upper and lower surfaces of the recording layer 46.

Here, FIG. 9B shows an enlarged view of the mark formed on the upper surface side of the recording layer 46. In the mark on the upper surface side, the lower edge surface of the mark indicated by R in the drawing is the reflecting surface. Will function as. That is, since the refractive index is different between the upper and lower sides of the edge surface R, the edge surface R functions as a reflecting surface.
In this case, the reflected light at the mark forming portion is guided to the detector by the component reflected by the reflecting surface as the upper surface of the recording layer 46 and the component reflected by the edge surface R. At this time, a phase difference corresponding to the mark height dm is generated between the reflected light from the mark non-formation portion on the upper surface of the recording layer 46 and the reflected light from the edge surface R. As can be understood from this, even in this case, a difference in detection intensity of reflected light, that is, a difference in level of the reproduction signal RF occurs between the mark forming portion and the non-forming portion, and the recording code can be determined. It becomes.

On the other hand, FIG. 9C shows an enlarged view of the mark formed on the lower surface side of the recording layer 46. As shown in the figure, for the mark on the lower surface side, the refractive index of the recording layer 46 is N, and the mark (refractive index If the height of the modulation portion) is dm and the refractive index of the mark is N ′, the optical optical path length difference Do between the mark forming portion and the non-forming portion on the lower surface side is

Do = (N′−N) · dm × 2

It can be expressed as.
On the lower surface side, the recording code can be determined based on the reflected light phase difference between the mark forming portion and the non-forming portion generated in this way.

In addition, since the edge surface of the mark (in this case, the upper edge surface) also functions as a reflection surface for such a mark portion on the lower surface side, strictly speaking, the mark forming portion and the non-forming portion on the lower surface side. Such a reflected light component from the edge surface also contributes to the reflected light detection intensity difference.
The fact that the reflected light from the edge surface of the refractive index modulation part contributes to the reflected light detection intensity difference between the mark formation part and the non-formation part in this way is the second embodiment (FIG. 7B, FIG. The same applies to the case of 7C).

Here, the material of the recording layer 46 in this case may be either a material that shows a decrease in refractive index due to the formation of “po” or a material that shows an increase in refractive index due to coloring or the like.
As can be understood from the above description, in any case, a detected intensity difference caused by the reflected light phase difference is obtained between the mark forming portion and the non-forming portion. That is, the recording code can be determined.

  Also in the third embodiment, the power of the recording laser light is set to a level that does not lead to the formation of the hole mark according to the characteristics of the recording layer.

Also in the third embodiment, the point that it is desirable that the thickness of the intermediate layer 51 and the recording layer 46 be at least 5 μm or more is the same as in the previous embodiments.

<4. Fourth Embodiment>

FIG. 10 is a cross-sectional structure diagram of an optical recording medium 55 according to the fourth embodiment.
In the optical recording medium 55 according to the fourth embodiment, an adhesive layer (intermediate layer) 56 is disposed below the selective reflection film 3, and a recording layer 57 serving as a recordable area 7 is provided below the adhesive layer 56. And a recording layer 46 are repeatedly formed (adhered).
In this case, the adhesive layer 56 can be made of a thermoplastic resin such as an ultraviolet curable resin.
In this case, the number of repeated laminations of the recording layer 57 and the recording layer 46 in the recordable area 7 is x times as in the previous embodiments.
The recording layer 57 is made of a material that causes refractive index modulation in the vicinity of the condensing point of the laser light, like the recording layer 46, but the refractive index of the recording layer 57 is made different from that of the recording layer 46. That is, the interface between the recording layer 57 and the recording layer 46 functions as a reflecting surface.
The Young's modulus of the recording layer 57 is set lower than that of the recording layer 46.

FIG. 11 is a diagram for explaining the recording / reproducing principle of the optical recording medium 55 according to the fourth embodiment.
In this case, as shown in FIG. 11A, the recording layer 46 and the recording layer 57 are obtained by performing a recording operation by appropriately condensing laser light on the upper and lower surfaces of the recording layer 46 (or the recording layer 57). A refractive index modulation portion will be formed on both sides of this. That is, a refractive index modulation portion is formed in a portion in the vicinity of the upper surface and the lower surface of the recording layer 46 and straddling the recording layer 46 and the recording layer 57.
Specifically, the portions near the upper and lower surfaces of the recording layer 46 in the recording layer 46 that are near the laser beam condensing point, and the upper and lower surfaces of the recording layer 46 in the recording layer 57. A refractive index modulation portion is formed with respect to each of the vicinity portions of the recording layer 57 (in other words, the lower surface and the upper surface of the recording layer 57) and the vicinity of the condensing point of the laser beam.
In this case, since the Young's modulus of the recording layer 57 is set lower than that of the recording layer 46, the recording layer 57 protrudes outside the recording layer 46 in the vicinity of the condensing point of the laser beam as shown in the figure. The upper and lower surfaces of the recording layer 46 are also deformed.

Here, as shown in FIGS. 11B and 11C, the refractive index of the recording layer 46 is N, the refractive index of the recording layer 57 is n, and the refractive index of the refractive index modulation portion formed on the recording layer 46 side is N ′. The refractive index of the refractive index modulation portion formed on the recording layer 57 side is set to n ′, and the height of the portion of the refractive index modulation portion that is above the apex of the convex surface deformation portion is set to dm. .
In this case, the optical optical path length difference Do between the mark forming portion and the non-forming portion on the upper surface side of the recording layer 46 is as shown in FIG. 11B.

Do = {(n′−n) · dm + n · ds} × 2

It is expressed.
Further, the optical optical path length difference Do between the mark forming portion and the non-forming portion on the lower surface side of the recording layer 46 is as shown in FIG. 11C.

Do = {(N′−N) · dm−N · ds} × 2

It is expressed.

  In this case as well, the edge surface of the refractive index modulation portion functions as a reflecting surface as in the case of FIG. 9B. Accordingly, in this case as well, strictly speaking, the reflected light component from such an edge surface contributes to the signal level difference between the mark forming portion and the non-forming portion on both the upper and lower surfaces of the recording layer 46. .

  Also in the fourth embodiment, the power of the recording laser beam is set to a level that does not lead to the formation of the hole mark according to the characteristics of the recording layers 46 and 57.

  Also in the fourth embodiment, the point that it is desirable that the thickness of the intermediate layer 51 and the recording layer 46 be at least 5 μm or more is the same as in the previous embodiments.

Here, it can be seen that the number of recordable interfaces can be set to 2x with respect to the number x of repeated laminations also in the optical recording medium 55 of the fourth embodiment. That is, in the fourth embodiment as well, in the same manner as in each of the previous embodiments, the number of repetitions x required for realizing the same recording capacity is recorded for one conventional recording layer. Compared to a multilayer optical recording medium, it can be halved. For confirmation, a conventional multilayer optical recording medium is one in which an intermediate layer / recording layer / intermediate layer ... are repeatedly laminated.

<5. Fifth embodiment>

FIG. 12 is a cross-sectional view of an optical recording medium 60 according to the fifth embodiment.
As compared with the optical recording medium 55 of the fourth embodiment, the optical recording medium 60 of the fifth embodiment has a recording layer 61 instead of the recording layer 46 and a recording layer 62 instead of the recording layer 57. Is different.
The recording layer 61 and the recording layer 62 are configured to have a property of causing refractive index modulation in a relatively low temperature state before the deformation of the interface accompanying thermal expansion in response to laser light irradiation occurs.
The recording layer 61 and the recording layer 62 have different refractive indexes.

FIG. 13 is a diagram for explaining the recording / reproducing principle of the optical recording medium 60 according to the fifth embodiment.
For the optical recording medium 60 of the fifth embodiment, the recording operation is performed by appropriately condensing the laser beam on the upper and lower surfaces of the recording layer 61 (or recording layer 62) as shown in FIG. 13A. As described above, the portions in the recording layer 61 that are in the vicinity of the upper surface and the lower surface of the recording layer 61 and in the vicinity of the condensing point of the laser beam, and the upper and lower surfaces of the recording layer 61 in the recording layer 62. In other words, a refractive index modulation portion is formed with respect to a portion in the vicinity of each of the recording layer 62 (the lower surface and the upper surface) and a portion in the vicinity of the laser beam condensing point.
At this time, as described above, since the recording layer 61 and the recording layer 62 are made of a material that undergoes refractive index modulation at a relatively low temperature before the interface deformation occurs, the interface deformation occurs as shown in the figure. There can be no (almost zero). In other words, by setting the power of the recording laser light to a power that does not cause interface deformation, a refractive index modulation mark that does not involve interface deformation as shown in the figure (interface deformation is almost zero) is formed. be able to.
When a dye-based recording material used in a write-once disc such as a DVD (Digital Versatile Disc) is used as the recording layer material, the interface is deformed when the power of the laser beam is increased. It has been previously confirmed that refractive index modulation occurs. That is, refractive index modulation occurs at a relatively low temperature before the interface deformation occurs.

In this case, the optical optical path length difference Do of the reflected light between the mark formation portion and the non-formation portion on the upper surface side of the recording layer 61 (that is, the lower surface side of the recording layer 62) is n. When the height of the refractive index modulation portion formed on the recording layer 62 side and its refractive index are set to dm and n ′, respectively, as shown in FIG. 13B.

Do = (n′−n) · dm × 2

It is expressed.
The optical path length difference Do of the reflected light between the mark forming portion and the non-forming portion on the lower surface side of the recording layer 61 (that is, the upper surface side of the recording layer 62) is N. When the height of the refractive index modulation portion formed on the layer 61 side and its refractive index are set to dm and N ′, respectively, as shown in FIG. 13C.

Do = (N′−N) · dm × 2

It is expressed.

  Also in this case, the edge surface of the mark functions as a reflection surface. Strictly speaking, the reflected light component from such an edge surface also contributes to the signal level difference between the mark forming portion and the non-forming portion. This is the same as in the case of the second to fourth embodiments.

  In the fifth embodiment, it is the same as in the previous embodiments that the thickness of the recording layers 61 and 62 is desirably 5 μm or more.

Here, in the above description, as a specific method for preventing the deformation of the interface, the recording layers 61 and 62 made of a material that causes refractive index modulation at a relatively low temperature before the interface deformation occurs are stacked. Although the method is exemplified, as a method for preventing the deformation of the interface, for example, a method of forming the recording layer laminated structure in a state of being pressed from above and below can be adopted. In this case, in the molded optical recording medium, a force that presses each other between the recording layers in the stacking direction is generated, and accordingly, deformation of the interface can be suppressed accordingly.

<6. Sixth Embodiment>

FIG. 14 is a cross-sectional structure diagram of an optical recording medium 65 according to the sixth embodiment.
This optical recording medium 65 is different from the optical recording medium 10 of the first embodiment in that an intermediate layer 66 is provided instead of the intermediate layer 4 and a recording layer 67 is provided instead of the recording layer 5. .
The recording layer 67 is of a property that causes melting in response to heating near the condensing point in response to irradiation of the recording laser beam. This corresponds to a recording material based on a general thermoplastic resin having a glass transition temperature as described in the material 3) above.
The intermediate layer 66 has a property that has a higher Young's modulus than the recording layer 67.
At this time, the intermediate layer 66 and the recording layer 67 have different refractive indexes.

  In this case, the optical recording medium 65 is formed in a state where a laminated structure of the intermediate layer 66 and the recording layer 67 is pressed from above and below. That is, in the molded optical recording medium 65, a force is generated between the intermediate layer 66 and the recording layer 67 that presses each other in the stacking direction.

FIG. 15 is a diagram for explaining the recording / reproducing principle of the optical recording medium 60 according to the sixth embodiment.
As shown in FIG. 15A, the optical recording medium 60 having the above-described configuration is subjected to a recording operation by appropriately condensing laser light on the upper surface and the lower surface of the recording layer 67. In this case, a mark (hereinafter referred to as a concave deformation mark) is formed by deforming such that the shape of the upper surface and the lower surface is convex toward the inside of the recording layer 67.
As can be understood from the description with reference to FIG. 14, in this case, the intermediate layer 66 is made of a hard material and is pressed in the stacking direction. From this, when the laser beam is focused on the upper surface and the lower surface of the recording layer 67, heating (melting) in the vicinity of the focusing point in the recording layer 67 occurs, and the pressure state is not affected. Due to the stress of the intermediate layer 66, the portion of the intermediate layer 66 near the laser light condensing point swells in a convex shape with respect to the recording layer 67 side. As a result, a concave deformation mark as shown in the figure is formed.
In addition, it is thought that the heating expansion which arises in the vicinity of the laser beam condensing point of the intermediate layer 66 partially contributes to the formation of the concave deformation mark.

In this case, the optical optical path length difference Do of the reflected light between the mark forming portion and the non-forming portion on the upper surface side of the recording layer 67 is such that the refractive index of the intermediate layer 66 is n and the recording layer 67 as shown in FIG. Where N is the refractive index and ds is the height of the concave deformation mark.

Do = n · ds × 2

It can be expressed as.
Further, the optical path length difference Do of the reflected light between the mark forming portion and the non-forming portion on the lower surface side of the recording layer 67 is:

Do = N · ds × 2

It can be expressed as.
As can be seen with reference to these equations, in this case as well, the recording code can be determined based on the reflected light phase difference between the mark forming portion and the non-forming portion.

  Also in the sixth embodiment, the power of the recording laser light is set to a level that does not lead to the formation of the hole mark according to the characteristics of the recording layer 67.

  Also in the sixth embodiment, it is desirable to make the thickness of the intermediate layer 66 and the recording layer 67 at least 5 μm or more as in the case of the previous embodiments.

Further, in the sixth embodiment, as in the first and second embodiments, when the recording mark is formed by the temperature rising deformation due to nonlinear light absorption, the recording laser light In order to obtain good recording characteristics (reproduction characteristics), it is preferable that the condensing point does not coincide with the interface but is offset to some extent from the interface toward the recording layer 67 side.

<7. Modification>

As mentioned above, although embodiment which concerns on this technique was described, this technique should not be limited to the specific example demonstrated so far.
For example, a surface treatment (modified) using, for example, plasma or ion beam is applied to the interface of the recording layer so that the interface of the recording layer functions effectively as a reflecting surface (that is, a refractive index difference at the interface is effectively obtained). Quality treatment).

In the above description, as an example of the structure of the optical recording medium in which a plurality of interfaces between the first layer and the second layer having different refractive indexes are formed, layers having different refractive indexes are alternately arranged. The structure in which the layers are repeatedly laminated has been illustrated, but as a structure having such an interface, for example, a structure as shown in FIG. 16A can be given.
That is, with respect to the laminated structure (FIG. 16B) in which the layers 71 having the same refractive index are repeatedly laminated (FIG. 16B), the refractive index modulation processing is performed on each of the upper part and the lower part of the interface so that FIG. As shown, a refractive index modulation layer 71A and a refractive index modulation layer 71B are formed. In this case, the refractive index modulation process is performed so as to give a refractive index difference between the refractive index modulation layer 71A and the refractive index modulation layer 71B.
For example, with such a configuration, the interface between the refractive index modulation layer 71A and the refractive index modulation layer 71B corresponds to the “interface between the first layer and the second layer having different refractive indexes”. For confirmation, the layer 71 having the same refractive index is a combination of a recording layer and an intermediate layer as described in the first to sixth embodiments, or a recording layer. Only a combination of these may be used.

  In the sense that a plurality of interfaces of layers having different refractive indexes are formed, at least one of the refractive index modulation layer 71A and the refractive index modulation layer 71B is formed as the refractive index modulation process. It is enough to go. That is, for example, if only the refractive index modulation layer 71A side is formed by the refractive index modulation process, the upper surface of the refractive index modulation layer 71A functions as an “interface”. If only the refractive index modulation layer 71B side is formed, its lower surface functions as an “interface”.

  The modification described with reference to FIG. 16 is suitable when there is a situation where it is desirable in the optical recording medium manufacturing process that each layer material handled in the laminating step is the same (in the sense that the refractive index is not different). is there.

In the present technology, the first layer and the second layer are not necessarily required to have different refractive indexes.
Even when the refractive index of the first layer and the second layer are the same, for example, when forming a mark by refractive index modulation such as void or coloring as in the third to fifth embodiments, The relationship between the reflectance and transmittance of the mark portion can be made different from the case of performing conventional void recording. In other words, as a result, it is possible to ensure that the reflectance of the mark portion is as high as necessary for reproduction, and that the transmittance of the mark portion is higher than when void recording is performed.
According to this, as compared with the case of the void recording, the situation in which the improvement of the reproduction signal level and the suppression of the crosstalk in the depth direction are in a trade-off relationship is mitigated, and as a result, an appropriate S / N is achieved. Adjustment can be made easier.

In the above description, the reference surface Ref is provided above the recordable area 7. However, the reference surface Ref can be provided below the recordable area 7.
When the reference surface Ref is provided on the lower side of the recordable area 7, the reflective film provided for the reference surface Ref has characteristics opposite to those of the selective reflection film 3, that is, selectively reflects only the servo laser beam. It is desirable to provide a material having such characteristics. This is because if a selective reflection film having such characteristics is provided, stray light during reproduction (due to reflected light from layer positions other than the layer position to be reproduced) can be effectively suppressed.

Further, for example, the tracking servo control for the recording laser beam can be performed based on the reflected light of the servo / playback laser beam, so that the upper surface and the lower surface of the first layer (or the second layer) can be controlled. It can also be said that a guide groove as a groove is formed in each. In this case, the recording mark can be formed on a groove (concave portion), a land (convex portion), or both.
If the groove is formed at the interface in this way and the tracking servo control for the recording laser beam is performed based on the groove (track), the reference surface Ref can be used as described above with reference to FIGS. Compared with the case where the tracking servo control for the recording laser beam is performed using the reflected light of the servo laser beam, the reliability of the tracking servo for the recording laser beam can be improved.
However, in the case where the tracking servo control for the recording laser beam is performed using the reflected light of the servo laser beam from the reference surface Ref as described in FIGS. Therefore, the manufacturing process of the optical recording medium can be simplified, and the manufacturing cost of the optical recording medium can be reduced accordingly.

In the above description, the focus servo control for the servo laser light is performed by controlling the objective lens 23 (biaxial actuator 24), and the focus servo control for the servo / reproduction laser light is performed for the servo / reproduction. Although the case where it is performed by controlling the focus mechanism for recording / reproducing light inserted in the optical path of the laser beam is exemplified, focus servo control for each laser beam can also be realized by the following method.
That is, the focus servo control for the servo / reproducing laser beam is performed by controlling the biaxial actuator 24 based on the focus error signal FE-sp, and the focus servo control of the servo laser beam is performed on the optical path of the servo laser beam. This is performed by inserting a separate focus mechanism (for example, having the same configuration as the upper recording / relighting focus mechanism) and controlling the focus mechanism based on the focus error signal FE-sv.

  In the description so far, the case where a guide groove such as a groove or a pit is formed as the position guide formed on the reference surface Ref is exemplified. However, as the position guide, for example, a mark is recorded on a phase change film or the like. And may be formed.

  In the description so far, the case where the optical recording medium of the present invention is a disc-shaped recording medium is exemplified, but other shapes such as a rectangular shape may be used.

In addition, about this technique, it can be set as a structure as shown to the following (1)-(12).
(1)
In an optical recording medium having a structure in which a plurality of interfaces between the first layer and the second layer are formed, a laser beam is appropriately condensed in the vicinity of the interface until the empty mark is formed in the vicinity of the interface. A recording apparatus for forming a recording mark that does not reach the above-mentioned position and is accompanied by modulation of refractive index and / or shape change of the interface.
(2) The recording apparatus according to (1), wherein the first layer and the second layer have different refractive indexes.
(3)
The first layer is configured to expand near the condensing point of the laser beam,
The second layer is set to have a lower Young's modulus than the first layer,
A recording mark that does not reach the formation of the empty mark at the interface and that has a change in shape of the interface according to an aspect that protrudes toward the second layer side. (1) or The recording apparatus according to (2).
(4)
The first layer is configured to cause the expansion and the modulation of the refractive index according to the power of the laser beam,
A recording mark that does not lead to the formation of an empty mark in the vicinity of the interface, and is accompanied by both modulation of the refractive index and shape change of the interface due to a convex shape toward the second layer. The recording apparatus according to (3), wherein a recording mark is formed.
(5)
The first layer is configured such that the refractive index is modulated near the condensing point of the laser beam,
The second layer is set to have a higher Young's modulus than the first layer,
The recording apparatus according to (1) or (2), wherein a recording mark that does not reach the formation of the empty mark and is formed by modulation of a refractive index is formed in the vicinity of the interface.
(6)
Both the first layer and the second layer are configured such that the refractive index is modulated near the condensing point of the laser beam,
A recording mark that is in the vicinity of the interface and straddles the first layer and the second layer is a recording mark that does not lead to formation of the empty mark, and the refractive index is modulated. The recording apparatus according to (1) or (2), wherein a recording mark is formed.
(7)
The second layer is set to have a lower Young's modulus than the first layer,
A recording mark that does not reach the formation of the empty envelope mark in the vicinity of the interface, is accompanied by a change in shape of the interface according to an aspect that protrudes toward the second layer side, and the first layer and the above The recording apparatus according to (6), wherein a recording mark having a refractive index modulation portion is formed in a portion straddling the second layer.
(8)
The first layer is configured such that refractive index modulation occurs in a relatively low temperature state before the interface is deformed due to thermal expansion in response to the laser light irradiation, or the first layer The layered structure of the layer and the second layer is molded in a state where pressure is applied from above and below,
A recording mark that is in the vicinity of the interface and straddles the first layer and the second layer and that does not lead to the formation of the empty mark and is due to modulation of the refractive index. The recording apparatus according to (6), wherein a recording mark is formed.
(9)
The first layer is configured to cause melting in response to heating in the vicinity of a condensing point in response to the laser light irradiation,
The second layer is set to have a higher Young's modulus than the first layer,
The laminated structure of the first layer and the second layer is molded in a state of being pressed from above and below,
A recording mark that does not reach the formation of the empty mark at the interface and that has a shape change of the interface according to an aspect that protrudes toward the first layer is formed. (1) or ( The recording apparatus according to 2).
(10)
The recording apparatus according to (1), (2), or (4) to (8), wherein the refractive index is modulated by forming a void.
(11)
The recording apparatus according to (1), (2), or (4) to (8), wherein the refractive index is modulated by coloring.
(12)
The recording apparatus according to any one of (2) to (11), further including a focus servo control unit that performs focus servo control on the laser light based on a result of detecting reflected light from the interface.

  1, 45, 50, 55, 60, 65 Optical recording medium, 2 cover layer, 3 selective reflection film, 4, 51, 66 intermediate layer, 5, 46, 57, 61, 62, 67 recording layer, 7 recordable area 10 Recording device, 56 Adhesive layer (intermediate layer)

Claims (15)

In an optical recording medium having a structure in which a plurality of interfaces between the first layer and the second layer are formed, a laser beam is appropriately condensed in the vicinity of the interface until the empty mark is formed in the vicinity of the interface. A recording apparatus for forming a recording mark that does not reach the above-mentioned position and is accompanied by modulation of refractive index and / or shape change of the interface.   The recording apparatus according to claim 1, wherein the first layer and the second layer have different refractive indexes. The first layer is configured to expand near the condensing point of the laser beam,
The second layer is set to have a lower Young's modulus than the first layer,
The recording mark that does not reach the formation of the empty mark at the interface and that has a change in shape of the interface according to an aspect that protrudes toward the second layer side. Recording device. The first layer is configured to cause the expansion and the modulation of the refractive index according to the power of the laser beam,
A recording mark that does not lead to the formation of an empty mark in the vicinity of the interface, and is accompanied by both modulation of the refractive index and shape change of the interface due to a convex shape toward the second layer. The recording apparatus according to claim 3, wherein a recording mark is formed. The first layer is configured such that the refractive index is modulated near the condensing point of the laser beam,
The second layer is set to have a higher Young's modulus than the first layer,
The recording apparatus according to claim 2, wherein a recording mark that does not reach the formation of the empty mark and is formed by modulation of a refractive index is formed in the vicinity of the interface. Both the first layer and the second layer are configured such that the refractive index is modulated near the condensing point of the laser beam,
A recording mark that is in the vicinity of the interface and straddles the first layer and the second layer is a recording mark that does not lead to formation of the empty mark, and the refractive index is modulated. The recording apparatus according to claim 2, wherein an accompanying recording mark is formed. The second layer is set to have a lower Young's modulus than the first layer,
A recording mark that does not reach the formation of the empty envelope mark in the vicinity of the interface, is accompanied by a change in shape of the interface according to an aspect that protrudes toward the second layer side, and the first layer and the above The recording apparatus according to claim 6, wherein a recording mark having a refractive index modulation portion is formed in a portion straddling the second layer. The first layer is configured such that refractive index modulation occurs in a relatively low temperature state before the interface is deformed due to thermal expansion in response to the laser light irradiation, or the first layer The layered structure of the layer and the second layer is molded in a state where pressure is applied from above and below,
A recording mark that is in the vicinity of the interface and straddles the first layer and the second layer and that does not lead to the formation of the empty mark and is due to modulation of the refractive index. The recording apparatus according to claim 6, wherein a recording mark is formed. The first layer is configured to cause melting in response to heating in the vicinity of a condensing point in response to the laser light irradiation,
The second layer is set to have a higher Young's modulus than the first layer,
The laminated structure of the first layer and the second layer is molded in a state of being pressed from above and below,
The recording mark which is a recording mark that does not lead to the formation of the empty mark at the interface and is accompanied by a shape change of the interface according to an aspect that protrudes toward the first layer side. Recording device.   The recording apparatus according to claim 1, wherein the refractive index is modulated by forming a void.   The recording apparatus according to claim 1, wherein the refractive index is modulated by coloring. The recording apparatus according to claim 2, further comprising a focus servo control unit that performs focus servo control on the laser light based on a result of detecting reflected light from the interface. In an optical recording medium having a structure in which a plurality of interfaces between the first layer and the second layer are formed, a laser beam is appropriately condensed in the vicinity of the interface until the empty mark is formed in the vicinity of the interface. A recording method for forming a recording mark that does not reach the above-mentioned position and is accompanied by modulation of refractive index and / or shape change of the interface. While having a structure in which a plurality of interfaces between the first layer and the second layer are formed,
An optical recording medium in which a recording mark that does not lead to formation of an empty mark is formed in the vicinity of the interface, which is accompanied by modulation of refractive index and / or shape change of the interface.   The optical recording medium according to claim 14, wherein an interval between the interfaces is 5 μm or more.

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