JP2003099939A - Optical recording/reproducing method and optical recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording/reproducing method and optical recording/reproducing device to record a boundary area such that a reflection factor/transmission factor becomes an intermediate value between values of a recorded area and a non-recorded area, on a boundary portion between the recorded area and the non-recorded area on an optical disk which has a recording layer constituted of two or more layers. SOLUTION: This optical recording/reproducing method constituted so that a laser beam is radiated from one side of an optical recording medium which has a plurality of recording layers laminated, so that information is recorded on a selected recording layer, and so that information is reproduced by capturing a reflected light reflected from a recording layer, is characterized in that a boundary area for preventing a rapid variation in the quantity of light of an irradiation light and a reflected light is recorded between a recorded area where information has been recorded on the recording layer and a non-recorded area where information is not yet recorded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and an optical recording / reproducing apparatus, and more particularly to an optical recording / reproducing method and an optical recording / reproducing apparatus for an optical recording medium having multiple recording layers.

[0002]

2. Description of the Related Art In an optical recording medium, for example, a DVD-RAM which is a rewritable optical disk of a phase change system, information is recorded by changing the intensity of light focused and irradiated on the disk to form a phase change mark array. To do. On the other hand, the reproduction of information is performed by converging and irradiating light having a constant intensity, which is lower than that in the case of recording, onto the disk and detecting the phase change mark array from the reflected light amount.

As a method for improving the recording capacity of one RAM type optical disk, one-sided two-layered recording film can be considered. This follows the single-sided, double-layer method adopted in DVD-ROMs, which are read-only optical discs, and it irradiates a disc manufactured by separating two recording layers with a transparent layer. The light is condensed from the same side, and recording / reproducing is performed in either selected recording layer. For example, when information is recorded / reproduced on / from a recording layer on the back side (hereinafter referred to as a second recording layer) when viewed from the light incident direction, the recording layer on the front side relative to the light incident surface (hereinafter referred to as “recording layer”). , Referred to as the first recording layer), the transmittance of the first recording layer changes depending on the recorded / unrecorded state of the area irradiated by the recording / reproducing light beam. As a result, when the state of the first recording layer irradiated by the recording / reproducing light beam changes from the recorded state to the unrecorded state or from the unrecorded state to the recorded state, the second recording layer Since the amount of light reaching the optical disk changes abruptly, it is impossible to stably record / reproduce information.

Further, when information is reproduced from the second recording layer, the reflected light from the second recording layer is superimposed on the reflected light from the first recording layer. The reflectance of the first recording layer changes depending on the recorded / unrecorded state of the region of the first recording layer irradiated by the light flux. This allows
The state of the first recording layer irradiated by the recording / reproducing light flux is
When the recorded state changes to the unrecorded state or the unrecorded state changes to the recorded state, the reflected light from the second recording layer, that is, the reproduction signal intensity changes, and information cannot be stably reproduced. .

By the way, the track centers of the first recording layer and the second recording layer are aligned with each other in mechanical accuracy, but they include a slight deviation. Therefore, when the optical disc rotates during recording / reproducing of information, eccentricity occurs, and the track irradiated with the light flux of the recording / reproducing light deviates between the first recording layer and the second recording layer. For example, when information is recorded / reproduced on / from a certain track of the second recording layer, the recording / reproducing light beam emitted to the first recording layer is decentered to change from the recorded state to the unrecorded state. Alternatively, the unrecorded state may change to the already recorded state. Then, the transmittance of the recording / reproducing light applied to the second recording layer changes when it passes through the first recording layer, and the amount of light reaching the second recording layer changes abruptly. It becomes impossible to record stably. Also, the reproduction light reflected from the second recording layer is
When passing through the recording layer, the reflected light of the first recording layer is superimposed and the reproduction signal intensity changes, and it becomes impossible to stably record information.

Further, although the case where information is recorded / reproduced on the track having the second recording layer has been described here, the present invention is not limited to this, and information is recorded on the track having the first recording layer. The same applies when performing reproduction. That is, since the state of the second recording layer irradiated by the recording / reproducing light flux changes according to the recorded / unrecorded state,
The reflected light from the first recording layer is superposed on the reflected light from the second recording layer and the reproduction signal intensity is largely changed, and the stability of reproduction on the optical disc is impaired.

[0007]

As described above, in the prior art,
The tracks on the first recording layer and the second recording layer irradiated by the recording / reproducing light beam are irradiated in a state of being deviated due to eccentricity. Therefore, for example, when information is recorded / reproduced on a track having the second recording layer, the track on the first recording layer irradiated by the light flux of the recording / reproducing light changes from the recorded state to the unrecorded state. Alternatively, the unrecorded state changes to the recorded state, and the transmittance of the first recording layer changes. As a result, the recording / reproducing light applied to the second recording layer is the first
However, there is a problem that the amount of light abruptly changes before it reaches the second recording layer after passing through the recording layer, and information cannot be stably recorded.

Further, when the reproduction light reflected from the second recording layer passes through the first recording layer, the reproduction light is superposed on the reflection light of the first recording layer and the reproduction signal intensity changes to stabilize the reproduction of information. There was a problem that I could not do it.

Further, when the information is reproduced on the track having the first recording layer, the reflectance of the second recording layer irradiated by the reproducing light beam changes depending on the recorded / unrecorded state. Therefore, there is a problem that the reflected light from the first recording layer is superimposed on the reflected light from the second recording layer and the reproduction signal strength is largely changed, and the stability of reproduction on the optical disc is impaired. .

The present invention is intended to solve such a problem, and an optical disc having two or more recording layers has a reflectance / transmittance recorded region at the boundary between the recorded and unrecorded regions. It is an object of the present invention to realize an optical recording / reproducing method and an optical recording / reproducing apparatus for recording a boundary area having an intermediate value between the values of the unrecorded area and the unrecorded area.

[0011]

According to the present invention, in order to achieve the above object, a selected recording is performed by irradiating a laser beam from one surface of an optical recording medium having a plurality of recording layers laminated. In an optical recording / reproducing method of recording information on a layer and obtaining reflected light from the recording layer to reproduce the information, an already recorded area in which the information is recorded on the recording layer, Between the unrecorded area that has not been recorded,
It is characterized in that a boundary area is recorded to prevent a rapid change in the light quantity of the irradiation light and the reflected light.

With the above configuration, even when recording / reproducing is performed on another information recording layer, the degree of interference due to the change in reflectance or transmittance in the information recording layer having the recorded area and the unrecorded area is reduced. It is possible to prevent sudden changes and stably record and reproduce information.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the overall structure of an optical recording / reproducing apparatus according to an embodiment of the present invention.
In FIG. 1, an optical disc 1 which is an information recording medium has a D
It has a single-sided two-layer structure in which two phase-change recording films, which are the same as the VD-RAM, are laminated. A transparent layer 4 is interposed between the lower first recording layer 2 and the upper second recording layer 3. That is, the first and second recording layers 2, 3 with the transparent layer 4 interposed.
Are stacked. The optical disc 1 is rotationally driven by a spindle motor 5 at a predetermined speed.

The optical pickup 7 irradiates the optical disc 1 with laser light from the lower side, focuses it on the selected one of the first and second recording layers by the objective lens 9, and selects it. Recording and reproduction are performed only on the recording layer.

The objective lens 9 is driven by a focus actuator 11 provided with a magnet (not shown) and a moving coil that cooperates with the magnet so that the objective lens 9 can be moved toward or away from the optical disk 1. Further, like the focus actuator 5, the objective lens 9 can be moved in the radial direction of the optical disc 1 by a tracking actuator 13 having a magnet and a moving coil (not shown). Then, the laser light emitted by the semiconductor laser provided in the optical pickup 7 is focused on the recording layer of the optical disc 1 via the objective lens 9, and is reflected by being changed depending on the presence or absence of pits on the optical disc 1. Not Received by the photo detector.

The RF amplifier 14 is composed of, for example, an adder and a subtractor, and is adapted to generate and output a focus error signal, a tracking error signal and a reproduction signal from the information signal received by the photo detector.

The servo processing circuit 15, based on the generated focus error signal and tracking error signal,
A focus control signal and a tracking control signal that surely converge the laser light on the pit row to be traced are generated and supplied to the focus actuator 11 and the tracking actuator 13. by this,
A servo loop is formed and servo control is performed.

The signal processing circuit 17 converts the reproduction signal generated by the RF amplifier 14 into an electric signal.

The decoding circuit 19 performs decoding processing such as 8-16 demodulation and error correction processing on the electric signal converted by the signal processing circuit 17. Then, the decoded signal is transmitted to an external device (not shown) such as a host computer via an interface.

The record information storage memory 21 stores the record information transmitted from the host computer via the interface and also stores the boundary record information necessary for forming the boundary area. This boundary area is the area between the recorded area and the unrecorded area and gradually changes from the average transmittance and reflectance in the recorded area to the average transmittance and reflectance in the unrecorded area. The boundary area is formed by recording boundary information after recording the recording information and recording boundary recording information described later.
The average transmittance and reflectance in the recorded area are the transmittance and reflectance felt by the defocused beam. That is, in the recording of information (recorded area), recording marks and spaces (portions not marked)
Since the area ratio is 1: 1 on average in a wide range, it is the average of the transmittance / reflectance of the recording mark and the transmittance / reflectance of the space. Further, the average transmittance and reflectance in the unrecorded area means the transmittance and reflectance of the space because the unrecorded area can be interpreted as all spaces.

The encoding circuit 23 performs encoding processing such as 8-16 demodulation and error correction processing on the record information stored in the record information storage memory 21.

The recording waveform generation circuit 25 generates a recording pulse signal for recording on the optical disc 1 from the recording information encoded by the encoding circuit 23.

The LD drive control circuit 27, based on the recording pulse signal generated by the recording waveform generation circuit 25,
The semiconductor laser provided in the optical pickup 7 is controlled.

All of these device operations are performed by the controller 2
It is conducted under the control of 9.

FIG. 2A shows an optical disc in which a boundary area is provided between a recorded area and an unrecorded area.
FIG. 6 is a diagram showing a state in which the recording layer of FIG. 2B and 2C are cross-sectional views showing a state in which the laser light is applied to the positions X and Y of the recording / reproducing track of the optical disc of FIG.

In FIG. 2A, the optical disc 1 has two phase change recording type information recording layers laminated on one side. First
The recording layer is disposed on the front side with respect to the light incident surface, and the second recording layer is disposed on the rear side with respect to the light incident surface. The first recording layer is recorded by the optical pickup 7 so that the transmittance and reflectance of the recorded area where information is recorded from the inner peripheral side and the recorded area and the unrecorded area are changed stepwise. A boundary area and an unrecorded area that has not been recorded yet are formed. It is assumed that the optical pickup 7 records / reproduces from the position Y of the track having the second recording layer, that is, the recording / reproducing track shown in the drawing, toward the position X in the above-formed state.

Now, the recording / reproducing light emitted from the optical pickup 7 is moved to the position Y of the recording / reproducing track of the second recording layer.
Assuming that the light is focused, recording on the first recording layer
The luminous flux of the reproduction light illuminates the recorded area (FIG. 2C).
reference). Further, when the recording / reproducing light is focused on the position X of the recording / reproducing track of the second recording layer, it can be seen that the light flux of the recording / reproducing light on the first recording layer irradiates the boundary area. (See FIG. 2 (b)). This is because there is a limit to the accuracy of aligning the centers of a plurality of recording layers when manufacturing the optical disc 1 having a plurality of recording layers.

If there is this center deviation, eccentricity occurs when the optical disk 1 rotates, and when the recording / reproducing light focuses the position Y and the position X of the recording / reproducing track of the second recording layer, The area irradiated by the recording / reproducing light flux in the first recording layer changes. Then, in the area of the first recording layer, the transmittance between the recorded area and the unrecorded area is
The reflectance changes, and the amount of recording / reproducing light reaching the second recording layer or the intensity of reflected light (reproducing signal) from the second recording layer changes abruptly. Therefore, by forming the boundary area of the present invention continuously after the already recorded area, it is possible to prevent the light quantity of the recording / reproducing light and the reproduction signal intensity from being drastically changed.

In order to form this boundary area, it is necessary to first calculate the deviation due to the eccentricity of the first recording layer and the second recording layer to determine the range of the boundary area. That is, when recording / reproducing on the second recording layer, the number of tracks that can be irradiated with the light flux of recording / reproducing light on the first recording layer is calculated,
Determine the extent of the border area. The number of tracks that can be irradiated is δ, which is the eccentricity of the optical disc 1,
If the radius of the recording layer is R and the track pitch is Tp, then (2R + δ) / Tp [track] (1).

However, the range to be processed as the boundary area only needs to have a track corresponding to the radius of the area where the light beam irradiates the first recording layer, so that (R + δ) / Tp [track] .. 2)

Therefore, the boundary areas are provided by the number of tracks thus obtained. In reality, the controller 29 is (2)
The number of tracks is calculated using the formula, and the number of tracks is controlled so that a boundary area is continuously provided after the recording of the recording information is completed. The eccentricity amount information refers to the eccentricity amount information recorded in advance on the optical disc, and the range to be processed as the boundary area is determined. If the eccentricity amount information is not recorded in advance on the optical disc, the maximum value of the eccentricity amount determined by the optical disc standard may be used to determine the range to be processed as the boundary area.

The recording process of the boundary area will be described with reference to the flowchart of FIG.

It is assumed that both the first and second recording layers are unrecorded areas. When recording information on the first or second recording layer, the LD drive control circuit 27 is irradiated by the semiconductor laser provided in the optical pickup based on the recording information stored in the recording information storage memory 21. Control the laser light. The controlled laser light is focused on the first or second recording layer from the optical pickup 7 and the recording information is recorded (step S1). Then, the controller 29 calculates the deviation due to the eccentricity using the above equation (2) and determines the range of the boundary area (steps S3 and S).
5). Further, the controller 29 uses the encoding circuit 2
3. The recording waveform generation circuit 25 and the LD drive control circuit 27 are controlled to read the boundary recording information stored in the recording information storage memory 21 (step S7). By this control, the boundary recording information stored in the recording information storage memory 21 is read out, and the LD drive control circuit 27 determines in step S1.
The semiconductor laser is controlled so as to record the boundary record information after the record information recorded in step S (step S).
9). Therefore, the boundary recording information is recorded only within the calculated boundary area after the already recorded area where the recording information is recorded on the first or second recording layer of the optical disc 1.

Next, the boundary recording information recorded in the boundary area in step S9 will be described with reference to FIGS. 4 to 6.

In FIG. 4, in the boundary area, several tracks, for example, are set so that the average transmittance / reflectance in the recorded area gradually changes to the average transmittance / reflectance in the unrecorded area. Boundary recording information is recorded every two tracks. By recording in this way, for example, when recording / reproducing is performed on the second recording layer, the recording on the first recording layer irradiated by the optical path focused on the second recording layer is already performed. It is possible to have a transmittance / reflectance intermediate between the average transmittance / reflectance in the recorded area and the average transmittance / reflectance in the unrecorded area. That is, in the first recording layer, the irradiated recording / reproducing light beam is in a defocused state and therefore spreads considerably. In this state, when the entire boundary area recorded every two tracks is viewed, it is average. It is possible to obtain transmittance and reflectance.

In FIG. 5, the boundary recording information is recorded every few tracks in the boundary area of FIG. 4, but here, it is divided into two areas such as the first boundary area and the second boundary area. Then, the intervals of the tracks recorded in each boundary area are changed. When dividing, controller 2
9 determines the area to be divided from the number of tracks calculated using the above equation (2). The first boundary area is provided adjacent to the recorded area, the second boundary area is provided adjacent to the first boundary area, and the other is provided adjacent to the unrecorded area. First
In the boundary area of, information is recorded every M tracks.
In the boundary area of, information is recorded every N tracks. That is, when the boundary recording information is recorded in the first and second boundary areas so that the relationship of M <N is established, the average transmission is performed between the recorded area and the unrecorded area, that is, in the boundary area. The reflectance and the reflectance are changed in three steps from the value in the recorded area to the value in the unrecorded area. Therefore, the conversion between the transmittance and the reflectance can be made more gradual than in the boundary area of FIG. Although the case where the boundary area is divided into two has been described here, the same effect can be expected even when the boundary area is generalized and divided into K.

Further, in FIG. 6, although information is recorded at least every two tracks in the boundary area between the recorded area and the unrecorded area in FIGS. 4 and 5, it is assumed here that the information is recorded in continuous tracks. That is, recording is performed by changing the ratio of recording marks and spaces to be recorded in order to change the average transmittance and reflectance.

The transmissivity / reflectance of the recording mark is Tm, Rm
And the transmittance and reflectance of the space are Ts and Rs, the appearance ratio of the recording mark and the space is 50:50.
In the case of, the average transmittance T and reflectance R are: T = (1/2) × Tm + (1/2) × Ts ... (3) R = (1/2) × Rm + (1/2) × Rs ... (4)

Next, when the appearance ratio of the recording marks and spaces is a: b, T = (a / (a + b)) × Tm + (b / (a + b)) × Ts (5) R = (A / (a + b)) × Rm + (b / (a + b)) × Rs ... (6) All unrecorded areas are considered spaces.

To change the average transmittance / reflectance in the boundary area from the value in the recorded area to the unrecorded area,
It is understood that the appearance ratio of the recording mark and the space may be changed from 50:50 to 0: 100. Further, when the appearance ratio of the recording marks and spaces to be recorded in the boundary area is set to 25:75, for example, it can be realized simply by recording the repetitive signal of 2T recording marks and 6T spaces. Note that, as in the case of FIG. 5, the boundary area may be divided and the appearance ratio of the recording mark and the space may be changed. In this case, 1>a1> a2 should be satisfied, assuming that the appearance ratio of the recording marks and spaces is a1: 1 in the first boundary area and a2: 1 in the second boundary area.

Therefore, information is recorded on a recording layer of an optical disc having a plurality of recording layers, and when a boundary between an already recorded area and an unrecorded area occurs in this recording layer, a boundary area is provided, and a step is made at this boundary area. The transmittance and the reflectance are changed. Therefore, the boundary recording information is recorded every few tracks, or the interval between the tracks divided into two areas such as the first and second boundary areas and recorded in each boundary area is changed. Record by changing the frequency of appearance of recording marks and spaces.

The boundary recording information recorded in the boundary area may be information (user information) that the user wants to record. In this case, when the user information is stored in the recording information storage memory 21 via, for example, the host computer, the controller 29 detects and detects the recording information end signal indicating that the user information is nearing the end. The recording processing of the boundary area is started by the recording information end signal. The recording information end signal is added to the boundary recording information in advance by the host computer side.

The boundary recording information recorded in the boundary area may be different from the information desired by the user.
In this case, the dummy information stored in advance in the recorded information storage memory 21 is recorded.

As described above, according to the present invention, when the recorded area and the unrecorded area exist in the first recording layer, the stability is ensured even when the information is recorded / reproduced on the second recording layer. However, the effect of the present invention can be expected by performing the same processing even when the first recording layer and the second recording layer have an opposite relationship. Further, although the present invention has been described for the case where the number of recording layers is two,
Even when the number of recording layers is three or more, the effect of the present invention is not impaired. Further, according to the present invention, it is not necessary to specify the order of recording information on the first recording layer and the second recording layer, and it is sufficient to record the boundary area when recording on a certain recording layer, which is convenient. Further improve.

[0046]

As described above, even when recording / reproducing is performed on another recording layer, the degree of interference due to changes in transmittance and reflectance in a recording layer having a recorded area and an unrecorded area is reduced. Prevent sudden changes and record information stably
Playback can be performed. This is because the amount of light passing through the first recording layer is sharp regardless of whether information is recorded / reproduced on the second recording layer or reproduced on the first recording layer. In addition, since the intensity of the reflected light (reproduction signal) reflected from the first and second recording layers does not change significantly, it is possible to stably record / reproduce information.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an overall configuration of an optical recording / reproducing apparatus of an embodiment according to the present invention.

FIG. 2 is a diagram showing an optical disc in which a boundary area is provided between an already recorded area and an unrecorded area, in which a first recording layer and a second recording layer are misaligned.

FIG. 3 is a flowchart of a boundary area recording process.

FIG. 4 is a diagram showing a boundary area recorded every two tracks.

FIG. 5 is a diagram showing a boundary region divided into two regions.

FIG. 6 is a diagram showing a boundary area recorded by changing the appearance ratio of recording marks and spaces.

[Explanation of symbols]

1 optical disc 2 First recording layer 3 Second recording layer 4 transparent layer 5 Spindle motor 7 Optical pickup 9 Objective lens 11 Focus actuator 13 Tracking actuator 14 RF amplifier 15 Servo processing circuit 17 Signal processing circuit 19 Decoding circuit 21 Recorded information storage memory 23 Encoding circuit 25 Recording waveform generation circuit 27 LD drive control circuit

Claims (16)

[Claims] 1. A laser beam is irradiated from one surface of an optical recording medium having a plurality of laminated recording layers to record information on the selected recording layer, and the information is reflected from the recording layer. In the optical recording / reproducing method for reproducing the information by obtaining reflected light, the recording layer is reached between an already recorded area in which the information is recorded in the recording layer and an unrecorded area not yet recorded. An optical recording / reproducing method characterized by recording a boundary area for preventing an abrupt change in the light amount of the irradiation light and the reflected light from the recording layer. 2. A laser beam is irradiated from one surface of an optical recording medium having a plurality of laminated recording layers to record information on the selected recording layer and the information is reflected from the recording layer. In the optical recording / reproducing method of reproducing the information by obtaining reflected light, in the recorded area between the recorded area in which the information is recorded in the recording layer and the unrecorded area that is not yet recorded, A recording / reproducing method characterized by recording a boundary region having a transmittance and a reflectance intermediate between the average transmittance and reflectance of the unrecorded area and the average transmittance and reflectance of the unrecorded area. . 3. The optical recording / reproducing method according to claim 1, wherein in the boundary area, the information is recorded every N tracks (an integer value of N ≧ 1). 4. The boundary area divides an area between the recorded area and the unrecorded area into n areas, and N ₁ , N _2, ..., N _n for each of the divided areas. (1 <N ₁ <N ₂
3. The optical recording / reproducing method according to claim 1, wherein the recording is performed every << _n >, <Nn) tracks. 5. The light according to claim 1, wherein the boundary area is recorded so that the frequency of appearance of recording marks and spaces satisfies x: 1 (x <1). Recording and playback method. 6. The boundary area is defined as an area between the recorded area and the unrecorded area by L ₁ , L _2, ..., L _k ,.
L _n divided into n regions, the region L ₁ is adjacent to L ₂ , the region L _k is adjacent to the region L _k−1 and the region L _{k + 1} ,
The region L _n is adjacent to the region L _n-1 and the unrecorded area, each area _{L 1, L 2 ,,, L k} ,,, N 1 to L _n,
3. The optical recording / reproducing method according to claim 1, wherein the recording is performed every N ₂ , N _n (1 <N ₁ <N ₂ <,, <N _n ) tracks. 7. The boundary area is an area between the recorded area and the unrecorded area, which is L ₁ , L _2, ..., L _k ,.
L _n divided into n regions, the region L ₁ is adjacent to L ₂ , the region L _k is adjacent to the region L _k−1 and the region L _{k + 1} ,
The region L _n is adjacent to the region L _n-1 and the unrecorded area, the frequency of occurrence of the recording mark and the space in each area _{L 1, L 2 ,,, L k} ,,, L n x 1 : 1, x ₂ :
3. The optical recording / reproducing according to claim 1, wherein the recording is performed so as to satisfy the following condition: 1 ... x _n : 1 (1> x ₁ > x ₂ >, ...> x _n ). Method. 8. The information recorded in the boundary area comprises:
The optical recording / reproducing method according to claim 1, wherein the optical recording / reproducing method is user data. 9. A laser beam is irradiated from one surface of an optical recording medium having a plurality of laminated recording layers to record information on the selected recording layer, and the information is reflected from the recording layer. In an optical recording / reproducing apparatus that obtains reflected light and reproduces the information, an irradiating unit that irradiates the recording layer with the laser beam, and the laser beam that is irradiated by the irradiating unit, the recording layer is the The irradiating light reaching the recording layer and the irradiating light reaching the recording layer between the first recording device for recording information, the recorded region recorded by the first recording device, and the unrecorded region not recorded yet. An optical recording / reproducing apparatus comprising: a second recording unit that records a boundary area for preventing a sudden change in the amount of light reflected from the recording layer. 10. A laser beam is irradiated from one surface of an optical recording medium having a plurality of laminated recording layers to record information on the selected recording layer, and the information is reflected from the recording layer. In an optical recording / reproducing apparatus that obtains reflected light and reproduces the information, an irradiating unit that irradiates the recording layer with the laser beam, and the laser beam that is irradiated by the irradiating unit, the recording layer is the Between the first recording means for recording information, the recorded area recorded by the first recording means, and the unrecorded area not yet recorded,
The boundary area is recorded such that the average transmittance and reflectance in the recorded area and the average transmittance and reflectance in the unrecorded area have an intermediate transmittance and reflectance. An optical recording / reproducing apparatus, comprising: 11. The optical recording / reproducing apparatus according to claim 9, wherein in the boundary area, the information is recorded every N tracks (an integer value of N ≧ 1). 12. A dividing means for dividing an area between the recorded area and the unrecorded area into n areas, wherein the boundary area is N ₁ for each area divided by the dividing means. N _2, ..., N _n (1 <N ₁ <N ₂ <,, <N _n )
The optical recording / reproducing apparatus according to claim 9, wherein the recording is performed for each track. 13. The light according to claim 9, wherein the boundary area is recorded so that the frequency of appearance of recording marks and spaces satisfies x: 1 (x <1). Recording / playback device. 14. The boundary region is defined by L ₁ , L ₂ ,.
Comprising a dividing means for dividing the n region of the L _k ,,, L _n, the boundary region, the divided by dividing means the area L ₁ is adjacent to the L _2, the region L _k is the region L _{k -1} is adjacent to the region L _{k + 1} , and the region L _n is the region L _n-1.
And adjacent to the unrecorded area, and each area L ₁ , L ₂ ,.
_k, ..., L _n are N ₁ , N _2, ..., N _n (1 <N ₁ <N
The optical recording / reproducing apparatus according to claim 9, wherein the recording is performed every ₂ <, ..., <N _n ) tracks. 15. The boundary region is defined by L ₁ , L ₂ ,.
Comprising a dividing means for dividing the n region of the L _k ,,, L _n, the boundary region, the divided by dividing means the area L ₁ is adjacent to the L _2, the region L _k is the region L _{k -1} is adjacent to the region L _{k + 1} , and the region L _n is the region L _n-1.
And adjacent to the unrecorded area, and each area L ₁ , L ₂ ,.
The appearance frequencies of the recording marks and the spaces at _k , L _n are x ₁ : 1, x ₂ : 1, x _n : 1 (1> x ₁ > x).
The optical recording / reproducing apparatus according to claim 9 or 10, wherein recording is performed so that ₂ >,,,> x _n ). 16. The optical recording / reproducing apparatus according to claim 9, wherein the information recorded in the boundary area is user data.