JP2006172688A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium capable of obtaining a BCA reproduction signal having a good signal quality from BCA with respect to an optical information recording medium for reproducing BCA information without performing tracking.
An optical information recording medium comprising a substrate and a light absorbing layer formed of a pigment material on the substrate, wherein a user information region having a concavo-convex pattern including spiral or concentric grooves is formed. There is provided an optical information recording medium including a BCA on which information is recorded with a barcode provided on the inner circumference side of the user information area, and having a concavo-convex pattern different from the concavo-convex pattern of the user information area formed on the BCA.
[Selection] Figure 2

Description

  The present invention relates to an optical information recording medium, and more particularly to an optical information recording medium in which management information is recorded in a barcode.

  An optical information recording medium such as a DVD-ROM includes a medium having an area where information can be read without performing tracking servo control on the innermost periphery, and information is recorded with a barcode as such an area. BCA (Burst Cutting Area) is known (see, for example, Patent Documents 1 and 2). In Patent Document 1, in order to manage user information such as programs, data, and application information written in the user information area, or to protect the copyright, the BCA outside the user information area is different from the user information area. Management information is recorded by a modulation method.

  The BCA is formed at the manufacturing stage of the optical information recording medium as disclosed in Patent Document 2. For example, in the case of a DVD-ROM, the reflection film is removed with a YAG laser. In the BCA, identification information for each optical information recording medium such as a serial number is recorded and used for copyright protection. In the case of DVD-R, which is a write-once type optical information recording medium, there is a problem that when the reflective film is removed with a YAG laser like the DVD-ROM, the recording layer and the reflective film are peeled off. BCA information is recorded by forming a barcode in the groove portion in the area.

  Further, in the conventional DVD-R, a groove having the same shape as the user information area is formed in the BCA, and the information of the BCA is reproduced while tracking the groove.

JP-A-10-188361 JP-A-6-20312

  The present inventors have provided a BCA on the innermost periphery of the disc in the same manner as in the past for HD DVD-R using a dye material in the recording layer of HD DVD, which is a next generation optical disc. When the BCA information was reproduced without tracking control (only focus control was performed), the BCA information could not be reproduced accurately.

  The present invention has been made to solve the above-described problems. For example, the BCA information is also obtained for an optical information recording medium that reproduces the BCA information without performing tracking control, such as the above-mentioned HD DVD. An object of the present invention is to provide an optical information recording medium that can be reproduced with good signal quality.

According to an aspect of the present invention, there is provided an optical information recording medium comprising a substrate and a light absorption layer formed of a pigment material on the substrate:
A user information area in which a concavo-convex pattern including spiral or concentric grooves is formed;
A BCA provided on the inner circumference side of the user information area and having information recorded by a barcode;
An optical information recording medium is provided in which a concavo-convex pattern different from the concavo-convex pattern of the user information area is formed on the BCA.

  The inventors first formed a BCA with a mirror portion and recorded / reproduced BCA information on an HD DVD using a dye material for a light absorption layer (recording layer). A reproduction signal could not be obtained, and BCA information could not be reproduced accurately. This is because when the recording layer is formed so that the film thickness of the recording layer in the groove of the user information area is optimized, the BCA is formed in the mirror portion, so that the dye material does not accumulate sufficiently on the BCA, and the BCA This is because the upper recording layer becomes thinner. When a dye material is used for the recording layer, there is an optimum recording layer thickness range in order to obtain sufficient recording / reproduction characteristics, and the film thickness may be too thick or too thin than the optimum film thickness range. Sufficient recording / reproduction characteristics cannot be obtained. Therefore, it was found that when the BCA is formed at the mirror portion, a recording layer having a film thickness sufficient to reproduce the BCA information is not formed on the BCA, so that the BCA information cannot be reproduced accurately. . Therefore, the thickness of the recording layer on the BCA is increased so that the BCA information can be sufficiently reproduced. In this case, however, the thickness of the recording layer on the groove in the user information area becomes too thick, and the user information The recording characteristics of the area deteriorated.

  Further, the present inventors have formed a groove of the user information area in the BCA in the same manner as the conventional DVD-R in order to form a recording layer having a thickness optimal for information reproduction in both the BCA and the user information area. The same groove was formed in BCA, and BCA information was recorded and reproduced. However, in this case, the amplitude fluctuation of the BCA reproduction signal becomes large, and the BCA information cannot be reproduced accurately. This is because when the BCA information is reproduced without tracking control as in HD DVD, the reproduction beam is irradiated across the groove portion and the land portion of the BCA due to the eccentricity of the disc, that is, the film thickness of the recording layer. This is because the reproduction beam is irradiated so as to cross the thick region and the thin region, so that the amplitude of the reproduction signal fluctuates (a cross track signal is generated). More specifically, since the recording layer thickness is sufficiently large in the BCA groove portion, the reproduction signal amplitude is large. However, in the land portion, since the recording layer thickness is thin, a reproduction signal having sufficient amplitude cannot be obtained. As a result, the amplitude of the reproduction signal from the BCA varies.

  The present invention has been made to solve the above problems. In the optical information recording medium of the present invention, a recording layer having a sufficient thickness can be formed on the BCA without affecting the recording / reproducing characteristics of the user information area, and the amplitude fluctuation from the BCA can be achieved without performing the tracking control. A concavo-convex pattern different from the concavo-convex pattern in the user information area was formed on the BCA so that a reproduced signal with a small amount was obtained. As used herein, the term “different concavo-convex pattern” refers not only to the shape of the concavo-convex pattern (for example, the shape of grooves and pits), but also to the same shape (for example, track pitch, groove width). Etc.) also includes different uneven patterns.

In the optical information recording medium of the present invention, between the track pitch TP of the concavo-convex pattern of the BCA and the track pitch TPy of the concavo-convex pattern of the user information area,
TP <TPy (1)
It is preferable that the relationship is established.

In the optical information recording medium of the present invention, the concave / convex pattern of the BCA includes grooves, the width LW1 between the grooves of the BCA, the wavelength λ of the reproduction beam used for reproduction of the optical information recording medium, and the numerical aperture NA of the objective lens. Between
(LW1 × NA) /λ≦0.3 (2)
It is preferable that the relationship is established.

In the optical information recording medium of the present invention, the concave / convex pattern of the BCA includes embossed pit rows, the width LW2 between the embossed pit rows of the BCA, the wavelength λ of the reproduction beam used for reproducing the optical information recording medium, and the objective lens Between the numerical aperture NA of
(LW2 × NA) /λ≦0.3 (3)
It is preferable that the relationship is established.

In the optical information recording medium of the present invention, the concave / convex pattern of the BCA includes grooves and embossed pit rows formed between the grooves, and the wider one of the widths between the embossed pit rows and the grooves on both sides thereof. Between the width LW3 of the laser beam and the wavelength λ of the reproduction beam used for reproducing the optical information recording medium and the numerical aperture NA of the objective lens,
(LW3 × NA) /λ≦0.3 (4)
It is preferable that the relationship is established.

  When the concave / convex pattern is formed on the BCA so as to satisfy any one of the above formulas (1) to (4), for example, recording is performed with a film thickness that optimizes the recording characteristics of the user information area by spin coating. Even if the layer is formed by coating, the dye material is accumulated in the groove portion or the embossed pit portion of the BCA, and the film thickness of the recording layer on the BCA becomes sufficiently thick. Further, when a concavo-convex pattern is formed on the BCA so as to satisfy any one of the above formulas (1) to (4), land areas other than the BCA groove and emboss pits are used for recording and reproduction. The optical resolution is smaller than the optical resolution λ / (2 · NA) of the optical disk drive, and the size cannot be completely identified. In this case, if the reproduction beam is irradiated to the BCA without performing tracking, the reproduction beam is irradiated across the groove portion and the land portion of the BCA due to the eccentricity of the medium, but the area of the land portion is smaller than the optical resolution. Therefore, a reproduction signal obtained by averaging the reproduction signal of the land portion where the signal amplitude is hardly obtained and the reproduction signal of the groove portion and the emboss pit portion where the sufficient signal amplitude is obtained is obtained from the BCA. As a result, the amplitude fluctuation of the BCA reproduction signal can be suppressed.

Further, when the concave / convex pattern is formed on the BCA so as to satisfy any of the above formulas (1) to (4), between the minimum amplitude Imin of the BCA reproduction signal and the amplitude CT of the cross track signal,
Imin> CT
Thus, the BCA information can be reproduced with good signal quality. In the optical information recording medium of the present invention, since a concavo-convex pattern is also formed on the BCA, the reproduction signal level obtained from the groove and the embossed pit row when reproducing the BCA information and the reproduction signal obtained from the land other than those areas It is slightly different from the level and is somewhat affected by the cross track signal. However, according to the verification experiment of the present inventors, when the BCA information is reproduced without tracking by forming the concave / convex pattern of the BCA so as to satisfy any of the above formulas (1) to (4). Even if it is somewhat affected by the cross track signal, the minimum amplitude Imin of the reproduction signal becomes larger than the amplitude CT of the cross track signal, so that the BCA information can be reproduced more accurately. In this specification, the “amplitude of the cross track signal” means the fluctuation amount of the unrecorded level of the reproduction signal obtained from the BCA (the signal level obtained from the unrecorded portion of the BCA) and the recording level (the recorded portion of the BCA). Of the fluctuation level of the signal level obtained from (1).

Further, in the optical information recording medium of the present invention, when the BCA information is reproduced without tracking by forming a concavo-convex pattern on the BCA so as to satisfy any of the above formulas (1) to (4). Furthermore, between the reflectance of the higher one RH and the reflectance RL of the lower one of the reflectances of the recorded part and the unrecorded part of BCA,
(RH-RL) /RH≧0.2
The relationship is established. That is, the modulation degree of the BCA reproduction signal is 20% or more, and a BCA reproduction signal with good signal quality can be obtained.

Further, in the optical information recording medium of the present invention, between the track pitch TP of the BCA, the wavelength λ of the reproduction beam used for reproducing the optical information recording medium, and the numerical aperture NA of the objective lens,
(TP × NA) /λ≦0.6 (5)
The relationship is preferably established, and more preferably,
0.45 ≦ (TP × NA) /λ≦0.6 (6)
It is preferable that the relationship is established.

  In the optical information recording medium of the present invention, when the concave / convex pattern of BCA is formed by a groove, the groove is formed in the BCA so as to satisfy the above formula (2) and the above formula (5) or (6). The present inventors have found that the reproduction signal characteristics as described above can be obtained. When reproducing the BCA information by irradiating the BCA with the reproduction beam without tracking, the reproduction signal amplitude obtained when the spot center of the reproduction beam is located at the center of the groove, and the reproduction Of the amplitudes of the reproduction signals obtained when the beam spot center is located at the center between the grooves, one amplitude is larger than the other amplitude, and the ratio of the amplitude of one to the other Becomes 1.4 or less. That is, by forming a groove in the BCA so as to satisfy the above expression (2) and the above expression (5) or (6), a reproduction signal with very small amplitude fluctuation can be obtained from the BCA.

  The “reproduced signal amplitude” obtained from the BCA in this specification refers to the unrecorded level (signal level obtained from the unrecorded part of the BCA) and the recorded level (obtained from the recorded part of the BCA). This is the level difference from the signal level. The magnitude relationship between the amplitude of the reproduction signal obtained when the reproduction beam spot center is located at the center of the groove and the amplitude of the reproduction signal obtained when the reproduction beam spot center is located at the center between the grooves is as follows. Depending on the forming material of the recording layer (light absorption layer).

  In the optical information recording medium of the present invention, when the concave / convex pattern of BCA is formed with an embossed pit row, the embossed pit row is formed on the BCA so as to satisfy the above formula (3) and the above formula (5) or (6). Thus, the present inventors have found that the following reproduction signal characteristics can be obtained. When reproducing the BCA information by irradiating the BCA with the reproduction beam without tracking, the amplitude of the reproduction signal obtained when the spot center of the reproduction beam is located at the center of the embossed pit row; Of the amplitudes of the reproduction signals obtained when the spot center of the reproduction beam is located at the center between the embossed pit rows, one amplitude is greater than the other amplitude, and one amplitude and the other The ratio to the amplitude is 1.4 or less. That is, by forming an embossed pit row in the BCA so as to satisfy the above expression (3) and the above expression (5) or (6), a reproduction signal with very small amplitude fluctuation can be obtained from the BCA.

  In the optical information recording medium of the present invention, when the concave / convex pattern of BCA is formed by grooves and embossed pit rows provided between the grooves, the above formula (4) and the above formula (5) or (6) The present inventors have found that the following reproduction signal characteristics can be obtained by forming the embossed pit row in the BCA so as to satisfy the condition. When reproducing the BCA information by irradiating the BCA with the reproduction beam without tracking, the reproduction signal amplitude obtained when the spot center of the reproduction beam is located at the center of the groove, and the reproduction Of the amplitudes of the reproduction signals obtained when the beam spot center is located in the center between the groove and the embossed pit row, one amplitude is larger than the other amplitude, and one amplitude and the other The ratio to the amplitude is 1.4 or less. That is, by forming the groove and the embossed pit row in the BCA so as to satisfy the above expression (4) and the above expression (5) or (6), it is possible to obtain a reproduction signal with very small amplitude fluctuation from the BCA. it can.

  In the optical information recording medium of the present invention, either of the above formulas (2) to (4) and the above formula (1) (characteristic that the track pitch TP of BCA is narrower than the track pitch TPy of the user information area) It is preferable to form a concave / convex pattern of BCA so as to be established at the same time. However, the present invention is not limited to this, and if the concave / convex pattern of BCA is formed in a shape that satisfies any of the above formulas (2) to (4), the track pitch TP of BCA is the user information area. The track pitch TPy may be the same, or the BCA track pitch TP may be somewhat larger than the track pitch TPy in the user information area. The present inventors have confirmed through verification experiments that even in such a case, a reproduced signal with very small amplitude fluctuation can be obtained from BCA.

  In the optical information recording medium of the present invention, it is preferable to record and reproduce information in the user information area using a blue laser.

  According to the optical information recording medium of the present invention, the concave / convex pattern of BCA is formed in a shape different from the concave / convex pattern formed in the user information area and satisfying any of the above formulas (1) to (4). Therefore, it is possible to form a recording layer having a film thickness sufficient to obtain a BCA reproduction signal on the BCA, and even if BCA information is reproduced without performing tracking control, The minimum amplitude value can be made larger than the amplitude value of the cross track signal (amplitude fluctuation can be suppressed), and BCA information can be reproduced with good signal quality.

  Hereinafter, embodiments of the optical information recording medium of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

[Format structure of optical information recording medium]
The optical information recording medium of the present invention is a medium comprising a substrate and a recording layer (light absorption layer) formed of a dye material on the substrate, and shows an embodiment of the optical information recording medium of the present invention. It is shown in 1. FIG. 1 is a schematic plan view of the optical information recording medium of the present embodiment. As shown in FIG. 1, the optical information recording medium 1 records a BCA 2 for recording management information with a barcode from the inner circumference side, a management information area 3 for recording management information related to user information recording, and user information. The user information area 4 is formed in this order.

  FIG. 2 shows a schematic diagram of the substrate shapes of the BCA2, the management information area 3, and the user information area 4 of the optical information recording medium of the present invention. In the present embodiment, as shown in FIG. 2, the BCA 2 is composed of any one of the groove 5, the embossed pit row 6, and the concavo-convex pattern 7 including the groove 7a and the embossed pit row 7b formed between the grooves. Is done. Although FIG. 2 shows an example of the concavo-convex pattern formed on the BCA 2 of the optical information recording medium of the present invention, it is not limited to this. For example, the concave / convex patterns 5, 6, and 7 of BCA2 may be wobbled at a specific frequency. 2 shows a pattern in which embossed pits having the same shape are arranged at equal intervals along the track direction, the above formulas (3) or (4) and (5) or (6) Any embossed pit row pattern can be used as long as it satisfies the following conditions. For example, as shown in FIG. 11, an emboss such that a part of the emboss pit of a track adjacent to the predetermined track is formed in a region between the emboss pits adjacent to each other in the circumferential direction of the emboss pit row formed in the predetermined track. A pit row pattern, that is, an emboss pit row pattern in which emboss pit rows overlap in the circumferential direction between adjacent tracks may be used.

  As shown in FIG. 2, the management information area 3 is formed with embossed pits 8 indicating management information, and the user information area 4 is formed with grooves 9 in which pits are formed during information recording. Further, the groove 9 in the user information area 4 may be wobbled at a specific frequency or may include pits in order to give address information. The pits or grooves in each region are formed in a spiral shape or a concentric shape.

[BCA structure]
Here, the configuration of the BCA 2 of the optical information recording medium of the present embodiment will be described in more detail with reference to FIGS.

  The depth of the grooves and / or embossed pits formed in BCA2 can be arbitrarily set depending on the specification, film configuration, etc., but usually a depth of 30 to 120 nm is preferable, and more preferably 50 to 100 nm. The depth is preferred. This is a preferred depth for ensuring good groove signal characteristics and recording characteristics for the user area, but the same effect can be obtained even if this depth range is applied to BCA2. That is, the depth range is also an optimum depth range for setting the film thickness of the dye material on BCA2 to a film thickness necessary for obtaining good signal characteristics from BCA2.

In the case where the concave / convex pattern of BCA2 is formed only by grooves (the left figure in FIG. 3), the following relational expression is established when the width 40 between the grooves (land portions) 5a is LW1.
(LW1 × NA) /λ≦0.3 (2)
Here, λ is the wavelength of the recording / reproducing laser of the optical disk drive, and NA is the numerical aperture of the objective lens of the recording / reproducing pickup. Here, as shown in the left diagram of FIG. 3, LW1 is the half-value width between the claws (land portions) 5a.

When the concave / convex pattern of BCA2 is formed only by embossed pit rows (center view in FIG. 3), if the width 43 between the embossed pit rows 6 is LW2, the following relational expression is established.
(LW2 × NA) /λ≦0.3 (3)
Here, the width LW2 between the embossed pit rows 6 is the pits facing each other in the radial direction of the track (left and right in the drawing) between the adjacent embossed pit rows 6 as shown in the central view of FIG. The distance between the extreme ends.

Further, when the concave / convex pattern of BCA2 is formed by grooves and embossed pit rows provided between the grooves (the right diagram in FIG. 3), the embossed pit rows 7b and the grooves 7a located on both sides thereof are arranged. If the wider one of the widths 45 is LW3, the following relational expression is established.
(LW3 × NA) /λ≦0.3 (4)
Here, as shown in the right diagram in FIG. 3, LW3 is defined as 1 / groove of the groove depth of the side wall of the groove 7 a facing the most end portion from the radial end portion of the embossed pit row 7 b. It was set as the distance to the position where the depth was two.

  As described above, since the concave / convex pattern is formed on the BCA 2 in the optical information recording medium of the present embodiment, recording is performed by applying a dye material with a film thickness that optimizes the recording characteristics of the user information area by spin coating. Even when the layer is formed, since the dye material is accumulated in the groove portion and the embossed pit portion of the BCA2, the film thickness of the recording layer on the BCA2 becomes sufficiently thick. Further, since the dye film thickness of the land portion other than the groove portion and the embossed pit portion of the BCA2 is thin, sufficient BCA signal characteristics cannot be obtained from this land portion. However, in the optical information recording medium of the present embodiment, the BCA2 Since the concavo-convex pattern is formed so as to satisfy any of the above formulas (2) to (4), the land area is larger than the optical resolution λ / (2 · NA) of the optical disc drive used for recording and reproduction. The size becomes smaller and completely indistinguishable. In this case, when the reproduction laser is irradiated to the BCA2 without tracking, the reproduction laser is irradiated across the track portion and the land portion of the BCA2 due to the eccentricity of the medium, but the area of the land portion is smaller than the optical resolution. Therefore, a reproduction signal obtained by averaging the reproduction signal of the land portion where the signal amplitude is hardly obtained and the reproduction signal of the groove portion and the emboss pit portion where a sufficient signal amplitude is obtained can be obtained from the BCA. Therefore, the amplitude variation of the BCA reproduction signal is suppressed by forming the concavo-convex pattern of the BCA2 so as to satisfy any of the above formulas (2) to (4) as in the optical information recording medium of the present embodiment. Therefore, it is possible to obtain a BCA reproduction signal amplitude modulation degree that is satisfactory for reproduction, that is, good BCA reproduction characteristics. In this case, the BCA reproduction signal is in accordance with the ratio of the area where the BCA reproduction signal is hardly obtained (land part) and the area where the BCA reproduction signal is obtained with sufficient intensity (groove part and / or embossed pit row part). Since it is averaged, it is preferable to increase the ratio of the width of the groove portion or the embossed pit portion to the width of the land portion.

  In the optical information recording medium of the present embodiment, the track pitch 42 (TP) of BCA2 is made smaller than the track pitch (TPy) of the user information area in any of the concave / convex patterns of BCA2 shown in FIG. Satisfying the above formula (1)) is preferable.

Further, in the optical information recording medium of the present embodiment, the track pitch 42 (TP) of BCA2, the recording / reproducing laser wavelength λ of the optical disc driving device, and the numerical aperture of the objective lens of the recording / reproducing pickup are NA.
(TP × NA) /λ≦0.6 (5)
It is preferable to set the track pitch 42 (TP) of BCA2 so that the above relationship is satisfied, and more desirably 0.45 ≦ (TP × NA) /λ≦0.6 (6)
It is preferable to set the track pitch 42 (TP) of BCA2 so that the above relationship is established. That is, it is preferable that the track pitch TP of BCA2 is made as small as possible so as to be closer to the optical resolution λ / (2 · NA) of the optical disk drive used for recording and reproduction, or less than the optical resolution. If (TP × NA) / λ is 0.5 or less, the track of BCA2 is completely smaller than the optical resolution.

  By setting the track pitch TP of BCA2 so as to satisfy the relationship of the above expression (5) or (6), even if the tracking is removed and the BCA information is reproduced, the influence of the amplitude variation of the reproduced signal due to the cross track signal Can be reduced. That is, by making the track pitch TP of BCA2 close to the optical resolution or less than or equal to the optical resolution, the concave / convex pattern of BCA2 looks the same as the mirror portion when viewed from the optical disk drive (reproducing beam) side, Only the contrast of the BCA information is reproduced as a signal.

  Further, as shown in the equation (6), when (TP × NA) / λ is set to 0.45 or more, the management information area and Grooves and embossed pits can be produced in the BCA2 using the same exposure apparatus (that is, the same laser) as the exposure apparatus used to form grooves and embossed pits in the user information area. improves.

  The range of the track pitch TP of BCA2 that satisfies the above expression (5) or (6) will be described more specifically. For example, a laser with a wavelength of 405 nm and an objective lens with a numerical aperture NA of 0.65 are used for recording and reproducing information. When the LW1, LW2, and LW3 of the concavo-convex pattern of BCA2 shown in FIG. 3 are all set to about 187 nm or less, a reproduction signal amplitude modulation degree that does not cause a problem in reproducing the BCA2 information can be obtained. Can do. Furthermore, if the track pitch TP of BCA2 is set to about 374 nm or less, the amplitude fluctuation due to the cross track signal can be reduced to a level that does not substantially affect. Further, by setting the track pitch TP of BCA2 to 280 nm or more, the BCA, the management information area, and the user data area can all be produced by the same exposure apparatus, so that productivity is dramatically improved.

  From the viewpoint of reducing the amplitude fluctuation of the BCA reproduction signal due to the influence of the eccentricity of the optical information recording medium (the influence of the cross track signal), the distance between the grooves of BCA2 shown in the above equations (2) to (5), respectively. The width LW1, the width LW2 between the embossed pit rows, the width LW3 between the embossed pit row and the groove, and the track pitch TP ((TP × NA) / λ) are desirably made as small as possible. However, the lower limits of these widths and track pitches have manufacturing limitations. With the current technology, the track pitch TP is about 200 nm, and the width limit between grooves or embossed pit rows Although it varies slightly depending on the depth of the embossed pit, the average is about 100 nm.

In addition, for the uneven pattern having the embossed pits (the uneven pattern in the center and right figures in FIG. 3), the pit length 46 (PL) of the embossed pits, the pit interval length 47 (SL), and the optical disk drive device Between the recording / reproducing laser wavelength λ and the numerical aperture NA of the objective lens of the recording / reproducing pickup,
(PL × NA) /λ≦0.6
(SL × NA) /λ≦0.6
It is preferable that the relationship is satisfied, and more desirably, (PL × NA) /λ≦0.5
(SL × NA) /λ≦0.5
Is preferably established. When a concavo-convex pattern having embossed pits is formed so as to establish such a relationship, the optical resolution λ / of an optical disc drive using the pit length 46 (PL) and the pit interval length 47 (SL) of the embossed pits for recording / reproduction. (2 · NA), or less than that, even if these concavo-convex patterns are irradiated with the recording / reproducing laser, the embossed pits and the embossed pits are not recognized. Since it looks similar, it is difficult to adversely influence the reproduction signal of the BCA such as amplitude fluctuation.

  As described above, it was found that the following BCA reproduction signal characteristics can be obtained by forming the concave / convex pattern of BCA so that the relational expressions (1) to (6) are satisfied (FIG. 4 also). reference). Details of the reproduction signal characteristics of the following BCA will be described in an embodiment described later.

[1] The minimum amplitude Imin of the BCA reproduction signal can be made larger than the amplitude CT of the cross track signal, and BCA information can be reproduced more accurately.

[2] The degree of modulation (RH-RL) / RH at the minimum amplitude of the BCA reproduction signal is 0.2 or more, and a BCA reproduction signal with good signal quality can be obtained.

[3] When the concave / convex pattern of the BCA is formed only by the groove, when the BCA information is reproduced by irradiating the reproduction beam to the BCA without performing tracking, the spot center of the reproduction beam is positioned at the center of the groove 5. Sometimes (the state of circles 30 and 32 in the left diagram of FIG. 4), the level difference ΔIg (amplitude of the BCA reproduction signal) of the reproduction signal level obtained from the unrecorded part 28 and the recording part 29 of the BCA, and the spot of the reproduction beam When the center is located at the center between the grooves (the state of circles 31 and 33 in the left diagram of FIG. 4), the level difference Δl1 (BCA playback signal) of the playback signal level obtained from the unrecorded portion 28 and the recorded portion 29 of BCA, respectively. Amplitude)
When ΔIg ≧ ΔIl1, ΔIg / ΔIl1 ≦ 1.4
If ΔIl1 ≧ ΔIg, then ΔIl1 / ΔIg ≦ 1.4
A reproduction signal that satisfies this relationship can be obtained. That is, by forming a groove in the BCA so as to satisfy the above equation (2), it is possible to obtain a reproduction signal with very small amplitude fluctuation from the BCA. In the above relational expression, the magnitude differences of the level differences ΔIg and ΔIl1 are classified according to the case. However, depending on the dye material forming the recording layer, the magnitude relationship between the reflectance of the unrecorded portion and the reflectance of the recording portion. This is because the magnitude relationship between the level differences ΔIg and ΔIl1 also changes.

[4] When the concave / convex pattern of the BCA is formed only by the embossed pit row, when the BCA information is reproduced by irradiating the reproduction beam to the BCA without performing tracking, the spot center of the reproduced beam is the center of the embossed pit row. 4 (the state of circles 35 and 37 in the center of FIG. 4), the level difference ΔIp of the reproduced signal level obtained from the unrecorded part 28 and the recorded part 29 of the BCA and the spot center of the reproduced beam are embossed pits. Between the level difference ΔIo of the reproduction signal level obtained from the unrecorded part 28 and the recorded part 29 of the BCA when positioned in the middle between the columns (the state of the circles 34 and 36 in the central diagram of FIG. 4),
When ΔIp ≧ ΔIo, ΔIp / ΔIo ≦ 1.4
If ΔIo ≧ ΔIp, ΔIo / ΔIp ≦ 1.4
A reproduction signal that satisfies this relationship can be obtained. That is, by forming an embossed pit row in the BCA so as to satisfy the above expression (3), a reproduction signal with very small amplitude fluctuation can be obtained from the BCA.

[5] When the concave / convex pattern of the BCA is formed by the grooves and the embossed pit rows provided between the grooves, when the BCA information is reproduced by irradiating the BCA with the reproduction beam without tracking, the reproduction beam When the spot center is located in the center of the groove (the state of circles 30 and 32 in the right figure of FIG. 4), the reproduction signal level level difference ΔIg obtained from the unrecorded part 28 and the recorded part 29 of the BCA, and the reproduction Reproduction signal levels obtained from the unrecorded part 28 and the recorded part 29 of the BCA when the spot center of the beam is located at the center between the groove and the embossed pit row (in the state of circles 38 and 39 in the right diagram of FIG. 4) Level difference ΔIl2 of
If ΔIg ≧ ΔIl2, ΔIg / ΔIl2 ≦ 1.4
When ΔIl2 ≧ ΔIg, ΔIl2 / ΔIg ≦ 1.4
A reproduction signal that satisfies this relationship can be obtained. That is, by forming grooves and embossed pit rows in the BCA so as to satisfy the above expression (4), it is possible to obtain a reproduction signal with very small amplitude fluctuation from the BCA.

[Film structure of optical information recording medium]
The film configuration of the optical information recording medium of this embodiment will be described. A schematic sectional view of the optical information recording medium 1 is shown in FIG. As shown in FIG. 5, the optical information recording medium 1 of the present embodiment has a light absorbing layer 11 (recording layer), a reflective layer 12, an adhesive layer 13, and a dummy on a translucent substrate 10 having pits and grooves. The substrate 14 has a structure formed in this order. The recording layer 11 is a layer that absorbs the irradiated laser light to generate heat, melts, evaporates, sublimates, deforms or denatures, and has a function of forming pits on the surface of the recording layer 11 or the substrate 10. Further, an enhancement layer or a solvent resistant layer made of SiO ₂ , ZnS—SiO ₂ or the like may be provided between the substrate 10 and the recording layer 11.

  The substrate 10 is preferably produced by producing an original disk and a stamper and performing injection molding. In this embodiment, the master was produced as follows. First, a glass master having a diameter of 200 mm and a thickness of 6 mm was prepared, and a photoresist was uniformly applied on one surface of the glass master using a spin coating method. The thickness of the photoresist was adjusted according to the depth of pits (embossed pits) or grooves. Next, the glass master on which the photoresist was formed was mounted on a cutting apparatus.

  A cutting device for producing a master is shown in FIG. The recording optical head 22 is driven by a servo system that moves in the radial direction of the master 15 relative to the master 15 (not shown). The recording radius position is monitored by a linear scale 21 and controlled by a closed servo loop. The formatter 19 generates information data, management information, a groove signal, and the like, and the recording optical head 22 is driven by the generated signal. The entire system of the cutting apparatus is managed by the controller 18, and the track pitch is servo-controlled by the controller 18. The master disk is driven to rotate by a spindle 16 and forms a unique servo loop. The spindle 16 is driven by a spindle driver 17.

  After the glass master is mounted on the cutting device, exposure is performed by irradiating the photoresist on the glass master 15 with laser light from the optical head 22 in accordance with the information sent from the formatter 19, and exposure corresponding to the pit or groove shape. A pattern was formed. The exposure pattern corresponding to the pit size and groove width was controlled by adjusting the amount of laser light. After the cutting was completed, the glass master was subjected to a known development process, and pits or groove patterns corresponding to the exposure pattern were formed on the photoresist. Next, electroless plating was applied to the pattern forming surface of the glass master 15 as a pretreatment for plating. Furthermore, using this plating layer as a conductive film, a Ni layer was formed on the glass master 15 by electroforming. Next, the surface of the Ni layer formed on the glass master 15 was polished, and the Ni layer was peeled from the glass master to obtain a stamper. Note that a sputtering method or a vapor deposition method may be used as a method for forming the conductive film in the pretreatment for plating.

  In this embodiment, the board | substrate 10 was produced by injection molding using the stamper produced by the said method. As a material of the translucent substrate 10, a resin having a high transparency with a refractive index with respect to a laser beam in a range of 1.4 to 1.6 and an excellent impact resistance is desirable. Specific examples include polycarbonate, amorphous polyolefin, and acrylic, but are not limited thereto.

  As a material for the recording layer 11 (light absorption layer), a light-absorbing organic dye is desirable. Specifically, a cyanine dye, polymethine dye, triarylmethane dye, pyrylium dye, phenanthrene dye, azo dye, tetradehydro Choline dyes, triarylamine dyes, squarylium dyes, croconic methine dyes and the like can be used. However, the present invention is not limited to this. The recording layer 11 may contain other dyes, additives, polymers (for example, thermoplastic resins such as nitrocellulose, thermoplastic elastomers), metal fine particles, and the like.

  The recording layer 11 is obtained by dissolving and solvating the above-mentioned dye and any additive in a known organic solvent (for example, tetrafluoropropanol, ketone alcohol, acetylacetone, methylcellulob, toluene, etc.) on the light-transmitting substrate 10. It is formed by coating. As a means for forming the recording layer 11, a spin coating method is used. In this method, the film thickness of the recording layer can be controlled by adjusting the concentration, viscosity, and solvent drying speed of the dye solution.

The reflective layer 12 is made of a metal film, and is formed of, for example, gold, silver, aluminum, or an alloy containing these by means such as sputtering. Note that another layer such as an enhancement layer or an oxidation-resistant layer made of SiO ₂ , ZnS—SiO ₂ , Al ₂ O ₃ or the like may be provided between the recording layer and the reflective layer. Further, a protective layer may be formed on the reflective layer 12, or a protective layer may not be formed. Any material can be used as the protective layer as long as it can protect the recording layer and the reflective layer. For example, an ultraviolet curable resin, a silicone-based resin, or the like can be used.

  The adhesive layer 13 is desirably formed of a resin having excellent impact resistance. For example, it is preferably formed by applying an ultraviolet curable resin by a spin coating method and irradiating and curing the ultraviolet ray. Further, the adhesive layer 13 may be formed of an elastic material such as urethane. In this case, the recording layer may be provided on both of the substrates to be bonded, or one of the substrates may be a dummy substrate having no recording layer. If necessary, a print layer or a print receiving layer may be provided on the surface of the substrate on the dummy substrate side.

  Recording on the optical information recording medium 1 of the present embodiment is performed by irradiating a recording layer provided on both sides or one side of the medium with laser light. In the portion irradiated with the laser beam, thermal changes of the substrate such as decomposition of the dye, heat generation, carbonization, melting of the substrate, deformation due to absorption of laser beam energy occur. The recorded information is reproduced by reading the difference in reflectance between the portion where the thermal change has occurred and the portion where the thermal change has not occurred with the laser beam.

  In the above embodiment, an example of an optical information recording medium that records and reproduces by irradiating a recording layer with a laser beam through a substrate has been described, but the present invention is not limited to this. The present invention is also applicable to an optical information recording medium that records and reproduces a recording layer made of a dye material from the film surface side by irradiating the recording layer with a laser beam. Further, the present invention is applicable to any optical information recording medium in which the light absorption layer is formed by a spin coating method and has the above-described BCA and user information area.

  As a laser of the driving device used for recording / reproducing of the optical information recording medium of the present embodiment, it is preferable to use a blue laser having a wavelength of 390 nm to 430 nm, and more preferably, a blue laser having a wavelength of 400 to 420 nm is used. . Moreover, as a laser used for a BCA writer, a red laser with a wavelength of 620 nm to 720 nm is preferable, and a red laser with a wavelength of 650 to 700 nm is more preferable. However, the wavelength of the BCA writer is not limited to this width.

  Hereinafter, the configuration of the optical information recording medium according to the present embodiment, the characteristics of the BCA reproduction signal, and the like will be described more specifically with reference to examples.

[Production of optical information recording medium]
First, the stamper produced by the above manufacturing method was mounted on an existing injection molding machine, and an optical information recording medium grade polycarbonate resin was injection molded to produce a substrate 10. The substrate 10 is a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm. As shown in FIG. 1, the BCA formed in the glass master, the management information area, and the spiral groove of the user information area and / or Alternatively, a concavo-convex pattern of pits (embossed pits) is transferred onto one surface of the substrate 10. In this example, the BCA was formed in an area having a radius of 22.20 mm to 23.20 mm. In BCA, a straight (not wobbled) groove having a track pitch of 350 nm, a groove width of 240 nm, and a groove depth of 70 nm was formed. The management information area was formed in an area having a radius of 23.40 mm to 23.80 mm. In the management information area, pits having a track pitch of 680 nm, a pit width of 200 nm, and a pit depth of 70 nm were formed. The user information area was formed in an area having a radius of 23.80 mm to 58.50 mm. In the user information area, a wobble groove modulated with a track pitch of 400 nm, a groove width of 210 nm, a groove depth of 70 nm and a frequency of 700 kHz was formed. Since the pits and grooves are formed in a spiral shape, these radii have a positional relationship at a specific angle of the optical information recording medium.

  Next, a tetrafluoropropanol solution having a concentration of 0.7% by weight of an azo dye represented by the following chemical formula (1) was applied to the uneven pattern forming surface of the substrate 10 by spin coating. In addition, when apply | coating the said pigment | dye solution, the pigment | dye solution was filtered with the filter and the impurity was removed. In the spin coating, 0.5 g of the dye solution was supplied by a dispenser onto the substrate 10 rotating at a rotation speed of 100 rpm, and then the substrate was rotated from 1000 rpm to 3000 rpm, and finally rotated at 5000 rpm for 2 seconds. At this time, the solution was applied so that the groove portion had a thickness of 60 nm. Next, the substrate 10 coated with the coloring material was dried at 80 ° C. for 1 hour, and further cooled at room temperature for 1 hour. Thus, the recording layer 11 (light absorption layer) was formed on the substrate 10.

  Next, an Ag alloy film was formed as a reflective layer 12 on the recording layer 11 so as to have a thickness of 130 nm using a sputtering method. Next, a UV resin material was applied as the adhesive layer 13 on the reflective layer 12 by a spin coating method, and a polycarbonate substrate having a thickness of 0.6 mm was placed thereon as the dummy substrate 14. In this state, the adhesive layer 13 is cured by UV irradiation from the dummy substrate 14 side, whereby the substrate 10 on which each layer is formed and the dummy substrate 14 are bonded to each other to form the optical information recording medium (optical information recording medium) of Example 1. Medium A) was obtained.

  The optical information recording medium A manufactured in Example 1 has a recording film configuration in which the reflection level (reflectance) after recording is higher than the reflection level before recording. However, the present invention is not limited to this, and the recording film may be configured such that the reflection level after recording is lower than the reflection level before recording. In this case, the same effect can be obtained.

  In this embodiment, the concave / convex pattern made of a straight groove is formed on the BCA. However, the concave / convex pattern of the BCA may be formed using a wobbled groove, and the same effect can be obtained in this case.

[Comparative Example 1]
In Comparative Example 1, the concave / convex pattern of BCA was formed with grooves, the track pitch was 400 nm, the groove width of the groove was 210 nm, and the groove depth was 70 nm. That is, a groove having the same dimensions as the user information area was formed. An optical information recording medium B was produced in the same manner as in Example 1 except that the dimensions of the BCA groove were changed.

[Recording and playback characteristics of BCA information]
BCA information was recorded on the optical information recording media A and B produced in Example 1 and Comparative Example 1 as follows. In order to record a BCA signal at a position of a radius of 22.20 mm to 23.20 mm on an optical information recording medium, a BCA lighter having a laser wavelength of 668 nm and a beam diameter of about 1 μm × about 48 μm is used to record the BCA signal. It was. The BCA code was recorded under the conditions of laser power 900 mW, linear velocity 5 m / s, radial beam feed amount 8 μm, recording start position 22.1 mm, and recording end position 23.3 mm.

  Next, for each of the optical information recording media of Example 1 and Comparative Example 1 on which the BCA code was recorded, the tester was equipped with an optical pickup having a laser beam having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.65. The BCA information was reproduced with the tracking removed. A photograph of the reproduced signal waveform is shown in FIG.

  The left photograph in FIG. 7 is a BCA reproduction signal waveform in the optical information recording medium A of the first embodiment. The waveform photograph on the lower left is a waveform photograph obtained by enlarging the horizontal axis (time axis) of the waveform photograph on the left middle. The upper left waveform photograph is a waveform photograph in which the vertical axis (voltage axis) of the left middle waveform photograph is enlarged, and shows the relationship between the BCA reproduction signal and the cross track signal. On the other hand, the right-side waveform photograph in FIG. 7 is a BCA reproduction signal waveform in the optical information recording medium B of Comparative Example 1. The upper right waveform photograph is a waveform photograph in which the vertical axis of the right middle waveform photograph is enlarged, and shows the relationship between the BCA reproduction signal and the cross track signal.

  A waveform 20 in the upper photograph on the left and right sides in FIG. 7 is a BCA reproduction signal waveform. The lower peak level of the waveform 20 is the signal level (hereinafter also referred to as the Low level) in the BCA unrecorded portion, and the upper peak level of the waveform 20 is the signal level (hereinafter referred to as the High level) in the BCA recording portion. It is also called). In addition, waveforms 23 and 24 in the upper left photograph and the right upper photograph in FIG. 7 (thick broken line waveforms in the left and right upper photographs in FIG. 7) indicate the fluctuations in the Low and High levels of the waveform 20, respectively. It represents the influence of the cross track signal. That is, the waveform 23 shows the fluctuation of the reproduction signal level due to the influence of the cross track signal in the BCA non-recorded portion, and the waveform 24 shows the fluctuation of the BCA reproduction signal level due to the influence of the cross track signal in the BCA recording portion. Show.

  As apparent from the waveform photograph of the BCA reproduction signal in FIG. 7, in Comparative Example 1, the amplitude fluctuation of the BCA reproduction signal waveform 20 increases due to the influence of the cross track signal, and the amplitude of the cross track signal in the unrecorded portion of the BCA. 26 (a fluctuation amount of the unrecorded level of the BCA reproduction signal) is larger than the minimum amplitude 25 of the BCA reproduction signal waveform 20. It is difficult to accurately reproduce the BCA information from the BCA reproduction signal waveform 20 having a large amplitude fluctuation. On the other hand, in the optical information recording medium of Example 1, it was found that both the amplitudes 26 and 27 of the cross track signal were much smaller than the minimum amplitude 25 of the BCA reproduction signal waveform 20.

From the photograph of the BCA reproduction signal waveform shown in FIG. 7, the minimum amplitude 25 of the BCA reproduction signal of the optical information recording medium of Example 1 and Comparative Example 1, the amplitude 26 of the cross track signal in the unrecorded portion of the BCA, and the BCA recording The degree of modulation of the cross track signal at amplitude 27 and the minimum amplitude of the BCA reproduction signal were measured. The results are summarized in Table 1. The modulation degree of the BCA reproduction signal is usually (RH-RL), where the higher reflectance RH and the lower reflectance RL of the reflectance of the BCA recording part and the reflectance of the unrecorded part are given. Here, the modulation degree of the BCA reproduction signal is obtained from the level difference at the minimum amplitude of the BCA reproduction signal instead of the reflectance. Specifically, the High level and the Low level at the minimum amplitude of the BCA reproduction signal are set to RH and RL, respectively, and (RH−RL) / RH is calculated and the value is set as the modulation degree at the minimum amplitude of the BCA reproduction signal. The modulation degree obtained in this way is substantially the same value as the modulation degree obtained from the difference in reflectance. The correspondence between the parameters in Table 1 and the measurement items is as follows.
TP: Track pitch RH: High level at minimum amplitude of BCA playback signal RL: Low level at minimum amplitude of BCA playback signal RH-RL: Minimum amplitude of BCA playback signal (amplitude amount 25 in FIG. 7)
Ictu: Amplitude of cross track signal in unrecorded portion of BCA (Low level fluctuation amount 26 in FIG. 7)
Ictw: Amplitude of cross track signal in BCA recording section (high level variation 27 in FIG. 7)
(RH-RL) / RH: Modulation degree at minimum amplitude of BCA reproduction signal

  As is clear from Table 1, in the optical information recording medium A of Example 1, the minimum amplitude of the BCA reproduction signal (RH-RL in Table 1) is larger than the amplitude of the cross track signal (Ictw and Itu in Table 1). And the degree of modulation ((RH-RL) / RH in Table 1) exceeded 20%. In addition, it was found that the optical information recording medium A of Example 1 has a smaller amplitude fluctuation of the BCA reproduction signal than that of Comparative Example 1, and a BCA reproduction signal with good signal quality can be obtained. On the other hand, in the optical information recording medium B of Comparative Example 1 in which the track pitch of the BCA is the same as the track pitch of the user information area, the minimum amplitude of the BCA reproduction signal is smaller than the amplitude of the cross track signal, and the modulation degree Was less than 20%. Further, in the optical information recording medium of Comparative Example 1, the amplitude fluctuation of the BCA reproduction signal was large and the signal quality was deteriorated. That is, as in Example 1, it was found that by making the track pitch TP of the concave / convex pattern of BCA smaller than the track pitch TPy of the user information area, a BCA reproduction signal with small amplitude fluctuation and high modulation degree can be obtained. .

  In Example 2, the concave / convex pattern of BCA was formed by grooves, the track pitch was 370 nm, the groove width of the grooves was 250 nm, the width between grooves was 120 nm, and the groove depth was 70 nm. An optical information recording medium C was produced in the same manner as in Example 1 except that the BCA groove dimensions were changed.

  In Example 3, the concave / convex pattern of BCA was formed by a groove, the track pitch was 370 nm, the groove width of the groove was 220 nm, the width between the grooves was 150 nm, and the groove depth was 70 nm. An optical information recording medium D was produced in the same manner as in Example 1 except that the dimensions of the BCA groove were changed.

  In Example 4, the concave / convex pattern of BCA was formed by a groove, the track pitch was 370 nm, the groove width of the groove was 190 nm, the width between the grooves was 180 nm, and the groove depth was 70 nm. An optical information recording medium E was produced in the same manner as in Example 1 except that the BCA groove dimensions were changed.

  In Example 5, an uneven pattern of BCA is formed by embossed pit rows, the track pitch is 370 nm, the pit width of the embossed pit rows is 190 nm, the width between pit rows is 180 nm, the pit length is 250 nm, and the pit interval is 150 nm. The pit depth was set to 70 nm. An optical information recording medium F was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

  In Example 6, the concave / convex pattern of BCA was formed by grooves and embossed pit rows provided between the grooves, and the track pitch was 370 nm. The groove width of the groove was 100 nm, and the groove depth was 70 nm. The emboss pit row had a pit width of 60 nm, a pit length of 300 nm, a pit interval of 100 nm, and a pit depth of 70 nm. The widths between the embossed pit rows and the grooves located on both sides thereof were 180 nm and 30 nm, respectively. An optical information recording medium G was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Comparative Example 2]
In Comparative Example 2, the concave / convex pattern of BCA was formed by grooves, the track pitch was 370 nm, the groove width of the grooves was 180 nm, the width between the grooves was 190 nm, and the groove depth was 70 nm. An optical information recording medium H was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Comparative Example 3]
In Comparative Example 3, the concave / convex pattern of BCA was formed by grooves, the track pitch was 370 nm, the groove width of the grooves was 150 nm, the width between the grooves was 220 nm, and the groove depth was 70 nm. An optical information recording medium I was prepared in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Comparative Example 4]
In Comparative Example 4, an uneven pattern of BCA is formed with embossed pit rows, the track pitch is 370 nm, the pit width of the embossed pit rows is 180 nm, the width between pit rows is 190 nm, the pit length is 300 nm, and the pit interval is 100 nm. The pit depth was set to 70 nm. An optical information recording medium J was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Comparative Example 5]
In Comparative Example 5, the concave / convex pattern of BCA was formed with grooves and embossed pit rows provided between the grooves, and the track pitch was 370 nm. The groove width of the groove was 100 nm, and the groove depth was 70 nm. The embossed pit row had a pit width of 60 nm, a pit length of 250 nm, a pit interval of 150 nm, and a pit depth of 70 nm. The widths between the embossed pit rows and the grooves located on both sides thereof were 190 nm and 20 nm, respectively. An optical information recording medium K was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Recording and playback characteristics of BCA information]
The BCA code was recorded on the BCA in the same manner as in Example 1 for the optical information recording media manufactured in Examples 2-6 and Comparative Examples 2-5. Then, in the same manner as in Example 1, the BCA information of each optical information recording medium is obtained with the focus removed from the tracking with a tester including a laser beam having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.65. Reproduction was performed, and the modulation degree of the minimum amplitude of the BCA reproduction signal was measured. The results are shown in Tables 2 and 3. The meaning of each parameter in Tables 2 and 3 is as follows.
TP: BCA track pitch LW1: BCA groove width LW2: BCA emboss pit row width LW3: BCA emboss pit row and the width of the groove on both sides NA: Tester Λ: Tester laser wavelength RH: High level at minimum amplitude of BCA playback signal RL: Low level of minimum amplitude of BCA playback signal (RH-RL) / RH: Modulation degree at minimum amplitude of BCA playback signal

  From the results of Tables 2 and 3, the relationship between (LW1 × NA) / λ, (LW2 × NA) / λ and (LW3 × NA) / λ and the modulation factor (RH−RL) / RH is shown in FIG. . In FIG. 8, the horizontal axis represents (LW1 × NA) / λ, (LW2 × NA) / λ, or (LW3 × NA) / λ, and the vertical axis represents the degree of modulation (RH−RL) / RH. When the BCA is formed with a concave / convex pattern made of grooves, as is clear from FIG. 8, as (LW1 × NA) / λ increases, that is, the width LW1 between the grooves (land portions) increases and linearly modulates. Degree (RH-RL) / RH becomes small. Then, it was found that by setting (LW1 × NA) / λ to 0.3 or less, the modulation degree of the minimum amplitude of the BCA reproduction signal exceeds 20%, and the signal quality is improved. Also, when the BCA is formed with an embossed pit row or a concavo-convex pattern composed of a groove and an embossed pit row, the same characteristics as (LW1 × NA) / λ are obtained as shown in FIG. It was found that when LW2 × NA) / λ or (LW3 × NA) / λ is 0.3 or less, the modulation degree of the minimum amplitude of the BCA reproduction signal exceeds 20%. In the present invention, 20% is used as the reference for the superiority or inferiority of the modulation degree, for the following reason. As will be described later, when the concave / convex pattern of the BCA is formed so that the modulation degree of the minimum amplitude of the BCA reproduction signal exceeds 20%, the modulation degree of the minimum amplitude of the BCA reproduction signal becomes larger than the modulation degree of the cross track signal. Since the BCA information can be reliably reproduced (see FIG. 9), 20% is used here as a reference for the superiority or inferiority of the modulation degree.

  In Example 7, the concave / convex pattern of BCA was formed by grooves, the track pitch was 310 nm, the groove width of the grooves was 200 nm, the width between grooves was 110 nm, and the groove depth was 70 nm. An optical information recording medium L was produced in the same manner as in Example 1 except that the dimensions of the BCA groove were changed.

  In Example 8, the concave / convex pattern of BCA was formed by a groove, the track pitch was 280 nm, the groove width of the groove was 200 nm, the width between the grooves was 80 nm, and the groove depth was 70 nm. An optical information recording medium M was produced in the same manner as in Example 1 except that the BCA groove dimensions were changed.

[Comparative Example 6]
In Comparative Example 6, the concave / convex pattern of BCA was formed by grooves, the track pitch was 385 nm, the groove width of the grooves was 190 nm, the width between grooves was 195 nm, and the groove depth was 70 nm. An optical information recording medium N was produced in the same manner as in Example 1 except that the dimensions of the BCA groove were changed.

[Comparative Example 7]
In Comparative Example 7, the concave / convex pattern of BCA was formed of grooves, the track pitch was 425 nm, the groove width of the grooves was 210 nm, the width between grooves was 215 nm, and the groove depth was 70 nm. Other than that was carried out similarly to Example 1, and produced the optical information recording medium O. FIG.

[Recording and playback characteristics of BCA information]
The BCA codes were recorded on the BCA in the same manner as in Example 1 for the optical information recording media manufactured in Examples 7 and 8 and Comparative Examples 6 and 7. Then, in the same manner as in Example 1, the BCA information of each optical information recording medium is obtained with the focus removed from the tracking with a tester including a laser beam having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.65. The minimum amplitude of the BCA reproduction signal and its modulation degree, and the maximum amplitude of the cross track signal (the larger amplitude fluctuation amount of the BCA reproduction signal waveform Low level and High level amplitude) and its modulation degree are reproduced. It was measured.

Also, the reproduction signal level when the spot center of the reproduction beam of the tester is irradiated to the center of the groove of the unrecorded portion of BCA (the state of the circle 30 in the left diagram in FIG. 4) and the groove of the recording portion of the BCA The difference from the reproduction signal level (amplitude of the BCA reproduction signal) when irradiating the center (the state of the circle 32 in the left diagram in FIG. 4) and the spot center of the reproduction beam of the tester are recorded in the BCA unrecorded portion. When the light is irradiated to the center between the grooves (the state of the circle 31 in the left diagram in FIG. 4) and when the light is irradiated to the center between the grooves of the BCA recording portion (left in FIG. 4) The difference in reproduction signal level (amplitude of BCA reproduction signal) in the state of circle 33 in the figure was also measured. The above measurement results are shown in Table 4. In Table 4, the measurement results of Examples 1 and 2 and Comparative Example 1 are also shown. The meaning of each parameter in Table 4 is as follows.
TP: BCA track pitch NA: Tester lens numerical aperture λ: Tester laser wavelength RH: High level at minimum amplitude of BCA playback signal RL: Low level at minimum amplitude of BCA playback signal (RH-RL) / RH: BCA Modulation degree at the minimum amplitude of the reproduction signal Ict: Maximum amplitude of the cross track signal Ict / RH: Modulation degree at the maximum amplitude of the cross track signal ΔIg: BCA when the spot center of the reproduction beam is irradiated to the center of the groove of the BCA Amplitude of reproduction signal ΔIl1: Amplitude of BCA reproduction signal when spot center of reproduction beam is irradiated to the center between BCA grooves

  From the results shown in Table 4, FIG. 9 shows the relationship between (TP × NA) / λ, modulation degree (RH−RL) / RH, and Ict / RH when the concave / convex pattern of BCA is formed by grooves. In FIG. 9, the horizontal axis represents (TP × NA) / λ, and the vertical axis represents the degree of modulation (RH-RL) / RH or Ict / RH. The optical information recording media of the examples and comparative examples shown in Table 4 have different reflectivities, and in FIG. 9, values normalized by the high level (RH) at the minimum amplitude of the BCA reproduction signal are plotted.

  When the BCA is formed with a concave / convex pattern made of grooves, as is clear from Table 4, by setting (TP × NA) / λ to be 0.6 or less, the modulation degree of the minimum amplitude of the BCA reproduction signal is changed to the cross track signal. It was found that the degree of modulation of the maximum amplitude of the BCA reproduction signal is greater than 20% or more. That is, by setting (TP × NA) / λ to 0.6 or less, the minimum amplitude of the BCA reproduction signal becomes larger than the maximum amplitude of the cross track signal, and a BCA reproduction signal with good signal quality can be obtained. I understood. Also, from this, by forming the concave / convex pattern of the BCA so that the modulation degree of the minimum amplitude of the BCA reproduction signal is 20% or more, the minimum amplitude of the BCA reproduction signal becomes larger than the maximum amplitude of the cross track signal. It was found that BCA information can be reproduced more reliably.

  Further, from the results of Table 4, (TP × NA) / λ when the concave / convex pattern of BCA is formed by a groove and the larger level difference (amplitude) of ΔIg and ΔIl1 are divided by the smaller level difference. The relationship with the value (ΔIg / ΔIl1 or ΔIl1 / ΔIg) is shown in FIG. In FIG. 10, the horizontal axis represents (TP × NA) / λ, and the vertical axis represents ΔIg / ΔIl1 or ΔIl1 / ΔIg. As is apparent from FIG. 10, when a concave / convex pattern made of grooves is formed on the BCA, ΔIg / ΔIl1 or ΔIl1 / ΔIg becomes 1.4 or less by setting (TP × NA) / λ to 0.6 or less. Amplitude fluctuation could be reduced. That is, from FIGS. 9 and 10, by forming a groove in the BCA so that (TP × NA) /λ≦0.6, the modulation degree of the minimum amplitude of the BCA reproduction signal exceeds 20% and the reproduction signal As a result, it was found that the BCA reproduction signal can be obtained with good signal quality. In FIG. 10, ΔIg / ΔIl1 or ΔIl1 / ΔIg is set to 1.4 as the standard of superiority or inferiority. As is clear from FIG. 10, this value is obtained when (TP × NA) / λ is increased. This is a value immediately before / ΔIl1 or ΔIl1 / ΔIg suddenly increases (fluctuation increases). Even if ΔIg / ΔIl1 or ΔIl1 / ΔIg is slightly larger than 1.4, the BCA information cannot be reproduced at all. Is based on the numerical value 1.4 immediately before ΔIg / ΔIl1 or ΔIl1 / ΔIg suddenly increases.

  In Example 9, an uneven pattern of BCA is formed by embossed pit rows, the track pitch is 350 nm, the pit width of the embossed pit rows is 190 nm, the width between pit rows is 160 nm, the pit length is 200 nm, and the pit interval is 200 nm. The pit depth was set to 70 nm. An optical information recording medium P was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

  In Example 10, the concave / convex pattern of BCA was formed by grooves and embossed pit rows provided between the grooves, and the track pitch was 350 nm. The groove width of the groove was 200 nm, and the groove depth was 70 nm. The embossed pit row had a pit width of 100 nm, a pit length of 200 nm, a pit interval of 200 nm, and a pit depth of 70 nm. The widths between the embossed pit rows and the grooves located on both sides thereof were 40 nm and 10 nm, respectively. An optical information recording medium Q was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Comparative Example 8]
In Comparative Example 8, an uneven pattern of BCA is formed by embossed pit rows, the track pitch is 400 nm, the pit width of the embossed pit rows is 190 nm, the width between pit rows is 210 nm , the pit length is 200 nm, and the pit interval is 200 nm. The pit depth was set to 70 nm. An optical information recording medium R was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Comparative Example 9]
In Comparative Example 9, the concave / convex pattern of BCA was formed by grooves and embossed pit rows provided between the grooves, and the track pitch was 400 nm. The groove width of the groove was 120 nm and the groove depth was 70 nm. The embossed pit row had a pit width of 80 nm, a pit length of 200 nm, a pit interval of 200 nm, and a pit depth of 70 nm. The widths between the embossed pit rows and the grooves located on both sides thereof were 190 nm and 10 nm, respectively. An optical information recording medium S was produced in the same manner as in Example 1 except that the uneven pattern of BCA was changed.

[Recording and playback characteristics of BCA information]
BCA codes were recorded on the BCA in the same manner as in Example 1 for the optical information recording media manufactured in Examples 9 and 10 and Comparative Examples 8 and 9. Then, in the same manner as in Example 1, the BCA information of each optical information recording medium is obtained with the focus removed from the tracking with a tester including a laser beam having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.65. The minimum amplitude of the BCA reproduction signal and the degree of modulation thereof, and the maximum amplitude of the cross track signal (a larger amplitude fluctuation amount of the amplitude fluctuation of the Low level and the High level of the BCA reproduction signal waveform) were measured.

  For the optical information recording medium (Example 9 and Comparative Example 8) in which the BCA is formed only by the embossed pits, the spot center of the reproduction beam of the tester is set at the center of the embossed pit row of the unrecorded part of the BCA. Reproduction signal level during irradiation (in the state of circle 35 in the central diagram in FIG. 4) and when irradiating the center of the embossed pit row of the BCA recording section (in the circle 37 in the central diagram in FIG. 4) 4) when the center of the BCA unrecorded portion between the embossed pit rows is irradiated with the difference between the reproduction signal level of the state (the amplitude of the BCA reproduction signal) and the spot center of the reproduction beam of the tester. The difference between the reproduction signal level (in the state of circle 34 in the center diagram) and the reproduction signal level when irradiating the center between the embossed pit rows of the BCA recording portion (in the state of circle 36 in the center diagram in FIG. 4) Measure the amplitude of the BCA playback signal .

Further, for the optical information recording medium (Example 10 and Comparative Example 9) in which BCA is formed by grooves and embossed pits, the center of the reproduction beam spot of the tester is irradiated to the center of the groove of the unrecorded portion of BCA. When the light is being irradiated (the state of the circle 30 in the right diagram in FIG. 4) and the center of the groove of the BCA recording section is illuminated (the state of the circle 32 in the right diagram in FIG. 4). When the difference between the reproduction signal level (amplitude of the BCA reproduction signal) and the spot center of the reproduction beam of the tester are applied to the center between the groove of the unrecorded portion of the BCA and the embossed pit row (in FIG. 4) (The state of the circle 38 in the right figure of FIG. 4) and the reproduction signal level (the state of the circle 39 in the right figure in FIG. 4) when irradiating the center between the reproduction signal level and the groove and the embossed pit row of the BCA recording section. Difference from signal level (BCA playback signal Was measured amplitude). The above measurement results are shown in Table 5. The meaning of each parameter in Table 5 is as follows.
TP: BCA track pitch RH: High level at minimum amplitude of BCA playback signal RL: Low level at minimum amplitude of BCA playback signal (RH-RL) / RH: Modulation degree at minimum amplitude of BCA playback signal Ict: Cross track signal ΔIg: Reproduction signal amplitude when the reproduction beam spot center is irradiated to the center of the BCA groove ΔI12: The reproduction beam spot center is irradiated to the center between the BCA groove and the embossed pit row Amplitude of reproduction signal when reading is performed ΔIp: Amplitude of reproduction signal when the center of the reproduction beam spot is irradiated to the center of the embossed pit row of the BCA ΔIo: Center of the reproduction beam spot center between the embossed pit rows of the BCA Of playback signal when irradiating

  As is apparent from Table 5, in the optical information recording media of Examples 9 and 10, the minimum amplitude (RH-RL) of the reproduction signal is larger than the maximum amplitude Ict of the cross track signal, and the modulation degree is 20 % Greatly exceeded. That is, the same results as in Example 1 were obtained even when the BCA uneven pattern was formed in the shape of embossed pit rows or grooves and embossed pit rows instead of grooves. On the other hand, in the optical information recording media of Comparative Examples 8 and 9, the maximum amplitude Ict of the cross track signal was larger than the minimum amplitude (RH-RL) of the reproduction signal, and the degree of modulation was also smaller than 20%.

  Further, as is apparent from Table 5, when the values of ΔIp / ΔIo or ΔIo / ΔIp of the optical information recording medium (Example 9 and Comparative Example 8) in which the BCA is formed only by the embossed pit row are compared, 9 (TP × NA / λ = 0.562) was 1.4 or less and the amplitude fluctuation was small, but in Comparative Example 8 (TP × NA / λ = 0.642), it was larger than 1.4. . When the values of ΔIg / ΔIl2 or ΔIl2 / ΔIg of the optical information recording medium (Example 10 and Comparative Example 9) in which the BCA is formed of grooves and embossed pit rows are compared, Example 10 (TP × NA / λ = 0) .562) was 1.4 or less, and the amplitude fluctuation was small, but in Comparative Example 9 (TP × NA / λ = 0.642), it was larger than 1.4. That is, even if the concave / convex pattern of BCA is formed in the shape of an embossed pit row or a groove and an embossed pit row instead of the groove, BCA can be obtained by setting TP × NA / λ ≦ 0.6 as in the first embodiment. It was found that the amplitude fluctuation of the reproduction signal was also reduced, and good signal quality was obtained.

  According to the optical information recording medium of the present invention, a light absorption layer (recording layer made of a dye material) having a thickness sufficient to obtain a reproduction signal from BCA can be formed on a BCA substrate, and Even if the BCA information is reproduced without performing tracking control, a BCA reproduction signal with very small amplitude fluctuation can be obtained. Therefore, the optical information recording medium of the present invention is optimal for an optical information recording medium such as HD DVD-R in which a recording layer is formed of a dye material and reproduces BCA information without tracking. is there.

FIG. 1 is a schematic plan view of an embodiment of the optical information recording medium of the present invention. FIG. 2 is a schematic configuration diagram of the substrate shape in the BCA, management information area, and user information area of the optical information recording medium of the present invention. FIG. 3 is a diagram for explaining the shape of the concave / convex pattern of BCA. FIG. 4 is a diagram showing the positional relationship between the concavo-convex pattern and the reproduction beam spot when the reproduction beam is irradiated onto the BCA. FIG. 5 is a schematic sectional view of an embodiment of the optical information recording medium of the present invention. FIG. 6 is a schematic configuration diagram of a cutting apparatus used when manufacturing the optical information recording medium of the present invention. FIG. 7 is a photograph of the reproduced signal waveform obtained from the BCA of the optical information recording medium produced in Example 1 and Comparative Example 1. FIG. 8 is a diagram showing the relationship between the LW1, LW2, and LW3 and the modulation degree in the optical information recording media manufactured in Examples and Comparative Examples. FIG. 9 is a diagram showing the relationship between the BCA track pitch TP and the modulation degree in the optical information recording media manufactured in the examples and comparative examples. FIG. 10 is a diagram showing the relationship between the BCA track pitch and ΔIg / ΔIl1 or ΔIl1 / ΔIg in the optical information recording media manufactured in the examples and comparative examples. FIG. 11 is a diagram showing another example of the embossed pit row pattern of BCA.

Explanation of symbols

1 Optical information recording medium 2 BCA
3 Management information area 4 User information area 5, 7a, 9 Groove 5a Land portion 6, 7b Embossed pit 10 Substrate 11 Recording layer 12 Reflective layer 13 Adhesive layer 14 Dummy substrate 20 BCA reproduction signal 23, 24 Cross track signal 28 Recording unit 29 BCA recording unit 30 to 39 Reproduction beam spot 40 LW1
42 Track pitch TP
43 LW2
45 LW3

Claims (13)

An optical information recording medium comprising a substrate and a light absorbing layer formed of a pigment material on the substrate:
A user information area in which a concavo-convex pattern including spiral or concentric grooves is formed;
A BCA provided on the inner circumference side of the user information area and having information recorded by a barcode;
An optical information recording medium, wherein an uneven pattern different from the uneven pattern of the user information area is formed on the BCA. Between the track pitch TP of the concavo-convex pattern of the BCA and the track pitch TPy of the concavo-convex pattern of the user information area,
TP <TPy
The optical information recording medium according to claim 1, wherein the relationship is established. The concave / convex pattern of the BCA includes grooves, and the width LW1 between the grooves of the BCA, the wavelength λ of the reproduction beam used for reproducing the optical information recording medium, and the numerical aperture NA of the objective lens,
(LW1 × NA) /λ≦0.3
The optical information recording medium according to claim 1, wherein the relationship is established. When reproducing the BCA information by irradiating the BCA with the reproduction beam without tracking, the reproduction signal amplitude obtained when the spot center of the reproduction beam is located at the center of the groove, and the reproduction Of the amplitudes of the reproduction signals obtained when the beam spot center is located at the center between the grooves, one amplitude is larger than the other amplitude, and the ratio of the amplitude of one to the other The optical information recording medium according to claim 3, wherein the optical information recording medium is 1.4 or less. The concavo-convex pattern of the BCA includes embossed pit rows, and the width LW2 between the embossed pit rows of the BCA, the wavelength λ of the reproduction beam used for reproducing the optical information recording medium, and the numerical aperture NA of the objective lens,
(LW2 × NA) /λ≦0.3
The optical information recording medium according to claim 1, wherein the relationship is established. When reproducing the BCA information by irradiating the BCA with the reproduction beam without tracking, the amplitude of the reproduction signal obtained when the spot center of the reproduction beam is located at the center of the embossed pit row; Of the amplitudes of the reproduction signals obtained when the spot center of the reproduction beam is located at the center between the embossed pit rows, one amplitude is greater than the other amplitude, and one amplitude and the other 6. The optical information recording medium according to claim 5, wherein the ratio to the amplitude is 1.4 or less. The concavo-convex pattern of the BCA includes a groove and an embossed pit row formed between the grooves, the wider width LW3 of the width between the embossed pit row and the grooves on both sides of the groove, and the optical information recording medium Between the wavelength λ of the reproduction beam used for reproduction and the numerical aperture NA of the objective lens,
(LW3 × NA) /λ≦0.3
The optical information recording medium according to claim 1, wherein the relationship is established. When reproducing the BCA information by irradiating the BCA with the reproduction beam without tracking, the reproduction signal amplitude obtained when the spot center of the reproduction beam is located at the center of the groove, and the reproduction Of the amplitudes of the reproduction signals obtained when the beam spot center is located in the center between the groove and the embossed pit row, one amplitude is larger than the other amplitude, and one amplitude and the other The optical information recording medium according to claim 7, wherein a ratio of the amplitude to the amplitude is 1.4 or less. Between the minimum amplitude Imin of the reproduction signal when reproducing the BCA information without tracking and the amplitude CT of the cross track signal,
Imin> CT
The optical information recording medium according to claim 1, wherein the relationship is established. Between the track pitch TP of the BCA, the wavelength λ of the reproduction beam used for reproducing the optical information recording medium, and the numerical aperture NA of the objective lens,
(TP × NA) /λ≦0.6
The optical information recording medium according to claim 1, wherein the relationship is established. Between the track pitch TP of the BCA, the wavelength λ of the reproduction beam used for reproducing the optical information recording medium, and the numerical aperture NA of the objective lens,
0.45 ≦ (TP × NA) /λ≦0.6
The optical information recording medium according to claim 1, wherein the relationship is established. The reflectance of the recording part of the BCA is different from the reflectance of the unrecorded part, and between the higher reflectance RH and the lower reflectance RL,
(RH-RL) /RH≧0.2
The optical information recording medium according to claim 1, wherein the relationship is established. 13. The optical information recording medium according to claim 1, wherein information in a user information area of the optical information recording medium is recorded and reproduced using a blue laser.

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