JP2007287318A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which has two or more information sections, and can perform recording and reproduction of information to the information section far from a light incident side stably and with high reliability. <P>SOLUTION: The optical recording medium has a first information section 10 having a first preformatted region, a first transition region, a first test region and a first information recording region and a second information section 20 formed on the first information section and having a second preformatted region, a second transition region, a second test region and a second information recording region. When distances from the center of the optical recording medium in a radial position of the innermost peripheral track in the second test region on the inner peripheral side and a radial position of the outermost peripheral track in the second test region on the outer peripheral side are defined as R1 and R2, respectively, and the radius of a light beam in the first information section when the optical beam is condensed in the second information section is defined as r, the first preformatted region, the first transition region, the first test region on the inner peripheral side and the first test region on the outer peripheral side are disposed in a region of the first information section different from a region where the distance from the center of the optical recording medium is in the range of R1-r to R2 +r. Thereby, the second test region is irradiated with the laser beam without making the laser beam pass through the first preformatted region, the first transition region and the first test region when the recording condition of the second information section is determined to the optical recording medium in which the optical beam is made incident from the first information section side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical recording medium, and more particularly, a ROM region having two or more information portions each having a substrate and a recording layer, and at least one information portion having information pre-formatted on the substrate in advance, The present invention relates to an optical recording medium having an information recording area for additionally recording information.

  As optical recording media, read-only, write once and rewritable optical disks are widely used. Of these, DVD-ROM (reproduction-only type), DVD-R (write-once type), and DVD-RAM (rewritable type) are well known. Among these optical disks, for example, a method for producing a DVD-R is as follows. First, a recording layer is formed by applying an organic dye material on a light-transmissive disc-shaped substrate having a thickness of 0.6 mm, and then a light reflecting layer is laminated on the recording layer to produce a disc (recording disc). To do. This DVD-R recording disk has a recording capacity of 4.7 GB. Next, the recording disk is bonded to a dummy disk having a thickness of 0.6 mm which cannot be written. In this way, a single-sided recordable DVD-R having a recording capacity of 4.7 GB is produced.

  There is also a 9.4 GB double-sided recording type DVD-R in which two recording disks having a recording capacity of 4.7 GB are bonded together. In the double-sided recording type DVD-R, information is recorded and reproduced by irradiating laser light from both sides. Although the double-sided recording type DVD-R has a large recording capacity of 9.4 GB, it records and reproduces information on the recording disk on the opposite side because information is recorded and reproduced by irradiating laser light from both sides. When doing so, it was necessary to turn the disc over.

  Recently, an optical disc (single-sided, dual-layer type optical disc) capable of recording information on both recording discs by irradiating a laser beam only on one side of the optical disc to which two recording discs are bonded. ) Has been proposed (see, for example, Patent Document 1). In fact, single-sided, dual-layer optical discs with a recording capacity of 8.5 GB have been developed and are spreading on the market.

JP 11-66622 A

  In the single-sided dual-layer type optical disk as described above, the first recording disk (hereinafter also referred to as the first information section), the spacer layer and the second recording disk (hereinafter referred to as the second information) from the light beam incident side. Have a structure provided in this order. When recording / reproducing information with respect to the second information part, the light beam is irradiated to the second information part via the first information part and the spacer layer.

  However, in such a single-sided, dual-layer type optical disc, the substrate of the first information section is formed with areas having different substrate shapes, such as a mirror surface section and a preformatted information area, so that it passes through the first information section. The light transmittance of the light beam is different in each region having a different shape formed on the substrate of the first information section. In addition, the light transmittance of the light beam passing through the first information portion is different in an unrecorded information recording area in the recording layer of the first information portion, an information recording area after recording, and the like. That is, the light transmittance of the light beam that passes through the first information portion differs depending on the shape of the substrate in the first information portion and the recording state of the recording layer. Therefore, when recording / reproducing information on / from the second information part of the single-sided, double-layer type optical disc, if the light beam passes through different areas of the light transmittance of the first information part, it is irradiated from the optical head. Even if the amount of light to be emitted is constant, the amount of light irradiated to the second information portion changes.

  The light amount fluctuation of the light beam that reaches the second information unit described above cannot be detected other than the reflected light amount from the second information unit. Therefore, it is possible to cope with this light quantity fluctuation by performing AGC (Auto Gain Control) on the reproduction signal of the second information section. However, since the light intensity distribution in the light beam becomes non-uniform, an offset occurs with respect to the focus error signal and tracking error signal. Such an offset has an adverse effect on the reproduction signal quality of the second information part, more than the influence of the light amount fluctuation of the light beam, and causes an error in information reproduction. In some cases, focus control or tracking control during recording / reproduction of the second information section may not be maintained.

  Furthermore, the light amount fluctuation of the light beam that reaches the second information section has the following fatal effect during information recording. When the recording power of the second information unit is set with a light beam that passes through a region with a high light transmittance of the first information unit, a light beam that passes through a region with a low light transmittance of the first information unit is irradiated. 2 In the area of the information section, the recording power of the light beam is insufficient, and there is a possibility that a large asymmetry is generated in the signal. In the opposite case, that is, when the recording power of the second information unit is set with a light beam that passes through the low light transmittance region of the first information portion, it passes through the high light transmittance region of the first information portion. In the area of the second information portion irradiated with the light beam to be irradiated, since the signal is written with overpower, there is a possibility of causing cross light (overwriting on the signal of the adjacent track). . Also, if there is a change in the light transmittance of the light beam during the test for determining the recording power of the second information section, the recording power is affected by both the recording light quantity fluctuation and the reproduction amplitude fluctuation when determining the recording power. There is a possibility that the test operation ends without being determined, and recording of the entire second information section becomes impossible.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to record / reproduce information with respect to an information portion far from the light incident side in an optical recording medium having two or more information portions. An object of the present invention is to provide an optical recording medium that can be stably and highly reliable.

According to a first aspect of the present invention, there is provided an optical recording medium on which information is recorded and reproduced by irradiation with a light beam,
A first information section;
A second information part irradiated with the light beam via the first information part,
The first information section is arranged in this order from the inner circumference side to the first preformat area, the first transition area, the first inner circumference test area, the first information recording area, and the first outer circumference test area. And the first preformat area is provided with embossed pits, the first transition area is a mirror surface, and the first information recording area, the first inner circumference side test area and the first outer circumference side test area have the above-mentioned A light beam guide groove is provided,
The second information section is arranged in this order from the inner circumference side to the second preformat area, the second transition area, the second inner circumference side test area, the second information recording area, and the second outer circumference side test area. The second preformat area is provided with embossed pits, the second transition area is a mirror surface, and the second information recording area, the second inner periphery side test area, and the second outer periphery side test area are A light beam guide groove is provided,
The distances from the center of the optical recording medium at the radial position of the innermost track of the second inner peripheral side test area and the radial position of the outermost track of the second outer peripheral side test area are R1 and R2, respectively. When the radius of the light beam in the first information part when the light beam is focused on is r,
The first preformat area, the first transition area, the first inner circumference side test area, and the first outer circumference side test area are different from the areas of distances R1-r to R2 + r from the center of the optical recording medium of the first information section. An optical recording medium is provided which is arranged in the region.

According to a second aspect of the present invention, there is provided an optical recording medium on which information is recorded and reproduced by irradiation with a light beam,
A first information section having a first substrate and a first recording layer, the light beam being incident from the first substrate side;
A second information section having a second substrate and a second recording layer, and being irradiated with the light beam through the first information section;
The first information section is arranged in this order from the inner circumference side to the first preformat area, the first transition area, the first inner circumference test area, the first information recording area, and the first outer circumference test area. The area on the first substrate corresponding to the first preformat area is provided with emboss pits, the area on the first substrate corresponding to the first transition area is a mirror surface, and the first information recording area The light beam guide groove is provided in a region on the first substrate corresponding to the first inner peripheral side test region and the first outer peripheral side test region,
The second information section is arranged in this order from the inner circumference side to the second preformat area, the second transition area, the second inner circumference side test area, the second information recording area, and the second outer circumference side test area. The area on the second substrate corresponding to the second preformat area is provided with emboss pits, the area on the second substrate corresponding to the second transition area is a mirror surface, and the second information recording area The light beam guide groove is provided in a region on the second substrate corresponding to the second inner peripheral side test region and the second outer peripheral side test region,
The distances from the center of the optical recording medium at the radial position of the innermost track of the second inner peripheral side test area and the radial position of the outermost track of the second outer peripheral side test area are R1 and R2, respectively. When the radius of the light beam in the first information part when the light beam is focused on is r,
The first preformat area, the first transition area, the first inner circumference side test area, and the first outer circumference side test area are different from the areas of distances R1-r to R2 + r from the center of the optical recording medium of the first information section. An optical recording medium is provided which is arranged in the region.

  In the optical recording medium of the present invention, it is preferable that a spacer layer is further provided between the first information part and the second information part.

FIG. 4 shows an example of a physical format positional relationship between the first information section and the second information section in the single-sided, double-layer type optical recording medium. The example shown in FIG. 4 is an optical recording medium in the case where test areas are provided in the vicinity of the inner periphery and the vicinity of the outer periphery in the second information recording area of the second information section. That is, the radial position R (1, TI, i) of the innermost track of the test area near the inner periphery of the second information recording area in FIG. 4, the outermost track of the test area near the outer periphery of the second information recording area Radial position R (1, TO, o), radial position R (0, G, i) of the innermost guide groove of the first information recording area of the first information section, and first information of the first information section When the distance from the center of the optical recording medium at the radial position R (0, G, o) of the outermost peripheral guide groove of the recording area is R1, R2, R3 and R4, respectively, The optical recording medium of the present invention in the case where both of the following expressions (1) and (2) are satisfied.
R1 ≧ R3 + r (1)
R2 ≦ R4-r (2)

  In addition, the meaning of each parameter in the parentheses of the above-described radial position R (P1, P2, P3) is as follows. The first parameter P1 is a parameter indicating whether the radial position R belongs to the first information part or the second information part. In the case of the first information part (L0 layer), the first parameter P1 is “0”. ", And in the case of the second information part (L1 layer)," 1 "is displayed. The second parameter P2 is a parameter indicating which area in the physical format is the radial position. In the case of the test area near the inner periphery of the second information recording area, the second parameter P2 is displayed as “TI”. In the case of the test area near the outer periphery of the information recording area, “TO” is displayed. In the case of the information recording area (area where the groove is formed), “G” is displayed, and the user information is recorded. In the case of the information recording / reproducing area to be displayed, “D” is displayed. The third parameter P3 is a parameter for displaying whether the radial position is the innermost position or the outermost position of the area specified by the parameter P2. When the radial position is the innermost position, “I” is displayed, and “o” is displayed when the position is the outermost peripheral position.

  FIG. 4 shows physical formats of the first information unit 10 (hereinafter also referred to as L0 layer) and the second information unit 20 (hereinafter also referred to as L1 layer) that are adjacent to each other via the spacer layer 30 (adhesive layer). FIG. 2 is a schematic cross-sectional view in the radial direction, and the direction from the left side to the right side of the drawing is the outer peripheral direction of the optical recording medium. In the example of FIG. 4, the physical format of the L0 layer 10 is the preformat area 51 (ROM area), the transition area 52 (mirror area), the information recording area 50, and the mirror area 58 from the inner circumference side of the optical recording medium. It consists of. As shown in FIG. 4, the information recording area 50 of the L0 layer 10 is composed of two buffer areas 53 and 57, two test areas 54 and 56, and an information recording / reproducing area 55. And 56 are provided near the inner periphery and the outer periphery of the information recording area 50, respectively. In the example of FIG. 4, the L1 layer 20 also has the same physical format configuration as the L0 layer 10.

FIG. 4A shows the lower limit condition (R1 = R3 + r) of the above expression (1) with respect to the radial position R (1, TI, i) of the innermost track in the test area 64 on the inner circumference side of the L1 layer 20. Is a diagram showing the positional relationship of the physical format between the L0 layer 10 and the L1 layer 20 when the above relationship is established. On the other hand, FIG. 4B shows the upper limit condition (R2 = R4) of the above equation (2) with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. FIG. 10 is a diagram illustrating a physical format positional relationship between the L0 layer 10 and the L1 layer 20 when the relationship (−r) is established. Normally, there is an eccentricity when the L0 layer 10 and the L1 layer 20 are bonded together. In the example of FIG. 4, the outer peripheral ends of the L0 layer 10 and the L1 layer 20 are specified as the eccentricity specification value RR _p-p ( An example of deviation by (PEAK TO PEAK value) is shown.

  In an optical recording medium in which a radial position relationship as shown in FIG. 4A is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test area 64 on the inner peripheral side of the L1 layer 20 Since the relationship of R1 = R3 + r (the relationship of the above equation (1)) is established with respect to the radial position R (1, TI, i) of the innermost track, as shown in FIG. Even if the light beam 40 is condensed at 64 innermost track positions R (1, TI, i), the light beam 40 does not pass through the transition region 52 and the preformat region 51 of the L0 layer 10.

  Further, as apparent from FIG. 4A, the relationship of R2 <R4-r with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. (Equation (2) above) holds, so that even if the light beam 40 is condensed at the outermost peripheral position R (1, TO, o) of the test region 66 on the outer peripheral side of the L1 layer 20, the light beam 40 Does not pass through the mirror region 58 on the outer peripheral side of the L0 layer 10.

  On the other hand, in the optical recording medium in which the radial position relationship shown in FIG. 4B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test area 66 on the outer peripheral side of the L1 layer 20 is used. Since the relationship of R2 = R4-r (the relationship of the above equation (2)) is established with respect to the radial position R (1, TO, o) of the outermost track of FIG. 4, the test is performed as shown in FIG. Even if the light beam 40 is focused on the outermost track position R (1, TO, o) of the region 66, the light beam 40 does not pass through the mirror region 58 of the L0 layer 10.

  4B, the relationship of R1> R3 + r with respect to the radial position R (1, TI, i) of the innermost track of the test region 64 on the inner circumference side of the L1 layer 20 ( Therefore, even if the light beam 40 is condensed at the innermost peripheral position R (1, TI, i) of the test region 64 on the inner peripheral side of the L1 layer 20, the light beam 40 40 does not pass through the transition area 52 and the preformat area 51 of the L0 layer 10.

  That is, the relationship between the physical positions of the L0 layer 10 and the physical format of the L1 layer 20 as shown in FIGS. 4A and 4B (relationships of the above expressions (1) and (2)). In the formed optical recording medium, the light beam condensed over the entire test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20 is transmitted to the preformat area 51, the transition area 52, and the mirror area of the L0 layer 10. 58, only the information recording area 50 is passed. The region on the first substrate corresponding to the information recording region 50 of the L0 layer 10 is a region where grooves are formed over the entire region (region where a uniform uneven pattern is formed). The transmittance of the light beam 40 passing through the information recording area 50 is substantially constant over the entire information recording area 50. Therefore, in the optical recording medium in which the radial position relationship as shown in FIGS. 4A and 4B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test of the L1 layer 20 is performed. Since the light beam 40 applied to the areas 64 and 66 and the information recording / reproducing area 65 passes only through the information recording area 50 of the L0 layer 10 having a substantially constant transmittance, the test areas 64 and 66 and information recording of the L1 layer 20 are recorded. Variations in the amount of light of the light beam 40 reaching the reproduction area 65 can be suppressed.

  As described above, in the optical recording medium having the test area near the inner circumference and the outer circumference of the second information recording area of the L1 layer 20, the physical format of the L0 layer 10 and the physical format of the L1 layer 20 are By establishing the relationship between the radial positions expressed by the formulas (1) and (2), the light beam 40 with very little light quantity fluctuation is irradiated onto the inner and outer test areas 64 and 66 of the L1 layer 20. Therefore, the optimum recording power for information recording can be determined with certainty. Further, since the light amount fluctuation of the light beam reaching the information recording / reproducing area 65 of the L1 layer 20 is also very small, user information and the like are stably recorded in the information recording / reproducing area 65 of the L1 layer 20 with the optimum recording power. be able to. Therefore, the incident side of the light beam 40 is adjusted by adjusting the relationship of the radial positions of the physical format of the L0 layer 10 and the physical format of the L1 layer 20 so that the relationship of the above expressions (1) and (2) is established. It is possible to stably record and reproduce information with respect to the information portion (L1 layer) on the side far from the remote.

  In the above description, for an optical recording medium having test areas near both the inner circumference and the outer circumference of the second information recording area of the second information section (L1 layer) on the side far from the incident side of the light beam. As described above, when the test area is provided only in the vicinity of the inner periphery of the second information recording area of the second information section, the first on the incident side of the light beam is established so that only the relationship of the above expression (1) is established. It is only necessary to adjust the relationship of the radial position between the physical format of the one information part (L0 layer) and the physical format of the second information part, and only in the vicinity of the outer periphery of the second information recording area of the second information part. Is provided, the relationship between the radial positions of the physical format of the first information section and the physical format of the second information section may be adjusted so that only the relationship of the above expression (2) is established. In any case, the same effect as in the case of the optical recording medium having the test areas near both the inner circumference and the outer circumference of the second information recording area of the second information section described above can be obtained.

  In the present specification, the “radius r of the light beam in the first information portion” means the radius of the light beam at the interface between the first recording layer of the first information portion (L0 layer) and the first substrate. . Note that the radius r of the light beam in the first information part when the light beam is focused on the second information part (L1 layer) can be obtained from FIG. 6 as follows.

  As shown in FIG. 6, the thickness of the spacer layer between the first information part (L0 in FIG. 6) and the second information part (L1 in FIG. 6) is D, the refractive index of the spacer layer is ns, Assuming that the numerical aperture of the aperture lens is NA, the radius r of the light beam in the first information section can be obtained from the following mathematical formula from the geometrical relationship shown in FIG. However, the solid line L0 in FIG. 6 represents the position of the first recording layer in the first information section, and the solid line L1 represents the position of the second recording layer in the second information section. In FIG. 6, the thicknesses of the first recording layer and the second recording layer are not taken into account, but this is because the thicknesses of the first and second recording layers are very small relative to the thickness of the spacer layer. is there. For example, in the embodiments described later, the thicknesses of the first and second recording layers are less than about 0.4% of the thickness of the spacer layer. Even if the film thicknesses of the first and second recording layers are not considered in the calculation, the value of the radius r of the light beam is not greatly affected. In the examples described later, a reflective layer, an interface layer, and the like are provided between the recording layer and the spacer layer. However, the thickness of these layers is very small compared to the thickness of the spacer layer. Even if the thickness of these layers is not taken into consideration, the value of the radius r of the light beam is not greatly affected.

  At the stage of designing the single-sided, double-layer type optical recording medium, the physical format positional relationship between the first and second information sections of the manufactured optical recording medium is the above formula (1) and / or (2). The radial position of the physical format of each information part is set so as to satisfy, but at that time, it is designed in consideration of the shift of the center position due to the eccentricity when the first information part and the second information part are bonded together Is preferred. It should be noted that the deviation of the center position between the first information portion and the second information portion is maximum when the disc is decentered in the opposite direction across the disc clamp center.

Specifically, the radial position R (1, TI, i) of the innermost track in the test area near the inner circumference of the second information recording area of the second information section and the test area near the outer circumference of the second information recording area The distances from the center of the second information section at the radial position R (1, TO, o) of the outermost track of the first track are R1 ′ and R2 ′, respectively, and the innermost guide groove in the first information recording area of the first information section R3 ′ and R4 ′ are the distances from the center of the first information section at the radial position R (0, G, i) of the first information recording area and the radial position R (0, G, o) of the outermost peripheral guide groove of the first information recording area, respectively. And r is the radius of the light beam in the first information part when the light beam is focused on the second information part, and RR _p-p (PEAK TO PEAK value) is the specification value for the eccentricity. When a test area is provided near the inner periphery of the second information recording area of the second information section , The following: (1) 'formula _{R1' ≧ R3 '+ RR p} -p + r ... (1)'
When the radial position of the physical format of each information section is designed so that the above holds, and a test area is provided in the vicinity of the outer periphery of the second information recording area of the second information section, the following (2) 'expression R2' ≦ R4′−RR _p−p −r (2) ′
It is preferable to design the radial position of the physical format of each information section so that is established. Further, when the test areas are provided near both the inner circumference and the outer circumference of the second information recording area of the second information section, each information section is set so that the above expressions (1) ′ and (2) ′ are satisfied. It is preferable to design the radial position of the physical format.

  When actually producing a single-sided, double-layer type optical disc, the eccentricity is always produced so that it falls within the specification value, so that the above formula (1) ′ and / or (2) ′ is satisfied. If the positional relationship of the physical format between the first and second information units is designed, in the manufactured optical recording medium, the above-described physical format of the first information unit and the physical format of the second information unit are always included. (1) and / or the relationship of the radial position of the formula (2) is established.

  More realistically, at the design stage, error factors such as substrate shrinkage, the resulting deviation from the roundness of the groove, and the positioning accuracy of the mastering device are added to the above formulas (1) 'and (2)'. Thus, it is preferable to set the radial position of the physical format of each information section.

In the optical recording medium of the present invention, the radial position of the innermost track in which information is recorded in the first information recording area, and the radial position of the outermost track in which information is recorded in the first information recording area Where the distance from the center of the optical recording medium in R5 is R5 and R6, respectively, the following formula (3)
R1 ≧ R5 + r (3)
And the following formula (4)
R2 ≦ R6-r (4)
Is established.

  In the present specification, “radial position of the innermost track in which information is recorded in the first information recording area” means the innermost circumference of the area in which information is additionally recorded by the user in the first information recording area. This means the radial position of the track.

  The light transmittance of the light beam passing through the first information portion varies depending on the shape of the first substrate of the first information portion as described above, and further, the unrecorded state of the first recording layer of the first information portion. The information recording area, the information recording area after recording, or the like, that is, the recording state of the first recording layer may change. For example, when the first recording layer of the first information portion is formed of a dye material, the transmittance may change before and after recording information on the first recording layer. In particular, in the test area for determining the recording power, recording is performed by changing the recording power from a lower one to a power larger than the optimum recording power, so that the transmittance fluctuation becomes larger. In addition, since the test writing is not always performed over the entire test area, there may be a case where a recording area and an unrecorded area are mixed in the test area. Also in such a case, the light beam transmittance may change greatly in the test area, and the light amount of the light beam reaching the second information section may fluctuate.

  As described above, when the light amount of the light beam reaching the second information section varies depending on the recording state of the test area of the first information section, the light beam is irradiated to the test area and the information recording area of the second information section. At this time, the positional relationship between the physical format of the first information section and the physical format of the second information section may be adjusted so that the light beam does not pass through the test area of the first information section. The conditions for satisfying such a positional relationship are the relationships indicated by the above equations (3) and (4). Note that the above equations (3) and (4) are conditional equations when the transmittance varies depending on both the shape of the first substrate of the first information section and the recording state of the first recording layer. ) And (4) are included in the condition ranges of the above expressions (1) and (2), respectively.

  FIG. 5 shows an example of the positional relationship between the physical format of the first information section and the physical format of the second information section when both the relations of the above expressions (3) and (4) are satisfied. FIG. 5 is a schematic configuration cross-sectional view in the radial direction of each physical format of the first information unit 10 (L0 layer) and the second information unit 20 (L1 layer) that are adjacent via the spacer layer 30, from the left side of the drawing. The direction toward the right side is the outer peripheral direction of the optical recording medium.

FIG. 5A shows the lower limit condition (R1 = R5 + r) of the above expression (3) with respect to the radial position R (1, TI, i) of the innermost track of the test region 64 on the inner circumference side of the L1 layer 20. Is a diagram showing the positional relationship of the physical format between the L0 layer 10 and the L1 layer 20 when the above relationship is established. On the other hand, FIG. 5B shows the upper limit condition (R2 = R6) of the above equation (4) with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. FIG. 10 is a diagram illustrating a physical format positional relationship between the L0 layer 10 and the L1 layer 20 when the relationship (−r) is established. Normally, there is an eccentricity when the L0 layer 10 and the L1 layer 20 are bonded together, and in the example of FIG. 5, the outer peripheral ends of the L0 layer 10 and the L1 layer 20 are only the specification value RRp _{-p of the} eccentric amount. A shifted example is shown.

  In the optical recording medium in which the relationship of the radial positions as shown in FIG. 5A is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test area 64 on the inner peripheral side of the L1 layer 20 Since R1 = R5 + r (the relationship of the above expression (3)) is established for the radial position R (1, TI, i) of the innermost track, as shown in FIG. 5A, the test of the L1 layer 20 Even if the light beam 40 is focused on the innermost track position R (1, TI, i) of the region 64, the light beam 40 passes through the test region 54, the transition region 52, and the preformat region 51 of the L0 layer 10. do not do.

  Further, as apparent from FIG. 5A, the relationship of R2 <R6-r with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. (Equation (4) above) holds, so that even if the light beam 40 is condensed at the outermost peripheral position R (1, TO, o) of the test region 66 on the outer peripheral side of the L1 layer 20, the light beam 40 Does not pass through the test area 56 and the mirror area 58 on the outer peripheral side of the L0 layer 10.

  On the other hand, in the optical recording medium in which the relationship of the radial positions as shown in FIG. 5B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test on the outer and inner peripheral side of the L1 layer 20 is performed. Since R2 = R6-r (the relationship of the above equation (4)) is established for the radial position R (1, TO, o) of the outermost track in the region 66, as shown in FIG. Even if the light beam 40 is condensed at the outermost track position R (1, TO, o) of the test area 66, the light beam 40 does not pass through the test area 56 and the mirror area 58 on the outer peripheral side of the L0 layer 10.

  Further, as apparent from FIG. 5B, for the radial position R (1, TI, i) of the innermost track of the test region 64 on the inner circumference side of the L1 layer 20, the relationship of R1> R5 + r Since (the relationship of the above expression (3)) is established, even if the light beam 40 is condensed at the innermost peripheral position R (1, TI, i) of the test area 64 on the inner peripheral side of the L1 layer 20, the light The beam 40 does not pass through the test area 54, the transition area 52, and the preformat area 51 on the inner circumference side of the L1 layer 10.

  That is, the relationship between the physical positions of the L0 layer 10 and the physical format of the L1 layer 20 is the radial position relationship (the relationship of the above expressions (3) and (4)) as shown in FIGS. In the established optical recording medium, the light beam condensed over the entire test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20 is preformatted area 51, transition area 52, and mirror area of the L0 layer 10. 58 and the test areas 54 and 56, but only the information recording / reproducing area 55 of the L0 layer 10 is passed. Grooves are formed throughout the information recording / reproducing area 55 of the L0 layer 10, and information is recorded with a predetermined recording power. In addition, since information recording is normally performed from the L0 layer 10, at the time when information is recorded in the L1 layer 20, user information and the like are recorded uniformly over the entire information recording / reproducing area 55 of the L0 layer 10. is there. Therefore, the transmittance of the light beam passing through the information recording / reproducing area 55 of the L0 layer 10 becomes substantially uniform. Therefore, in the optical recording medium in which the radial position relationship as shown in FIGS. 5A and 5B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the first of the L0 layer 10 is used. Even when the light transmittance varies depending on the recording state of the test areas 54 and 56 as well as the shape of the substrate, the light beam applied to the test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20. 40 passes through only the information recording / reproducing area 55 of the L0 layer 10 having a substantially constant transmittance, so that fluctuations in the light quantity of the light beam 40 reaching the test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20 are suppressed. be able to.

  As described above, in the optical recording medium in which the radial position relationship expressed by the above equations (3) and (4) is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the L0 layer 10 Even when the light transmittance fluctuates depending on the recording state of the test areas 54 and 56 as well as the shape of the first substrate, the light beam 40 with a very small light amount fluctuation is reflected on the inner peripheral side of the L1 layer 20 and Since the test areas 64 and 66 on the outer peripheral side are irradiated, the optimum recording power for information recording can be determined reliably. Further, since the light amount fluctuation of the light beam reaching the information recording / reproducing area 65 of the L1 layer 20 is also very small, user information and the like are stably recorded in the information recording / reproducing area 65 of the L1 layer 20 with the optimum recording power. be able to. Therefore, when the light transmittance varies depending on the shape of the first substrate of the L0 layer 10 and the recording state of the test area, the relationship of the radial position between the physical format of the L0 layer 10 and the physical format of the L1 layer 20 Is adjusted so that the relationship expressed by the above equations (3) and (4) is satisfied, information can be recorded and reproduced stably with respect to the information portion (L1 layer) on the side far from the incident side of the light beam 40. It can be performed with high reliability.

  In the above description, for an optical recording medium having test areas near both the inner circumference and the outer circumference of the second information recording area of the second information section (L1 layer) on the side far from the incident side of the light beam. As described above, when the test area is provided only in the vicinity of the inner periphery of the second information recording area of the second information section, the first on the incident side of the light beam is established so that only the relationship of the above expression (3) is established. It is only necessary to adjust the relationship of the radial position between the physical format of the one information part (L0 layer) and the physical format of the second information part, and only in the vicinity of the outer periphery of the second information recording area of the second information part. Is provided, the relationship between the radial positions of the physical format of the first information section and the physical format of the second information section may be adjusted so that only the relationship of the above expression (4) is established. In any case, the same effect as in the case of the optical recording medium having the test areas near both the inner circumference and the outer circumference of the second information recording area of the second information section described above can be obtained.

  When designing the optical recording medium of the present invention in which the relationship of the above expressions (3) and (4) is established, the center position due to the eccentricity when the first information section and the second information section are bonded together is designed. It is preferable to design in consideration of the deviation.

Specifically, the radial position R (1, TI, i) of the innermost track in the test area near the inner circumference of the second information recording area of the second information section in FIG. 5 and the outer circumference of the second information recording area The distance from the center of the second information portion at the radial position R (1, TO, o) of the outermost track of the adjacent test area is R1 ′ and R2 ′, respectively, and information is recorded in the first information recording area. Of the first information section at the radial position R (0, D, i) of the innermost track and the radial position R (0, D, o) of the outermost track where information is recorded in the first information recording area. The distances from the center are R5 ′ and R6 ′, respectively, the radius of the light beam in the first information portion when the light beam is focused on the second information portion is r, and the eccentricity specification value is RR _p when the _-p, following (3) 'formula _{R1' ≧ R5 '+ RR p} -p + r ... (3 '
And the following (4) ′ expression R2 ′ ≦ R6′−RR _p−p −r (4) ′
It is preferable to design the radial position of the physical format of each information section so that is established.

  When actually manufacturing a single-sided, dual-layer type optical disk, the eccentricity is always manufactured so as to be within the specification value, so that the first (3) ′ and (4) ′ expressions are satisfied. If the positional relationship of the physical format between the second information portion and the second information portion is designed, in the manufactured optical recording medium, the above-mentioned (3) is always between the physical format of the first information portion and the physical format of the second information portion. ) And (4) are satisfied.

  In the optical recording medium of the present invention, the track pitch of the first information portion is preferably larger than the track pitch of the second information portion.

  In the optical recording medium of the present invention, it is preferable that the recording capacity of the first information section and the recording capacity of the second information section are the same.

  When the positional relationship between the physical format of the first information unit and the physical format of the second information unit is set to the positional relationship described with reference to FIG. 5, for example, an area where user information of the second information unit can be recorded ( In FIG. 5, the information recording / reproducing area 65) is narrower than the area (information recording / reproducing area 55 in FIG. 5) where the user information of the first information section can be recorded. Therefore, if the track pitch of the second information part is made narrower than the track pitch of the first information part, the recording capacities of the first information part and the second information part can be made the same.

  A design method in the case where the recording capacities of the first information section and the second information section are the same will be specifically described taking an optical disk compatible with a blue laser as an example.

  When the thickness D of the spacer layer is 25 μm, the refractive index ns of the spacer layer is 1.5, and the NA of the lens is 0.65, the laser beam is focused on the second information part from the above formula (Equation 1). In this case, the radius r of the light beam in the first information portion is about 13.3 μm.

Further, in consideration of the eccentricity when the first information part and the second information part are bonded together, when the eccentricity specification value RR _pp is 50 μm, in the case of this example, the second information part 2nd What is necessary is just to make it so that the radius of the inner and outer periphery of an information recording area (area in which the groove is formed) is narrower by 63.3 μm or more than the first information recording area of the first information section. When the first information recording area of the first information portion is set to have a radius of 23.8 mm to 58.0 mm and the track pitch of the first information portion is 0.400 μm, the track pitch of the second information portion is 0.398 μm, That is, by making the track pitch narrower by about 0.4% than the track pitch of the first information part, the number of tracks of the first information part and the second information part can be made equal, and the same capacity can be obtained.

  In the optical recording medium of the present invention, the positional relationship between the physical format of the first information section and the physical format of the second information section is formed so as to satisfy the above expressions (3) and (4). It is possible to irradiate the test area of the second information section on the side far from the incident side and the information recording / reproducing area for recording user information and the like with a light beam with very little light amount fluctuation. Therefore, when information recording is performed on the second information section far from the light beam incident side, the optimum recording power can be determined reliably, and the user information and the like can be stably used with the optimum recording power. Can be recorded. Therefore, in the single-sided two-layer type optical recording medium of the present invention, the information recording / reproducing process can be performed more stably and reliably with respect to the information part (second information part) far from the incident side of the light beam. it can.

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

Reference form [membrane structure]
In the reference embodiment, an optical disk having a single-sided two-layer structure will be described. A schematic sectional view thereof is shown in FIG. As shown in FIG. 1, in the optical disc 100 of the present embodiment, the first information portion 10 (hereinafter also referred to as L0 layer) and the second information portion 20 (hereinafter also referred to as L1 layer) are bonded layers 30 (referred to as L1 layer). Hereinafter, it has a structure of being bonded via a spacer layer).

  As shown in FIG. 1, the L0 layer 10 includes a first recording layer 12 and a first reflective layer 13 stacked in this order on a first substrate 11. As shown in FIG. 1, the L1 layer 20 is formed by laminating a second reflective layer 23, a second recording layer 22, and an interface layer 24 in this order on a second substrate 21. The L0 layer 10 and the L1 layer 20 are bonded together with the spacer layer 30 so that the first reflective layer 13 of the L0 layer 10 and the interface layer 24 of the L1 layer 20 face each other. In this example, as shown in FIG. 1, the light beam 40 enters from the first substrate 11 side of the L0 layer 10.

  The first substrate 11 and the second substrate 21 are translucent substrates, and emboss pits and user information for recording disc management information for each layer (L0 layer or L1 layer) in advance on each substrate surface. A guide groove (groove) for recording is formed. As a material for the first substrate 11 and the second substrate 21, a resin having a refractive index in the range of 1.4 to 1.7, a large transmittance, and excellent impact resistance is desirable. Specifically, polycarbonate, amorphous polyolefin, acrylic and the like can be used. However, the substrate material is not limited thereto, and any material can be used as the substrate material as long as it has the above properties. As shown in FIG. 1, the second substrate 21 is disposed on the side opposite to the light beam incident side, and therefore does not need to transmit light, but the L0 layer 10 and the L1 layer 20 are bonded. In consideration of maintaining good mechanical properties later, the same material as the first substrate 11 is preferable.

  The first recording layer 12 and the second recording layer 22 absorb the irradiated light beam and generate heat, and melt, evaporate, sublimate, deform, modify or phase change, phase change, and form on the recording layer itself or the surface of the substrate. It is a layer having the function of forming recording pits. In the case of producing a write-once optical disc, the material for forming the first recording layer 12 and the second recording layer 22 is preferably a light-absorbing organic dye, such as a cyanine dye, polymethine dye, triarylmethane dye, pyrylium dye, phenanthrene. Dyes, azo dyes, tetradehydrocholine dyes, triarylamine dyes, squarylium dyes, croconic methine dyes and the like can be used. However, the dye material that can be used in the recording layer is not limited to the dye material described above. The material for forming the first recording layer 12 and the second recording layer 22 described above may contain other dyes, additives, polymers (for example, thermoplastic resins such as nitrocellulose, thermoplastic elastomers), and the like.

  When the dye material or a material containing any additive is used as a material for forming the first recording layer 12 and the second recording layer 22, the first recording layer 12 and the second recording layer 22 On the first substrate 11 and the second reflective layer 23, materials containing arbitrary additives are dissolved and solvated with a known organic solvent (for example, tetrafluoropropanol, ketone alcohol, acetylacetone, methylcellulob, toluene, etc.). It is formed by a method such as spin coating. When the spin coating method is used as the recording layer forming means, the film thickness of the recording layer can be controlled by adjusting the concentration, viscosity, and solvent drying speed of the dye solution. In addition, when forming the 1st recording layer 12 and the 2nd recording layer 22 with a spin coat method, you may change and form dye material, coating conditions, a solvent, etc. suitably according to a use.

  When a write-once or rewritable optical disk is manufactured, a phase change material may be used as a material for forming the first recording layer 12 and the second recording layer 22. As the phase change material, for example, a material in which a part of Bi—Ge—Te based material is replaced with Si, B, Pb, Sn, etc., Ge—Sn—Sb—Te based material such as Ag, Al, Cr, Mn, etc. A material added with a metal, an Ag-In-Sb-Te recording material, or the like can be used. However, the phase change material that can be used for the recording layer is not limited to the above materials. In the case where the first and second recording layers are formed of the phase change material, it is preferable to form the first and second recording layers by a vapor deposition method or a sputtering method.

  The 1st reflective layer 13 and the 2nd reflective layer 23 consist of metal films, for example, are formed with gold, silver, aluminum, etc., or the alloy containing these metal elements. These metal films are formed by means such as sputtering.

The interface layer 24 of the L1 layer 20 is an indispensable layer for chemically protecting the second recording layer 22 from the adhesive and / or the solvent of the adhesive when the L0 layer 10 and the L1 layer 20 are bonded together. It is. Various dielectric materials are suitable as a material for forming the interface layer 24, and oxides such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , and Ta ₂ O ₅ , nitrides such as SiN, AlN, and TiN, ZnS It is possible to use sulfides and the like. The interface layer 24 needs to have a property that it is optically less absorbed, chemically stable and has a protective effect.

  The spacer layer 30 is desirably formed of a resin having excellent impact resistance. For example, it is formed by applying an ultraviolet curable resin by a spin coating method and irradiating with an ultraviolet ray to be cured. Further, the spacer layer 30 may be formed of an elastic material such as urethane.

The film configuration of the two-layer optical recording medium is not limited to the configuration shown in FIG. Between the first substrate 11 first recording layer 12 _may be provided with enhanced layer and solvent layer of SiO 2, etc. ZnS-SiO _2. Further, 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. Furthermore, a protective layer may be formed on the reflective layer. In this case, the protective layer may be a layer having a function capable of protecting the recording layer and the reflective layer, and may be formed of, for example, an ultraviolet curable resin or a silicone resin. Moreover, you may provide a printing layer or a printing acceptance layer on the 2nd board | substrate 21 as needed.

[Physical format configuration]
Next, the configuration of the physical format in the optical disc of the reference form will be described.

  FIG. 2 shows a configuration example of the physical format of the information section (L0 layer) on the side close to the light incident side of the optical disc of the reference form. As shown in FIG. 2, the L0 layer 10 includes a preformat area 51 (hereinafter also referred to as a ROM area) and an information recording area 50 from the inner periphery side. In the area on the first substrate 11 corresponding to the ROM area 51, disc management information or the like is recorded in the form of embossed pits in advance, and in the area on the first substrate 11 corresponding to the information recording area 50, A light beam guide groove is formed. As shown in FIG. 2, the information recording area 50 includes an information recording / reproducing area 55 where additional information such as user information is recorded / reproduced, and information recording / reproducing areas provided on the inner and outer circumference sides of the information recording / reproducing area 55, respectively. Test areas 54 and 56 for determining recording conditions for the reproduction area 55, and buffer areas 53 and 57 provided on the inner circumference side of the test area 54 and the outer circumference side of the test area 56, respectively. The buffer regions 53 and 57 are provided in order to keep the recording layer thickness up to the region where recording is performed when the recording layer is formed by spin coating in the production of a dye-coated optical recording medium or the like. It has been. Further, as shown in FIG. 2, a mirror region 58 (mirror surface portion) is provided on the outer peripheral side of the buffer region 57 on the outer peripheral side.

  Further, in the optical disc of the reference form, as shown in FIG. 2, a transition area 52 is provided as a third area between the ROM area 51 and the information recording area 50. In the reference form, the region on the first substrate 11 corresponding to the transition region 50 is a mirror surface. The transition area 50 is an area provided between different format configurations. (1) The purpose of preventing crosstalk between the reproduction signal in the ROM area 51 and the reproduction signal in the information recording area 50, and (2) Dye application When a recording layer of an optical recording medium of the type is formed by spin coating on a substrate, a stabilization purpose for forming a uniform thickness of the recording layer by adjusting the disturbance of the coating liquid generated in the ROM area 51 This is an area provided for this purpose.

  On the other hand, the physical format of the L1 layer 20 adjacent to the L0 layer 10 via the spacer layer 30 may be configured without a ROM area. However, in the optical disk of the reference form, the same physical format configuration as that of the L0 layer 10 (see FIG. 2). However, the optical disk of the reference form was formed by shifting the radial position of each area in the physical format of the L0 layer 10 and the radial position of each area in the physical format of the L1 layer 20 as will be described later. In each of the L0 layer 10 and the L1 layer 20, a laminate of the constituent films shown in FIG. 1 is formed on the entire area of the disk including the ROM area, the information recording area, and the transition area.

  Corresponds to ROM area, transition area and information recording area (area where grooves are formed on the first substrate, including information recording / playback area, test area and buffer area) in each information section of the optical disc of the reference form An example of the concavo-convex pattern formed on the first substrate is schematically shown in FIG. As shown in FIG. 3, pits 31a are formed in the ROM area 31, and management information and the like of each information section are recorded by the pits 31a. In the information recording area 33, a groove 33a for guiding a light beam when recording user information or the like in the information recording area 33 is formed in a spiral shape. Information is recorded in the information recording area 33 by recording marks. The information recording area 33 may be provided with prepits for adding additional information such as address information, or the additional information may be recorded by meandering the groove. Then, the transition area 32 provided between the preformat area 31 and the information recording area 33 is usually left as a mirror surface portion where no groove or pit is provided. Even if the constituent films in each region have the same laminated structure, the reflectivity and transmittance of each region differ depending on the diffraction by embossed pits and grooves, the change in film thickness of the recording layer in the groove, and the like.

[Position of physical format between L0 and L1 layers]
In the optical disk of the reference form, when the light beam is irradiated to the range of the L1 layer test area and the information recording / reproducing area, which is the information part far from the light incident side, the transmittance of the L0 layer area through which the light beam passes Is formed by shifting the radial position of each region in the physical format of the L0 layer and the radial position of each region in the physical format of the L1 layer. Specifically, when the light beam is irradiated to the test area and the information recording / reproducing area of the L1 layer, the light beam does not pass through the ROM area, transition area, and mirror area of the L0 layer where the transmittance varies. In addition, the radial position of each physical format of the L0 layer and the L1 layer was adjusted.

The above contents are specifically expressed by mathematical formulas as follows. The radial position of the innermost track in the test area on the inner peripheral side of the L1 layer, the radial position of the outermost track in the test area on the outer peripheral side of the L1 layer, the radial position of the innermost guide groove in the information recording area of the L0 layer, The distances from the center of the optical disk at the radial position of the outermost peripheral guide groove in the information recording area of the L0 layer are R1, R2, R3, and R4, respectively, and the light beam is focused on the L1 layer. When the radius of the light beam is r,
R1 ≧ R3 + r (1)
R2 ≦ R4-r (2)
The radial positions of the physical formats of the L0 layer and the L1 layer are adjusted so that both of these relationships are established.

  FIG. 4 shows an example of the physical format positional relationship between the L0 layer and the L1 layer that satisfies the relationship of the above expressions (1) and (2). In the stage of designing the physical format positional relationship between the L0 layer and the L1 layer of the optical disk of the reference form, the above ((2) is considered in consideration of the eccentricity when the L0 layer and the L1 layer are bonded together. It is preferable to design using the formulas 1) ′ and (2) ′.

  4 is a schematic cross-sectional view of the physical format of each physical format of the L0 layer 10 and the L1 layer 20 that are adjacent via the spacer layer 30 (cross section AA in FIG. 2), from the left side to the right side of the drawing. The direction to go is the outer peripheral side direction. FIG. 4A shows a case where the lower limit condition of the above expression (1) is satisfied for the radial position R (1, TI, i) of the innermost track of the test area 64 on the inner circumference side of the L1 layer 20. It is the figure which showed the positional relationship of the physical format between L0 layer 10 and L1 layer 20 of FIG. That is, the radial position R (1, TI, i) of the innermost track of the test area 64 on the inner peripheral side of the L1 layer 20 and the radial position R (0 of the innermost guide groove of the information recording area 50 of the L0 layer 10). , G, i) between the distances R1 and R3 from the center of the optical disc and the radius r of the light beam in the L0 layer 10 when the light beam is focused on the L1 layer 20, the relationship of R1 = R3 + r It is the figure which showed the positional relationship between the physical formats of the L0 layer 10 and the L1 layer 20 when is materialized.

  On the other hand, FIG. 4B shows a case where the upper limit condition of the above equation (2) is satisfied with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. It is the figure which showed the positional relationship of the physical format between the L0 layer 10 and the L1 layer 20. FIG. That is, the radial position R (1, TO, o) of the outermost peripheral track of the test area 66 on the outer peripheral side of the L1 layer 20 and the radial position R (0, G, of the outermost peripheral guide groove of the information recording area 50 of the L0 layer 10 The relationship of R2 = R4-r is established between the distances R2 and R4 from the center of the optical disc in o) and the radius r of the light beam in the L0 layer 10 when the light beam is focused on the L1 layer 20. It is the figure which showed the positional relationship between the physical formats of the L0 layer 10 and the L1 layer 20 in the case of doing.

  In the optical disc in which the relationship of the radial positions as shown in FIG. 4A is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the innermost side of the test area 64 on the inner peripheral side of the L1 layer 20 R1 = R3 + r (the relationship of the above expression (1)) is established for the radial position R (1, TI, i) of the circumferential track. Therefore, as shown in FIG. 4A, even if the light beam 40 is focused on the innermost track position R (1, TI, i) of the test area 64, the light beam 40 is It does not pass through the transition area 52 and the ROM area 51.

  Further, as apparent from FIG. 4A, the relationship of R2 <R4-r with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. (Equation (2) above) holds, so that even if the light beam 40 is condensed at the outermost peripheral position R (1, TO, o) of the test region 66 on the outer peripheral side of the L1 layer 20, the light beam 40 Does not pass through the mirror region 58 on the outer peripheral side of the L0 layer 10.

  On the other hand, in the optical disc in which the relationship of the radial positions as shown in FIG. 4B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test area 66 on the outer and inner peripheral side of the L1 layer 20 is used. R2 = R4-r (the relationship of the above equation (2)) is established for the radial position R (1, TO, o) of the outermost track. Therefore, as shown in FIG. 4B, even if the light beam 40 is focused on the outermost track position R (1, TO, o) of the test area 66, the light beam 40 is reflected by the mirror of the L0 layer 10. Do not pass through region 58.

  Further, as apparent from FIG. 4B, the relationship of R1> R3 + r with respect to the radial position R (1, TI, i) of the innermost track of the test region 64 on the inner circumference side of the L1 layer 20 (Relationship of the above formula (1)) is established, so that even if the light beam 40 is condensed at the innermost peripheral position R (1, TI, i) of the test region 64 on the inner peripheral side of the L1 layer 20, The beam 40 does not pass through the transition region 52 and the ROM region 51 of the L0 layer 10.

  That is, the positional relationship shown in FIGS. 4 (a) and 4 (b) (the relationship of the above equations (1) and (2)) is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20. In the optical disk, the light beam condensed over the entire test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20 has a ROM area 51, a transition area 52, and a mirror area of the L0 layer 10 whose transmittance varies. 58, only the region (information recording region) 50 in which the groove of the L0 layer 10 is formed is passed. Since the information recording area 50 of the L0 layer 10 is an area where grooves are formed over the entire area (an area where a uniform concavo-convex pattern is formed), the light beam passing through the information recording area 50 of the L0 layer 10 The transmittance of 40 is substantially constant over the entire information recording area 50. Therefore, in the optical disc in which the radial position relationship as shown in FIGS. 4A and 4B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test area 64 of the L1 layer 20 is used. , 66 and the information recording / reproducing area 65 are transmitted only through the information recording area 50 of the L0 layer 10 having a substantially constant transmittance, so that the test areas 64, 66 and information recording / reproducing of the L1 layer 20 are recorded. Variation in the amount of light of the light beam 40 that reaches the region 65 can be suppressed.

  As described above, the optical disc of the reference form in which the positional relationship shown in FIG. 4 (the relationship of the above expressions (1) and (2)) is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20. Then, since the light beam 40 with very small light amount fluctuation is irradiated onto the inner and outer test areas 64 and 66 of the L1 layer 20, it is possible to reliably determine the optimum recording power for information recording. it can. Further, since the light amount fluctuation of the light beam reaching the information recording / reproducing area 65 of the L1 layer 20 is also very small, user information and the like are stably recorded in the information recording / reproducing area 65 of the L1 layer 20 with the optimum recording power. be able to. Therefore, by adjusting the positional relationship between the physical format of the L0 layer 10 and the physical format of the L1 layer 20 so as to satisfy the relationship of the above formulas (1) and (2) as in the optical disc of the reference form, Information recording / reproduction can be performed stably and reliably with respect to the information part (L1 layer) on the side far from the incident side of the light beam 40.

  In the reference embodiment, as described above, the optical disc having the test areas near both the inner periphery and the outer periphery of the second information recording area of the L1 layer has been described. However, the reference embodiment is not limited to this. When the test area is provided only in the vicinity of the inner circumference of the second information recording area of the L1 layer, the physical format of the L0 layer and the physical format of the L1 layer are set so that only the relationship of the above equation (1) is satisfied. The relationship between the radial positions may be adjusted, and when the test area is provided only in the vicinity of the outer periphery of the second information recording area of the L1 layer, L0 is set so that only the relation of the above expression (2) is established. The relationship of the radial position between the physical format of the layer and the physical format of the L1 layer may be adjusted. In any case, it is obvious that the effect can be obtained as in the case of the reference embodiment described above.

Embodiment The transmittance of the information portion (L0 layer) on the side close to the incident side of the light beam may vary depending on the recording state of the recording layer of the L0 layer, in addition to the influence of the substrate shape of the L0 layer. For example, when the recording layer of the L0 layer is formed of a dye material, the transmittance may change before and after recording information on the recording layer. In particular, in the test area for determining the recording power, since the recording power is changed from a lower one to a power larger than the optimum recording power, the transmittance variation becomes larger. In addition, since test writing is not necessarily performed over the entire test area, there may be a mixture of recorded areas and unrecorded areas in the test area. There is a possibility that the transmittance of the light beam passing through may fluctuate greatly.

  In the embodiment, a description will be given of a physical format of a single-sided, dual-layer type optical disc in consideration of a case where the light transmittance of the light beam passing through the L0 layer changes depending on not only the substrate shape in the L0 layer but also the recording state of the test area. To do. In the embodiment, as in the reference embodiment, the physical format of an optical disc in which test areas are provided both near the inner periphery and near the outer periphery in the second information recording area of the L1 layer will be described.

[Physical format configuration]
In order to solve the above-described problems, when the test writing is performed by irradiating the test area of the information portion (L1 layer) on the side far from the incident side of the light beam and the trial writing is performed, the information recording of the L1 layer is performed. Adjusts the positional relationship between the physical format of the L0 layer and the physical format of the L1 layer so that the light beam does not pass through the test region of the L0 layer when irradiating the reproduction area with a light beam to record / reproduce user information, etc. Just do it.

The above contents are specifically expressed by mathematical formulas as follows. The radial position of the innermost track in the test area on the inner peripheral side of the L1 layer, the radial position of the outermost track in the test area on the outer peripheral side of the L1 layer, and the innermost position where information is recorded in the information recording area of the L0 layer The distances from the center of the optical disk at the radial position of the circumferential track and the radial position of the outermost circumferential track where information is recorded in the information recording area of the L0 layer are R1, R2, R5 and R6. When r is the radius of the light beam in the L0 layer when the light beam is focused,
R1 ≧ R5 + r (3)
R2 ≦ R6-r (4)
The radial positions of the physical formats of the L0 layer and the L1 layer are adjusted so that both of these relationships are established. In the embodiment, except for changing the positional relationship between the physical format of the L0 layer and the physical format of the L1 layer, it has the same film configuration (see FIG. 1) as the single-sided dual layer type optical disc described in the reference mode. The physical format is the same (see FIG. 2).

  FIG. 5 shows an example of a physical format positional relationship between the L0 layer and the L1 layer that satisfies the relationship of the above expressions (3) and (4). In the stage of designing the physical format positional relationship between the L0 layer and the L1 layer of the optical disc of the embodiment, in consideration of the eccentricity when the L0 layer and the L1 layer are bonded, as in the reference embodiment, It is preferable to design using the above formulas (3) ′ and (4) ′.

  FIG. 5 is a schematic cross-sectional view of the physical format of each physical format of the L0 layer 10 and the L1 layer 20 that are adjacent via the spacer layer 30 (cross section AA in FIG. 2), from the left side to the right side of the drawing. The direction to go is the outer peripheral side direction. FIG. 5A shows a case where the lower limit condition of the above equation (3) is satisfied with respect to the radial position R (1, TI, i) of the innermost track in the test area 64 on the inner circumference side of the L1 layer 20. It is the figure which showed the positional relationship of the physical format between L0 layer 10 of this, and L1 layer. That is, information (additional information such as user information) is recorded in the radius position R (1, TI, i) of the innermost track in the test area 64 on the inner circumference side of the L1 layer 20 and in the information recording area 50 of the L0 layer 10. Distances R1 and R5 from the center of the optical disc at the radius position R (0, D, i) of the recorded innermost track (the innermost track position of the information recording / reproducing area 55 of the L0 layer 10 in FIG. 5) And the physical properties of the L0 layer 10 and the L1 layer 20 when the relationship R1 = R5 + r is established between the L1 layer 20 and the radius r of the light beam in the L0 layer 10 when the light beam 40 is focused on the L1 layer 20. It is the figure which showed the positional relationship between formats.

  On the other hand, FIG. 5B shows a case where the upper limit condition of the above expression (4) is satisfied with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. It is the figure which showed the positional relationship of the physical format between L0 layer 10 of this, and L1 layer. That is, the radial position R (1, TO, o) of the outermost track in the test area 66 on the outer peripheral side of the L1 layer 20 and the radial position of the outermost track on which information is recorded in the information recording area 50 of the L0 layer 10 Distances R2 and R6 from the center of the optical disc at R (0, D, o) (the outermost track position of the information recording / reproducing area 55 of the L0 layer 10 in FIG. 5), and the light beam 40 is focused on the L1 layer 20. FIG. 6 is a diagram showing the positional relationship between the physical formats of the L0 layer 10 and the L1 layer 20 when the relationship of R2 = R6-r is established between the radius r of the light beam in the L0 layer 10 when is there.

  In the optical disc in which the relationship of the radial positions as shown in FIG. 5A is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the innermost of the test area 64 on the inner peripheral side of the L1 layer 20 R1 = R5 + r (the relation of the above expression (3)) is established for the radial position R (1, TI, i) of the circumferential track. Therefore, as shown in FIG. 5A, even when the light beam 40 is focused on the innermost track position R (1, TI, i) of the test area 64, the light beam 40 is It does not pass through the test area 54, the transition area 52, and the ROM area 51.

  Further, as apparent from FIG. 5A, the relationship of R2 <R6-r with respect to the radial position R (1, TO, o) of the outermost track of the test region 66 on the outer peripheral side of the L1 layer 20. (Equation (4) above) holds, so that even if the light beam 40 is condensed at the outermost peripheral position R (1, TO, o) of the test region 66 on the outer peripheral side of the L1 layer 20, the light beam 40 Does not pass through the test area 56 and the mirror area 58 on the outer peripheral side of the L0 layer 10.

  On the other hand, in the optical disc in which the relationship of the radial positions as shown in FIG. 5B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the test area 66 on the outer and inner peripheral side of the L1 layer 20 is used. R2 = R6-r (the relationship of the above equation (4)) is established for the radial position R (1, TO, o) of the outermost track. Therefore, as shown in FIG. 5B, even if the light beam 40 is focused on the outermost track position R (1, TO, o) of the test area 66, the light beam 40 is It does not pass through the test area 56 and the mirror area 58 on the side.

  Further, as apparent from FIG. 5B, for the radial position R (1, TI, i) of the innermost track of the test region 64 on the inner circumference side of the L1 layer 20, the relationship of R1> R5 + r Since (the relationship of the above expression (3)) is established, even if the light beam 40 is condensed at the innermost peripheral position R (1, TI, i) of the test area 64 on the inner peripheral side of the L1 layer 20, the light The beam 40 does not pass through the test area 54, the transition area 52, and the ROM area 51 on the inner circumference side of the L1 layer 10.

  That is, the positional relationship shown in FIGS. 5 (a) and 5 (b) (the relationship of the above expressions (3) and (4)) is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20. In the optical disk, the light beam condensed over the entire test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20 has a ROM area 51, a transition area 52, and a mirror area of the L0 layer 10 whose transmittance varies. It does not pass not only 58 but also the test areas 54 and 56 whose transmittance may vary depending on the recording state, and passes only the information recording / reproducing area 55 of the L0 layer 10. Grooves are formed throughout the information recording / reproducing area 55 of the L0 layer 10, and information is recorded with a predetermined recording power. In addition, since information recording is normally performed from the L0 layer 10, at the time when information is recorded in the L1 layer 20, user information and the like are recorded uniformly over the entire information recording / reproducing area 55 of the L0 layer 10. is there. Therefore, the transmittance of the light beam passing through the information recording / reproducing area 55 of the L0 layer 10 becomes substantially uniform. Therefore, in the optical disk of the present embodiment in which the radial position relationship as shown in FIGS. 5A and 5B is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20, the L0 layer 10 Even when the light transmittance varies depending on the recording state of the test areas 54 and 56 as well as the shape of the first substrate, the test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20 are irradiated. Since the light beam 40 passes only through the information recording / reproducing area 55 of the L0 layer 10 having a substantially constant transmittance, the light quantity variation of the light beam 40 that reaches the test areas 64 and 66 and the information recording / reproducing area 65 of the L1 layer 20. Can be suppressed.

  As described above, the optical disc of the embodiment in which the positional relationship shown in FIG. 5 (the relationship of the above expressions (3) and (4)) is established between the physical format of the L0 layer 10 and the physical format of the L1 layer 20. Then, even in the case where the light transmittance varies depending on the recording state of the test areas 54 and 56 as well as the shape of the first substrate of the L0 layer 10, the light beam 40 with a very small light amount variation is generated by the L1 layer 20. Since the test areas 64 and 66 on the inner peripheral side and the outer peripheral side are irradiated, the optimum recording power for information recording can be determined reliably.

  Further, since the light amount fluctuation of the light beam reaching the information recording / reproducing area 65 of the L1 layer 20 is also very small, user information and the like are stably recorded in the information recording / reproducing area 65 of the L1 layer 20 with the optimum recording power. be able to.

  Therefore, the relationship of the radial positions of the physical format of the L0 layer 10 and the physical format of the L1 layer 20 is established by the above formulas (3) and (4) as in the single-sided dual layer type optical disc of this embodiment. By adjusting so, it is possible to stably record and reproduce information with respect to the information portion (L1 layer) on the side far from the incident side of the light beam 40.

[Reference Example 1]
In Reference Example 1, a single-sided, dual-layer write-once optical disc compatible with a red laser having a recording layer formed of a dye material was produced. In the optical disc of this example, the physical format of each information unit was adjusted so that the positional relationship of the physical format between the L0 layer and the L1 layer satisfied the above expressions (1) and (2). The film configuration of the optical disk in this example was the same as the film configuration shown in FIG.

  Note that there are mainly two types of methods for producing a single-sided two-layer type optical recording medium as shown in FIG. The first method is a method of sequentially laminating two recording layers of the L0 layer and the L1 layer on a single substrate. The second method is a method in which the recording layers of the L0 layer and the L1 layer are laminated on different substrates and then bonded together. In the case of manufacturing by the second method, the stacking order of the stacked films on the substrate in the L1 layer needs to be reversed from the stacking order of the L0 layer. The optical disk of Reference Example 1 can exert its effect even if any of the above production methods is used, but in this example, the latter method was adopted.

[Preparation of test disk for transmittance evaluation and transmittance measurement]
First, before describing the details of the optical disc of Reference Example 1, the relationship between the physical format of the L0 layer and the transmittance in a single-sided dual-layer type red laser compatible optical disc using a dye material for the recording layer will be described. Therefore, in order to investigate the relationship between the physical format of the L0 layer and the transmittance, a single-sided, dual-layer type test disc (hereinafter also referred to as a transmittance evaluation test disc) having the same physical format as the DVD-R is manufactured. did.

  As shown in FIG. 7, the physical format of the L0 layer of the test disk for transmittance evaluation includes a ROM area 91, a transition area 92, and an information recording area 93 (including a buffer area, a test area, and an information recording / reproducing area) from the inner periphery side. ). Embossed pits were formed in the region on the substrate of the L0 layer corresponding to the ROM region 91, and grooves were formed on the substrate corresponding to the information recording region 93. The region on the substrate of the L0 layer corresponding to the transition region 92 is a mirror surface. Specifically, DVD-ROM data was recorded by forming a pit row having a track pitch of 0.74 μm and a half-value width of 0.32 μm in an area on the substrate of the L0 layer corresponding to the ROM area 91. On the substrate corresponding to the information recording area 93, a groove having a track pitch of 0.74 nm, a half-value width of 0.32 μm, and a depth of 170 nm was formed. The radial width of the transition region 92 was about 100 μm. On the other hand, a groove (groove) having a track pitch of 0.74 μm, a half-value width of 0.37 μm, and a depth of 30 nm was formed on the substrate surface of the L1 layer of the test disk for transmittance evaluation from the innermost circumference to the outermost circumference. The film configuration of the transmittance evaluation test disk was as shown in FIG.

  Furthermore, here, as a test disk serving as a reference for transmittance evaluation, a test disk (hereinafter referred to as a reference disk) in which a dummy substrate (a substrate on which the concave / convex pattern is not formed) is bonded to the L1 layer instead of the L0 layer. A test disk was also produced.

  Next, a method for producing a test disk for transmittance evaluation will be described with reference to FIG. The method for producing the single-sided, dual-layer type optical disc of Reference Example 1 is the same as the method for producing a test disk for transmittance evaluation described below.

  First, the L0 layer 10 was produced as follows. A stamper in which a concavo-convex pattern corresponding to a pit row and a groove (groove) pattern formed on the first substrate 11 is formed. Next, the manufactured stamper was mounted on an existing injection molding machine, and an optical information recording medium grade polycarbonate resin was injection molded to obtain the first substrate 11 of the L0 layer 10 of the test disk. Here, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was produced.

  Next, a tetrafluoropropanol solution having a concentration of 1.3% by weight of an azo dye represented by the following chemical formula (Chemical Formula 1) was applied to the uneven pattern forming surface of the first substrate 11 by a spin coating method. 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 spin coating, 0.5 g of a dye solution is supplied onto the first substrate 11 rotating at a rotation speed of 100 rpm by a dispenser, and then the first substrate 11 is rotated from 1000 rpm to 3000 rpm, and finally rotated at 5000 rpm for 2 seconds. It was. At this time, the solution was applied so that the thickness was 130 nm at the groove portion. Subsequently, the 1st board | substrate 11 which apply | coated the said pigment | dye material was dried at 70 degreeC for 1 hour, and also it cooled at room temperature for 1 hour. Thus, the first recording layer 12 was formed on the first substrate 11.

  Further, an Ag film having a thickness of 160 nm was formed as the first reflective layer 13 on the first recording layer 12 by sputtering. Thus, the L0 layer 10 was produced.

  Next, the L1 layer 20 was produced as follows. First, the second substrate 21 of the L1 layer 20 was produced in the same manner as the first substrate 11 of the L0 layer 10. The second substrate 21 of the L1 layer 20 is a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm. As described above, the substrate surface has a track pitch of 0.74 μm and a half width from the inner periphery side to the outer periphery side. Grooves having a value width of 0.37 μm and a depth of 30 nm were formed. In the L1 layer 20, since the laser light is irradiated from the groove pattern forming surface side of the second substrate 21, the groove pattern is formed in a spiral in the direction opposite to that of the L0 layer 10 in consideration thereof. did. In the L1 layer 20, the constituent layers were formed on the groove pattern forming surface of the second substrate 21 in the reverse order to the L0 layer 10.

First, an Ag film having a thickness of 160 nm was formed as the second reflective layer 23 on the second substrate 21 by sputtering. Next, a tetrafluoropropanol solution having an azo dye represented by the above chemical formula (Chemical Formula 1) at a concentration of 1.3% by weight is applied onto the second reflective layer 23 by spin coating, and the second recording layer 22 is applied. Formed. At this time, the above solution was applied under the same conditions as those for forming the first recording layer 12 of the L0 layer 10 described above to form the second recording layer 22. The film thickness was 200 nm. Subsequently, the 2nd board | substrate 21 which apply | coated the said pigment | dye material was dried at 70 degreeC for 1 hour, and also it cooled at room temperature for 1 hour. Next, a ZnS—SiO ₂ film having a thickness of 10 nm was formed as the interface layer 24 on the second recording layer 22 by sputtering. In this way, the L1 layer 20 was formed.

  Next, the L0 layer 10 and the L1 layer 20 produced as described above were bonded together as follows. First, a UV resin material was applied as a spacer layer 30 on the first reflective layer 13 of the L0 layer 10 by spin coating. Further, the L1 layer 20 was placed thereon. At this time, the L1 layer 20 was placed on the spacer layer 30 so that the first reflective layer 13 of the L0 layer 10 and the interface layer 24 of the L1 layer 20 face each other with the spacer layer 30 interposed therebetween. Next, in this state, UV irradiation was performed from the first substrate 11 side of the L0 layer 10 to cure the UV resin material, and the L0 layer 10 and the L1 layer 20 were bonded together. The thickness of the spacer layer 30 is preferably 50 to 55 μm, and in Reference Example 1, it is 55 μm. A test disk for transmittance evaluation was produced as described above. The reference test disk was produced by the same method as above except that a dummy substrate was bonded to the L1 layer instead of the L0 layer.

  The transmittance of the L0 layer in the transmittance evaluation test disk and the reference test disk prepared by the above-described manufacturing method was measured. The transmittance of the L0 layer in the groove (information recording area) was measured in an unrecorded state and a state after recording. The recording conditions at this time were such that the linear velocity was a linear velocity equivalent to double the speed of DVD and the recording power was 12 mW. The wavelength of the laser beam used for the measurement was 650 nm, and the numerical aperture of the aperture lens was NA = 0.6. The transmittance was measured using parallel light having a wavelength of 650 nm. The evaluation results of the transmittance of the L0 layer are shown in Table 1. The transmittance in the column “None” in Table 1 is the transmittance of the reference test disk.

  Furthermore, the optimum value of the recording power in the L1 layer when the L1 layer was irradiated with laser light through each region of the L0 layer was examined. At that time, the recording pulse strategy was the same, and the recording power without asymmetry was set as the optimum recording power. The results are shown in Table 2. The optimum recording power in the “None” column in Table 2 is the optimum recording power of the reference test disk.

  As is clear from the results in Tables 1 and 2, it was found that the transmittance of the L0 layer varies depending on the shape of the first substrate of the L0 layer through which the light beam passes, and the optimum recording power in the L1 layer also changes. Further, as apparent from Table 1, in this example, since the dye material is used for the recording layer, it has been found that the transmittance of the L0 layer varies somewhat depending on the recording state of the first recording layer. Therefore, in the case where information is recorded / reproduced by irradiating the test area and the information recording / reproducing area of the L1 layer with the light beam, the transmittance of the L0 layer area through which the light beam passes is kept constant. It became clear that this was important.

[Configuration of Optical Disc of Reference Example 1]
In Reference Example 1, the L0 layer and the L1 layer are both formed in the physical format as shown in FIG. 2, and the positional relationship of each area in the physical format between the L0 layer and the L1 layer has a relationship as shown in Table 3. A two-layer type optical disc was produced. Table 3 shows the start radius position and the end radius position of each area constituting the physical format of the L0 layer and the L1 layer. The numerical values shown in Table 3 are values at the design stage of the optical disc, the numerical values described in the L0 layer column are distances from the center of the L0 layer, and the numerical values described in the L1 layer column are the center of the L1 layer. It is the distance from.

  In the optical disc of this example, the track pitch of the L1 layer is set to L0 so that the number of tracks in the L0 layer and the number of tracks in the L1 layer are the same, that is, the recording capacities of the L0 layer and the L1 layer are the same. Narrower than the track pitch of the layer. Specifically, the track pitch of the L0 layer was 0.74 μm, and the track pitch of the L1 layer was 0.736 μm. Note that the dimensions of the grooves formed in the area on the first substrate corresponding to the information recording area of the L0 layer in the optical disk of this example are the same dimensions as the disk for transmittance evaluation (track pitch 0.74 μm, half width 0). .32 μm and depth 170 nm), and the dimensions of the grooves formed in the region on the second substrate corresponding to the information recording region of the L1 layer were track pitch 0.736 μm, half-value width 0.37 μm, and depth 30 nm. .

  In the optical disc of this example, the physical format configurations of the L0 layer and the L1 layer are made the same, the radial position of each area in the physical format of the L0 layer and the L1 layer is adjusted as shown in Table 3, and the L1 layer The structure is the same as that of the above-described transmittance evaluation test disk except that the track pitch between the L0 layer and the L0 layer is changed. The optical disk of this example was manufactured by the same method as the above-described transmittance evaluation test disk.

  As clarified in the measurement result of the above-described transmittance (Table 1), the transmittance of the L0 layer varies greatly depending on the shape of the first substrate of the L0 layer through which the light beam passes. A light beam condensed over the entire test area and information recording / reproduction area of the L1 layer does not pass through the ROM area, transition area, and mirror area of the L0 layer where the transmittance varies, and L0 has a small variation in transmittance. The positional relationship of the respective areas in the physical format of the L0 layer and the L1 layer was adjusted so as to pass only through the information recording area of the layer (area where the groove was formed).

In the optical disk of this example, as is clear from Table 3, at the design stage, from the center of the L1 layer at the radial position R (1, TI, i) of the innermost track in the test area on the inner periphery side of the L1 layer. Distance R1 ′ = 23.910 mm, distance R2 ′ = 57.920 mm from the center of the L1 layer at the radial position R (1, TO, o) of the outermost track of the outermost track of the L1 layer, information recording of the L0 layer The distance R3 ′ from the center of the L0 layer at the radial position R (0, G, i) of the innermost circumferential guide groove in the region is equal to 23.810 mm, and the radial position R ( The distance from the center of the L0 layer at 0, G, o) is R4 ′ = 58.020 mm. In addition, a laser beam having a wavelength of 650 nm was used for recording / reproduction of the optical disk of this example, and a lens having a numerical aperture NA = 0.6 was used as the aperture lens. Further, the spacer layer of the optical disk is made of a material having a refractive index ns = 1.5 at a wavelength of 650 nm, and the thickness D is 55 μm. Therefore, in the optical disk of this example, the laser beam is condensed on the L1 layer. The radius r of the laser beam in the L0 layer when it is being is about 20 μm. In this example, the specification value RR _pp of the eccentricity when the L0 layer and the L1 layer are bonded is set to 70 μm.

Therefore, in the optical disc of this example, at the design stage, the radial position R (1, TI, i) of the innermost track in the test area on the inner circumference side of the L1 layer and the outermost circumference of the test area on the outer circumference side of the L1 layer. The distances R1 ′ and R2 ′ from the center of the L1 layer at the track radial position R (1, TO, o), the radial position R (0, G, i) of the innermost guide groove in the information recording area of the L0 layer, and Distances R3 ′ and R4 ′ from the center of the L0 layer at the radial position R (0, G, o) of the outermost guide groove in the information recording area of the L0 layer, the radius r of the laser beam in the L0 layer, and the amount of eccentricity RR _p The relationship of the above expressions (1) ′ and (2) ′ is established between _−p and _-p . Therefore, in the optical disc of this example manufactured with the above design content, the physical format positional relationship between the L0 layer and the L1 layer satisfies the above expressions (1) and (2). Therefore, in the optical disk manufactured in this example, the L0 layer ROM area, transition area, and mirror area where the light beam condensed over the entire test area and information recording / reproduction area of the L1 layer varies in transmittance. And only passes through the information recording area of the L0 layer where the transmittance fluctuation is very small.

[Reference Example 2]
In Reference Example 2, the L0 layer and the L1 layer are both formed at the same track pitch, and as shown in Table 4, the single-sided two-layer in which the radial positions of the regions in the physical format of the L0 layer and the L1 layer are the same A type optical disc was produced. That is, an optical disc was produced in which the physical format positional relationship between the L0 layer and the L1 layer did not satisfy the above expressions (1) and (2). The configuration is the same as that of the optical disc of Reference Example 1 except that the track pitches of the L0 layer and the L1 layer are the same, and the radial positions of the respective areas in the physical format of the L0 layer and the L1 layer are the same. The same method was used. In addition, the radial position described in Table 4 is a value at the design stage, the numerical value described in the L0 layer column is the distance from the center of the L0 layer, and the numerical value described in the L1 layer column is from the center of the L1 layer. Distance.

[Recording characteristics]
Each of the five single-sided dual-layer type optical discs of Reference Examples 1 and 2 was prototyped, recorded on the L0 layer, and then recorded on the L1 layer. As a result, the optical disk of Reference Example 1 was able to record normally on the L1 layer in one recording operation for all five discs. However, in the optical disc of Reference Example 2, there is one disc that can be normally recorded in the L1 layer by one recording operation, and three discs that can be normally recorded in the L1 layer after repeating the recording operation a plurality of times. One of the images could not be recorded. From this result, as in the optical disc of Reference Example 1, the positional relationship between the physical format of the L0 layer 10 and the physical format of the L1 layer 20 is adjusted so that the relationship of the above expressions (1) and (2) is established. Thus, it was found that information recording / reproduction with respect to the L1 layer can be performed stably and with high reliability.

  Further, when the test area on the inner circumference side of the L1 layer of the optical disk in which the recording operation was retried among the optical disks of Reference Example 2 and the optical disk that could not be recorded was examined, there was an amplitude fluctuation of one cycle per track circumference. I understood. This is because the laser light reaching the test area on the inner peripheral side of the L1 layer has passed through the mirror area and the ROM area of the L0 layer due to the influence of eccentricity when the L0 layer and the L1 layer are bonded together.

  In Example 1, a write-once type optical disc corresponding to a blue laser of a single-sided two-layer type in which a recording layer was formed of a dye material was produced. In the optical disk of this example, since the recording layer is formed of a dye material, as described in Table 1 of Reference Example 1, information is recorded / reproduced with respect to the information portion (L1 layer) on the side far from the light incident side. When performing the above, there is a possibility that the transmittance of the laser beam will slightly vary depending on the recording state of the test area of the information portion (L0 layer) closer to the light incident side. Therefore, in the optical disc of this example, further considering this point, the physical format of each information section is set so that the positional relationship between the physical formats of the L0 layer and the L1 layer satisfies the above expressions (3) and (4). It was adjusted. The film configuration of the optical disk in this example was the same as the film configuration shown in FIG.

[Preparation of test disk for transmittance evaluation and transmittance measurement]
First, before describing the details of the optical disk of Example 1, as in Reference Example 1, the physical format and transmittance of the L0 layer in a single-sided, dual-layer blue laser compatible optical disk using a dye material for the recording layer The relationship will be described. Therefore, a single-sided, two-layer type test disk (hereinafter also referred to as a transmittance evaluation test disk) for examining the relationship between the physical format of the L0 layer and the transmittance was prepared. Further, a test disk (hereinafter also referred to as a reference test disk) in which a dummy substrate was bonded to the L1 layer instead of the L0 layer was produced as a reference disk for transmittance evaluation.

  As shown in FIG. 7, the physical format of the L0 layer of the test disk for transmittance evaluation includes a ROM area 91, a transition area 92, and an information recording area 93 (including a buffer area, a test area, and an information recording / reproducing area) from the inner periphery side. ). Embossed pits were formed in the region on the substrate of the L0 layer corresponding to the ROM region 91, and grooves were formed in the region on the substrate corresponding to the information recording region 93. The region on the substrate of the L0 layer corresponding to the transition region 92 is a mirror surface. Specifically, ROM data was recorded by forming a pit row having a track pitch of 400 nm and a half-value width of 160 nm in an area on the substrate of the L0 layer corresponding to the ROM area 91. A groove having a track pitch of 400 nm, a half-value width of 220 nm, and a depth of 70 nm was formed in an area on the substrate corresponding to the information recording area 93. The radial width of the transition region 92 was about 10 μm. On the other hand, a groove (groove) having a track pitch of 400 nm, a half-value width of 220 nm, and a depth of 15 nm was formed on the substrate surface of the L1 layer of the test disk for transmittance evaluation from the innermost circumference to the outermost circumference of the disk. The film configuration of the transmittance evaluation test disk in this example was the configuration shown in FIG.

  Next, a method for producing a test disk for transmittance evaluation will be described with reference to FIG. The production method of the single-sided, double-layer type optical disc of Example 1 is the same as the production method of the transmittance evaluation test disc described below.

  First, the L0 layer 10 was produced as follows. A stamper in which a concavo-convex pattern corresponding to a pit row and a groove (groove) pattern formed on the first substrate 11 is formed. Next, the manufactured stamper was mounted on an existing injection molding machine, and an optical information recording medium grade polycarbonate resin was injection molded to obtain the first substrate 11 of the L0 layer 10 of the test disk. Here, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was produced as the first substrate 11.

  Next, a tetrafluoropropanol solution containing an azo dye represented by the following chemical formula (Chemical Formula 2) at a concentration of 0.7% by weight is applied onto the uneven pattern forming surface of the first substrate 11 by spin coating. did. 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 spin coating, 0.5 g of a dye solution is supplied onto the first substrate 11 rotating at a rotation speed of 100 rpm by a dispenser, and then the first substrate 11 is rotated from 1000 rpm to 3000 rpm, and finally rotated at 5000 rpm for 2 seconds. It was. At this time, the solution was applied so that the groove portion had a thickness of 110 nm. Subsequently, the 1st board | substrate 11 which apply | coated the said pigment | dye material was dried at 80 degreeC for 1 hour, and also it cooled at room temperature for 1 hour. Thus, the first recording layer 12 was formed on the first substrate 11.

  Further, an Ag film having a thickness of 10 nm was formed as the first reflective layer 13 on the first recording layer 12 by sputtering. Thus, the L0 layer 10 was produced.

  Next, the L1 layer 20 was produced as follows. First, the second substrate 21 of the L1 layer 20 was produced in the same manner as the first substrate 11 of the L0 layer 10. In the L1 layer 20, since the laser light is irradiated from the groove pattern forming surface side of the second substrate 21, the groove pattern is formed in a spiral in the opposite direction to the L0 layer in consideration thereof. . In the L1 layer 20, the constituent films were formed on the groove pattern forming surface of the second substrate 21 in the reverse order to the L0 layer 10.

First, an Ag film having a thickness of 130 nm was formed as the second reflective layer 23 on the second substrate 21 by sputtering. Next, a tetrafluoropropanol solution containing an azo dye represented by the above chemical formula (Chemical Formula 2) at a concentration of 0.7% by weight is applied onto the second reflective layer 23 by a spin coating method, and then the second recording layer. 22 was formed. At this time, the second recording layer 22 was formed by applying the solution under the same conditions as those for forming the first recording layer 12 of the L0 layer 10. The film thickness was 100 nm. The 2nd board | substrate 21 which apply | coated the said pigment | dye material was dried at 80 degreeC for 1 hour, and also cooled at room temperature for 1 hour. Next, a ZnS—SiO ₂ film having a thickness of 10 nm was formed as the interface layer 24 on the second recording layer 22 by sputtering. In this way, the L1 layer 20 was formed.

  Next, the L0 layer 10 and the L1 layer 20 produced as described above were bonded together as follows. First, a UV resin material was applied as a spacer layer 30 on the first reflective layer 13 of the L0 layer 10 by spin coating. Further, the L1 layer 20 was placed thereon. At this time, the L1 layer 20 was placed on the spacer layer 30 so that the first reflective layer 13 of the L0 layer 10 and the interface layer 24 of the L1 layer 20 face each other with the spacer layer 30 interposed therebetween. Next, in this state, UV irradiation was performed from the first substrate 11 side of the L0 layer 10 to cure the UV resin material, and the L0 layer 10 and the L1 layer 20 were bonded together. The thickness of the spacer layer 30 is preferably 15 to 25 μm, and in this embodiment, it is set to 25 μm. A test disk for transmittance evaluation was produced as described above. The reference test disk was produced by the same method as above except that a dummy substrate was bonded to the L1 layer instead of the L0 layer.

  The transmittance of the L0 layer in the transmittance evaluation test disk and the reference test disk prepared by the above-described manufacturing method was measured. The transmittance of the L0 layer in the groove (information recording area) was measured in an unrecorded state and a state after recording. The recording conditions in this measurement were a linear velocity of 6.61 m / s and a recording power of 9.0 mW. The evaluation results are shown in Table 5. The wavelength of the laser beam used for the measurement was 405 nm, and the numerical aperture of the aperture lens was NA = 0.65. The transmittance measurement was performed using parallel light having a wavelength of 405 nm. The transmittance in the column “None” in Table 5 is the transmittance of the reference test disk.

  Furthermore, the optimum value of the recording power in the L1 layer when the L1 layer was irradiated with laser light through each region of the L0 layer was examined. At that time, the recording pulse strategy was the same, and the recording power without asymmetry was set as the optimum recording power. The results are shown in Table 6. The optimum recording power in the “None” column in Table 6 is the optimum recording power of the reference test disk.

  As is clear from the results of Tables 5 and 6, when the recording layer is formed of a dye material, the light beam is also applied to the laser beam having a wavelength of 405 nm, as in the transmittance evaluation result of Reference Example 1. It has been found that the transmittance of the L0 layer varies depending on the shape of the first substrate of the L0 layer that passes through, and the optimum recording power in the L1 layer also changes. Further, as is apparent from Table 5, it was found that the transmittance of the L0 layer varies somewhat depending on the recording state of the first recording layer. Therefore, in the case where information is recorded / reproduced by irradiating the test area and the information recording / reproducing area of the L1 layer with the light beam, the transmittance of the L0 layer area through which the light beam passes is kept constant. It became clear that this was important.

[Configuration of Optical Disc of Example 1]
In the first embodiment, the L0 layer and the L1 layer are both formed in a physical format as shown in FIG. 2, and the positional relationship of the physical format between the L0 layer and the L1 layer has a relationship as shown in Table 7 An optical disc was produced. Table 7 shows the start radius position and the end radius position of each area constituting the physical format of the L0 layer and the L1 layer. In addition, the radial position described in Table 7 is a value at the design stage, the numerical value described in the L0 layer column is the distance from the L0 layer center, and the numerical value described in the L1 layer column is from the L1 layer center. Distance.

  Further, in the optical disk of this example, in order to make the number of tracks in the L1 layer and the number of tracks in the L0 layer the same, that is, in order to make the recording capacities of the L0 layer and the L1 layer the same, In order to adjust the end radius position, the track pitch of the L1 layer was made narrower than the track pitch of the L0 layer. Specifically, the track pitch of the L0 layer was 400 nm, and the track pitch of the L1 layer was 395 nm. The dimensions of the grooves formed in the region on the first substrate corresponding to the information recording region of the L0 layer in the optical disc of this example are the same as those of the transmittance evaluation disc (track pitch 400 nm, half-value width 220 nm, and depth 70 nm). And the dimensions of the grooves formed in the region on the second substrate corresponding to the information recording region of the L1 layer were a track pitch of 395 nm, a half-value width of 218 nm, and a depth of 15 nm.

  In the optical disc of this example, the physical format configurations of the L0 layer and the L1 layer were made the same, the radial position of each area in the physical format of the L0 layer and the L1 layer was adjusted as shown in Table 7, and Except for changing the track pitch of the L1 layer and the L0 layer, the structure was the same as the above-described transmittance evaluation test disk. The optical disk of this example was manufactured by the same method as the above-described transmittance evaluation test disk.

  As is clear from the measurement results of the transmittance described above (results shown in Table 5), when a dye material is used for the L0 recording layer, the transmittance varies depending on the recording state of the recording layer. In the optical disc of this example, the light beam condensed over the entire test area and information recording / reproduction area of the L1 layer passes through the ROM area, transition area, mirror area, and test area of the L0 layer whose transmittance varies. The physical properties of the L0 layer and the L1 layer so that only the region (information recording / reproducing region 55 in FIG. 2) in which the information of the L0 layer (additional information such as user information) with little variation in transmittance is recorded is recorded. Adjusted the positional relationship of each area in the format.

In the optical disk of this example, as is clear from Table 7, at the design stage, the distance from the center of the L1 layer at the radial position R (1, TI, i) of the innermost track of the innermost test area of the L1 layer R1 ′ = 24.064 mm, distance R2 ′ = 57.857 mm from the center of the L1 layer at the radial position R (1, TO, o) of the outermost track of the test area on the outer periphery side of the L1 layer, information recording / reproduction of the L0 layer The distance R5 ′ = 24.000 mm from the center of the L0 layer at the radial position R (0, D, i) of the innermost track of the area, and the radial position R (0 of the outermost track of the information recording / reproducing area of the L0 layer , D, o), the distance R6 ′ from the L0 center is 57.921 mm. In addition, a laser beam having a wavelength of 405 nm was used for recording / reproduction of the optical disk of this example, and a lens having a numerical aperture NA = 0.65 was used as the aperture lens. Further, since the spacer layer of the optical disk is formed of a material having a refractive index ns = 1.5 at a wavelength of 405 nm and the thickness D is 25 μm, the laser light is condensed on the L1 layer in the optical disk of this example. The radius r of the laser beam in the L0 layer when it is on is 11.5 μm. Further, in this example, the specification value RR _pp of the eccentricity when the L0 layer and the L1 layer are bonded is set to 50 μm.

Therefore, in the optical disc of this example, at the design stage, the radial position R (1, TI, i) of the innermost track in the test area on the inner circumference side of the L1 layer and the outermost circumference of the test area on the outer circumference side of the L1 layer. Distances R1 ′ and R2 ′ from the center of the L1 layer at the radial position R (1, TO, o) of the track, the radial position R (0, D, i) of the innermost track in the information recording / reproducing area of the L0 layer, and Specification of distances R5 ′ and R6 ′ from the center of the L0 layer at the radial position R (0, D, o) of the outermost track of the information recording / reproducing area of the L0 layer, the radius r of the laser beam in the L0 layer, and the amount of eccentricity The relationship of the above expressions (3) ′ and (4) ′ is established between the value RR _p-p . Therefore, in the optical disc of this example manufactured with the above design content, the positional relationship of the physical format between the L0 layer and the L1 layer satisfies the above expressions (3) and (4). Therefore, in the optical disc manufactured in this example, the L0 layer ROM region, transition region, mirror region where the light beam condensed over the entire test region and information recording / reproducing region of the L1 layer varies in transmittance. In addition, it does not pass through the test area, and passes only through the information recording / reproducing area of the L0 layer where the transmittance fluctuation is very small.

[Comparative Example 1]
In Comparative Example 1, the L0 layer and the L1 layer are both formed at the same track pitch, and as shown in Table 8, each surface in the physical format of the L0 layer and the L1 layer has the same radial position in two layers on one side. A type optical disc was produced. That is, an optical disc was produced in which the physical format positional relationship between the L0 layer and the L1 layer did not satisfy the above expressions (3) and (4). In addition, except that the track pitches of the L0 layer and the L1 layer are the same, and the radial position of each region in the physical format of the L0 layer and the L1 layer is the same, the optical disc of the first embodiment has the same configuration. The same method was used. In addition, the radial position described in Table 8 is a value at the design stage, the numerical value described in the column of the L0 layer is the distance from the center of the L0 layer, and the numerical value described in the column of the L1 layer is from the center of the L1 layer. Distance.

[Recording characteristics]
Each of the five single-sided, dual-layer type optical discs of Example 1 and Comparative Example 1 was prototyped, recorded on the L0 layer, and then recorded on the L1 layer. As a result, the optical disk of Example 1 was able to normally record on the L1 layer with a single recording operation on all five discs. However, in the optical disc of Comparative Example 1, one disc was successfully recorded by one recording operation on the L1 layer, and three discs were successfully recorded on the L1 layer after repeating the recording operation a plurality of times. The remaining one could not be recorded. From this result, as in the optical disc of Example 1, the positional relationship between the physical format of the L0 layer 10 and the physical format of the L1 layer 20 is adjusted so that the relationship of the above expressions (3) and (4) is established. Thus, it was found that information recording / reproduction with respect to the L1 layer can be performed stably and with high reliability.

  Further, when the test area on the inner circumference side of the L1 layer of the optical disk of Comparative Example 1 in which the recording operation was retried and the optical disk that could not be recorded was examined, there was an amplitude fluctuation of one cycle per track circumference. I understood. This is because the laser light reaching the test area on the inner peripheral side of the L1 layer has passed through the mirror area and the ROM area of the L0 layer due to the influence of eccentricity when the L0 layer and the L1 layer are bonded together.

[Reference Example 3]
In Reference Example 3, a rewritable optical disc corresponding to a blue laser of a single-sided dual layer type in which a recording layer was formed of a phase change material was produced. In the optical disc of this example, since the recording layer is formed of a phase change material, as will be described later, when recording / reproducing information on the information portion (L1 layer) on the side far from the light incident side, Although the laser beam transmittance varies depending on the substrate shape of the information portion (L0 layer) on the side closer to the incident side, the laser beam transmittance hardly varies depending on the recording state of the test area. Therefore, in the optical disk of this example, the physical format of each information section is adjusted so that the positional relationship of the physical formats between the L0 layer and the L1 layer satisfies the above expressions (1) and (2).

  A schematic cross-sectional view of the single-sided, double-layered rewritable optical disk produced in this example is shown in FIG. As shown in FIG. 8, the optical disc 300 in this example has a structure in which an L0 layer 70 (first information portion) and an L1 layer 80 (second information portion) are bonded together via a spacer layer 90.

  As shown in FIG. 8, the L0 layer 70 is formed on the first substrate 71, the first protective layer 72, the first interface layer 73, the first recording layer 74, the second interface layer 75, the second protective layer 76, The first reflective layer 77 and the third protective layer 78 are sequentially stacked. Further, as shown in FIG. 8, the L1 layer 80 is formed on the second substrate 81 on the second reflective layer 87, the second protective layer 86, the second interface layer 85, the second recording layer 84, and the first interface layer 83. The first protective layer 82 is sequentially stacked. The L0 layer 70 and the L1 layer 80 are bonded via the spacer layer 90 so that the third protective layer 78 of the L0 layer 70 and the first protective layer 82 of the L1 layer 80 face each other. In this example, as shown in FIG. 8, the laser beam 40 is incident from the first substrate 71 side of the L0 layer 70.

[Preparation of test disk for transmittance evaluation and transmittance measurement]
First, before explaining the details of the optical disc of Reference Example 3, in this example as well, the physical format and transmittance of the L0 layer in the single-sided dual-layer blue laser compatible optical disc using a phase change material for the recording layer The relationship will be described. Therefore, a single-sided, two-layer type test disk (hereinafter also referred to as a transmittance evaluation test disk) for examining the relationship between the physical format of the L0 layer and the transmittance was prepared. Further, a test disk (hereinafter also referred to as a reference test disk) in which a dummy substrate was bonded to the L1 layer instead of the L0 layer was produced as a reference disk for transmittance evaluation. The film configuration of the transmittance evaluation test disk was the film configuration shown in FIG.

  Hereinafter, a method for producing a test disk for transmittance evaluation will be described with reference to FIG. The method for producing the single-sided, double-layered rewritable optical disc of Reference Example 3 is the same as the method for producing the transmittance evaluation test disc described below.

  First, the L0 layer 70 was produced as follows. As the first substrate 71 of the L0 layer 70, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was used. The physical format of the L0 layer 70 is composed of a ROM area 91, a transition area 92, and an information recording area 93 from the inner periphery side as shown in FIG. Embossed pits were formed in the region on the first substrate 71 of the L0 layer corresponding to the ROM region 91, and grooves were formed in the region on the first substrate 71 corresponding to the information recording region 93. The region on the first substrate 71 corresponding to the transition region 92 is a mirror surface. Specifically, a pit row having a track pitch of 400 nm and a half-value width of 160 nm was formed in a region on the first substrate 71 of the L0 layer corresponding to the ROM region 91. In the region on the first substrate 71 corresponding to the information recording region 93, a groove having a track pitch of 400 nm, a half-value width of 220 nm, and a depth of 20 nm was formed. A region on the first substrate 71 corresponding to the transition region 92 was formed with a mirror surface having a radial width of about 10 μm. Such a concavo-convex pattern on the first substrate 71 was formed using a stamper as in Reference Example 1.

Next, the first protective layer 72, the first interface layer 73, the first recording layer 74, the second interface layer 75, the second protective layer 76, and the first protective layer 72 are formed on the first substrate 71 of the L0 layer 70 by a sputtering process. A reflective layer 77 and a third protective layer 78 were sequentially stacked. At this time, the first protective layer 72 is formed of (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 50 nm, the first interface layer 73 is formed of Ge ₈ Cr ₂ -N having a thickness of 1 nm, and the first recording layer is formed. 74 is formed of Bi _4.5 Ge ₄₈ Te _47.5 with a thickness of 7 nm, the second interface layer 75 is formed of Ge ₈ Cr ₂ —N with a thickness of 2 nm, and the second protective layer 76 is formed with a thickness of 7 nm. (ZnS) ₈₀ (SiO ₂ ) ₂₀ , the first reflective layer 77 is formed of Ag with a thickness of 8 nm, and the third protective layer 78 is (ZnS) ₈₀ (SiO ₂ ) ₂₀ with a thickness of 25 nm. Formed.

  Then, initialization was performed by irradiating the single disk disk of the L0 layer 70 manufactured as described above with an elliptical beam having a wavelength of 810 nm, a beam major axis of 96 μm, and a minor axis of 1 μm. In this way, the L0 layer 70 was produced.

  Next, the L1 layer 80 was produced as follows. First, as the second substrate 81 of the L1 layer 80, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was used. Grooves having a track pitch of 400 nm, a half width of 180 nm, and a depth of 20 nm were formed on the surface of the second substrate 81 from the innermost periphery to the outermost periphery of the disk. As shown in FIG. 8, the laser beam 40 is applied to the L1 layer 80 from the groove pattern forming surface side of the second substrate 81. Therefore, the groove pattern takes the L0 layer into consideration. The spiral was formed in the direction opposite to that of 70.

Next, the second reflective layer 87, the second protective layer 86, the second interface layer 85, the second recording layer 84, and the first interface are formed on the groove pattern forming surface of the second substrate 81 of the L1 layer 80 by a sputtering process. A layer 83 and a first protective layer 82 were sequentially stacked. That is, in the L1 layer 80, the constituent films of the L1 layer 80 were formed in the order reverse to the stacking order of the constituent films of the L0 layer 70. At this time, the second reflective layer 87 is formed of Ag having a thickness of 150 nm, the second protective layer 86 is formed of (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 11 nm, and the second interface layer 85 has a thickness of 2 nm. of _Ge 8 _Cr 2 formed with -N, the second recording layer 84 is formed by _Bi 4.5 _Ge 48 _{Te 47.5} with a thickness of 11 nm, the first interface layer 83 having a thickness of 7 nm _Ge 8 Cr ₂ - The first protective layer 82 is formed of (ZnS) ₈₀ (SiO ₂ ) ₂₀ having a thickness of 60 nm. Thus, the L1 layer 80 was produced.

  Next, a UV resin material was applied on the first protective layer 82 of the L1 layer 80 by a spin coating method. In this state, UV irradiation was performed to cure the UV resin material to form a UV resin layer 90a that is a part of the spacer layer 90. The film thickness of the UV resin layer 90a was 10 μm. Next, similarly to the L0 layer 70, a laser beam having an elliptical beam having a wavelength of 810 nm, a beam major axis of 96 μm, and a minor axis of 1 μm is irradiated on the single disk of the L1 layer 80 on which the UV resin layer 90a is formed. Made. At this time, in the apparatus used for initialization, spherical aberration correction was performed by inserting optical glass having a thickness of 0.6 mm between the optical head for irradiating laser light and the single disk.

  Next, the L0 layer 70 and the L1 layer 80 produced by the above method were bonded together as follows. First, a UV resin material was applied on the third protective layer 78 of the L0 layer 70 by a spin coating method to form a UV resin layer 90b. Further, the L1 layer 80 was placed thereon. At this time, as shown in FIG. 8, the L1 layer 80 was placed so that the third protective layer 78 of the L0 layer 70 and the first protective layer 82 of the L1 layer 80 face each other with the spacer layer 90 interposed therebetween. In this state, UV irradiation was performed from the L0 layer 70 side to cure the UV resin material of the UV resin layer 90b to form the spacer layer 90, and the L0 layer 70 and the L1 layer 80 were bonded together. The thickness of the spacer layer 90 is preferably 15 to 25 μm, and in this example, it is set to 25 μm. The spacer layer 90 was formed of a resin having a refractive index of 1.50 at a wavelength of 405 nm. As described above, the test disk for transmittance evaluation of this example was produced. The reference test disk was produced by the same method as above except that a dummy substrate was bonded to the L1 layer instead of the L0 layer.

  The transmittance of the L0 layer in the transmittance evaluation test disk and the reference test disk prepared by the above-described manufacturing method was measured. The transmittance of the L0 layer in the groove (information recording area) was measured in the erased state and the recorded state. The recording conditions in this measurement were a linear velocity of 6.61 m / s, a recording power of 8.5 mW, and an erasing power of 4.0 mW. The evaluation results are shown in Table 9. The wavelength of the laser beam used for this measurement was 405 nm, and the numerical aperture of the condenser objective lens was NA = 0.65. The transmittance measurement was performed using parallel light having a wavelength of 405 nm. The transmittance in the column “None” in Table 9 is the transmittance of the reference test disk.

  Furthermore, the optimum values of the recording power and the erasing power in the L1 layer when the L1 layer was irradiated with laser light through each region of the L0 layer were examined. At that time, the recording pulse strategy was the same, and the recording power and erasing power without asymmetry were set to their optimum values. The results are shown in Table 10. The optimum recording power and optimum erasing power in the column “None” in Table 10 are the optimum recording power and optimum erasing power of the reference test disk.

  As is apparent from the results of Tables 9 and 10, when the recording layer was formed of a phase change material, the transmittance of the L0 layer did not change depending on the recording state of the first recording layer of the L0 layer. It was found that depending on the shape of the first substrate, the transmittance of the L0 layer differs, and the optimum recording and reproducing power also changes. Therefore, also in this example, when irradiating a light beam to the test area and the information recording / reproducing area of the L1 layer and performing information recording / reproducing, the transmittance of the L0 layer area through which the light beam passes is constant. It has become clear that it is important to keep it on.

[Configuration of Optical Disc of Reference Example 3]
In Reference Example 3, the L0 layer and the L1 layer are both formed in a physical format as shown in FIG. 2, and the positional relationship of the physical format between the L0 layer and the L1 layer has a relationship as shown in Table 11 A rewritable optical disk was produced. Table 11 shows the start radius position and the end radius position of each area constituting the physical format of the L0 layer and the L1 layer. In addition, the radial position described in Table 11 is a value at the design stage, the numerical value described in the L0 layer column is the distance from the L0 layer center, and the numerical value described in the L1 layer column is from the L1 layer center. Distance.

  In the optical disk of this example, in order to make the number of tracks in the L1 layer and the number of tracks in the L0 layer the same, that is, in order to make the recording capacities of the L0 layer and the L1 layer the same, as shown in Table 11, the L1 layer The information recording / reproducing area is shifted from the information recording / reproducing area of the L0 layer to the outer peripheral side. The dimensions of the grooves formed in the region on the first substrate corresponding to the information recording region of the L0 layer in the optical disc of this example are the same as those of the transmittance evaluation disc (track pitch 400 nm, half-value width 220 nm, and depth 20 nm). And the dimensions of the grooves formed in the region on the second substrate corresponding to the information recording region of the L1 layer were a track pitch of 400 nm, a half-value width of 180 nm, and a depth of 20 nm.

  In the optical disc of this example, the physical format configurations of the L0 layer and the L1 layer are made the same, the radial position of each area in the physical format of the L0 layer and the L1 layer is adjusted as shown in Table 11, and Except for changing the track pitch of the L1 layer and the L0 layer, the structure was the same as the above-described transmittance evaluation test disk. The optical disk of this example was manufactured by the same method as the above-described transmittance evaluation test disk.

  As is clear from the measurement results of the transmittance described above (results shown in Table 9), when a phase change material is used for the recording layer, the transmittance is high in the ROM region, transition region, and mirror region of the L0 layer. fluctuate. Therefore, in the optical disc of this example, the light beam condensed over the entire test area and information recording / reproduction area of the L1 layer passes through the ROM area, transition area, and mirror area of the L0 layer whose transmittance varies. The positional relationship of the respective areas in the physical format of the L0 layer and the L1 layer so as to pass only through the area (information recording area 50 in FIG. 2) in which the groove of the L0 layer with little transmittance fluctuation is formed. Adjusted.

In the optical disk of this example, as is clear from Table 7, at the design stage, the distance from the center of the L1 layer at the radial position R (1, TI, i) of the innermost track of the innermost test area of the L1 layer R1 ′ = 23.870 mm, distance R2 ′ = 58.080 mm from the center of the L1 layer at the radial position R (1, TO, o) of the outermost track in the outer peripheral side of the L1 layer, the information recording area of the L0 layer Distance R3 ′ = 23.800 mm from the center of the L0 layer at the radial position R (0, G, i) of the innermost circumferential guide groove of the innermost groove, and the radial position R (0 of the outermost circumferential guide groove of the information recording area of the L0 layer) , G, o), the distance from the center of the L0 layer is R4 ′ = 58.499 mm. In addition, a laser beam having a wavelength of 405 nm was used for recording / reproduction of the optical disk of this example, and a lens having a numerical aperture NA = 0.65 was used as the aperture lens. Further, since the spacer layer of the optical disk is formed of a material having a refractive index ns = 1.5 at a wavelength of 405 nm and the thickness D is 25 μm, the laser light is condensed on the L1 layer in the optical disk of this example. The radius r of the laser beam in the L0 layer when it is on is 11.5 μm. Further, in this example, the specification value RR _pp of the eccentricity when the L0 layer and the L1 layer are bonded is set to 50 μm.

Therefore, in the optical disk of this example, at the design stage, the radial position R (1, TI, i) of the innermost track in the test area on the inner circumference side of the L1 layer and the outermost test area on the outer circumference side of the L1 layer. Distances R1 ′ and R2 ′ from the center of the L1 layer at the radius position R (1, TO, o) of the outer track and the radius position R (0, G, i) of the innermost guide groove in the information recording area of the L0 layer And distances R3 ′ and R4 ′ from the center of the L0 layer at the radial position R (0, G, o) of the outermost guide groove in the information recording area of the L0 layer, the radius r of the laser beam in the L0 layer, and the amount of eccentricity The relationship of the above formulas (1) ′ and (2) ′ is established between the specification value RR _pp . Therefore, in the optical disc of this example manufactured with the above design content, the physical format positional relationship between the L0 layer and the L1 layer satisfies the above expressions (1) and (2). Therefore, in the optical disk manufactured in this example, the L0 layer ROM area, transition area, and mirror area where the light beam condensed over the entire test area and information recording / reproduction area of the L1 layer varies in transmittance. And only passes through the information recording area of the L0 layer where the transmittance fluctuation is very small.

[Reference Example 4]
In Reference Example 4, the L0 layer and the L1 layer are both formed at the same track pitch, and as shown in Table 8, the single-sided surface 2 in which the radial positions of the regions in the physical format of the L0 layer and the L1 layer are the same A layer-type rewritable optical disc was produced. That is, an optical disc was produced in which the physical format positional relationship between the L0 layer and the L1 layer did not satisfy the above expressions (1) and (2). The configuration is the same as that of the optical disc of Reference Example 3 except that the track pitches of the L0 layer and the L1 layer are the same, and the radial positions of the respective areas in the physical formats of the L0 layer and the L1 layer are the same. The same method was used.

[Recording characteristics]
Five rewritable optical discs of Reference Example 3 and 4 of the single-sided two-layer type were made on a trial basis, recorded on the L0 layer, and then recorded on the L1 layer. As a result, with the optical disc of Reference Example 3, all five discs could be recorded normally on the L1 layer by a single recording operation. However, in the optical disc of Reference Example 4, there is no disc that can be normally recorded in the L1 layer in one recording operation, and two discs that can be normally recorded in the L1 layer after repeating the recording operation a plurality of times, the remaining discs Three sheets could not be recorded. From this result, as in the optical disc of Reference Example 3, the positional relationship between the physical format of the L0 layer 10 and the physical format of the L1 layer 20 is adjusted so that the relationship of the above expressions (1) and (2) is established. Thus, it was found that information recording / reproduction with respect to the L1 layer can be performed stably and with high reliability.

  Further, when the test area on the inner circumference side of the L1 layer of all the optical discs in Reference Example 4 was examined, it was found that there was one cycle of amplitude fluctuation per track circumference. This is because the laser light reaching the test area on the inner peripheral side of the L1 layer has passed through the mirror area and the ROM area of the L0 layer due to the influence of eccentricity when the L0 layer and the L1 layer are bonded together.

  In the first embodiment, the optical recording medium including two information units has been described. However, the present invention is not limited to this. The present invention can also be applied to an optical recording medium provided with three or more information units. When the optical recording medium includes three or more information units, one of the adjacent information units on the side on which the light beam is incident is the first information unit, and the other information unit is the second information unit. Then, when the test area is provided near the inner periphery of the second information recording area, the above equation (3) is satisfied, and when the test area is provided near the outer periphery of the second information recording area. When the above equation (4) is established and the test areas are provided near both the inner circumference and the outer circumference of the second information recording area, each of the formulas (3) and (4) is established. What is necessary is just to adjust the positional relationship of the physical format of an information part.

  In the optical recording medium of the present invention, as described above, information recording / reproduction can be performed stably and reliably also on the information portion (second information portion) on the side far from the light incident side. Therefore, the optical recording medium of the present invention is suitable for an optical recording medium having two or more recording layers for recording and reproducing information by entering a light beam from one side, and particularly as a single-sided dual-layer type optical disc. Is preferred.

FIG. 1 is a schematic cross-sectional view of a single-sided, dual-layer type optical disc according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the physical format of the L0 layer of the optical disc in the embodiment of the present invention. FIG. 3 is a perspective view showing the structure of the concavo-convex pattern formed on the substrate surface of the L0 layer of the optical disc in the embodiment of the present invention. FIGS. 4A and 4B are diagrams showing the physical format positional relationship between the L0 layer and the L1 layer in the reference mode. FIGS. 5A and 5B are diagrams showing the positional relationship between the physical formats of the L0 layer and the L1 layer in the embodiment of the present invention. FIG. 6 is a diagram for explaining how to obtain the radius of the light beam in the L0 layer when the light beam is focused on the L1 layer. FIG. 7 is a schematic configuration diagram of the physical format of the L0 layer of the optical disc manufactured in Reference Example 1. FIG. 8 is a schematic cross-sectional view of the rewritable optical disk manufactured in Reference Example 3.

Explanation of symbols

10,70 L0 layer (first information part)
11, 71 First substrate 12, 74 First recording layer 13, 77 First reflection layer 20, 80 L1 layer (second information section)
21, 81 Second substrate 22, 84 Second recording layer 23, 87 Second reflective layer 30, 90 Spacer layer 50 Information recording area 51 ROM area 52 Transition area 54, 56 Test area 100, 300 Optical disc

Claims (2)

An optical recording medium on which information is recorded and reproduced by irradiation with a light beam,
A first information section;
A second information part irradiated with the light beam via the first information part,
The first information section is arranged in this order from the inner circumference side to the first preformat area, the first transition area, the first inner circumference test area, the first information recording area, and the first outer circumference test area. And the first preformat area is provided with embossed pits, the first transition area is a mirror surface, and the first information recording area, the first inner circumference side test area and the first outer circumference side test area have the above-mentioned A light beam guide groove is provided,
The second information section is arranged in this order from the inner circumference side to the second preformat area, the second transition area, the second inner circumference side test area, the second information recording area, and the second outer circumference side test area. The second preformat area is provided with embossed pits, the second transition area is a mirror surface, and the second information recording area, the second inner periphery side test area, and the second outer periphery side test area are A light beam guide groove is provided,
The distances from the center of the optical recording medium at the radial position of the innermost track of the second inner peripheral side test area and the radial position of the outermost track of the second outer peripheral side test area are R1 and R2, respectively. When the radius of the light beam in the first information part when the light beam is focused on is r,
The first preformat area, the first transition area, the first inner circumference side test area, and the first outer circumference side test area are different from the areas of distances R1-r to R2 + r from the center of the optical recording medium of the first information section. An optical recording medium arranged in a region. An optical recording medium on which information is recorded and reproduced by irradiation with a light beam,
A first information section having a first substrate and a first recording layer, the light beam being incident from the first substrate side;
A second information section having a second substrate and a second recording layer, and being irradiated with the light beam through the first information section;
The first information section is arranged in this order from the inner circumference side to the first preformat area, the first transition area, the first inner circumference test area, the first information recording area, and the first outer circumference test area. The area on the first substrate corresponding to the first preformat area is provided with emboss pits, the area on the first substrate corresponding to the first transition area is a mirror surface, and the first information recording area The light beam guide groove is provided in a region on the first substrate corresponding to the first inner peripheral side test region and the first outer peripheral side test region,
The second information section is arranged in this order from the inner circumference side to the second preformat area, the second transition area, the second inner circumference side test area, the second information recording area, and the second outer circumference side test area. The area on the second substrate corresponding to the second preformat area is provided with emboss pits, the area on the second substrate corresponding to the second transition area is a mirror surface, and the second information recording area The light beam guide groove is provided in a region on the second substrate corresponding to the second inner peripheral side test region and the second outer peripheral side test region,
The distances from the center of the optical recording medium at the radial position of the innermost track of the second inner peripheral side test area and the radial position of the outermost track of the second outer peripheral side test area are R1 and R2, respectively. When the radius of the light beam in the first information part when the light beam is focused on is r,
The first preformat area, the first transition area, the first inner circumference side test area, and the first outer circumference side test area are different from the areas of distances R1-r to R2 + r from the center of the optical recording medium of the first information section. An optical recording medium arranged in a region.

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