JP2008217991A - Information storage medium and disk apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information storage medium that has favorable recording and playback characteristics and that can perform recording and playback from one side. <P>SOLUTION: The information storage medium includes a substrate, a first optical reflective layer containing an organic dye material, a first recording layer, a first barrier layer, a space layer, a second optical reflective layer, a second recording layer, a second barrier layer and a protective layer formed on the second barrier layer. The first and second recording layers are capable of playback at a wavelength of 405 nm, the maximum absorption wavelength λmax being higher than 405 nm, and capable of recording. A groove has an inner zone and a data zone, and the inner zone has a BCA area, a prerecording area and a rewrite area, and is capable of playback by irradiating the first and second recording layers with a playback light through the protective layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information storage medium capable of recording and reproducing information by a short wavelength laser beam such as a blue laser beam and a disk device for performing the reproduction.

  As is well known, in recent years, with the spread of personal computers and the like, the importance of media for storing digital data has increased. For example, information storage media capable of digitally recording and reproducing long-time video information, audio information, and the like are now widespread. Also, information storage media for digital recording and reproduction have been used in mobile devices such as mobile phones.

  Here, this type of information storage medium has a large information recording capacity, a high random access performance capable of quickly searching for desired recording information, and is small and light, excellent in storability and portability, In addition, disk-shaped ones are often used because they are economically inexpensive.

  As such a disk-shaped information storage medium, at present, a so-called optical disk that can record and reproduce information in a non-contact manner by irradiating a laser beam is mainly used. This optical disc mainly conforms to the CD (Compact Disk) standard or the DVD (Digital Versatile Disk) standard, and is compatible with both standards.

  The optical disc includes a read-only type such as a CD-DA (Digital Audio), a CD-ROM (Read Only Memory), a DVD-V (Video), and a DVD-ROM, and a CD-R (Recordable). ), Write-once type that can write information only once, such as DVD-R, and rewritable type that can rewrite information as many times as CD-RW (Rewritable), DVD-RW, etc. There are three types.

  Of these, recordable optical discs using organic dyes in the recording layer are most widely used because they can be recorded because of low manufacturing costs.

  In recent years, a double-layer DVD-R has been proposed in response to a demand for a large capacity of a write-once recording disk. This is a disc having two recording layers of DVD-R, and has two organic dye recording layers.

  However, it has been difficult to obtain sufficient recording / reproduction characteristics.

  In addition, such a two-layer write-once recording disk has a structure in which, for example, a light reflection layer, a recording layer, a barrier layer, a light semi-transmissive layer, a recording layer, a barrier layer, and a protective layer are sequentially laminated on a transparent resin substrate The manufacturing process becomes very complicated, the cost tends to increase, and the yield tends to decrease.

As a manufacturing process technique for improving the yield, for example, there is a method in which a protective layer is spinner coated in two steps (see, for example, Patent Document 1 and Patent Document 2). By using this method, the protective layer can be dried in a short time, but there is a tendency that the thickness of the protective layer is uneven and the recording characteristics and reproduction characteristics are deteriorated.
JP 2005-259111 A JP 2005-4944 A

  The present invention has been made in view of the above circumstances, and an object thereof is to obtain an information storage medium having good recording / reproducing characteristics and capable of recording / reproducing from one side.

  The information storage medium of the present invention is recordable / reproducible from one side, has a concentric or spiral land and groove formed therein, and has an opening at the center thereof, and is provided along the land and groove of the substrate. A first recording layer that is reproducible at a wavelength of 405 nm, has a maximum absorption wavelength λmax higher than 405 nm, and is recordable on the first recording layer A first barrier layer provided, and a space layer provided on the first barrier layer, wherein a land and a groove synchronized with the shape are formed on a surface opposite to the surface facing the first barrier layer And a second light reflecting layer provided along the lands and grooves of the space layer and formed with the lands and grooves synchronized with the shape, and the lands and grooves synchronized with the shape. A second recording layer that is reproducible at a wavelength of 405 nm, has a maximum absorption wavelength λmax higher than 405 nm, and is recordable, and a second barrier layer formed on the second recording layer, A protective layer formed on the second barrier layer, the groove having an inner zone and a data zone, the inner zone having a BCA area, a pre-recording area, and a rewriting area, Reproduction can be performed by irradiating the first and second recording layers with reproduction light through the protective layer.

  According to the present invention, an information storage medium having good recording / reproducing characteristics and capable of recording / reproducing from one side can be obtained.

  In the following, various embodiments of the present invention will be described.

  The information storage medium is divided into first to fifth embodiments having the following characteristics.

  The information storage medium according to the first to third embodiments of the present invention is basically an information storage medium that can be recorded and reproduced from one side, on a substrate on which concentric or spiral lands and grooves are formed. In addition, a first recording layer containing an organic dye material, a first barrier layer, a space layer, a second recording layer containing an organic dye material, a second barrier layer, and a protective layer are sequentially laminated. including. On at least one main surface of the first recording layer, the first barrier layer, the space layer, the second recording layer, and the second barrier layer, lands and grooves synchronized with the concentric or spiral shape are formed. Is formed.

  In the first embodiment of the present invention, the information storage medium has an opening at its center, and the angle formed between the outer and inner surfaces of the protective layer and the direction parallel to the surface of the second barrier layer is 30 to 30. It can be 150 °.

  In the second embodiment of the present invention, at least one of the first barrier layer and the second barrier layer has lands and grooves synchronized with the concentric or spiral shapes on both main surfaces thereof, In addition, the depth of the land on the other main surface can be made smaller than the depth of the land on the main surface on the substrate side.

  In the third embodiment of the present invention, the first barrier layer and the second barrier layer can be formed of a coatable material.

  The information storage media according to the fourth and fifth embodiments of the present invention are basically information storage media that can be recorded / reproduced from one side, in which concentric or spiral lands and grooves are formed. On the substrate, a light reflecting layer, a first recording layer containing an organic dye material, a first barrier layer, a space layer, a light semi-transmissive layer, a second recording layer containing an organic dye material, and a second It includes a configuration in which a barrier layer and a protective layer are sequentially laminated. At least one main surface of the light reflecting layer, the first recording layer, the first barrier layer, the space layer, the light semi-transmissive layer, the second recording layer, and the second barrier layer has the concentric or spiral shape. Lands and grooves synchronized with the shape are formed.

  In the fourth embodiment of the present invention, the wobble amplitude of the groove facing the light semi-transmissive layer of the first recording layer is greater than the wobble amplitude of the groove facing the second light reflecting layer of the second recording layer. Can also be increased.

  In the fifth embodiment of the present invention, the land depth of the first recording layer may be different from the land depth of the second recording layer.

  According to the first embodiment, the angle formed between the inner surface or the outer surface of the transparent protective layer and the recording layer is set in the range of 30 degrees to 150 degrees, so that the inner periphery portion to the outer periphery portion of the information storage medium is set. It is possible to set the thickness of the transparent protective layer uniformly over a wide area. As a result, it is possible to prevent deterioration of the characteristics of the recording layer caused by moisture entering the recording layer through the transparent protective layer. In addition, since the thickness of the transparent protective layer is uniform over a wide range from the inner periphery to the outer periphery, it is possible to improve the reproduction characteristics or recording characteristics from the recording layer in the information recording / reproducing apparatus. It becomes.

  According to the second embodiment, at least one of the first barrier layer and the second barrier layer has lands and grooves synchronized with the concentric or spiral shape on both main surfaces thereof, and is on the substrate side. Since the depth of the land on the other main surface is smaller than the depth of the land on the other main surface, the wettability of the first and second recording layers is taken into consideration, and the land can be obtained from the first recording layer. The amount of wobble signal and the amount of wobble signal obtained from the second recording layer can be made substantially equal, and stable wobble signals can be obtained for both the first recording layer and the second recording layer.

  According to the third embodiment, by providing a barrier layer between the recording layer and the space layer, the space layer can be stably formed without impairing the characteristics and shape of the recording layer. Similarly, by forming a barrier layer between the recording layer and the protective layer, a transparent protective layer can be stably formed without impairing the characteristics and shape of the recording layer. Further, the barrier layer can be formed by various coating methods by selecting a material that can be coated. The coating method is easier to manufacture and shorter in manufacturing time than the conventional sputtering method or vacuum deposition method. Moreover, since it can be manufactured under normal pressure, the apparatus is simple and inexpensive. As a result, the information storage medium according to the second embodiment of the present invention can reduce the cost.

  According to the fourth embodiment, taking into account the difference in wettability during the formation of the first recording layer and the second recording layer, the wobble amplitude due to the land and groove of the space layer is set to the wobble with respect to the land and groove of the substrate. By making it smaller than the amplitude, the amount of wobble signal obtained from the first recording layer and the amount of wobble signal obtained from the second recording layer are made substantially equal to improve the stability of wobble signal detection in the information recording / reproducing apparatus. I can do it.

  According to the fifth embodiment, the land depth of the first recording layer is different from the land depth of the second recording layer. By making the land depth of the first recording layer different from the land depth of the second recording layer, the difference in wettability between the first recording layer and the second recording layer is taken into consideration. It is possible to adjust the amount of wobble signals obtained from the second recording layer and the amount of wobble signals obtained from the second recording layer substantially equally, and it is possible to obtain stable wobble signals in both the first recording layer and the second recording layer. Become.

  In addition, as a material for the first and second barrier layers, for example, a water-based paint can be used. The water-based paint is inexpensive and easy to handle, and can reduce the manufacturing cost and the manufacturing time of the information storage medium according to the present invention.

  Hereinafter, the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a sectional view schematically showing an embodiment of the information storage medium of the present invention.

  As shown in the figure, the information storage medium 15 has a substrate 8 having concentric or spiral lands and grooves on one main surface thereof. On the substrate 8, a light reflection layer 4-4 and a recording layer 3-4 each having lands and grooves on both main surfaces thereof are sequentially laminated. On the recording layer 3-4, a barrier layer 6-4 is provided so as to at least partially fill the dent of the land. A space layer 7 is provided on the barrier layer 6-4, and concentric or spiral lands and grooves are formed on its surface by a stamper (not shown). On the space layer 7, a light semi-transmissive layer 4-3 and a recording layer 3-3 having lands and grooves on both main surfaces are provided in this order. A second barrier layer 6-3 is provided on the recording layer 3-3 so that the land recess is at least partially filled. On the barrier layer 6-3, as the transparent protective layer 5, a transparent protective layer 5-2 and a transparent protective layer 5-1 are sequentially laminated.

  Here, the combination of the light transflective layer 4-3 and the recording layer 3-3 is a layer L0 as a recording unit, and the combination of the light reflecting layer 4-4 and the recording layer 3-4 is a layer L1 as a recording unit. .

  For example, it is possible to read information recorded on the basis of reflected light that is incident from the direction of the arrow 101 and reflected from the layer L0 in the direction of the arrow 102, for example.

  In this information storage medium, since the protective layer 5-1 serves as a reading surface, the convex portion 11 near the reading surface of the projections 11 and 16 is a groove, and the concave portion 16 farther from the reading surface than the groove 11 is a land.

  The thickness of the substrate is sufficiently thick, for example, less than 1.1 mm.

  Further, the thickness t of the protective layer is, for example, about 0.1 mm.

  In the first embodiment, in the information storage medium shown in FIG. 1, the angle formed between the outer side surface and the inner side surface of the protective layer and the direction parallel to the barrier layer surface is 30 to 150 °.

  By making the side surface angle of the protective layer close to 30 to 150 °, or even 90 °, it is possible to ensure the uniform thickness of the transparent protective layer on the inner and outer peripheral sides of the information storage medium and pass through the protective layer 5. Thus, it is possible to prevent the recording layer from deteriorating due to water entering the recording layer. Furthermore, the reading accuracy and recording accuracy of the information recording / reproducing apparatus can be ensured.

  FIG. 2 is a cross-sectional view schematically showing another example of the information storage medium of the present invention.

  As shown in FIG. 2, in the information storage medium according to the second embodiment of the present invention, at least one of the barrier layers 6-3 and 6-4 has both main surfaces 13-3 and 13-3 ′. , 13-4 and 13-4 ′ have lands and grooves synchronized with concentric or spiral shapes, and the other side than the land depth of the main surfaces 13-3 ′ and 13-4 ′ on the substrate side. The main surfaces 13-3 and 13-4 have the same configuration as that of FIG. 1 except that the land depth can be reduced.

  By changing the level difference at the interface of the barrier layer, the ease of forming the space layer and the protective layer formed on the barrier layer can be improved, the reliability during mass production can be improved, and the manufacture of the information storage medium can be simplified. Can reduce the price of information storage media.

  In the third embodiment of the present invention, in the information storage medium shown in FIG. 1, a material that can be formed by a coating method can be used as the material of the barrier layers 6-3 and 6-4.

  Further, when the barrier layers 6-3 and 6-4 are formed by the coating process, the solution containing the material of the barrier layers 6-3 and 6-4 is prevented so that the recording layers 3-3 and 3-4 are not dissolved or deformed / deformed. The solvent is selected from, for example, water, polyvinyl alcohol (PVA), polyurethane vinyl alcohol, perfluoroether, von Prioni oil, etc., and the water-soluble material that is soluble in these solvents as the material of the barrier layers 6-3 and 6-4 And water-based paints, gelatin materials, utril rubber materials, silicone materials, urethane rubber materials, and the like. By making it possible to form the barrier layers 6-3 and 6-4 by coating, the manufacturing becomes easy and the manufacturing time is shortened. The manufacturing cost of the information storage medium can be greatly reduced.

  In the fourth and fifth embodiments of the present invention, in the information storage medium shown in FIG. 1, the land M1 between the light semi-transmissive layer 4-3 and the recording layer 3-3, the light reflecting layer 4-4 and the recording are recorded. For the land M2 between the layers 3-4, the wobble amplitude can be made smaller in M2 than in M1, or the dimension in the depth direction can be changed between the layers L1 and L0.

  In the formation stage of the recording layer 3-4 and the recording layer 3-3, the wettability between the coating liquid containing the organic dye material for the recording layer 3-4 and the light reflecting layer, and the organic for the recording layer 3-3 The shape of the land M2 of the recording layer 3-4 and the land M1 of the recording layer 3-3 is set by setting the wettability between the coating liquid containing the dye material and the light semi-transmissive layer 4-3 different from each other. The dimensions, for example, the dimensions in the depth direction can be made different from each other. Thereby, the reproduction signal characteristics from the layer 0 and the layer 1 can be matched, and the recording / reproduction characteristics of the information recording / reproducing apparatus can be improved.

  In another embodiment of the present invention, the flatness of the surface of the protective layer can be ensured over the entire surface of the information storage medium.

  By flattening the surface of the transparent protective layer over the entire surface of the information storage medium, it is possible to prevent the recording layer from being deteriorated due to water intrusion. Further, by making the thickness t of the transparent protective layer uniform, sufficient reading accuracy or writing accuracy of the information recording / reproducing apparatus over the entire surface of the information storage medium can be ensured.

  In yet another embodiment of the present invention, the protective layer can be a multilayered structure.

  By forming the protective layer in a laminated structure, it is possible to improve the manufacturability of the information storage medium and to ensure the low cost and high reliability of the information storage medium, compared to the case where a single layer thick protective layer is formed. it can.

  Further, in the information storage medium shown in FIGS. 1 and 2, lands 16 and grooves are formed in advance on this information storage medium, and address information is recorded in advance by wobbling the groove 11. Examples of information contents recorded in the pre-groove 11 and data format recorded in the recording layer 3-3 or the recording layer 3-4 in the information storage medium according to the present embodiment are shown below.

§ Description of B format B format optical disc specification FIG. 3 shows the specification of a B format optical disc using a blue-violet laser light source. B format optical discs are classified into rewritable type (RE disc), read-only type (ROM disc), and write once type (R disc). As shown in FIG. 3, any type other than the standard data transfer rate is used. It is a common specification and it is easy to realize compatible drives common to different types. In contrast to the current DVD with two 0.6 nm thick disk substrates, the B format provides a recording layer on a 1.1 nm thick disk substrate and a 0.1 nm transparent It is a structure covered with a simple cover layer. Single-sided, double-layer media are also defined.

[Error correction method]
In the B format, an error correction method called a picket code that can efficiently detect a burst error is adopted. Pickets are inserted into main data (user data) columns at regular intervals. The main data is protected by a powerful and efficient Reed-Solomon code. The picket is protected by a second very powerful and efficient Reed-Solomon code separate from the main data. In decoding, the picket is first error-corrected. The correction information can be used to estimate the position of the burst error in the main data. The symbols at these positions are flagged as “Erasure” which is used when correcting the code word of the main data.

  FIG. 4 shows the structure of a picket code (error correction block). The error correction block (ECC block) in the B format is composed of 64 Kbytes of user data as in the H format. This data is protected by a very strong Reed-Solomon code LDC (long distance code).

  The LCD consists of 304 code words. Each codeword consists of 216 information symbols and 32 parity symbols. That is, the code word length is 248 (= 216 + 32) symbols. These codewords are interleaved every 2 × 2 in the vertical direction of the ECC block, and constitute an ECC block of 152 (= 304/2) bytes × 496 (= 2 × 216 + 2 × 32) bytes. .

  The interleave length of picket is 155 × 8 bytes (there are 8 control code correction sequences in 496 bytes), and the interleave length of user data is 155 × 2 bytes. For the 496 bytes in the vertical direction, every 31 rows is a recording unit. In the parity symbol of the main data, two groups of parity symbols are nested for each row.

  In the B format, a picket code embedded in the ECC block in a shape like a “pillar” at regular intervals is adopted. A burst error is detected by looking at the error status. Specifically, four picket rows were arranged at equal intervals in one ECC block. There is also an address in the picket. The picket contains its own parity.

  Since the symbols in the picket string also need to be corrected, the pickets in the three right columns are error-corrected and protected by BIS (burst indicator subcode). This BIS is composed of 30 information symbols and 32 parity symbols, and the codeword length is 62 symbols. From the ratio between the information symbol and the parity symbol, it can be seen that there is an extremely strong correction capability.

  BIS codewords are interleaved and stored in three picket sequences each consisting of 496 bytes. Here, both LDC and BIS codes have the same number of parity symbols per codeword of 32. This means that one common Reed-Solomon decoder can decode both LDC and BIS.

  When decoding data, first, picket string correction processing is performed by BIS. Thereby, the location of the burst error is estimated, and a flag called Erasure is set at that location. This is used when correcting the code word of the main data.

  The information symbols protected by the BIS code form an additional data channel (side channel) separate from the main data. Address information is stored in this side channel. Address information error correction uses a dedicated Reed-Solomon code prepared separately from the main data. This code consists of 5 information symbols and 4 parity symbols. As a result, it is possible to grasp a high-speed and highly reliable address independent of the main data error correction system.

[Address format]
Like the CD-R disc, the RE disc has a very narrow groove as a recording track. The recording mark is written only in the convex portion when seen from the laser beam incident direction among the concave and convex portions (on-groove recording).

  The address information indicating the absolute position on the disk is embedded by slightly wobbling (meandering, swinging) the groove as in a CD-R disk or the like. The signal is modulated, and digital data representing "1" or "0" is placed on the meandering shape or period. FIG. 5 shows the wobble method. The meandering amplitude is only ± 10 nm in the disk radial direction. 56 wobbles (about 0.3 mm in length on the disk) are address information 1 bit = ADIP unit (described later).

  In order to write fine recording marks with almost no positional deviation, it is necessary to generate a stable and accurate recording clock signal. Therefore, we focused on a system in which the main frequency component of wobble is single and the groove is smoothly continuous. If the frequency is single, a stable recording clock signal can be easily generated from the wobble component extracted by the filter.

  Timing information and address information are added to the wobble based on this single frequency. For this purpose, “modulation” is applied. As this modulation method, one that is less prone to error even if there are various distortions inherent to the optical disc is selected.

  The wobble signal distortion generated in the optical disk is classified into the following four when sorted by cause.

  (1) Disc noise: Disturbance of the surface shape (surface roughness) generated in the groove portion during manufacturing, noise generated in the recording film, crosstalk noise leaking from recorded data, and the like.

  (2) Wobble shift: A phenomenon in which the detection sensitivity is lowered when the wobble detection position is shifted relative to the normal position in the recording / reproducing apparatus. It is likely to occur immediately after a seek operation.

  (3) Wobble beat: Crosstalk generated between the wobble signal of the track to be recorded and the adjacent track. This occurs when the rotation control method is CLV (constant linear velocity) and there is a deviation in the angular frequency of adjacent wobbles.

  (4) Defects: caused by local defects due to dust or scratches on the disk surface.

  In the RE disc, two different wobble modulation schemes are combined in a form that produces a synergistic effect on condition that they have high tolerance against all of these four different types of signal distortion. This is because resistance to four types of signal distortion, which is generally difficult to achieve with only one type of modulation system, can be obtained without side effects.

  The two systems are the MSK (minimum shift keying) system and the STW (saw tooth wobble) system (FIG. 6). The name of the STW is named because its waveform resembles a “tooth profile”.

  In the RE disk, one bit of “0” or “1” is expressed by a total of 56 wobbles. These 56 are called a unit, that is, an ADIP (address in pregroove) unit. When 83 ADIP units are continuously read, an ADIP word indicating one address is obtained. The ADIP word is composed of 24-bit address information, 12-bit auxiliary data, a reference (calibration) area, error correction data, and the like. In the RE disc, three ADIP words are assigned to each RUB (recording unit block, 64 Kbyte unit) for recording main data.

  The ADIP unit consisting of 56 wobbles is roughly divided into the first half and the second half. The first half of the wobble numbers from 0 to 17 is the MSK system, and the second half of the 18th to 55th is the STW system, which is smoothly connected to the next ADIP unit. One ADIP unit can represent one bit. Depending on whether it is “0” or “1”, the position of the wobble subjected to the MSK modulation is changed in the first half, and the shape of the sawtooth wave is changed in the second half.

  The first half of the MSK system is further divided into three wobble areas subjected to MSK modulation and a monotone wobble cos (wt) area. First, the three wobbles from No. 0 to No. 2 always start with MSK modulation in any ADIP unit. This is called a bit sync (an identifier indicating the start position of the ADIP unit).

  After that, the monotone wobble is next. Then, data is represented by the number of monotone wobbles up to the next three wobbles subjected to MSK modulation that reappears. Specifically, “11” is “0”, and “9” is nine. Data is distinguished by the difference between two wobbles.

  The MSK method uses a local phase change of the fundamental wave. In other words, the region where there is no phase change is dominant. This region is effectively used as a place where the phase of the fundamental wave does not change even in the STW system.

  A region subjected to MSK modulation has a length of three wobbles. The first part is 1.5 times the frequency of monotone wobble (cos (1.5 wt)), the second is the same frequency as monotone wobble, and the third is 1.5 times the frequency again. Double to restore the original phase. In this way, the polarity of the second (center) wobble is just inverted with respect to the monotone wobble, and this is detected. The first start point and the third end point are exactly in phase with the monotone wobble. Therefore, a smooth connection without discontinuities is possible.

  On the other hand, there are two types of waveforms in the latter half of the STW system. One is a waveform that rises steeply toward the outer periphery of the disk and returns with a gentle inclination toward the center of the disk, and the other is a waveform that rises with a gentle inclination and returns sharply. The former represents data “0” and the latter represents data “1”. The reliability of data is increased by indicating the same bit using both the MSK method and the STW method in one ADIP unit.

  When the STW method is expressed mathematically, it can be said that a second harmonic sin (2 wt) having an amplitude of ¼ is added to or subtracted from the fundamental wave cos (wt). However, the zero cross point is the same as the monotone wobble regardless of whether the STW system represents “0” or “1”. That is, in extracting the clock signal from the fundamental wave component common to the MSK monotone wobble part, the phase is not affected at all.

  As described above, the MSK method and the STW method work to compensate each other's weak points.

  FIG. 7 shows the ADIP unit. The basic unit of the address wobble format is an ADIP unit. Each group of 56 NML (Nominal Wobble Length) is called an ADIP unit. One NML is equal to 69 channel bits. Different types of ADIP units are defined by inserting modulation wobbles (MSK marks) at specific locations within the ADIP unit (see FIG. 6). 83 ADIP units constitute one ADIP word. The minimum segment of data recorded on the disc exactly matches three consecutive ADIP words. Each ADIP word contains 36 information bits (24 of which are address information bits).

  8 and 9 show the configuration of one ADIP word.

  One ADIP word includes 15 nibbles, and nine nibbles are information nibbles as shown in FIG. Other nibbles are used for ADIP error correction. The fifteen nibbles constitute a codeword of [15, 9, 7] Reed-Solomon code.

  The code word includes nine information nibbles, six information nibbles record address information, and three information nibbles record auxiliary information (for example, disc information).

  The Reed-Solomon code of [15, 9, 7] is non-systematic, and prior knowledge can increase the Hamming distance by “Informed Decoding”. “Informed Decoding” means that all codewords have a distance of 7 and all codewords of nibble n0 have a distance of 8, so prior knowledge about n0 increases the Hamming distance. Nibble n0 includes a layer index (3 bits) and an MSB of a physical sector number. If nibble n0 is known, the distance increases from 7 to 8.

  FIG. 11 shows the track structure. Here, the track structure of the first layer (the first layer is a layer far from the laser light source) and the second layer of the single-sided dual-layer disc will be described. Grooves are provided to enable push-pull tracking. Several types of track shapes are used. The first layer L0 and the second layer L1 have different tracking directions. In the first layer, the tracking direction is from left to right in the drawing, and in the second layer, the tracking direction is from right to left. The left side of the figure is the inner circumference of the disc, and the right side is the outer circumference. The BCA area consisting of the straight groove of the first layer, the pre-recording area consisting of the HFM (High Frequency Modulated) groove, and the wobble groove area in the rewriting area correspond to the H format lead-in area, and the rewriting of the second layer The wobble groove area in the area, the pre-recording area composed of HFM (High Frequency Modulated) grooves, and the BCA area composed of straight grooves correspond to the H format lead-out area. However, in the H format, the lead-in area and the lead-out area are recorded not in the groove system but in the pre-pit system. The phase of the HFM groove is shifted between the first layer and the second layer so that interlayer crosstalk does not occur.

  FIG. 12 shows a recording frame. As shown in FIG. 4, user data is recorded for each 64 Kbyte segment. Each row of the ECC cluster is converted into a recording frame by adding a frame sync bit and a DC control bit. A 1240-bit (155-byte) stream in each row is converted as follows. A 1240-bit stream has 25-bit data at the head, the following is divided into 45-bit data, a 20-bit frame sync is added before the 25-bit data, and 1-bit is added after the 25-bit data. DC control bits are added, and thereafter, similarly, 1-bit DC control bit is added after 45-bit data. A block including the first 25-bit data is defined as DC control block # 0, and 45-bit data and 1-bit DC control bit are defined as DC control blocks # 1, # 2,. 496 recording frames are referred to as a physical cluster.

  The recording frame is 1-7PP modulated at a rate of 2/3. A modulation rule is applied to 1268 bits excluding the head frame sync to obtain 1902 channel bits, and a 30-bit frame sync is added to the head of the whole. That is, 1932 channel bits (= 28 NML) are configured. The channel bits are NRZI modulated and recorded on the disc.

Frame Sync Structure Each physical cluster includes 16 address units. Each address unit includes 31 recording frames. Each recording frame begins with a frame sync of 30 channel bits. The first 24 bits of the frame sync violate the 1-7PP modulation rules (including a run length twice 9T). The 1-7PP modulation rule uses (1, 7) PLL modulation method and performs parity preserve / prohibit PMTR (repeated minimum transition runlength). Parity Preserve controls the so-called DC (direct current) component of the code (reduces the DC component of the code). The remaining 6 bits of the frame sync change to identify the 7 frame syncs FS0, FS1,. These 6-bit symbols are chosen such that the distance with respect to the deviation amount is 2 or more.

  Seven frame syncs make it possible to obtain more detailed position information than only 16 address units. Of course, it is insufficient to identify 31 recording frames with only 7 different frame syncs. Accordingly, seven frame sync sequences are selected from 31 recording frames so that each frame can be identified by a combination of its own frame sync and any one of the four preceding frames.

  FIG. 13 shows the structure of the recording unit block RUB. The unit of recording is called RUB. As shown in FIG. 5A, the RUB is composed of a 40 wobble data run-in, a 496 × 28 wobble physical cluster, and a 16 wobble data run out. Data run-in and data run-out allow sufficient data buffering to facilitate completely random overwriting. One RUB may be recorded one by one, or a plurality of RUBs may be recorded continuously as shown in FIG.

  Data run-in mainly consists of 3T / 3T / 2T / 2T / 5T / 5T repeating patterns, in which two frame syncs (FS4, FS6) serve as indicators indicating the start position of the next recording unit block. 40 cbs apart from each other.

  Data run out starts with FS0, followed by 9T / 9T / 9T / 9T / 9T / 9T pattern indicating the end of data following FS0, mainly repeating 3T / 3T / 2T / 2T / 5T / 5T Consists of patterns.

  FIG. 14 shows the structure of data run-in and data run-out.

  FIG. 15 is a diagram showing the arrangement of data relating to wobble addresses. The physical cluster is 496 frames. A total of 56 wobbles (NWL) of data run-in and data run-out is 2 × 28 wobbles, which corresponds to two recording frames.

1 RUB = 496 + 2 = 498 recording frames 1 ADIP unit = 56 NWL = 2 recording frames 83 ADIP units = 1 ADIP word (including 1 ADIP address)
3ADIP word = 3 × 83 ADIP unit 3ADIP word = 3 × 83 × 2 = 498 recording frame When recording data on a write once type disc, it is necessary to record the next data in succession to the already recorded data It is. If there is a gap between the data, it cannot be played back. Therefore, in order to record (overwrite) the first data run-in area of the subsequent recording frame so as to overlap the last data run-out area of the preceding recording frame, as shown in FIG. The guard 3 area is arranged at the end of the. FIG. 4A shows a case where only one physical cluster is recorded, and FIG. 4B shows a case where a plurality of physical clusters are continuously recorded. Only after the run-out of the last cluster, the guard 3 is recorded. Provide an area. In this way, each recording unit block recorded independently or a plurality of recording unit blocks recorded continuously is terminated in the guard 3 area. The guard 3 area ensures that there is no unrecorded area between the two recording unit blocks.

  In the description of the §B format as described above, it is desired that the information recording / reproducing apparatus reads the address signal with high accuracy with respect to the wobble signal of the groove 11 shown in FIGS. In the information storage medium of the present embodiment, if the wobble signal qualities in layer 1 7-4 and layer 0 7-3 are different, there arises a problem that the wobble detection characteristic in a specific layer is deteriorated. Therefore, as described above, the shape of the pre-groove 11 is changed between the layer 0 7-3 and the layer 1 7-4, and the detection signal characteristics in the information recording / reproducing apparatus from the wobble are substantially matched, so that it is stable regardless of the layer. A wobble detection signal can be obtained. The layer 0 7-3 means a combination of the recording layer 3-3 and the light semi-transmissive layer 4-3 in FIG. 1, and the layer 1 7-4 is the recording layer 3-4 and the light reflecting layer in FIG. It means a combination of 4-4.

  Further, the information shown in FIGS. 12 to 16 is recorded in the recording layers 3-4 and 3-3, and an error correction method as shown in FIG. 4 is adopted. However, the error correction shown in FIG. 4 may not be sufficient for the information storage medium in the present embodiment. Therefore, in the present embodiment, by ensuring the flatness of the surface of the transparent protective layer 5 over the entire area of the information storage medium, the reproduction signal characteristics are improved particularly in the inner periphery or the outer periphery, as shown in FIGS. The recording signal can be reproduced stably.

  Similarly, by ensuring the flatness of the surface of the transparent protective layer 5 over the entire surface of the information storage medium, the recording characteristics especially on the inner peripheral portion or the outer peripheral portion are improved, and recording based on the formats shown in FIGS. Further stabilization can be achieved.

  Next, the manufacturing method in the information storage medium of this embodiment will be described with reference to FIGS. A substrate 8 having a polycarbonate material, having a thickness of less than 1.1 millimeters and having lands and grooves formed on the surface is prepared. A light reflection layer 4-4 is formed on the substrate 8 by vacuum deposition or sputtering.

  In the present embodiment, for example, silver bismuth AgBi is adopted as the material of the light reflecting layer 4-4. The thickness of the light reflecting layer 4-4 can be, for example, 100 nm or more. Thus, when the thickness of the light reflecting layer 4-4 is sufficiently large, as will be described later, the surface characteristics of the silver bismuth AgBi appear as it is as the base when the recording layer 3-4 is formed. In the present embodiment, the recording layer 3-4 is formed on the light reflecting layer 4-4 by spinner coating.

  In this embodiment, an organometallic complex is used as the material of the recording layer 3-4. Specifically, for example, an azo metal complex can be used among the organometallic complexes. A solution in which an azo metal complex is dissolved in a solvent is applied on the light reflecting layer 4-4, and the substrate 8 is rotated to diffuse the solution, uniformly apply, and then the solvent is evaporated to record. Layers 3-4 are formed. In the step of spreading the solution uniformly on the light reflecting layer 4-4 by spinner coating, the surface of the light reflecting layer 4-4 has the surface characteristics of silver bismuth AgBi alone as described above. It has a low wettability structure. In FIG. 1, the recording layer 3-4 is shown to be formed along the irregularities of the light reflecting layer 4-4, but in fact, the recording layer 3-4 is smoother than the shape of the light reflecting layer 4-4 due to a decrease in wettability. The recording layer 3-4 is easily formed in a different shape. For this reason, the level difference in the recording layer 3-4 due to the effect of the wettability described above is such that the shape of the land 16 described above is narrower than, for example, the width of the land 16 and shallower than the depth of the land 16. A step in the recording layer 3-4 can be formed.

  In the present embodiment, the shape of the width and depth of the land 16 means the shape at the interface between the substrate 8 and the light reflecting layer 4-4. The level difference between the height of the land 16 and the height other than the land 16 at the interface between the substrate 8 and the light reflection layer 4-4 is called the depth of the land 16, and the width of the central portion of the level difference on the side surface of the land 16 is implemented in this embodiment. In the form, the width of the land 16 is defined. Accordingly, the level difference (depth) at the portion corresponding to the land 16 in the recording layer 3-4 is shallower than the depth of the land 16 according to the definition. Similarly, the width of the stepped portion at the portion corresponding to the land 16 in the recording layer 3-4 is narrower than the width of the land 16 according to the above definition.

The space layer 7 is formed of 2P resin (photopolymer). When the space layer 7 is formed, the recording layer 3-4 is partially damaged, and there is a problem that the stable recording layer 3-4 cannot be held. This is because when the liquid 2P resin is applied (by spinner coating) to form the space layer 7, the recording layer 3-4 made of a material that is soluble in an organic solvent is dissolved in the liquid 2P resin 2. This is because the recording layer 3-4 partially peels. In order to prevent this, in this embodiment, a barrier layer 6-4 is formed between the recording layer 3-4 and the space layer 7 to prevent damage to the recording layer 3-4 when the space layer 7 is formed. ing. The barrier layer 6-4 is vacuum-deposited using an oxide such as SiO ₂ , Si ₃ N ₄ , metal or semiconductor oxide, sulfide, nitride, carbide, or fluoride such as Ca, Mg, or Li. If it is formed by sputtering or the like, the manufacturing time is increased and the manufacturing cost is increased. However, in this embodiment, by selecting a material that can be formed by application (spinner coating) as the barrier layer 6-4, the formation time of the barrier layer 6-4 is greatly shortened, and the cost of the information storage medium is reduced. It is possible.

  In the present embodiment, the recording layer 3-4 is made of a material that is soluble in an organic solvent. For this reason, the barrier layer 6-4 cannot be formed with a solution using an organic solvent as a solvent. Therefore, the material constituting the recording layer 3-4 is soluble in an organic solvent, but has the property of being insoluble in water. In this embodiment, a water-soluble material that dissolves in water as the material of the barrier layer 6-4. Can be used. Specifically, for example, a water-soluble paint can be used. By using a water-soluble paint in which the barrier layer 6-4 is soluble in water, it is possible to prevent the recording layer 3-4 from being dissolved into a solution containing the barrier layer material when the barrier layer 6-4 is formed. As described above, when the water-soluble paint is used, the recording layer 3-4 is not peeled off when forming the barrier layer, and the shape and characteristics of the recording layer 3-4 are stably maintained, and the barrier layer 6-4 is maintained. Can be formed. In this embodiment, not only a water-soluble paint but also a material of the barrier layer 6-4 may be, for example, spin-on glass or gelatin (such as Yamato glue) that is soluble in water, or silicone that is soluble in water.

  In the present embodiment, the organic recording material constituting the recording layer 3-4 has a characteristic that it does not dissolve in polyvinyl alcohol (PVA), polyurethane vinyl alcohol, perfluoroether, von Prioni oil, or the like. Therefore, as another application example of the present embodiment, an organic material that can use PVA, polyurethane vinyl alcohol, perfluoroether, or von Prioni oil as a solvent can be selected as the material of the barrier layer 6-4. Specifically, nitrile rubber-based organic materials, silicone-based organic materials, urethane rubber-based organic materials that can use perfluoroether, vonprioni oil as a solvent, gelatin that can use PVA (polyvinyl alcohol) or polyurethane vinyl alcohol as a solvent, Use silicone organic materials. As a result, the recording layer 3-4 is not dissolved in the solution before forming the barrier layer when forming the barrier layer, and the barrier layer 6-4 is formed while maintaining the shape and characteristics of the stable recording layer 3-4.

  In this embodiment, as shown in FIG. 18, the surface of the barrier layer 6-4 looks relatively flat. However, when the barrier layer 6-4 is formed by application (spinner coating), as shown in FIG. 2, although it is actually influenced by the concave shape in the land 16 in the recording layer 3-4, a level difference is likely to occur. The unevenness on the surface of the barrier layer 6-4 is more relaxed than the unevenness on the substrate 8. Thus, since the unevenness | corrugation of the surface of barrier layer 6-4 is smooth | blunted to some extent, the space layer 7 becomes easy to form on it.

  As shown in FIG. 19, the space layer 7 is formed by applying an ultraviolet curable resin (2P resin) 2 and then transferring the concavo-convex shape based on the lands 16 and the pregroove 11 with a polycarbonate stamper 1-4. Specifically, the 2P resin 2 on the liquid is hung on the barrier layer 6-4 shown in FIG. 18, and then a polycarbonate stamper 1-4 having lands and grooves similar to the lands and grooves on the surface of the substrate. Is applied as shown in FIG. 19, and the entire substrate 8 is rotated to spread the 2P resin 2. At that time, the concavo-convex shape by the polycarbonate stamper 1-4 shaped land and groove is transferred. Thereafter, ultraviolet rays are irradiated from the polycarbonate stamper 1-4 side. The ultraviolet rays pass through the polycarbonate stamper 1-4 and enter the 2P resin 2. As a result, the 2P resin 2 is cured by being irradiated with ultraviolet rays.

  When the space layer 7 is formed from the 2P resin 2 in the process of FIG. 19, the uneven shape of the polycarbonate stamper 1-4 is transferred, the uneven state is formed on the surface of the space layer 7, and the pregroove 11 and the land 16 are formed. The On top of this, as shown in FIG. 20, a light semi-transmissive layer 4-3 is formed. In this embodiment, the light translucent layer 4-3 is made of silver bismuth AgBi and formed by sputtering or vacuum deposition. In this embodiment, when reproducing the information recorded on the recording layer 3-4, the laser light 9 must pass through the light semi-transmissive layer 4-3. Therefore, it is desirable that the thickness of the light semi-transmissive layer 4-3 be sufficiently thin, and it is desirable that the thickness is 100 nm or less. In the present embodiment, the thickness of the light semi-transmissive layer 4-3 can be set to 23 to 25 nm.

  After the formation of the light semi-transmissive layer 4-3, as shown in FIG. 20, the recording layer 3-3 is formed by a spinner coating method. As the material of the recording layer 3-3, an organometallic complex is used as in the recording layer 3-4. In the present embodiment, an azo metal complex in an organometallic complex can be used as a specific material of the recording layer 3-3.

  However, the recording layer 3-4 requires highly sensitive recording characteristics. That is, since the laser beam 9 reaches the recording layer 3-4 after passing through the recording layer 3-3 and the light semi-transmissive layer 4-3, the characteristic required for the recording layer 3-4 is high sensitivity. Required. On the other hand, in the recording layer 3-3, since the laser beam 9 must pass through to the recording layer 3-4, it is necessary to increase the light transmittance. Therefore, in the present embodiment, recording materials having different materials or different molecular structures can be used even with the same azo metal complex, corresponding to the performance required for the respective recording layers 3-4 and 3-3.

  As described above, since the thickness of the light reflection layer 4-4 is sufficiently thick, when viewed from the recording layer 3-4 formed thereon, the base has the same characteristics as the material of only silver bismuth AgBi, and the recording layer 3-4 The wettability with respect to the solution containing the recording material when forming the film is low. On the other hand, since the light semi-transmissive layer 4-3 is sufficiently thin, the characteristics of the underlying space layer 7 are reflected, and the wettability with respect to the solution containing the recording material when the recording layer 3-3 is formed is relative. To be high. As described above, the recording layer 3-3 is also formed by the spinner coating method. That is, a solution containing the recording material (azo metal complex) constituting the recording layer 3-3 is applied, and the solution is spread while rotating the substrate 8. At that time, the surface of the light translucent layer 4-3 is coated. Since the wettability to the solution is high, the recording layer 3-3 can well reproduce the uneven shape on the surface of the light semi-transmissive layer 4-3, that is, the shape of the land 16 and the pregroove 11.

  As a result, if the shape (width and depth) of the land 16 and the pregroove 11 on the substrate 8 is the same as the shape (width and depth) of the land 16 and the pregroove 11 on the surface of the space layer 7 In contrast to the recording layer 3-4, the recording layer 3-3 has a larger depth and a wider width of the pregroove 11. As a result, the signal amount of the wobble address signal from the land 16 and the pregroove 11 obtained from the recording layer 3-4 and the recording layer 3-3 changes.

  The wobble address information by the pregroove 11 shown in FIGS. 5 to 11 is required to be substantially equal from the layer 0 7-3 and the layer 1 7-4. For this reason, in this embodiment, the shape of the pregroove 11 on the surface of the space layer 7 is made different from the shape of the pregroove 11 on the surface of the substrate 8 in consideration of the wettability of the recording solution. Can do. As described above, since the recording layer 3-3 has higher wettability with respect to the solution used for forming the recording layer 3-4 than the recording layer 3-4, the concavo-convex shape in the land 16 and the pregroove 11 is better. The depth of the pregroove 11 of the space layer 7 can be made shallower than the depth of the substrate 8. From various experiments, it was found that the wobble signal amplitude can be made substantially equal by making the depth smaller than 95% of the depth smaller. Furthermore, the width of the pregroove 11 of the space layer 7 is changed from the width of the pregroove 11 of the substrate 8 in the direction in which the wobble detection signal amplitude becomes smaller.

  In this embodiment, as another method, instead of changing the shapes of the land 16 and the pregroove 11 on the surface of the space layer 7 and the surface of the substrate 8, the shape dimensions of both are made equal, and instead the wobble detection signal amplitude is reduced. As shown, the wobble amplitude of the pregroove 11 in the space layer 7 (layer 0 7-3 side) is made smaller than the wobble amplitude of the pregroove 11 (on the layer 1 7-4 side) on the substrate 8, and the layer 0 7- 3 and the wobble signal amplitude from the layer 1 7-4 can also be made substantially coincident. From various experimental results, it was found that the wobble signal amplitude can be made substantially equal by setting the small amplitude to 95% or less with respect to the large amplitude. Further, according to another aspect, it has been found that the wobble signal amplitude can be substantially matched by setting the small amplitude to 80% or less with respect to the large amplitude.

  Next, as shown in FIG. 21, the barrier layer 6-3 is formed on the recording layer 3-3. In the present embodiment, the material and forming method of the barrier layer 6-3 can be the same as those of the barrier layer 6-4 described above. Thereby, the manufacturing cost of an information storage medium can be reduced.

  Furthermore, in this embodiment, when forming the protective layer 5 formed on the barrier layer 6-3, the surface 12 of the protective layer is flattened by using the polycarbonate stamper 1-3 having a flat surface. be able to. Further, in order to improve the manufacturability, the protective layer 5 is a laminate of the protective layer 5-1 and the protective layer 5-2, and the film thickness per layer is reduced to improve the manufacturing efficiency and the film flatness. be able to. As shown in FIG. 21, a liquid 2P resin 2 is hung on the barrier layer 6-3, and a polycarbonate stamper 1-3 with flatness is placed on the resin layer 2-3. The resin 2 can be spread evenly in the information storage medium. Next, the 2P resin 2 is irradiated with ultraviolet rays through a polycarbonate stamper 1-3 to form a transparent protective layer 5-2.

  Further, as shown in FIG. 22, a liquid 2P resin 2 is dropped on the cured transparent protective layer 5-2 in the same manner as in FIG. 21, and the above-described polycarbonate stamper 1-3 having a flat surface is applied. The 2P resin 2 is spread over the entire information storage medium by being put again and rotated together with the substrate 8, and then the protective layer 5-1 is formed by irradiating the 2P resin 2 with ultraviolet rays through the polycarbonate stamper 1-3. .

  In the present embodiment, as shown in FIG. 1, the thickness t of the protective layer 5 can be set to 0.1 millimeter, for example. However, if the thickness t of the protective layer 5 is sufficiently thick as 0.1 millimeter, the viscosity of the liquid 2P resin 2 must be increased by application by spinner coating, and such a high viscosity 2P resin 2 is used. When the protective layer 5 is formed, it tends to be difficult to ensure uniformity in thickness within the information storage medium. On the other hand, when the protective layer 5 is separated into two layers as in this embodiment, the thickness of the single protective layer 5-1 or 5-2 may be 50 μm. When the thickness is about this, the viscosity required for the 2P resin 2 may be low, and the production is easy. Even if the thickness of the protective layer 5-2 is not uniform in the information storage medium, by arranging the polycarbonate stamper 1-3 at the stage of forming the protective layer 5-1, Further, it becomes possible to cancel the thickness unevenness in the protective layer 5-2. It is possible to ensure the uniformity of the thickness t of the information storage medium in the laminated state of the protective layers 5-2 and 5-1 when viewed in total. Compared with the formation method of the protective layer 5 using the 2P resin 2 by spinner coating, as shown in FIGS. 21 and 22, the polycarbonate stamper 1 is formed by forming the protective layer 5 using the polycarbonate stamper 1-3. Since the flatness of −3 is transferred, the thickness unevenness of the protective layer 5 can be greatly reduced.

  An organic stamper (polyolefin type) made of COP (cycloolefin polymer) is used as a stamper that transmits ultraviolet rays. However, since COP is expensive, the cost of the information storage medium is increased. On the other hand, by using an inexpensive polycarbonate that transmits ultraviolet rays as a stamper used when forming the transparent protective layer 5 as in the present embodiment, the manufacturing cost of the stamper 1-3 that ensures flatness is greatly reduced. . By frequently replacing the inexpensive polycarbonate stamper 1-3 with a new one, it is possible to prevent the stamper 1-3 from being affected by scratches and dirt, and to keep the price and quality of the information storage medium low. As shown in FIG. 1, the information storage medium thus prepared irradiates the recording layer 3-3 with a laser beam 9 through the transparent protective layer 5-1, the transparent protective layer 5-2, and the barrier layer 6.3. Or it can be regenerated. In addition, the recording layer 3-4 can be recorded or reproduced by passing through the light semi-transmissive layer 4-3, the space layer 7, and the barrier layer 6-4 and irradiating the recording layer 3-4 with the laser light 9.

  Next, the flatness of the surface 12 of the transparent protective layer and the uniformity of the thickness of the transparent protective layer 5 will be described. When the transparent protective layer 5 is formed on the 2P resin 2 by the spinner coating method, the thickness t of the transparent protective layer 5 may be reduced or increased at the inner peripheral portion or the outer peripheral portion of the information storage medium. When reproducing the data shown in FIG. 33 or FIG. 41 to FIG. 45 or recording such data, if the thickness t of the transparent protective layer 5 is locally thick as shown in FIG. There arises a problem that the recording or reproducing performance deteriorates due to spherical aberration at the optical head in the recording / reproducing apparatus.

  FIG. 23 is a perspective view showing a longitudinal section of a disk-shaped information storage medium according to an embodiment of the present invention. In this embodiment, since the flatness of the polycarbonate stamper 1-3 is transferred, the thickness t of the transparent protective layer 5 is uniform throughout the information storage medium as shown in FIG. As a result, it is possible to prevent film deterioration of the recording layer 3-3 and recording / reproduction signal characteristic deterioration due to water intrusion, and greatly improve the recording / reproduction performance of the information storage medium. In addition, according to the manufacturing method shown in the present embodiment, the cross-sectional shape at the boundary portion of the transparent protective layer 5 can have a great feature to be described later.

  FIG. 24 is an enlarged view of the cross section of the boundary portion of the transparent protective layer 5 in the inner peripheral portion of FIG. 23, and FIG. 25 shows the cross sectional shape of the outer peripheral portion of the transparent protective layer 5 shown in FIG. is there.

  When the manufacturing method of this embodiment is used, as shown in FIGS. 21 and 22, the 2P resin 2 that forms the transparent protective layer 5 is formed of a polycarbonate stamper 1-3 and a barrier layer 6-3 or a transparent protective layer 5-2. Therefore, the inclination angle θ of the side surface of the inner peripheral portion and the outer peripheral portion is close to 90 degrees. As a result of many experiments, when the flatness of the polycarbonate stamper 1-3 is transferred, the angle θ of the side surface of the boundary shown in FIGS. 24 and 25 can be ensured to be not less than 30 degrees and not more than 150 degrees. However, if such a stamper is not used, the angle θ of the cross section at the transparent protective layer boundary portion may be 30 degrees or less, or may exceed 150 degrees. Thus, by setting the angle of the side surface of the boundary portion at the outer periphery or the outer periphery of the transparent protective layer 5 to be in the range of 30 degrees to 150 degrees, the thickness t of the transparent protective layer 5 can be reduced to the inner peripheral portion of the information storage medium. It can be made uniform and the thickness t of the transparent protective layer 5 can be made uniform up to the very periphery, and stable recording or reproducing performance can be ensured over a wide range from the inner periphery to the outer periphery.

  Furthermore, when it is desired to make the thickness t of the transparent protective layer 5 uniform over a wider range from the inner peripheral portion to the outer peripheral portion of the information storage medium, the angle of the side surface at the boundary portion of the protective layer 5 is 45 degrees or more. It can be less than 135 degrees. Further, when it is intended to make the effective recording range of the information storage medium wider than that, and when it is desired to make the thickness t of the transparent protective layer 5 uniform over an even wider range from the inner peripheral portion to the outer peripheral portion, FIG. 24 and the side surface angle θ at the boundary portion of the protective layer 5 shown in FIG. 25 can be set to 60 degrees or more and 120 degrees or less.

  When the manufacturing method shown in FIGS. 1, 2, and 22 is used, it is easy to set the side surface angle θ at the boundary of the protective layer 5 within the range of 60 degrees to 120 degrees by appropriately managing the manufacturing conditions. It becomes.

  Next, specific materials for the recording layer 3-4 and the recording layer 3-3 shown in FIG. 1 will be described.

  As described above, the recording layer 3-4 requires high sensitivity, and the recording layer 3-3 requires high light transmittance. Therefore, the structure of the material used in accordance with the required performance, or contamination Is different. However, all the recording layers 3-4 and 3-3 are commonly used in azo metal complexes which are organometallic complexes. The common material and molecular structure of the recording layer 3-4 and the recording layer 3-3 will be described below.

§Common material and molecular structure in the recording layer Explanation of difference in reproduction signal between phase change recording film and organic dye recording film 2-1) Difference in recording principle / difference in recording film structure and basic concept regarding reproduction signal generation 26A shows a standard phase change recording film structure (mainly used for a rewritable information storage medium), and FIG. 26B shows a standard organic dye recording film structure (mainly write-once information). Used for storage media). In the description of this embodiment, the entire recording film structure (including the light reflection layers 4-1 and 4-2) excluding the transparent substrates 2-1 and 2-2 shown in FIG. It is defined and distinguished from the single recording layer 3-1, 3-2 in which the recording material is arranged. In recording materials that use phase change, the amount of change in optical characteristics between recorded areas (inside recorded marks) and unrecorded areas (outside recorded marks) is generally small. An enhanced structure is used. Therefore, in the phase change recording film structure, as shown in FIG. 26 (a), the base intermediate layer 5 is disposed between the transparent substrate 2-1 and the phase change recording layer 3-1, and the phase of the light reflecting layer 4-2 and the phase change recording layer 3-1. An upper intermediate layer 6 is arranged between the changeable recording layer 3-1. In this embodiment, polycarbonate PC or acrylic PMMA (polymethyl methacrylate), which is a transparent plastic material, is employed as the material for the transparent substrates 2-1 and 2-2. The center wavelength of the laser beam 7 used in the present embodiment is 405 nm, and the refractive indexes n ₂₁ and n ₂₂ of the polycarbonate PC at this wavelength are in the vicinity of 1.62. The standard refractive index n ₃₁ and absorption coefficient k ₃₁ at 405 nm of GeSbTe (germanium antimony tellurium), which is most commonly used as a phase change recording material, are n ₃₁ ≈1.5 and k in the crystalline region. ₃₁ amorphous region for ≒ 2.5 and has a _{n 31 ≒ 2.5, k 31 ≒} 1.8. Thus, the refractive index (in the amorphous region) of the phase change recording material is significantly different from the refractive index of the transparent substrate 2-1, and in the phase change recording film structure, the reflection of the laser beam 7 at the interface of each layer is performed. It is easy to happen. As described above, (1) the phase change recording film structure has an enhanced (emphasized) structure, and (2) there is a large difference in the refractive index between the layers. Changes in the amount of reflected light during reproduction (the difference between the reflected light amount from the recording mark and the reflected light amount from the unrecorded area) are the base intermediate layer 5, the recording layer 3-1, the upper intermediate layer 6, and the light reflective layer 4- It is obtained as a result of interference of multiple reflected light generated at each of the two interfaces. In FIG. 26A, the laser beam 7 is emitted from the interface between the base intermediate layer 5 and the recording layer 3-1, the interface between the recording layer 3-1 and the upper intermediate layer 6, and the upper intermediate layer 6 and the light reflecting layer. Although it appears that the light is reflected only at the interface with 4-2, the light reflected light amount change is actually obtained as a result of the interference between multiple reflected lights.

On the other hand, the organic dye recording film structure has a very simple laminated structure of only the organic dye recording layer 3-2 and the light reflecting layer 4-2. An information storage medium (optical disk) using this organic dye recording film is called a write-once information storage medium and can be recorded only once, but it is like a rewritable information storage medium using the phase change recording film. It is impossible to erase or rewrite information once recorded. The refractive index at 405 nm of a general organic dye recording material is n ₃₂ ≈1.4 (the refractive index range of various organic dye recording materials at 405 nm is n ₃₂ = 1.4 to 1.9), and the absorption coefficient There are many in the vicinity of k32≈0.2 (the absorption coefficient range at 405 nm of various organic dye recording materials is also k32≈0.1 to 0.2). Since the refractive index difference between the organic dye recording material and the transparent substrate 2-2 is small, the amount of light reflection at the interface between the recording layer 3-2 and the transparent substrate 2-2 hardly occurs. Therefore, the principle of optical reproduction from the organic dye recording film (the reason why the reflected light amount changes) is not “multiple interference” in the phase change recording film as described above, but “reflected by the light reflecting layer 4-2”. The main factor is the “light loss in the middle of the optical path (including interference)” with respect to the returning laser beam 7. Specific reasons for causing a light quantity loss in the middle of the optical path include “interference phenomenon due to phase difference partially caused in laser light 7” and “light absorption phenomenon in recording layer 3-2”. The light reflectance of the organic dye recording film in the unrecorded area on the mirror surface without pregrooves or prepits is the light when passing through the recording layer 3-2 from the light reflectance of the laser light 7 in the light reflecting layer 4-2. It is characterized in that it can be obtained simply by subtracting the absorption amount. As described above, there is a great difference from the phase change recording film in which the light reflectance is obtained by calculating “multiple interference”.

First, a description will be given of a recording principle that is interpreted as a conventional technique in the current DVD-R disc. In the current DVD-R disc, when the recording film is irradiated with the laser beam 7, the recording layer 3-2 locally absorbs the energy of the laser beam 7 and becomes hot. When the specific temperature is exceeded, the transparent substrate 2-2 is locally deformed. The mechanism for inducing the deformation of the transparent substrate 2-2 differs depending on the DVD-R disc manufacturer.
(1) The transparent substrate 2-2 is locally plastically deformed by the vaporization energy of the recording layer 3-2. (2) Heat is transferred from the recording layer 3-2 to the transparent substrate 2-2, and locally transparent by the heat. It is said that the substrate 2-2 is caused by plastic deformation. When the transparent substrate 2-2 is locally plastically deformed, it is reflected by the light reflecting layer 4-2 through the transparent substrate 2-2, and then returns to the optical path of the laser light 7 that passes through the transparent substrate 2-2 again. The target distance changes. The laser beam 7 from the recording mark returning through the part of the transparent substrate 2-2 locally plastically deformed, and the recording mark returning through the part of the transparent substrate 2-2 not deformed Since there is a phase difference with the laser beam 7 from the peripheral portion, the amount of reflected light changes due to interference between the two companies. In particular, when the mechanism (1) occurs, a substantial change in the refractive index n32 caused by cavitation of the recording mark of the recording layer 3-2 due to vaporization (evaporation), or within the recording mark. The change in the refractive index n32 caused by the thermal decomposition of the organic dye recording material contributes to the generation of the phase difference. In the current DVD-R disc, the recording layer 3-2 remains at a high temperature until the transparent substrate 2-2 is locally deformed (the vaporization temperature of the recording layer 3-2 in the mechanism (1) above, and transparent in the mechanism (2) above). The temperature inside the recording layer 3-2 required for plastic deformation of the substrate 2-2) or a high temperature is necessary to thermally decompose or vaporize (evaporate) a part of the recording layer 3-2. In order to form a recording mark, a large power of the laser beam 7 is required.

  In order to form a recording mark, it is necessary that the recording layer 3-2 can absorb the energy of the laser beam 7 as a first step. The light absorption spectrum in the recording layer 3-2 greatly affects the recording sensitivity of the organic dye recording film. The principle of light absorption in the organic dye recording material forming the recording layer 3-2 will be described with reference to (A3) of the present embodiment.

  Chemical formula 1 shows a specific structural formula of the specific content “(A3) azo metal complex + Cu” of the constituent elements of the information storage medium. A circular peripheral region centering on the central metal M of the azo metal complex shown in Chemical Formula 1 is the color developing region 8. When the laser beam 7 passes through the coloring region 8, the localized electrons in the coloring region 8 resonate with the electric field change of the laser beam 7 and absorb the energy of the laser beam 7. The value converted to the wavelength of the laser beam 7 with respect to the frequency of the electric field change at which the localized electrons resonate most easily and absorb energy is called the maximum absorption wavelength and is represented by λmax. As the length of the color development region 8 (resonance range) as shown in Chemical Formula 1 increases, the maximum absorption wavelength λmax shifts to the longer wavelength side. In addition, by changing the atom of the central metal M in the chemical formula 1, the localized range of localized electrons around the central metal M (how much the central metal M can attract the localized electrons to the center) changes, and the maximum absorption. The value of the wavelength λmax changes.

It is expected that the light absorption spectrum of the organic dye recording material in the case of absolute zero, high purity, and only one color developing region 8 will draw a narrow line spectrum near the maximum absorption wavelength λmax. In addition, the light absorption spectrum of a general organic dye recording material including a plurality of light absorption regions shows a broad absorption characteristic with respect to the wavelength of light centered on the maximum absorption wavelength λmax. An example of the light absorption spectrum of the organic dye recording material used in the current DVD-R disc is shown in FIG. In FIG. 27, the horizontal axis represents the wavelength of light applied to the organic dye recording film formed by applying the organic dye recording material, and the vertical axis represents the absorbance when the organic dye recording film is irradiated with light of each wavelength. Is taken. Absorbance refers to a state completed as a write-once information storage medium (or a state where only the recording layer 3-2 is formed on the transparent substrate 2-2 (the light reflecting layer 4-2 with respect to the structure of FIG. 26B). The laser light having the incident intensity Io is incident from the transparent substrate 2-2 side to the reflected laser light intensity Ir (the light intensity of the laser light transmitted from the recording layer 3-2 side). It is a value obtained by measuring It). Absorbance Ar (At) is Ar≡-log ₁₀ (Ir / Io) (A-1)
At≡-log ₁₀ (It / Io) (A-2)
It is represented by As long as there is no notice in the future, the absorbance will be described by showing the reflection type absorbance Ar expressed by the equation (A-1), but in the present embodiment, it is not limited to this and expressed by the equation (A-2). It can also be considered as the transmission type absorbance At. In the embodiment shown in FIG. 27, since there are a plurality of light absorption regions including the color development region 8, there are a plurality of positions where the absorbance is maximized. In this case, there are a plurality of maximum absorption wavelengths λ _max when the absorbance takes a maximum value. The wavelength of the recording laser beam in the current DVD-R disc is 650 nm. If the maximum absorption wavelength lambda _max was more present in the present embodiment, a value of the maximum absorption wavelength is close lambda _max to the wavelength of the recording laser light beam becomes important. Therefore, only in the description of the present embodiment, the value of the maximum absorption wavelength λ _max that is closest to the wavelength of the recording laser beam is defined as “λ”, and is distinguished from other λ _max (λ _max 0).

2-2) Difference in Light Reflecting Layer Shape in Prepit / Pregroove Area FIG. 28 shows a comparison of the formation shape of the recording film in the prepit area or the pregroove area 10. FIG. 28A shows the shape of the phase change recording film. When forming any of the base intermediate layer 5, the recording layer 3-1, the upper intermediate layer 6, and the light reflecting layer 4-1, any one of sputter vapor deposition, vacuum vapor deposition, or ion plating is used in vacuum. . As a result, the uneven shape of the transparent substrate 2-1 is replicated relatively faithfully in all layers. For example, when the cross-sectional shape in the pre-pit region or pre-groove region 10 of the transparent substrate 2-1 is rectangular or trapezoidal, the cross-sectional shapes of the recording layer 3-1 and the light reflecting layer 4-1 are also approximately rectangular or It becomes a trapezoid.

  FIG. 28B shows a general recording film cross-sectional shape of a current DVD-R disc which is a conventional technique as a recording film when an organic dye recording film is used. As a method for forming the recording film 3-2 in this case, a completely different method called spin coating (or spinner coding) is used unlike FIG. In spin coating, the organic dye recording material for forming the recording layer 3-2 is dissolved in an organic solvent and applied onto the transparent substrate 2-2, and then the transparent substrate 2-2 is rotated at high speed to apply the coating agent by centrifugal force. In this method, the recording layer 3-2 is formed by spreading to the outer peripheral side of the transparent substrate 2-2 and vaporizing an organic solvent. When this method is used, an organic solvent coating step is used, so that the surface of the recording layer 3-2 (interface with the light reflection layer 2-2) tends to be flat. As a result, the cross-sectional shape at the interface between the light reflecting layer 2-2 and the recording layer 3-2 is the surface shape of the transparent substrate 2-2 (interface between the transparent substrate 2-2 and the recording layer 3-2). Have different shapes. For example, in the pregroove region where the cross-sectional shape of the surface of the transparent substrate 2-2 (interface between the transparent substrate 2-2 and the recording layer 3-2) is a rectangle or a trapezoid, the light reflecting layer 2-2 and the recording layer 3 are used. -2 has a substantially V-shaped groove shape at the interface, and a substantially conical side surface shape in the prepit region. Furthermore, since the organic solvent tends to accumulate in the recesses during spin coating, the thickness Dg of the recording layer 3-2 in the prepit area or pregroove area 10 (as shown in FIG. 28B), the prepit area or pregroove area 10 The distance from the bottom surface to the lowest position of the interface with the light reflection layer 2-2) is significantly larger than the thickness Dl in the land region 12 (Dg> Dl). As a result, the unevenness amount at the interface between the transparent substrate 2-2 and the recording layer 3-2 in the prepit region or the pregroove region 10 is significantly larger than the unevenness amount at the interface between the transparent substrate 2-2 and the recording layer 3-2. It has become less.

As described above, the uneven shape at the interface between the light reflecting layer 2-2 and the recording layer 3-2 is dull and the uneven amount is greatly reduced. Therefore, the surface of the transparent substrate 2 (pre-pit region) is different depending on the recording film forming method. Alternatively, when the concave and convex shapes and dimensions of the pregroove region 10) are the same, the diffraction intensity of the reflected light from the organic dye recording film when irradiated with the laser light is significantly greater than the diffraction intensity of the reflected light from the phase change recording film. to degrade. As a result, when the surface of the transparent substrate 2 (pre-pit region or pre-groove region 10) has the same concavo-convex shape and dimensions, the conventional organic dye recording film is used in comparison with the phase change recording film. (1) The degree of modulation of the optical reproduction signal from the prepit area is small and the signal reproduction reliability from the prepit area is poor (2) A sufficiently large track deviation detection signal from the pregroove area by the push-pull method is difficult to obtain (3) There is a feature that it is difficult to obtain a sufficiently large wobble detection signal when the pre-groove area is wobbling (meandering).

  Further, in the DVD-R disc, specific information such as address information is recorded in the land area 12 in a minute unevenness (pit) shape, so that the width Wl of the land area 12 is larger than the width Wg of the prepit area or the pregroove area 10. Is wide (Wg> Wl).

3. Description of Features of Organic Dye Recording Film in Present Embodiment 3-1) Problems with High Density in Additional Recording Film (DVD-R) Using Conventional Organic Dye Material “2-1) Recording Principle / Recording Film Structure As described above in “Differences in Basics and Reproduction Signal Generation”, general recording of current DVD-R and CD-R, which are write-once information storage media using conventional organic dye materials The principle is accompanied by “local plastic deformation of the transparent substrate 2-2” or “local thermal decomposition and vaporization in the recording layer 3-2”. FIG. 29 shows a specific plastic deformation state of the transparent substrate 2-2 at the position of the recording mark 9 in the recordable information storage medium using a conventional organic dye material. There are two types of typical plastic deformation situations, and as shown in FIG. 29A, the depth of the bottom surface 14 of the pre-groove area at the position of the recording mark 9 (the amount of step between the adjacent land areas 12) is as shown. When the depth is different from the depth of the bottom surface of the pregroove area 11 in the unrecorded area (in the example shown in FIG. 29A, the depth of the bottom surface 14 of the pregroove area at the position of the recording mark 9 is shallower than that of the unrecorded area. 29), the bottom surface 14 of the pre-groove region at the position of the recording mark 9 is slightly distorted as shown in FIG. 29B (the flatness of the bottom surface 14 is broken: the example shown in FIG. 29B) In this case, the bottom surface 14 of the pre-groove area at the position of the recording mark 9 is slightly curved downward). In any case, there is a feature that the plastic deformation range of the transparent substrate 2-2 at the position of the recording mark 9 covers a wide area. The current DVD-R disc, which is a conventional technology, has a track pitch of 0.74 μm and a channel bit length of 0.133 μm. In the case of such a large value, a relatively stable recording process and reproducing process can be performed even when the plastic deformation range of the transparent substrate 2-2 at the position of the recording mark 9 is wide.

  However. If the track pitch is made narrower than the above 0.74 μm, the plastic deformation range of the transparent substrate 2-2 at the position of the recording mark 9 extends to a wide area, so that an adverse effect on the adjacent track appears, and the recording mark reaches the adjacent track. The phenomenon of “cross erase” occurs in which the recording mark 9 of the adjacent track that already exists due to multiple writing is substantially erased (made unreproducible). In addition, if the channel bit length in the direction along the track (circumferential direction) is narrower than 0.133 μm, intersymbol interference appears, and the error rate during reproduction greatly increases and the reproduction reliability decreases. Will occur.

3-2) Basic characteristics common to the organic dye recording film in the present embodiment 3-2-A] Range that requires application of the technique of the present embodiment Plasticity of the transparent substrate 2-2 as shown in FIG. How much the track pitch is reduced in a conventional write-once information storage medium (CD-R or DVD-R) with deformation or local thermal decomposition or vaporization phenomenon in the recording layer 3-2, or which is adversely affected The following will describe the results of a technical study of whether or not the adverse effect appears when the channel bit length is reduced to some extent. A range in which an adverse effect starts to occur when the conventional recording principle is used indicates a range in which an effect is exhibited by the novel recording principle shown in the present embodiment (suitable for high density).

(1) Conditions for the thickness Dg of the recording layer 3-2 If a thermal analysis is performed to theoretically determine the lower limit value of the allowable channel bit length and the lower limit value of the allowable track pitch, the recording layer 3- The range of the thickness Dg of 2 is important. In a conventional write-once information storage medium (CD-R or DVD-R) accompanied by plastic deformation of the transparent substrate 2-2 as shown in FIG. The change in the amount of light reflection when it is in the unrecorded area of the recording layer 3-2 has the largest factor of "interference effect due to the difference in optical distance between the recorded mark 9 and the unrecorded area". The difference in the optical distance is mainly “the thickness Dg of the physical recording layer 3-2 due to plastic deformation of the transparent substrate 2-2 (from the interface between the transparent substrate 2-2 and the recording layer 3-2 to the recording layer 3). "and" -2 and changes in physical distance) to the interface of the light reflection layer 4-2 changes in refractive index n ₃₂ of the recording layer 3-2 in the recording mark 9 ". Therefore, in order to obtain a sufficient reproduction signal (change in the amount of reflected light) between the recorded mark 9 and the unrecorded area, when the wavelength of the laser beam in vacuum is λ, The value of the thickness Dg of the recording layer 3-2 needs to have a certain size as compared with λ / n ₃₂ . Otherwise, the difference in optical distance (phase difference) between the recorded mark 9 and the unrecorded area does not appear, and the light interference effect becomes thin. Actually, at least Dg ≧ λ / 8n ₃₂ (1)
Desirably Dg ≧ λ / 4n ₃₂ (2)
These conditions are required.

For the time being, it is assumed that λ = 405 nm. The value of the refractive index _{n 32} of the organic dye recording material at 405nm is generally is in the range of 1.3 to 2.0. Accordingly, as a value of the thickness Dg of the recording layer 3-2, n32 = 2.0 is substituted into the equation (1),
Dg ≧ 25 nm (3)
Is an essential condition. Here, the conditions when the organic dye recording layer of a conventional write-once information storage medium (CD-R or DVD-R) with plastic deformation of the transparent substrate 2-2 is made to correspond to 405 nm light are examined. ing. As will be described later, in this embodiment, the change of the absorption coefficient k32 will be described as a main factor of the recording principle without causing plastic deformation of the transparent substrate 2-2, but from the recording mark 9 using a DPD (Differential Phase Detection) method. Since it is necessary to detect the track deviation, the refractive index n ₃₂ is actually changed in the recording mark 9. Therefore, the condition of the formula (3) is a condition that should be satisfied even in the present embodiment in which the transparent substrate 2-2 does not undergo plastic deformation.

From another viewpoint, the range of the thickness Dg of the recording layer 3-2 can be specified. In the case of the phase change recording film shown in FIG. 28 (a), when the refractive index of the transparent substrate is n21, the push-pull method is used to produce the largest track deviation detection signal between the prepit area and the land area. The step amount is λ / (8n21). However, in the case of the organic dye recording film shown in FIG. 28 (b), as described above, the shape at the interface between the recording layer 3-2 and the light reflecting layer 4-2 becomes dull and the level difference becomes small. The level difference between the prepit area and the land area on the substrate 2-2 needs to be larger than λ / (8n ₂₂ ). For example, when polycarbonate is used as the material of the transparent substrate 2-2, the refractive index at 405 nm is n ₂₂ ≈1.62, so the step amount between the prepit region and the land region needs to be larger than 31 nm. When the spin coating method is used, the recording layer 3 in the land area 12 must be formed unless the thickness Dg of the recording layer 3-2 in the pregroove area is larger than the step amount between the prepit area and the land area on the transparent substrate 2-2. There is a risk that the thickness Dl of -2 is lost. Therefore, from the above examination results, Dg ≧ 31 nm (4)
It is necessary to satisfy the condition. The condition of equation (4) is also a condition that should be satisfied in the present embodiment in which the transparent substrate 2-2 does not undergo plastic deformation. Although the conditions of the lower limit value are shown by the expressions (3) and (4), n32 = 1.8 is substituted for the equal sign part of the expression (2) as the thickness Dg of the recording layer 3-2 used in the thermal analysis. The value Dg≈60 nm obtained was used.

Then, assuming that polycarbonate is used as a standard material for the transparent substrate 2-2, 150 ° C., which is a glass transition temperature of polycarbonate, is set as an estimated value of the thermal deformation temperature on the transparent substrate 2-2 side. In the examination using thermal analysis, a value of k ₃₂ = 0.1 to 0.2 was assumed as the value of the absorption coefficient of the organic dye recording film 3-2 at 405 nm. Furthermore, the NA value of the focusing objective lens and the incident light intensity distribution when passing through the objective lens are NA = 0.60 and H format ((D1): NA = 0.0), which are preconditions for the conventional DVD-R format. 65) and B format ((D2): NA = 0.85) were examined.

(2) Channel bit length lower limit condition When the recording power is changed, the length change in the direction along the track of the region reaching the thermal deformation temperature on the transparent substrate 2-2 side in contact with the recording layer 3-2 is changed. We examined the lower limit of allowable channel bit length considering the window margin during playback. As a result, if the channel bit length is made smaller than 105 nm, the length change in the direction along the track in the region reaching the thermal deformation temperature on the transparent substrate 2-2 side according to a slight change in recording power occurs. It is thought that the wind margin cannot be taken. In the study of thermal analysis, a similar tendency is shown in all cases of NA values of 0.60, 0.65, and 0.85. Although the condensing spot size changes by changing the NA value, it is considered that the heat spread range is wide (the gradient of the temperature distribution on the transparent substrate 2-2 side in contact with the recording layer 3-2 is relatively gentle). It is done. In the thermal analysis, since the temperature distribution on the transparent substrate 2-2 side in contact with the recording layer 3-2 is examined, the influence of the thickness Dg of the recording layer 3-2 does not appear.

  Furthermore, when the shape change of the transparent substrate 2-2 shown in FIG. 29 occurs, the boundary position of the substrate deformation region is blurred (unclear), and the window margin is further reduced. When the cross-sectional shape of the region where the recording mark 9 is formed is observed with an electron microscope, it is considered that the amount of blur at the boundary position of the substrate deformation region increases as the value of the thickness Dg of the recording layer 3-2 increases. In consideration of the blur of the boundary position of the substrate deformation region in consideration of the influence of the heat deformation region length due to the change in the recording power, the lower limit value of the allowable channel bit length for securing a sufficient window margin is the recording layer 3-2. It is considered that about twice the thickness Dg is necessary, and it is desirable that the thickness is larger than 120 nm.

  In the above, the examination by the thermal analysis when the thermal deformation of the transparent substrate 2-2 occurs is mainly described. As another recording principle (mechanism for forming the recording mark 9) in the conventional write-once information storage medium (CD-R or DVD-R), the plastic deformation of the transparent substrate 2-2 is very little and the recording layer 3-2 There are cases where the thermal decomposition and vaporization (evaporation) of the organic dye recording material is the center. The vaporization (evaporation) temperature of the organic dye recording material varies depending on the organic dye material, but is generally in the range of 220 ° C. to 370 ° C., and the thermal decomposition temperature is lower. In the above examination, the glass transition temperature of the polycarbonate resin is assumed to be 150 ° C. as the temperature at the time of substrate deformation, but the temperature difference between 150 ° C. and 220 ° C. is small, and when the transparent substrate 2-2 reaches 150 ° C. It exceeds 220 ° C. inside the recording layer 3-2. Therefore, although there are exceptions due to the organic dye recording material, even if the plastic deformation of the transparent substrate 2-2 is very small, the thermal decomposition or vaporization (evaporation) of the organic dye recording material in the recording layer 3-2 is the main. The result is almost the same as the above examination result.

  Summarizing the results of the study on the channel bit length, in conventional write-once information storage media (CD-R and DVD-R) that involve plastic deformation of the transparent substrate 2-2, the window margin is reduced when the channel bit length is made smaller than 120 nm. It is thought that stable reproduction becomes difficult when the thickness is smaller than 105 nm. That is, when the channel bit is smaller than 120 nm (105 nm), the effect of using the new recording principle shown in this embodiment is exhibited.

(3) Lower limit condition of track pitch When the recording layer 3-2 is exposed with recording power, energy is absorbed in the recording layer 3-2 and the temperature becomes high. In a conventional write-once information storage medium (CD-R or DVD-R), it is necessary to absorb energy in the recording layer 3-2 until the transparent substrate 2-2 reaches the heat distortion temperature. The temperature at which the structural change of the organic dye recording material occurs in the recording layer 3-2 and the values of the refractive index n32 and the absorption coefficient k32 start changing is much higher than the temperature at which the transparent substrate 2-2 starts thermal deformation. Very low. Accordingly, the values of the refractive index n ₃₂ and the absorption coefficient k ₃₂ change in a relatively wide area in the recording layer 3-2 around the recording mark 9 where the transparent substrate 2-2 side is thermally deformed, and this changes to the adjacent track. It seems to be the cause of “cross light” and “cross erase”. “Cross light” or “Cross” in the width of the region reaching the temperature for changing the refractive index n ₃₂ and the absorption coefficient k ₃₂ in the recording layer 3-2 when the transparent substrate 2-2 side exceeds the thermal deformation temperature. The lower limit of the track pitch that does not cause “erase” can be set. From the above viewpoint, it is considered that “cross light” and “cross erase” occur when the track pitch is 500 nm or less. Further, in consideration of the influence of the warp and tilt of the information storage medium and the change in recording power (recording power margin), the conventional energy absorption is performed in the recording layer 3-2 until the transparent substrate 2-2 reaches the thermal deformation temperature. It can be concluded that it is difficult to make the track pitch 600 nm or less in the recordable information storage medium (CD-R or DVD-R). As described above, even if the NA value is changed to 0.60, 0.65, and 0.85, in the recording layer 3-2 around the center when the transparent substrate 2-2 reaches the thermal deformation temperature. The gradient of the temperature distribution is relatively gentle and the heat spread range is wide, so the same tendency is shown. As another recording principle (mechanism for forming the recording mark 9) in the conventional write-once information storage medium (CD-R or DVD-R), the plastic deformation of the transparent substrate 2-2 is very little and the recording layer 3-2 Even when the thermal decomposition and vaporization (evaporation) of organic dye recording materials at the center is, the “cross light” and “cross erase” are already described in “(2) Lower limit condition of channel bit length”. The starting track pitch values give almost similar results. For the above reasons, the effect of using the new recording principle shown in the present embodiment is exhibited when the track pitch is 600 nm (500 nm) or less.

3-2-B] Basic features common to the organic dye recording material in this embodiment As described above, the recording principle (formation of the recording mark 9) in the conventional write-once information storage medium (CD-R or DVD-R) When the transparent substrate 2-2 is accompanied by plastic deformation as a mechanism) or when local thermal decomposition or vaporization (evaporation) occurs in the recording layer 3-2, the recording layer 3-2 is formed when the recording mark 9 is formed. Since the inside and the surface of the transparent substrate 2-2 reach a high temperature, there arises a problem that the channel bit length and the track pitch cannot be reduced. As a solution to the above problem, the present embodiment does not cause substrate deformation or vaporization (evaporation) in the recording layer 3-2. “Local optical characteristic change in the recording layer 3-2 that occurs at a relatively low temperature” As a recording principle ”
The major features are the “invention of the organic dye material” and the “setting of the environment (recording film structure and shape)” in which the above recording principle is likely to occur. The following contents can be raised as specific features of the present embodiment.

α] As a method for changing the optical characteristics in the recording layer 3-2: Change in color development characteristics: Change in light absorption cross section or change in molar absorption coefficient due to qualitative change in color development area 8 (Chemical formula 1)
The light absorption spectrum (FIG. 27) profile (characteristics) itself is preserved while the light absorption spectrum (FIG. 27) is preserved by partially destroying the color development region 8 or changing the substantial light absorption cross section by changing the size of the color development region 8. The amplitude (absorbance) at the position of _{max write} changes in the recording mark 9 ・ Change in the electronic structure (electron orbital) with respect to electrons contributing to the color development phenomenon… Local electron orbital break (dissociation of local molecular bonds) Change in optical absorption spectrum (Fig. 27) based on decoloring action and changes in size and structure of color development region 8 (Chemical Formula 1)-Changes in orientation (or intermolecular) orientation and arrangement in molecule ... For example, shown in Chemical Formula 1 Optical property change based on orientation change inside azo metal complex ・ Molecular structure change inside molecule… For example, bond dissociation between anion part and cation part or either anion part or cation part An organic dye material is devised that either undergoes thermal decomposition of the carbon or destroys the molecular structure itself and causes tarring (degradation into black coal tar) in which carbon atoms are deposited. As a result, the refractive index n ₃₂ and the absorption coefficient k ₃₂ in the recording mark 9 are changed with respect to the unrecorded area, thereby enabling optical reproduction.

[beta]] The recording film structure and shape that are likely to cause the change in the optical characteristics of [[alpha]] are set stably. For specific contents regarding this technique, "3-2-C", the recording principle shown in the present embodiment is generated. This will be described in detail after the “ideal recording film structure that can be easily formed”.

[gamma]] The recording power is lowered in order to form a recording mark in a state where the recording layer and the transparent substrate surface are at a relatively low temperature. -2 occurs at a temperature below the vaporization (evaporation) temperature in -2. Therefore, the exposure amount (recording power) at the time of recording is lowered to prevent the deformation temperature from being exceeded on the surface of the transparent substrate 2-2 and the vaporization (evaporation) temperature from being exceeded in the recording layer 3-2. This content will be described in detail later in “3-3) Recording characteristics common to the organic dye recording film in the present embodiment”. Conversely, by examining the value of the optimum power during recording, it is possible to determine whether or not the optical characteristic change indicated by [α] has occurred.

δ] Stabilizes the electronic structure in the color development region and makes it difficult for structural decomposition to occur when irradiated with ultraviolet rays or reproduction light. Irradiation of the recording layer 3-2 with ultraviolet rays or reproduction light during reproduction is performed on the recording layer 3-2. , The temperature in the recording layer 3-2 rises. In addition to preventing the deterioration of the characteristics due to the temperature rise, seemingly contradictory performance is required in terms of temperature characteristics of recording at a temperature lower than the substrate deformation temperature and the vaporization (evaporation) temperature in the recording layer 3-2. In the present embodiment, the seemingly contradictory performance is ensured by “stabilizing the electronic structure in the coloring region”. The specific technical contents will be described in “Chapter 4 Description of Specific Embodiment of Organic Dye Recording Film in Present Embodiment”.

[epsilon]] Improves the reliability of the reproduction information in case the reproduction signal deteriorates due to the irradiation of ultraviolet rays or reproduction light. In this embodiment, the technical device for "stabilizing the electronic structure in the coloring region" However, when compared with a local cavity in the recording layer 3-2 generated by plastic deformation or vaporization (evaporation) on the surface of the transparent substrate 2-2, the recording formed by the recording principle shown in the present embodiment is performed. It must be said that the reliability of the mark 9 is reduced in principle. As a countermeasure, in the present embodiment, as described later in “Chapter 7 Explanation of H Format” and “§1. Explanation of B Format”, the density is increased by combining with a powerful error correction capability (new ECC block structure). And the reliability of recording information is achieved at the same time. Further, in the present embodiment, as described in “4-2) Description of the reproduction circuit in the present embodiment, a PRML (Pertial Response Maximum Likelyhood) method is adopted as a reproduction method, which is combined with an error correction technique at the time of ML demodulation. As a result, it is possible to achieve higher density and ensure the reliability of recorded information at the same time.

Among the specific features of the present embodiment, [α] to [γ] are technically devised in this embodiment in order to realize “narrow track pitch” and “narrow channel bit length”. I already explained that it was a devised content. In addition, “narrow channel bit lengthening” also leads to “reduction of minimum recording mark length”. The meaning (purpose) of the present embodiment regarding the remaining [δ] and [ε] will be described in detail. In the present embodiment, the passing speed (linear velocity) of the focused spot passing through the recording layer 3-2 during reproduction in the H format is set to 6.61 m / s, and the linear velocity in the B format is 5.0 to 10. Set in the range of 2m / s. In any case, the linear velocity during reproduction in this embodiment is 5 m / s or more. The start position of the data lead-in area DTLDI in the H format is 47.6 mm in diameter, and user data is recorded at a diameter of 45 mm or more even when the B format is taken into view. Since the circumference having a diameter of 45 mm is 0.141 m, the number of rotations of the information storage medium when this position is reproduced at a linear speed of 5 m / s is 35.4 rotations / s. One method of using the recordable information storage medium of this embodiment is recording video information such as a TV program. For example, when the user presses a “pause (pause) button” during playback of a video recorded by the user, the reproduction focused spot remains on the track at the pause position. If it is stopped on the track at the pause position, playback can be started from the pause position immediately after the user presses the “play start button”. For example, if a visitor arrives immediately after the user presses the “pause (pause) button” to get up, he may be left with the pause button pressed for 1 hour. The write-once information storage medium has rotated 35.4 × 60 × 60≈130,000 revolutions in one hour, and the focused spot traces on the same track all the time (repeatedly reproduced 130,000 times). In the meantime, if the recording layer 3-2 is repeatedly reproduced and deteriorated and the reproduction of the video information becomes impossible, the user who came back after 1 hour is angry because he cannot see a part of the video, and in the worst case There is a risk of becoming a trial. Therefore, it is necessary to guarantee that even if the recorded video information is not destroyed even if it is left for about one hour (continuous reproduction within the same track), it does not deteriorate even if it is repeatedly reproduced at least 100,000 times. As a general user use situation, it is rare to repeat the pause (repeat playback) for one hour for the same place 10 times. Therefore, as long as the repetitive reproduction of 1 million times is desirably ensured as the recordable information storage medium of the present embodiment, there is no problem for general user use, and the upper limit of the number of repetitive reproductions that does not deteriorate the recording layer 3-2. It is considered sufficient to set the value to about 1 million times. If the upper limit value of the number of repeated playbacks is set to a value that greatly exceeds one million times, inconveniences such as “the recording sensitivity is lowered” and “the medium price is raised” occur.

When the upper limit value of the number of repeated reproductions is guaranteed, the reproduction power value is an important factor. In the present embodiment, the recording power is defined within a range set by equations (8) to (13) described later. As a characteristic of a semiconductor laser, it is said that continuous light emission is not stable at a value of 1/80 or less of the maximum use power. At the power of 1/80 of the maximum use power, light emission is finally started (the mode starts standing), so that it is easy to mode hop. Therefore, this light emission power generates “return light noise” in which the amount of light emission always fluctuates when the light reflected by the light reflection layer 4-2 of the information storage medium returns to the semiconductor laser light source. Therefore, in this embodiment, the value of the reproduction power is based on the value of 1/80 of the value described on the right side of the equation (12) or (13) [Optimum reproduction power]
> 0.19 × (0.65 / NA) 2 × (V / 6.6) (B-1)
[Optimum playback power]
> 0.19 × (0.65 / NA) 2 × (V / 6.6) 1/2 (B-2)
Is set.

  The optimum reproduction power value is limited by the dynamic range of the power monitor photodetector. An optical head for recording / reproducing exists in the information recording / reproducing unit. This optical head incorporates a photodetector for monitoring the light emission amount of the semiconductor laser light source. In the present embodiment, in order to improve the light emission accuracy of the reproduction power during reproduction, this light detector detects the amount of light emission and applies feedback to the amount of current supplied to the semiconductor laser light source during light emission. In order to reduce the price of the optical head, it is necessary to use a very inexpensive photodetector. In many cases, commercially available inexpensive photodetectors are molded with resin (the light detection portion is surrounded).

  “The light source wavelength in this embodiment is 530 nm or less (especially 455 nm or less). In this wavelength region, the resin (mainly epoxy type) that molds the photodetection part emits ultraviolet light when irradiated with the wavelength light. Deterioration that occurs when irradiated (discoloration to a turbid color or generation of cracks (fine white streaks), etc.) occurs and deteriorates the light detection characteristics, particularly in the case of the write-once information storage medium shown in this embodiment. 31 has a pre-groove area 11 as shown in Fig. 31 and is liable to cause deterioration of the mold resin. In most cases, the “knife edge method” is employed in which a photodetector is arranged at an image position (imaging magnification M is about 3 to 10 times). Then, since the light is collected on the photodetector, the light density irradiated on the mold resin is increased, and the resin is easily deteriorated by the light irradiation. The upper limit of the allowable dose can be predicted by comparing with the light dose in the thermal mode (thermal excitation), and a photodetector is placed at the imaging position as an optical head assuming the worst state. Assume an optical system.

From the content described in “(1) Conditions for Thickness Dg of Recording Layer 3-2” within “3-2-A] Range of Application of Technology of Present Embodiment”, the recording layer at the time of recording in the present embodiment When the optical characteristic change (thermal mode) occurs in 3-2, it is considered that the temperature temporarily rises in the range of 80 ° C. to 150 ° C. in the recording layer 3-2. Assuming that the room temperature is around 15 ° C., the temperature difference ΔT _write is 65 ° C. to 135 ° C. Since pulse emission is performed during recording but continuous emission is performed during reproduction, the temperature rises in the recording layer 3-2 during reproduction, and a temperature difference ΔT _read is generated. If the imaging magnification of the detection system in the optical head is M, the light density of the detection light condensed on the photodetector is 1 / M2 of the light density of the convergent light irradiated on the recording layer 3-2. Therefore, the amount of temperature rise on the photodetector during reproduction is ΔT _read / M2 as a rough estimate. Considering that the mold resin deterioration occurs in the photon mode, it is considered that ΔT _read / M2 ≦ 1 ° C. when the upper limit value of the light density that can be irradiated on the photodetector is converted into a temperature rise amount. Since the imaging magnification of the detection system in the optical head is generally about 3 to 10 times, if it is temporarily estimated that M2≈10,
ΔT _read / ΔT _write ≦ 20 (B-3)
It is necessary to set the reproduction power so that If the duty ratio of the recording pulse at the time of recording is estimated to be 50%, [optimum reproduction power] ≦ [optimum recording power] / 10 (B-4)
Is required. Therefore, the optimum reproduction power is calculated by adding the following expressions (8) to (13) and the above expression (B-4): [optimum reproduction power]
<3 × (0.65 / NA) 2 × (V / 6.6) (B-5)
[Optimum playback power]
<3 × (0.65 / NA) 2 × (V / 6.6) 1/2 (B-6)
[Optimum playback power]
<2 × (0.65 / NA) 2 × (V / 6.6) (B-7)
[Optimum playback power]
<2 × (0.65 / NA) 2 × (V / 6.6) 1/2 (B-8)
[Optimum playback power]
<1.5 × (0.65 / NA) 2 × (V / 6.6) (B-9)
[Optimum playback power]
<1.5 × (0.65 / NA) 2 × (V / 6.6) 1/2 (B-10)
(Refer to “3-2-E] Basic characteristics regarding thickness distribution of recording layer in this embodiment” for the definition of each parameter.)
Given in. For example, when NA = 0.65 and V = 6.6 m / s, [optimum reproduction power] <3 mW,
[Optimum playback power] <2mW,
Or [optimum playback power] <1.5mW
It becomes. Actually, the optical detector is fixed as compared with the information storage medium that rotates and moves relatively, so that the optimum reproduction power is further taken into account by taking this into consideration. Must be less than or equal to In the information recording / reproducing apparatus in this embodiment, the value of the reproduction power is set to 0.4 mW.

3-2-C] Ideal recording film structure in which the recording principle shown in the present embodiment is easy to be generated In the present embodiment, the “environment (recording film structure and shape) setting” method in which the recording principle is likely to occur is described. explain.

As described above, the environment in which the optical characteristics inside the recording layer 3-2 are likely to change is described as follows. The surface of the transparent substrate 2-2 near the center of the recording mark 9 does not exceed the thermal deformation temperature. ”
As described above, the technical features of the recording film structure and shape are as follows.

  Specific contents regarding the above will be described with reference to FIG. In FIG. 30, a hollow arrow indicates an optical path of the irradiation laser beam 7, and a broken arrow indicates a heat flow. The recording film structure shown in FIG. 30A shows an environment in which the optical characteristic change in the recording layer 3-2 corresponding to this embodiment is most likely to occur. That is, in FIG. 30A, the recording layer 3-2 made of the organic dye recording material has a uniform thickness throughout the range (sufficiently thick) in the range indicated by the formula (2) or the formula (4). The laser beam 7 is irradiated from a direction perpendicular to -2. As will be described later in detail in “6-1) Light Reflecting Layer (Material and Thickness)”, in this embodiment, a silver alloy is used as the material of the light reflecting layer 4-2. A material including a metal having a high light reflectance, not limited to a silver alloy, generally has a high thermal conductivity and a heat dissipation characteristic. Therefore, the energy of the irradiated laser beam 7 is absorbed and the temperature of the recording layer 3-2 rises, but heat is released toward the light reflecting layer 4-2 having heat dissipation characteristics. Since the recording film shown in FIG. 30 (a) has a uniform shape everywhere, a relatively uniform temperature rise occurs inside the recording layer 3-2, and at the central α point, β point, and γ point. The temperature difference is relatively small. Therefore, when the recording mark 9 is formed, when the temperature exceeds the critical temperature at which the optical characteristics change at the β point and the γ point, the central α point is closest to the central α point without exceeding the vaporization (evaporation) temperature. The surface of the transparent substrate (not shown) does not exceed the heat distortion temperature.

  In contrast, when there is a step in a part of the recording film 3-2 as shown in FIG. 30B, the δ point and the ε point are inclined from the direction in which the recording layer 3-2 is arranged. Since the laser beam 7 is irradiated, the irradiation amount of the laser beam 7 per unit area is relatively decreased as compared with the central α point, and as a result, the recording layer 3-2 at the δ point and the ε point is reduced. Temperature rise is reduced. Since there is heat emission toward the light reflecting layer 4-2 at the δ point and the ε point, the temperature reached at the δ point and the ε point is significantly lower than that at the central α point. For this reason, heat flows from the β point to the δ point and heat flows from the γ point to the ε point, so the temperature difference between the β point and the γ point with respect to the central α point becomes very large. During recording, the amount of temperature rise at the β and γ points is low and does not exceed the critical temperature at which changes in optical characteristics occur at the β and γ points. As a countermeasure, it is necessary to increase the exposure amount (recording power) of the laser beam 7 in order to cause a change in optical characteristics at the β point and the γ point (in order to make it higher than the critical temperature). In the recording film structure shown in FIG. 30B, the temperature difference between the β point and the γ point at the center α point is very large. Therefore, when the temperature rises to the temperature at which the optical characteristics change at the β point and the γ point, the center α The vaporization (evaporation) temperature is exceeded at a point, or the surface of a transparent substrate (not shown) near the center α point is likely to exceed the thermal deformation temperature.

  Further, even when the surface of the recording layer 3-2 on the receiving side of the laser beam 7 is perpendicular to the irradiation direction of the laser beam 7, the thickness of the recording layer 3-2 varies depending on the location. The structure is difficult to cause the optical characteristic change in the recording layer 3-2 of the present embodiment. For example, as shown in FIG. 30C, the thickness Dl of the peripheral portion is significantly thinner than the thickness Dg of the recording layer 3-2 at the center α point (for example, the equations (2) and (4) are If you are not satisfied). Although heat is emitted toward the light reflecting layer 4-2 even at the center α point, since the recording layer 3-2 has a sufficiently thick thickness Dg, it can accumulate heat and reach a high temperature. In contrast, since the heat is released toward the light reflecting layer 4-2 without sufficiently storing heat at the ζ point and η point where the thickness of the recording layer 3-2 is D1 significantly smaller, the temperature rise amount is increased. Few. As a result, not only the release of heat toward the light reflection layer 4-2, but also the release of heat from the β point → δ point → ζ point, or the release of heat from the γ point → ε point → η point, Similar to FIG. 30B, the temperature difference between the β point and the γ point at the center α point becomes very large. If the exposure amount (recording power) of the laser beam 7 is increased to cause a change in optical characteristics at the β point and the γ point (in order to make the temperature higher than the critical temperature), the vaporization (evaporation) temperature may be exceeded at the central α point or the center. The surface of the transparent substrate (not shown) in the vicinity of the part α is likely to exceed the heat distortion temperature.

  Based on the above-described content, the technical contents and the thickness of the recording layer in the present embodiment regarding the pre-groove shape / dimension for performing “setting of environment (recording film structure and shape)” in which the recording principle of the present embodiment is likely to occur The technical contrivance contents in this embodiment regarding the distribution will be described with reference to FIG. FIG. 31A shows a recording film structure in a conventional write-once information storage medium such as a CD-R or DVD-R, and FIGS. 31B and 31C show a recording film structure in the present embodiment. In this description, the recording mark 9 is formed in the pre-groove area 11 as shown in FIG.

3-2-D] Basic Characteristics Regarding Pregroove Shape / Dimension in the Present Embodiment As shown in FIG. 31A, in the conventional write-once information storage medium such as CD-R and DVD-R, the pregroove area 11 has In many cases, it had a “V-groove” shape. In the case of this structure, as described with reference to FIG. 30B, the energy absorption efficiency of the laser light 7 is low, and the temperature distribution unevenness in the recording layer 3-2 is very large. In order to approach the ideal state of FIG. 30A, the feature of the present embodiment is that at least “a planar region perpendicular to the traveling direction of the incident laser beam 7 is provided in the pregroove region 11 on the transparent substrate 2-2 side”. Yes. As described with reference to FIG. 30A, it is desirable to make this plane area as wide as possible. Therefore, not only the planar area is provided in the pregroove area 11, but also the width Wg of the pregroove area is larger than the width Wl of the land area (Wg> Wl). In this description, the width Wg of the pre-groove area and the width Wl of the land area are set to a plane having an intermediate height between the height at the plane position of the pre-groove area and the height at the highest position of the land area. It is defined as each width at the position where the slope of the crossing.

  Data is recorded in a recordable information storage medium that has been studied by thermal analysis and actually manufactured, and substrate deformation is observed by a cross-sectional SEM (scanning electron microscope) image at the position of the recording mark 9, and vaporization (evaporation) in the recording layer 3-2 is performed. As a result of repeating the observation of the presence or absence of cavities generated by (1), it was found that there is an effect by making the width Wg of the pregroove region wider than the width Wl of the land region (Wg> Wl). Furthermore, the ratio of the pre-groove area width Wg to the land area width Wl is made larger than Wg: Wl = 6: 4, preferably Wg: Wl = 7: 3, so that the recording layer 3-2 can be more stably recorded. It is considered that local optical characteristic changes are likely to occur in the inside. When the difference between the pre-groove region width Wg and the land region width Wl is increased in this way, a flat surface is eliminated on the land region 12 as shown in FIG. In the conventional DVD-R disc, pre-pits (land pre-pits: not shown) are formed in the land area 12, and the address information and the like are recorded in advance here. Therefore, it is indispensable to form a flat region in the land region 12, and as a result, the pregroove region 11 often has a “V-groove” shape. In the conventional CD-R disc, a wobble signal is input to the pre-groove area 11 by frequency modulation. In a conventional frequency modulation method using a CD-R disc, the slot interval (details will be described later in the description of each format) is not constant, and phase alignment (PLL: PhaseLockLoop synchronization) at the time of wobble signal detection is relatively was difficult. For this reason, the wall surface of the pre-groove region 11 is concentrated near the center where the intensity of the reproduction focused spot is the highest (close to the V-groove) and the wobble amplitude is increased to guarantee the wobble signal detection accuracy. As shown in FIGS. 31B and 31C, the flat region in the pre-groove region 11 in the present embodiment is widened, and the inclined surface of the pre-groove region 11 is relatively outward from the center position of the reproduction focused spot. If moved, it becomes difficult to obtain a wobble detection signal. In the present embodiment, the width Wg of the pre-groove area is increased, and the H format or FSK (Frequency Shift Keying) using phase modulation (PSK: Phase Shift Keying) in which the slot interval at the time of wobble detection is always kept fixed. By combining the B format using STW (Saw Tooth Wobble), it is possible to guarantee stable recording characteristics with low recording power (suitable for high-speed recording and multi-layering) as well as stable wobble signal detection characteristics. There is a big feature. In particular, in the H format, in addition to the above combinations, “lower the wobble modulation area ratio than the non-modulation area” makes it easier to synchronize when detecting wobble signals, and further stabilizes the wobble signal detection characteristics. I am letting.

3-2-E] Basic characteristics regarding thickness distribution of recording layer in this embodiment In this description, as shown in FIGS. 31B and 31C, the thickest recording layer 3-2 in the land area 12 is shown. Is defined as the recording layer thickness Dl in the land area, and the thickness at the thickest recording layer 3-2 in the pregroove area 11 is defined as the recording layer thickness Dg in the pregroove area. As already described with reference to FIG. 30C, the recording layer thickness Dl in the land area is relatively increased, so that local optical characteristic changes can easily occur in the recording layer 3-2 during recording. Become.

  In the same manner as described above, thermal analysis is performed and data is recorded on a recordable information storage medium that is actually manufactured, and the deformation of the substrate is observed by a cross-sectional SEM (scanning electron microscope) image at the position of the recording mark 9 and in the recording layer 3-2. As a result of repeated observation of the presence or absence of cavities caused by vaporization (evaporation), the ratio of the recording layer thickness Dg in the pre-groove area to the recording layer thickness Dl in the land area is at most Dg: Dl = 4: 1 or less. There is a need to do. Furthermore, when Dg: Dl = 3: 1 or less, preferably Dg: Dl = 2: 1 or less, the stability of the recording principle in this embodiment can be guaranteed.

3-3) Recording characteristics common to the organic dye recording film in the present embodiment As described in [γ] as one of “3-2-B] Basic features common to the organic dye recording material in the present embodiment” Recording power control is a major feature of this embodiment.

  The formation of the recording mark 9 due to a local change in optical characteristics in the recording layer 3-2 is based on the conventional plastic deformation temperature of the transparent substrate 2-2, the thermal decomposition temperature in the recording layer 3-2, and the vaporization (evaporation) temperature. However, since it occurs at a much lower temperature, the transparent substrate 2-2 does not locally exceed the plastic deformation temperature during recording or does not exceed the thermal decomposition temperature or vaporization (evaporation) temperature locally in the recording layer 3-2. Limit the upper limit of recording power.

In parallel with the examination by thermal analysis, the apparatus described later in “4-1) Description of structure and characteristics of reproducing apparatus or recording / reproducing apparatus in this embodiment” is used, and “4-3) Recording conditions in this embodiment are determined. The value of the optimum power when recording was performed according to the recording principle shown in the present embodiment using the recording conditions described later in “Description” was also demonstrated. The objective lens NA (Numerical Apperture) value in the recording / reproducing apparatus used in the demonstration experiment was 0.65, and the linear velocity during recording was 6.61 m / s. The value of recording power (Peak Power) defined later in “4-3) Description of recording conditions in this embodiment” is vaporized (evaporated) in most organic dye recording materials at 30 mW, and cavities are formed in the recording marks. The temperature of the transparent substrate 2-2 near the recording layer 3-2 greatly exceeds the glass transition temperature. The temperature of the transparent substrate 2-2 near the recording layer 3-2 at 20 mW is the plastic deformation temperature. (Glass transition temperature) reached ◎ It was found that 15 mW or less is desirable in anticipation of margins such as surface wobbling / warping of the information storage medium and fluctuations in recording power.

The “recording power” described above means the sum of the exposure amount irradiated to the recording layer 3-2. The light energy density in the central portion of the focused spot where the light intensity density is the highest is a parameter to be studied in the present embodiment. Since the focused spot size is inversely proportional to the NA value, the light energy density at the center of the focused spot increases in proportion to the square of the NA value. Therefore,
[Recording power adaptable to different NAs]
= [Recording power at NA = 0.65] × 0.652 / NA2 (5)
Can be converted into an optimum recording power value in the B format described later or another format (different NA value) shown in Table 1 (D3).

Furthermore, the optimum recording power varies depending on the linear velocity V during recording. In general, it is said that the optimum recording power changes in proportion to the 1/2 power of the linear velocity V in the phase change recording material, and changes in proportion to the linear velocity V in the organic dye recording material. Therefore, the optimum recording power conversion formula taking into account the linear velocity V is an extension of formula (5) [General recording power]
= [NA = 0.65; Recording power at 6.6 m / s]
× (0.65 / NA) 2 × (V / 6.6) (6)
Or [General recording power]
= [NA = 0.65; Recording power at 6.6 m / s]
× (0.65 / NA) 2 × (V / 6.6) 1/2 (7)
It is obtained by. Summarizing the above examination results, as the recording power for guaranteeing the recording principle shown in this embodiment, [Optimum recording power]
<30 × (0.65 / NA) 2 × (V / 6.6) (8)
[Optimal recording power]
<30 × (0.65 / NA) 2 × (V / 6.6) 1/2 (9)
[Optimal recording power]
<20 × (0.65 / NA) 2 × (V / 6.6) (10)
[Optimal recording power]
<20 × (0.65 / NA) 2 × (V / 6.6) 1/2 (11)
[Optimal recording power]
<15 × (0.65 / NA) 2 × (V / 6.6) (12)
[Optimal recording power]
<15 × (0.65 / NA) 2 × (V / 6.6) 1/2 (13)
It is desirable to set an upper limit value. Among the above formulas, the condition of formula (8) or formula (9) is an indispensable condition, formula (10) or formula (11) is a target condition, and formula (12) or formula (13) is a desirable condition.

3-4) Description of Features Regarding “H → L” Recording Film in the Present Embodiment A recording film having a characteristic that the light reflection amount in the recording mark 9 is lower than the light reflection amount in the unrecorded area is referred to as “H → L”. The recording film called “recording film” and conversely, the recording film that rises is called “L → H” recording film. Among them, the “H → L” recording film (1) An upper limit is set for the ratio of the absorbance at the reproduction wavelength to the absorbance at the λ _{max write} position of the light absorption spectrum. (2) Recording is performed by changing the light absorption spectrum profile. The major feature of this embodiment is that the mark is formed.

  A detailed description of the above contents will be given with reference to FIG. In the H → L recording film in this embodiment, as shown in FIG. 32, the wavelength of λmax write is shorter than the used wavelength (near 405 nm) used for recording / reproduction. As can be seen from the chemical formula 14, there is little change in absorbance between unrecorded and recorded in the vicinity of the wavelength of λmax write. If there is little change in absorbance between unrecorded and recorded, the reproduction signal amplitude cannot be increased. In view of the fact that stable recording or reproduction can be performed even if the wavelength of the recording or reproducing laser light source changes, in this embodiment, the wavelength of λmax write is outside the range of 355 nm to 455 nm as shown in FIG. That is, the recording film 3-2 is designed so as to be on the shorter wavelength side than 355 nm. FIG. 33 is an explanatory diagram of light absorption spectrum characteristics in the recording mark in the “H → L” recording film.

"Chapter 0 Use" when the absorbance at the λmax write position defined as "2-1) Difference in recording principle / difference in recording film structure and fundamental difference in reproduction signal generation" has been normalized to "1" The relative absorbance at 355 nm, 455 nm, and 405 nm described in “Relationship Between Wavelength and This Embodiment” is defined as Ah ₃₅₅ , Ah ₄₅₅ , and Ah ₄₀₅ .

When Ah ₄₀₅ = 0.0, the light reflectance from the recording film in the unrecorded state matches the light reflectance at 405 nm in the light reflecting layer 4-2. The light reflectance of the light reflecting layer 4-2 will be described later in detail in “6-1) Light reflecting layer”, but here the light reflectance of the light reflecting layer 4-2 is changed for the sake of simplicity of explanation. The explanation will be made assuming 100%.

In the write-once information storage medium using the “H → L” recording film in the present embodiment, the reproduction circuit is made common to the case of using a read-only information storage medium (HD DVD-ROM disc) in the case of a single-layer film on one side. ing. Therefore, the light reflectivity in this case is set to 40 to 85% in accordance with the light reflectivity of the read-only information storage medium (HD DVD-ROM disc) having a single-sided single layer film. For this purpose, it is necessary to set the light reflectance at an unrecorded position to 40% or more. Since 1−0.4 = 0.6, the absorbance Ah _{405 at 405} nm is Ah ₄₀₅ ≦ 0.6 (14)
I can intuitively understand what should be done. When the above formula (14) is satisfied, it can be easily understood that the light reflectance at the unrecorded position can be 40% or more. Therefore, in this embodiment, the organic dye satisfying the formula (14) at the unrecorded location. Recording materials are selected. The above equation (14) assumes that the light reflectivity is 0% when the light reflection layer 4-2 is reflected through the recording layer 3-2 with the light having the wavelength of λ _{max write} in FIG. However, in actuality, the light reflectivity at this time does not become 0% but has a certain degree of light reflectivity, and strictly, correction to the equation (14) is necessary. In FIG. 32, when the light reflectance when the light reflecting layer 4-2 is reflected through the recording layer 3-2 with the light having the wavelength of λ _{max write} is defined as Rλ _{max write} , the light reflectance at the unrecorded position is 40. The strict conditional expression set to% or more is 1-Ah ₄₀₅ × (1-Rλ _{max write} ) ≧ 0.4 (15)
It becomes. In the case of “H → L” recording film, Rλ _{max write} ≧ 0.25 in many cases, so equation (15) is Ah ₄₀₅ ≦ 0.8 (16)
It becomes. In the “H → L” recording film of the present embodiment, it is essential to satisfy the expression (16). Detailed optical film design was performed on condition that the characteristics of the above expression (14) were given and the condition of the expression (3) or (4) was satisfied as the film thickness of the recording layer 3-2. As a result, taking into account various margins such as film thickness fluctuation and wavelength fluctuation of reproduction light, Ah ₄₀₅ ≦ 0.3 (17)
Is desirable. Assuming equation (14),
Ah ₄₅₅ ≦ 0.6 (18)
Or Ah ₃₅₅ ≦ 0.6 (19)
When set to, the recording / reproducing characteristics are further stabilized. This is because when the formula (14) is satisfied and at least one of the formulas (18) and (19) is satisfied, the range is 355 nm to 405 nm, or the range 405 nm to 455 nm (sometimes 355 nm to 455 nm). This is because the value of Ah becomes 0.6 or less (within this range), so that even if the emission wavelength of the recording laser light source (or reproducing laser light source) varies, the absorbance value does not change greatly.

The specific recording principle of the “H → L” recording film in this embodiment is “α” in “3-2-B] Basic features common to organic dye recording materials in this embodiment” already described. Among the listed recording mechanisms, the phenomenon of “change in arrangement between molecules” or “change in molecular structure within the molecule” is used. As a result, the light absorption spectrum profile is changed as described in (2) above. The light absorption spectrum profile in the recording mark in the present embodiment is indicated by a solid line in the formula 14, and the light absorption spectrum profile at an unrecorded place is overlapped by a broken line so that both can be compared. In the present embodiment, the light absorption spectrum profile in the recording mark changes relatively broadly, causing a change in the molecular structure inside the molecule, possibly causing the precipitation of carbon atoms (coal tarization). By reproducing the wavelength λlmax at which the absorbance within the recording mark is maximized closer to the reproduction wavelength 405 nm than the value of the wavelength λmax write at the unrecorded position, a reproduction signal is generated on the “H → L” recording film. There is a feature of this embodiment. Thereby, the absorbance at the wavelength λlmax where the absorbance is highest is smaller than “1”, and the value of the absorbance Al _{405 at} the reproduction wavelength 405 nm is larger than the value of Ah ₄₀₅ . As a result, the total light reflectance in the recording mark is lowered.

In the H format in the present embodiment, ETM (Eight to Twelve: 8-bit data code is converted into 12 channel bits), RLL (1, 10) (corresponding to the channel bit length T in the modulated code string) The minimum inversion length is 2T and the maximum inversion length is 11T). The performance of the reproduction circuit described later in “4-2) Description of the reproduction circuit in this embodiment” was evaluated. In order to reproduce stably with the reproduction circuit [unrecorded with a sufficiently long length (11T)] The difference value I ₁₁ ≡I ₁₁ H−I ₁₁ between [the I ₁₁ H and the reproduction signal amount I ₁₁ L from the recording mark having a sufficiently long length (11T) with respect to the reproduction signal amount I ₁₁ H from the area] L] is at least the ratio of I ₁₁ / I ₁₁ H ≧ 0.4 (20)
Desirably I ₁₁ / I ₁₁ H> 0.2 (21)
It was found that it was necessary to satisfy. In the present embodiment, the PRML method is used when reproducing a signal recorded at a high density. In order to detect accurately with the PRML method, the linearity of the reproduction signal is required. The ratio for the I ₁₁ of the value when the amplitude of the reproduced signal from the repetition signal of the recording mark and the unrecorded spaces having a length of 3T and I3 in order to ensure linearity of the reproduction signal (linearity) I ₃ / I ₁₁ ≧ 0.35 (22)
Desirably I ₃ / I ₁₁ > 0.2 (23)
It was also found that there is a need to satisfy. The technical feature of the present embodiment is that the value of Al ₄₀₅ is set so as to satisfy the expressions (20) and (21) while considering the condition of the above expression (16). Refer to the equation (16) 1-0.3 = 0.7 (24)
It becomes. Taking the equation (24) into view, from the correspondence with the equation (20), (Al ₄₀₅ -0.3) /0.7≧0.4
Al ₄₀₅ ≧ 0.58 (25)
The conditions are derived. The formula (25) is a formula derived from a very rough examination result and merely shows a basic idea. Since the setting range of Ah ₄₀₅ are defined in (16), in this embodiment at least Al _405> 0.3 As a condition of _{Al 405} (26)
Is essential.

As a method of selecting an organic dye material suitable for a specific “H → L” recording film, in this embodiment, the refractive index range in an unrecorded state is n ₃₂ = 1.3-2. 0, an absorption coefficient range of k ₃₂ = 0.1 to 0.2, preferably n ₃₂ = 1.7 to 1.9, an absorption coefficient range of k32 = 0.15 to 0.17 is selected. The above-described series of conditions are satisfied.

In the “H → L” recording film shown in FIG. 32 or 14, the wavelength of λ _{max write} is shorter than the wavelength of reproduction light or recording / reproduction light (for example, 405 nm) in the light absorption spectrum in the unrecorded area. However, the present invention is not limited to this. For example, the wavelength of λ _{max write} may be longer than the wavelength of reproduction light or recording / reproduction light (for example, 405 nm).

In order to satisfy the formula (22) or the formula (23), the thickness Dg of the recording layer 3-2 greatly affects. For example, when the thickness Dg of the recording layer 3-2 greatly exceeds the allowable value, only a part of the optical characteristics in contact with the transparent substrate 2-2 in the recording layer 3-2 changes as the state after the recording mark 9 is formed. As a result, the optical characteristics of the portion in contact with the light reflecting layer 4-2 adjacent to the location remain the same as those of other unrecorded areas. As a result, the change in the amount of reproduced light is reduced, the value of I3 in the expression (22) or (23) is decreased, and the condition of the expression (22) or (23) cannot be satisfied. Therefore, in order to satisfy the expression (22), it is necessary to change the optical characteristics of the portion in contact with the light reflection layer 4-2 in the recording mark 9 as shown in FIGS. 31 (b) and 31 (c). Further, if the thickness Dg of the recording layer 3-2 greatly exceeds the allowable value, a temperature gradient is generated in the thickness direction in the recording layer 3-2 at the time of recording mark formation, and the light reflecting layer 4- in the recording layer 3-2. Before reaching the optical property change temperature at the portion in contact with 2, the vaporization (evaporation) temperature of the portion in contact with the transparent substrate 2-2 is exceeded, or the thermal deformation temperature is exceeded in the transparent substrate 2-2. For this reason, in the present embodiment, the thickness Dg of the recording layer 3-2 is set to “3T” or less in order to satisfy the equation (22) by thermal analysis, and the condition of the recording layer 3-2 is satisfied as a condition to satisfy the equation (23). The thickness Dg is set to “3 × 3T” or less. Basically, when the thickness Dg of the recording layer 3-2 is "3T" or less, the equation (22) can be satisfied. However, the influence of tilt and defocusing caused by surface wobbling / warping of the write-once information storage medium can be satisfied. Considering the margin for, there may be a case where it is set to “T” or less. Considering the results of the expressions (1) and (2) already described, the range of the thickness Dg of the recording layer 3-2 in the present embodiment is 9T ≧ Dg ≧ λ / 8n ₃₂ (27) as a necessary minimum condition.
Desirable conditions are 3T ≧ Dg ≧ λ / 4n ₃₂ (28)
The thickness Dg of the recording layer 3-2 is set within the range given by. However, the strictest conditions are not limited to T ≧ Dg ≧ λ / 4n ₃₂ (29)
It is also possible to. As will be described later, the channel bit length T is 102 nm for the H format and 69 nm to 80 nm for the B format. Therefore, the 3T value is 306 nm for the H format, 207 nm to 240 nm for the B format, and the 9T value is the H format. Is 918 nm and B format is 621 nm to 720 nm. Here, the “H → L” recording film has been described, but the conditions of the equations (27) to (29) are not limited thereto, and can be applied to the “L → H” recording film.

Specific Description of Organic Dye Recording Film in this Embodiment 5-1) Characteristic Description Regarding “L → H” Recording Film in this Embodiment The L → H ″ recording film will be described. The recording principle when this recording film is used is mainly the recording principle described in “3-2-B] Basic features common to the organic dye recording material in this embodiment”. Changes in the electronic structure (electron orbital) for electrons contributing to the phenomenon (decolorization, etc.)
• Change the characteristics of the absorption spectrum using any of the intermolecular alignment changes. Regarding the “L → H” recording film, there is a great feature in that the reflection amount range at the unrecorded location and the recorded location is specified taking into consideration the characteristics of a read-only information storage medium having a single-sided two-layer structure. Yes. In this embodiment, it is defined that the reflectance lower limit value δ in the non-recording portion of the “H → L” recording film is higher than the upper limit value γ in the non-recording portion of the “L → H” recording film. When the information recording / reproducing apparatus or the information recording medium is mounted on the information reproducing apparatus, the light reflectance of the non-recording part is measured by the slice level detecting unit 132 or the PR equalizing circuit 130, and the “H → L” recording film is instantaneously measured. Since “L → H” recording film can be discriminated, the type of recording film can be discriminated very easily. As a result of measuring the “H → L” recording film and the “L → H” recording film prepared by changing many manufacturing conditions, the reflectance lower limit value δ at the non-recording portion of the “H → L” recording film was measured. When the light reflectance α between the upper limit value γ and the upper limit value γ in the non-recording portion of the “L → H” recording film is within the range of 32% to 40%, the recording film is highly manufacturable and the medium price is reduced. I found it easy. The light reflectance range 801 of the “L → H” recording film non-recording portion (“L” portion) is matched with the light reflectance range 803 of the single-sided two-recording layer in the read-only information storage medium, and “H → L” recording is performed. If the light reflectance range 802 of the non-recording portion (“H” portion) of the film is matched with the single-layer single-layer light reflectance range 804 in the read-only information storage medium, compatibility with the read-only information storage medium is achieved. Since the reproduction circuit of the information reproducing apparatus can be commonly used, the information reproducing apparatus can be made at low cost. As a result of creating and measuring “H → L” recording films and “L → H” recording films prepared by changing many manufacturing conditions, in order to increase the productivity of the recording films and facilitate the cost reduction of the medium In the present embodiment, the lower limit value β of the light reflectance of the non-recording portion (“L” portion) of the “L → H” recording film is 18% and the upper limit value γ is 32%. The light reflectance lower limit value δ of the non-recording portion (“H” portion) was set to 40% and the upper limit value ε was set to 85%.

  When the H format is adopted, an embossed area (system lead-in area SYLDI, etc.) and a recording mark area (data) are defined on the “L → H” recording film on the basis of the groove level by defining the light reflectance range in the non-recording part. A signal appears in the same direction in the lead-in area DTLDI, the data lead-out area DTLDO, and the data area DTA). Similarly, in the “H → L” recording film, the embossed area (system lead-in area SYLDI, etc.) and the recording mark area (data lead-in area DTLDI, data lead-out area DTLDO, data area DTA) are reversed in the reverse direction with the groove level as a reference. A signal appears. Using this phenomenon, not only can it be used for recording film identification between “L → H” recording film and “H → L” recording film, but also supports “L → H” recording film and “H → L” recording film. It is easy to design the detection circuit. In addition, the reproduction signal characteristics obtained from the recording marks recorded on the “L → H” recording film shown in the present embodiment are matched with the signal characteristics obtained from the “H → L” recording film, the expressions (20) to (23) ) Is satisfied. As a result, the same signal processing circuit can be used when using either the “L → H” recording film or the “H → L” recording film, and the signal processing circuit can be simplified and reduced in price.

5-2) Characteristics of Optical Absorption Spectra Regarding “L → H” Recording Film of this Embodiment “3 → 4” Characteristics of “H → L” Recording Film ”“ H → L ” “In the recording film, the relative absorbance in the unrecorded area is basically low, so that when the reproducing light is irradiated during reproduction, the optical characteristic change caused by absorbing the energy of the reproducing light hardly occurs. Even if a change in optical characteristics (update of recording action) occurs due to absorption of the energy of the reproduction light in the recording mark having a high absorbance, the light reflectance from the recording mark is decreasing, so the amplitude of the reproduction signal (I ₁₁ ≡I ₁₁ H-I ₁₁ L) increases, and there is little adverse effect on the reproduction signal processing.

  In contrast, the “L → H” recording film has an optical characteristic that “the light reflectance of the unrecorded portion is lower than that in the recording mark”. This means that the absorbance of the unrecorded portion is higher than that in the recorded mark, as can be seen from the contents described with reference to FIG. Therefore, the “L → H” recording film is more susceptible to signal degradation during reproduction than the “H → L” recording film. As described in “3-2-B] Basic features common to organic dye recording materials in the present embodiment”, “ε” is prepared in the event that reproduction signal deterioration occurs due to irradiation with ultraviolet rays or reproduction light. There is a need to improve the reliability of playback information.

As a result of examining the characteristics of organic dye recording materials in detail, it was found that the mechanism that changes the optical characteristics by absorbing the energy of the reproduction light is almost similar to the mechanism that changes the optical characteristics by ultraviolet irradiation. As a result, if a structure for improving the durability against ultraviolet irradiation in an unrecorded area is provided, signal deterioration during reproduction hardly occurs. Therefore, in the “L → H” recording film, the value of λ _{max write} (maximum absorption wavelength closest to the wavelength of the recording light) is longer than the wavelength of the recording light or reproduction light (near 405 nm). There are features. Thereby, the absorptance with respect to an ultraviolet-ray can be made low and the durability with respect to ultraviolet irradiation can be improved significantly. As can be seen from Figure 35, lambda _{max write} a difference in absorbance is small between the recorded portion and an unrecorded portion in the vicinity, the reproduction signal modulation degree in the case of reproduction with a light beam having a wavelength in the vicinity of lambda _{max write} (signal amplitude) Get smaller. Taking into account the wavelength variation of the semiconductor laser light source, it is desirable that a sufficiently large reproduction signal modulation degree (signal amplitude) can be obtained in the range of 355 nm to 455 nm. Therefore, in the present embodiment, the recording film 3-2 is designed so that the wavelength of λ _{max write} is outside the range of 355 nm to 455 nm (that is, longer wavelength side than 455 nm).

An example of the light absorption spectrum in the “L → H” recording film in this embodiment is shown in FIG. As described in “5-1) Characteristic description regarding“ L → H ”recording film” in this embodiment, in this embodiment, the light reflection of the non-recording portion (“L” portion) of the “L → H” recording film is described. The lower limit value β of the rate is set to 18%, and the upper limit value γ is set to 32%. In order to satisfy the above condition from 1-0.32 = 0.68, the absorbance value Al ₄₀₅ in the unrecorded area at 405 nm is Al ₄₀₅ ≧ 68% (36)
You can intuitively understand that you should be satisfied. Although the light reflectance at 405 nm of the light reflecting layer 4-2 in FIG. 26 is slightly lower than 100%, it is assumed that it is close to 100% for the sake of simplicity of explanation. Therefore, the light reflectance when the absorbance Al = 0 is almost 100%. The light reflection factor of the whole recording film at a wavelength of lambda _{max write} in Fig. 34 expressed by R [lambda] _{max write.} The expression (36) is derived on the assumption that the light reflectance at this time is zero (Rλ _{max write} ≈0). However, since it is not actually “0”, it is necessary to derive a more strict expression. The strict conditional expression for setting the upper limit value γ of the light reflectance of the non-recording portion (“L” portion) of the “L → H” recording film to 32% is 1−Al ₄₀₅ × (1−Rλ _{max write} ) ≦ 0 .32 (37)
Given in. All conventional write-once information storage media use “H → L” recording film, and there is no accumulation of information regarding “L → H” recording film, but “5-3) anion portion: azo metal complex + cation. Part: Dye ”and“ 5-4) Azo metal complex + “Use copper” as the central metal. When this embodiment described later is used, the most severe condition satisfying the expression (37) is Al ₄₀₅ ≧ 80% ( 38)
It becomes. When the organic dye recording material described later in the above embodiment is used, if the recording film is optically designed including margins such as variations in characteristics during manufacturing and changes in the thickness of the recording layer 3-2, "5-1) Al ₄₀₅ ≧ 40% (39) is the minimum condition for satisfying the reflectance described in “Characteristics regarding“ L → H ”recording film” in this embodiment ”.
I understood that I should be satisfied. Furthermore, Al ₃₅₅ ≧ 40% (40)
Al455 ≧ 40% (41)
Is satisfied even if the wavelength of the light source is changed in the range of 355 nm to 405 nm or the range of 405 nm to 455 nm (the range of 355 nm to 455 nm when both equations are satisfied simultaneously). Reproduction characteristics can be secured.

FIG. 35 shows a change state of the light absorption spectrum after recording in the “L → H” recording film of the present embodiment. The value of the maximum absorption wavelength λl _{max in} the recording mark is deviated from the wavelength of λ _{max write} , and it is considered that an intermolecular molecular change (for example, an array change between azo metal complexes) occurs. Furthermore, the decolorization effect (local electron orbital breakage) occurs in parallel with the decrease in both the absorbance at λl _max and the absorbance at 405 nm, Al ₄₀₅ and the spread of the light absorption spectrum itself. (Local molecular bond dissociation)) is considered to have occurred.

Also in the “L → H” recording film of the present embodiment, the “L → H” recording film and the “H → L” recording are satisfied by satisfying the equations (20), (21), (22), and (23). The same signal processing circuit can be used for both membranes to simplify the signal processing circuit and reduce the price. In the equation (20), I ₁₁ / I ₁₁ H≡ (I ₁₁ H-I ₁₁ L) / I ₁₁ H ≧ 0.4 (42)
I ₁₁ H ≧ / I ₁₁ L / 0.6 (43)
It becomes. As described above, in this embodiment, the lower limit value β of the light reflectance of the unrecorded portion (“L” portion) of the “L → H” recording film is set to 18%, and this value becomes I ₁₁ L. Correspond. Furthermore, conceptually, I ₁₁ H≈1-Ah ₄₀₅ × (1-Rλ _{max write} ) (44)
Therefore, from the equations (43) and (44), 1-Ah ₄₀₅ × (1-Rλ _{max write} ) ≧ 0.18 / 0.6 (45)
It becomes. When 1−Rλ _{max write} ≈0, the expression (45) is Ah ₄₀₅ ≦ 0.7 (46)
It is obtained by. Comparing the above formulas (46) and (36), it can be seen that it would be good if the values of Al ₄₀₅ and Ah ₄₀₅ are set as the absorbance values around 68% to 70%. _Furthermore, in the case where the range as the value of formula (39) of the _{Al 405,} given the performance stability of a signal processing circuit, Ah ₄₀₅ ≦ 0.4 as severe condition (47)
There is. If possible, Ah ₄₀₅ ≦ 0.3 (48)
It is desirable to satisfy

5-3) Anion part: azo metal complex + cation part: Dye “5-1) Features described in“ Characteristics of “L → H” recording film ”in this embodiment”, “5-2) This implementation The organic dye material according to the present embodiment, which satisfies the conditions indicated by the “characteristics of the light absorption spectrum related to the“ L → H ”recording film” in the embodiment, will be described. The thickness of the recording layer 3-2 satisfies the conditions indicated by the equations (3), (4), (27), and (28), and is formed by spinner coating (spin coating). As an example for comparison, "salt" crystals are assembled with "ionic bonds" between positively charged "sodium ions" and negatively charged "chlorine ions". Similarly, in the case of polymers, organic dye materials may be formed by combining a plurality of different polymers close to “ionic bonds”. The organic dye recording film 3-2 in the present embodiment is composed of a “cation part” that is charged on the plus side and an “anion part” that is charged on the minus side. In particular, the “cation part” charged on the positive side uses a “dye” that has coloring properties, and the counter ion part is used and the “anion part” that is negatively charged uses an organometallic complex to stabilize the bond. To stabilize the electronic structure in the “δ” coloring region shown in “3-2-B] Basic features common to the organic dye recording material in the present embodiment” There is a major technical feature in satisfying the condition of “structural decomposition is difficult to occur”. Specifically, in this embodiment, an “azo metal complex” having a general structural formula shown in Chemical Formula 1 is used as an organometallic complex. In this embodiment comprising a combination of an anion portion and a cation portion, cobalt or nickel is used as the central metal M of this azo metal complex to improve the light stability, but not limited to scandium, yttrium, titanium, zirconium, hafnium. , Vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, rhodium, iridium, palladium, platinum, copper, silver, gold, zinc, cadmium, mercury, etc. may be used. . In the present embodiment, any one of a cyanine dye, a styryl dye, and a monomethine cyanine dye having a general structural formula shown in Chemical Formula 3 is used as a dye used in the cation moiety. In the present embodiment, an azo metal complex is used for the anion portion. However, for example, a formazan metal complex may be used. The organic dye recording material comprising the anion portion and the cation portion is initially powdered. In the case of forming the recording layer 3-2, this powdery organic dye recording material is dissolved in an organic solvent, and then spin coating is performed on the transparent substrate 2-2. Examples of organic solvents used at this time include hydrocarbons such as fluoroalcohol-based TFP (tetrafluoropropanol), pentane, hexane, cyclohexane, petroleum ether, petroleum benzine, alcohols, phenols, ethers, nitriles, nitro Either a compound or a sulfur-containing compound or a combination thereof is used.

5-4) Use of “copper” as the azo metal complex + central metal Recording on the “H → L” recording film and the “L → H” recording film using the optical characteristic change of this embodiment as a recording principle (record mark formation) An example of the change in the light absorption spectrum before and after is shown in FIGS. The λ _{max write} wavelength before recording (within the unrecorded area) is λb _{max write} , and the half width of the light absorption spectrum (b) centered on this λb _{max write} (absorbance A at λb _{max write} is set to “1”) The width of the wavelength region satisfying the range of “A ≧ 0.5” at the time) is defined as Was, and the λ _{max write} wavelength of the light absorption spectrum (a) after recording (within the recording mark) is defined as λa _{max write} . The recording film 3-2 having the characteristics shown in FIGS. 36 and 37 is the same as the recording principle shown in [α] in “3-2-B] Basic features common to organic dye recording materials in this embodiment”. , "Changes in the electronic structure (electron orbitals) for electrons contributing to the coloring phenomenon" and "Molecular structure changes in the molecule" are used. When “change in the electronic structure (electron orbit) with respect to electrons contributing to the coloring phenomenon” occurs, for example, the size and structure of the coloring area 8 as shown in Chemical Formula 1 change. For example, when the dimension of the light emitting region 8 changes, the resonance absorption wavelength of the localized electrons changes, so that the maximum (maximum) absorption wavelength of the light absorption spectrum changes from λb _{max write} to λa _{max write} . Similarly, when a “molecular structure change within the molecule” occurs, the structure of the color development region 8 also changes, and similarly, the maximum (maximum) absorption wavelength of the light absorption spectrum changes. Here maxima (maximum) amount of change in absorption wavelength is defined as [Delta] [lambda] _max when _{Δλ max ≡ | λ amax write -λb} max write | (49)
The relationship holds. Thus, when the maximum (maximum) absorption wavelength of the light absorption spectrum changes, the half-value width Was of the light absorption spectrum also changes accordingly. The influence on the reproduction signal obtained from the recording mark position when the maximum (maximum) absorption wavelength of the light absorption spectrum and the half-value width Was of the light absorption spectrum simultaneously change will be described. In FIG. 36 (FIG. 37), since the light absorption spectrum in the pre-recording / unrecorded area is given by (b), the absorbance at 405 nm reproduction light is Ah ₄₀₅ (Al ₄₀₅ ). If only the maximum (maximum) absorption wavelength of the optical spectrum after recording (inside the recording mark) changes to λa _{max write,} and there is no change in the half-value width Was, the optical absorption spectrum is as shown in FIG. As shown in c), the absorbance at 405 nm reproduction light changes to A ^* _405. However, since the half-value width actually changes, the absorbance after recording (within the recording mark) becomes Al ₄₀₅ (Ah ₄₀₅ ). End up. Since the amount of change in absorbance | Al ₄₀₅ -Ah ₄₀₅ | before and after recording is proportional to the amplitude of the reproduced signal, in the example shown in FIG. 36 (FIG. 37), the maximum (maximum) absorption wavelength change and the half-value width change are the reproduced signal. Since it cancels out the increase in amplitude, there arises a problem that the C / N ratio of the reproduction signal is deteriorated. As a first application example of this embodiment for solving the problem, the characteristics of the recording layer 3-2 are set so that the maximum (maximum) absorption wavelength change and the half-value width change work synergistically with the increase in the reproduction signal amplitude. There is a big feature in the setting (film design). That is, as can be easily predicted from the change in FIG. 36 (FIG. 37), the half-value width of the “H → L” recording film expands regardless of the moving direction of λa _{max write} after recording with respect to λb _{max write} before recording. ,
In the “L → H” recording film, the characteristics of the recording layer 3-2 are set so that the half-value width changes in a direction that becomes narrower regardless of the moving direction of the λ _{amax write} after recording with respect to the λb _{max write} before recording (film design). )

Next, a second application example in the present embodiment will be described. As described above, there is a case where the C / N ratio of the reproduction signal is lowered by offsetting the opening between Ah ₄₀₅ and Al ₄₀₅ by the change in the maximum (maximum) absorption wavelength and the change in half-value width Was. Furthermore, in the first application example and the embodiment shown in FIG. 36 or FIG. 37, the maximum (maximum) absorption wavelength change and the half-value width Was of the light absorption spectrum change simultaneously, so after recording (within the recording mark). The value of absorbance A is affected by both the maximum (maximum) absorption wavelength variation Δλ _max and the half-value width variation. When the write-once information storage medium 12 is mass-produced, it is difficult to control both the maximum (maximum) absorption wavelength variation Δλ _max and the half-value width variation at the same time with high accuracy. The variation in the amplitude of the reproduction signal when information is recorded increases, and the reliability of the reproduction signal when reproduced by the information reproduction apparatus decreases. In contrast, the material of the recording layer 3-2 shown in the second application example in the present embodiment is devised so that the maximum (maximum) absorption wavelength before and after recording (in the recording mark and in the unrecorded area) does not change. There is a great feature in that the reliability of the reproduction signal is improved by suppressing the variation in the value of the absorbance A after recording (within the recording mark) and reducing the inter-individual variation in the reproduction signal amplitude therefrom. In this second application example, since the maximum (maximum) absorption wavelength before and after recording (in the recorded mark and in the unrecorded area) does not change, the value of the absorbance A is the light before and after recording (in the recorded mark and in the unrecorded area). It is determined only by the spread of the absorption spectrum. When a large number of write-once information storage media 12 are mass-produced, it is only necessary to control the spread of the light absorption spectrum before and after recording (in the recorded mark and in the unrecorded area), so that variations in characteristics between the media can be reduced. Even if it is devised so that the maximum (maximum) absorption wavelength before and after recording (in the recorded mark and in the unrecorded area) does not change, strictly, the values of λb _{max write} and λa _{max write} are completely set as shown in FIG. It is difficult to match perfectly. The full width at half maximum Was of the light absorption spectrum centering on λb _{max write} shown in FIGS. 36 and 37 is often in the range of 100 nm to 200 nm in a general organic dye recording material. Therefore, when the value of the maximum (maximum) absorption wavelength variation Δλmax exceeds 100 nm, the absorbance Ah ₄₀₅ (Al ₄₀₅ ) obtained from the characteristics (b) and the absorbance A * ₄₀₅ obtained from the characteristics (c) are obtained. It can be easily predicted from FIGS. 36 and 37 that a large opening occurs. Therefore, as a second application example, the meaning of “the maximum (maximum) absorption wavelength does not change” means Δλmax ≦ 100 nm (50)
It means satisfying the conditions. Furthermore, the maximum (maximum) absorption wavelength variation Δλmax is 1/3 of the equation (50).
Δλmax ≦ 30nm (51)
The difference between the absorbance Ah ₄₀₅ (Al ₄₀₅ ) obtained from the characteristics of (b) and the absorbance A * ₄₀₅ obtained from the characteristics of (c) becomes very small under the conditions of (b). The variation in signal characteristics can be reduced.

FIG. 38 shows “L → H” recording film characteristics satisfying the formula (50) or the formula (51). The light absorption spectrum before recording (in an unrecorded area) is a broad spectrum as shown in the characteristic (b) of FIG. 38, and the absorbance Ah ₄₀₅ at a reproduction wavelength of 405 nm is a sufficiently small value. . The optical absorption spectrum after recording (within the recording mark) becomes narrow as shown in the characteristic (a) of FIG. 38, and the absorbance Al ₄₀₅ at the reproduction wavelength of 405 nm increases.

In order to satisfy the formula (50) or the formula (51), in the present embodiment, “3-2-B” in “α” of “Basic features common to the organic dye recording material in the present embodiment” is used as the recording principle. “Change in orientation within the molecule” is utilized. The specific contents of this embodiment (second applied example) will be described below. In the azo metal complex shown in Chemical Formula 1, since the benzene nucleus ring is radically bonded, a plurality of benzene nucleus rings are arranged on the same plane. That is, the four benzene nucleus rings above the central metal M in the chemical formula 1 form a U (up side) plane formed by the benzene nucleus group, and the four benzene nucleus rings below the central metal M. Forms the D (down side) plane created by the benzene nucleus group. In any case (regardless of before and after recording), the U plane and the D plane always maintain a parallel relationship. The side chain groups of R1 and R3 are arranged so as to be orthogonal to the U plane and the D plane. The central metal atom M and the oxygen atom O (solid line portion) are connected by an ionic bond, and the plane formed by the line connecting O-MO is arranged in parallel to the U plane and the D plane. . The coloring area 8 surrounded by the round area of Chemical Formula 1 has such a three-dimensional structure. For future explanation, the direction from the R4 direction to the R5 direction in the U plane is provisionally defined as “Yu direction”, and the direction from the R4 direction to the R5 direction in the D plane is provisionally defined. It is defined as “Yd direction”. The nitrogen atom N included in the U plane or D plane and the central metal atom M sandwiched between the two surfaces (broken line portion) are connected by a coordinate bond, and nitrogen centered on the central metal atom M The position of atom N is rotatable. In other words, the Y plane can be rotated with respect to the Yu direction while maintaining a parallel relationship between the U plane and the D plane. In the azo metal complex shown in Chemical Formula 1, the Yu direction and the Yd direction are parallel to each other as shown in Chemical Formula 2 (a) (the directions can be opposite or the same as in Chemical Formula 2 (a)). As shown in chemical formula 2 (b), the Yu direction and the Yd direction are twisted. Naturally, it is also an arbitrary angular relationship between the chemical formula 2 (a) and the chemical formula 2 (b). As described above, since the side chain groups of R1 and R3 shown in Chemical formula 1 are arranged in a form orthogonal to the U plane and the D plane, in the structure of Chemical formula 2 (a), the upper and lower R1 or R3 Collisions easily occur between side chain groups or other side chain groups such as R4. Therefore, when the Yu direction and the Yd direction are twisted with each other as shown in chemical formula 2 (b) (when viewed from the upper side of the U plane, the Yu direction and the Yd direction appear to be orthogonal to each other). Is the most structurally stable. The light absorption wavelength in the coloring region 8 in the state of chemical formula 2 (b) coincides with the value of λa _{max write} = λbl in FIG. When the relationship between the Yu direction and the Yd direction deviates from the state of Chemical Formula 2 (b), the electronic structure in the color development region 8 and the localized distance of the light absorbing electrons (the size of the localized region) change slightly, and the light absorption wavelength Deviates from the value of λa _{max write} = λb _{max write} . The relationship between the Yu direction and the Yd direction is arbitrarily oriented in the recording layer 3-2 immediately after being formed on the transparent substrate 2-2 by spinner coating (unrecorded state). Therefore, the distribution width of the light absorption spectrum is wide as shown in the characteristic (b) of FIG. When the temperature in the recording layer 3-2 is locally increased to form a recording mark, the molecular orientation starts to move due to the high temperature, and finally, the state is almost completely structurally stabilized (b). Then, the electronic structure in the coloring region 8 is consistent everywhere in the recording mark, and changes to a light absorption spectrum having a narrow distribution width as shown in the characteristic (a) of FIG. As a result, the absorbance at the reproduction wavelength (for example, 405 nm) changes from Al ₄₀₅ to Ah ₄₀₅ .

Another effect of using the color development region 8 in the azo metal complex as shown in Chemical Formula 1 will be described. When the combination of the anion part and the cation part described above is used, a dye is used for the cation part. By combining with an anion portion that does not contribute to the color development region, the relative occupied volume of the color development region in the recording layer 3-2 is reduced. As a result, the light absorption cross-sectional area is relatively reduced, and the molar absorption coefficient is decreased. As a result, the absorbance value at the λ _{max write} position shown in FIG. 34 is decreased, and the recording sensitivity is decreased. In contrast, when utilizing the color development characteristics around the central metal of the azo metal complex described here, the azo metal complex itself emits light, so there is an extra portion that does not contribute to the color development region such as the anion portion described above. not exist. Therefore, there is no unnecessary factor for reducing the relative occupied volume of the coloring region, and the occupied volume of the coloring region 8 in the azo metal complex is wide as shown in Chemical Formula 1, so that the light absorption cross-sectional area is increased and the molar molecule is increased. The extinction coefficient value increases. As a result, the absorbance value at the λ _{max write} position shown in FIG. 34 is increased, and the recording sensitivity is improved.

  The electronic structure in the “δ” color development region described in “3-2-B] Basic features common to the organic dye recording material in the present embodiment” is stabilized, and structural decomposition against ultraviolet rays and reproduction light irradiation hardly occurs. As a specific method for achieving this, the main feature of the present embodiment is that the central metal of the azo metal complex is optimized to stabilize the structure of the color development region.

It is known that each metal ion has a unique ionization tendency characteristic. When these metal atoms are arranged in the order of strong ionization tendency, Na>Mg>Al>Zn>Fe>Ni>Cu>Hg>Ag> Au
It has become. This ionization tendency of metal atoms represents the “characteristic that metal emits electrons and becomes cations”.

Various metal atoms were inserted as the central metal of the azo metal complex having the structure shown in Chemical Formula 1 and the stability of repeated reproduction (the stability of the color development characteristics when repeatedly irradiated with light at around 405 nm with the reproduction power) was investigated. As a result, it was found that the metal atom having a higher ionization tendency emits electrons and breaks the bond, so that the color development region 8 is easily destroyed. As a result of numerous experiments, it has been found that it is desirable to use a metal material (Ni, Cu, Hg, Ag, Au) after nickel (Ni) as the central metal in order to ensure the structural stability of the color development region. Furthermore, it is most desirable to use copper (Cu) as the central metal in the present embodiment from the viewpoints of “high structural stability of the color development region”, “cost reduction”, and “use safety”. In this embodiment, any one of CH ₃ , C _x H _y , H, Cl, F, NO ₂ , and SO ₂ NHCH ₃ is used as R1, R2, R3, R4, and R5 that are side chains of Chemical Formula _1. .

  Next, a method for forming the organic dye recording material having the molecular structure shown in Chemical Formula 1 as the recording layer 3-2 on the transparent substrate 2-2 will be described. First, 1.49 g of the organic dye recording material in powder form is dissolved in 100 ml of TFP (tetrafluoro-propanol) which is a fluorine alcohol solvent. The above numerical value means that the mixing ratio is 1.4% by weight, and the actual usage varies depending on the production amount of the write-once information storage medium. The mixing ratio is desirably 1.2 to 1.5% by weight. As a solvent, it is an indispensable condition not to dissolve the surface of the transparent substrate 2-2 made of a polycarbonate resin, and the above alcohol is used. Since TFP (tetrafluoro-propanol) has polarity, the solubility of the organic dye recording material in powder form is improved. The organic dye recording material dissolved in the solvent is applied to the center of the transparent substrate 2-2 while rotating the transparent substrate 2-2 on the spindle motor, and the solvent evaporates after spreading using centrifugal force. After that, the recording layer 3-2 is hardened by a baking process for raising the entire temperature.

5-5) Azo metal complexation in which the central metal is ionically bonded to four oxygen atoms In the case of the structure in which two oxygen atoms are ionically bonded to the central metal shown in FIG. As shown in 2 (a) and (b), the recording principle is performed by the mutual arrangement angle between the U plane and the D plane formed by the benzene nucleus group.

As described above, by using copper or the like as the material of the central metal M, molecular bonds are strong and molecular destruction due to ultraviolet irradiation hardly occurs. Therefore, long-term stability is ensured as shown in Chemical Formula 2. However, when only two oxygen atoms are ion-bonded to the central metal M, the space between the U plane and the D plane formed by the benzene nucleus group as shown in the chemical formulas 2 (a) and (b) It is easy to rotate. For this reason, the repeated recording causes the unrecorded area shown in Chemical Formula 2 (a) to gradually change to the post-recording arrangement as shown in Chemical Formula 2 (b), resulting in a phenomenon that the recorded signal deteriorates.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

Sectional drawing which represents typically one embodiment of the information storage medium of this invention Sectional drawing which represents typically another example of the information storage medium of this invention FIG. 5 is a diagram for explaining the specification of a B-format optical disc. The figure which shows the structure of the picket code (error correction block) in B format. Explanatory drawing of the wobble address in B format. The figure which shows the detailed structure of the wobble address which combined the MSK system and the STW system. The figure which shows the ADIP unit expressing 1 bit of "0" or "1" which is a unit of 56 wobbles. The figure which shows the ADIP word which consists of 83 ADIP units and shows one address. The figure which shows ADIP word. The figure which shows 15 nibbles contained in an ADIP word. The figure which shows the track structure of B format. The figure which shows the recording frame of B format. The figure which shows the structure of a recording unit block. Diagram showing the structure of data run-in and data run-out. The figure which shows arrangement | positioning of the data regarding a wobble address. Explanatory drawing of the guard 3 area | region arrange | positioned at the end of a data run-out area | region. The figure showing the manufacturing process of the information storage medium concerning one Embodiment of this invention. The figure showing the manufacturing process of the information storage medium concerning one Embodiment of this invention. The figure showing the manufacturing process of the information storage medium concerning one Embodiment of this invention. The figure showing the manufacturing process of the information storage medium concerning one Embodiment of this invention. The figure showing the manufacturing process of the information storage medium concerning one Embodiment of this invention. The figure showing the manufacturing process of the information storage medium concerning one Embodiment of this invention. The perspective view showing the longitudinal section of the disc-shaped information storage medium concerning one embodiment of the present invention. The figure which expanded a part of section of Drawing 23 The figure which expanded the other part of the cross section of FIG. Diagram showing standard phase change recording film structure and organic dye recording film structure Explanatory drawing of an example of the light absorption spectrum characteristic of the organic dye recording material used for the current DVD-R disc The figure which shows the formation shape comparison of the recording film in the prepit area | region or the pregroove area | region 10 in a phase change recording film and an organic dye recording film The figure which shows the concrete plastic deformation state of the transparent substrate 2-2 in the recording mark 9 position in the write-once information storage medium using the conventional organic pigment | dye material. Explanatory drawing regarding the shape and dimensions of the recording film that facilitates the recording principle Characteristic illustration of shape and dimensions of recording film Explanatory diagram of light absorption spectrum characteristics in an unrecorded state in an “H → L” recording film Explanatory diagram of light absorption spectrum characteristics in a recording mark in an “H → L” recording film Explanatory diagram of light absorption spectrum characteristics in an unrecorded state in an “L → H” recording film The figure showing the light absorption spectrum characteristic change in the recorded state and the unrecorded state in the “L → H” recording film Explanatory drawing of an example of changes in optical absorption spectrum characteristics before and after recording in an “H → L” recording film Explanatory drawing of examples of changes in optical absorption spectrum characteristics before and after recording in an “L → H” recording film Explanatory drawing of another example of change in optical absorption spectrum characteristics before and after recording in “L → H” recording film

Explanation of symbols

  3-3: Second recording layer, 3-4: First recording layer, 4-3: Light semi-transmissive layer, 4-4: Light reflecting layer, 5,5-1, 5-2 ... Protective layer, 6-3 ... Second barrier layer, 6-4 ... First barrier layer, 7 ... Space layer, 8 ... Substrate, 11 ... Groove, 15 ... Information storage medium

Claims (4)

  Concentric circular or spiral lands and grooves are formed, a substrate having an opening at the center thereof, a land and a groove provided on the first light reflection layer and synchronized with the shape, and having a wavelength of 405 nm A first recording layer that is recordable and has a maximum absorption wavelength λmax higher than 405 nm, a first barrier layer provided on the first recording layer, and the first A space layer formed on a surface opposite to the surface facing the first barrier layer and having a land and a groove synchronized with the shape, and provided along the land and the groove of the space layer. A second light reflecting layer in which lands and grooves synchronized with the shape are formed, lands and grooves synchronized with the shape are formed, and can be reproduced at a wavelength of 405 nm, A second recording layer having a large absorption wavelength λmax higher than 405 nm and recordable, a second barrier layer formed on the second recording layer, and formed on the second barrier layer The groove has an inner zone and a data zone, and the inner zone has a BCA area, a pre-recording area, and a rewrite area, and the reproduction light is transmitted through the protective layer to the first and An information storage medium that can be reproduced by irradiating the second recording layer.   The first barrier layer and the second barrier layer have lands and grooves synchronized with the shape on both principal surfaces thereof, and the other principal surface is deeper than the land depth of the principal surface on the substrate side. The information storage medium according to claim 1, wherein the land land has a smaller depth.   2. The information storage medium according to claim 1, wherein a land width or a depth of the first recording layer is different from that of the second recording layer. A detection mechanism for detecting reflected light obtained by irradiating the information storage medium according to any one of claims 1 to 3 with laser light;
And a generating mechanism for generating a reproduction signal based on the reflected light detected by the detecting means.

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