JP2006244703A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium having in-groove pits, which is excellent in recording and reproduction characteristics and tracking characteristics. <P>SOLUTION: In the optical information recording medium, the in-groove pits which have flat bottom surfaces are arranged on a groove which has a flat bottom surface are disposed. Therefore, it is possible to increase the difference between a height position of an interface between a recording layer and a reflective layer at a groove portion formed with the recording layer containing an organic dye and a height position of the interface between the recording layer and the reflective layer at an in-groove pit portion, as compared with an optical information recording medium in which a wide-width portion and a narrow-width portion are formed on a groove. Accordingly, information which is recorded on the in-groove pits can be reproduced at a high modulation factor and at a low jitter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium, a manufacturing method thereof, a stamper used for manufacturing a substrate of the optical information recording medium, and a manufacturing method thereof, and in particular, media information such as a manufacturer name and copyright protection countermeasure information is in the form of prepits. The present invention relates to an optical information recording medium recorded in a groove, a manufacturing method thereof, a stamper used for manufacturing the substrate, and a manufacturing method thereof.

  In recent years, DVDs (digital versatile discs) having a recording capacity several times that of CDs (compact discs) have been widely used as information recording media for images and sounds. Also, a DVD-R (write-once digital versatile disc) that allows a user to record information only once on a DVD, or a DVD-RW (rewritable type) that allows information to be rewritten. Digital versatile discs) have already been commercialized and are expected to become widely used as future high-capacity information recording media.

  Normally, in DVD-R, predetermined information (hereinafter referred to as media information) such as disc manufacturer information, information for copyright protection measures, and output of laser light used for disc information recording and reproduction is recorded in advance on the disc. ing. These media information is recorded by modifying the recording layer by light irradiation or the like using a recording device at the final stage of the disc manufacturing process.

  In contrast to this, information such as media information is not recorded on the recording layer as described above, but is recorded in advance in the form of embossed pits (hereinafter referred to as in-groove pits) in the groove of the substrate in the substrate manufacturing stage of the disc. A method is disclosed (see, for example, Patent Documents 1, 2, and 3). FIG. 21 shows part of a substrate manufactured using these methods. FIG. 21A is a partially enlarged plan view of a substrate, and schematically shows a region where an in-groove pit is formed (hereinafter referred to as an in-groove pit region). FIGS. 21B and 21C are views showing a cross section taken along the line A′-A ′ and a cross section taken along the line B′-B ′ of FIG. 21A, respectively. In this substrate, as shown in FIG. 21 (b), the depth dp "up to the bottom surface (lowermost surface) 217a of the in-groove pit 217 with reference to the land surface 211a of the substrate 211 on which lands and grooves are formed. However, it is formed deeper than the depth dg ″ up to the bottom surface (lowermost surface) 215a of the groove 215 with reference to the land surface 211a. As a result, when an optical information recording medium is produced by forming a recording layer and a reflective layer on the pattern forming surface of the substrate 211, the portion where the in-groove pit 217 is formed and the in-groove pit 217 are not formed. There is a difference in the height of the surface of each layer formed with the groove portion. By utilizing the difference in depth between the in-groove pit portion and the groove portion, data such as media information can be recorded in the groove.

  An optical information recording medium using the substrate is manufactured as follows. A photoresist formed with a uniform thickness on the surface of the master is irradiated with a laser beam with a certain intensity to expose a pattern corresponding to the groove, and the intensity is modulated to an exposure intensity higher than the above-mentioned constant intensity exposure intensity. The pattern corresponding to the in-groove pit is exposed with the laser beam. The pattern corresponding to the groove and the pattern corresponding to the in-groove pit can be exposed by continuously switching the exposure intensity, or once the pattern corresponding to the groove is exposed, the pattern corresponding to the in-groove pit is exposed again. May be. Next, by developing the exposed master, a desired photoresist pattern corresponding to the groove and the in-groove pit is formed on the master. Next, an etching process such as RIE is performed on the photoresist pattern forming surface of the master, and a desired pattern corresponding to the groove and the in-groove pit is formed on the surface of the master. Next, a stamper is produced using a master having a pattern formed on the surface, and the substrate is further duplicated using this stamper. An optical information recording medium can be manufactured by forming various layers such as a recording film on the pattern forming surface of the replicated substrate.

  However, when the in-groove pit corresponding portion is exposed by the master exposure method as described above, as shown in FIGS. 22 (a) and 22 (b), at time T1 corresponding to the pit length of the in-groove pit to be formed. Since exposure is performed, the length L1 in the track direction of the in-groove pit formation portion 221 exposed to the photoresist is increased by an amount corresponding to the diameter D of the light spot SP2 irradiated to the photoresist on the master. Accordingly, the track direction length L2 of the space 222 arranged between the adjacent in-groove pit formation portions 221 'in the track direction is shortened accordingly. This increases the jitter of the in-groove pit reproduction signal read from the optical information recording medium.

  Usually, in an optical information recording medium such as a DVD-R, in order to suppress jitter of a prepit reproduction signal, a periodic cut 231a is provided in a part of the groove 231 as shown in FIG. It is known to separately form a prepit 232. When exposing a master used for manufacturing such an optical information recording medium, the exposure amount when the pattern corresponding to the pre-pit 232 is exposed is adjusted regardless of the exposure amount when the pattern corresponding to the groove 231 is exposed. be able to. Thus, for example, the prepit size can be reduced by reducing the exposure intensity when exposing the prepit formation portion, or the exposure time interval of the prepit formation portion can be determined before and after (exposure start end and exposure end end). By adjusting so that the time is reduced and shortened, redundancy of the prepit length can be suppressed or prevented.

However, in an optical information recording medium with in-groove pits, the exposure intensity of the in-groove pit formation part can be reduced by simply lowering the exposure intensity of the in-groove pit formation part or reducing the exposure time of the in-groove pit formation part before and after the master exposure. When the length is shortened by cutting, the exposure amount at the end in the track direction of the in-groove pit formation portion is insufficient, so that the photoresist at that portion is not exposed to the surface of the master. As a result, a desired photoresist pattern cannot be accurately formed on the master. Furthermore, in the master disk whose surface has been etched according to this photoresist pattern, as shown in FIG. 24, the bottom surface 242a of the in-groove pit formation portion 242 of the wall surface 242b facing the track direction of the in-groove pit formation portion 242 is used as a reference. the inclination angle theta ₂ when a becomes smaller. Also in the substrate of the optical information recording medium manufactured based on this master, the inclination angle of the wall surface facing the track direction of the in-groove pit is reduced in the same manner as the above master, so that the reproduction signal from this in-groove pit is reduced. The degree of modulation will decrease.

  By the way, in the optical information recording medium in which the recording layer containing the organic dye is formed on the pattern forming surface of the substrate, the height of the interface between the recording layer and the reflective layer is changed depending on the width of the pattern formed on the substrate. There is a difference. The height position of the interface between the recording layer and the reflective layer in the wide groove is lower than that in the narrow groove. As a result, a difference occurs between the optical path length of the laser light in the wide groove portion and the optical path length of the laser light in the narrow groove portion. A method of reproducing information such as media information using the difference in optical path length is disclosed (see, for example, Patent Document 4). However, the depth of the wide groove and the narrow groove formed on the substrate used in this method is the same.

  However, in the above optical information recording medium, although there is actually a slight difference in the height position of the interface between the recording layer and the reflective layer between the wide portion and the narrow portion of the groove, a signal sufficient to reproduce information is obtained. The difference in the optical path length of the laser beam that can obtain the degree of modulation cannot be generated. Even when the dimensional ratio between the wide portion and the narrow portion of the groove, the viscosity of the recording layer material, the rotational driving conditions of the substrate, and the like were variously changed, a sufficient optical path length difference could not be obtained. In addition, in the case of an optical information recording medium that records information such as media information using the wide part and the narrow part of the groove as described above, it is difficult to reduce the track pitch. This is disadvantageous in increasing the recording capacity of the optical information recording medium due to the narrowing.

  An optical information recording medium is disclosed in which the film thickness of the recording layer (dye layer) formed on the substrate differs depending on the depth of pits and grooves formed on the substrate surface (for example, Patent Document 5 and 6), neither document mentions an optical information recording medium having in-groove pits.

JP 2000-21024 (column 5-7, FIG. 1 and FIG. 8) JP 2001-67733 A (column 5-6, Fig. 1-3) JP 2002-216364 A (column 6-8, FIG. 1) JP-A-2001-351268 (columns 5-8, 4-5) JP-A-8-129780 (column 6-8, FIG. 1) Japanese Patent Laid-Open No. 2002-237093 (columns 7-15, FIG. 2-7)

  An object of the present invention is to provide an optical information recording medium having in-groove pits excellent in recording / reproducing characteristics and tracking characteristics, and a method for producing the same. Another object of the present invention is to provide a stamper used for manufacturing the substrate of the optical information recording medium and a manufacturing method thereof.

According to the first aspect of the present invention, a substrate having a land, a groove having a flat bottom surface and an in-groove pit having a flat bottom surface formed on one surface, and formed on the one surface of the substrate. An optical information recording medium having a recording layer containing an organic dye and a reflective layer formed on the recording layer,
The depth from the land surface of the substrate to the bottom surface of the groove is represented by dg, the depth from the land surface of the substrate to the bottom surface of the in-groove pit is represented by dp, and the recording layer and the reflective layer on the land surface The depression depth of the recording layer from the interface to the interface between the recording layer and the reflective layer in the groove is represented by Tg, and the recording layer in the in-groove pit from the interface between the recording layer and the reflective layer on the land surface Provided is an optical information recording medium characterized by dp / dg <Tp / Tg, where Tp represents the depth of the recording layer to the interface with the reflective layer.

  In the optical information recording medium of the present invention, since the groove having a flat bottom surface is provided with in-groove pits having a flat bottom surface, the optical information recording medium has a wide portion and a narrow portion formed in the groove. The difference between the height position of the interface between the recording layer and the reflective layer in the groove portion where the recording layer containing the organic dye is formed and the height position of the interface between the recording layer and the reflective layer in the in-groove pit portion is increased. can do. As a result, information recorded in the in-groove pit can be reproduced with high modulation and low jitter. In addition, since the wide portion is not provided in the groove, it is possible to improve the recording density by narrowing the track pitch. In the optical information recording medium of the present invention, the depth from the land surface of the substrate to the bottom surface of the in-groove pit (hereinafter referred to as the in-groove pit depth) dp and the depth from the land surface of the substrate to the bottom surface of the groove (hereinafter referred to as the groove surface) The relationship between the ratio dp / dg (referred to as groove depth) dg and the ratio Tp / Tg between the depression depth Tp of the recording layer in the in-groove pit and the depression depth Tg of the recording layer in the groove is dp / dg <Tp. A recording layer containing an organic dye is formed so as to satisfy / Tg. Thereby, even when the in-groove pit depth dp and the groove depth dg are not formed to have a predetermined signal modulation degree and a radial push-pull signal, the optical path length of the light passing through the groove and the in-groove pit The difference from the optical path length of the light passing through can be increased. Accordingly, since the in-groove pit depth dp can be made shallower than the groove depth dg, it is possible to facilitate the master cutting and substrate molding and to reduce the manufacturing cost of the optical information recording medium. In particular, it is preferable that 1.15 <(Tp / Tg) / (dp / dg).

  In the present invention, the ratio Tp / Tg between the depth Tg of the recording layer in the groove and the depth Tp of the recording layer in the in-groove pit is 1.6 ≦ Tp / Tg ≦ 2.0. Is desirable. As a result, information recorded in the in-groove pit can be reproduced with a high degree of modulation and a low jitter. In the optical information recording medium of the present invention, for example, a modulation degree of 60% or more can be obtained and the jitter can be suppressed to 8% or less, so that practically sufficient reproduction characteristics can be obtained. Further, it is desirable that the groove depth dg is dg> λ / 4n, where λ represents the wavelength of light used for recording or reproduction of the optical information recording medium and n represents the refractive index of the substrate. Generally, the groove can be detected with the highest contrast when the optical path length difference between the light transmitted through the groove portion and the light transmitted through the land portion is λ / 4n. In an optical information recording medium using an organic dye material for the recording layer, since the state of the recording layer is different between the groove portion and the land portion, the optical path between the light transmitted through the groove portion and the light transmitted through the land portion is usually different. The length difference will be λ / 4n or less, and the groove cannot be detected with good contrast. In the optical information recording medium of the present invention, the groove depth dg is formed so that dg> λ / 4n, so that the optical path difference between the light transmitted through the groove portion and the light transmitted through the land portion is λ / 4n. It becomes easy to adjust the stacking conditions of the recording layer so as to expand. As a result, the groove portion and the land portion can be detected with the highest contrast.

According to the second aspect of the present invention, a substrate having a land, a groove having a flat bottom surface and an in-groove pit having a flat bottom surface formed on one surface, and formed on the one surface of the substrate. Optical information recording comprising: a reflective layer; a recording layer containing an organic dye formed on the reflective layer; a protective layer formed on the recording layer; and a cover layer formed on the protective layer A medium,
The depth from the land surface of the substrate to the bottom surface of the groove is represented by dg, the depth from the land surface of the substrate to the bottom surface of the in-groove pit is represented by dp, and the recording layer and the protective layer on the land surface The depression depth of the recording layer from the interface with the recording layer to the interface between the recording layer and the protective layer in the groove is represented by Tg ′, and the recording layer at the in-groove pit from the interface between the recording layer and the protective layer on the land surface An optical information recording medium is provided wherein dp / dg <Tp ′ / Tg ′, where Tp ′ represents the depth of depression of the recording layer to the interface between the protective layer and the protective layer.

  In the optical information recording medium of the present invention, information is recorded and reproduced by making light incident from the cover layer side. By satisfying the relationship of dp / dg <Tp ′ / Tg ′, the optical information of the first aspect is obtained. The same effects as the recording medium can be obtained.

  In the present invention, the ratio Tp ′ / Tg ′ between the depth Tg of the recording layer in the groove and the depth Tp of the recording layer in the in-groove pit is 1.6 ≦ Tp ′ / Tg ′ ≦ 2. 0 is desirable. Further, when the wavelength of light used for recording or reproduction of the optical information recording medium is represented by λ and the refractive index of the cover layer is represented by n, the depth dg to the bottom surface of the groove is dg> λ / 4n. It is desirable to be.

  In the optical information recording medium of the above aspect, the ratio dp / dg between the groove depth dg and the in-groove pit depth dp is preferably 1.4 ≦ dp / dg ≦ 1.7. In order to obtain a predetermined signal modulation degree and radial push-pull signal, it is preferable that the ratio of the optical path length of light passing through the groove to the optical path length of light passing through the in-groove pit is set to about 1.6 to 2.0. . However, the optical information recording medium of the present invention can increase the difference between the optical path length in the groove and the optical path length in the in-groove pit by forming the recording layer using the organic dye material, so that the groove depth Even when the ratio dp / dg between dg and in-groove pit depth dp is 1.6 to 2.0 or less as described above, the optical path length of light passing through the groove and the optical path length of light passing through the in-groove pit The ratio can be about 1.6 to 2.0. Thereby, a predetermined signal modulation degree and a radial push-pull signal can be obtained. In addition, information recorded in the in-groove pit can be reproduced with high modulation and low jitter.

According to the third aspect of the present invention, there is provided a master cutting (lithography) process for forming a groove and an in-groove pit provided in the groove on the master, and a reversal pattern of the groove and the in-groove pit of the master. An optical information recording medium manufacturing method comprising a stamper manufacturing process for manufacturing a transferred stamper, a substrate replication process for replicating a substrate from the stamper, and a film forming process for forming at least one layer on the surface of the replicated substrate. And
The master cutting process is formed on the surface of the master by exposing a photoresist formed on the surface of the master with light having a first exposure intensity to form the groove pattern on the master. An in-groove pit exposure step of forming the in-groove pit pattern on the master by exposing the photoresist with light having a second exposure intensity set higher than the first exposure intensity;
There is provided a method for producing an optical information recording medium, characterized in that a period of exposure with a third exposure intensity lower than the first exposure intensity is provided between the groove exposure process and the in-groove pit exposure process. The

  In the method for producing an optical information recording medium according to the present invention, when switching between the groove exposure step and the in-groove pit exposure step, a period of exposing the photoresist with a third exposure intensity lower than the first exposure intensity ( (Hereinafter referred to as blank cutting amount or blank period), the front end and the rear end in the track direction of the in-groove pit formation portion are compared with the case where the exposure time interval of the in-groove pit formation portion is simply shortened by cutting back and forth. The end portion can be exposed with a sufficient exposure amount. Thus, the photoresist formed on the master is sufficiently exposed to the interface with the master, so that a photoresist pattern corresponding to a desired preformat pattern can be formed by performing development processing. By performing etching based on this photoresist pattern, the inclination angle of the wall surface facing the track direction of the in-groove pit formation portion can be formed large. Therefore, a stamper is produced based on this master, and a substrate having a concavo-convex pattern similar to the preformat pattern formed on the master surface can be produced by using the stamper. Further, by forming various layers such as a recording layer and a reflective layer on the substrate, an optical information recording medium capable of reproducing the in-groove pits with a high modulation degree and a low jitter can be manufactured.

  In the present invention, it is desirable to set the exposure period at the third exposure intensity based on the modulation degree, jitter, and radial push-pull value of the reproduction signal of the in-groove pit. The blank period is desirably a value at which the modulation degree of the in-groove pit reproduction signal is maximized and maximized. Further, the blank period is desirably a value when the jitter value of the in-groove pit reproduction signal is minimum and minimum. The radial push-pull value decreases as the blank period increases. In addition, since there is a correlation among the three parameters of the modulation degree of the in-groove pit reproduction signal, jitter, and radial push-pull, by selecting the blank period of the optimum condition from these relationships, the in-groove pit and It is possible to optimize the shape of the space and to obtain a high recording density optical information recording medium having excellent recording / reproducing characteristics and tracking characteristics. In particular, from the viewpoint of optimizing the above three parameters, it is desirable that the exposure period (blank period) at the third exposure intensity is 0.2T when the clock cycle is represented by T. Further, the third exposure intensity may be zero.

According to the fourth aspect of the present invention, a master cutting (lithography) step for forming a groove and an in-groove pit provided in the groove on the master, the groove of the master and the inversion pattern of the in-groove pit A stamper manufacturing method including a stamper manufacturing step of manufacturing a stamper to which is transferred,
The master cutting process is formed on the surface of the master by exposing a photoresist formed on the surface of the master with light having a first exposure intensity to form the groove pattern on the master. An in-groove pit exposure step of forming the in-groove pit pattern on the master by exposing the photoresist with light having a second exposure intensity set higher than the first exposure intensity;
A stamper manufacturing method is provided, wherein a period of exposure with a third exposure intensity lower than the first exposure intensity is provided between the groove exposure process and the in-groove pit exposure process.

  The present invention provides a method for manufacturing a stamper used for manufacturing a substrate for an optical information recording medium in which the shape of in-groove pits and spaces arranged in the groove is optimized.

  In the present invention, it is desirable to set the exposure period at the third exposure intensity based on the modulation degree, jitter, and radial push-pull value of the reproduction signal of the in-groove pit. Further, when the clock cycle is represented by T, it is desirable that the period of exposure with the third exposure intensity is 0.2T. Further, the third exposure intensity may be zero.

According to a fifth aspect of the present invention, there is provided a stamper manufactured using the stamper manufacturing method according to the fourth aspect,
A stamper is provided in which the bottom surface of the groove and the bottom surface of the in-groove pit are flat, and the inclination angle of the wall surface facing the track direction of the in-groove pit is 40 degrees or more and less than 90 degrees. .

  By using the stamper of the present invention, it is possible to produce an optical information recording medium substrate on which grooves and in-groove pits satisfying the above conditions are formed. In the substrate thus obtained, a reproduction signal having a good modulation degree can be obtained from the in-groove pit.

  Embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  As shown in FIG. 1, the optical information recording medium 10 according to the present invention is formed in a disc shape having a center hole 10a with the center AX as a reference. Further, as shown in FIGS. 1 and 2, the optical information recording medium 10 has a substrate 1 on which a preformat pattern 10b such as a groove 8 or an in-groove pit 9 is formed on one surface. The recording layer 2, the reflective layer 3, and the protective layer 4 are formed in this order.

  The substrate 1 can be a plastic substrate molded using an injection molding method, a compression molding method, or an injection compression molding method. Or you may use the glass substrate produced using 2P method (photosensitive resin method).

  As shown in FIGS. 3A to 3C, the preformat pattern 10b formed on the substrate 1 includes in-groove pits 9 for optically reading information such as address information, and recording / reproducing light. The in-groove pit 9 is formed on the groove 8. Further, as shown in FIG. 3B, the information such as the address information includes an in-groove pit 9 and a groove portion adjacent to the in-groove pit 9 where no in-groove pit is formed (hereinafter referred to as a space). It is composed of an 8 ′ array. The length L1 of the in-groove pit 9 and the length L2 of the space 8 'are adjusted to either 3T to 11T or 14T, respectively, where T is the clock period. The preformat pattern 10b is formed in a spiral shape or a concentric shape with the center AX of the optical information recording medium 10 as a reference.

  The substrate 1 is manufactured using a master having the same concavo-convex pattern as the preformat pattern on the surface and a stamper obtained from the master. The master disc in the present invention is produced by the following master disc cutting method (lithography). When exposing a desired in-groove pit pattern to the photoresist formed on the master surface, a period in which the exposure intensity of exposure light is temporarily set lower than the level at which the groove pattern is exposed (blank) Period) before and after the in-groove pit pattern exposure period. Thereby, redundancy in the track direction of the in-groove pit pattern according to the diameter of the laser spot can be prevented. Note that the blank period is set based on the modulation degree, jitter, and radial push-pull values of the reproduction signal of the in-groove pit detected from the optical information recording medium. Next, the exposed master is developed to form a desired photoresist pattern on the master. By performing etching such as RIE based on this resist pattern, a desired preformat pattern composed of an in-groove pit pattern and a groove pattern is formed on the surface of the master. Both the in-groove pit pattern and the groove pattern are formed so that the cross-sectional shape is substantially trapezoidal. A stamper can be obtained by forming a metal layer of Ni or the like on the preformat pattern forming surface of the master produced by the above method using an electroforming method or the like.

As shown in FIGS. 3B and 3C, the in-groove pit 9 formed on the substrate 1 thus obtained has a bottom surface 9a having a flat cross-sectional shape and a wall surface standing from the periphery of the bottom surface 9a. 9b is formed to be substantially trapezoidal. At this time, the inclination angle θ ₁ of the wall surface 9 b facing the track direction of the in-groove pit 9 is formed to be 40 degrees or more and less than 90 degrees with respect to the bottom surface 9 a of the in-groove pit 9. The ratio A1 / A2 between the shortest in-groove pit length A1 and the shortest space length A2 is 0.8 to 1.2 at the half-value portion of the depth of the in-groove pit 9, and The ratio h1 / h2 between the height h1 of the shortest space 8′a from the bottom surface 9a and the height h2 of the space 8′b other than the shortest space is 0.95 or more and 1.0 or less. On the other hand, as shown in FIG. 3C, the groove 8 is formed to be substantially trapezoidal with a bottom surface 8a having a flat cross-sectional shape and a wall surface 8b erected from the periphery of the bottom surface 8a. Needless to say, the depth d2 from the land surface 1c of the substrate 1 to the bottom surface 8a of the groove 8 is shallower than the depth d1 from the land surface 1c of the substrate 1 to the bottom surface 9a of the in-groove pit 9. In this specification, “substantially trapezoidal” means a shape having a slight roundness at the corner where the bottom surface and the inclined wall surface intersect, and at the corner where the land surface 1c and the inclined wall surface intersect, in addition to a mathematically complete trapezoid. In addition, a shape having slight distortion on each surface is also included. In this specification, the flat bottom surface means a surface having a flat portion that is substantially parallel to the land surface of the substrate and is defined by a width of at least 50 nm in the radial direction and the track direction of the substrate.

  Next, the recording layer 2 formed on the substrate 1 uses a low melting point alloy, a phase change recording material, a magneto-optical recording material, an organic dye material, or the like in accordance with the information recording / reproducing method in the optical information recording medium. Formed. In FIG. 2, the recording layer 2 is shown as a single layer, but the recording layer 2 may be formed of a laminate of the same or different thin films as required. For example, in the case of a magneto-optical recording medium, the recording layer may be formed by a laminate composed of a first enhancement film made of an inorganic dielectric, a magneto-optical recording film made of a perpendicular magnetization film, and a second enhancement film made of an inorganic dielectric. it can.

  The reflective layer 3 formed on the recording layer 2 is made of a metal material or an alloy material having a high light reflectivity for recording / reproducing light, such as silver or silver alloy, aluminum or aluminum alloy, gold or gold alloy, titanium or titanium alloy. Formed using. In the case of a read-only optical information recording medium, the recording layer may not be formed, and the reflective layer may be formed directly on the preformat pattern forming surface of the substrate.

  The protective layer 4 is a layer for protecting the recording layer 2 and the reflective layer 3 from mechanical impacts and chemical changes, and is the same or different kind of inorganic dielectric or ultraviolet curable resin as the inorganic dielectric constituting the enhancement film. It is formed using an organic material such as. Further, a substrate (dummy substrate) having a flat surface as a cover layer on the protective layer 4 and formed of plastic in the same manner as the substrate 1 may be attached to the protective layer 4 via an ultraviolet curable resin or the like. Good.

  The depth of the in-groove pit and the film thickness of the recording layer in the optical information recording medium of the present invention are determined as follows. When the wavelength of the recording / reproducing light is λ, the light is incident from the substrate, passes through the land surface, reaches the interface between the recording layer and the reflective layer, is reflected at the interface, and is guided again through the land surface to the substrate side. Light that is incident on the substrate, passes through the bottom surface of the in-groove pit, reaches the interface between the recording layer and the reflective layer, is reflected at the interface, and is guided again to the substrate side through the bottom surface of the in-groove pit These film thicknesses are adjusted so that the optical path difference between λ / 6 and λ / 3 becomes λ / 6. The groove depth is such that when the wavelength of the recording / reproducing light is λ, it enters from the substrate, passes through the land surface, reaches the interface between the recording layer and the reflective layer, is reflected at the interface, and is land again. Light that is guided to the substrate side through the surface, enters from the substrate, reaches the interface between the recording layer and the reflective layer through the bottom surface of the groove, is reflected at the interface, and passes again through the bottom surface of the groove to the substrate side The optical path difference from the light guided to is adjusted to be λ / 16 to λ / 8.

  Depending on the type and film thickness of the recording layer 2, the interface between the recording layer 2 and the reflective layer 3 does not become flat as shown in FIG. 4, and a depression corresponding to the surface shape of the groove 8 and the in-groove pit 9 is obtained. 8 'and 9' are formed. In this case, the depths 8 ′ and 9 ′ of the depressions are obtained in advance by experiment, and the depth d1 of the in-groove pit 9, the depth d2 of the groove 8 and the film thickness t of the recording layer 2 are determined according to the values. The value may be adjusted to satisfy the above optical path difference condition.

  Further, when the reflective layer 3 is directly formed on the preformat pattern forming surface of the substrate, for example, in a reproduction-only optical information recording medium, when the wavelength of the recording / reproducing light is λ and the refractive index of the substrate is n The depth of the in-groove pits may be formed to λ / 6n to λ / 3n, and the depth of the grooves may be formed to λ / 16n to λ / 8n.

  In the optical information recording medium of the present invention, both the in-groove pits and the cross-sectional shape of the groove are formed in a substantially trapezoidal shape having a flat bottom surface, so that the radial push-pull is more stable than an optical information recording medium having a groove whose bottom surface is not flat. A signal can be obtained. Further, noise with respect to a reproduction signal detected from the in-groove pit can be reduced. Thereby, it is possible to increase the recording density of the optical information recording medium and increase the S / N ratio of the reproduction signal.

  In addition, as described above, the inclination angle of the wall surface facing the track direction of the in-groove pit formed on the substrate of the optical information recording medium is 40 degrees or more and less than 90 degrees with respect to the bottom surface of the in-groove pit. The ratio of the shortest prepit length to the shortest space length is 0.8 to 1.2 at the half-value portion of the depth of the in-groove pit, and the height of the shortest space from the bottom surface of the in-groove pit and the in-groove pit Since the ratio of the height of the space other than the shortest space from the bottom surface is 0.95 to 1.0, an in-groove pit reproduction signal can be obtained with a high degree of modulation and low jitter.

  In another embodiment of the present invention, a media information recording area in which media information is recorded in advance using in-groove pits on a surface of a substrate of an optical information recording medium on which a preformat pattern is formed; A user recording area for recording is provided. This eliminates the need to write media information one after another on the recording layer of the optical information recording medium by using a dedicated recording apparatus. This simplifies the manufacturing process of the optical information recording medium, and thus the manufacturing cost of the optical information recording medium. Can be reduced.

  The preformat pattern formed in the media information recording area has a substantially trapezoidal groove shape having a flat bottom surface and a substantially trapezoidal groove shape having a flat bottom surface disposed in the groove, as in the above embodiment. It consists of in-groove pits. The in-groove pits are prepared with a length of 3T to 11T or 14T when the clock cycle is T, and media information is recorded by an array of a plurality of in-groove pits having different lengths. .

  As shown in FIG. 19A, the depth from the land surface 1′a of the substrate 1 ′ to the bottom surface 182a of the groove 182, that is, the groove depth dg is the laser beam used for recording and reproducing information. When the wavelength is λ and the refractive index of the substrate 1 ′ is n, it is formed at a depth slightly deeper than λ / 4n. Further, the depth from the land surface 1 ′ a of the substrate 1 ′ to the bottom surface 183 a of the in-groove pit 183, that is, the in-groove pit depth dp is formed deeper than the groove depth dg. The ratio dp / dg between the groove depth dg and the in-groove pit depth dp is formed to be in the range of 1.4 ≦ dp / dg ≦ 1.7 in order to facilitate the production of the substrate 1 ′. The

  Further, as shown in FIG. 20, in the case of an optical information recording medium that records and reproduces information by irradiating laser light from the cover layer 5 ″ side instead of the substrate 1 ″, the land surface 1 ″ a of the substrate 1 ″ From the groove 201 to the bottom surface 201a of the groove 201, that is, the groove depth dg is λ / where the wavelength of the laser beam used for recording and reproducing information is λ and the refractive index of the dummy substrate 5 ″ is n. The depth from the land surface 1 ″ a of the substrate 1 ″ to the bottom surface 202a of the in-groove pit 202, that is, the in-groove pit depth dp ′ is the groove depth. The ratio dp ′ / dg ′ between the groove depth dg ′ and the in-groove pit depth dp ′ is set to 1.4 ≦ dp ′ / dg ′ ≦ 1.7 It is formed.

  In the optical information recording medium of the present embodiment, the preformat pattern constituting the user recording area is substantially trapezoidal groove-shaped having a flat bottom surface in the same manner as the preformat pattern for constituting the media information recording area. And a substantially trapezoidal in-groove pit having a flat bottom surface disposed in the groove, or a wobble pit for tracking control may be provided without providing the groove.

  The recording layer 2 ′ shown in FIG. 19A is formed by spin-coating an organic dye dissolved in an organic solvent on the preformat pattern forming surface of the substrate 1 ′. Since an external force such as a centrifugal force is applied during spin coating, the surface of the recording layer 2 ′ is not smooth, and is formed in an uneven shape corresponding to the groove depth dg and the in-groove pit depth dp. The recording layer 2 ′ is a depression of the recording layer from the interface between the recording layer 2 ′ and the reflective layer 3 ′ on the land surface 1′a of the substrate 1 ′ to the interface between the recording layer 2 ′ and the reflective layer 3 ′ in the groove 182. The recording layer 2 'and the reflective layer in the in-groove pit 183 from the interface between the recording layer 2' and the reflective layer 3 'on the land surface 1'a of the substrate 1' rather than the depth (recording layer maximum depression depth) Tg. The recording layer recess depth to the interface with 3 ′ (recording layer maximum recess depth) Tp is formed to be larger. Further, the ratio Tp / Tg between the maximum recording layer recess depth Tg and the maximum recording layer recess depth Tp is larger than the ratio dp / dg between the groove depth dg and the in-groove pit depth dp. Is done. Thus, even when the ratio dp / dg is not formed so as to obtain a good signal modulation degree and a radial push-pull signal, the optical path length of the laser light in the groove and the optical path length of the laser light in the in-groove pit The optical path length difference (≈2 × (Tp−Tg)) can be increased. Tp / Tg is formed so as to satisfy a range of 1.6 ≦ Tp / Tg ≦ 2.0 in order to reproduce media information with high signal modulation and low jitter. Further, for all in-groove pits having different lengths, the recording layer maximum depression depth Tp is adjusted to the same level, and the value of Tp / Tg is formed within the above range. Furthermore, as the organic dye material, for example, a known organic dye material applicable to a write-once type optical information recording medium, such as an azo dye or a cyanine dye, can be used.

  Hereinafter, the manufacturing method of the optical information recording medium in the 1st Embodiment of this invention is demonstrated using FIGS.

  The optical information recording medium described above is a master cutting process for forming a desired pattern on the surface of the master, a stamper manufacturing process for preparing a stamper based on the master that has been cut, and a substrate of the optical information recording medium is duplicated from the manufactured stamper. The substrate is manufactured through a substrate manufacturing step and a film forming step of forming various films on the replicated substrate.

[Manufacturing method of master and stamper for substrate manufacture]
First, a method for manufacturing a master and a stamper for manufacturing the substrate 1 of the optical information recording medium in the present invention will be described with reference to FIGS. As shown in FIG. 5A, a glass master 51 having a diameter of 200 mm and a thickness of 6 mm was prepared. Next, as shown in FIG. 5B, a photoresist 52 was uniformly applied to a thickness of 200 nm on one surface 51a of the glass master 51 by using a spin coating method. Next, the glass master 51 on which the photoresist 52 was formed was mounted on a master cutting apparatus (master exposure apparatus) 50 shown in FIG. The master cutting apparatus 50 mainly includes a Kr gas laser oscillator 53 that oscillates a laser beam having a wavelength of 351 nm, an optical modulator 54 that includes an acoustic light modulator, a signal source 55 that supplies a modulation signal to the optical modulator 54, and a condenser lens 56. And a driving device (not shown) for rotating the glass master. As shown in FIG. 5C, the laser light LS emitted from the laser oscillator 53 of the master cutting device 50 is irradiated to the photoresist 52 on the glass master 51 through the optical modulator 54 and the condenser lens 56. Is done. At this time, the glass master 51 was rotated at a predetermined rotational speed around the central axis BX of the glass master 51. Further, the laser beam LS is moved so that the irradiation position of the laser beam LS on the glass master 51 moves from the inside to the outside of the glass master 51 along the radial direction of the glass master 51 (arrow AR1). .

  As described above, while moving the laser beam LS, the exposure intensity of the laser beam LS applied to the glass master 51 is changed using the optical modulator 54. In this example, as shown in FIG. 6A, the exposure intensity of the laser beam was changed in two steps, a low level and a high level. The exposure intensity when forming a groove forming portion that does not have an in-groove pit forming portion was set to a low level (hereinafter referred to as a groove level). Further, the exposure intensity when forming the groove forming portion having the in-groove pit forming portion is set to a high level (hereinafter referred to as pit level) for the in-groove pit forming portion, and for the other groove forming portions, Set to groove level. The groove level was set so that the exposure intensity was 55% when the pit level was 100%. As a result, the photoresist in the in-groove pit formation portion is exposed to the interface between the photoresist and the master, whereas the photoresist in the groove formation portion is not exposed to the interface between the photoresist and the master. Each in-groove pit formation portion is formed with a channel bit length of 3T to 11T or 14T in the track direction, where T is a clock cycle. Note that the clock period T can be adjusted as appropriate according to the reproduction apparatus used.

  Further, in this embodiment, the exposure intensity of the in-groove pit formation portion is temporarily changed every time the exposure intensity is switched from the groove level to the pit level or from the pit level to the groove level as shown in FIG. In particular, a period (blank period) BE in which the exposure intensity of the laser beam is lower than the groove level is provided. In this embodiment, the exposure intensity of the laser beam in the blank period BE is set to 0 level. By providing the blank period, as shown in FIG. 6B, the exposure amount of the photoresist at the front end portion 62a and the rear end portion 62b of the in-groove pit formation portion 62 corresponds to the radius of the laser spot SP1, respectively. Exposure amount. Thereby, redundancy of the in-groove pit corresponding to the diameter of the laser spot SP1 can be prevented. In addition, since the photoresist in the in-groove pit formation portion is exposed with sufficient exposure intensity as described above, it is possible to eliminate insufficient exposure of the photoresist at the front end portion and the rear end portion of the in-groove pit formation portion. It is possible to form an in-groove pit formation portion with high processing accuracy such that the inclination angle of the wall surfaces of the front end portion and the rear end portion of the in-groove pit formation portion is not less than 40 degrees and less than 90 degrees.

  The blank period BE is set based on three parameters of the modulation degree of the in-groove pit reproduction signal detected from the optical information recording medium, jitter, and radial push-pull. The blank period BE can be changed according to the channel bit length of the in-groove pit to be formed. In this embodiment, the blank period BE is set to 0.2 T based on the values of three parameters at the time of exposure of the in-groove pit formation portion having the shortest channel bit length of 3T. A method for setting the blank period will be described later.

  Next, the glass master on which the photoresist was exposed was taken out of the cutting apparatus and developed. As a result, as shown in FIG. 7A, the groove forming portion 71 and the in-groove pit forming portion 72 were formed on the glass master 51. The groove forming portion 71 is formed to have a V-shaped groove shape in cross section. Further, in the in-groove pit formation portion 72, the photoresist 52 on the glass master 51 is removed by development processing, and the surface 51a of the glass master 51 appears as an exposed portion 72a.

Next, as shown in FIG. 7B, the surface of the photoresist 52 formed on the glass master 51 is made of C ₂ F ₆ gas by using a RIE (reactive ion etching) apparatus (not shown). Etched in atmosphere. Instead of the C ₂ F ₆ gas, a gas such as CF ₄ or C ₃ F ₆ may be used. As a result, the in-groove pit formation portion 72 is etched from the surface 51a of the glass master 51 to a depth of 90 nm. Next, as shown in FIG. 7C, in order to expose the surface 51a of the glass master 51 in the groove forming portion 71, a resist ashing apparatus using O ₂ (not shown) is used to remove the photoresist 52 by a predetermined thickness. Shaved. Thus, the glass master surface 71a of the groove forming portion 71 was exposed. Further, as shown in FIG. 8A, RIE was performed again on the surface of the glass master 51 on which the photoresist 52 was formed in a C ₂ F ₆ gas atmosphere. As a result, the groove forming portion 71 was etched from the glass master surface 51a to a depth of 170 nm. At the same time, the in-groove pit formation portion 72 was etched from the glass master surface 51a to a depth of 260 nm. Next, as shown in FIG. 8B, the photoresist 52 on the glass master 51 was removed again using a resist ashing device (not shown). Thereby, the glass master 51 in which the desired uneven | corrugated pattern was formed on the surface was obtained.

  The inclining angle of the wall surface facing the track direction of the in-groove pit formation portion of the glass master obtained in this way, the shortest prepit length and the shortest space length in the half-value portion of the in-groove pit depth, and the shortest space from the bottom of the in-groove pit The ratio between the height and the height from the bottom of the in-groove pit of the space other than the shortest space was determined using an atomic force microscope.

  In the in-groove pit having a pre-pit length of 3T, the inclination angle of the wall surface facing the track direction of the in-groove pit formation portion was 60 degrees. In addition, in the in-groove pit formation portion having other pre-pit lengths, the inclination angles of the wall surface at the front end portion and the rear end portion in the track direction are both 40 degrees or more and less than 90 degrees.

  The shortest prepit length in the half-value portion of the depth of the in-groove pit was 400 nm to 420 nm. The shortest space length was 355 nm to 375 nm.

  The height from the bottom surface of the in-groove pit in the shortest space (distance from the bottom surface of the in-groove pit to the bottom surface of the groove) is 90 nm to 85 nm (the distance from the bottom surface of the in-groove pit to the land surface is 262 nm to 258 nm). ). Further, the height from the bottom surface of the in-groove pit of the space other than the shortest space was 90 nm to 85 nm. Therefore, the ratio of the height from the bottom surface of the in-groove pit in the shortest space to the height from the bottom surface of the in-groove pit in the space other than the shortest space is 0.95 to 1.0. From this, it can be seen that the height of any space from the bottom surface of the in-groove pit is substantially the same.

  Next, electroless plating was applied to the pattern forming surface of the glass master as a pretreatment for plating. Further, by using this plating layer as a conductive film, a Ni layer having a thickness of 0.3 mm was formed by electroforming. Next, the surface of the Ni layer formed on the glass master was polished, and the Ni layer was peeled off from the glass master to obtain a stamper 91 as shown in FIG. On the surface of the stamper 91, an inverted pattern 92 of the concavo-convex pattern formed on the surface of the master is formed. In addition, you may perform the electrically conductive film formation in the pre-processing of the said plating using a sputtering method or a vapor deposition method. Further, the stamper may be manufactured by adding another process such as bonding a backing material to the stamper.

[Method for producing optical information recording medium]
Next, a method for manufacturing an optical information recording medium will be described with reference to FIGS. The stamper was mounted on an existing injection molding apparatus, and the substrate 1 was obtained by injection molding. The substrate 1 is a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm. As shown in FIG. 10, the substrate 1 has the same shape as the concavo-convex pattern shape such as the groove forming portion and the in-groove pit forming portion formed on the glass master. The pattern is transferred onto one surface of the substrate 1 (land 7, groove 8 and in-groove pit 9). The bottom surface of the in-groove pit formed on this substrate was observed using a transmission electron microscope (TEM). It has been found that a flat region defined by a width of at least 50 nm exists in the radial direction and the track direction of the substrate on the bottom surface of the in-groove pit. Similarly, the bottom surface of the groove formed on the substrate was observed using a transmission electron microscope (TEM). It has been found that a flat region defined by a width of at least 50 nm is also present on the bottom surface of the groove in the radial direction and the track direction of the substrate.

  A solution having a concentration of 1% by weight of an azo dye represented by the following chemical formula (1) is spin-coated on the pattern forming surface of the substrate 1 so as to have a thickness of 30 nm between the grooves, that is, between the lands. It was applied using the method. At this time, the application amount of the solution was 1 g, and the substrate was rotated at a rotation speed of 100 rpm for 30 seconds from the start of application, and then at a rotation speed of 800 to 1000 rpm for 30 seconds. In addition, when apply | coating the said pigment | dye solution, it was set as the azo dye solvent by using tetrafluoropropanol as a solvent, and it filtered with the filter, and removed the impurity. Further, the spin coating of the dye solution was performed from a radius of 21.0 mm to the outer peripheral portion with reference to the rotation center of the substrate 1. Subsequently, the board | substrate 1 which apply | coated the said pigment | dye material was dried at 70 degreeC for 1 hour, and also it cooled at room temperature for 1 hour. Thus, the recording layer 2 was formed on the substrate 1 (see FIG. 11). In addition, since an external force such as a centrifugal force is applied during spin coating, the surface of the recording layer 2 is not smooth, and is formed in an uneven shape according to the depth of the groove and the depth of the in-groove pit.

  Further, as shown in FIG. 11, an Ag alloy was formed as the reflective layer 3 on the recording layer 2 by a sputtering method so as to have a thickness of 100 nm. Next, an ultraviolet curable resin 4 is applied on the reflective layer 3 by a spin coating method so as to have a thickness of 10 μm, and a 0.6 mm thick polycarbonate substrate (dummy) similar to the substrate 1 is further formed thereon. Substrate) 5 was placed with its center aligned. In this state, the substrate 1 on which each layer was formed was irradiated with ultraviolet rays to solidify the ultraviolet curable resin 4, whereby the substrate 1 on which each layer was formed and the dummy substrate 5 were bonded together. Thereby, an optical information recording medium 110 was obtained.

[Blank period setting method]
Below, the setting method of a blank period is demonstrated using FIGS. 12 (a) to 12 (c), tracks of 3T signal recording portions (prepit length 3T and space length 3T) on each substrate manufactured using three types of masters cut by changing the blank period. A sectional shape and a planar shape of a direction are shown. Note that these cross-sectional and planar shapes were both measured using an atomic force microscope. FIG. 12A shows the cross-sectional shape (reference symbol a-1) and planar shape (reference symbol a-2) of the substrate in the track direction when no blank period is provided (blank period 0). ) Shows a cross-sectional shape (reference symbol b-1) and a planar shape (reference symbol b-2) in the track direction of the substrate in the blank period 0.2T, and FIG. 12C shows the blank period 0.3T. A cross-sectional shape (reference symbol c-1) and a planar shape (reference symbol c-2) of the substrate in the track direction are shown. From these figures, the following can be understood regarding the relationship between the blank period and the pre-pit size. When the blank period is not provided or the blank period is too short, for example, as shown in FIG. 12A, the pre-pit size is increased, and the space size is decreased accordingly. On the other hand, for example, as shown in FIG. 12C, if the blank period is too large, the pre-pit size is reduced, and the space size is increased accordingly. In this embodiment, as shown in FIG. 12 (b), when the blank period is 0.2T, the size of the 3T pre-pit and the size of the 3T space are almost equal, and the desired pre-pit size and space size are set. I was able to get it.

  Next, the cross-sectional shape and the planar shape in the track direction in the optical information recording medium in which the dye recording film is applied with a film thickness of 200 nm on the preformat pattern forming surfaces of the above three types of substrates are shown in FIG. -It shows in FIG.13 (c). FIG. 13A shows the cross-sectional shape (reference symbol a′-1) and planar shape (reference symbol a′-2) in the track direction of the optical information recording medium when no blank period is provided (blank period 0). FIG. 13B shows the cross-sectional shape (reference symbol b′-1) and planar shape (reference symbol b′-2) in the track direction of the optical information recording medium in the case of the blank period 0.2T. c) shows a cross-sectional shape (reference symbol c′-1) and a planar shape (reference symbol c′-2) in the track direction of the optical information recording medium in the case of the blank period 0.3T. FIG. 14 shows the cross-sectional shape (reference symbol a ″ -1) and planar shape (reference symbol a ″ -2) in the direction orthogonal to the track direction of the optical information recording medium in the blank period 0.2T. . These cross-sectional shapes and planar shapes were measured using an atomic force microscope in the same manner as described above. As shown in FIGS. 13A to 13C, a recess corresponding to the shape of the in-groove pit formed on the substrate is formed on the surface of the recording film. When the blank period is not provided or the blank period is too short, for example, as shown in FIG. 13A, the prepit size becomes large, and the space size becomes small according to the increased length of the prepit. On the other hand, as shown in FIG. 13C, if the blank period is excessively increased, the prepit size is decreased, and the space size is increased in accordance with the reduced length of the prepit. In the present embodiment, as shown in FIG. 13B, when the blank period is 0.2T, the size of the 3T pre-pit and the size of the 3T space are substantially equal. Further, in this case, as shown in FIG. 14, depressions corresponding to the depths of the in-groove pits and grooves formed on the substrate are formed on the surface of the recording film. Due to the difference in the depth of the recess, the in-groove pit and the groove can be optically identified.

  FIGS. 15A to 15C show changes in the modulation degree, jitter, and radial push-pull in the 3T signal recording section when the blank period is variously changed. FIG. 16A shows a change in modulation degree, a change in jitter, and a radial with respect to the blank period when an in-groove pit having a medium size (the radial width of the optical information recording medium is about 330 nm to 360 nm) is formed. The push-pull changes are summarized. Further, FIG. 16B shows a relationship between the duty ratio and the change in the modulation degree, the change in jitter, the change in radial push-pull in FIG. Here, the duty ratio refers to a ratio of actual lengths of in-groove pits and spaces (grooves) adjusted to have the same length. The duty ratio is expressed as a ratio of the actual space length to the total length of the in-groove pit and the space. In these drawings, the pit size is an optical information recording in which in-groove pits having a large size (the width in the radial direction of the optical information recording medium is 360 nm or more) are formed by irradiating high-intensity laser light during exposure. The medium data is the data of the optical information recording medium in which the medium-sized in-groove pits are formed by irradiating the medium intensity laser beam during the exposure in the pit, and the small pit is the low intensity laser beam in the exposure. The data of the optical information recording medium in which in-groove pits having a small size (the width in the radial direction of the optical information recording medium is 330 nm or less) are formed by irradiating the light. As described above, as described above, a dye layer having a film thickness of 200 nm was formed on each of the three types of substrates by spin coating, and then, in the same manner as in Example 1, a 100 nm film was formed on the dye layer. An optical information recording medium was used in which an Ag reflective layer having a film thickness was formed by sputtering, and a dummy substrate was bonded to the Ag reflective layer via an ultraviolet curable resin.

  As shown in FIG. 15A, the modulation degree of the signal read from the optical information recording medium differs in the blank period when the modulation degree is maximum depending on the pit size. Further, as shown in FIG. 15B, the jitter of the signal read from the optical information recording medium differs in the blank period when the jitter is minimized depending on the pit size. Furthermore, the radial push-pull detected from the optical information recording medium decreases as the blank period increases as shown in FIG. For example, when the pit size is medium, as shown in FIG. 16A, when the blank period is 0.2T, the modulation degree is maximum and the jitter is minimum, and a sufficiently high radial push-pull is obtained. be able to. On the other hand, when the pit size is large, the maximum degree of modulation can be obtained when the blank period is set to 0.4 T, but the jitter becomes large and is not optimal. On the other hand, when the pit size is small, the jitter can be reduced when the blank period is set to 0. However, the modulation degree also decreases with this, so it is not optimal. Therefore, when forming a 3T in-groove pit, it is optimal to set the pit size of the in-groove pit to a medium size and the blank period to 0.2T. In addition, the duty ratio at this time is approximately 0.5 as shown in FIG. 16B, and the in-groove pit and the space adjusted to have the same length in the track direction are actually substantially the same length. It can be seen that it is formed. Since the optimum blank period varies depending on the pit length of the in-groove pit to be formed, the optimum blank period can be obtained for each pit length by the same method as described above.

  Next, a second embodiment of the optical information recording medium of the present invention will be described with reference to FIGS. In the optical information recording medium of the present embodiment, as shown in FIG. 17, the preformat pattern forming area is composed of a media information recording area 170b for recording media information and a user recording area 170c for recording user information. Other than that, the configuration was the same as in Example 1. The media information recording area 170b is formed by a groove having in-groove pits, and is formed in a radius range of 23.9 mm to 24 mm with respect to the center AX ′. On the other hand, the user recording area 170c is formed only by a groove, and is formed in a radius range of 21 mm to 23.9 mm and a radius range of 24 mm to 58 mm with respect to the center AX ′. Note that the groove depth in the user recording area 170c is the same as the groove depth in the portion where the in-groove pit is not formed in the media information recording area 170b.

  FIG. 18 shows a schematic top view of the media information recording area 170b of the optical information recording medium in this embodiment. FIGS. 19A and 19B are a cross-sectional view taken along line CC and a cross-sectional view taken along line DD in FIG. As shown in FIG. 19A, the optical information recording medium in the present embodiment has a recording layer 2 ′, a reflective layer 3 ′, a protective layer 4 ′, and a cover layer 5 sequentially on the preformat pattern forming surface of the substrate 1 ′. 'Is formed. With respect to this optical information recording medium, the maximum depth of the recording layer in the groove 182 (from the interface between the recording layer and the reflective layer on the land surface of the substrate from the interface of the recording layer and the reflective layer) using a scanning probe microscope manufactured by Digital Instruments. Depth of recording layer to interface with layer) Tg and maximum depth of recording layer in in-groove pit 183 (recording layer in in-groove pit from interface between recording layer and reflection layer on land surface of substrate) The recording layer recess depth Tp to the interface with the reflective layer was measured. The recording layer maximum depression depth Tg in the groove 182 was about 100 nm, and the recording layer maximum depression depth Tp in the in-groove pit 183 was about 170 nm. Accordingly, the ratio Tp / Tg = 1.70 of the maximum recording layer recess depth Tg in the groove 182 and the maximum recording layer recess depth Tp in the in-groove pit 183 is obtained. Since the depth dg of the groove 182 is 170 nm and the depth dp of the in-groove pit 183 is 250 nm, the ratio dp / dg = 1.47, which indicates that the relationship dp / dg <Tp / Tg is satisfied. It can also be seen that 1.15 <(Tp / Tg) / (dp / dg).

  Further, this optical information recording medium was mounted on a drive device equipped with an optical pickup that generates laser light having a wavelength of 650 nm, and media information recorded in the media information recording area by the in-groove pit method was reproduced. At this time, the signal modulation degree of the reproduction signal was 61% and the jitter was 7.2%, and it was found that the recording and reproduction characteristics were practically sufficient.

[Modification 1]
A modification of the second embodiment will be described with reference to FIG. As shown in FIG. 20, the optical information recording medium of this modification is formed with a reflective layer 3 ″, a recording layer 2 ″, a protective layer 4 ″, and a cover layer 5 ″ in this order on the preformat forming surface of the substrate 1 ″. The information recording / reproducing of the optical information recording medium is performed by irradiating the recording / reproducing laser light not from the substrate 1 ″ side but from the cover layer 5 ″ side. The bottom surface 201a of the groove 201 and the bottom surface 202a of the in-groove pit 202 are formed flat, and the ratio of the groove depth dg ′ to the in-groove pit depth dp ′ in the substrate 1 ″ is the maximum recording layer in the groove 201 portion. Depression depth (recording layer depression depth from the interface between the recording layer and the protective layer on the land surface of the substrate to the interface between the recording layer and the protective layer in the groove) Tg ′ and the in-groove pit 20 Recording layer maximum recess depth in the portion (recording layer recess depth from the interface between the recording layer and the protective layer on the land surface of the substrate to the interface between the recording layer and the protective layer in the in-groove pit) Tp ′ By satisfying the condition of dp ′ / dg ′ <Tp ′ / Tg ′ with respect to the ratio, the same effect as in Example 2 can be obtained. The protective layer 4 ″ is provided to prevent the recording layer 2 ″ from being deteriorated, and a metal material such as silver or a silver alloy or an inorganic dielectric material such as SiN is sputtered to a thickness of 1 nm to 10 nm. It can be formed by spin-coating an aqueous solution of 4-morpholine-2,5-dibutoxydiazonium trifluoromethanesulfate and polyvinylpyrrolidone. At this time, the film thickness of the protective layer 4 ″ is preferably about 100 nm to 1 μm. The cover layer 5 ″ protects the recording layer 2 ″ from mechanical impact and chemical change, and the surface is A plastic substrate similar to the flat substrate 1 ″ can be attached via an ultraviolet curable resin or the like.

  In the above embodiment, the photoresist formed on the master was exposed by irradiating laser light continuously modulated using two levels of exposure intensity at the pit level and groove level. A pattern corresponding to the groove may be exposed by irradiating a laser beam having an exposure intensity of the groove level, and then a pattern corresponding to the groove and the in-groove pit may be exposed by irradiating a laser beam having an exposure intensity of the pit level. In addition, although the exposure intensity (third exposure intensity) in the blank period is set to zero, the intensity is set to 1/2, 1/3, 1/4, etc. of the intensity (first exposure intensity) when the groove is exposed. obtain.

  In the above embodiment, RIE is used as the etching means for the glass master, but other physical or chemical etching means may be used. Various etching means can be selected depending on the material of the master used, such as glass or metal.

  In the above embodiment, the coating condition of the dye solution is as follows: coating amount 1 g, substrate rotation speed 100 rpm at the start of coating, retention time 30 seconds at the rotation speed of 100 rpm from the start of coating, rotation speed 800-1000 rpm for shaking off excess solution. Although the holding time is 30 seconds, other coating conditions may be used as long as the coating conditions allow the recording layer to be uniformly formed on the land surface of the substrate with a film thickness of 10 nm to 50 nm.

  In the above embodiment, a single-plate optical information recording medium having a dummy substrate on one side is prepared. However, two substrates each having a recording layer and a reflection layer formed on the preformat pattern forming surface are prepared, and the respective reflections are prepared. A double-side bonded optical information recording medium may be obtained by bonding the surfaces to each other via an adhesive layer made of UV resin.

  According to the present invention, by providing a blank period during exposure of the master, it is possible to prevent redundancy for the spot diameter of the laser light in the in-groove pits. In addition, since the blank period is set based on the modulation degree, jitter, and radial push-pull value of the in-groove pit reproduction signal detected from the optical information recording medium, the optical information having good recording / reproduction characteristics and tracking characteristics. A recording medium can be manufactured.

  In the optical information recording medium of the present invention, a media information recording area in which media information is recorded in advance using in-groove pits on the preformat forming surface of the substrate of the optical information recording medium, and the user records information. Since there is a user recording area to perform, there is no need to write media information one after another on a recording layer of the optical information recording medium using a dedicated recording device, and the manufacturing process of the optical information recording medium is simplified. As a result, the manufacturing cost of the optical information recording medium can be reduced.

  Furthermore, in the present invention, by forming a recording layer containing an organic dye on a groove having a flat bottom surface and an in-groove pit, unlike the case of recording media information with a wide and narrow groove, The difference between the height position of the recording layer and the height position of the recording layer in the in-groove pit portion can be increased. In addition, the depth of the dents in the recording layer can be made equal regardless of the difference in the track direction length of the in-groove pits. As a result, information such as media information recorded using the in-groove pits can be read with a high degree of modulation and low jitter. Further, since information is recorded using in-groove pits instead of wide grooves, the track pitch can be narrowed, and the recording capacity can be increased.

  Even if the ratio dp / dg between the in-groove pit depth dp and the groove depth dg is not formed to a value that can provide a desired signal modulation factor and radial push-pull signal, the depth of the recording layer recess in the in-groove pit portion Since the recording layer containing the organic dye is formed on the substrate so that the depth Tp and the recording layer recess depth Tg of the groove portion satisfy the relationship dp / dg <Tp / Tg, it is sufficient for reproducing the recording signal. An optical path length difference can be obtained. Therefore, since the in-groove pit depth dp can be shallow with respect to the groove depth dg of the substrate, the master can be easily cut and the substrate can be formed. Thereby, the manufacturing cost of the optical information recording medium can be reduced.

FIG. 1 is a plan view of an optical information recording medium according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the optical information recording medium in the embodiment of the present invention. FIG. 3A is a plan view of the substrate in the embodiment of the present invention, FIG. 3B is a cross-sectional view taken along the line AA of FIG. 3A, and FIG. FIG. 4 is a cross-sectional view taken along line BB in FIG. FIG. 4 is a cross-sectional view of an optical information recording medium according to another embodiment of the present invention. FIG. 5A to FIG. 5C are diagrams for explaining a master disc manufacturing method used for manufacturing an optical information recording medium in Embodiment 1 of the present invention. FIG. 6A is a diagram showing the change over time of the exposure intensity of the laser beam used for the master exposure in Example 1, and FIG. 6B shows the dimensional relationship between the corresponding in-groove pit formation portion and the groove formation portion. FIG. FIG. 7A to FIG. 7C are diagrams for explaining a method of manufacturing a master in the first embodiment. FIG. 8A and FIG. 8B are diagrams for explaining a method of manufacturing a master in the first embodiment. FIG. 9 is a schematic cross-sectional view of the stamper manufactured in Example 1. FIG. 10 is a schematic perspective view of the pattern forming surface of the substrate obtained in Example 1. FIG. FIG. 11 is a schematic cross-sectional view of an in-groove pit region of the optical information recording medium obtained in Example 1. 12 (a) to 12 (c) show the cross-sectional shape and the planar shape in the track direction of the 3T signal recording unit in each substrate manufactured using three types of masters cut by changing the blank period. 12 (a) shows the case of the blank period 0T, FIG. 12 (b) shows the case of the blank period 0.2T, and FIG. 12 (c) shows the case of the blank period 0.3T. Yes. FIGS. 13 (a) to 13 (c) show a 200 nm thick dye recording film on the preformat pattern forming surface of each substrate produced using three types of masters cut by varying the blank period. FIGS. 13A and 13B show a cross-sectional shape and a planar shape in the track direction in an optical information recording medium coated with a thickness. FIG. 13A shows a case where there is no blank period, and FIG. 13B shows a case where the blank period is 0.2T. FIG. 13C shows a case where the blank period is 0.3T. FIG. 14 is a diagram showing a cross-sectional shape and a planar shape of the optical information recording medium in a direction orthogonal to the track direction in the blank period 0.2T. FIGS. 15A to 15C are diagrams respectively showing the modulation degree, jitter change, and radial push-pull change in the 3T signal recording section when the blank period is variously changed. FIG. 16A is a diagram showing a change in modulation degree, a change in jitter, and a change in radial push-pull with respect to the blank period when a medium-sized in-groove pit is formed, and FIG. It is the figure which showed the relationship between the change of the modulation degree in FIG. 16A, the change of a jitter, the change of radial push pull, and a duty ratio. FIG. 17 is a plan view of an optical information recording medium in Embodiment 2 of the present invention. FIG. 18 is a schematic top view of the in-groove pit area of the optical information recording medium according to the second embodiment. 19A is a cross-sectional view taken along the line CC in FIG. 18, and FIG. 19B is a cross-sectional view taken along the line DD in FIG. FIG. 20 is a schematic cross-sectional view of the in-groove pit area of the optical information recording medium in Modification 1 of the present invention. FIG. 21A is a schematic top view of an in-groove pit region of a conventional optical information recording medium substrate having in-groove pits, and FIG. 21B is A′-A ′ in FIG. FIG. 21C is a cross-sectional view taken along line B′-B ′ of FIG. FIG. 22A is a diagram showing a change over time in the exposure intensity of laser light used for conventional master exposure, and FIG. 22B shows the dimensional relationship between the corresponding in-groove pit formation portion and groove formation portion. FIG. FIG. 23 is a diagram showing a groove and pre-pit pattern employed in a conventional DVD-R or the like. FIG. 24 is a diagram showing a cross-sectional shape of a conventional in-groove pit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer 3 Reflective layer 4 Protective layer 5 Cover layer 8 Groove 9 In-groove pit 10,110 Optical information recording medium 50 Master disc cutting device 51 Glass master 52 Photoresist 91 Stamper BE Blank period

Claims (7)

A substrate formed with a land, a groove having a flat bottom surface and an in-groove pit having a flat bottom surface on one surface; a recording layer containing an organic dye formed on the one surface of the substrate; An optical information recording medium having a reflective layer formed on a recording layer,
The depth from the land surface of the substrate to the bottom surface of the groove is represented by dg, the depth from the land surface of the substrate to the bottom surface of the in-groove pit is represented by dp, and the recording layer and the reflective layer on the land surface The depression depth of the recording layer from the interface to the interface between the recording layer and the reflective layer in the groove is represented by Tg, and the recording layer in the in-groove pit from the interface between the recording layer and the reflective layer on the land surface An optical information recording medium characterized in that dp / dg <Tp / Tg, where Tp is the depth of depression of the recording layer to the interface with the reflective layer. The ratio Tp / Tg of the depth Tg of the recording layer in the groove and the depth Tp of the recording layer in the in-groove pit satisfies 1.6 ≦ Tp / Tg ≦ 2.0. Item 4. The optical information recording medium according to Item 1. When the wavelength of light used for recording or reproduction of the optical information recording medium is represented by λ and the refractive index of the substrate is represented by n, the depth dg to the bottom surface of the groove is dg> λ / 4n. The optical information recording medium according to claim 1 or 2, characterized in that: A substrate having a land on one surface, a groove having a flat bottom surface and an in-groove pit having a flat bottom surface, a reflective layer formed on the one surface of the substrate, and formed on the reflective layer An optical information recording medium comprising a recording layer containing the prepared organic dye, a protective layer formed on the recording layer, and a cover layer formed on the protective layer,
The depth from the land surface of the substrate to the bottom surface of the groove is represented by dg, the depth from the land surface of the substrate to the bottom surface of the in-groove pit is represented by dp, and the recording layer and the protective layer on the land surface The depression depth of the recording layer from the interface with the recording layer to the interface between the recording layer and the protective layer in the groove is represented by Tg ′, and the recording layer at the in-groove pit from the interface between the recording layer and the protective layer on the land surface An optical information recording medium characterized in that dp / dg <Tp ′ / Tg ′, where Tp ′ represents the depth of depression of the recording layer up to the interface between the protective layer and the protective layer. The ratio Tp ′ / Tg ′ between the depth Tg of the recording layer in the groove and the depth Tp of the recording layer in the in-groove pit is 1.6 ≦ Tp ′ / Tg ′ ≦ 2.0. 5. The optical information recording medium according to claim 4, wherein Depth dg to the bottom surface of the groove is dg> λ / 4n, where λ represents the wavelength of light used for recording or reproduction of the optical information recording medium and n represents the refractive index of the cover layer. The optical information recording medium according to claim 4, wherein: The ratio dp / dg of the depth dg to the bottom surface of the groove and the depth dp to the bottom surface of the in-groove pit is 1.4 ≦ dp / dg ≦ 1.7. The optical information recording medium as described in any one of -6.

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