HK1059496B - Optical information recording medium and method for producing the same - Google Patents

Description

Optical information recording medium and method for manufacturing the same

Technical Field

The invention relates to an optical information recording medium and its manufacturing method, and the stamper for manufacturing the substrate of the optical information recording medium and its manufacturing method; in particular, the present invention relates to an optical information recording medium in which media information such as information for a manufacturer and copyright protection measures is recorded in tracks (グル - プ, group) in the form of prepit (プリピツと, prepit), a method of manufacturing the same, a stamper for manufacturing a substrate, and a method of manufacturing the same.

Background

In recent years, DVDs (digital versatile discs) having a recording capacity several times that of CDs (コンパクトデイスク, compact discs) have been widely used as recording media for information such as images and sounds. Further, DVDs such as DVD-R digital high-quality video recording (complementary recording type versatile disc) in which information can be recorded only once by a user and DVD-RW (rewritable versatile disc) in which information can be rewritten are commercialized and are widely used as large-capacity information recording media in the future.

In the DVD-R, manufacturer information of an optical disc, information for copyright protection and countermeasure, and fixed information (hereinafter, referred to as media information) such as an output of a laser beam for recording and reproducing information of the optical disc are generally recorded on the optical disc in advance. These media information are recorded by irradiating light or the like with a recording device to deform the recording layer at the final stage of the optical disk manufacturing process.

In contrast, Japanese patent laid-open Nos. 2000-21024, 2001-67733 and 2002-216364 disclose recording methods in which information such as media information is recorded in the form of embossed pits (エンボスピツト, emboss pit) (hereinafter referred to as in-track pits, インぐル - ブピツト) in the substrate track in advance in the manufacturing stage of the optical disk substrate, instead of the above-described recording layer. Fig. 21 shows a partial substrate made by this method. Fig. 21A is an enlarged plan view of a part of the substrate, schematically showing a region where in-track pits are formed (hereinafter referred to as an in-track pit region). And FIG. 21B and FIG. 21C are a cross-sectional view taken along line A '-A' and a cross-sectional view taken along line B '-B' of FIG. 21A, respectively. On this substrate, as shown in fig. 21B, a depth dp "from the land surface 211a of the substrate 211 on which the lands and the tracks are formed to the bottom surface (lowermost surface) 217a of the in-track pits 217 is formed deeper than a depth dg" from the land surface 211a to the bottom surface (lowermost surface) 215a of the tracks 215. When an optical information recording medium is manufactured by forming a recording layer and a reflective layer on the pattern forming surface of the substrate 211, the surface heights of the layers formed differ between the portion where the in-track information pit 217 is formed and the portion where the in-track information pit 217 is not formed. By utilizing the difference in depth between the pit portion and the track portion in the track, data such as media information can be recorded in the track.

An optical information recording medium using the substrate was manufactured as follows. A resist having a uniform thickness is formed on the surface of the master, the resist is irradiated with a laser beam of a certain intensity to expose a pattern corresponding to the track, and at the same time, a pattern corresponding to the inner-track information pits is exposed using a laser beam adjusted to a higher level than the exposure intensity of the certain intensity. The pattern corresponding to the track and the pattern corresponding to the inner track information pit may be exposed by changing the exposure intensity of the exposure continuously or by changing the exposure to the pattern corresponding to the inner track information pit after exposing the pattern corresponding to the track once. Then, by developing the exposed master, a desired resist pattern corresponding to the track and the in-track information pits is formed on the master. Then, etching treatment such as RIE is performed on the resist pattern forming surface of the master, and a desired pattern corresponding to the track and the inner-track information pits is formed on the surface of the master. Further, a stamper is produced from the master having the pattern formed on the surface thereof, and the substrate is transferred by using the stamper. An optical information recording medium can be manufactured by forming various layers such as a recording film on a pattern formation surface of a transfer substrate.

However, in the case of exposing the portions corresponding to the inner track information pits by the master exposure method as described above, since exposure is performed for a time T1 corresponding to the information pit length for forming the inner track information pits, as shown in fig. 22A and 22B, exposure is performed only at the portion corresponding to the diameter D of the spot SP2 irradiated on the resist of the master, resulting in an increase in the track direction length L1 of the resist-exposed inner track information pit forming portion 221. Thereby shortening the track direction length L2 of the track pitch 222 provided between the inner-track information pit forming portion 221' adjacent to the partial track direction. Therefore, the jitter of the reproduced signal of the inner track pit read from the optical information recording medium increases.

In an optical information recording medium such as DVD-R, in order to suppress the wobble of a prepit reproduction signal, as shown in fig. 23, a slit 231a is usually provided periodically in a track 231, and another prepit 232 is formed in the slit 231 a. In the case of exposing such a master for manufacturing an optical information recording medium, the exposure amount at the time of exposing the pattern corresponding to the pre-information pits 232 can be adjusted so as to be irrelevant to the exposure amount at the time of exposing the pattern corresponding to the tracks 231. Thus, for example, by reducing the exposure intensity at the time of exposing the prepit forming portion to form small-sized prepits, or by adjusting the time interval between exposures of the prepit forming portion to shorten the predetermined time before and after (the exposure start time and the exposure end time), it is possible to suppress or prevent the prepit length from becoming excessively long.

However, in the case of an optical information recording medium in which inner track pits are formed, the size of the pits is reduced by lowering only the exposure intensity of the inner track pit formation portion at the time of exposure of the original disc, or by shortening the exposure time of the inner track pit formation portions before and after the formation, and in these cases, the resist of the inner track pit formation portion cannot be exposed to the surface of the original disc because the exposure amount at the end in the track direction is insufficient. And thus a desired resist pattern cannot be precisely formed on the master. In the master whose surface is etched by such a resist pattern, as shown in fig. 24, inner-track information pit forming portion 242 has a wall surface 242b facing the track direction, and the inclination angle θ 2 with respect to bottom surface 242a of inner-track information pit forming portion 242 is reduced. Similarly to the master, the substrate of the optical information recording medium manufactured by the master has a reduced inclination angle θ 2 of the inner track information pit surface to the wall surface in the track direction, and thus the modulation degree of the signal reproduced by the inner track information pit is reduced.

In addition, 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 position of the interface between the recording layer and the reflective layer is varied depending on the width of the pattern formed on the substrate. The height position of the interface between the recording layer and the reflective layer in the wide track is lower than that in the narrow track. Therefore, an optical path difference is generated between the optical path of the laser light in the wide track portion and the optical path of the laser light in the narrow track portion. In japanese patent application laid-open No. 2001-351268, a method for reproducing media information using such an optical path difference is disclosed, but the depth of a wide track and the depth of a narrow track formed on a substrate used in this method are the same.

However, in the 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 in the wide portion and the narrow portion of the track, the difference in the optical path length of the laser light required for a sufficient signal modulation degree for reproducing information cannot be obtained. Even if various changes are made to the size ratio of the wide portion to the narrow portion of the optical track, the viscosity of the recording layer material, the substrate rotation driving conditions, and the like, a sufficient optical path difference cannot be obtained. In the case of an optical information recording medium in which information such as medium information is recorded using the wide and narrow portions of the track, it is difficult to narrow the track information pits (トラツクピツチ, track pit), which is disadvantageous in increasing the recording capacity of the optical information recording medium by narrowing the track information pits.

In Japanese unexamined patent publication Hei 8-129780 and Japanese unexamined patent publication Hei 2002-237093, although there are disclosed optical information recording media in which the thickness of a recording layer (dye layer) formed on a substrate is made different by the depths of pits and tracks formed on the surface of the substrate, none of them discloses an optical information recording medium having inner-track pits.

Disclosure of Invention

The invention aims to provide an optical information recording medium having inner track information pits with excellent recording and reproducing characteristics and excellent groove (トラツキンダ) characteristics, a method for manufacturing the same, and a stamper for manufacturing a substrate of the optical information recording medium and a method for manufacturing the same.

According to a first aspect of the present invention, there is provided an optical information recording medium comprising a substrate having a land formed on one surface thereof, a track having a flat bottom surface, and an in-track information pit having a flat bottom surface, a recording layer containing an organic dye formed on the one surface of the substrate, and a reflective layer formed on the recording layer.

The optical information recording medium of the present invention is characterized in that dp/dg < Tp/Tg when dg represents the depth from the land of the substrate to the land of the track, dp represents the depth from the land of the substrate to the land of the inner track information pit, Tg represents the pit depth of the recording layer from the interface between the recording layer and the reflective layer on the land to the interface between the recording layer and the reflective layer in the track, and Tp represents the pit depth of the recording layer from the interface between the recording layer and the reflective layer on the land to the interface between the recording layer and the reflective layer in the inner track information pit.

In the optical information recording medium of the present invention, since the inner track information pit having a flat bottom surface is provided in the track having a flat bottom surface, the difference in position between the height position of the interface between the recording layer and the reflective layer in the track 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 inner track information pit portion can be made larger as compared with the optical information recording medium in which the wide width portion and the narrow width portion are formed in the track. Information recorded in the inner-track information pits can be reproduced with a high modulation degree and low jitter. Further, since the wide portion is not provided in the track, the recording density can be increased by narrowing the track information pits. In the optical information recording medium of the present invention, a ratio dp/dg of a depth (hereinafter, referred to as an inner track information pit depth) dp from a land of a substrate to a bottom surface of an inner track information pit to a depth (hereinafter, referred to as a track depth) dg from a land surface of the substrate to the bottom surface of the track, and a ratio Tp/Tg of a pit depth Tp of a recording layer in the inner track information pit and a pit depth Tg of the recording layer in the track satisfy a relationship of dp/dg < Tp/Tg, thereby forming a recording layer containing an organic dye. Thus, even in the case where the predetermined signal modulation degree and the size required for the radial push-pull signal cannot be obtained at the inner-track pit depth dp and the track depth dg, the optical path length difference between the optical path length of the light ray passing through the track and the optical path length of the light ray passing through the inner-track pit can be increased. Therefore, since the depth dp of the inner-track information pit can be made smaller than the track depth dg, the groove of the master and the substrate can be formed more easily, and the manufacturing cost of the optical information recording medium can be reduced. In particular, 1.15 < (Tp/Tg)/(dp/dg) is preferred.

In the present invention, the ratio Tp/Tg of the recording layer pit depth Tp in the inner track information pit to the recording layer pit depth Tg in the track is: Tp/Tg is more than or equal to 1.6 and less than or equal to 2.0. This allows reproduction of information recorded in the in-track information pits with a high modulation degree and low jitter. The optical information recording medium of the present invention can achieve a modulation degree of 60% or more and suppress jitter to 8% or less, for example, and therefore can achieve practically sufficient reproduction characteristics. When λ denotes a wavelength of light for recording or reproduction of the optical information recording medium and n denotes a refractive index of the substrate, the track depth dg should have dg > λ/4 n. In general, when the optical path length difference between the light transmitted through the light tunnel portion and the light transmitted through the stage portion reaches λ/4n, the light tunnel can be detected with the highest contrast. In an optical information recording medium using an organic dye for a recording layer, since the track portion and the land portion recording layer are laminated differently, the difference in optical path length between the light transmitted through the track portion and the light transmitted through the land portion is usually equal to or less than λ/4n, and therefore the track cannot be detected with a good contrast. In the optical information recording medium of the present invention, since the track depth dg of dg > λ/4n is formed, the optical path length difference between the light beam transmitted through the track portion and the light beam transmitted through the land portion is increased to λ/4n, and it is easy to adjust the lamination condition of the recording layer. The track portion and the land portion can be detected with the highest contrast.

According to a second embodiment of the present invention, there is provided an optical information recording medium comprising a substrate having a land formed on one surface thereof, a track having a flat bottom surface and an inner-track information pit having a flat bottom surface, a reflective layer formed on the one surface of the substrate, 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,

dp/dg < Tp '/Tg' when a depth from a land of the substrate to the track bottom surface is denoted by dg, a depth from the land of the substrate to the inner track information pit bottom surface is denoted by dp, a recording layer pit depth from an interface between a recording layer and a reflective layer on the land to an interface between a recording layer and a protective layer in the track is denoted by Tg ', and a recording layer pit depth from an interface between a recording layer and a protective layer on the land to an interface between a recording layer and a protective layer in the inner track information pit is denoted by Tp'.

The optical information recording medium of the present invention records and reproduces information by receiving light from the cover layer side, but by satisfying the relation dp/dg < Tp '/Tg', the same operational effects as those of the optical information recording medium of the first embodiment can be obtained.

In the present invention, the ratio Tp '/Tg' of the pit depth Tp of the recording layer in the intra-track information pit to the pit depth Tg of the recording layer in the intra-track information pit preferably satisfies 1.6. ltoreq. Tp '/Tg'. ltoreq.2.0. When λ denotes the wavelength of light for recording or reproduction of the optical information recording medium and n denotes the refractive index of the surface layer, the depth dg to the bottom surface of the track is preferably dg > λ/4 n.

In the optical information recording medium of the embodiment, a ratio dp/dg of the inner-track information pit depth dp to the track depth dg preferably satisfies 1.4. ltoreq. dp/dg. ltoreq.1.7. In order to obtain a predetermined signal modulation degree and radial push-pull signal, the ratio of the length of the optical path of the light passing through the track to the optical path of the light passing through the inner-track information pit is preferably in the range of about 1.6 to 2.0. However, in the optical information recording medium of the present invention, since the optical path difference between the optical path in the track and the optical path in the inner track information pit can be enlarged by forming the recording layer with an organic dye, even when the ratio dp/dg of the depth dp of the inner track information pit to the depth dg of the track is less than 1.6 to 2.0, the ratio of the optical path length of the light passing through the track to the optical path length of the light passing through the inner track information pit can be in the range of about 1.6 to 2.0. A predetermined signal modulation degree and a radial push-pull signal can be obtained. But also makes it possible to reproduce the information recorded in the inner-track information pits at a high modulation degree and low jitter.

According to a third aspect of the present invention, there is provided a method of manufacturing an optical information recording medium, comprising: the optical information recording medium has a stage and a track, and a substrate is obtained by injection molding using a stamper having management information formed in advance on an information pit, a coating material recording layer is formed on the substrate by spin coating, and a UV resin layer is formed on the recording layer. The information pits are arranged in the light path, and the depth of the information pits is deeper than that of the light path.

The stamper of the present invention can produce a substrate for an optical information recording medium on which a track and an inner-track information pit satisfying the above-mentioned conditions are formed. The substrate thus obtained can obtain a reproduced signal with good modulation from the inner track information pits.

Drawings

FIG. 1 is a plan view of an optical information recording medium in an embodiment of the present invention;

FIG. 2 is a cross-sectional view of an optical information recording medium in an embodiment of the present invention;

FIG. 3A is a plan view of a substrate, FIG. 3B is a cross-sectional view taken along line A-A of FIG. 3A, and FIG. 3C is a cross-sectional view taken along line B-B of FIG. 3A, according to an embodiment of the present invention;

FIG. 4 is a cross-sectional view of an optical information recording medium according to another embodiment of the present invention;

FIGS. 5A to 5C are explanatory views of the method of manufacturing a master for optical information recording medium manufacture in example 1 of the present invention;

FIG. 6A is a graph showing the change with time of the exposure intensity of the laser for exposing the master in example 1, and FIG. 6B is a graph showing the dimensional relationship between the corresponding inner track information pit-forming part and track-forming part;

FIGS. 7A to 7C are explanatory views of a method of manufacturing a master in example 1;

FIGS. 8A and 8B are explanatory views of a method of manufacturing a master in example 1;

FIG. 9 is a schematic sectional view of a stamper produced in example 1;

FIG. 10 is an isometric view of the patterned surface of the substrate obtained in example 1;

FIG. 11 is a schematic sectional view of an inner track information pit region of an optical information recording medium obtained in example 1;

fig. 12A to 12C are diagrams showing a cross-sectional shape and a plane shape in the track direction of a 3T signal recording portion in each substrate manufactured by using three types of masters grooved under the condition of changing the blank period, and fig. 12A, 12B, and 12C show the case where the blank period is 0T, the blank period is 0.2T, and the blank period is 0.3T, respectively;

FIGS. 13A to 13C are views showing cross-sectional shapes and planar shapes in the track direction of an optical information recording medium in which a dye recording film having a thickness of 200 nm is applied to a pattern forming surface of a predetermined format, each of the substrates being formed by using each of three types of master discs grooved under conditions in which a blank period is changed, and FIGS. 13A, 13B and 13C are views showing the case where the blank period is zero, the blank period is 0.2T and the blank period is 0.3T, respectively;

FIG. 14 is a view showing a cross-sectional shape and a plane shape of the optical information recording medium in a direction orthogonal to a track direction in a case where a blank period is 0.2T;

fig. 15A to 15C are graphs showing a modulation degree, a jitter variation and a radial push-pull variation in a 3T signal recording section in the case where a blank period is variously changed, respectively;

fig. 16A is a graph showing changes in modulation degree, jitter, and radial push-pull with respect to a blank period, respectively, in the case of forming a middle-sized in-track information pit, and fig. 16B is a graph showing a relationship between the change in modulation degree, jitter, and radial push-pull and a duty ratio in fig. 16A;

FIG. 17 is a plan view of an optical information recording medium in embodiment 2 of the present invention;

FIG. 18 is a plan view showing an inner track information pit area of the optical information recording medium in example 2;

FIG. 19A is a cross-sectional view taken along line C-C of FIG. 18, and FIG. 19B is a cross-sectional view taken along line D-D of FIG. 18;

FIG. 20 is a schematic cross-sectional view of a track information pit area in an optical information recording medium according to modification 1 of the present invention;

FIG. 21A is a schematic sectional view of an inner track information pit region of a conventional substrate for an optical information recording medium having inner track information pits, FIG. 21B is a sectional view taken along line A '-A' in FIG. 21A, and FIG. 21C is a sectional view taken along line B '-B' in FIG. 21;

FIG. 22A is a graph showing the relationship between the exposure intensity of a conventional master exposure laser and the change with time, and FIG. 22B is a graph showing the relationship between the sizes of the corresponding inner track pit formation portions and tracks;

FIG. 23 is a schematic diagram of tracks and pre-pits employed in a conventional DVD-R;

FIG. 24 is a diagram showing a cross-sectional shape of a conventional inner track information pit.

Detailed Description

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

The optical information recording medium 10 of the present invention is formed in a circular disk shape having a center hole 10a with reference to a center AX, as shown in fig. 1. As shown in fig. 1 and 2, the optical information recording medium 10 has a substrate 1 on one surface of which a predetermined pattern 10b such as a track 8 and an in-track information pit 9 is formed, and on the surface, a recording layer 2, a reflective layer 3, and a protective layer 4 are formed in this order.

The substrate 1 may be a plastic substrate molded using an injection molding method, a compression molding method, or an injection compression molding method. Alternatively, a glass substrate manufactured by a 2P method (photosensitive resin method) may be used.

As shown in fig. 3A to 3C, the predetermined format pattern 10b formed on the substrate 1 is composed of inner track information pits 9 for optically reading information such as address information and the like and a track 8 for guiding a light beam for recording and reproducing, and the inner track information pits 9 are formed on the track 8. As shown in fig. 3B, the information such as the address information is formed by arranging inner track information pits 9 and track portions (hereinafter also referred to as track pitches) 8' adjacent to the inner track information pits 9 but not forming the inner track information pits. The length L1 of the inner track information pit 9 and the length L2 of the track pitch 8' can be arbitrarily adjusted to 3T to 11T or 14T, respectively, when the clock period is T. The predetermined pattern 10b may be formed in a spiral shape or a concentric shape with respect to the center AX of the optical information recording medium 10.

The substrate 1 can be manufactured by using a master having the same concave-convex pattern as the predetermined pattern 10b on the surface and a stamper obtained from the master. The master of the present invention is fabricated by the following master grooving method (lithography method). When exposing the resist formed on the master according to the required inner track information pit pattern, exposure should be performed before and after the exposure period of the inner track information pit pattern by setting a period (blank period) during which exposure is performed with an exposure intensity of exposure light lower than the level at the time of exposure of the track pattern. This prevents the inner track information pit pattern from extending in the track direction by a length corresponding to the laser spot diameter. Wherein the blank period should be set based on the modulation degree, jitter, and radial push-pull value of the inner-track pit reproduction signal detected from the optical information recording medium. And developing the exposed master to form a required resist pattern on the master. By etching such as RIE based on such a resist pattern, a desired predetermined format pattern composed of an inner-track information pit pattern and a track pattern can be formed on the surface of the master. The cross-sectional shapes of both the inner track information pit pattern and the track pattern are formed substantially stepwise. A stamper can be obtained by forming a metal layer such as Ni on the pattern forming surface of the master having the predetermined pattern formed by the above-described method by electroforming or the like.

The inner track information pit 9 formed on the substrate 1 thus obtained has a substantially stepped cross-sectional shape including a flat bottom surface 9a and a wall surface 9B rising from the periphery of the bottom surface 9a, as shown in fig. 3B and 3C. The tilt angle θ 1 of inner track information pit 9 to the wall surface 9b in the track direction is 40 degrees or more and 90 degrees or less with respect to bottom surface 9a of inner track information pit 9. The ratio A1/A2 of the shortest inner track information pit length A1 to the shortest track pitch length A2 is 0.8 to 1.2 times the half-depth of the inner track information pit 9, and the ratio h1/h2 of the height h1 from the bottom surface 9a of the inner track information pit 9 to the shortest track pitch 8 'a to the height h2 to the track pitch 8' b other than the shortest track pitch is 0.95 or more and 1.0 or less. On the other hand, as shown in fig. 3C, the cross-sectional shape of the light path 8 is substantially stepped, and the light path is formed by a flat bottom surface 8a and a wall surface 8b rising from the periphery of the bottom surface 8 a. Wherein a depth d2 from the land 1c of the substrate 1 to the bottom surface 8a of the track 8 is shallower than a depth d1 from the land 1c of the substrate 1 to the bottom surface 9a of the inner-track information pit 9. The term "substantially step-like" as used herein means that the bottom surface and the inclined wall surface intersect each other in a straight step-like manner in mathematical terms, and the bottom surface and the inclined wall surface intersect each other in a plurality of arc-like shapes and a plurality of inclined shapes on each surface. The flat bottom surface in the present specification means a surface having a flat portion substantially parallel to the substrate stage and having a width of at least 50nm in each of the substrate radial direction and the track direction.

Then, the recording layer 2 is formed on the substrate 1 using a low melting point alloy, a phase change type recording material, a magneto-optical recording material, an organic dye material, or the like, according to a recording/reproducing method of information in the optical information recording medium. Although fig. 2 shows a recording layer formed of a single layer, the recording layer may be formed of a laminate of films of the same type or different types, if necessary. For example, in the case of an optomagnetic recording medium, the recording layer may be formed by a laminate of a first reinforcing film formed of an inorganic dielectric, a magnetooptical recording film formed of a perpendicular magnetization film, and a second reinforcing film formed of an inorganic dielectric.

The reflective layer 3 formed on the recording layer 2 may be formed of a metal material or an alloy material having a high reflectance to recording/reproducing light such as silver or a silver alloy, aluminum or an aluminum alloy, gold or a gold alloy, titanium or a titanium alloy, or the like. In the case of an optical information recording medium for reproduction, the reflective layer may be formed directly on the predetermined pattern formation surface of the substrate without forming a recording layer.

The protective layer 4 is a layer for protecting the recording layer 2 and the reflective layer 3 from mechanical impact and chemical change, and may be formed of an inorganic dielectric of the same kind or different kind as the inorganic dielectric constituting the reinforcing film, or an organic material such as an ultraviolet-curable resin. As a cover layer on the protective layer 4, a substrate (separator, ダミ — substrate) having a flat surface and made of the same plastic as the substrate 1 may be bonded to the protective layer 4 using an ultraviolet curable resin or the like.

The depth of the inner track information pit and the thickness of the recording layer in the optical information recording medium of the present invention can be determined as follows. When the wavelength of the recording/reproducing light is λ, the thickness of the film can be adjusted so that the difference in optical path length between the light incident from the substrate, passing through the stage, reaching the interface between the recording layer and the reflective layer, reflected by the interface, and then guided to the substrate side through the stage, and the light incident from the substrate, passing through the bottom surface of the inner-track information pit, reaching the interface between the recording layer and the reflective layer, reflected by the interface, and then guided to the substrate side through the bottom surface of the inner-track information pit becomes λ/6 to λ/3. The track depth can be adjusted by adjusting the difference in optical path length between a light beam incident from the substrate through the stage to reach the interface between the recording layer and the reflective layer, reflected by the interface, and guided to the substrate side through the stage, and a light beam incident from the substrate through the bottom surface of the track to reach the interface between the recording layer and the reflective layer, reflected by the interface, and guided to the substrate side through the bottom surface of the track to λ/16 to λ/8, when the wavelength of the recording/reproducing light beam is λ.

In which pits 8 'and 9' corresponding to the surface shapes of the track 8 and the inner-track information pit 9 are formed as shown in fig. 4 by making the interface between the recording layer 2 and the reflective layer 3 uneven due to the kind and thickness of the recording layer 2. In this case, the depths of pits 8 'and 9' are determined in advance by experiments, and the depth d1 of the in-track information pit 9, the depth d2 of the track 8, and the film thickness t of the recording layer 2 are adjusted according to the values so as to satisfy the above-described optical path difference condition.

When the reflective layer 3 is directly formed on the predetermined pattern formation surface of the substrate, for example, in an optical information recording medium for reproduction, when the wavelength of the recording/reproducing light and the refractive index of the substrate are λ and n, respectively, the inner track information pit depth and the track depth to be formed can be λ/6n to λ/3n and λ/16n to λ/8n, respectively.

In the optical information recording medium of the present invention, since the cross-sectional shapes of the inner track information pit and the track are substantially stepped with a flat bottom surface, a stable radial push-pull signal can be obtained as compared with the optical information recording medium having a track with an uneven bottom surface. And the noise of the reproduced signal detected from the inner track pits can be reduced. Therefore, it is possible to realize a high recording density of the optical information recording medium and a high S/N ratio of a reproduced signal.

As described above, since the inner track information pit 9 formed on the substrate of the optical information recording medium has an inclination angle of the wall surface facing the track direction of 40 degrees or more and 90 degrees or less with respect to the bottom surface of the inner track information pit, the ratio of the shortest prepit length to the shortest track pitch length of the inner track information pit is 0.8 to 1.2 times the half depth of the inner track information pit, and the ratio of the height from the bottom surface of the inner track information pit to the shortest track pitch to the height from the bottom surface of the inner track information pit to the track pitch other than the shortest track pitch is 0.95 to 1.0, a reproduced signal of the inner track information pit can be obtained with a high modulation degree and a low jitter.

In another embodiment of the present invention, a medium information recording region in which medium information is recorded in advance by inner track pits and a user recording region in which user information is recorded are provided on a predetermined format pattern forming surface of an optical information recording medium substrate. Thus, it is not necessary to record media information one by one on the recording layer of the optical information recording medium by a dedicated recording device, and therefore, the manufacturing process of the optical information recording medium can be simplified and the manufacturing cost of the optical information recording medium can be reduced.

The predetermined pattern formed in the medium information recording region is constituted by a track having a substantially step-like flat bottom surface and inner track information pits having a substantially step-like flat bottom surface provided in the track, as in the above-described embodiment. When the clock period is T, the length of the inner track information pit can be arbitrarily adjusted to 3T to 11T or 14T, and the medium information can be recorded by the arrangement of a plurality of inner track information pits having different lengths.

As shown in fig. 19A, the depth from the stage 1 'a of the substrate 1' to the bottom surface 182a of the track 182, i.e., the track depth dg, can be formed to a depth slightly deeper than λ/4n when the laser wavelength used for information recording and reproduction is λ and the refractive index of the substrate is n. Further, the depth from land 1 'a of substrate 1' to bottom surface 183a of inner track information pit 183, i.e., inner track information pit depth dp, may be formed deeper than track depth dg. For ease of manufacture of the substrate 1', the ratio dp/dg of the inner-track information pit depth dp to the track depth dg may be in the range of 1.4 dp/dg 1.7.

As shown in fig. 20, in the case of an optical information recording medium in which information is recorded and reproduced by irradiating laser light from the surface layer 5 "side without irradiating the substrate 1", the depth from the stage 1 "a of the substrate 1" to the bottom surface 201a of the track 201, i.e., the track depth dg, can be set to a depth slightly deeper than λ/4n when the wavelength of laser light used for information recording and reproduction is λ and the refractive index of the spacer 5 "is n. Also, the depth from land 1 "a of substrate 1" to bottom surface 202a of inner track information pit 202, i.e., inner track information pit depth dp 'may be formed deeper than track depth dg'. For ease of manufacture of the substrate 1 ', the ratio dp'/dg 'of the inner track information pit depth dp' to the track depth dg 'may be in the range of 1.4. ltoreq. dp'/dg.ltoreq.1.7.

In the optical information recording medium of the present embodiment, the predetermined format pattern constituting the user recording region may be constituted by a substantially stepped groove-shaped track having a flat bottom surface and a substantially stepped groove-shaped inner track information pit having a flat bottom surface provided in the track, and a wobble fm information pit (ウオブルピツト, flexible pit) for controlling a groove may be provided without providing a track, similarly to the predetermined format pattern constituting the medium information recording region.

The recording layer 2 'shown in fig. 19A is formed by spin-coating a dye dissolved in an organic solvent on a predetermined-format pattern formation surface of the substrate 1'. The surface of the recording layer 2' is not smooth by an external force during spin coating, and a concave-convex shape corresponding to the track depth dg and the depth dp of the information pit in the track is formed. The recording layer 2 ' may be formed such that a recording layer pit depth (recording layer maximum pit depth) Tp from the interface between the recording layer 2 ' and the reflective layer 3 ' on the land 1 ' a of the substrate 1 ' to the interface between the recording layer 2 ' and the reflective layer 3 ' in the track 182 to the interface between the recording layer 2 ' and the reflective layer 3 ' in the inner track information pit 183 becomes larger than a recording layer pit depth (recording layer maximum pit depth) Tg from the interface between the recording layer 2 ' and the reflective layer 3 ' on the land 1 ' a of the substrate 1 '. And the ratio Tp/Tg of the recording layer maximum pit depth Tp to the recording layer maximum pit depth Tg becomes larger than the ratio dp/dg of the inner-track information pit depth dp and the track depth dg. Thus, even when the ratio dp/dg is not formed so that a good signal modulation degree and radial push-pull signal value can be obtained, the optical path difference (approximately 2 × (Tp-Tg)) between the optical path of the laser light in the track and the optical path of the laser light in the in-track information pit can be increased. To reproduce media information with a high signal modulation degree and low jitter, Tp/Tg may be made to be in the range of 1.6. ltoreq. Tp/Tg. ltoreq.2.0. Also for all the inner track information pits of different lengths, the recording layer maximum pit depth TP can be adjusted to the same level while keeping the TP/Tg value within the range. As the organic dye material, for example, a known organic dye suitable for a complementary recording type optical information recording medium such as an azo dye and a cyanine dye can be used.

Example 1

The method for manufacturing an optical information recording medium according to the first embodiment of the present invention will be described below with reference to fig. 5 to 16.

The optical information recording medium can be manufactured by the following steps: the method includes a master grooving step of forming a desired pattern on a master surface, a stamper manufacturing step of manufacturing a stamper based on the grooved master, a substrate manufacturing step of copying an optical information recording medium substrate using the manufactured stamper, and a film forming step of forming various films on the copied substrate.

[ methods for producing master and stamper for producing substrate ]

First, a method of manufacturing a master and a stamper for manufacturing a substrate 1 for an optical information recording medium according to the present invention will be described with reference to fig. 5 to 9. 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 resist 52 having a thickness of 200 nm was uniformly applied on one surface 51a of the glass master 51 by spin coating. Then, the glass master 51 on which the resist 52 is formed is mounted on a master notching device (master exposure device) 50 shown in fig. 5C. The master patterning device 50 is mainly composed of a Kr gas laser resonator 53 for resonating a laser beam having a wavelength of 351 nm, an optical modulator 54 including an acousto-optic modulator, a signal source 55 for supplying a modulation signal to the optical modulator 54, a condenser lens 56, and a drive device (not shown) for rotating the glass master. As shown in fig. 5C, the laser LS emitted from the laser resonator 53 of the master notching device 50 is irradiated onto the resist 52 of the glass master 51 through the optical modulator 54 and the condenser lens 56. At this time, the glass original 51 is rotated around the center axis BX of the glass original 51 at a predetermined number of revolutions. Then, the laser LS is moved (in the direction of the arrow AR 1), and the irradiation position of the laser LS on the glass original 51 is moved from the inside to the outside of the glass original 51 along the radial direction of the glass original 51.

As described above, while the laser LS is moved, the exposure intensity of the laser LS irradiated on the glass master 51 is changed by the optical modulator 54. In this embodiment, as shown in fig. 6A, the exposure intensity of the laser light is changed in two steps of high level and low level. When a track forming portion having no inner-track information pit forming portion is formed, the exposure intensity is set at a low level (hereinafter referred to as a track level). When the track forming portion having the inner track pit forming portion is formed, the exposure intensity is set at a high level (hereinafter referred to as a pit level) in the inner track pit forming portion, and is set at a track level with respect to the other track forming portions. Wherein the exposure intensity at the track level is set at 55% in the case where the information pit level is set at 100%. Thus, the resist of the inner-track information pit forming portion is exposed to the interface between the resist and the master, while the resist of the track forming portion is not exposed to the interface between the resist and the master. Further, when the clock period is T, any of the channel pits of 3T to 11T or 14T can be formed in the track direction in each of the inner-track pit forming portions. Wherein the clock period T can be adjusted appropriately according to the regeneration device used.

In the present embodiment, a low level period BE (blank period) is provided in which the exposure intensity of the laser light is temporarily made lower than the track level, and the exposure intensity of the inner track pit forming portion is changed alternately one by one from the exposure intensity at the track level to the exposure intensity at the information pit level or from the exposure intensity at the information pit level to the exposure intensity at the track level as shown in fig. 6A. In this embodiment, the exposure intensity of the laser light in the blank period BE is set to a zero level. By providing the blank period, as shown in fig. 6B, the resist exposure amount in the front end portion 62a and the rear end portion 62B of the inner-track pit forming section 62 becomes equivalent to the radius portion of the laser spot SP1, respectively. This can prevent the inner track information pit from extending by a length corresponding to the radius of the laser spot SP 1. Further, since the resist of the inner track pit-forming portion is exposed to light with sufficient exposure intensity as described above, the disadvantage of insufficient exposure of the resist in the front end portion and the rear end portion of the inner track pit-forming portion can be eliminated, and thus an inner track pit-forming portion with high processing accuracy can be formed in which the wall surface inclination angle between the front end portion and the rear end portion of the inner track pit-forming portion is 40 degrees or more and 90 degrees or less.

The blank period BE can BE set based on three parameters, i.e., the modulation degree, jitter, and radial push-pull of the inner-track pit reproduction signal detected from the optical information recording medium. And the blank period BE can BE changed according to the channel information pit length of the formed inner track information pit. In this embodiment, when exposing the inner track information pit forming portion having the shortest channel information pit length of 3T, the blank period BE is set to 0.2T according to the values of the three parameters. The method for setting the blank period will be described in detail later.

Then, the glass master with the resist exposed to light is removed from the notching device and subjected to a development process. Thus, as shown in fig. 7A, a track forming portion 71 and an inner-track information pit forming portion 72 are formed on the glass master 51. The light path forming portion 71 is formed in a V-shaped groove shape in cross section. In the inner-track pit forming portion 72, the resist 52 is removed from the glass master 51 by development treatment, and then the exposed portion 72a is exposed on the surface 51a of the glass master 51.

Then, as shown in FIG. 7B, using an RIE (reactive ion etching) apparatus not shown in the figure, at C₂F₆The surface of the resist 52 formed on the glass master 51 is etched in a gas atmosphere. CF may also be used₄And C₃F₆Substitution of C by isogas₂F₆. Thus, the inner-track information pit forming portions 72 are each etched to a depth of 90 nm from the surface 51a of the glass master 51. Further, as shown in fig. 7C, in order to expose the surface 51a of the glass master 51 in the light-path forming portion 71, the resist 52 is thinned to a predetermined thickness using an oxygen-induced resist polishing apparatus not shown in the figure. Thus enabling the track section 71The glass original surface 71a is exposed. Next, as shown in FIG. 8A, again at C₂F₆RIE was performed on the resist 52-formed surface of the glass master 51 in a gas atmosphere. Thus, the light-path forming portion 71 is etched to a depth of 170nm from the glass master surface 51 a. While the inner-track information pit-forming portions 72 were also etched to a depth of 260 nm from the glass master surface 51 a. Then, as shown in fig. 8B, the resist 52 on the glass master 51 is removed by a resist polishing device (not shown). Thus, a glass master 51 having a desired concave-convex pattern formed on the surface thereof was obtained.

Using an atomic force microscope (interatomic force microscope), the following were obtained: the inclination angle of the inner track information pit forming part of the glass master facing the wall surface in the track direction, the ratio of the shortest prefabricated information pit length and shortest track gauge length of the half-depth part of the inner track information pit to the height of the bottom surface of the inner track information pit in the shortest track gauge distance to the height of the bottom surface of the inner track information pit in the track gauge distance other than the shortest track gauge are obtained.

The tilt angle of the inner track information pit forming portion facing the wall surface in the track direction in the inner track information pit having a pre-information pit length of 3T is 60 degrees. In the inner track pit forming portion having a pre-pit length other than the pre-pit length, the inclination angles of the wall surfaces of the front end portion and the rear end portion facing the track direction are both formed to be 40 degrees or more and 90 degrees or less.

The shortest pre-pit length formed at half the depth of the inner track pit is 400-420 nm. And the shortest track pitch length is 355-375 nm.

The height to the bottom surface of the inner-track information pit of the shortest track pitch (the distance from the bottom surface of the inner-track information pit of the shortest track pitch to the bottom surface of the track) is formed to be 90 to 85 nm (the distance from the bottom surface of the inner-track information pit of the shortest track pitch to the land is 262 to 258 nm). And the height from the track gauge outside the shortest track gauge to the bottom surface of the inner track information pit is 90-85 nanometers. So that the ratio of the height from the shortest track pitch to the bottom surface of the inner track information pit to the height from the track pitches other than the shortest track pitch to the bottom surface of the inner track information pit is 0.95 to 1.0. This means that the heights of any track pitch to the bottom surface of the inner track information pit are formed at substantially the same height position.

Then, the pattern-formed surface of the glass master is subjected to electroless plating for pretreatment of plating. Further, this plating layer was used as a conductive film, and an Ni layer having a thickness of 0.3 mm was formed by electroforming. Then, the surface of the Ni layer formed on the glass master was polished, and finally, the Ni layer was peeled off from the glass master, thereby obtaining a stamper 91 shown in fig. 9. The stamper 91 has a surface formed with a pattern 92 that is inverse to the asperities formed on the surface of the master. The conductive film in the pre-plating treatment may be formed by a sputtering method or a vapor deposition method. Further, the stamper may be manufactured by adding another step such as bonding a lining material to the stamper.

[ method for producing optical information recording Medium ]

The method of manufacturing the optical information recording medium will be described below with reference to fig. 10 and 11. The stamper is mounted on an existing injection molding apparatus, and the substrate 1 is obtained by injection molding. The substrate 1 was a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm, and as shown in fig. 10, a pattern having the same shape as the concave-convex pattern such as the track forming portion and the inner track information pit forming portion formed on the glass disc was transferred onto one surface of the substrate 1 (the land 7, the track 8, and the inner track information pit 9). The bottom surface of the inner-track information pits formed on this substrate was observed with a Transmission Electron Microscope (TEM). On the bottom surface of the inner track information pit, a flat region having a width of at least 50nm in the substrate radius direction and the track direction is formed. Also, the bottom surface of the light path formed on this substrate was observed with a Transmission Electron Microscope (TEM). It has been ascertained that on the bottom surface of the track there is also a flat area which is at least 50nm wide, in the substrate radial direction and in the track direction, respectively.

An azo dye solution represented by the following chemical formula (1) was applied to the pattern-forming surface of the substrate 1 by spin coating so that the thickness between the tracks, i.e., the mesa portion, became 30 nm. The amount of the solution applied is 1 g, and the substrate is rotated at a rotation speed of 800 to 1000 rpm for 30 seconds after the start of the application at 100 rpm for 30 seconds. Wherein the solvent of azo dye using tetrafluoropropanol as solvent is filtered by a filter to remove impurities when the dye solution is applied. The spin coating of the dye solution was performed from a radius of 21.0 mm toward the outer peripheral portion of the substrate 1 with respect to the rotation center thereof. The substrate 1 coated with the dye material was further dried at 70 ℃ for 1 hour, and then cooled at room temperature for 1 hour. This forms the recording layer 2 on the substrate 1 (see fig. 11). In which the surface of the recording layer 2 is not smooth due to an external force such as a centrifugal force applied during spin coating, and has a concave-convex shape corresponding to the depth of the track and the depth of the inner track information pit.

Further, as shown in FIG. 11, an Ag alloy was formed as a reflective layer 3 on the recording layer 2 by sputtering to a thickness of 100 nm. Next, an ultraviolet curable resin 4 was applied on the reflective layer 3 by a spin coating method to a thickness of 10 μm, and a polycarbonate substrate (spacer) 5 having a thickness of 0.6 mm as the substrate 1 was placed thereon so as to be aligned with the center. In this state, the substrate 1 on which each layer is formed is irradiated with ultraviolet rays to cure the ultraviolet curable resin, and the substrate 1 on which each layer is formed is bonded to the separator 5 by this method. Thus, the optical information recording medium 110 was obtained.

[ method for setting blank period ]

The method for setting the blank period will be described below with reference to fig. 12 to 16. Fig. 12A to 12C show the cross-sectional shape and the plane shape of the 3T signal recording portion (prepit length 3T and track pitch length 3T) in the track direction in each substrate produced using three types of master discs on which grooving is performed under the condition that the blank period is changed. Wherein the measurement of the cross-sectional shapes is performed by an atomic force microscope. Fig. 12A, 12B, and 12C show: the cross-sectional shape (reference symbol A-1) and the planar shape (reference symbol A-2) of the substrate in the track direction are set when the blank period (blank period is zero), the cross-sectional shape (reference symbol B-1) and the planar shape (reference symbol B-2) of the substrate in the track direction are set when the blank period is 0.2T, and the cross-sectional shape (reference symbol C-1) and the planar shape (reference symbol C-2) of the substrate in the track direction are set when the blank period is 0.3T. These figures illustrate the relationship between the blank period and the pre-pit size as follows. When the blank period is not set or is too small, the size of the prepit pit increases and the track pitch size of the portion decreases as shown in fig. 12A, for example. In contrast, if the blank period is too large, as shown in fig. 12C, for example, the pre-pit size decreases and the track pitch size of the portion increases. In the present embodiment, as shown in fig. 12B, when the blank period is set to 0.2T, the 3T prepit pit size and the 3T track pitch size are substantially equal to each other, and the desired prepit pit size and track pitch size can be obtained.

Further, fig. 13A to 13C show the cross-sectional shape and the planar shape of the optical information recording medium along the track direction, in which the dye recording film of 200 nm thickness is applied to the predetermined pattern formation surface of each of the three substrates. Fig. 13A, 13B, and 13C show: the cross-sectional shape (reference symbol A '-1) and the plane shape (reference symbol A' -2) of the optical information recording medium in the track direction in the case where the blank period is not set (zero blank period), the cross-sectional shape (reference symbol B '-1) and the plane shape (reference symbol B' -2) of the optical information recording medium in the track direction in the case where the blank period is 0.2T, and the cross-sectional shape (reference symbol C '-1) and the plane shape (reference symbol C' -2) of the optical information recording medium in the track direction in the case where the blank period is 0.3T are provided. FIG. 14 shows the cross-sectional shape (reference character A '-1) and the plan shape (reference character A' -2) of the optical information recording medium in the direction perpendicular to the track direction in the case where the blank period is 0.2T. Wherein the measurement of these cross-sectional shapes is carried out by atomic force microscopy as described above. As shown in fig. 13A to 13C, pits corresponding to the shape of the inner track information pits formed on the substrate may be formed on the surface of the recording film. When the blank period is not set or is too small, the size of the prepit pit increases and the track pitch size decreases according to the increased length of the prepit pit, as shown in fig. 13A, for example. In contrast, as shown in fig. 13C, if the blank period is too large, the size of the prepit is reduced, and the track pitch size is increased according to the reduced length of the prepit. In the present embodiment, as shown in fig. 13B, when the blank period is set to 0.2T, the 3T prepit pit size and the 3T track pitch size become substantially equal. Also in this case, as shown in fig. 14, pits corresponding to the respective depths of the inner-track information pits and the tracks formed on the substrate may be formed on the surface of the recording film. The inner-track information pits and tracks can be optically recognized using such a difference in pit depth.

Fig. 15A to 15C show changes in the modulation degree of the 3T signal recording portion, changes in the jitter, and changes in the radial push-pull, respectively, in the case where the blank period is variously changed. FIG. 16A shows a relationship between a change in modulation, a change in jitter, and a change in radial push-pull and a blank period in forming a track information pit of medium size (a width of 330 to 360 nm in the radial direction of an optical information recording medium). Further, fig. 16B shows the relationship between the change in modulation degree, the change in jitter, and the change in radial push-pull in fig. 16A and the duty ratio. The duty ratio here means a ratio of an inner track information pit adjusted to the same length to an actual length of a track pitch (track). The duty ratio is expressed by the ratio of the actual track pitch length to the total length of the track information pit and the track pitch. In these figures, the large pits indicate data of an optical information recording medium on which large-size (a width in the radial direction of the optical information recording medium is larger than 360 nm) inner-track pits are formed by irradiation of a high-intensity laser beam during exposure, the medium pits indicate data of an optical information recording medium on which medium-size inner-track pits are formed by irradiation of a medium-intensity laser beam during exposure, and the small pits indicate data of an optical information recording medium on which small-size (a width in the radial direction of the optical information recording medium is smaller than 330 nm) inner-track pits are formed by irradiation of a low-intensity laser beam during exposure. As a sample used therein, the same one as described above was used, that is, a dye layer having a film thickness of 200 nm was formed on each of the three substrates by a spin coating method, and then an Ag reflective layer having a film thickness of 100 nm was formed on the dye layer by a sputtering method in the same manner as in example 1, and further a spacer was bonded to the optical information recording medium on the Ag reflective layer via an ultraviolet curable resin.

As shown in fig. 15A, the modulation degree of a signal read from an optical information recording medium varies depending on the size of a pit and the blank period when the modulation degree is maximized. Further, jitter in the read signal from the optical information recording medium is different depending on the size of the information pit, and the blank period when the jitter is minimized is also different as shown in fig. 15B. Further, the radial push-pull detected from the optical information recording medium decreases as the blank period increases, as shown in fig. 15C. For example, when the information 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 sufficiently high radial push-pull can be obtained. On the other hand, when the pit size is large, if the blank period is 0.4T, the maximum modulation degree can be obtained, but the jitter increases, which is not suitable. In contrast, when the pit size is small, if the blank period is 0, the jitter can be reduced, but this is not suitable because the modulation degree is also reduced. Therefore, when the 3T inner track information pit is formed, it is preferable to set the information pit size of the inner track information pit to the middle size and set the blank period to 0.2T. Also, it is found that the duty ratio at this time is about 0.5 as shown in fig. 16B, and the inner-track information pits and the track pitches adjusted to the same length in the track direction are formed almost the same length as they are in reality. Since the optimum space period varies depending on the pit length of the inner track information pit to be formed, the optimum space period can be obtained for each pit length by the same method as described above.

Example 2

The second embodiment of the optical information recording medium of the present invention will be described below with reference to fig. 17 to 19. The optical information recording medium of the present embodiment has the same configuration as that of embodiment 1, except that the predetermined format pattern forming region is constituted by a medium information recording region 170b in which medium information is recorded and a user information recording region 170c in which user information is recorded, as shown in fig. 17. The medium information recording region 170b is formed by tracks having inner track information pits, and is formed within a radius of 23.9 to 24 mm with respect to the center AX'. On the other hand, the user recording area 170c is formed of tracks only, and is formed within a range of a radius of 21 to 23.9 mm and a range of a radius of 24 to 58 mm with respect to the center AX'. Wherein the track depth in the user recording area 170c is the same as the track depth in the medium information recording area 170b where the inner-track information pit portion is not formed.

Fig. 18 is a schematic plan view showing a medium information recording area 170b of the optical information recording medium according to the present embodiment. And FIGS. 19A and 19B are sectional views showing the cross-sectional lines C-C and D-D in FIG. 18, respectively. In the optical information recording medium of this embodiment, as shown in fig. 19A, a recording layer 2 ', a reflective layer 3 ', a protective layer 4 ' and a cover layer 5 ' are formed in this order on a predetermined pattern formation surface of a substrate 1 '. With respect to this optical information recording medium, the maximum pit depth Tg of the recording layer in the track 182 (the pit depth from the interface between the recording layer and the reflective layer on the stage of the substrate to the recording layer between the recording layer and the interface between the reflective layers in the track) and the maximum pit depth Tp of the recording layer in the inner track information pit 183 (the pit depth from the interface between the recording layer and the reflective layer on the stage of the substrate to the recording layer between the recording layer and the interface between the reflective layers in the inner track information pit) were measured by a scanning electronic probe available from digital instruments. The maximum pit depth Tg of the recording layer in the track 182 is about 100 nm, and the maximum pit depth Tp of the recording layer in the inner-track information pit 183 is about 170 nm. Therefore, the ratio Tp/Tg of the maximum pit depth Tp of the recording layer in the inner track information pit 183 to the maximum pit depth Tg of the recording layer in the track 182 is 1.70. Since the depth dg of the track 182 is 170nm and the depth dp of the inner-track information pit 183 is 250nm, it was found that dp/dg is 1.47 and satisfies the relationship dp/dg < Tp/Tg. But also found 1.15 < (Tp/Tg)/(dp/dg).

This optical information recording medium is mounted on a drive unit equipped with an optical pickup (beam ピツクアツプ) for generating a laser beam having a wavelength of 650 nm, and medium information recorded in the medium information recording region by the inner track information pit method is reproduced. It is found that the signal modulation degree of the reproduced signal at this time is 61% and the jitter is 7.2%, and that the recording and reproducing characteristics are practically sufficient.

Modification example 1

A modification of embodiment 2 will be described with reference to fig. 20. As shown in fig. 20, the optical information recording medium of this variation is an optical information recording medium in which a reflective layer 3 ", a recording layer 2", a protective layer 4 ", and a cover layer 5" are formed in this order on a predetermined format pattern formation surface of a substrate 1 ", and information recording and reproduction of the optical information recording medium is performed so that a recording/reproduction laser beam is not irradiated from the substrate 1" side but from the surface layer 5 "side. With respect to this optical information recording medium, since the relationship of dp '/dg' < Tp '/Tg' is satisfied in the relationship between the bottom surface 201a of the track 201 and the bottom surface 202a of the inner track information pit 202, while the substrate 1 "the ratio dp '/dg' of the inner track information pit depth dp 'to the track depth dg', and the ratio of the maximum pit depth of the recording layer in the track 201 portion (the pit depth from the land of the substrate to the recording layer between the recording layer and the reflective layer interface in the track) Tg 'to the maximum pit depth of the recording layer in the inner track information pit 202 portion (the pit depth from the land of the substrate to the recording layer between the recording layer and the reflective layer interface in the inner track information pit to the recording layer between the recording layer and the reflective layer interface) Tp', the same effect as in embodiment 2 can be obtained. The protective layer 4 'is provided for preventing deterioration of the recording layer 2', and can be obtained by a method of sputtering a metal material such as silver or a silver alloy and an inorganic dielectric material such as SiN to a thickness of 1 to 10nm, or a method of spin-coating an aqueous solution of 4-morpholino-2, 5-dibutoxy azo trifluoromethanesulfonate and polyvinylpyrrolidone. In this case, the thickness of the protective layer 4' is preferably 100 nm to 1 μm. The cover layer 5 "is provided to prevent the recording layer 2" from mechanical shock and chemical change, and a plastic substrate similar to the substrate 1 "having a flat surface may be bonded with an ultraviolet curable resin or the like.

In the above-described embodiment, the resist formed on the master is exposed by the laser irradiation method in which the two-stage exposure intensity of the information pit level and the track level is continuously modulated, but the exposure of the pattern corresponding to the track may be started by starting the irradiation of the laser with the track level exposure intensity to the resist, and the exposure of the pattern corresponding to the track and the intra-track information pit may be started by further irradiating the laser with the information pit level exposure intensity. The exposure intensity during the blank period (third exposure intensity) is set to 0, but may be set to 1/2, 1/3, 1/4, etc., which correspond to the intensity during the track exposure (first exposure intensity).

Although RIE was used as the etching means for the glass master in the above embodiment, other physical or chemical etching means may be used. Various etching methods can be selected depending on the material of the master used for glass, metal, or the like.

In the above-mentioned examples, the coating amount of the dye solution was set to 1 g, the number of revolutions of the substrate at the start of coating was set to 100 rpm, the number of revolutions per minute was maintained at 100 rpm for 30 seconds after the start of coating, and the number of revolutions was increased to 800 to 1000 rpm and maintained for 30 seconds in order to throw off the remaining solution, but any other conditions may be employed as long as a recording layer having a film thickness of 10 to 50nm can be uniformly formed on the substrate.

In the above-described embodiment, a single-plate structure optical information recording medium having a spacer on one surface thereof is manufactured, but two substrates each having a recording layer and a reflective layer formed on a predetermined pattern formation surface thereof may be prepared, and the reflective surfaces of the two substrates may be bonded to each other by an adhesive layer formed of a UV resin to manufacture a double-sided adhesive type optical information recording medium.

According to the present invention, by setting the blank period in the exposure of the master, the inner track information pit can be prevented from being extended along the radius of the laser spot. Further, since the blank period is set based on the modulation degree, jitter, and radial push-pull value of the inner-track pit reproduction signal detected from the optical information recording medium, the optical information recording medium having excellent recording/reproducing characteristics and land track characteristics can be manufactured.

In the optical information recording medium of the present invention, since the medium information recording region in which the medium information is recorded in advance by the inner track information pits and the user recording region in which the user information is recorded are provided on the predetermined format pattern forming surface of the optical information recording medium substrate, it is not necessary to record the medium information one by one on the recording layer of the optical information recording medium by using a dedicated recording device afterwards, and therefore, the manufacturing process of the optical information recording medium can be simplified and the manufacturing cost of the optical information recording medium can be reduced.

In the present invention, by forming a recording layer containing an organic dye on a track having a flat bottom surface and an inner track pit, the difference in position between the height of the recording layer in the track portion and the height of the recording layer in the inner track pit portion can be increased, unlike the case of recording medium information by a track width narrowing method. And the pit depths of the recording layers can be made equal despite the fact that the inner-track information pits differ in length in the track direction. Thus, information such as medium information recorded in the inner track information pits can be read out with a high modulation degree and a low jitter. In addition, since information is recorded not in the track width portion but in the inner track information pits, the track information pits can be narrowed to increase the recording capacity.

Even if a ratio dp/dg of an inner-track pit depth dp to a track depth dg is assumed, and a desired signal modulation degree and radial push-pull signal value are not obtained, a recording layer containing an organic dye is formed on a substrate so that a pit depth Tp of the inner-track pit portion recording layer and a pit depth Tg of the track portion recording layer satisfy a relation dp/dg < Tp/Tg, and therefore a sufficient optical path difference required for reproducing a recording signal can be obtained. Therefore, the depth dp of the inner track information pits can be formed shallower than the track depth dg of the substrate, and therefore, the formation of the groove of the master and the substrate becomes easier. Therefore, the manufacturing cost of the optical information recording medium can be reduced.

Claims (10)

1. An optical information recording medium comprising a substrate having formed on one surface thereof a land, a track having a flat bottom surface, and an inner-track information pit having a flat bottom surface, a recording layer containing an organic dye formed on the one surface of the substrate, and a reflective layer formed on the recording layer, characterized in that:

when the depth from the land surface of the substrate to the track bottom surface is denoted by dg, the depth from the land surface of the substrate to the inner track information pit bottom surface is denoted by dp, the recording layer pit depth from the interface between the recording layer and the reflective layer on the land surface to the interface between the recording layer and the reflective layer in the track is denoted by Tg, and the recording layer pit depth from the interface between the recording layer and the reflective layer on the land surface to the interface between the recording layer and the reflective layer in the inner track information pit is denoted by Tp, dp/dg < Tp/Tg is present.

2. The optical information recording medium according to claim 1, wherein a ratio Tp/Tg of a pit depth Tp of the recording layer in the inner track information pit and a pit depth Tg of the recording layer in the track is: Tp/Tg is more than or equal to 1.6 and less than or equal to 2.0.

3. The optical information recording medium according to claim 1, wherein when λ represents a wavelength of a recording or reproducing light of the optical information recording medium, and n represents a refractive index of the substrate, a depth dg to the bottom surface of the track is dg > λ/4 n.

4. The optical information recording medium according to claim 1, wherein: the ratio dp/dg of the depth dp to the bottom of the inner track information pit to the depth dg to the bottom of the track is 1.4. ltoreq. dp/dg. ltoreq.1.7.

5. The optical information recording medium according to claim 1, wherein: the optical information recording medium has a stage and a track, and a substrate is obtained by injection molding using a stamper having management information formed in advance on an information pit, a coating material recording layer is formed on the substrate by spin coating, and a UV resin layer is formed on the recording layer.

6. The optical information recording medium according to claim 5, wherein the management information includes information on copyright protection.

7. The optical information recording medium according to claim 5 or 6, wherein said information pits are provided in said tracks, and the depth of said information pits is deeper than said tracks.

8. An optical information recording medium comprising a substrate having formed on one surface thereof a land, a track having a flat bottom surface, and an inner track information pit having a flat bottom surface, a reflective layer formed on the one surface of the substrate, 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, characterized in that:

when the depth from the land surface of the substrate to the track bottom surface is denoted by dg, the depth from the land surface of the substrate to the inner track information pit bottom surface is denoted by dp, the pit depth from the interface between the recording layer and the reflective layer on the land surface to the recording layer at the interface between the recording layer and the protective layer in the track is denoted by Tg ', and the pit depth from the interface between the recording layer and the protective layer on the land surface to the recording layer at the interface between the recording layer and the protective layer in the inner track information pit is denoted by Tp', dp/dg < Tp '/Tg' is given.

9. The optical information recording medium according to claim 8, wherein: the ratio Tp '/Tg' of the pit depth Tp of the recording layer in the inner track information pit to the pit depth Tg of the recording layer in the track is 1.6-2.0.

10. The optical information recording medium according to claim 8, wherein: when λ represents the wavelength of light for recording or reproduction of an optical information recording medium and n represents the refractive index of the surface layer, the depth dg to the bottom surface of the track is dg > λ/4 n.