JP2002203340A - Optical information medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a stable tracking in the case of a land/groove recording in an optical information medium, in which an optical effect layer and a light transmission layer including a recording layer are laminated on a substrate having lands and grooves, and the lands and the grooves are transferred on the light transmission layer, and to set the asymmetry of a prepit reproduced signal within appropriate range in the optical information medium, in which the optical effect layer and the light transmission layer including a reflective layer are laminated on the substrate having the prepits, and the prepits are transferred on light transmission layer. SOLUTION: The optical information medium satisfies PG<=0.80 μm and 0.51<=WG/PG<=0.70 wherein a groove pitch is PG and a groove width is WG. PT<=0.40 μm, and 0.30<=WP/PT<=0.48 wherein a recording track pitch is PT and the width of the prepit is WP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information medium such as an optical recording disk and a read-only optical disk.

[0002]

2. Description of the Related Art In recent years, in optical recording media such as a read-only optical disk and an optical recording disk, in order to record or store enormous information such as moving image information, it is required to increase the capacity of the medium by improving the recording density. In order to respond, research and development for higher recording density have been actively conducted.

One of them is, for example, DVD (Di
As shown in the “Gital Versatile Disk”, the recording / reproducing wavelength is shortened, and the numerical aperture (NA) of the objective lens of the recording / reproducing optical system is increased to reduce the laser beam spot diameter during recording / reproducing. It has been proposed to.
When comparing DVD with CD, the recording / reproducing wavelength is 780 nm.
To 650 nm and NA from 0.45 to 0.6 to improve the bit density and shorten the recording track pitch, thereby increasing the recording capacity by 6 to 8 times (4.7 times).
GB / side).

However, when the NA is increased as described above, a tilt margin is reduced. The tilt margin is
The tolerance of the tilt of the optical recording medium with respect to the optical system.
Is determined by Assuming that the recording / reproducing wavelength is λ and the thickness of the transparent substrate on which the recording / reproducing light is incident is t, the tilt margin is proportional to λ / (t · NA ³ ). When the optical recording medium is tilted with respect to the laser beam, that is, when tilt occurs, wavefront aberration (coma aberration) occurs. Assuming that the refractive index of the substrate is n and the inclination angle is θ, the wavefront aberration coefficient is (１ ／) · t · {n ² · sin θ · cos θ} · NA ³ / (n
² −sin ² θ) ^-5/2 . From these equations, it can be seen that in order to increase the tilt margin and suppress the occurrence of coma, the thickness t of the base may be reduced. Actually, in the DVD, the tilt margin is secured by setting the thickness of the base to about half (about 0.6 mm) of the thickness of the CD base (about 1.2 mm).

By the way, in order to record a high-quality moving image for a long period of time, there has been proposed a structure in which the substrate can be made thinner. In this structure, a substrate having a normal thickness is used as a supporting substrate for maintaining rigidity, pits and a recording layer are formed on the surface thereof, and a light transmitting layer having a thickness of about 0.1 mm is formed thereon as a thin substrate. The recording / reproducing light is made incident through the light transmitting layer. With this structure, the substrate can be made significantly thinner than in the past, so that a high recording density can be achieved by increasing the NA. A medium having such a structure is disclosed in, for example, JP-A-10-320859 and JP-A-11-1.
No. 20,613.

By providing a light transmitting layer having a thickness of about 0.1 mm, an objective lens having a large numerical aperture NA, for example, having an NA of about 0.85 can be used.

As a method for forming the light transmitting layer having a thickness of about 0.1 mm, for example, a spin coating method can be mentioned. In the case of using the spin coating method, a resin layer is formed by supplying a resin to the surface of a disk substrate fixed to a rotary table, rotating the disk substrate, and spreading the resin by centrifugal force.

In an optical recording medium, a groove (guide groove) is formed in a base for tracking, and the groove may carry address information. conventionally,
The area (land) within the groove or between adjacent grooves
Generally, only the recording track was used. However, recently, a land / groove recording method using both grooves and lands as recording tracks has been proposed because of the necessity of narrowing the recording track pitch in order to perform high-density recording.

When the land / groove recording method is applied to the optical recording medium having the above-described light transmitting layer, first, as shown in FIG. 1, a concave / convex pattern composed of a groove 20G and a land 20L is formed on the surface of a support base 20. It is common to form a reflective layer 5, a second dielectric layer 32, a phase-change type recording layer 4 and a first dielectric layer 31 in this order, and finally form a light transmitting layer 2 thereon. It is a target. At this time,
By the transfer of the groove 20G and the land 20L, the concave and convex pattern formed by the groove 20G and the land 20L is transferred to the light transmitting layer 2.

[0010]

As described above, techniques for improving the recording density of an optical recording medium include decreasing the recording track pitch, making recording / reproducing light incident through a thin light transmitting layer, The same applies to a read-only type medium. Further, for an optical recording medium, a land / groove recording method may be employed.

The present inventors prototyped a number of optical recording media and read-only media employing these techniques, and examined the recording / reproducing characteristics. As a result, it was found that when the recording track pitch was narrowed, a problem occurred in tracking in an optical recording medium, and a problem occurred in signal asymmetry in a read-only medium.

Specifically, in an optical recording medium, a relatively large difference occurs in the on-track level between the groove and the land, so that stable tracking becomes difficult. On the other hand, in a read-only medium, it has been difficult to keep the asymmetry of the pre-pit signal within an appropriate range.

An object of the present invention is to have a structure in which an optical effect layer including a recording layer and a light transmitting layer are laminated on a supporting base having lands and grooves, and the lands and grooves are transferred to the light transmitting layer. It is an object of the present invention to enable stable tracking when performing recording / reproduction in an optical information medium by a land / groove recording method. Another object of the present invention is to provide an optical information medium having a structure in which an optical effect layer including a reflective layer and a light transmitting layer are laminated on a supporting substrate having prepits, and the prepits are transferred to the light transmitting layer. In this case, the asymmetry of the pre-pit reproduced signal falls within an appropriate range.

[0014]

This and other objects are achieved by the present invention which is defined below as (1) to (5). (1) A support base is provided, and grooves, which are concave, and lands, which are convex, are alternately present on one main surface of the support, and at least a recording layer is formed on the groove forming surface of the support. An optical effect layer is formed, and a light transmitting layer is formed on the optical effect layer. On the main surface of the light transmitting layer facing the support base, the ridges and concaves formed by transferring the grooves and lands are formed. there exist alternately, grooves and lands are used as recording tracks, the optical information medium recording / reproducing light is incident through the light transmitting layer, represents the arrangement pitch of the grooves in the P _G, the width of the groove when the expressed in _{W G, P G ≦ 0.80μm,} 0.51 ≦ W G / P G ≦ 0.70 in which the optical information medium. (2) The optical information medium according to (1), wherein a reflective layer is formed between the support base and the recording layer. (3) having a support base, having a prepit as a concave portion on one main surface of the support base, and forming an optical effect layer including at least a reflective layer on a prepit formation surface of the support base; A light transmission layer is formed on the optical effect layer,
On the main surface of the light transmitting layer facing the support substrate, there is a projection formed by transferring the pre-pits, and the pre-pits are linearly arranged to form a recording track, and the reproduction light is transmitted through the light transmitting layer. , The recording track pitch is denoted by _PT , and the prepit width measured in the recording track width direction is denoted by W _P , where P _T ≦ 0.40 μm and 0.30 ≦ W _P An optical information medium wherein / P _T ≦ 0.48. (4) having a support base, having a prepit as a convex portion on one main surface of the support base, and forming an optical effect layer including at least a reflective layer on a prepit formation surface of the support base; A light transmitting layer is formed on the optical effect layer,
A concave portion formed by transfer of the pre-pits is present on the main surface of the light-transmitting layer facing the support base, and the pre-pits are linearly arranged to form a recording track, and reproduction light passes through the light-transmitting layer. In the incident optical information medium, when the recording track pitch is represented by _PT and the width of the prepit measured in the recording track width direction is represented by W _P , P _T ≦ 0.40 μm, 0.22 ≦ W _P / An optical information medium in which P _T ≦ 0.40. (5) The optical information medium according to any one of (1) to (4), wherein the thickness of the optical effect layer is 5 to 500 nm.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment First, a first embodiment of the present invention will be described.

FIG. 1 shows an optical information medium having a phase-change type recording layer as a configuration example of the medium of the first embodiment. This optical information medium has a support base 20. On one main surface of the support base 20, grooves 20G, which are concave stripes, and lands 20L, which are convex stripes, alternately exist. On this main surface, an optical effect layer 10 including at least a recording layer is formed. The light transmitting layer 2 is formed on the optical effect layer 10, and the main surface of the light transmitting layer 2 facing the support base 20 has ridges 2 </ b> GT and concave portions formed by transferring the groove 20 </ b> G and the land 20 </ b> L, respectively. Article 2LT alternates. In this medium, the recording / reproducing light passes through the light transmitting layer 2.
And the land 20L and the groove 20G are both used as recording tracks.

In this specification, a medium having the structure shown in FIG. 1, that is, a medium in which a light transmitting layer on which recording / reproducing light is incident is laminated at the end of the manufacturing process, is referred to as a reverse film forming type medium. Call. On the other hand, a land and a groove are formed on a translucent substrate having relatively high rigidity, an optical effect layer including a recording layer is formed thereon, and a type of medium on which recording / reproducing light is incident through the translucent substrate is used. , Is referred to as a normal film formation type medium.

Conventionally, in the medium of the normal film formation type, in order to make the on-track level equal between the land and the groove,
The land width and the groove width are controlled so as to have an appropriate ratio. Then, even in medium GyakuNarumaku type, the ratio between the width W _L of the width W _G and the land 20L of the groove 20G in the support 20, were the same as those in JunNarumaku type. However, the present inventors have found that when the recording track pitch is narrow, particularly when the arrangement pitch (groove pitch) P _G of the groove were less 0.80μm is directly findings in JunNarumaku type Not applicable,
We found that the difference in on-track level between land and groove was so large that it could not be ignored. In addition,
Groove pitch P _G in land / groove recording method
Is twice the recording track pitch, and (W _G +
W _L) and equal.

In the reverse film forming type medium shown in FIG.
Relatively large differences in the on-track level between land and groove only when the groove pitch P _G is narrow from occurring is believed to be due to the reasons explained below.

First, the optical effect layer 10 shown in FIG. 1 will be described. In the present specification, the optical effect layer means a layer that exerts an optical effect such as refraction or reflection on recording / reproducing light, such as a recording layer, a dielectric layer, and a reflection layer. In the phase change type medium, as shown in FIG. 4, the optical effect layer 10 is formed by forming the reflection layer 5, the second dielectric layer 32, the phase change type recording layer 4, and the first dielectric layer from the support base 20 side. It is general that 31 is a laminated body laminated in this order.

As shown in FIG. 1, the side walls of the groove 20G are not perpendicular to the bottom surface but are inclined. Therefore, the optical effect layer 10 adheres to the side wall of the groove 20G regardless of the step coverage at the time of formation. as a result,
Width W _GT of ridges 2GT formed on the light transmitting layer 2 by a transfer groove 20G is made narrower than the groove width W _G, whereas the width of the concave 2LT formed on the light transmitting layer 2 by a transfer of the land 20L W _LT is wider than land width W _L. Note that, in this specification, the width of the uneven portion having the inclined side wall or side peripheral surface is a value measured at an intermediate position in the depth direction or the height direction as illustrated. Generally, when narrowing the recording track pitch, the wavelength of the recording / reproducing light is shortened. In this case, the thickness of the optical effect layer 10 is hardly changed, or is reduced as the wavelength of the recording / reproducing light is shortened. However, compared to the decrease rate of the recording track pitch,
The reduction rate of the thickness of the optical effect layer 10 is small. for that reason,
In the medium of the reverse film formation type shown in FIG.
Groove pitch P _G without changing the ratio between the _G and the land width W _L
As you narrow, in the light transmitting layer 2, the ratio of the difference between the ridge width W _GT and concave width W _LT becomes larger with respect to a groove pitch P _G.

[0022] considered in conjunction with this and, when the groove pitch P _G is reduced to a certain extent and that a relatively large difference in the on-track level in the land and groove occurs,
The present inventors inferred as follows. In GyakuNarumaku types of media, the support base 20, the groove 20 of the width W _G
Be provided lands 20L of G and a width W _L, the width of the region functioning as effectively grooves and lands in the tracking is not the width W _G and a width W _L. The width of this effectively functioning region is determined by the width W _{GT of the} ridge 2GT formed on the light transmitting layer 2 by the transfer of the groove 20G and the width of the land 2GT.
2LT formed in the light transmission layer 2 by transfer of 0L
A width W _LT or a value in the vicinity thereof.

Based on such considerations, the present inventors have repeated experiments, and are of the reverse film forming type as shown in FIG. 1, the land / groove recording method is applied, and P _G ≦ 0 in high track density of the medium is .80Myuemu, and _{0.51 ≦ W G / P G ≦} 0.70, preferably if _{0.55 ≦ W G / P G ≦} 0.65, the grooves and lands We found that the on-track level could be almost the same and stable tracking was possible. Specifically, _assuming that the on-track level of the land is L _OTL and the on-track level of the groove is G _OTL , both 2L _OTL / (L _OTL + G _OTL ) and 2G _OTL / (L _OTL + G _OTL ) are 0. 9-1.
It can be 1. That is, in both the land and the groove, the on-track level can be kept within ± 10% of the average value. The on-track level is proportional to the amount of light reflected from the medium. W _G / P _G
Is too small or too large, the difference in on-track level between the groove and the land becomes large. Incidentally, the groove pitch P _G is too small, the effect of the present invention can not be sufficiently exhibited, and preferably 0.4 .mu.m ≦ P _G.

The first embodiment can be applied to a magneto-optical recording medium and a write-once medium using an organic dye as a recording material, in addition to the above-described phase change medium.

In the first embodiment, the thickness of the optical effect layer is 5 to 5.
It is particularly effective when the thickness is 500 nm, especially 100 to 500 nm. In addition, the depth of the groove 20G in the first embodiment may be appropriately determined according to the wavelength of the recording / reproducing light, but is usually in the range of 30 to 60 nm.

Second Embodiment Next, a second embodiment of the present invention will be described.

FIG. 2 shows a read-only optical information medium as a configuration example of the medium of the second embodiment. This optical information medium has a support base 20. On one main surface of the support base 20, there are pre-pits 20P which are concave portions. On this main surface, an optical effect layer 10 including at least a reflective layer is formed. The light transmitting layer 2 is formed on the optical effect layer 10, and the main surface of the light transmitting layer 2 facing the support base 20 has a convex portion 2PT formed by transferring the pre-pit 20P. In this medium, the reproduction light enters through the light transmission layer, and the prepits 20P are linearly arranged to form a recording track. This medium is also of the above-mentioned reverse film formation type.

Conventionally, in a read-only medium of the forward film formation type, the ratio of the prepit width to the recording track pitch (prepit arrangement pitch in the track width direction) is optimized in order to keep the asymmetry of the prepit reproduction signal within a preferable range. It was common to do. And
Also in GyakuNarumaku types of media, the optimum value of the width W _P of the pre-pit 20P provided in the supporting substrate 20, was the same as the optimum value of the pre-pit width in JunNarumaku type. However, the present inventors set the recording track pitch _PT at 0.40.
When the thickness is less than μm, it has been found that the knowledge of the forward film formation type cannot be applied as it is, and the asymmetry becomes so large that it cannot be ignored.

In the medium of the reverse film formation type shown in FIG.
It is considered that the asymmetry deteriorates only when the recording track pitch is narrow, for the following reason.

As shown in FIG. 2, the side peripheral surface of the pre-pit 20P is not perpendicular to the bottom surface but is inclined. Therefore, the optical effect layer 10 adheres to the side peripheral surface of the pre-pit 20P regardless of the step coverage at the time of formation. As a result, even if the width W _{P of the} pre-pits 20P is set to be the same as the width of the pre-pits of the forward film formation type, the width W _PT of the projection PT formed on the light transmitting layer 2 by the transfer of the pre-pits 20P is
It is smaller than the pre-pit width of the normal film formation type. In general,
To narrow the recording track pitch, the wavelength of the recording / reproducing light is shortened. In this case, the thickness of the optical effect layer 10 is hardly changed, or is reduced as the wavelength of the recording / reproducing light is shortened. However, the reduction rate of the thickness of the optical effect layer 10 is smaller than the reduction rate of the recording track pitch.
Therefore, in the reverse film type medium shown in FIG. 2, when a width W _P of the recording track pitch P _T and pre-pits 20P is narrower in the same proportion, in the light transmitting layer 2, the convex with respect to the recording track pitch P _T The ratio of the width W _PT of the portion 2PT decreases.

Considering this and the fact that the asymmetry deteriorates when the recording track pitch _PT is reduced to some extent, the present inventors have inferred the following. In the case of the reverse film-forming type medium, even if the support base 20 is provided with the pre-pits 20P having the width W _P , the width of the region which effectively functions as the pre-pits when reproducing the pre-pit signal has a width W _P
Not _P. The width of the region that functions effectively is the width W _{PT of the} convex portion 2PT formed on the light transmitting layer 2 by the transfer of the prepit 20P or a value near the width W _PT .

Based on such considerations, the present inventors repeated the experiment, and confirmed that the pre-pits 20P of the reverse film formation type and having concave portions as shown in FIG.
Provided, and, P _T ≦ In high track density of the medium is 0.40 .mu.m, and _{0.30 ≦ W P / P T ≦} 0.48, preferably _{0.35 ≦ W P / P T ≦} 0. 45, it has been found that the asymmetry of the pre-pit reproduced signal can be kept within the optimum range, and that a high-quality signal can be reproduced. If W _P / P _T is too small or too large, it will be difficult to keep asymmetry within the optimum range. If the recording track pitch _PT is too small,
Since the effect of the present invention cannot be sufficiently exhibited, preferably, 0.20 μm ≦ _PT .

Here, the asymmetry of the reproduced signal
explain. FIG. 5 is a graph for explaining asymmetry.
Show This graph shows the pre-pit reproduction signal output.
The shortest signal output and the longest signal output are schematically shown.
You. The asymmetry is (AB) / 2C in FIG.
It is. In positive asymmetry, the amplitude center of the shortest pit is
Indicates that it is on the ground side from the center of amplitude of the long pit
And negative asymmetry indicates the opposite. Departure
The optimal range of asymmetry in the bright optical information medium is -0.05≤ (AB) /2C≤0.15. If the asymmetry is outside the optimal range, jitter
It gets bigger. W _P/ P_TIs a value within the above range
To keep the asymmetry within the above optimum range
Becomes easier.

In FIG. 2, the optical effect layer 10 includes at least a reflective layer. The reflection layer in this case is Al, A
Examples include a metal layer made of a simple substance such as u, Ag, Pt, and Cu, or an alloy containing one or more of them, a semimetal layer made of Si, Ge, or the like, and a dielectric multilayer film. Also, the second
Can be applied to a medium having both a read-only area in which prepits holding recording information are arranged and a recordable area in which grooves and lands exist. in this case,
In the read-only area, only the reflective layer may be provided, while in the recordable area, in addition to the reflective layer, a recording layer and a pair of dielectric layers sandwiching the recording layer may be provided. It may be the same as the possible area. In this case, it is preferable that the second aspect is applied to the pre-pit area and the first aspect is applied to the recordable area.

The thickness range of the optically effective layer in which the second embodiment is particularly effective is 5 to 200 nm, especially 20 to 200 nm.
Further, the depth of the pre-pit 20P in the second mode is
It may be appropriately determined according to the wavelength of the reproduction light.
It is in the range of 0 to 70 nm.

Third Embodiment Next, a third embodiment of the present invention will be described.

FIG. 3 shows a read-only optical information medium as a configuration example of the medium of the third embodiment. This optical information medium differs from FIG. 2 in that the prepits 20P provided on the support base 20 are convex portions. Therefore, the recesses 2PT are formed in the light transmitting layer 2 by transferring the prepits 20P. The rest is the same as the medium of the second embodiment.

As shown in FIG. 3, the side peripheral surface of the pre-pit 20P is not perpendicular to the bottom surface but is inclined. Therefore, the optical effect layer 10 adheres to the side peripheral surface of the pre-pit 20P regardless of the step coverage at the time of formation. As a result, even if the width W _{P of the} pre-pit 20P is set to be the same as the pre-pit width of the forward deposition type, the width W _PT of the concave portion PT of the light transmitting layer formed by the transfer of the pre-pit 20P is the same as that of the forward deposition type. It is wider than the pre-pit width. Generally, when narrowing the recording track pitch, the wavelength of the recording / reproducing light is shortened. In that case, the thickness of the optical effect layer 10 is
It is hardly changed or made thinner as the wavelength of the recording / reproducing light is shortened. However, the reduction rate of the thickness of the optical effect layer 10 is smaller than the reduction rate of the recording track pitch. Therefore, in the reverse film type medium shown in FIG. 3, when the width W _P of the recording track pitch P _T and pre-pits 20P is narrower in the same proportion, in the light transmitting layer 2, the concave portion for the recording track pitch P _T The ratio of the width W _PT of 2PT increases.

The inventors of the present invention have repeated the experiment through the considerations described in the second embodiment, and as a result, have found that the pre-pits 20P of the reverse film formation type and having convex portions as shown in FIG. Is provided on the support base 20 and in a medium having a high track density where P _T ≦ 0.40 μm, 0.22 ≦ W _P / P _T ≦ 0.40, preferably 0.25 ≦ W _P / P _{It has been found that when T} ≦ 0.35, the asymmetry of the prepit reproduced signal can be kept within the above-mentioned optimum range, and high-quality signal reproduction can be performed. If W _P / P _T is too small or too large, it will be difficult to keep asymmetry within the optimum range. If the recording track pitch _PT is too small, the effect of the present invention cannot be sufficiently exhibited, so that preferably 0.20 μm ≦ _PT .

The thickness range of the optically effective layer in which the third embodiment is particularly effective is the same as in the second embodiment. In addition, the height of the pre-pits 20P in the third embodiment may be appropriately determined according to the wavelength of the reproduction light, and is usually in the range of 30 to 70 nm.

[0041]

Example 1 (first embodiment) An optical recording disk sample having the structure shown in FIGS. 1 and 4 was manufactured by the following procedure.

Formation of groove 20G and land 20L
Disc-shaped support base 20 (made of polycarbonate,
(120mm diameter, 1.1mm thickness)₉₈Pd₁C
u₁(Reflection layer) with a thickness of 100 nm
It was formed by a tta method. The groove depth is 40nm
Was. Groove pitch P_G, And P_GGroove width for
W _GRatio W_G/ P_GIs the value shown in Table 1.

Next, a second dielectric layer 32 having a thickness of 20 nm was formed on the surface of the reflection layer by sputtering using an Al ₂ O ₃ target.

Next, a recording layer 4 having a thickness of 12 nm was formed on the surface of the second dielectric layer 32 by sputtering using an alloy target made of a phase change material. The composition (atomic ratio) of the recording layer was Sb ₇₄ Te ₁₈ Ge ₇ In ₁ .

Next, a first dielectric layer 31 having a thickness of 130 nm was formed on the surface of the recording layer 4 by sputtering using a ZnS (80 mol%)-SiO ₂ (20 mol%) target.

Next, an ultraviolet-curable resin was applied to the surface of the first dielectric layer 31 by spin coating, and was cured by irradiating ultraviolet rays to form a light-transmitting layer 2 having a thickness of 100 μm.

The thickness of the optical effect layer 10 composed of the reflection layer 5, the second dielectric layer 32, the recording layer 4 and the first dielectric layer 31 is 262 nm.

After the recording layer of the optical recording disk sample thus manufactured was initialized (crystallized) by a bulk eraser, the on-track level in each of the groove and the land was measured. The conditions of the evaluation apparatus used for the measurement were as follows: laser wavelength: 405 nm, numerical aperture of the objective lens: 0.85.

_Assuming that the on-track level of the land is L _OTL and the on-track level of the groove is G _OTL , 2L _OTL / (L _OTL
+ G _{OT L)} and 2G _OTL / (determine the L _OTL + G _OTL).
Table 1 shows the results.

[0050]

[Table 1]

From Table 1, the effect of the present invention is clear.
That is, when the groove pitch P _G is 0.8μm or less, by setting the groove width W _G as W _G / P _G is in the range of limiting in the present invention, in both of the land and the groove, on The track level can be kept within ± 10% of the average value.

Example 2 (Second Aspect) An optical disk sample having the structure shown in FIG. 2 was manufactured by the following procedure.

Disc-shaped support on which pre-pits 20P are formed
Holding base 20 (made of polycarbonate, diameter 120 mm, thickness
1.1mm) on the surface₉₈Pd₁Cu₁(Atomic ratio)
Forming a reflective layer with a thickness of 100 nm by sputtering
The optical effect layer 10 was obtained. Recording track pitch P_TIs
0.35μm, P_TPrepit width W_PRatio
W _P/ P_TWas set to 0.4. The depth of the pre-pit 20P
The thickness was 65 nm.

The asymmetry of this sample was measured using the same evaluation device as in Example 1.
It was in the range of 0.5 to 0.15.

Example 3 (Third Aspect) An optical disk sample having the structure shown in FIG. 3 was manufactured by the following procedure.

Disc-shaped support on which pre-pits 20P are formed
Holding base 20 (made of polycarbonate, diameter 120 mm, thickness
1.1mm) on the surface₉₈Pd₁Cu₁(Atomic ratio)
Forming a reflective layer with a thickness of 100 nm by sputtering
The optical effect layer 10 was obtained. Recording track pitch P_TIs
0.35μm, P_TPrepit width W_PRatio
W _P/ P_TWas set to 0.33. The pre-pit 20P
The height was 65 nm.

The asymmetry of this sample was measured using the same evaluation apparatus as in Example 1.
It was in the range of 0.5 to 0.15.

[0058]

According to the present invention, it is possible to control the ratio of the groove width to the groove pitch in an optical information medium of a reverse film formation type, to which a land / groove recording method is applied, and in which the recording track pitch is narrow. By
The on-track level can be made substantially the same between the groove and the land.

Further, according to the present invention, a reverse film formation type is provided.
Further, in an optical information medium having pre-pits and a narrow recording track pitch, by controlling the ratio of the pre-pit width to the recording track pitch, the asymmetry of the pre-pit reproduced signal can be kept within an optimum range.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a configuration example of an optical information medium having lands and grooves.

FIG. 2 is a partial cross-sectional view showing a configuration example of an optical information medium having pre-pits.

FIG. 3 is a partial cross-sectional view showing a configuration example of an optical information medium having pre-pits.

FIG. 4 is a partial cross-sectional view illustrating a configuration example of an optical recording disk.

FIG. 5 is a graph for explaining asymmetry.

[Explanation of symbols]

 Reference Signs List 2 light transmitting layer 2GT ridge on which groove is transferred 2LT ridge on which land is transferred 2PT convex or concave portion on which prepit is transferred 20 support base 20L land 20G groove 20P prepit 31 first dielectric layer 32 second dielectric Layer 4 Recording layer 5 Reflective layer 10 Optically effective layer

Claims (5)

[Claims] The present invention has a supporting base, and a groove as a concave and a land as a convex are alternately present on one main surface of the supporting base, and at least recording is performed on the groove forming surface of the supporting base. An optical effect layer including a layer is formed, a light transmitting layer is formed on the optical effect layer, and a ridge formed by transferring the groove and the land on a main surface of the light transmitting layer facing the support base. and the concave are present alternately, the grooves and lands are used as recording tracks, the optical information medium recording / reproducing light is incident through the light transmitting layer, represents the arrangement pitch of the grooves in the P _G, the grooves when representing the width in _{W G, P G ≦ 0.80μm,} 0.51 ≦ W G / P G ≦ 0.70 in which the optical information medium. 2. The optical information medium according to claim 1, wherein a reflective layer is formed between said support base and said recording layer. 3. A support base, wherein one main surface of the support base has pre-pits which are concave portions, and an optical effect layer including at least a reflective layer is formed on a pre-pit formation surface of the support base. A light transmitting layer is formed on the optical effect layer, and a convex portion formed by transferring the prepits is present on a main surface of the light transmitting layer facing the support base, and the prepits are arranged in a line. constitutes a recording track Te, an optical information medium reproducing light is incident through the light transmitting layer, expressed represent recording track pitch P _T, the width of the pre-pit measured in the recording track width direction W _{P when, P T ≦ 0.40μm, 0.30 ≦} W P / P T ≦ 0.48 in which the optical information medium. 4. A support base, wherein one main surface of the support base has pre-pits which are convex portions, and an optical effect layer including at least a reflective layer is formed on a pre-pit formation surface of the support base. A light transmitting layer is formed on the optical effect layer, and a concave portion formed by transferring the pre-pits is present on a main surface of the light transmitting layer facing the support base, and the pre-pits are arranged in a line. constitutes a recording track Te, an optical information medium reproducing light is incident through the light transmitting layer, expressed represent recording track pitch P _T, the width of the pre-pit measured in the recording track width direction W _{P when, P T ≦ 0.40μm, 0.22 ≦} W P / P T ≦ 0.40 in which the optical information medium. 5. The optical effect layer has a thickness of 5 to 500 nm.
The optical information medium according to any one of claims 1 to 4, wherein