JP2596474B2 - Optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, and more particularly to an optical information recording medium having a read-only area and a recordable area formed on the same main surface of a substrate.

[0002]

2. Description of the Related Art Hitherto, a read-only information carrier such as a so-called compact disk or CD-ROM (hereinafter referred to as a CD) has been known. In this type of carrier, a metal light reflecting film is formed on a translucent substrate having a plurality of pits arranged on a main surface, and a protective layer is further formed thereon. Such an information carrier reproduces predetermined information by irradiating a laser beam for reproduction from the translucent substrate side and reading the diffracted light of the laser beam. The pit depth is 110
The thickness is generally about 120 nm, and if it is more than this value, the phase is reversed and tracking cannot be performed.

[0003] Optical information recording media on which information can be recorded by irradiating a laser beam are also known. Among these types of optical information recording media, an optical information recording medium capable of obtaining a reproduction signal similar to that of a CD has recently been proposed. This has a light absorbing layer, a light reflecting layer, and a protective layer made of a hard layer on a light transmitting substrate.

Further, there has been proposed an optical information recording medium in which the read-only information carrier such as the CD and the recordable optical information recording medium are combined. This optical information recording medium has a read-only area in which a metal light reflection film and a protection film are formed on a light-transmitting substrate, and a recording layer, a light reflection layer, and other layers formed on the same main surface on the same substrate. And a recordable area. Specifically, Japanese Utility Model Application Laid-Open No. 61-193526
JP-A-1-282775, JP-A-1-28613
No. 5, JP-A-2-195540 and the like.

[0005] However, in an optical information recording medium having both a read-only area and a recordable area conventionally known, the read-only area has a structure in which a light reflecting film is formed on a light-transmitting substrate. Therefore, a boundary portion of at least several tens of μm was required between the recording layer and the recordable area. Therefore, at the boundary between the read-only area and the recordable area, tracking becomes difficult due to the variation of the boundary position or the difference in film thickness between the boundary and the recordable area. However, the start position of the recordable area cannot be accurately determined, which may be practically difficult.

Normally, a CD has a read area in the innermost area for setting conditions necessary for reproduction. In a conventional optical information recording medium having a read-only area, the innermost area is When it is necessary to record the conditions necessary for recording and the amount of information recorded in the recordable area because the area is a read-only area, such information is recorded in the innermost peripheral area in the same manner as a CD. It was difficult. Furthermore, it is desirable that a recordable area in an optical information recording medium having a read-only area of this type be formed at an arbitrary position according to the intended use and can be reproduced continuously with the read-only area. .

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been described in connection with the art. Can be obtained, and a read-only area can be provided at an arbitrary position, and further, from a read-only area to a recordable area,
Alternatively, it is another object to provide an optical information recording medium capable of continuously reproducing from a recordable area to a read-only area.

[0008]

That is, according to the present invention, recording can be performed from a read-only area by setting both the pits in the read-only area and the optical phase difference in the recordable portion of the recordable area to positive values. It focuses on enabling continuous tracking over an area, and has a light-transmitting substrate, a light-absorbing layer provided on the substrate, a light-reflecting layer provided on the light-absorbing layer, and a light-reflecting layer. A protection layer provided on the substrate, and a read-only area and a recordable area formed on the same main surface of the substrate. The read-only area has a pit row composed of a plurality of types of pits. The recordable area is an optical information recording medium having a recordable portion formed continuously with the pit row, wherein the pit is formed in a concave shape with respect to the substrate, and The concave part is formed on the substrate, the real part of the complex refractive index of the substrate is set to nsub, the real part of the complex refractive index of the light absorbing layer is set to nabs, and the depth of the pit is set to dps. The depth of the pre-groove constituting the recordable portion is dgs, and the difference in film thickness between the pit portion and the non-pit portion up to the layer boundary between the light absorbing layer and the light reflecting layer in the read-only region is dpa. Where dsub is the difference in film thickness between the pre-groove portion and the land portion up to the layer boundary between the light absorbing layer and the light reflecting layer in the recordable region, where nsub / nabs> 1-dpa / dp
s and nsub / nabs> 1-dga / dgs.

Further, when the average thickness of the light absorbing layer is dav, the wavelength of the reproduction light is λ, and the optical parameters are ρ = nabs · dav / λ, 0.05 ≦ ρ
≦ 0.6, and when the imaginary part of the complex refractive index of the light absorbing layer is represented by kabs, 0.01 ≦ kabs ≦
0.3 is desirable.

[0010]

In the optical information recording medium according to the present invention, the light absorbing layer provided in the recordable area is also provided continuously in the read-only area. A recordable portion of the recordable area can be formed continuously from the pit row. Therefore, it is possible to record satisfactorily from the end of the recordable area at the boundary with the read-only area to the recordable part.

Further, since the pit row and the recordable portion are provided continuously, the read-only area can be provided at an arbitrary position. Therefore, continuous reproduction is possible from the reproduction-only area to the recordable area or from the recordable area to the reproduction-only area.

Further, by setting nsub / nabs> 1-dpa / dps and nsub / nabs> 1-dga / dgs, the optical phase difference ΔSp of the pit portion and the optical phase difference ΔSg of the recordable portion are obtained. Can be set to positive values, so that tracking can be continuously performed from the pit portion of the read-only area to the recordable portion of the recordable area.

However, △ Sp = 2 dps ｛nsub-nabs
(1−dpa / dps)｝ / λ. Also, {Sg = 2dgs {nsub-nabs (1-dga / dgs)}}
/ Λ (both will be described later).

[0014]

Next, an optical information recording medium 1 according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of the optical information recording medium 1.
Form a first read-only area 2, a first recordable area 3, a second read-only area 4, and a second recordable area 5 from the innermost area to the outermost area, respectively. is there.

When the first recordable area 3 is formed in the innermost peripheral area, recording is performed only halfway in the second recordable area 5 formed in the outer peripheral area. Information on the end position can be recorded in the innermost first recordable area 3. Therefore, even when a new recording is performed, the position of the recording light can be easily and quickly positioned at the recording start position.

Since the first read-only area 2 and the second read-only area 4 have substantially the same structure, the "read-only area 2" will be used when it is not necessary to distinguish them from each other. It will be described as. Similarly, the first recordable area 3 and the second recordable area 5 are also described as “recordable area 3”.

FIG. 2 is an enlarged cross-sectional view schematically showing a portion of the read-only region 2. The optical information recording medium 1 in the portion of the read-only region 2 includes a light-transmitting substrate 6. ,
It has a light absorbing layer 7 formed on the main surface of the substrate 6, a light reflecting layer 8 formed on the light absorbing layer 7, and a protective layer 9 formed on the light reflecting layer 8. The substrate 6 is made of a resin such as polycarbonate. The light absorbing layer 7
Although this is composed of an organic dye such as cyanine, it may be composed of a plurality of layers. The light reflection layer 8 is made of a metal such as gold. The protective layer 9 is constituted by a hard layer made of an ultraviolet curable resin or the like.

On the main surface of the substrate 6, pits 10 which are concave with respect to the surface of the substrate 6 are formed. The substrate 6 and the light absorbing layer 7 are in contact with each other by a first layer boundary 11. Light absorbing layer 7
And the light reflection layer 8 are in contact with each other by the second layer boundary 12. The light reflecting layer 8 and the protective layer 9 are in contact with each other by a third layer boundary 13. When another layer is provided, the other layer may be interposed between the light reflection layer 8 and the protective layer 9.

FIG. 3 is a cross-sectional view schematically showing the recordable area 3 in an enlarged manner. The structure is the same as that of the read-only area 2 except that the pit 1 is formed on the substrate 6.
Instead of 0, the pre-groove 14 is formed in a spiral shape concave to the surface of the substrate 6. On the left and right sides of the pre-groove 14, portions other than the pre-groove 14, that is, land 15 are located. This land 15
Corresponds to a non-pit portion in the read-only area 2.

The bottom of the pregroove 14 functions as a recordable portion 16. That is,
When the optical information recording medium 1 is irradiated with recording light (recording laser light) L1, the light absorbing layer 7 generates heat by absorbing the energy of the laser light L1, and heat deformation occurs on the substrate 6 side to cause pits. A recording pit 17 corresponding to 10 is formed. In some cases, an optical change may occur in the light absorbing layer 7.

Further, the depth dgs of the pre-groove 14 (from the first layer boundary 11 between the light absorbing layer 7 and the substrate 6 at the land 15 to the bottom of the first layer boundary 11 at the pre-groove 14) The depth of the pit 10 dps
(From the first layer boundary 11 between the light absorbing layer 7 and the substrate 6 in the non-pit portion 15, the first
(Depth at the bottom of the layer boundary 11).

For example, if the depth dps of the pit 10 is 13
By setting it to 0 nm or more, the modulation degree specified in the CD standard, that is, I11 / Itop is 60% or more;
And 13 / Itop is 30% or more. However, “ltop” means that the CD
This is the maximum amount of reflected light in the raw signal.
Longest pit recorded in the groove where recording is performed
The amount of reflected light that is diffracted by and returned to the objective lens,
Anti-reflection reflected by non-pits and returned to the objective lens
An optically modulated component corresponding to the difference from the amount of emitted light.
"3" is recorded in the groove where the recording is performed
Anti-diffraction by the shortest pit and returning to the objective lens
The amount of radiation and reflected by the non-bit part and returned to the objective lens
Optical modulation component corresponding to the difference
You.

When the depth of the pregroove 14 forming the recordable portion 16 is dgs, dps / dgs ≧ 1.
5, that is, the depth dps of the pit 10 is
By setting the depth dgs of the pre-groove 14 to a certain ratio or more, the modulation degree specified in the CD standard can be satisfied, and the reproduction light (reproduction) of the pre-groove 14 portion of the recordable area 3 after recording can be achieved. Laser light), the reflectance to L2 can be as high as 70% or more.

Thus, the reproduced signal of the signal recorded in the recordable section 16 of the recordable area 3 can be made similar to the reproduced signal in the read-only area 2.

The width wgs of the recordable portion 16, that is, the pregroove 14, is formed wider than the width wps of the pit 10. For example, the width wps of the pit 10 is 0.3 μm
By setting the thickness to 0.8 μm or less, the portion of the pit 10 can be darkened, and a large degree of modulation can be obtained.

When the width of the pregroove 14 constituting the recordable portion 16 is wgs, wps / wgs ≦ 0.7
, Ie, the width wgs of the pre-groove 14
Is made wider than the width wps of the pit 10 by a certain ratio or more, so that the pit 10
The part can be brightened. Therefore, when recording is performed in the pre-groove 14 portion, the brightness of the recording portion can be made approximately the same as that of the pit 10.

Thus, a reproduction signal similar to the reproduction signal of the reproduction-only area 2 can be obtained also in the recordable area 3.

The pit 10 and the pre-groove 1
In order to obtain the substrate 6 having 4, first, a photoresist is applied to a master such as glass. A predetermined number of types of convex pits 10 are formed by intermittently irradiating this photoresist with a beam obtained by converting predetermined information into a signal using a mastering machine, and continuously irradiating the beam. By doing so, a convex recordable portion 16 is formed. Then, development is performed, and a stamper is manufactured by electroforming using the master. The substrate 6 on which the desired pits 10 and pre-grooves 14 are formed can be obtained by molding using this stamper by an injection molding method or the like.

FIG. 4 shows the surface of the substrate 6 from the first read-only area 2 to the first recordable area 3 or from the second read-only area 4 to the second recordable area 5 of the optical information recording medium 1. It is the elements on larger scale which showed. The upper side of FIG.
The read-only area 2 has a plurality of types of pits 10 thereon. The lower side is the recordable area 3 having the pregroove 14 or the recordable portion 16 on the substrate 6. As shown, a recordable portion 16 is formed continuously in 10 rows of pits.

Next, irradiation is performed from the substrate 6 side, and the light reflecting layer 8 is irradiated.
The optical phase difference of the reproduction light L2 reflected by the laser beam will be described (see FIGS. 2 and 3). The optical phase difference at the pit 10 is ΔSp, and the optical phase difference at the pre-groove 14 is ΔSg. The real part of the complex refractive index of the substrate 6 is nsub, and the real part of the complex refractive index of the light absorbing layer 7 is nabs. As described above, the depth of the pit 10 is set to dps, and the pre-groove 1
The depth of 4 is dgs. The difference in film thickness between the pit 10 and the non-pit portion 15 adjacent to the pit 10 up to the second layer boundary 12 between the light absorption layer 7 and the light reflection layer 8 in the read-only region 2, that is, in the portion of the non-pit portion 15 From the second layer boundary 12 between the light absorption layer 7 and the light reflection layer 8, the depth at the bottom of the second layer boundary 12 at the pit 10 is dpa. Second layer boundary 1 between light absorbing layer 7 and light reflecting layer 8 in recordable area 3
2, the difference in film thickness between the pre-groove 14 and the land 15, that is, from the second layer boundary 12 between the light absorbing layer 7 and the light reflecting layer 8 at the land 15, The depth at the bottom of the layer boundary 12 is d
ga. Further, the wavelength of the reproduction light is set to λ.

First, the optical phase difference 部分 of the pit 10 portion
Sp will be described. When the light is irradiated from the substrate 6 side, the light absorbing layer 7 in the pit 10 has a second depth from the deepest portion of the pit 10 with respect to the first layer boundary 11 on the substrate 6 side.
Assuming that the optical distance difference between the pit 10 up to the layer boundary 12 and the non-pit portion 15 adjacent to the pit 10 is ND, ND = nsub.dps + nabs.dpa-nabs.dps. Therefore, the reproduction light L2 from the substrate 6 side
Is irradiated, the optical phase difference ΔSp = 2ND / λ between the pit 10 and the non-pit portion 15 of the reproduction light L2 in the pit 10 reflected by the light reflecting layer 4 is ΔSp = 2dps ｛nsub− nabs (1-dpa / dps)｝ /
λ.

Similarly, the optical phase difference ΔSg of the reproduction light L2 between the pregroove 14 and the land 15 at the portion of the pregroove 14 reflected by the light reflection layer 7 is as follows: ΔSg = 2dgs ｛nsub-nabs (1-dga / dgs)｝ /
λ.

By making these optical phase differences ΔSp and ΔSg both positive values, when tracking is performed by the push-pull method, the pit 10 or the pre-groove 14 having a short optical distance and the optical path Diffracted light at the non-pit portion 15 or land 15 with a long distance becomes good, and tracking becomes easy in each region. Therefore, tracking can be continuously performed from the pit 10 to the pre-groove 14.

That is, ΔSp = 2 dps {nsub-nabs (1-dpa / dps)} /
The conditions for λ> 0 are derived below. Dps, nsu in this equation
Since b, nabs, dpa, and λ are all positive numerical values, when nsub-nabs (1-dpa / dps)> 0, {Sp
Takes a positive value. Therefore, when this conditional expression is modified, nsub / nabs> 1-dpa / dps.

Similarly, for the pregroove 14 portion, ΔSg = 2dgs {nsub-nabs (1-dga / dgs)} /
From λ> 0, nsub / nabs> 1-dga / dgs.

The absolute values of the optical phase differences ΔSp and ΔSg are defined in the following predetermined ranges. That is, 0.3 ≦ | △ Sp | <0.5 and | △ Sg | <0.3.

It should be noted that the shape of the pit 10 is convex with respect to the surface of the substrate 6 and the shape of the pit 10
The relationship between the film thickness of the light absorbing layer 7 and the depth of the substrate 6 in the non-pit portion 15 adjacent to this and the non-pit portion 15 is reversed. Therefore, when the pit 10 is concave, 0.3 ≦ | ≦ Sp | <0.
A range of 5 is desirable. When the pit 10 is convex, the range of 0.3 ≦ | △ Sp | ≦ 0.4 is desirable.

However, if the pit 10 is concave, the CD
In order to increase the degree of modulation while satisfying the standard, set the push-pull to about 0.05, and stably perform tracking by the push-pull method, △ Sp is 0.4 ≦ | △ Sp | ≦
A range of 0.45 is more preferred.

In the case where the pit 10 is convex, in order to obtain the same effect, the range of 0.2 ≦ | △ Sp | ≦ 0.3 is more preferable.

Further, the reflectivity of the pregroove 14 before recording is increased, and the push-pull is stabilized after recording.
For stable tracking by the push-pull method, △ Sg is more preferably in the range of 0.05 ≦ | △ Sg | ≦ 0.1.

Such nsub / nabs> 1-dpa / dps,
And nsub / nabs> 1-dga / dgs, or satisfy the range of optical phase differences ΔSp and ΔSg.
The refractive indices nsub and nabs of the substrate 6 and the light absorbing layer 7 and the depths dps and dg of the pits 10 and the pregrooves 14
s, difference in film thickness of light absorbing layer 7 or surface depth dpa and dg
a, and by selecting the wavelength λ of the reproduction light L2, it is possible to improve the reflectivity, modulation degree, and push-pull signal during reproduction, and to continuously connect the reproduction-only area 2 and the recordable area 3 to each other. And playback becomes possible.

Next, the substrate 6, the light absorbing layer 7, the light reflecting layer 8
The protective layer 9 will be described in more detail. The substrate 6 has a light-transmitting property with respect to the recording light L1 and the reproduction light L2, and is desirably a disk shape for the purpose of reproducing using a CD player or the like, but is a card shape. You may. This substrate 6 is made of, for example, polycarbonate,
This is constituted by injection molding a resin such as polyolefin or by cutting glass.

By using such a translucent substrate 6, the recording light L1 or the reproducing light L2 can be irradiated from the substrate 6 side, and the recording / reproducing characteristics caused by dust or flaws adhering to the light incident surface of the substrate 6 can be reduced. Can be eliminated.

The light absorbing layer 7 absorbs the recording light L1,
The absorption forms the recording pit 17 as a recording portion. Alternatively, it is made of a material having a property of forming a recording portion. Such a material may be one in which the optical properties of a portion irradiated by the recording light L1 change. For example, a material used for a known optical information recording medium such as a magneto-optical recording material such as a low melting point metal or an organic dye can be used. These materials are formed by a spin coating method, an evaporation method, or the like.

In order to obtain a high reflectance similar to that of a CD even with the light absorbing layer 7, it is necessary to consider the optical properties of the light absorbing layer 7. That is, the following is known from the results of experiments and simulations performed by the present inventors.

The real part of the complex refractive index of the light absorbing layer 7 is represented by nabs
And the imaginary part of the complex refractive index of the light absorbing layer 7 is kabs,
The average thickness of the light absorbing layer 7 is dav (shown as the volume of the light absorbing layer 7 / the area of the region where the light absorbing layer 7 is formed), and the wavelength of the reproduction light (reproduction laser light) L2 is λ. ,
Further, when the optical parameter ρ = nabs · dav / λ, 0.05 ≦ ρ ≦ 1.6 and 0.01 ≦
It has been found that a high reflectance (specifically, 70% or more) can be obtained when the relationship of kabs ≦ 0.3 is satisfied.

That is, in the optical information recording medium 1 having the structure in which the light absorbing layer 7 and the light reflecting layer 8 are provided on the substrate 6, the reflectance specified by the CD standard is 70% or more and the degree of modulation is shown. In order to obtain an output signal in which I11 / Itop is 60% or more and the degree of modulation I3 / Itop is 0.3 to 0.7, ρ = nabs · dav / λ is set to 0.05 ≦ ρ ≦
It has been found that by setting the value in the range of 1.6, it can be easily realized.

When ρ is smaller than 0.05,
Since the average thickness dav of the light absorbing layer 7 must be considerably reduced, it is not practical for manufacturing. Therefore, 0.05
The range of 0.30 ≦ ρ ≦ 0.6 is practical for obtaining a sufficient reflectance in the range of ≦ ρ ≦ 0.6, and 0.1 or more for obtaining a sufficient degree of modulation. The range of 0.45 ± 0.1 is the most desirable range in order to obtain a stable recording characteristic with a large modulation factor.

Further, as shown in FIG. 5, even if ρ is in the range of 0.6 or more, the reflectance can exceed 70% at the peak point on the graph. 0.6 <ρ <
In the range of 1.6, there are two peak points, always in the range of 0.6 <ρ <1.10 and in the range of 1.10 <ρ <1.6.
It has been found that high reflectance can be obtained at those peak points. When ρ> 1.6, the film thickness is large, so that it is difficult to control the film thickness.
Not practical for manufacturing.

A graph showing the relationship between ρ and the reflectance is as follows:
It is expressed as a function obtained by combining an exponential function and a periodic function, and the amplitude of the periodic function increases as ρ increases. The amplitude of such a periodic function changes with the complex refractive index and the thickness of the layers constituting the optical information recording medium 1, their homogeneity, and the like as parameters. For example, if the refractive index of the layer on the side where light is incident from the light absorbing layer 7 is small, the reflectance shifts in the direction in which the reflectance increases in the entire graph.

This graph is represented by an exponential function having the imaginary parts kabs and dav of the complex refractive index of the light absorbing layer 7 as parameters. As shown in FIG. Is also known to grow. Unless the light absorbing layer 7 is homogeneous and the real part nabs of the complex refractive index and the film thickness dav do not have non-uniform distribution, the present inventors have found that there is no change in the period of the point showing the peak in the above graph. Is known by simulation.

The reflectance at the bottom point of the graph in FIG. 5 can be increased by controlling the above parameter conditions depending on the conditions. However, when ρ is set near the bottom point, the reflectance can be increased. However, it is difficult to obtain a large degree of modulation, and in some cases, the reflectance may be higher than before recording. Therefore,
ρ is desirably set near the peak point.

Reference will also be made to the above kabs. In order to obtain a high reflectance, it is necessary that kabs is 0.3 or less. The present inventors have found that the setting of the numerical value of kabs is an important parameter. That is, if kabs is 0.3 or less, the reflectance increases as it approaches 0. Therefore, this range is most desirable. However, as the recording sensitivity approaches 0, the recording sensitivity becomes worse. Specifically, 0.
A range of at least 01 is desirable, and in practice, a value of around 0.05 is desirable.

When ρ is in the range of 0.05 to 0.6, the imaginary part kabs of the complex refractive index of the same layer is desirably 0.3 or less. When ρ is in the range of 0.6 to 1.6, kabs is preferably 0.2 or less.

The contents of the present invention can be applied to the case where there are other layers. For example, when a transparent layer (for example, an enhanced layer such as SiO2, an undercoating layer, etc.) is provided between the substrate 6 and the light absorbing layer 7, this layer may be treated as a part of the substrate 6, Absorbing layer 7 and light reflecting layer 8
(For example, an enhancement layer, an adhesive layer, a hard layer, etc.) are provided between the second light absorbing layer 7 and the second light absorbing layer 7.
Is treated as ρ = (n1 · d1 + n2 · n2) / λ, and when there are many layers, ρ = Σ (ni · di) / λ (where i is an integer and ni is the complex refractive index of each layer) If the real part and di are the average film thickness of each layer), it can be handled in the same manner even when there are a plurality of layers.

The composite complex refractive index K expressed as the average of kabs is calculated as follows: K = Σdi · ki / Σdi (where ki is the imaginary part of the complex refractive index of each layer). Can handle.

Next, since the light reflecting layer 8 needs to have as high a reflectance as possible in consideration of the relationship with the CD, gold, silver, aluminum, or an alloy thereof is deposited by known methods such as evaporation and sputtering. It is desirable to form by the thin film forming method. By providing the light reflection layer 8, the reflectance of the reproduction signal can be increased, so that a reproduction signal substantially similar to that of a CD can be obtained.

The protective layer 9 has a function of protecting the substrate 6, the light absorbing layer 7, the light reflecting layer 8, and the like, and a function of improving the recording of the recordable area 3. The hardness is determined by the relationship with the substrate 6 or the light absorbing layer 7 or the relationship with the recording mechanism. For example, in the case where recording is performed by the light absorption layer 7 absorbing light to generate heat and deforming the substrate 6 due to the heat generation, the hardness of the protective layer 9
Needless to say, the material is harder, but it is preferable that the material is hard enough not to deform the light reflection layer 8 side with respect to the light absorption layer 7.

When the pits 10 in the read-only area 2 are formed unevenly with respect to the surface of the substrate 6, such a recording mechanism is similar to the pits 10 in the read-only area 2 due to the deformation of the substrate 6. This is advantageous because it is possible to obtain a large amount of diffracted light. In such a case, the layer on the substrate 6 side with respect to the light absorbing layer 7 needs to be a layer that is deformed by irradiation of the recording light L1.

The position of the light absorbing layer 7 of the optical information recording medium 1 must be located between the light transmitting substrate 6 and the light reflecting layer 8. It must be between the protective layer 9.

Further, the light absorbing layer 7, the light reflecting layer 8 and the protective layer 9 are not limited to a single layer, but may be composed of a plurality of layers, and may have other functions. Good.

If the surface on which the light absorbing layer 7, the light reflecting layer 8 and the protective layer 9 are formed covers the read-only area 2 and the recordable area 3, it is not necessary to form them on the inner and outer peripheral edges. It is not always necessary to form it over the entire surface. However, from the read-only area 2 to the recordable area 3,
Alternatively, it is necessary to continuously form these layers from the recordable area 3 to the read-only area 2. Also,
In production, the material of the layer covering the read-only area 2 and the recordable area 3 needs to be the same, and the layer configuration also needs to be the same.

The read-only area 2 and the recordable area 3
As long as they are on the same main surface of the substrate 6, a plurality of them may be formed continuously regardless of their number and order.

The information recorded in the read-only area 2 of the present invention is constituted by a plurality of types of pits 10. The plurality of types of pits 10 referred to here are optical pits having different lengths in the direction in which the reproduction light L2 moves so that a plurality of signal lengths are generated at the time of reproduction. On the other hand, those formed with irregularities are usually used.

However, in consideration of compatibility with widely used information carriers such as CDs, it is desirable that the substrate 6 be formed with irregularities.

The pits 10 are formed by a known means, that is, by using a stamper or the like having a projection corresponding to the shape of the target pit 10 on the surface when the substrate 6 is formed, or by pressing the stamper thereafter. These are formed. When a reproduction light L2 is irradiated through a translucent substrate 6 on a pit row composed of pits 10 of this kind, diffraction light is generated along with the reproduction light L2, and a reproduction signal can be obtained.

The read-only area 2 has at least the light absorbing layer 7
And a light reflection layer 8 and a protective layer 9, and shows a region on the substrate 6 in which a pit row including a plurality of types of pits 10 is formed. The recordable area 3 includes the recordable unit 1
6 in a row of pits 10.

The light absorbing layer 7, the light reflecting layer 8, and the protective layer 9 similar to those in the recordable area 3 are also provided in a continuous portion from the row of the pits 10 to the recordable section 16 or from the recordable section 16 to the row of the pits 10. Is formed, it is possible to obtain almost the same recording / reproducing signal as the middle of the recordable unit 16 from the start position of the recordable unit 16 or the end position of the recordable unit 16. Further, tracking can be performed continuously from the row of pits 10 to the recordable section 16 or from the recordable section 16 to the row of pits 10.

The recordable portion 16 constituted by the pre-groove 14 irradiates the light absorbing layer 7 thereon with the recording light L1 to cause a chemical, physical or mechanical change in the irradiated portion. Alternatively, it is a region where a recording portion having the same function as the pit 10 in the read-only region 2, that is, a recording pit 17 is formed. As described above, the recording pits 17 may have any recording mechanism. However, since it is necessary that the recording pits 17 can be continuously reproduced from the reproduction-only area 2, it is possible to obtain a reproduction signal similar to that of the reproduction-only area 2. It is desirable to have a recording unit that can.

In the optical information recording medium 1 having a read-only area 2 in which pits 10 having irregularities are formed on a substrate 6 such as a CD, the pre-groove 14 or the recordable section 16 or the recordable section 16 is irradiated by the recording light L1. It is desirable that the recordable portion 16 be deformed in its periphery and be formed with concavities and convexities capable of obtaining the same diffracted light as the pits 10.

The present invention can be applied not only to the write-once type recordable area 3 but also to an erasable area.

In order to perform recording on the recordable section 16, it is desirable to have a tracking means. The tracking means is generally based on the pregroove 14, but is not limited to this, and may be a known tracking means, for example, a pit having a predetermined period or a predetermined period. .

The shape is not limited to a concave rectangular shape, but may be a V-shaped or U-shaped groove.
The recordable portion 16 may have a convex shape such as a Λ shape or a cap shape. When tracking is performed by the pre-groove 14, the pre-groove 14 may meander. The pit train and the recordable section 16
The shape on the surface of the substrate 6 is desirably concentric or spiral.

Recording on the optical information recording medium 1 having the read-only area 2 and the recordable area 3 is performed, for example, as follows. That is, while the central portion of the optical information recording medium 1 is clamped, and the optical information recording medium 1 is rotated at a predetermined number of rotations, tracking is performed by the pit train and the tracking guide means, and a recordable portion is formed based on information stored in the inner peripheral portion in advance. 16 start positions are detected. When the recording start position is detected, a recording light L1 (laser beam) having a relatively strong wavelength or a wavelength different from that of the reproduction light L2 is irradiated from the translucent substrate 6 side, and the recordable portion 16 has the same function as the pit 10. A recording portion, that is, a recording pit 17 is formed.

After the recording has been performed, information of the recording (for example, the recording end position) is recorded in the inner recordable area 3 by irradiating the recording light L1 in the same manner as described above.

The optical information recording medium 1 thus recorded is continuously reproduced even when reproduction is performed from the middle of the reproduction-only area 2 to the recordable area 3 formed on the outer peripheral portion. be able to. Further, even when a new recording is performed, the recording end position recorded before is recorded on the inner periphery, so that the start position can be easily determined.

Hereinafter, a more specific embodiment 1 of the present invention will be described. A read-only area in which a predetermined EFM signal is recorded in advance as pits having a track pitch of 1.6 μm as 11 types of lengths, and a spiral meandering pre-groove having a track pitch of 1.6 μm continuous to the read-only area. A stamper having a recordable area formed on the main surface of was prepared, and a circular polycarbonate substrate having a thickness of 1.2 mm was obtained by an injection molding method.

The pit shape of this substrate is concave, the pregroove shape is concave, the nsub of the substrate is 1.58,
The pit depth dps is 300 nm and the pregroove depth d
gs is 200 nm.

On this main surface, a cyanine dye dissolved in a solvent was formed by spin coating to form a dye layer. Nabs of this dye layer is 2.5, dav is 125 nm,
dpa is 165 nm, dga is 85 nm, nsub / nabs is 0.63, 1-dpa / dps is 0.45, 1-dga / dgs
Is 0.57. An Au film having a thickness of 50 nm was formed on the substrate on which such a dye film layer was formed by a sputtering method.

Next, a UV curable resin was formed to a thickness of 8 μm by spin coating, and then UV irradiation was performed to form a protective layer.

An EFM signal was recorded in the recordable area of the optical information recording medium thus obtained by using a commercially available recording device. At this time, the wavelength λ of the recording light is 780 nm, the linear velocity is 1.4 m / sec, and the recording power is 7.0 mW. Therefore, nabs · dav / λ is 0.4.

When this optical information recording medium was reproduced with a commercially available CD player, the following characteristics could be obtained. That is, the modulation degree (I11 / Ito
p) is 68%, the reflectance (Rtop) is 70%, the push-pull is 0.07, the modulation degree (I11 / Itop) of the recordable area is 75%, the reflectance (Rtop) is 72%, and the push-pull is 0. 0.06.

As described above, since the read-only area and the recordable area can obtain substantially the same characteristics, continuous reproduction is performed from the read-only area to the recordable area or from the recordable area to the read-only area. It turns out that it becomes possible.

[0084]

As described above, according to the present invention, nsub /
nabs> 1-dpa / dps, and nsub / nabs> 1-dga
By satisfying / dgs, the optical phase difference values ΔSp and ΔSg in the pit portion of the read-only area and the recordable portion (pre-groove) of the recordable area are both set to positive values, and Even in the recordable area at the boundary with the possible area, it is possible to perform recording capable of obtaining a good reproduction signal, and the reproduction-only area can be provided at an arbitrary position. From the recordable area to the read-only area, or from the recordable area to the read-only area.

Further, the provision of the read-only area makes it possible to supply a large amount of optical information recording media having the same information. In addition, since the light reflection layer is provided, the reflectance of the reproduction signal can be increased, and a reproduction signal similar to that of a CD can be obtained from any region.

[0086]

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of an optical information recording medium 1 according to an embodiment of the present invention.

FIG. 2 is an enlarged schematic sectional view of a portion of a read-only area 2 of the optical information recording medium 1;

FIG. 3 is a cross-sectional view schematically showing an enlarged portion of a recordable area 3 of the optical information recording medium 1;

FIG. 4 is a partially enlarged sectional view showing a read-only area 2 and a recordable area 3 on a substrate 6 of the optical information recording medium 1;

FIG. 5 is a graph showing a relationship between ρ (= nabs · dav / λ) and reflectance.

FIG. 6 is a graph showing the relationship between the imaginary part kabs of the complex refractive index of the light absorption layer 7 and the reflectance.

[Explanation of symbols]

Reference Signs List 1 optical information recording medium 2 first read-only area 3 first recordable area 4 second read-only area 5 second recordable area 6 substrate 7 light absorption layer 8 light reflection layer 9 protective layer 10 pit 11th 1 layer boundary 12 second layer boundary 13 third layer boundary 14 pregroove 15 land 16 recordable portion 17 recording pit dpa second layer boundary between light absorbing layer 7 and light reflecting layer 8 in read-only area 2 Pits 10 and non-pits 15 up to 12
(From the second layer boundary 12 between the light absorbing layer 7 and the light reflecting layer 8 at the non-pit portion 15,
0) The depth of the pregroove 14 and the land 1 up to the second layer boundary 12 between the light absorbing layer 7 and the light reflecting layer 8 in the dga recordable area 3.
5 (the depth from the second layer boundary 12 between the light absorbing layer 7 and the light reflecting layer 8 at the land 15 to the bottom of the second layer boundary 12 at the pregroove 14). dps Depth of the pit 10 (from the first layer boundary 11 between the light absorbing layer 7 and the substrate 6 at the non-pit portion 15 to the bottom of the first layer boundary 11 at the pit 10) dgs The depth of the pre-groove 14 (from the first layer boundary 11 between the light absorbing layer 7 and the substrate 6 at the land 15 to the bottom of the first layer boundary 11 at the pre-groove 14) wps pit 10 width wgs width of pregroove 14 nsub real part of complex refractive index of substrate 6 nabs real part of complex refractive index of light absorption layer 7 imaginary part of complex refractive index of light absorption layer 7 davs average of light absorption layer 7 Film thickness λ Wavelength of reproduction light L2 L1 Recording light (recording laser Light) L2 playback light (optical phase difference of the optical portion of the phase difference △ Sg pregroove 14 parts of the reproducing laser beam) △ Sp pit 10

Claims (1)

(57) [Claims] A light-transmitting substrate, a light-absorbing layer provided on the substrate, a light-reflecting layer provided on the light-absorbing layer, and a protective layer provided on the light-reflecting layer. A read-only area and a recordable area are formed on the same main surface of the substrate, and the read-only area has a pit row composed of an array of a plurality of types of pits. An optical information recording medium having a recordable portion formed continuously on the substrate, wherein the pits are formed in a concave shape with respect to the substrate, and the recordable portions are also formed with a concave shape with respect to the substrate. The real part of the complex refractive index of the substrate is defined as nsub, the real part of the complex refractive index of the light absorbing layer is defined as nabs, the depth of the pit is defined as dps, and the depth of the pregroove forming the recordable part is defined as nsubs. Is dgs, and the light absorption of the read-only area is The layer thickness difference between the pit portion and the non-pit portion up to the layer boundary between the layer and the light reflection layer is dpa, and the layer boundary between the light absorption layer and the light reflection layer in the recordable region, An optical information recording medium, wherein nsub / nabs> 1-dpa / dps and nsub / nabs> 1-dga / dgs, where dga is the difference in film thickness between the pregroove portion and the land portion. .