JP2000322773A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk which assures >=65% reflecting light quantity at a top level of a CD-R standard and further can prevent characteristic degradation by suppressing crosstalk between neighboring tracks. SOLUTION: In the disk-shaped optical disk in which a recording layer 2 is formed by spin-coating on a preformat of a transparent substrate 1 having the preformat in which grooves 4 and lands 5 are alternatively formed in concentric circular shape or in spiral shape on a surface thereof, flanks of both sides of the groove 4 are provided by respectively inclining toward a virtual face X being parallel to the land 5 of the transparent substrate 1, average taper angle θ1 of the flank of disk inner peripheral side of the groove 4 to the virtual face X is made to be smaller than average taper angle θ2 of flank 4b of disk outer peripheral side of the groove 4 to the virtual face X.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disc,
In particular, a transparent substrate having a preformat in which grooves and lands are alternately formed concentrically or spirally on the surface,
A recording layer formed by spin coating on the preformat on the transparent substrate.

[0002]

2. Description of the Related Art In recent years, an optical recording system for recording and reproducing information by irradiating a laser beam onto an optical disk has been developed with the progress of optical recording laser technology and a reduction in cost.

As one of such optical disks, a write-once optical disk using an organic dye, such as a CD-R (Compact Disk Recordable), has been commercialized. This optical disc can dissolve a recording material containing an organic dye in a solvent and apply a recording layer on a transparent substrate by spin coating to form a recording layer. There is an advantage that the manufacturing time is short and the manufacturing cost is low.

[0004]

The substrate of a write-once optical disc such as a CD-R or the like containing an organic dye as a recording material includes:
A spiral groove is formed, and there are lands between the spiral grooves. The grooves and the lands are alternately provided along the radial direction of the disk to form a preformat.

A solution of a recording material is dropped on the center of the transparent substrate 1, and the transparent substrate 1 is rotated at a high speed to centrifugally apply the solution radially outward on the transparent substrate 1 on which grooves 4 and lands 5 are alternately provided. In the spin coating method of forming the recording layer 2 by stretching the recording layer 2 as shown in FIG. 8, the formed recording layer 2 has a concave shape on the groove 4 and a relatively convex shape on the land 5 as shown in FIG. A depression (depression) 6 is generated in the recording layer 2 above the recording layer 4, and a step d 1 is generated between the lowermost part and the uppermost part of the recording layer 2. Reference numeral 3 in the drawing denotes a light reflection layer made of metal.

The amount of reflected light at the top level, which is the space (11T) between the bits (11T), has some effect on the dent (concave) 6 and
There is a concern that the amount of reflected light at vel decreases and that the amount of reflected light of 65% or more specified in the CD-R standard cannot be satisfied.

Further, when recording is performed on a portion where the dent 6 is formed, the recording portion easily spreads in the radial direction, and crosstalk occurs between adjacent tracks, thereby deteriorating the recording characteristics.

[0008] In the future, write-once optical disks such as CD-Rs containing organic dyes as recording materials will have a trend toward narrower track pitches for higher densities and higher speed spin coating by tact-up from the viewpoint of cost reduction. Therefore, the depression (recess) 6 (step d1) tends to be further increased, and the above-mentioned adverse effects are remarkably exhibited.

In particular, in recent years, there has been a demand for further increasing the recording capacity of an optical disk. As a method of achieving this, it is necessary to shorten the wavelength of a laser beam used for recording and reproduction to reduce the beam spot diameter. Thus, a method for increasing the recording density has been proposed. A DVD (digital versatile disk) has been proposed as a high-density recording optical disk according to this method, and a DVD-R (digital versatile disk recordable) has been proposed as a write-once type optical disk. The wavelength of the laser beam used for recording / reproducing the DVD-R is 630 nm to 660 nm.

The track pitch of the groove of the DVD-R is 0.7 μm to 0.8 μm, and the minimum recording pit is 0.40 μm.
m to 0.44 μm and a CD-R track pitch of 1.6
μm, which is extremely shorter than the minimum recording pit of 0.83 μm. When the track pitch is further narrowed by the increase in density and performance as described above, the influence (particularly, the problem of crosstalk) of the above-described dents (dents) 6 becomes more remarkable.

The present inventors have conducted various studies on the formation of the depressions (recesses) 6 and found that there is a problem in the cross-sectional shape of the groove 4 formed on the surface of the transparent substrate 1.
That is, in the conventional optical disk, as shown in FIG. 8, both side surfaces of the groove of the groove 4 are inclined, and the taper angle θ1 of the side surface 4a on the inner peripheral side of the groove and the taper angle of the side surface 4b on the outer peripheral side of the disk. θ2 is equal (θ1 = θ2 θ1 / θ
2 = 1).

For this purpose, a solution of the recording material is dropped almost at the center of the transparent substrate 1 fixed on the turntable, and the transparent substrate 1 is rotated at a high speed to flow the liquid recording material from the center toward the outer periphery. When the recording layer 2 is formed while being spread and solidified, the liquid recording material flows into the groove 4 and temporarily accumulates, and is further centrifugally applied to the land 5 on the outer peripheral side.
In addition, the recording material flows into the groove 4, but the recording material flows into the groove 4 at that time and rises at the side surface 4b on the outer peripheral side of the disk, so that a relatively deep dent (recess) 6 is formed. It has been found that the step d1 is large.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, reduce the dents, and secure a reflected light amount of 65% or more at the top level of the CD-R standard.
In addition, it is an object of the present invention to provide an optical disk that can suppress crosstalk between adjacent tracks and prevent deterioration in characteristics, and is particularly suitable for high-density recording.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a spinning pre-format of a transparent substrate having a pre-format in which grooves and lands are alternately formed concentrically or spirally on the surface. It is intended for an optical disc having a recording layer formed by a coat.

According to a first aspect of the present invention, when the groove is sectioned along a radial direction of the transparent substrate, both side surfaces of the groove of the groove are respectively inclined with respect to a virtual surface parallel to the land of the transparent substrate. The average taper angle θ1 of the inner peripheral side surface of the groove with respect to the virtual surface is smaller than the average taper angle θ2 of the outer peripheral side surface of the groove with respect to the virtual surface (θ1 <θ2). It is assumed that.

A second means of the present invention is the first means, wherein θ1 / θ2 is a ratio of θ1 to θ2.
Is in the range of 0.3 ≦ θ1 / θ2 <1.

A third means of the present invention is the first means, wherein θ1 / θ2 is a ratio of θ1 to θ2.
Is in the range of 0.75 ≦ θ1 / θ2 ≦ 0.9.

According to a fourth aspect of the present invention, in any one of the first to third means, the value of θ1 / θ2 gradually decreases from the inner area to the outer area of the disk. It is a feature.

In a fifth aspect of the present invention, in any one of the first to third means, the disk is divided into a plurality of zones from an inner region to an outer region of the disk, and the outermost zone includes the θ1 / The value of θ2 is smaller than the value of θ1 / θ2 in the innermost zone.

In a sixth aspect of the present invention, in any one of the first to third means, the disc is divided into a plurality of zones from an inner area to an outer area of the disk, and the value of θ1 / θ2 is It is characterized in that it gradually decreases from the circumferential zone to the outer circumferential zone.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the track pitch is 0.8.
μm or less.

According to an eighth aspect of the present invention, in any one of the first to sixth means, the track pitch is 0.7.
The thickness is 4 μm or less.

When the value of θ1 / θ2 becomes 1, it corresponds to a conventional optical disk, and as described above, the depression (recess) 6
(Step d1) increases, causing various adverse effects as described above. On the other hand, when the value of θ2 / θ1 is less than 0.3,
Since the center of the concave portion in the groove of the recording layer deviates from the center of the groove, the center of tracking and the center of writing deviate, resulting in a problem that sufficient characteristics cannot be obtained and recording and reproduction are hindered. Therefore, the value of θ1 / θ2 is
It is necessary to regulate within the range of 0.3 ≦ θ1 / θ2 <1.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2, when cutting a preformat pattern by irradiating an exposure beam 10 to a master on which a photoresist 8 is coated on a glass substrate 9, the exposure beam 10 is incident on the surface of the master at an angle θ0, The state of incidence of the exposure beam 10 on the master when a preformat pattern (groove) portion is exposed,
7 shows the exposure intensity distribution and the taper angles of the groove grooves on the inner and outer peripheral sides of the disk, respectively.

As shown in FIG.
0 is an incident angle θ0 = 90 °, that is, when the exposure beam 10 is vertically incident on the master via the objective lens 11 and the photoresist 8 is exposed, as shown in FIG. The exposure intensity distribution on the circumferential side and the outer circumferential side becomes the same. Therefore, as shown in FIG. 3A, the taper angle θ1 on the inner peripheral side after development and the taper angle θ2 on the outer peripheral side become equal.

On the other hand, as shown in FIG. 1B, when the incident beam θ0 <90 °, that is, the exposure beam 10 is incident on the master through the objective lens 11 with a slight inclination, and the photoresist 8 is exposed, As shown in FIG. 3B, the exposure intensity distribution on the inner peripheral side and the outer peripheral side are different from each other with the focal point therebetween, and the exposure range is narrower on the outer peripheral side than on the inner peripheral side. Therefore, as shown in FIG. 3B, the taper angle θ1 on the inner peripheral side of the groove can be made smaller than the taper angle θ2 on the outer peripheral side (θ1 <θ).
2).

After the master was exposed and developed as shown in FIGS. 1 (b1), (b2) and (b3), the master was plated with nickel or the like by a known technique to form a stamper.

Using this stamper, a transparent substrate 1 made of a polycarbonate resin is prepared by an injection molding method. As a material of the transparent substrate 1, other transparent resin materials such as an epoxy resin other than the polycarbonate resin can be used. The transparent substrate 1 created in this way has a preformat pattern of a stamper transferred thereon.

As shown in FIG. 1, the pregroove 4 of the preformat pattern has side surfaces 4a, 4b on both sides of the groove with respect to an imaginary plane X parallel to the land 5 of the transparent substrate 1.
Are provided so as to be inclined upward toward each other so as to have a wide angle. Then, the side surface 4 of the groove 4 on the disk inner peripheral side
a is smaller than the average taper angle θ2 of the side surface 4b on the outer peripheral side of the disk (θ1 <
θ2). The average taper angles θ1 and θ2 will be specifically described later.

In the present invention, the position of the imaginary plane X is defined as an intermediate position in the depth direction of the groove of the groove 4 (that is, L1 = L
2). As shown in FIG. 8, when a virtual surface passes through the groove bottom surface of the groove 4 or the surface of the land 5, the portion where the groove bottom surface of the groove 4 intersects or the portion where the surface of the land 5 intersects the side surface 4a, 4b. However, when viewed microscopically, there is a concern that an accurate angle cannot be obtained due to chipping or rounding, so the virtual plane X is a virtual plane passing through the middle position of the groove 4 in the depth direction.

A recording layer 2 containing an organic dye was formed on the surface of the transparent substrate 1 on which the preformat pattern was formed by spin coating. As the organic dye, cyanine-based, phthalocyanine-based, azo-based dyes, and the like can be used. In particular, organic dyes represented by the following general structural formulas [Chemical Formula 1] and [Chemical Formula 2] are preferable.

[0032]

Embedded image In the formula, R or R ′ may be the same or different, and each represents a hydrogen atom, an alkyl group, an alkoxyl group, an alkoxy group, an aralkyl group, an alkenyl group, an alkylcarboxyl group, or an alkylsulfonyl group. Y or Y 'may be the same or different, each being-
_{C (CH 3) 2 -,} - S -, - O -, - shows a CH = CH-. A or A 'may be the same or different, and each represents an aromatic ring or a benzene ring. X represents a counter ion, and represents a halogen and halide ion or a metal complex. Z represents a hydrogen atom, a halogen atom, or an alkyl group. n shows the integer of 0-2.

[0033]

Embedded image In the formula, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different and each is a hydrogen atom, a hydroxyl group, an alkyl fluoride group, an amine, an alkyl group, an alkoxyl group, an alkylhydro group, an aralkyl group, It represents an alkenyl group, an alkylcarboxyl group, an alkylsulfonyl group or an aromatic ring having these functional groups. X represents an anion, n represents the ionic value of the compound, and is 1 or 2.

It is to be noted that several kinds of organic dyes may be combined, and a quencher or an infrared absorbing agent can be added for the purpose of improving corrosion resistance and the like, and as the additive, aminium or imidium can be used. .

As described above, by forming the average taper angle θ1 of the inner peripheral side surface 4a of the groove 4 to be smaller than the average taper angle θ2 of the outer peripheral side surface 4b of the disk, the groove 4 and the land 5 are formed. When the recording layer 2 is formed by spin coating, as shown in FIG. 1, a slight dent (dent) 6 is formed in the recording layer 2, and the step d1 is markedly different from the conventional one shown in FIG. The state is small or almost nonexistent.

On the recording layer 2, a reflective layer 3 was formed by sputtering or vapor-depositing a metal such as Au, Ag, or Al or an alloy containing Au, Ag, Al, or the like. A write-once optical disc was formed by laminating a protective layer made of an acrylic UV curable resin on the reflective layer 3.

Next, a specific embodiment will be described. (Example 1) Using a glass master to duplicate a transparent substrate,
This glass master was prepared using a master exposure apparatus as follows. First, a polished glass substrate 9 is prepared, and a photoresist 8 comprising a cresol novolak resin having a refractive index of 1.65 and a photosensitive agent of naphthoquinonediazide is provided thereon.
Was applied to a thickness of 0.13 μm.

Next, as shown in FIG.
While rotating on a turntable, photoresist 8
The exposure beam 10 was irradiated from the inner circumference to the outer circumference at an angle of θ0 shown in FIG. From the innermost circumference to the outermost circumference θ0 =
It was fixed at 60 ° and exposed so that the cross-sectional shape at a track pitch (TP) of 1.6 μm became a trapezoidal continuous groove.

While rotating the glass substrate 9 after this exposure, it is applied onto the exposed photoresist 8 using an alkaline developing solution and developed, and a continuous groove corresponding to a groove is formed in the photoresist 8. The surface of the glass substrate 9 was plated with nickel to form a stamper, and the transparent substrate 1 made of polycarbonate resin was formed by injection molding using the stamper.

The average taper angle θ1 of the inner peripheral side surface 4a of the groove 4 of the transparent substrate 1 and the average taper angle θ2 of the outer peripheral side surface 4b of the disk were measured, and the results are shown in FIG.

In the present invention, the average taper angles θ1, θ2
Cuts the formed transparent substrate, measures the taper angle of the cut surface of the groove at 10 points at random using an atomic force microscope (AFM), calculates the average value, and calculates the average taper angles θ1, θ2. And Also, zones 1 to 4 in FIG.
4, the transparent substrate 1 is divided into four zones at substantially equal intervals from the inner peripheral side to the outer peripheral side, as shown in FIG. 13, zone 3 is denoted by reference numeral 14, and zone 4 is denoted by reference numeral 15.

As is apparent from the results of FIG. 4, by fixing θ0 = 60 ° from the innermost circumference to the outermost circumference,
In each of the zones 1 to 4, the average taper angle θ1 is 67 °, the average taper angle θ2 is 74 °, and the taper angle θ1 is greater than the taper angle θ.
5, and as is apparent from FIG. 5, the value of θ1 / θ2 is 0.9 in each of the zones 1 to 4, and 0.3 ≦ θ
2 / θ1 <1.

On the prepit pattern of the transparent substrate 1, an indole cyanine dye having the following structural formula [Formula 3] and an aminium salt are dissolved in a solvent, and a recording layer 2 having a thickness of 160 μm is formed by spin coating. did.

[0044]

Embedded image A light reflecting layer 3 made of gold and having a thickness of 100 nm is formed on the recording layer, and a 10 μm thick acrylic UV curable resin is formed so as to overcoat the recording layer 2 and the light reflecting layer 3. A write-once optical disc was prepared by laminating a protective layer.

The reflectance of each zone of the optical disk was measured, and the results are shown in FIG. FIG. 7A shows the reflectance of each part by dividing each zone into an inner side, a middle side, and an outer side. FIG. 3B is a graph of the reflectance of each of the above-mentioned portions, but the illustrations of Examples 1 and 5 are omitted because the lines overlap.

For this optical disc, a wavelength λ = 780
Using a laser beam of nm and an optical lens of NA = 0.50, a recording power of 7.0 mW and a linear velocity of 1.2 m
The random pattern was recorded at / s. On the other hand, for reproduction, a laser beam having a wavelength of λ = 780 nm was used, and NA = 0.4.
Using the optical lens No. 5 at a reproduction power of 0.1 mW and a linear velocity of 1.2 m / s, the crosstalk at that time was measured, and the results are shown in FIG. FIG. 7A is a table in which each zone is further divided into an inner side, a middle side, and an outer side, and crosstalk of each portion is tabulated. FIG. 6B is a graph of the crosstalk of each of the above-mentioned portions, but illustration of Examples 3 and 4 is omitted because the lines overlap.

(Example 2) The track pitch is set to 0.8 μm.
A stamper was prepared in the same manner as in Example 1 while fixing to θ0 = 60 °, and a transparent substrate made of a polycarbonate resin was prepared by injection molding using the stamper.

By exposing from the innermost periphery to the outermost periphery at θ0 = 60 °, as is apparent from FIG.
The average taper angle θ1 is 67 °, and the average taper angle θ2
Is 74 °, the taper angle θ1 is smaller than the taper angle θ2, and as is apparent from FIG. 5, the value of θ1 / θ2 is 0.9 in each of the zones 1 to 4, and 0.3 ≦ θ1 / θ2. <
Within the range of 1.

On a prepit pattern of the transparent substrate 1, a cyanine dye having the following structural formula [Formula 4] and an aminium salt are dissolved in a solvent, and a thickness of 16 is formed by spin coating.
A recording layer 2 having a thickness of 0 μm was formed.

[0050]

Embedded image A light reflecting layer 3 made of gold and having a thickness of 100 nm is formed on the recording layer, and an overcoating of the recording layer 2 and the light reflecting layer 3 is made of a 10 μm thick acrylic UV curable resin. A write-once optical disc was prepared by laminating a protective layer. FIG. 6 shows the reflectance of each zone of the optical disc, and FIG. 7 shows the crosstalk of each zone.

(Example 3) The track pitch is set to 0.8 μm.
As shown in FIG. 3, the zone 1 (reference numeral 12) and the zone 2 (reference numeral 13) have θ0 = 60 °, and the zone 3 (reference numeral 14) and zone 4 (reference numeral 15) have θ0 = 70 °, as in Example 1. A stamper was prepared, and a transparent substrate made of a polycarbonate resin was prepared by injection molding using the stamper.

When θ1 and θ2 in each zone of the transparent substrate were measured, as shown in FIG. 4, the average taper angle θ1 of zones 1 and 2 was 67 °, the average taper angle θ2 was 74 °, and zones 3 and 4 were measured. Has an average taper angle θ1 of 65 ° and an average taper angle θ2 of 81 °.
Is smaller than the taper angle θ2.

As is apparent from FIG.
Θ1 / θ2 of 0.9 is 0.9, and θ1 / θ2 of zones 3 and 4
Is 0.8, and the value of θ1 / θ2 is 0.3 for each zone.
.Ltoreq..theta.1 / .theta.2 <1, but the values of .theta.1 / .theta.2 in zones 3 and 4 corresponding to the outer area of the disk are smaller than those of zones 1 and 2 corresponding to the inner area. I have.

On the prepit pattern of the transparent substrate 1, a cyanine dye having the structural formula [Formula 4] and an aminium salt were dissolved in a solvent, and the thickness was adjusted to 16 by a spin coating method.
A recording layer 2 having a thickness of 0 μm was formed.

The recording layer is made of gold and has a thickness of 100 n.
m, and a 10 μm-thick protective layer made of an acrylic ultraviolet curable resin is laminated so as to overcoat the recording layer 2 and the light reflective layer 3 to form a write-once optical disc. did. FIG. 6 shows the reflectance of each zone of the optical disc, and FIG. 7 shows the crosstalk of each zone.

Example 4 A stamper was prepared in the same manner as in Example 1 except that the track pitch was set to 0.74 μm and each of the zones 1 to 4 was fixed at θ0 = 60 °, and the stamper was formed by injection molding using the stamper. A transparent substrate was created.

When θ1 and θ2 in each zone of the transparent substrate were measured, as shown in FIG. 4, the average taper angle θ1 was 67 ° and the average taper angle θ2 was 74 ° in each zone.
As is clear from FIG. 5, the value of θ1 / θ2 was 0.9 in each zone.

On the prepit pattern of the transparent substrate 1, a cyanine dye having the structural formula [Formula 4] and an aminium salt are dissolved in a solvent, and the thickness is adjusted to 16 by a spin coating method.
A recording layer 2 having a thickness of 0 μm was formed.

On this recording layer, a thickness of 100 n made of gold
m, and a 10 μm-thick protective layer made of an acrylic ultraviolet curable resin is laminated so as to overcoat the recording layer 2 and the light reflective layer 3 to form a write-once optical disc. did. FIG. 6 shows the reflectance of each zone of the optical disc, and FIG. 7 shows the crosstalk of each zone.

(Example 5) The track pitch is set to 0.74 μm, and as shown in FIG.
(Code 13) is θ0 = 60 °, and zone 3 (code 1)
Example 1 with 4) and zone 4 (reference numeral 15) as θ0 = 70 °
A stamper was prepared in the same manner as described above, and a transparent substrate made of a polycarbonate resin was prepared by injection molding using the stamper.

When θ1 and θ2 in each zone of the transparent substrate were measured, as shown in FIG. 4, the average taper angle θ1 of the zones 1 and 2 was 67 °, the average taper angle θ2 was 74 °, and the zones 3 and 4 were measured. Has an average taper angle θ1 of 65 ° and an average taper angle θ2 of 81 °.
Is smaller than the taper angle θ2.

As is apparent from FIG.
Θ1 / θ2 of 0.9 is 0.9, and θ1 / θ2 of zones 3 and 4
Is 0.8, and the value of θ1 / θ2 is 0.3 for each zone.
.Ltoreq..theta.1 / .theta.2 <1, but the values of .theta.1 / .theta.2 in zones 3 and 4 corresponding to the outer area of the disk are smaller than those of zones 1 and 2 corresponding to the inner area. I have.

On the pre-pit pattern of the transparent substrate 1, a cyanine dye having the structural formula [Formula 4] and an aminium salt are dissolved in a solvent, and the thickness is adjusted to 16 by a spin coating method.
A recording layer 2 having a thickness of 0 μm was formed.

On this recording layer, a thickness of 100 n
m, and a 10 μm-thick protective layer made of an acrylic ultraviolet curable resin is laminated so as to overcoat the recording layer 2 and the light reflective layer 3 to form a write-once optical disc. did. FIG. 6 shows the reflectance of each zone of the optical disc, and FIG. 7 shows the crosstalk of each zone.

(Example 6) The track pitch is 0.74 μm, zone 1 is θ0 = 60 °, and zone 2 is θ0 = 65.
°, zone 3 θ0 = 70 °, zone 4 θ0 = 75 °
A stamper was prepared in the same manner as in Example 1, and a transparent substrate made of a polycarbonate resin was prepared by injection molding using the stamper.

When θ1 and θ2 in each zone of the transparent substrate were measured, as shown in FIG.
Θ2 = 74 ° in °, θ2 = 7 in Zone 1 θ1 = 66 °
8 °, the angle θ2 = 81 ° at θ1 = 65 ° in zone 3, and θ2 = 83 ° at θ1 = 62 ° in zone 4, and the taper angle θ1 is smaller than the taper angle θ2 in each zone.

As is clear from FIG. 5, the values of θ1 / θ2 are 0.9 in zone 1, 0.85 in zone 2, 0.8 in zone 3, and 0.75 in zone 4. In both cases, the value of θ1 / θ2 is in the range of 0.3 ≦ θ1 / θ2 <1, but the value of θ1 / θ2 gradually decreases from the inner region to the outer region of the disk.

On the pre-pit pattern of the transparent substrate 1, a cyanine dye having the structural formula [Formula 4] and an aminium salt are dissolved in a solvent, and the thickness is adjusted to 16 by a spin coating method.
A recording layer 2 having a thickness of 0 μm was formed.

On this recording layer, a thickness of 100 n
m, and a 10 μm-thick protective layer made of an acrylic ultraviolet curable resin is laminated so as to overcoat the recording layer 2 and the light reflective layer 3 to form a write-once optical disc. did. FIG. 6 shows the reflectance of each zone of the optical disc, and FIG. 7 shows the crosstalk of each zone.

In the above embodiment, zones 1 to 4 were formed on the transparent substrate.
And the radial length of each zone was made substantially the same, but the present invention is not limited to this, and the number of divided zones and the radial length of each zone are appropriately set as necessary. Can be changed.

[0071]

As is clear from FIG. 6, the reflectance of each portion is 66% or more, and the reflected light amount of 65% or more at the top level of the CD-R standard is secured. Further, as is clear from FIG. 7, the crosstalk of each part is also suppressed low.

The evaluation of the crosstalk characteristic at each track pitch (TP) is shown on the right side of FIG. As shown in the figure, when the TP is relatively large at 1.6 μm as in Example 1, even if the θ1 / θ2 values of the respective zones are the same in the entire area of the disk, there is almost no influence of the crosstalk.
The evaluation is the best ◎. TP is 0.8μ as in Examples 2 and 3.
m, the angle becomes slightly smaller than in Example 2 as in Example 3.
When the binary value is smaller in the outer peripheral region than in the inner peripheral region of the disk, the influence of crosstalk is reduced, and the evaluation is the best ◎. When the TP is further reduced to 0.74 μm, the θ1 / θ2 value is gradually or gradually reduced in the outer peripheral region than in the inner peripheral region of the disk as in Example 5 or Example 6 than in Example 4. However, the influence of crosstalk was suppressed, and the evaluation was the best の.

As described above, the present invention relates to an optical disk in which a recording layer is formed by spin coating on a preformat of a transparent substrate having a preformat in which grooves and lands are alternately formed concentrically or spirally on the surface. When the groove is cross-sectioned along the radial direction of the transparent substrate, both side surfaces of the groove of the groove are respectively inclined with respect to a virtual plane parallel to the land of the transparent substrate, and the inner peripheral side surface of the groove is formed. An average taper angle θ1 with respect to the virtual surface is smaller than an average taper angle θ2 of the outer peripheral side surface of the groove with respect to the virtual surface (θ1 <θ2).

By adopting such a configuration, the dent (dent) is reduced, the amount of reflected light is 65% or more at the top level of the CD-R standard, and the crosstalk between adjacent tracks is suppressed. It is possible to provide an optical disk that can prevent deterioration in characteristics and is particularly suitable for high-density recording.

[Brief description of the drawings]

FIG. 1 is a partially enlarged sectional view of an optical disc according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship among an incident angle of an exposure beam to a glass substrate, an exposure intensity, and an inclination angle of a groove groove side surface.

FIG. 3 is an explanatory diagram showing zones 1 to 4 on a transparent substrate.

FIG. 4 is a diagram showing θ0, θ1, θ2 and a track pitch (TP) of each zone on a transparent substrate in each example of the present invention.

FIG. 5 shows θ1 / θ2 of each zone in each example of the present invention.
FIG. 4 is a diagram showing values, track pitches (TP), and evaluation results.

FIG. 6 is a characteristic diagram showing a reflectance in each example of the present invention.

FIG. 7 is a characteristic diagram showing crosstalk in each example of the present invention.

FIG. 8 is a partially enlarged sectional view of a conventional optical disk.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Recording layer 3 Reflective layer 4 Groove 4a Inner side surface of groove 4b Outer side surface of groove 5 Land 6 Depression (dent) 8 Photoresist layer 9 Glass substrate 10 Exposure beam 11 Objective lens 12 Zone 1 13 Zone 2 14 Zone 3 15 Zone 4 X Virtual surface layer parallel to the land θ1 Average taper angle of the groove on the inner peripheral side of the disk on the inner peripheral side θ2 Average taper angle of the groove on the outer peripheral side of the disk on the outer peripheral side of the disk

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yota Matsuki 1-1-88 Ushitora, Ibaraki City, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Inventor Takahiro Otsuka 1-188 Ushitora, Ibaraki City, Osaka Hitachi Within Maxell Co., Ltd. (72) Koichi Otsuka 1-88 Ushitora, Ibaraki-shi, Osaka Prefecture F-term within Hitachi Maxell Co., Ltd. 5D029 JA04 WB03 WB11 WC01 WD10 WD11 WD16

Claims (9)

[Claims] 1. An optical disc in which a recording layer is formed by spin coating on a preformat of a transparent substrate having a preformat in which grooves and lands are alternately formed concentrically or spirally on the surface, wherein the groove is formed on the transparent substrate. When cross-sectioned in the radial direction, both side surfaces of the groove of the groove are respectively inclined with respect to a virtual surface parallel to the land of the transparent substrate, and the average taper of the inner circumferential side surface of the groove with respect to the virtual surface. Angle θ1
However, the optical disk is characterized in that the average taper angle θ2 of the side surface on the outer peripheral side in the groove with respect to the virtual surface is smaller (θ1 <θ2). 2. The optical disc according to claim 1, wherein a value of θ1 / θ2, which is a ratio of θ1 to θ2, is:
An optical disc characterized by being in the range of 0.3 ≦ θ1 / θ2 <1. 3. The optical disk according to claim 1, wherein a value of θ1 / θ2, which is a ratio of θ1 to θ2, is:
An optical disc characterized by being in the range of 0.75 ≦ θ1 / θ2 ≦ 0.9. 4. The optical disk according to claim 1, wherein the value of θ1 / θ2 gradually decreases from the inner region to the outer region of the disk. 5. The optical disk according to claim 1, wherein the optical disk is divided into a plurality of zones from an inner region to an outer region of the disk, and the value of θ1 / θ2 of the outermost zone is the innermost region. Θ1 / θ of the side zone
An optical disc characterized by being smaller than the value of 2. 6. The optical disk according to claim 1, wherein said optical disk is divided into a plurality of zones from an inner region to an outer region of said disk, and said θ1 / θ2
An optical disk characterized in that the value of gradually decreases from the inner peripheral zone to the outer peripheral zone. 7. The optical disk according to claim 1, wherein a track pitch is 0.8 μm or less. 8. The optical disk according to claim 1, wherein a track pitch is 0.74 μm or less. 9. The optical disk according to claim 1, wherein said recording layer contains an organic dye.