JP2007207304A - Optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk which can obtain land pre-pit signals satisfying the standards, and make excellent recording and reproducing. <P>SOLUTION: The optical disk 1 is formed by adhering a first intermediate A which has a first recording layer 3 and a first reflection layer 4 sequentially stacked on a first substrate 2 having first concavo-convex sections 2A, 2B and a second intermediate B which has a second reflection layer 8 and a second recording layer 7 sequentially stacked on a second substrate 9 having second concavo-convex sections 9A, 9B, while making the first reflection layer 4 face the second recording layer 7 side by using a light transmissive adhesive layer 5. Recording and reproducing are made on the first and second recording layers 3, 7 by radiating a laser beam from the side of the first substrate 2. When making the side close to the incident plane 201 the first and second recesses 2A, 9A, the width of the first projection 2B is smaller than the first recess 2A, and the width of the second projection 9B is smaller than the second recess 9A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc having two or more recording layers.

DVDs having two recording layers have been developed for recording and reproducing large amounts of information.
In Patent Document 1, a first intermediate body in which a first recording layer and a first reflective layer are sequentially laminated on a first substrate having a recess width of 0.2 to 0.3 μm, and a recess width is described. The first reflective layer and the barrier described above include a second intermediate layer in which a second reflective layer, a second recording layer, and a barrier layer are sequentially laminated on a second substrate having a thickness of 0.2 to 0.4 μm. An optical disc is described in which a layer is disposed so as to face each other with a transparent intermediate layer interposed therebetween. The first reflective layer is made of an alloy containing at least one selected from Au, Ag, Cu and the like as a main component, and has a light transmittance of 30 to 60%. In addition, it is described that the light reflectance is 15 to 35%.

Further, by focusing the laser beam on the first recording layer and the second recording layer from the first substrate side of the optical disc, information can be recorded on each recording layer or the information can be reproduced. .
Since the surfaces of the first and second substrates are convex with respect to the concave portions, the first and second substrates are provided with concave and convex portions. Hereinafter, the first and second substrates will be described. The side close to the laser light incident surface of the substrate is referred to as a recess.
At this time, the first and second recording layers formed on the concave portions of the first and second substrates become the first and second information recording layers.
Japanese Patent Laid-Open No. 2005-50497

  When the information light obtained by irradiating the second information recording layer of the second substrate with the laser beam through the first substrate and detecting the reflected light is detected by the photodetector, The information light transmitted through the formed concave portion and the information light transmitted through the convex portion interfere with each other to generate high-order diffracted light. By the way, in the prior art, the width of the concave portion formed on both the first and second substrates is equal to the width of the convex portion. And since the light quantity of the information light irradiated to the uneven | corrugated | grooved part formed in the 1st board | substrate becomes equal, the high order diffracted light by interference becomes most easy to produce. Since the high-order diffracted light disturbs the light receiving state of the photodetector, a good reproduction signal could not be obtained.

  In order to easily record information from the second information recording layer, a semi-transmissive film made of metal or alloy is usually used for the first reflective layer. Since it is easy to generate folding light, it has become a factor causing the same problem as described above.

  The diffracted light also affects the land pre-pit signal formed on the convex portion adjacent to the second information recording layer of the second substrate, and the AR (aperture ratio) value of the land pre-pit signal is lowered. There was a problem such as. The AR value is a value indicating an index from which the land pre-pit signal can be read.

The AR value of the land pre-pit signal is required to be 10% or more according to the standard.
Among the information signals obtained from the second recording layer, in particular, the land prepit signal obtained from the land prepit is very small as compared with the reproduction information signal, and thus may not satisfy the standard value. The same applies to recording.

  Therefore, the present invention has been proposed in view of the above-described problems, and an object of the present invention is to provide an optical disc that can obtain a land pre-pit signal that satisfies a standard value and that can perform good recording and reproduction. To do.

  The present invention relates to an optical disc that records or reproduces information by irradiating a recording or reproducing laser beam, and has an incident surface of the laser beam, and a first concave portion and a first convex portion are formed. A first intermediate body in which at least a first recording layer and a first reflective layer are sequentially stacked on a first substrate that is light transmissive, and a second intermediate portion formed with a second concave portion and a second convex portion. A second intermediate layer in which at least a second reflective layer and a second recording layer are sequentially laminated on the substrate, wherein the first reflective layer faces the second recording layer, The first intermediate body and the second intermediate body are bonded together, and in the first intermediate body, the side close to the incident surface in the first uneven portion is defined as the first concave portion, and the second intermediate body is formed. In the intermediate body, when the second concave portion is the second concave portion on the side close to the incident surface, the first concave portion Narrower than the width of the convex portion of the first recess, and the width of the second projecting portion is to provide an optical disc, characterized in that narrower than said second recess.

  According to the present invention, since the width of the first concave portion is narrower than that of the first convex portion and the width of the second convex portion is narrower than that of the second concave portion, the land prepits satisfying the standard value. A signal can be obtained and good recording and reproduction can be performed.

Hereinafter, embodiments of the optical disk according to the present invention will be described in detail with reference to FIGS.
1A and 1B show an optical disc according to an embodiment of the present invention, in which FIG. 1A is a cross-sectional view thereof, FIG. 1B is a cross-sectional view of MM in FIG. 1A, and FIG.
FIG. 2 is a diagram showing a method for producing the first intermediate. FIG. 3 is a diagram showing a method for producing the second intermediate. FIG. 4 is a sectional view showing the bonding of the first and second intermediates.

  As shown in FIG. 1, an optical disc 1 includes a first recording layer 3 and a first recording layer 1 on a first substrate 2 having disc-shaped first uneven portions 2A and 2B on the recording / reproducing laser beam irradiation side. The second reflective layer 8, the second recording layer 7, and the second intermediate layer 9 having the first intermediate body A and the second concave-convex portions 9A and 9B in which the reflective layers 4 are sequentially laminated. The second intermediate body B in which the light-transmitting protective layer 6 is sequentially laminated is pasted with the first reflective layer 4 and the light-transmitting protective layer 6 disposed opposite to each other with the light-transmitting adhesive layer 5 interposed therebetween. Are combined.

  Hereinafter, of the first and second concave and convex portions 2A, 2B, 9A, and 9B formed on the first and second substrates 2 and 9, a concave portion is formed on the side closer to the incident surface 201 of the recording / reproducing laser beam. The far side is called the convex part. The concave portion is referred to as a groove, and the convex portion is referred to as a land. That is, in FIG. 1, the grooves are 2A and 9A, and the lands are 2B and 9B. Information is recorded in the first and second recording layers 3 and 7 on the grooves 2A and 9A. The areas of the first and second recording layers 3 and 7 on the grooves 2A and 9A in which this information is recorded are referred to as information recording areas 3A and 7A, respectively. Further, land pre-pits 2C and 9C indicating auxiliary information are formed on the lands 2B and 9B.

  Grooves 2A and lands 2B are alternately formed adjacent to each other on the surface of the first substrate 2. As shown in FIG. 1B, the lands 2B indicate auxiliary information such as addresses and synchronization signals. Land pre-pits 2C are formed. Specifically, the land pre-pit 2C is formed as a pattern having the same height as the land 2B.

That is, the land pre-pits 2C are formed as pits that are recessed portions scattered in the lands 2B.
The groove 2A and the land 2B are formed in a spiral shape that is continuous from the inner periphery toward the outer periphery or from the outer periphery toward the inner periphery. Further, both sides of the groove 2A are wobbled, and the first information is recorded on and reproduced from the information recording area 3A of the first recording layer 3 formed on the groove 2A.

  Grooves 9A and lands 9B are alternately formed adjacent to each other on the surface of the second substrate 9 facing the first substrate 2, and as shown in FIG. A pit 9C is formed. Specifically, the land pre-pit 9C is formed as a pattern having the same height as the groove 9A.

  That is, the land pre-pits 9C are formed as pits having a shape protruding from the land 9B, and are scattered at intervals defined by the standard. The groove 9A and the land 9B are formed in a spiral shape that is continuous from the inner periphery toward the outer periphery or from the outer periphery toward the inner periphery, similarly to the groove 2A and the land 2B. Further, both sides of the groove 9A are wobbled, and the second information is recorded on and reproduced from the information recording area 7A of the second recording layer 7 formed on the groove 9A.

  As the first substrate 2, a light transmissive material such as polycarbonate resin, polymethacrylate resin, or amorphous polyolefin resin can be used. The second substrate 9 is not necessarily arranged to be light transmissive because it is not disposed on the recording / reproducing laser beam irradiation side, but the same material as the first substrate 2 is preferably used.

  As the first and second recording layers 3 and 7, cyanine dyes, phthalocyanine dyes, and azo dyes that are soluble in alcoholic or cellosolve solvents that are polar solvents can be used. The surface of the second recording layer 7 is flattened.

  Cyclic amorphous polyolefin (for example, trade name ZEONEX or QUINTON (Nippon Zeon Co., Ltd.) can be used as the light-transmitting protective layer 6. When the above-described material is used for the first recording layer 3, an organic material is used. Non-polar solvents such as cyclohexane, tetralin, and decalin are used as solvents that do not dissolve pigments, and cyclic amorphous polyolefins (for example, trade names such as Zeonex and Quinton (Nippon Zeon Corporation) are used as transparent resins that can be dissolved in nonpolar solvents. And can be formed by a spin coating method or the like.

  Further, a semi-transmissive metal reflective layer or an inorganic transparent thin film layer may be used for the light transmissive protective layer 6. At this time, the light-transmitting protective layer 6 may have a function of adjusting the optical transmittance, and by selecting the refractive index n, the absorption coefficient k, and the thickness with respect to the wavelength of the laser light to be recorded and reproduced, It is possible to adjust the reflectance and tracking signal of the second recording layer 7.

Specifically, the light-transmitting protective layer 6 includes ZnS (n = 2.4), SiC (n = 2.2), TiO ₂ (n = 2.5), SiN (n = 2.1). An inorganic dielectric film of sulfide, oxide, or nitride such as ZnS—SiO ₂ (n = 2.1) can be used. Furthermore, the refractive index n of the light-transmitting protective layer 6 can be increased by using a mixture of metal and ceramic fine particles in an ultraviolet curable resin as the light-transmitting protective layer 6.

Furthermore, the light-transmitting protective layer 6 may have a two-layer structure using both the light-transmitting resin thin film layer such as the above-mentioned cyclic amorphous polyolefin and a semi-transmissive metal reflective layer or an inorganic transparent thin film layer.
For the first and second reflective layers 4 and 8, Au, Al, Ag, or an alloy thereof can be used because high reflectance can be obtained.

  For the light-transmitting adhesive layer 5, it is preferable to use an acrylate-based ultraviolet curable resin from the viewpoint of productivity and yield. As the ultraviolet curable resin, for example, an ultraviolet curable resin mainly composed of epoxy acrylate, urethane acrylate, and a mixture thereof is preferable.

Relationship between the width L ₂ of the width L ₁ of the first recess 2A first convex portion 2B is L _1> L _2. Also, the width L ₃ of the second recess 9A relationship between the width L ₄ of the second convex portions 9B is a L _3> L _4. In other words, the width L _{1 of the} groove 2A is wider than the width L _{2 of the} land 2B, and the width L _{3 of the} groove 9A is wider than the width L _{4 of the} land 9B. Since the width L _{1 of the} groove 2A is wider than the width L _{2 of the} land 2B, the interference of the higher-order diffracted light that is diffracted by the groove 2A by the recording / reproducing laser beam reflected by the information recording area 7A of the second recording layer 7 Can be weakened. For this reason, it is possible to easily detect the recording / reproducing laser beam reflected by the information recording area 7A by a photodetector (not shown), so that good recording / reproducing can be performed.

Further, since the width L _{3 of the} groove 9A is wider than the width L _{4 of the} land 9B, the spread of heat of the recording / reproducing laser beam on the second recording layer 7 can be suppressed, so that the land pre-pit signal is detected. Easy to do. However, if the widths L ₂ and L 4 of the lands 2B and 9B are made too narrow, it becomes difficult to detect the land pre-pit signals from the land pre-pits 2C and 9C.

For this reason, the ratio of the width L ₁ of the first recess 2A to 60% is 70 to 70% with respect to one track width (L ₁ + L ₂ ) of the first protrusion 2B adjacent to the first recess 2A. Is preferred.
Further, the ratio of the width L ₃ of the second recess 9A to one track width (L ₃ + L ₄ ) is preferably 50 to 70%.
By setting the groove width in this way, it becomes possible to easily detect the recording / reproducing laser beam reflected by the land pre-pit 9C by a photodetector (not shown), and the signal of the land pre-pit 9C that satisfies the standard value. Can be obtained.

Next, a method for manufacturing the optical disc 1 will be described with reference to FIGS.
(First glass master production process for substrate)
As shown in FIG. 2A, a photoresist 11 is applied on a disk-shaped glass substrate 10. As shown in FIG. 2 (B), the photoresist 11 is irradiated with a laser beam for exposure and then developed, and the groove 2A and land 2B described with reference to FIGS. 1 (A) and 1 (B) are developed. And the photoresist pattern 12 used as the land prepit 2C formed on the land 2B is formed toward the outer periphery from the inner periphery, and the glass master 13 is produced. At this time, both sides of the photoresist pattern 12 are wobbled. The photoresist pattern 12 corresponding to the groove 2A is formed as one spiral concave portion that is continuous from the inner periphery toward the outer periphery or from the outer periphery toward the inner periphery.

(Process for producing the first substrate master stamper)
As shown in FIG. 2 (C), after forming Ni of 50 to 200 nm in thickness on the glass master 13 by sputtering, a plating film of 100 to 500 μm in thickness is formed by electroforming. The master stamper 14 is produced by transferring the photoresist pattern 12 formed on the master 13. The pattern formed on the master stamper 14 has a reverse relationship to the photoresist pattern 12 formed on the glass master 13.

(First substrate manufacturing process)
Next, the master stamper 14 is mounted on an injection molding machine (not shown), and as shown in FIG. 2 (D), from the inner periphery to the outer periphery or from the outer periphery to the inner periphery by the injection molding method. Thus, the first substrate 2 in which the land 2B on which the groove 2A and the land pre-pit 2C are formed is formed in a spiral shape is obtained.

(First recording layer forming step)
Next, as shown in FIG. 2E, an organic dye dissolved in an alcohol solvent is applied onto the first substrate 2 by a spin coating method to obtain the first recording layer 3. Actually, the first recording layer 3 is thicker in the groove 2A than on the land 2B. This is because the organic dye flows and accumulates in the groove 2A which is lower than the land 2B. For this reason, no organic dye is formed on the side walls of the land 2B and the land prepit 2C.

(First reflective layer forming step)
Next, as shown in FIG. 2F, the first reflective layer 4 is formed on the first recording layer 3 by sputtering or vacuum deposition.
Thus, the first intermediate A is produced.

(Manufacturing process of master stamper for second substrate)
Next, as shown in FIG. 3A, a photoresist 11 is applied on a disk-shaped glass substrate 15. As shown in FIG. 3 (B), the photoresist 11 is irradiated with laser light to be exposed and developed, and then the grooves 9A and lands 9B described with reference to FIGS. 1 (A) and 1 (C) are used. A glass master 17 is produced by forming a photoresist pattern 16 to be land prepits 9C formed on the lands 9B from the inner periphery toward the outer periphery or from the outer periphery toward the inner periphery. At this time, both sides of the photoresist pattern 16 are wobbled.

(Manufacturing process of master stamper for second substrate)
The photoresist pattern 16 corresponding to the groove 9A is formed as one spiral concave portion that is continuous from the inner periphery toward the outer periphery or from the outer periphery toward the inner periphery. As shown in FIG. 3 (C), Ni having a thickness of 50 to 200 nm is formed on the glass master 17 by sputtering, and then an Ni plating film having a thickness of 100 to 500 μm is formed by electroforming. The stamper 18 is produced. The pattern of the master stamper 18 has a reverse relationship with the glass master 17.

(Mother stamper manufacturing process)
Next, after separating the master stamper 18 from the glass master 17, as shown in FIG. 3D, an Ni plating film is formed on the master stamper 18 by electroforming, thereby forming the master stamper 18. The mother stamper 19 is produced by transferring the pattern. The pattern of the mother stamper 19 has the same relationship as that of the glass master 17.

(Second substrate manufacturing process)
Next, the mother stamper 19 is mounted on an injection molding machine (not shown), and as shown in FIG. 3 (E), the groove 9A and the land pre-pit 9C are formed from the inner periphery toward the outer periphery by an injection molding method. The second substrate 9 in which the formed land 9B is spirally formed is obtained.

(Second reflection layer forming step)
Next, as shown in FIG. 3F, the second reflective layer 8 is formed over the second substrate 9 by sputtering or vacuum evaporation.

(Second recording layer forming step)
Next, as shown in FIG. 3G, an organic dye dissolved in an alcohol solvent is applied onto the second reflective layer 8 by spin coating to obtain the second recording layer 7. The thickness of the second recording layer 7 on the groove 9A is made larger than the height of the land 9B. As a result, the unevenness of the surface of the second recording layer 7 is reduced and flattened than the step formed by the groove 9A and the land 9B.

(Process for forming light-transmitting protective layer)
Next, as shown in FIG. 3H, a light-transmitting protective layer is formed by applying a light-transmitting resin made of a thermoplastic resin dissolved in a nonpolar solvent on the second recording layer 7 by spin coating. 6 is formed. In this way, the second intermediate B is produced.

(Lamination process)
As shown in FIG. 4, after the light transmissive adhesive layer 5 made of an ultraviolet curable resin is applied on the first light transmissive protective layer 4 of the first intermediate A, the light transmissive protective layer 6 side is attached. The second intermediate B is placed on the light transmissive adhesive layer 5 so as to face the light transmissive adhesive layer 5. In this state, the first and second intermediates A and B are rotated to spread the light-transmitting adhesive layer 5 over the entire surface, and then cured by irradiating with ultraviolet rays to form two layers on one side shown in FIG. An optical disc 1 having a recording layer is prepared.

  In addition, you may use the adhesive sheet in which the adhesive material was formed in the single side | surface of a peeling sheet instead of ultraviolet curable resin. In this case, the adhesive material side is opposed to the first reflective layer 4 of the first intermediate A, the pressure-sensitive adhesive sheet is pressed and removed from the first intermediate A, and then peeled off. Only the sheet is peeled off, and the second intermediate body B is overlaid on the adhesive material described above with the light-transmitting protective layer 6 side facing the adhesive material. Furthermore, the optical disc 1 having two recording layers on one side can be manufactured by applying pressure, removing and bonding.

Next, Example Sample 1 and Comparative Samples 1 and 2 were prepared by changing the material of each layer in the optical disc 1, and the recording / reproducing characteristics were examined.
Each sample of the optical disk 1 was produced as follows.
The material of the first and second substrates 2 and 9 used here is a polycarbonate resin.

(Example sample 1)
First, the first intermediate A is prepared.
Using the master stamper 14, a groove 2A having a track pitch of 0.74 μm, a depth of 160 nm and a width of 0.25 μm, a land 2B having a height from the bottom of the groove 2A of 160 nm and a width of 0.49 μm, and a land 2B Then, a first substrate 2 having a thickness of 0.6 mm is formed in which land prepits 2C having a pattern of 160 nm having the same height as the land 2B are formed. Next, a cyanine dye having a maximum absorption wavelength of 585 nm (trade name S06-DX001, manufactured by Hayashibara Biochemical Laboratories) is dissolved in tetrafluoropropanol, and a 1.0 wt% solution is prepared by spin coating to form the first substrate. 2 is applied to form the first recording layer 3. At this time, the first substrate 2 is rotated at 1500 rpm.

  The thickness of the first recording layer 3 formed in this way is 120 nm on the groove 2A and 30 nm on the land 2B. A first reflective layer 4 made of Ag having a thickness of 10 nm is formed on the first recording layer 3 by sputtering. In this way, the first intermediate A is produced.

Next, the 2nd intermediate body B is produced.
Using the mother stamper 19, a groove 9A having a track pitch of 0.74 μm, a depth of 30 nm and a width of 0.44 μm, a land 9B having a height from the bottom surface of the groove 9A of 30 nm and a width of 0.3 μm, and a land 9B Then, a second substrate 9 having a thickness of 0.6 mm in which a land pre-pit 9C having a pattern of 30 nm having the same height as the groove 9A is formed.
A second reflective layer 8 made of Ag having a thickness of 100 nm is formed on the second substrate 9 by sputtering.

  A cyanine dye having a maximum absorption wavelength of 585 nm in a dichloromethane solution (trade name S06-DX001, manufactured by Hayashibara Biochemical Laboratories) is dissolved in tetrafluoropropanol to form a 1.5 wt% solution by spin coating. The second recording layer 7 is formed by coating on the reflective layer 8 so that the thickness on the groove 9A is 120 nm. At this time, the second substrate 9 is rotated at 1000 rpm.

Next, the light-transmitting protective layer 6 made of a 20 nm thick ZnS—SiO ₂ (ZnS: SiO ₂ = 20: 80 mol%) thin film is formed by RF sputtering.
In this way, the second intermediate B is produced.

Next, the first and second intermediates A and B are bonded together.
A light transmissive adhesive layer 5 made of an ultraviolet curable resin (manufactured by Nippon Kayaku Co., Ltd .: acrylate (trade name) DVD1142) is applied on the first reflective layer 4 of the first intermediate A, and then light transmissive. The second intermediate body B is overlaid on the light-transmitting adhesive layer 5 with the transparent protective layer 6 side facing the light-transmitting adhesive layer 5. In this state, the first and second intermediates A and B are rotated at a rotational speed of 6000 rpm so that the entire light-transmitting adhesive layer 5 having a thickness of 50 μm is spread, and then cured by irradiation with ultraviolet rays. At this time, the ultraviolet curable resin used as the light-transmitting adhesive layer 5 is modified urethane acrylate (trade name World Rock No. 811) manufactured by Kyoritsu Chemical Industry Co., Ltd.
Thus, the optical disc 1 of Sample 1 having two recording layers 3 and 7 on one side was produced.

(Comparative sample 1)
The comparative sample 1 is the same as the example sample 1 except that the widths of the grooves 9A and the lands 9B of the second intermediate B are the same and the widths of the grooves 2A and the lands 2B of the first intermediate A are equal. The rest is the same.
Hereinafter, a method for manufacturing the comparative sample 1 will be described.
First, the first intermediate A is prepared.
Using the master stamper 14, the groove 2A having a track pitch of 0.74 μm, a depth of 160 nm and a width of 0.37 μm, a land 2B having a height from the bottom surface of the groove 2A of 160 nm and a width of 0.37 μm, and a land 2B A first substrate 2 having a thickness of 0.6 mm on which land pre-pits 2C having a pattern of 160 nm having the same height as the land 2B are formed.

  Next, a cyanine dye having a maximum absorption wavelength of 585 nm (trade name S06-DX001, manufactured by Hayashibara Biochemical Laboratories) is dissolved in tetrafluoropropanol, and a 1.0 wt% solution is prepared by spin coating to form the first substrate. The first recording layer 3 having a thickness of 50 nm is formed by coating on the substrate 2. At this time, the first substrate 2 is rotated at 1500 rpm.

  A first reflective layer 4 having a thickness of 10 nm is formed on the first recording layer 3 by sputtering in Ar gas using a target of an alloy containing Ag as a main component by DC sputtering. In this way, the first intermediate A is produced.

Next, the 2nd intermediate body B is produced.
Using the mother stamper 19, a groove 9A having a track pitch of 0.74 μm, a depth of 30 nm and a width of 0.29 μm, a land 9B having a height from the bottom of the groove 9A of 30 nm and a width of 0.45 μm, and a land 9B Then, a second substrate 9 having a thickness of 0.6 mm in which a land pre-pit 9C having a pattern of 30 nm having the same height as the groove 9A is formed.
A second reflective layer 8 made of an Ag alloy film having a thickness of 100 nm is formed on the second substrate 9 by sputtering.

  A cyanine dye having a maximum absorption wavelength of 585 nm in a dichloromethane solution (trade name S06-DX001, manufactured by Hayashibara Biochemical Laboratories) is dissolved in tetrafluoropropanol to form a 1.5 wt% solution by spin coating. A second recording layer 7 made of an organic dye having a thickness of 120 nm is applied on the reflective layer 8. At this time, the second substrate 9 is rotated at 1000 rpm.

Next, the light-transmitting protective layer 6 made of a 20 nm thick ZnS—SiO ₂ (ZnS: SiO ₂ = 20: 80 mol%) thin film is formed by RF sputtering.
In this way, the second intermediate B is produced.

  Next, similarly to Example Sample 1, the first and second intermediates A and B were bonded together to produce the optical disc 1 of Comparative Sample 1 having two recording layers 3 and 7 on one side. .

(Comparative sample 2)
The comparative sample 2 is the same as the example sample 1 except that the groove width and land width of the first intermediate A are kept as they are, the groove width of the second intermediate B is 0.35 μm, and the land width is 0.39 μm. Other than this is the same.
Since the manufacturing method of the comparative sample 2 is the same as that of Example sample 1, description is abbreviate | omitted.

(Recording / playback evaluation)
The optical disk 1 of Example Sample 1 and Comparative Samples 1 and 2 thus obtained was set in an optical disk evaluation machine equipped with an optical pickup that emits laser light having a numerical aperture of 0.65 and a wavelength of 650 nm. The characteristics were investigated. A DVD format signal is recorded in the information recording area 3A of the first recording layer 3 of each sample with a laser light power of 20 mW, and the information recording area 7A of the second recording layer 7 is recorded with a laser light power of 23 mW. A DVD format signal was recorded.

(Evaluation results of Example Sample 1)
In the information recording area 3A of the first recording layer 3, the reproduction jitter is 7.8% and the reflectance is 18%. In the information recording layer 7A of the second recording layer 7, the reproduction jitter is 8.0%. The reflectance was 18%.
The AR value indicating the quality of the land pre-pit detection signal was 26%. The DVD standard specifies that the reproduction jitter is 8% or less, the reflectance is 16% or more, and the AR value is 10% or more. As described above, it was found that the reproduction jitter, the reflectance, and the AR value all satisfy the standard values, and a good recording layer is formed.

(Evaluation result of comparative sample 1)
In the information recording area 3A of the first recording layer 3, the reproduction jitter, the reflectance, and the AR value were the same as those of the example sample 1.
In the information recording area 7A of the second recording layer 7, the reproduction jitter was 7.8%, the reflectance was 17.8%, and the AR value was 0%.
Although the reproduction jitter and reflectance satisfy the standard values, the AR value does not satisfy the standard values, and land pre-pit detection with good signal quality could not be performed.

(Evaluation result of comparative sample 2)
In the information recording area 7A of the second recording layer 7, the reproduction jitter and reflectance were the same as those of the comparative sample, but the AR value was 8%.
Thus, like the comparative sample 1, the AR value did not satisfy the standard value, and land pre-pit detection with good signal quality could not be performed.
As described above, the width of the groove 2A in the first recording layer 3 is made wider than the width of the land 2B, and the width of the groove 9A in the second recording layer 7 is made wider than the width of the land 9B. An AR value satisfying the value can be obtained, and good recording and reproduction can be performed.

It is a figure which shows the optical disk in embodiment of this invention. It is a figure which shows the manufacturing method of a 1st intermediate body. It is a figure which shows the manufacturing method of a 2nd intermediate body. It is sectional drawing which shows bonding of the 1st, 2nd intermediate body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... 1st board | substrate, 2A, 9A ... Groove, 2B, 9B ... Land, 2C, 9C ... Land pre-pit, 3 ... 1st recording layer, 3A, 7A ... Information recording area, 4 ... 1st DESCRIPTION OF SYMBOLS 1 Reflective layer, 5 ... Light transmissive adhesive layer, 6 ... Light transmissive protective layer, 7 ... Second recording layer, 8 ... Second reflective layer, 9 ... Second substrate, 10, 15 ... Glass Substrate, 11 ... Photoresist, 12, 16 ... Photoresist pattern, 13 ... Glass master, 14, 18 ... Master stamper, 19 ... Mother stamper, A ... First intermediate, B ... Second intermediate, 210 ... Incident surface

Claims (1)

In an optical disc that records or reproduces information by irradiating a recording or reproducing laser beam,
At least a first recording layer and a first reflective layer are sequentially stacked on a light-transmitting first substrate having the laser light incident surface and having a first concave portion and a first convex portion. A first intermediate,
A second intermediate body in which at least a second reflective layer and a second recording layer are sequentially laminated on a second substrate on which a second concave portion and a second convex portion are formed;
The first intermediate body and the second intermediate body are bonded so that the first reflective layer faces the second recording layer,
In the first intermediate body, a side close to the incident surface in the first uneven portion is defined as the first concave portion, and in the second intermediate body, a side close to the incident surface in the second uneven portion is defined as the first concave portion. When making the second recess,
An optical disc, wherein the width of the first convex portion is narrower than that of the first concave portion, and the width of the second convex portion is narrower than that of the second concave portion.

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