JP4609782B2 - optical disk - Google Patents

Description

  The present invention relates to an optical disc, and more particularly to an optical disc in which information of a plurality of standards having different recording densities is recorded on the same disc and can be reproduced in a compatible manner.

With the rise of multimedia and the like, there has been a demand for handling large volumes of information such as digital moving images, and there has been an increasing demand for optical recording media (optical disks) capable of storing large volumes of information. And the demand for the recording capacity of this optical recording medium (optical disk) is increasing in the direction of increasing capacity. For example, the recording capacity of CD (compact disc) was 650 MB (megabyte) level, but with the advent of DVD, its storage capacity has been expanded to 4.7 GB (gigabyte) level for single-sided single-layer discs, for example. .

  At present, a plurality of “next-generation high-density recording optical disks” capable of high-capacity recording of 20 GB level by shortening the wavelength of the light source as shown in FIG. 8 have been proposed (for example, the 1999 Autumn Society of Applied Physics). Academic Lecture Proceedings, 2p-ZY-7, 3p-ZC-1 and 2).

  The next-generation high-density recording optical disk shown in FIG. 8 has a concavo-convex shape portion formed on the outermost surface of a suitable substrate 1, and deposits a reflective film layer made of a metal thin film such as aluminum (Al), like CD, The high-density recording area 3a is used. After the formation of the high density recording area 3a, a protective layer (using a sheet or the like) 6 having a thickness of about 100 to 120 μm is provided on the high density recording area 3a. When reproducing the next-generation high-density recording optical disk shown in FIG. 8, laser light (high-density recording area reading light) 9 having a wavelength λ = 410 nm band is applied from the protective layer 6 side to a numerical aperture (NA) = 0.7. The light is condensed and irradiated using a lens of about ~ 0.85, and the information recorded in the high-density recording area 3a is read from the reflected light. In the next-generation high-density recording standard optical disk shown in FIG. 8, the thickness tp of the medium that is transmitted during reading, that is, the protective layer 6 is set to about tp <100 to 200 μm mainly for the purpose of preventing the occurrence of aberration due to the substrate tilt. A plurality of methods have been proposed in which a thin film is reproduced by irradiating with high-density recording area reading light 9 through a protective layer 6. That is, a plurality of structures that have been optically designed so that the high-density recording area reading light 9 does not pass through the thick main substrate (high-density optical disk substrate) 1 have been proposed.

If a high-density optical recording medium at the level of the next-generation high-density recording optical disk shown in FIG. 8 becomes commercially available, the current DVD will be regarded as a medium-density optical recording medium.
In the market, a low density optical recording medium such as a CD, a medium density optical recording medium such as a DVD, and a high density optical recording medium as described above will be mixed, and a plurality of standards will coexist. is expected.

  FIG. 7 is a cross-sectional view showing an example of the structure of a CD. As shown in FIG. 7, the CD has a concavo-convex shape portion on the surface of the transparent substrate 1 having a thickness tD = 1.2 mm ± 0.1 mm and a diameter of 12 cm or 8 cm, and a total reflection film such as aluminum (Al). The recording area 3b is formed by depositing layers (in the present invention, a recording area corresponding to a CD is hereinafter referred to as a “low density recording area” 3b). A protective layer 6 is usually formed on the outermost surface. When reproducing the CD shown in FIG. 7, a laser beam having a wavelength λ = 780 nm band (low density recording) from the back side of the transparent substrate (first substrate) 1 on which the concavo-convex portion (low density recording region) 3b is formed. (Region reading light) 10 is condensed and irradiated using a lens having an NA of about 0.45, and information recorded in the concavo-convex shape portion (low density recording region) 3b is read from the reflected light.

  On the other hand, in a DVD having a recording density intermediate between FIGS. 7 and 8 (in the present invention, a recording area corresponding to a DVD is hereinafter referred to as “medium density recording area”), the two substrates are bonded together. Since it is assumed, it is somewhat difficult to create an optical disc compatible with other standards.

  FIG. 9 shows an example of a DVD double-layer optical disc. Recording pits are formed on the respective surfaces of the transparent first substrate 13 and the second substrate 11 having a thickness ts = 0.6 mm and a diameter of 12 cm. A semitransparent film is formed on the second substrate 11 side. A total reflection film layer similar to a CD or the like is formed on the substrate 13 side, and bonding is performed via a transparent adhesive layer 16. The distance between the two layers at this time is defined as 55 ± 15 μm in the standard. At the time of reproduction, the first recording area reading light 15b and the second recording area reading light 15a using a laser beam having a wavelength of 650 nm are applied from the side of the second substrate 11 on which the semitransparent film is formed, with NA = 0. The information is recorded in the first recording area 14 and the second recording area 12 from the reflected light. Both the first recording area 14 and the second recording area 12 can be reproduced by selecting a layer by a lens focusing operation.

  In the case of a DVD single-layer optical disc, the upper first substrate 13 is a flat plate, recording pits are formed only on the lower second substrate 11, and a total reflection film layer is formed on the recording pits. .

  Thus, at present, low density optical recording media such as CDs and medium density optical recording media such as DVDs are mixed. Many technologies for reproducing low-density recording standard and medium-density recording standard optical disks with the same reproducing apparatus have been announced for the purpose of avoiding complicated handling of users and duplication of reproducing apparatuses. That is, even in a DVD playback device, a compatible playback function with a CD that is a prior standard is virtually essential.

  For this reason, on the reproducing apparatus side, a plurality of light sources and an optical system adapted to a plurality of substrate thicknesses have been developed. At the same time, on the optical disc side, an attempt to realize such compatibility has been started. For example, as an optical disc for medium density music that has begun to be commercialized as “Super Audio CD (SACD)”, an optical disc having a multilayer structure called “hybrid SACD” as shown in FIG. (See Kaihei 9-91752). In this hybrid SACD, the two substrates of the first substrate 19 and the second substrate 21 are bonded to each other, and a medium density recording region 20 is provided in the middle, and a CD standard low density recording region 22 is provided in the uppermost layer. Allows for compatibility. That is, a concavo-convex shape portion is formed on the surface of the transparent first substrate 19 having a thickness tS = 0.6 mm and a diameter of 12 cm, a semi-transparent film is deposited on the concavo-convex shape portion, and the medium density recording region 20 is formed. Forming. Further, a concavo-convex shape portion is formed on the surface of the transparent second substrate 21 having a thickness of 0.6 mm and a diameter of 12 cm, which is the same as that of the first substrate 19, and the same as CD or the like is formed on the concavo-convex shape portion. A total reflection film layer is deposited to form a low density recording area 22. Then, the first substrate 19 and the second substrate 21 are bonded together with a transparent adhesive layer 16. It is basically the same as the DVD double-layer optical disc shown in FIG. 9 in that the two substrates are bonded together. However, in the hybrid SACD, the concavo-convex shape portion (low density recording region) 22 is positioned on the uppermost portion of the upper second substrate 21, and the medium density recording region 20 is positioned on the uppermost portion of the lower first substrate 19. And the direction of each substrate is aligned. Thus, the uppermost uneven portion layer (low density recording area) 22 is formed with an uneven portion conforming to the CD standard, and the medium density recording region 20 is formed at the center of the optical disc. There are two methods of reproducing the hybrid SACD shown in FIG.

  (A) At the time of reproduction as SACD, laser light (medium density recording area reading light) 15c having a wavelength λ = 650 nm band is applied from the side of the first substrate 19 on which the medium density recording area 20 made of a translucent film is formed. , The light is condensed and irradiated using a lens with NA = 0.6, and the information recorded in the medium density recording area 20 is read from the reflected light. That is, it is a playback method equivalent to DVD.

  (B) On the other hand, although the recording density (information amount) as an SACD cannot be obtained, it can be reproduced as a CD. At the time of this reproduction, laser light (low-density recording area reading light) 10 having a wavelength λ = 780 nm band is condensed and irradiated from the first substrate 19 side using a lens with NA = 0.45. Read information from reflected light.

  Thus, if the hybrid SACD shown in FIG. 10 is played back using a CD playback device, playback can be performed with the hybrid SACD regarded as a normal CD. In this way, if the hybrid SACD method is used, the same content can be stored on one optical disk by using two types of conventional CD and SACD (high quality sound). This has the advantage that compatible playback is possible even with a conventional CD playback device (which has become widespread). For this reason, the consumer can purchase one piece of the same content regardless of the playback device.

As described above, when the next generation high-density recording standard that is higher in density than the current DVD standard appears due to the demand for high density and large capacity, the “low density recording standard” equivalent to the current CD and “ In addition to “medium density recording standard”, the third standard of “high density recording standard” will be added. Accordingly, not only does the playback apparatus become complicated, but there is also a risk of hindering the supply of content to only a CD playback apparatus that has been widely used in the past or a user who has only a DVD playback apparatus.

The hybrid SACD shown in FIG. 10 is capable of supplying content with CD quality to a user who has only a CD playback device. However, since the first substrate 19 having a medium density recording area 20 equivalent to a DVD and the second substrate 21 having a low density recording area 22 equivalent to a CD are independently manufactured and bonded, There is a disadvantage that the manufacturing cost is high. That is, both the CD manufacturing cost and the SACD manufacturing cost are superimposed, resulting in a high cost. Therefore, in reality, the software production (software manufacturer) cannot obtain the consent, and the hybrid SA as a product
There is virtually no CD.

  In addition, in order to reproduce a plurality of layers from the same surface direction, the medium density recording region 20 needs to be a semi-transmissive layer, which causes deterioration in characteristics due to a decrease in reflectance. When a wavelength selective film is used for this solution, there is a further disadvantage that the cost is increased.

  In addition, in the optical disc, the thickness t of the light transmission layer through which the reading light passes needs to be strictly controlled. Therefore, in the hybrid SACD shown in FIG. 10 or the DVD dual-layer disc shown in FIG. It is necessary to strictly control the thickness of each layer including the thickness, and the total thickness, which causes high costs. That is, the thickness error Δt of the light transmission layer thickness t has an upper limit depending on the design center of the objective lens, the NA value, the wavelength λ of the reading light, and the like. The amount of aberration given to the spot by the thickness error Δt of the light transmission layer is defined by the NA value and the wavelength λ of the reading light. Specifically, as a request from the system side, in the case of CD, when NA = 0.45, the upper limit (standard) of the thickness error ΔtCD of the light transmission layer is ± 100 μm. In the case of DVD, at NA = 0.6, the upper limit (standard) of the light transmission layer thickness error ΔtDVD is ± 30 μm. In the case of the DVD dual-layer disc shown in FIG. 9, the interval Δd = 55 ± 15 μm of the adhesive layer 16 is defined as a standard because Δd needs to be within 2 | ΔtDVD | = 60 μm. .

  The reproduction compatibility problem corresponding to the situation where the optical discs of the CD standard and the DVD standard coexist is a practical use of the next generation high density recording standard in which the current DVD standard is regarded as a medium density recording standard. This is a situation that is naturally expected. That is, in the near future, it is expected that the reproduction compatibility problem between the DVD standard (medium density recording standard) and the optical disk standard (high density recording standard) having a higher density than the DVD standard will be realized. Therefore, an optical disc structure capable of reproducing both the next-generation high-density recording standard (high-density recording standard) and the DVD standard (medium-density recording standard) has been a problem.

  In view of the above-described problems, the present invention is inexpensive and has no deterioration in characteristics, and has a higher density than the current low-density recording standard (CD standard), the next-generation high-density recording standard (high-density recording standard) and the low-density recording standard ( CD standard) is intended to provide an optical disc that can be used for both purposes.

  Another object of the present invention is to provide compatibility with optical discs of three standards having different recording densities from low density recording standards, medium density recording standards, and high density recording standards (next generation high density recording standards). It is possible to provide an inexpensive optical disc that can be reproduced according to the standard.

  Still another object of the present invention is to be compatible with multiple standards in which the thickness of each layer including the thickness of an intermediate layer such as an adhesive layer is gently limited, a desired thickness can be easily realized, and cost can be easily reduced. It is to provide a reproducible optical disc.

In order to achieve the above object, the first invention provides an optical disc having a low density recording area, a medium density recording area, and a high density recording area having different recording densities.
It is made of a transparent optical material that transmits light for reading information recorded in the low-density recording area and the medium-density recording area, has a thickness that is ½ of the CD standard thickness, and the first and first thicknesses. A first substrate having two main surfaces;
A first concavo-convex shape portion formed on the first main surface of the first substrate;
Over the entire surface of the first concavo-convex shape portion that selectively transmits light for reading information recorded in the low-density recording area and reflects light for reading information recorded in the medium-density recording area. A first reflective film layer formed by:
An adhesive layer that is formed on the first reflective film layer and selectively transmits light for reading information recorded in the low-density recording area;
A first main surface, the low-density recording area is formed on the first main surface, and the high-density recording area is formed on the outer peripheral side of the low-density recording area; A second substrate having a thickness equal to that of the first substrate, the surface of which is in contact with the adhesive layer;
Provided on the first main surface of the second substrate, the low-density recording area and the high-density recording area have different geometric dimensions, and formed on the first main surface of the second substrate. A second concavo-convex shape portion;
A second reflective film layer formed over the entire surface of the second uneven portion;
An optical thickness formed on the surface of the second reflective film layer and necessary for reading the information recorded in the high-density recording area, for reading the information recorded in the high-density recording area An optical disc comprising a protective layer made of a transparent thin film that transmits light is provided.
According to a second aspect of the present invention, there is provided the optical disc according to claim 1, wherein the first reflective film layer region obtained by parallel projection of the low density recording region is a transparent region.
According to a third aspect of the present invention, there is provided the optical disc according to claim 1 or 2, wherein the depths of recording pits formed in the low density recording area and the high density recording area are equal.
4. The optical disk according to claim 1, wherein one continuous track guide groove is formed in the low density recording area and the high density recording area. I will provide a.
5th invention provides the optical disk of any one of Claims 1 thru | or 4 by which the independent track guide groove | channel is formed in the said low density recording area and the said high density recording area, respectively. To do.

  According to the present invention, the low-density recording area that can be played back by the CD playback device is provided in the recording area of the next-generation high-density recording optical disk. Thus, a predetermined reproducing operation can be performed even in the CD reproducing apparatus.

  In addition, according to the present invention, by adopting a structure using two substrates, three standards of a low density recording standard (CD standard), a medium density recording standard (DVD standard), and a next generation high density recording standard are adopted. A multi-device compatible playback type optical disc that can be played back can be realized at the same cost as a DVD double-layer optical disc.

Furthermore, according to the present invention, the thickness of each layer including the thickness of the intermediate layer such as the adhesive layer is moderately limited, and a desired thickness can be easily realized. It is possible to provide an optical disc that can be played back in a compatible manner.
Therefore, according to the present invention, the transition to the next-generation high-density recording standard is smoothly performed, and a certain content can be supplied even to a user who has only a conventional playback apparatus.

  Next, first to sixth embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Accordingly, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(First embodiment)
As shown in FIG. 1, an optical disc according to the first embodiment of the present invention includes a substrate 1, a concavo-convex shape portion that is provided on the main surface of the substrate 1 and has an inner peripheral region 5 and an outer peripheral region 4, It is composed of a reflective film layer disposed on the surface of the uneven portion and a protective layer (sheet) 6 formed on the reflective film layer.

  Here, the substrate 1 is a transparent substrate made of a transparent optical material, and has a CD standard thickness tD = 1.2 mm ± 0.1 mm. As the transparent substrate used for the substrate 1, a plastic substrate or a glass substrate made of an acrylic resin such as polycarbonate or polymethyl methacrylate (PMMA) is suitable. The outer peripheral side region 4 of the uneven portion provided on the main surface of the substrate 1 differs from the inner peripheral side region 5 in the geometric dimension of the surface. Here, the “uneven shape portion” is a portion having an uneven shape composed of a track guide groove and a recording pit. For example, the inner peripheral side region 5 has a CD-standard concavo-convex shape made up of track guide grooves with a track pitch of 1.6 μm, and the outer peripheral side region 4 has a next-generation high-density recording standard made up of track guide grooves with a track pitch of 0.36 μm. An uneven shape may be used. Then, by forming a reflective film layer on the surface of the concavo-convex portion, the inner peripheral region 5 is made a low density recording region 3b and the outer peripheral region 4 is made a high density recording region 3a. The reflective film layer is a total reflective film layer having a reflectance of 70% or more, preferably 90% or more. The total reflection film layer may be made of a metal thin film such as aluminum (Al) or gold (Au). As a result, the recording surface of the optical disc according to the first embodiment of the present invention is divided into two regions in the radial direction. For example, the inner peripheral side region 5 of the CD standard and the outer peripheral side region 4 on the outer peripheral portion. Is arranged.

  The protective layer (sheet) 6 is composed of a transparent thin film having an optical thickness necessary for reading information recorded in the high-density recording area 3a. For example, a thin film such as an ultraviolet (UV) curable resin can be used as the protective layer 6. The “optical thickness necessary to read information recorded in the high-density recording area 3a” tp of the protective layer 6 is mainly an objective after comprehensively considering system tolerances such as disc tilt. Determined by the optical design of the lens. In the concept such as the presentation example of the aforementioned academic conference of the Physical Society of Japan, the maximum thickness tpmax is about 200 μm. On the other hand, the lower limit tpmin of the optical thickness tp of the protective layer 6 is determined depending on whether a protective function for protecting the high-density recording area 3a is secured. That is, it is preferable that tpmin = 10 μm or more in consideration of the reliability of the optical disc according to the first embodiment of the present invention and the influence of the collision of the lens with the surface of the protective layer 6. Therefore, the optical thickness tp of the protective layer 6 is tp = 10 μm to 200 μm. The optical thickness tp of the protective layer 6 is more preferably about tp = 100 to 120 μm.

  In the optical disc according to the first embodiment of the present invention, when reading information recorded in the high-density recording area 3a, the high-density recording area reading light 9 is transmitted through the protective layer 6 so as to pass through the protective layer 6. Is incident from the main surface side (upper surface) of the substrate 1 on which is formed. On the other hand, when reading the information recorded in the low density recording area 3b, the low density recording area reading light 10 is emitted from the other main surface of the substrate 1, that is, the back side, with the CD standard thickness tD = 1.2 mm ± 0. .. 1 mm is transmitted and enters the inner peripheral region 5.

  As described above, the high-density recording area reading light 9 and the low-density recording area reading light 10 have opposite incident surfaces during reproduction. For this reason, the optical thickness tp of the protective layer 6 is not optically related to the low density recording area 3b. On the other hand, the substrate thickness tD is not optically involved in the high-density recording area 3a as the next-generation high-density recording optical disk. Therefore, the substrate thickness tD can be optimized for the low density recording area 3b, and the thickness tp of the protective layer 6 can be optimized for the high density recording area 3a.

  In the optical disc, there is a strict requirement for the thickness error Δt of the light transmission layer reaching the information recording area. As already described, in the case of CD, at NA = 0.45, the standard of the light transmission layer thickness error Δt is ΔtCD = ± 100 μm. According to the optical disc according to the first embodiment of the present invention, it is possible to easily set the total thickness of the substrate 1 and the protective layer 6 within the allowable range ΔtCD of the CD standard thickness tD. This is because, as described above, the incident surfaces of the high-density recording area reading light 9 and the low-density recording area reading light 10 are opposite to each other during reproduction. For example, if the optical thickness tp of the protective layer is tp = 100 μm or less, the total thickness of the substrate 1 and the protective layer 6 is within the range of the CD standard thickness tD + | ΔtCD | considering the allowable range Δt. Can be set. If the thickness of the substrate 1 is first selected as tD− | ΔtCD |, the optical thickness tp of the protective layer 6 can be selected up to a range of 2 | ΔtCD |. Therefore, if the optical thickness tp of the protective layer 6 is selected in the range up to the maximum value of 200 μm, the allowable range can be satisfied. Therefore, it is possible to satisfy the optical disc structure of the CD standard without changing the manufacturing method of the next generation high density recording optical disc.

As already described, in the optical disc according to the first embodiment of the present invention, the inner peripheral area 5 is the CD standard (low density recording standard), and the outer peripheral area 4 is the next generation high density recording standard. Is possible. In this way, compatibility with the conventional system (CD playback device) on the optical disk side can be made possible when the next generation high density recording optical disk is widespread. It is impossible to record the same content of high-definition video assumed in the next-generation high-density recording optical disc at the CD recording density. However, for example, high-resolution image / audio information is recorded in the outer peripheral area 4 of the optical disc according to the first embodiment of the present invention, and the information recorded in the outer peripheral area 4 is, for example, the outer peripheral area 4. If you have recorded typical or summary information, trailers in the video CD standard, movie theme songs, soundtracks, etc., you can reproduce the information in the inner area 5 with a CD playback device. It becomes possible. Alternatively, the game program may be recorded in the outer peripheral area 4 and the user data of this game may be recorded in the inner peripheral area 5.

(Second Embodiment)
The optical disk according to the second embodiment of the present invention shown in FIG. 2 is similar to the optical disk according to the first embodiment. The substrate 1 is provided on the main surface of the substrate 1 and the inner peripheral side region 5 and the outer periphery. It is comprised from the uneven | corrugated shaped part which has the side area | region 4, the reflective film layer arrange | positioned on the surface of the uneven | corrugated shaped part, and the protective layer (sheet | seat) 6 formed in the upper part of this reflective film layer. Then, by forming a reflective film layer on the surface of the concavo-convex shape portion, the inner peripheral region 5 is made a low density recording region 3b and the outer peripheral region 4 is made a high density recording region 3a. The protective layer (sheet) 6 has an optical thickness tp necessary for reading information recorded in the high-density recording area 3a. Furthermore, in the optical disc according to the second embodiment of the present invention, a low density recording label 23 is provided on the protective layer 6 side of the inner peripheral region 5, and high density recording is performed on the back surface side of the substrate 1 in the outer peripheral region 4. A label 24 is provided.

  When the information recorded on the outer peripheral side area 4 is read, the optical disk according to the second embodiment of the present invention emits the high-density recording area reading light 9 on the main surface side of the substrate 1 as shown in FIG. Incident from (upper surface). On the other hand, when reading the information recorded in the inner peripheral side region 5, the low density recording region reading light 10 enters the inner peripheral side region 5 from the other main surface (lower surface) side of the substrate 1. However, as can be seen from FIG. 2, there is a region through which the high-density recording region reading light 9 and the low-density recording region reading light 10 are not transmitted, so the low-density recording label 23 and the high-density recording label 24 are placed in this region. It is possible to arrange. As described in the first embodiment, since the high-density recording area reading light 9 and the low-density recording area reading light 10 have opposite incident surfaces at the time of reproduction, the substrate thickness tD of the substrate 1 is reduced. The thickness tp of the peripheral region 5 and the protective layer 6 can be optimized for the peripheral region 4. The total thickness of the substrate 1 and the protective layer 6 can be easily set within the allowable range ΔtCD of the CD standard thickness tD.

  In a reproducing apparatus that reproduces two types of optical disks from the same side, it is necessary to invert each of the optical disk surfaces for reproduction. In the optical disk according to the second embodiment of the present invention shown in FIG. 2, the low density recording label 23 and the high density recording label 24 are used to determine whether the surface is a low density recording standard or a high density recording standard. Therefore, the user can easily select the surface.

  When recording content, for example, a high-quality movie is recorded in the outer peripheral area 4, the content is displayed on the high-density recording label 24, and sound track audio information is recorded in the inner peripheral area 5. It may be displayed on the density recording label 23 that it is audio information. For example, in the recorded video of the live concert, the audio information of the opening song may be recorded in the inner peripheral area 5 and displayed on the low density recording label 23. As a result, it is possible to coexist contents having the same title and greatly different capacities, and the user can easily select a face.

(Third embodiment)
The optical disk according to the third embodiment of the present invention shown in FIG. 3 is similar to the optical disk according to the first embodiment. The substrate 1 is provided on the main surface of the substrate 1 and the inner peripheral side region 5 and the outer periphery. It is comprised from the uneven | corrugated shaped part which has the side area | region 4, the reflective film layer arrange | positioned on the surface of the uneven | corrugated shaped part, and the protective layer (sheet | seat) 6 formed in the upper part of this reflective film layer. Then, by forming a reflective film layer on the surface of the concavo-convex portion, the inner peripheral region 5 is made a low density recording region 3b and the outer peripheral region 4 is made a high density recording region 3a. Further, as shown in FIG. 3, the optical disk according to the third embodiment of the present invention is further provided with a lead-in area (high-intensity) at the time of reproducing the high-density recording area on the inner peripheral side (low-density recording area) 5. Density recording area lead-in area) 25 is arranged.

  As shown in FIG. 3, a player can be recognized as a CD by providing a high-density recording area lead-in area 25 at the innermost periphery and a lead-out area at the boundary according to the standard. Further, by setting the diameter of the circle formed by the boundary portion to about 8 cm, it is recognized as an 8 cm CD that exists as a standard, and it is possible to perform a good reproduction operation.

  Since the region on the outer peripheral side of the boundary portion is configured as the outer peripheral side region 4, the recording pits are also formed according to the high density recording standard. The outer peripheral side region 4 is structured to be reproduced by irradiating high-density recording region reading light from the protective layer 6 side above the recording pits. Therefore, when reproducing as a next-generation high-density recording optical disk, the region on the outer peripheral side of the boundary portion satisfies the optical specifications as the next-generation high-density recording optical disk, so that the reproduction operation is performed satisfactorily. Also in the optical disc according to the third embodiment of the present invention shown in FIG. 3, the protective layer (sheet) 6 has an optical thickness tp necessary for reading the information recorded in the high-density recording area 3a. Have. That is, the protective layer 6 is a transparent layer having a thickness of 100 to 120 μm, and is formed on the low density recording area constituting the inner peripheral area 5, the outer peripheral area 4 and the high density recording area constituting the high density recording area lead-in area 25. Is provided.

  In a next-generation high-density recording optical disk proposed in the past (other than the optical disk composed of two areas of the inner peripheral area 5 and the outer peripheral area 4 of the present invention), high-density recording is usually performed from the innermost periphery. It is. Therefore, if the lead-in area of this next-generation high-density recording optical disc is set on the inner circumference side of the CD-standard lead-in area, this high-density lead-in area can be used when reproducing the next-generation high-density recording optical disc. You can play it first. Therefore, it is possible to record information as to whether the optical disk of the present invention or a conventional next-generation high-density recording optical disk. Furthermore, by recording again the radius, address, and the like at which the outer peripheral area 4 starts, it is possible to reproduce the outer peripheral area 4 of the optical disk of the present invention without any problem.

(Fourth embodiment)
The optical disc according to the fourth embodiment of the present invention shown in FIG. 4 is an optical disc capable of reproducing three standards compatible including a medium density recording area such as a DVD. That is, the optical disk according to the fourth embodiment of the present invention includes a first substrate 19; a first uneven shape portion provided on the first main surface of the first substrate 19; this first uneven shape portion. A medium density recording region 20 having a first reflective film layer disposed on the surface thereof; an adhesive layer 16 provided on the surface of the medium density recording region 20; and a second main surface in contact with the adhesive layer 16 2nd board | substrate 21; 2nd uneven | corrugated shaped part provided in the 1st main surface of this 2nd board | substrate 21; 2nd reflection film layer arrange | positioned on the surface of this 2nd uneven | corrugated shaped part; This 2nd reflection The protective layer 6 is formed on the surface of the film layer.

  The first reflective film layer disposed on the surface of the first concavo-convex shape portion reflects the medium density recording area reading light 15d of the second wavelength λ2 and transmits the low density recording area reading light 10 having the first wavelength λ1. It is a semi-transparent film (half mirror) having selectivity. As the translucent film having wavelength selectivity, a dielectric multilayer film using a predetermined combination of titanium oxide (TiO2), zinc sulfide (ZnS), oxide film (SiO2), nitride film (Si3N4), or the like is used. I can do it.

  The first substrate 19 is made of a transparent optical material having first and second main surfaces, has a thickness (= 0.6 mm) that is 1/2 of the CD standard thickness tD, and has a diameter of 12 cm. is there.

  The adhesive layer 16 is made of an adhesive having wavelength selectivity that transmits the low-density recording region reading light 10 having the first wavelength λ1. The second substrate 21 has first and second main surfaces, and has the same thickness (= 0.6 mm) and diameter (= 12 cm) as the first substrate 19. As the first substrate 19 and the second substrate 21, a plastic substrate or a glass substrate made of an acrylic resin such as polycarbonate or polymethyl methacrylate (PMMA) can be used. The second concavo-convex shape portion provided on the first main surface of the second substrate 21 has an inner peripheral side region 5 and an outer peripheral side region 4 having a geometric dimension different from that of the inner peripheral side region 5. . The second reflective film layer is arranged on the surface of the second concavo-convex portion so that the inner peripheral side region 5 is a low density recording region 3b and the outer peripheral side region 4 is a high density recording region 3a. The second reflective film layer is a total reflective film layer having a reflectance of 70% or more, preferably 90% or more. The total reflection film layer may be made of a metal thin film such as aluminum (Al) or gold (Au). The protective layer 6 is made of a transparent thin film, and has an optical thickness tp necessary for reading information recorded in the high-density recording area 3a described in the first embodiment.

  That is, in the optical disc according to the fourth embodiment of the present invention, as shown in FIG. 4, the high density recording area 3a and the low density recording area 3b are positioned on the uppermost portion of the upper first substrate 21. The first substrate 21 and the second substrate 19 are oriented in the same direction, and are bonded together with a transparent adhesive layer 16.

  In the optical disk according to the fourth embodiment of the present invention, for example, the low density recording area 3b on the uppermost surface side of the optical disk is the CD standard (low density recording standard), and the high density recording area 3a is the next generation high density recording standard. The medium density recording area 20 in the center of the optical disk can be set to the DVD standard (medium density recording standard). An optical disc that satisfies the three types of standards, CD, DVD, and next-generation high-density recording optical disc, usually requires a three-layer recording area, and is considered to require bonding of three substrates. That is, conventionally, it has been considered that it is difficult to bond two substrates together. However, as already described in the first to third embodiments, according to the present invention, the CD standard (low density recording standard) and the next generation high density recording standard are realized by only one layer. Since it is possible, as shown in FIG. 4, by adding one layer (one substrate), (partial) compatibility of three standards becomes possible.

  (A) When reproducing an optical disc according to the fourth embodiment of the present invention as a CD, a laser beam (low-density recording area reading light) 10 having a wavelength of 780 nm band is NA = NA = from the first substrate 19 side. Information is recorded in the low density recording area 3b from the reflected light from the low density recording area 3b by focusing with a lens of about 0.45.

  (B) At the time of reproduction as a DVD, a laser beam (medium density recording area reading light) 15d having a wavelength of 650 nm band is applied from the side of the first substrate 19 on which the translucent film is formed to a lens having an NA of about 0.6. And the information recorded in the medium density recording area 20 is obtained from the reflected light from the medium density recording area 20.

  (C) When reproducing as an optical disk for next-generation high-density recording, laser light (high-density recording area reading light) 9 with a wavelength of 410 nm is applied from the protective layer 6 side to NA = 0.7 to 0.85. The information recorded in the high-density recording area 3a is obtained from the reflected light from the high-density recording area 3a.

  As described above, by using the technique according to the fourth embodiment of the present invention, the two-layer recording area (20; 3a, 3b) using the first substrate 19 and the second substrate 21 is used. It is possible to obtain an optical disc that can be played back according to the standard.

  The manufacturing cost of the optical disc according to the fourth embodiment of the present invention is comparable to that of a conventional DVD double-layer optical disc or a hybrid SACD. That is, since a compatible playback disc of 3 standards can be produced at the manufacturing cost of a compatible playback disc of 2 standards, the manufacturing cost per standard becomes lower.

(Fifth embodiment)
The optical disk according to the fifth embodiment of the present invention shown in FIG. 5 is similar to the optical disk according to the first embodiment. The substrate 1 is provided on the main surface of the substrate 1 and the inner peripheral side region 5 and the outer periphery. It is comprised from the uneven | corrugated shaped part which has the side area | region 4, the reflective film layer arrange | positioned on the surface of the uneven | corrugated shaped part, and the protective layer (sheet | seat) 6 formed in the upper part of this reflective film layer. Then, by forming a reflective film layer on the surface of the concavo-convex portion, the inner peripheral region 5 is made a low density recording region 3b and the outer peripheral region 4 is made a high density recording region 3a. The protective layer (sheet) 6 has an optical thickness tp necessary for reading information recorded in the high-density recording area 3a.

  In the optical disc according to the fifth embodiment of the present invention, as shown in FIG. 5, a write-once recording area 26 is arranged in the inner peripheral side area 5, and a write-once type such as a so-called CD-R or RW is provided. It has a rewritable recording structure. In this case, in master mastering, the inner periphery is formed as a groove (continuous groove) with wobble (meandering), and the recording signal is modulated (on / off modulation of the recording light beam) at the outer periphery, and the recording medium is formed after film formation A total reflection film layer of aluminum (Al) or gold (Au) may be formed. In this case, although the film formation region of the recording medium may be limited by a mask or the like, the total reflection film layer is the uppermost layer, and in the next-generation high-density recording optical disk, reproduction is performed from the protective film side. Such area limitation is not always necessary.

  When reading information recorded on the outer peripheral side area 4, the optical disk according to the fifth embodiment of the present invention emits high-density recording area reading light 9 on the main surface side of the substrate 1, as shown in FIG. Incident from (upper surface). On the other hand, when reading write-once and rewritable recording information recorded on the inner peripheral side region 5, the low-density recording region reading light 10 is sent from the other main surface (lower surface) side of the substrate 1 to the write-once recording region. 26 is incident.

  Such an optical disc having the inner peripheral region 5 can be applied to various uses. For example, in a game that incorporates a high-resolution video, by recording the user's progress and data in the inner peripheral area 5, a main memory or a memory card that is conventionally required for a game machine is separated. You can avoid it. That is, an optical disc for game software having an additional function is possible.

  In general, the recording operation is more difficult than the reproducing operation, and it is generally difficult to increase the density. However, according to this structure, only the recording portion is already widely used. Since it is equivalent to RW, a recording operation can be easily performed. In addition, in this application, the amount of data that needs to be recorded is sufficiently small compared to the playback content, so that even the low density can sufficiently achieve the purpose.

(Sixth embodiment)
An optical disc according to a sixth embodiment of the present invention shown in FIG. 6 is an optical disc capable of reproducing three standards compatible with a medium density recording area 20 such as a DVD, similar to the fourth embodiment. That is, the optical disk according to the sixth embodiment of the present invention includes a first substrate 19; a first uneven shape portion provided on the first main surface of the first substrate 19; this first uneven shape portion. A medium density recording region 20 formed by selectively disposing a first reflective film layer on the surface; an adhesive layer 16 provided on the surface of the medium density recording region 20; a second main layer on the adhesive layer 16; 2nd board | substrate 21 which contact | connected the surface; 2nd uneven | corrugated shaped part provided in the 1st main surface of this 2nd substrate 21; 2nd reflective film layer arrange | positioned on the surface of this 2nd uneven | corrugated shaped part; The protective layer 6 is formed on the surface of the second reflective film layer. The protective layer (sheet) 6 has an optical thickness tp necessary for reading information recorded in the high-density recording area 3a.

  Unlike the optical disc according to the fourth embodiment shown in FIG. 4, the optical disc according to the sixth embodiment has a first reflective film layer obtained by parallel projecting the inner peripheral region 5 of the uppermost layer downward. The area is configured as a transparent area 27. That is, the first reflective film layer is selectively formed in the inner peripheral region 5 so that the first reflective film layer is not disposed. If the region obtained by parallel projection of the inner peripheral region 5 of the uppermost layer is set as the transparent region 27, the light to the low density recording region 3b will not be attenuated or scattered due to the transmission characteristics of the first reflective film layer. Therefore, the reproduction characteristics of the low density recording area 3b are improved. In this case, the first reflective film layer does not need to be a translucent film using a dielectric multilayer film or the like as in the optical disk according to the fourth embodiment of the present invention shown in FIG. Therefore, it is only necessary to selectively form a total reflection film layer such as aluminum (Al) using a mask or the like so as not to be disposed in a region obtained by parallel projection of the innermost region 5 of the uppermost layer. Therefore, an optical disk can be manufactured easily and inexpensively. If the diameter of the circle that defines the boundary between the inner peripheral side region 5 and the outer peripheral side region 4 is selected to be 8 cm, it can be recognized as an 8 cm CD that exists as a standard, and thus a good reproduction operation is possible. .

(Master mastering)
Generally, master mastering uses processes such as photolithography and etching. In order to master the two masters in the same process, it is necessary to slightly improve the conventional technique. The pit width can be changed by switching between two beams and one beam, the recording light power, etc., and the track pitch can be changed by changing the mastering linear velocity or the feed speed.

  Note that although the irradiation direction of the reading light flux varies depending on the region, this means that the unevenness of the same recording pit is apparently reversed with respect to the light. In any case, reproduction is possible, but if you want to obtain the same tracking polarity regardless of the tracking method, mask the inner and outer circumferences sequentially with master mastering, and expose with both negative resist and positive resist, An optical disk with unevenness can be produced. Further, in a next-generation high-density recording optical disc for which the standard is not yet determined, if the recording pit irregularities are reversed from the CD (as viewed from the reading side), the same irregularity direction can be used on the mastering and can be easily manufactured. .

  If the pit depth of the next-generation high-density recording standard and the pit depth of the low-density recording standard (CD standard) are set to be the same, the next-generation high-density recording standard and the low-density recording standard (CD standard) can be performed with a single etching. Both recording pits can be formed. In addition, if selective etching is performed using a mask technique, optically optimal pit depth can be formed for each of the next generation high density recording standard and low density recording standard (CD standard), and the reproduction characteristics can be improved. Is also possible.

  Further, if the two areas are made one continuous track guide groove, the master mastering can be performed in a single continuous process. At this time, the pit width and the track width can be controlled by switching the beam and the linear velocity.

  On the other hand, if the two regions are independent track guide grooves, a mastering optical system can be prepared for each, and mastering mastering with better characteristics is possible.

  Also, by making the two areas spiral in the same direction, using a playback device equipped with each playback pickup on the top and bottom of the optical disk, without flipping up and down and limiting the spindle rotation direction to one direction, simple playback Playback on the device is possible. This structure is suitable as a structure that does not involve reversal or replacement of the optical disk, in an application that combines program reproduction and user data recording in a game machine.

1 is a cross-sectional view showing a schematic structure of an optical disc according to a first embodiment of the present invention. It is sectional drawing which shows schematic structure of the optical disk based on the 2nd Embodiment of this invention. It is sectional drawing which shows schematic structure of the optical disk based on the 3rd Embodiment of this invention. It is sectional drawing which shows schematic structure of the optical disk based on the 4th Embodiment of this invention. It is sectional drawing which shows schematic structure of the optical disk based on the 5th Embodiment of this invention. It is sectional drawing which shows schematic structure of the optical disk based on the 6th Embodiment of this invention. It is sectional drawing which shows schematic structure of the optical disk (CD) which concerns on a prior art example. It is sectional drawing which shows schematic structure of the optical disk (optical disk for next generation high-density recording) concerning a prior art example. It is sectional drawing which shows schematic structure of the optical disk (DVD double layer optical disk) which concerns on a prior art example. It is sectional drawing which shows schematic structure of the optical disk (hybrid SACD) which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Rotation (symmetric) axis 3a High-density recording area 3b, 22 Low-density recording area 4 Outer peripheral area 5 Inner peripheral area 6 Protective layer 9 High-density layer reading light 10 Low-density layer reading light 11, 21 Substrate 12 Second recording area 13, 19 First substrate 14 First recording area 15a, 15c Second recording area reading light 15b First recording area reading light 15d Medium density recording area reading light 16 Adhesive layer 20 Medium Density recording area 23 Low density recording area label 24 High density recording area label 25 High density recording area Lead-in area 26 Write-once recording area 27 Transmission area tD Optical disc thickness tp Protective layer thickness ts Substrate thickness

Claims (5)

In an optical disc having a low density recording area, a medium density recording area, and a high density recording area having different recording densities,
It is made of a transparent optical material that transmits light for reading information recorded in the low-density recording area and the medium-density recording area, has a thickness that is ½ of the CD standard thickness, and the first and first thicknesses. A first substrate having two main surfaces;
A first concavo-convex shape portion formed on the first main surface of the first substrate;
Over the entire surface of the first concavo-convex shape portion that selectively transmits light for reading information recorded in the low-density recording area and reflects light for reading information recorded in the medium-density recording area. A first reflective film layer formed by:
An adhesive layer that is formed on the first reflective film layer and selectively transmits light for reading information recorded in the low-density recording area;
A first main surface, the low-density recording area is formed on the first main surface, and the high-density recording area is formed on the outer peripheral side of the low-density recording area; A second substrate having a thickness equal to that of the first substrate, the surface of which is in contact with the adhesive layer;
Provided on the first main surface of the second substrate, the low-density recording area and the high-density recording area have different geometric dimensions, and formed on the first main surface of the second substrate. A second concavo-convex shape portion;
A second reflective film layer formed over the entire surface of the second uneven portion;
An optical thickness formed on the surface of the second reflective film layer and necessary for reading the information recorded in the high-density recording area, for reading the information recorded in the high-density recording area An optical disc comprising a protective layer made of a transparent thin film that transmits light.   2. The optical disk according to claim 1, wherein a region of the first reflective film layer obtained by parallel projection of the low density recording region is a transparent region.   3. The optical disc according to claim 1, wherein the depths of recording pits formed in the low density recording area and the high density recording area are equal.   4. The optical disc according to claim 1, wherein one continuous track guide groove is formed in the low density recording area and the high density recording area.   5. The optical disc according to claim 1, wherein independent track guide grooves are formed in the low density recording area and the high density recording area, respectively.

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