HK1075119B - Optical disk - Google Patents

Description

Optical disk

Technical Field

The present invention relates to an optical Disk such as a DVD (Digital Versatile Disk), a CD (Compact Disk), or the like, which is used as a recording medium in an information processing apparatus such as an optical Disk drive apparatus or the like, and more particularly to an optical Disk which prevents deformation or surface deformation in a radial direction of the optical Disk from occurring and suppresses deviation or deflection of a light beam incident on the optical Disk with respect to an optical axis.

This application claims priority to Japanese patent application JP 2002-254989, filed on 8/30/2002, which is hereby incorporated by reference.

Background

Hitherto, an optical disc used as a recording medium in an information processing apparatus such as an optical disc drive is generally configured as shown in fig. 1. The optical disk 11 shown in fig. 1 includes a disk substrate 10 having a recording layer 12 formed on one surface thereof and a transparent protective film 20 formed on the recording layer 12. The disk substrate 10 of the optical disk 11 has a center hole 14 formed in the center thereof. When the optical disc 11 is placed on a disc rotation driving mechanism disposed on an optical disc drive, the center hole 14 engages with a centering member disposed on the disc rotation driving mechanism, so that the center of rotation of the optical disc 11 corresponds to the center of rotation of the disc rotation driving mechanism.

The recording layer 12 is formed on the optical disc 11 in various ways, for example, in such a way that an information pit train is formed along a recording track of its concentric shape or spiral shape, and the information pit train thus formed is covered with a reflective film. For example, the thickness of the disk substrate 10 is about 1.1mm, and the thickness of the transparent protective film 20 is about 0.1 mm.

This optical disk 11 is set on a turn table of an optical disk drive, not shown in the drawing, with respective centers aligned together at the time of centering and driven at high speed, and at the same time, a light beam L emitted from an optical pickup is incident to the recording layer 12 through the transparent protective film 20, thereby recording information onto the recording layer 12 or reproducing information recorded on the recording layer 12.

The flatness of the recording layer 12 of the optical disc must be well maintained in order to accurately record/reproduce information using an optical pickup under the condition that the optical disc is placed on a turn table of an optical disc drive and rotated at a high speed. In particular, in order to make the frequency of the transmission signal higher in order to increase the recording density and the transmission speed of the signal for recording/reproduction, it is necessary to suppress the deviation or deflection of the light beam L incident on the optical disc from the optical axis due to various factors. That is, it is necessary to prevent deformation from occurring in the radial direction of the optical disc.

For example, according to international application WO99/00794, an optical disc is disclosed in which a water-repellent film is formed on a specific side of the optical disc to prevent permeation of water into the disc substrate, thus preventing deformation in the optical disc.

The influence factor of the deformation occurring in the optical disc is, in addition to the water permeation, that one side and the other side of the optical disc 11 have different layer structures and are made of different materials, for example, thereby forming an asymmetric structure in the thickness direction of the optical disc substrate 10, as shown in fig. 1.

Disclosure of Invention

It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art by providing a new type of optical disc.

Another object of the present invention is to provide an optical disc that can prevent deformation caused by different layer structures of one side and the other side of the optical disc, thereby preventing skew (skew) from occurring when the optical disc is mounted on an optical disc drive.

The above object may be achieved by providing an optical disc according to the present invention, comprising: a disk substrate having a recording layer formed on a first surface thereof; a transparent protective film provided on the recording layer formed on the first surface of the disk substrate; and a print mark film provided on the second surface of the disk substrate, having a function of reducing a skew due to a film quality and a film structure corresponding to the transparent protective film, and a function of representing information by printing a mark.

According to the optical disk of the present invention, asymmetry between the first side and the second side of the optical disk is eliminated by a printed mark film provided on the second side of the disk substrate, with a transparent protective film on a recording layer formed on the first side of the disk substrate.

The optical disc according to the present invention can effectively prevent skew due to asymmetry between layer structures of the disc substrate in the thickness direction, so that the flatness of the recording layer can be well maintained, which can realize a very stable recording/reproducing operation.

As a result, the optical disc medium can be applied to high recording density and increased transmission speed of signals for recording/reproduction.

These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention.

Drawings

FIG. 1 is a cross-sectional view of a conventional optical disc;

FIG. 2 is a cross-sectional view of a first embodiment of an optical disc according to the present invention;

FIG. 3 is a cross-sectional view of a second embodiment of an optical disc according to the present invention;

FIG. 4 is a cross-sectional view of a third embodiment of an optical disc according to the present invention;

FIG. 5 is a cross-sectional view of a fourth embodiment of an optical disc according to the present invention;

fig. 6 is a cross-sectional view of a fifth embodiment of an optical disc according to the present invention;

FIG. 7 is a graph showing the transient variation of skew values for optical discs according to the present invention and conventional;

Detailed Description

An optical disc according to the present invention will be described in detail below with reference to the accompanying drawings. Note that the optical disc according to the present invention is used as a recording medium in an information processing apparatus such as an optical disc drive or the like.

Fig. 2 is a cross-sectional view of a first embodiment of an optical disc according to the present invention.

The optical disc 111 shown in fig. 2 includes a disc substrate 110 made of acrylic synthetic resin or the like, having a recording layer 112 on one surface thereof, and a transparent protective film 120 formed on the recording layer 112. In addition, the disk substrate 110 includes a printed mark film 130 formed on the other surface thereof.

Meanwhile, the disk substrate 110 has a center hole 114 formed at the center thereof. When the optical disc 111 is placed on a disc rotation driving mechanism disposed on an optical disc drive, the center hole 114 engages with a centering member disposed on the disc rotation driving mechanism, so that the center of rotation of the optical disc 111 corresponds to the center of rotation of the disc rotation driving mechanism.

The recording layer 112 provided on one side of the disk substrate 110 is formed in such a manner that an information pit train of a pit-and-pit pattern is formed along a recording track, and the information pit train thus formed is covered with a reflective film.

The transparent protective film 120 formed on the recording layer 112 is a synthetic resin film mainly made of a thermoplastic synthetic resin, such as a polycarbonate film, through which light can be transmitted, which covers the recording layer 112 of the disk substrate 110.

The printed mark film 130 formed on the other side of the disk substrate 110 is a synthetic resin film mainly made of thermoplastic synthetic resin, and light can be transmitted through the film, similarly to the transparent protective film 120, such as a polycarbonate film or the like. More specifically, the print label film 130 is formed in such a manner that a color polycarbonate paste to which ink is added is printed on the other surface of the disk substrate 110 by a screen printing method. The printed label film 130 formed by printing one or more kinds of colored polycarbonate pastes serves as an information representing part to represent the names of contents and works recorded on the optical disc 111 and identification information such as label names.

Note that the area of the print mark film 130 formed on the other face of the disk substrate 110 substantially covers the entire area of the other face of the disk substrate 110, and substantially corresponds to the area of the transparent protective film 120 formed on one face of the disk substrate 110.

The optical disc 111 according to the present invention is formed to have a diameter of about 120mm and a thickness D of the disc substrate 110₁About 1.1 mm. Thickness D of transparent protective film 120 on recording layer 112₂About 0.1mm, the thickness D of the printed mark film 130 on the other side of the disk substrate 10₃About 0.1 mm. That is, the total thickness of the optical disc 111 according to the present invention is about 1.2 to 1.3 mm.

In the optical disc 111 according to the present invention, a light beam is incident into one surface of the disc substrate 110 on which the transparent protective film 120 is formed, which reads information recorded on the recording layer 112 or writes information on the recording layer 112.

In the optical disk 111 shown in fig. 2 according to the present invention, the printed mark film 130 is provided on the surface of the disk substrate 110 opposite to the surface having the recording layer 112, the film is mainly made of a synthetic resin similar to the material of the transparent protective film 120, and has a thickness approximately equal to that of the transparent protective film 120, and when the top surface and the back surface of the optical disk 111 are compared, both surfaces thereof have the same structure, and therefore the optical disk 111 becomes approximately symmetrical. That is, in the optical disc 111, structural asymmetry in the thickness direction of the disc substrate 110 is eliminated so that deformation or surface deformation particularly in the radial direction is avoided. Since the occurrence of distortion is suppressed as described above, when the optical disc 111 is placed on an optical disc drive to record/reproduce information, the light beam emitted from the optical pickup device provided on the optical disc drive can be kept perpendicular to the optical disc 111, whereby the occurrence of skew can be prevented.

In the above-described optical disc 111, the transparent protective film 120 and the print label film 130 are formed using a thermosetting synthetic resin material such as polycarbonate, but other materials such as an ultraviolet curable resin may be used. In addition, it is not necessary to use the same synthetic resin material for the transparent protective film 120 and the print mark film 130, that is, a synthetic resin material having similar characteristics to some extent may also be used.

A second embodiment of the optical disc according to the present invention is explained below with reference to fig. 3.

In fig. 3, parts or components similar to those of the optical disc 111 shown in fig. 2 are denoted by the same reference numerals.

The optical disc 121 shown in fig. 3 is formed in such a manner that a transparent protective film 220 is provided on the recording layer 112 formed on one side of the disc substrate 110 with an adhesive material 210 bonded therebetween, and a printed mark film 240 is provided on the other side of the disc substrate 110 with an adhesive material 230 bonded therebetween.

The transparent protective film 220 and the print label film 240 are synthetic resin films mainly made of polycarbonate or the like, which are bonded to the one and the other sides of the disk substrate 110 with bonding materials 210 and 230, respectively.

On the surface of the print label film 240, the names of the contents and works recorded on the optical disc 111 and identification information such as a label name and the like are set by printing.

The optical disc 121 shown in fig. 3 is formed to have a diameter of approximately 120mm, and the transparent protective film 220 and the printed mark film 240 thereof are formed to have thicknesses of 0.1mm, respectively, so that the overall thickness of the optical disc 121 is approximately 1.2-1.3mm, similar to the optical disc 111 shown in fig. 1.

Note that also in the optical disc 121, one face having the transparent protective film 220 is provided as a face for recording/reproduction, on which a light beam is incident.

Since the optical disk 121 shown in fig. 3 is also provided with the transparent protective film 220 and the print label film 240, both of which are made of the same material and have approximately equal thicknesses, which are bonded on the respective faces of the disk substrate 110 with the bonding materials 210 and 230, respectively, the disk substrate 110 has approximately the same structured films on both faces thereof. When the top surface and the back surface are compared, both surfaces have the same structure, and thus the optical disc 121 shown in fig. 3 becomes substantially symmetrical. That is, in the optical disc 121, structural asymmetry in the thickness direction of the disc substrate 110 is eliminated so that deformation is avoided, particularly in the radial direction. Since the occurrence of distortion can be suppressed as described above, when the optical disc 121 is set on an optical disc drive to record/reproduce information, a light beam emitted from an optical pickup device provided on the optical disc drive can be kept perpendicular to the optical disc 121, whereby the occurrence of skew can be prevented.

Also in the optical disc 121 of the present embodiment, the transparent protective film 220 and the print label film 240 are formed using a thermosetting synthetic resin material such as polycarbonate or the like, but other materials such as an ultraviolet curable resin may also be employed. In addition, it is not necessary to use the same synthetic resin material for the transparent protective film 220 and the print label film 240, that is, synthetic resin materials having somewhat similar characteristics may also be used.

A third embodiment of an optical disc according to the present invention is explained below with reference to fig. 4.

In fig. 4, parts or components similar to those of the optical disc 111 shown in fig. 2 are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

The optical disc 131 shown in fig. 4 is formed in such a manner that a moisture-proof film 310 is further provided between the other surface of the disc substrate 110 and the printed marks 130 of the optical disc 111 shown in fig. 2. The moisture-proof film 310 is made of a metal or alloy such as Al, Au, Ag, Ni, Cr, Cu, Pt, Ti, etc., a stainless alloy, SiNx, SiOx, SiNxOy, SiC, etc., a dielectric material, or an organic material. When the moisture-proof film 310 is made of metal such as Al or the like, vapor deposition is employed.

Since the moisture-proof film 310 is provided, the optical disk 131 shown in fig. 4 can prevent moisture from invading into the interior of the disk substrate 110, whereby deformation can be prevented from occurring.

In the optical disk 131 shown in fig. 4, the moisture-proof film 310 can be preferably made of the same material as the reflective film as the recording layer 112. Here, the moisture-proof film 310 and the reflective film of the recording layer 112 are both made of Al. Since the reflective film and the moisture-proof film 310 are made of the same material, the disk substrate 110 has approximately the same structure of films on both sides thereof. When the top surface and the back surface are compared, both surfaces have the same structure, and thus the optical disc 131 shown in fig. 4 becomes substantially symmetrical. Here, when the optical disc 131 is disposed on an optical disc drive to record/reproduce information, a light beam emitted from an optical pickup device disposed on the optical disc drive may be maintained perpendicular to the optical disc 131, whereby occurrence of skew may be prevented.

A fourth embodiment of an optical disc according to the present invention is explained below with reference to fig. 5.

In fig. 5, parts or components similar to those of the optical disc 121 shown in fig. 3 are denoted by the same reference numerals, and a detailed description thereof will be omitted.

The optical disc 141 shown in fig. 5 is formed in such a manner that a moisture-proof film 410 is further provided between the other surface of the disc substrate 110 and the adhesive material 230 of the optical disc 121 shown in fig. 3. The moisture-proof film 410 is made of a dielectric material or an organic material such as a metal or an alloy of Al, Au, Ag, Ni, Cr, Cu, Pt, Ti, etc., a stainless alloy, SiNx, SiOx, SiNxOy, SiC, etc.

Since the moisture-proof film 410 is provided, the optical disc 141 can also prevent moisture from invading into the inside of the disc substrate 110, whereby deformation can be prevented from occurring.

Also in the optical disk 141 shown in fig. 5, the moisture-proof film 410 can be preferably made of the same material as the reflective film as the recording layer 112. Here, the moisture-proof film 410 and the reflective film of the recording layer 112 are both made of Al. Since the reflective film and the moisture-proof film 410 are made of the same material, the disk substrate 110 has films of approximately the same structure on both sides thereof. When the top surface and the back surface are compared, both surfaces have the same structure, and thus the optical disc 141 shown in fig. 5 becomes substantially symmetrical. Accordingly, when the optical disc 141 is disposed on an optical disc drive to record/reproduce information, a light beam emitted from an optical pickup device disposed on the optical disc drive can be kept perpendicular to the optical disc 141, whereby occurrence of skew can be prevented.

While the above-described optical discs 131 and 141 are provided with the moisture-proof films 310 and 410 and the printed mark films 130 and 240, respectively, the optical discs 131 and 141 may be provided with only the moisture-proof films 310 and 410, or may be printed with information thereon as printed mark films.

A fifth embodiment of the optical disc according to the present invention is explained below with reference to fig. 6.

In fig. 6, parts or components similar to those of the optical disc 111 shown in fig. 2 are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

The optical disc 151 shown in fig. 6 is formed in such a manner that a water-permeable protective layer 510 having a low water permeability is further provided inside the disc substrate 110 of the optical disc 111 shown in fig. 2. The disc substrate 110 is formed by a co-injection molding technique (coinjection molding technique) or the like, in which a material having a low water permeability is embedded inside the disc substrate 110, thereby reducing the penetration of water thereinto and preventing deformation from occurring in the optical disc 151.

In the optical disk 151 shown in fig. 6, by adding an additive such as a metal foil or the like to the water-permeable protective layer 510 provided inside the disk substrate 110, the appearance of the disk substrate 110 can be improved because it has a marble pattern or the like.

Such a water-permeable protective layer 510 may also be provided inside the disc substrate 110 of the optical disc 121 shown in fig. 3.

The variation of the skew values of the optical disc according to the present invention and the conventional optical disc was measured, and the results are explained as follows.

Here, in the measurement, the optical disk 11 of the structure shown in fig. 1 and the optical disk 111 shown in fig. 2 according to the present invention and the optical disk 131 shown in fig. 4 also according to the present invention are employed.

The skew values are measured in the following manner. First, a reference skew value is determined in a state where an optical disk is placed on a turn table as a base and rotated at a specific speed, and a light beam is perpendicularly incident on a recording layer from a side of a disk substrate having a transparent protective film. According to the reference skew value, when the optical disk is deformed in the radial direction in the incident direction of the light beam, i.e., toward the opposite side to the light beam emitting side, the measured value is "+", and on the other hand, when the optical disk is deformed in the radial direction in the opposite direction to the incident direction of the light beam, i.e., toward the side from which the light beam is emitted, the measured value is "-".

In measuring the skew values, the respective optical disks 11, 111, 131 are retained for a certain period of time in an environment (in a constant temperature and humidity cabinet) in which the temperature is set to 25 ℃ and the humidity is set to 50% until both faces of the disks become parallel to each other. This period is usually around three days.

Subsequently, each of the optical disks 11, 111, 131 whose both surfaces are parallel to each other is moved to and left in an environment (in a constant temperature and humidity chamber) where the temperature is set to 25 ℃ and the humidity is set to 90%. Then, after the deflection value of the measurement start point is set to "0", the instantaneous change in the deflection value is measured. The measurement results are shown in fig. 7.

Note that the skew values are measured at points 55mm from the center of each optical disk 11, 111, 131 having a diameter of 120 mm.

In fig. 7, the horizontal axis represents elapsed time, and the vertical axis represents a skew value representing the tilt angle of the optical disc with respect to the optical axis of the light beam incident on the optical disc.

In fig. 7, "a" represents a change in the skew value of the conventional optical disc 11 shown in fig. 1, "B" represents a change in the skew value of the optical disc 111 shown in fig. 2, in which the optical disc 111 shown in fig. 2 is provided with the printed mark film 130 on the other side of the disc substrate 110, and "C" represents a change in the skew value of the optical disc 131, the optical disc 131 being provided with the moisture-proof film 310 between the disc substrate 110 and the printed mark film 130.

As is apparent from the results shown in fig. 7, the conventional optical disc 11 still has a skew after a lapse of time under varying environments. On the other hand, with the optical disk 111, 131 according to the present invention, having the transparent protective film 120 formed on one side of the disk substrate 110 and the printed mark film 130 formed on the other side of the disk substrate having the same film quality and film structure as the transparent protective film 120, the skew value becomes close to "0" after a certain time elapses under a changed environment. Particularly, the optical disc 131 according to the present invention, which is provided with the moisture-proof film 310 made of the same material as the reflective film as the recording layer 112 and the printed mark film 130, has a minimum variation in skew value under a changed environment. Thus, with the optical disks 111, 131 according to the present invention, even if the environment changes, the distortion in the radial direction can be eliminated after a certain time has elapsed.

As described above, the optical disk according to the present invention is provided with the transparent protective film formed on one surface of the disk substrate having the recording layer and the printed mark film formed on the other surface of the disk substrate having the same structure as the transparent protective film, has a symmetrical structure in the thickness direction, and the occurrence of skew is prevented so that the recording density and the transport speed can be increased.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that the present invention is not limited to the specific embodiments, but various changes, structural modifications and equivalents may be made therein without departing from the scope and spirit of the present invention as set forth and defined in the appended claims.

Industrial applicability

In the optical disk according to the present invention, since the transparent protective film is disposed on the recording layer formed on one side of the disk substrate, and the print mark film having the same film quality and film structure as the transparent protective film and having the function of reducing skew and the information presentation function is disposed on the other side of the disk substrate by printing, asymmetry of the respective sides of the disk substrate can be eliminated, whereby skew can be effectively suppressed so that the flatness of the recording layer is well maintained, and thus a very stable recording/reproducing operation is performed. Therefore, the optical disc according to the present invention can be applied to high recording density and increased transmission speed of signals for recording/reproduction.

Claims (8)

1. An optical disc, comprising:

a disk substrate having a recording layer formed on a first surface thereof;

a transparent protective film provided on the recording layer formed on the first surface of the disk substrate;

a printed mark film provided on the second side of the disk substrate, having the same film quality and film structure as the transparent protective film, and having a function of reducing skew and an information presentation function by mark printing.

2. The optical disc of claim 1, wherein the transparent protective film is a synthetic resin sheet adhered to the first face of the disc substrate with an adhesive material, and the print label film is a synthetic resin sheet adhered to the second face of the disc substrate with an adhesive material.

3. The optical disc of claim 2, wherein the synthetic resin sheet is made mainly of a thermoplastic polymer through which light can pass.

4. The optical disc of claim 1, wherein the transparent protective film is a synthetic resin layer directly laminated on the recording layer formed on the disc substrate, and the print mark film is a synthetic resin layer printed on the second face of the disc substrate.

5. The optical disc of claim 4, wherein the synthetic resin layer is mainly made of a thermoplastic polymer through which light can pass.

6. The optical disc of claim 1, wherein a formation area of the print mark film on the second side of the disc substrate corresponds to a formation area of the transparent film on the first side of the disc substrate.

7. The optical disc of claim 1, wherein a moisture barrier film is further disposed between the second side of the disc substrate and the printed indicia film.

8. The optical disc of claim 1, wherein a water-permeable protective layer having a low water permeability is provided inside the disc substrate.