JP2000235734A - Optical recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deformation in a substrate such as warpage and shrinkage, to ensure satisfactory rotating performance and to attain satisfactory adaptation to the increase of recording density by laminating two or more 1st and 2nd resin layers which transmit incident light and comprise different materials different from each other in physical and/or mechanical characteristics to form the substrate. SOLUTION: A signal recording layer 3, a light reflecting layer 4 and a protective coat 5 are successively laminated on a substrate 2 to obtain the objective optical disk. The substrate 2 has a sandwich structure obtained by forming 1st and 2nd skin layers 6a, 6b on both principal faces of a core layer 7. The skin layers 6 are formed with a material having a lower water absorption than the core layer 7 so as to inhibit the warpage of the optical disk. The core layer 7 is formed with a material having a higher glass transition temperature and a larger mechanical internal loss than the skin layers 6 so as to inhibit the warpage of the optical disk even at a high temperature and to prevent the resonance phenomenon of the optical disk in rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a signal recording layer formed on a substrate and a method of manufacturing the same. The present invention relates to an optical recording medium capable of sufficiently coping with a higher recording density and a method for manufacturing the same.

[0002]

2. Description of the Related Art An optical recording medium is used for a recording / reproducing apparatus, and the recording / reproducing apparatus records and / or reproduces various information such as, for example, audio information, image information, and character information. This is a recording medium on which reproduction is performed. An optical recording medium generally has a disk shape. For example, an optical disk in which a recording signal is written in advance by a physical uneven shape called a pit, or a recording signal using a phase change of a signal recording layer is used. There are types of phase-change optical disks to be written, and magneto-optical disks in which recording signals are recorded and reproduced using the magneto-optical effect of the signal recording layer.

[0003] The optical recording medium is provided with recording portions for recording signals called recording tracks in the circumferential direction on the main surface. Then, the recording / reproducing device irradiates the recording track with light to perform recording / reproducing of a recording signal.

In an optical recording medium, for example, a land / groove having a physical uneven shape corresponding to a recording track,
A fine concavo-convex pattern such as pits written in advance is formed on the signal recording surface. These fine concavo-convex patterns are usually formed by injection molding a disk substrate with a resin material onto a side of the disk substrate to be a signal recording surface by a stamper.

[0005]

In the above-described injection molding process for a disk substrate, the effects of pressure change and temperature change when the molten resin material is injected and filled, friction between the resin material and the mold, and the like are considered. As a result, stress is generated in the resin material. In the injection molding process, the stress generated in the resin material is reduced in the process until the molten resin material is cooled and hardened in the mold. However, the residual stress remains in the completed disk substrate. In an optical recording medium, if internal stress remains on the disk substrate, deformation such as warpage or undulation, and non-uniform birefringence distribution may occur.

[0006] Further, since the disk substrate is formed of a resin material, it is difficult to avoid shrinkage and deformation during the injection molding process, particularly during the cooling process. Specifically, the disk substrate is deformed into a propeller shape when the outer peripheral portion has a larger contraction than the inner peripheral portion. Further, the disk substrate is deformed into a bowl shape when the shrinkage at the outer peripheral portion is larger than that at the inner peripheral portion.

Therefore, in the conventional injection molding process, in order to minimize the shrinkage deformation and the deformation of the disk substrate due to the residual internal stress described above, the mold clamping pressure of the mold is reduced or the injection speed of the resin material is reduced. Complicated work such as slowing down or reducing the injection pressure of the resin material is required. Further, in the conventional injection molding process, such a deformation causes a problem that sinks (dents) or bulges occur on the outer peripheral portion of the disk substrate, and it is difficult to transfer a concave / convex pattern of the stamper accurately. have.

For this reason, in the conventional injection molding process, a resin material having a small molecular weight and having high fluidity is used, or the temperature at the time of injection of the resin material and the temperature of a mold are increased, so that a disk is formed. The birefringence of the substrate is reduced, and transferability from the stamper is ensured. However, in the conventional injection molding process, there is a problem that mechanical properties such as rigidity of the disk substrate are deteriorated by reducing the molecular weight of the resin material. In addition, in the conventional injection molding process, when the mold temperature is increased, there is a problem that thermal deformation occurs when the disk substrate is taken out or a molding cycle is lengthened.

On the other hand, in recent years, it has been desired to increase the recording density of the optical recording medium in response to the downsizing of the recording / reproducing apparatus and the increase in the capacity of the recording signal. As described above, when the optical recording medium is constituted by a disk substrate having low rigidity or when the disk substrate is deformed, a high NA having a small depth of focus corresponding to a high recording density is used.
When used for an optical system, there is a problem that it is difficult to perform normal recording and reproduction.

[0010] Further, it is desired that the optical recording medium has a higher number of revolutions at the time of recording / reproduction in response to the higher speed of the recording / reproduction operation. Therefore, the optical recording medium is required to have good resonance characteristics of the disk substrate and to be able to perform stable recording and reproduction even at high speed rotation.

In the optical recording medium, as described above, the disk substrate has various physical characteristics / mechanical characteristics such as transferability from a stamper, in-plane and birefringence in the thickness direction, water absorption, rigidity, resonance characteristics, and the like. It is required to satisfy the characteristics. However, it is difficult for these various physical / mechanical properties to be sufficiently satisfied by a single resin material.

Accordingly, the present invention provides an optical recording medium which has sufficient rotation performance without deformation of a disk substrate such as warpage or sink mark, and which can sufficiently cope with high recording density, and a method of manufacturing the same. The purpose is to do.

[0013]

An optical recording medium according to the present invention comprises at least a signal recording layer formed on a substrate,
An optical recording medium on which recording signals are recorded and / or reproduced from the signal recording layer by incident light incident from the substrate side. The substrate is formed by laminating two or more first resin layers and second resin layers. In addition, the first resin layer and the second resin layer are formed of different materials having a property of transmitting the above-mentioned incident light and having different physical characteristics and / or mechanical characteristics.

In the optical recording medium configured as described above, each of the substrates is formed by laminating a first resin layer and a second resin layer having a property of transmitting incident light. The resin material for forming the resin layer is appropriately selected to provide excellent physical properties and / or mechanical properties as a whole. In addition, since the substrate is formed of a material having a property of transmitting the incident light, the incident light incident from the substrate side can be transmitted, thereby affecting optical recording / reproducing characteristics. Absent.

Further, a method of manufacturing an optical recording medium according to the present invention comprises forming at least a signal recording layer on a substrate,
Recording and / or reproduction of a recording signal is performed on the signal recording layer by the incident light incident from the substrate side, and the first resin layer and the first resin layer having a property of transmitting the incident light to the signal recording layer. This is a method used when injection molding a substrate of an optical recording medium formed by the second resin layer. In particular, in the method for manufacturing an optical recording medium according to the present invention, the second resin layer is formed by a two-color molding process using a different material having different physical characteristics and / or mechanical characteristics from the first resin layer. .

Therefore, according to such a method for manufacturing an optical recording medium, the first resin layer and the second resin layer having a property of transmitting incident light are laminated to form a substrate. By appropriately selecting a resin material for forming each resin layer, an optical recording medium having excellent physical and / or mechanical properties as a whole can be manufactured. Further, since the substrate is formed of a material having a property of transmitting incident light, an optical recording medium that can transmit incident light incident from the substrate side can be manufactured.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, a signal recording layer formed of a phase change material is provided as an optical recording medium, and recording and reproduction of a recording signal are performed by irradiating the signal recording layer with light having different intensities. A phase-change type optical disc which records and reproduces a recording signal by a so-called phase-change recording method will be described as an example. However, the present invention is widely applicable to an optical disc that records and reproduces a recording signal on and from an optical recording medium. For example, a read-only optical disc and the like that can only record a recording signal on an optical recording medium can be used. Good.

In the following description, an optical disc 1 as shown in FIGS. 1 and 2 will be described. Optical disk 1
As shown in FIG. 1, the whole has a substantially disk shape, and a center hole 1a is perforated at the center thereof.

As shown in FIG. 2, the optical disc 1 has a signal recording layer 3, a light reflection layer 4, and a protective film 5 sequentially laminated on a substrate 2. The substrate 2 is composed of a skin layer 6 and a core layer 7, and a first skin layer 6a and a second skin layer 6b are formed on both main surface sides of the core layer 7, respectively, to form a so-called sandwich structure. It is supposed to be.

The optical disk 1 is used detachably with respect to an optical disk device (not shown), and has a recording / reproducing head (not shown) provided in the optical disk device. The reproduction of the signal is performed. In the optical disc 1, at the time of signal reproduction, a laser beam 11 is condensed by an optical lens 10 provided in a recording / reproducing head, and this laser beam 11 is transmitted from the substrate 2 to the signal recording layer 3.
Is incident toward. Then, the optical disc device detects the return light that is reflected by the laser light 11 on the signal recording layer 3 and the light reflection layer 4 and returned by the pickup.
The recording signal is recorded on and reproduced from the optical disc 1.

In the substrate 2, the skin layer 6 and the core layer 7 are formed of different materials having a light transmitting property to the laser beam 11 and different physical properties and / or mechanical properties. . In the optical disc 1, the laser light 11 can be incident on the signal recording layer 3 from the substrate 2 side because the substrate 2 has a light transmitting property with respect to the laser light 11.

The first skin layer 6a is formed on the substrate 2
The surface on which the laser light 11 is incident, that is, the light incident surface 2
It is formed on the a side. In addition, the second skin layer 6b
The substrate 2 is formed on the surface on which the signal recording layer 3 is formed, that is, on the signal recording surface 2b side.

The substrate 2 has a concavo-convex pattern 2c formed on a signal recording surface 2b. Uneven pattern 2c
Is a pattern in which fine irregularities such as pregrooves are formed as a change in physical shape, and serves as a positioning reference when the optical disc apparatus performs recording and reproduction on the optical disc 1. When the optical disc 1 is a read-only optical disc such as a CD (Compact Disc), the concavo-convex pattern 2c may be a pit indicating a recording signal.

The skin layer 6 is desirably formed of a material having good fluidity. Thereby, the skin layer 6
Is excellent in transferability. Therefore, the concavo-convex pattern 2c can be reliably and accurately formed on the signal recording surface 2b of the substrate 2 on the side of the second skin layer 6b. Therefore, the optical disc 1 can form the pits indicating recording signals, the concavo-convex pattern 2c corresponding to the pre-groove and the like with high density and high precision, and can be an optical disc compatible with high recording density.

The optical disk 1 has a structure in which the skin layer 6 is formed of a material having good fluidity, so that the substrate 2
Can be reduced. Therefore, the optical disc 1 can reduce the birefringence of the laser beam 11 on the substrate 2. A resin material having good fluidity generally has a small photoelastic constant. Therefore, the optical disc 1 can stably guide the laser beam 11 incident on the substrate 2 to the signal recording layer 3 and can surely reflect the return light to the pickup, thereby coping with an increase in recording density. Even in this case, the reproduction of the recording signal can be performed stably and reliably.

The skin layer 6 is preferably formed of a material having a lower water absorption than the core layer 7. Thereby, the optical disc 1 can suppress the warp deformation caused by the skin layer 6 absorbing water and the like contained in the atmosphere.

Generally, in an optical disk, a substrate and
The water absorption of the protective film formed on the surface on which the signal recording layer is formed is different from that of the protective film, and the water absorption of the protective film is usually lower than that of the substrate. Therefore, when the substrate absorbs moisture and the like in the air, the substrate is warped so that the substrate side becomes convex, and the substrate is dehydrated in a dry environment,
Warpage deformation occurs so that the signal recording layer side becomes convex. In particular, the external environment of an optical disc often changes drastically when it is mounted on a recording / reproducing apparatus, and when water absorption deformation occurs on a substrate, the occurrence of tracking errors and focus errors increases, and normal recording / reproducing is performed. It will be difficult to do.

For example, D which is one of the optical disc standards
In VD (Digital Versatile Disk), the allowable warp deformation angle is 0.4 °. This DVD is usually formed by laminating two substrates each having a thickness of 0.6 mm made of polycarbonate having a water absorption of 0.3% or more on the side where the signal recording layer is formed. Therefore, in the DVD, the water-absorbing deformation is suppressed by canceling out the warp stress of each substrate.

However, when the optical disk is composed of a single substrate, it is difficult to perform normal recording and reproduction due to the substrate being deformed by water absorption as described above.

Therefore, in the optical disk 1, the substrate 2
It is preferable that the skin layer 6 formed on the side facing the outside is formed of a material having a low water absorption. Thereby, the optical disc 1 can suppress the water absorption deformation of the substrate 2 and can perform stable and reliable reproduction even when a recording signal is recorded at a high density.

Specifically, it is desirable that the skin layer 6 is formed of a material having a water absorption of 0.15% or less. Thereby, the optical disc 1 is, for example, 0.6 mm
The warp deformation angle of the substrate 2 when the substrate 2 is formed to a thickness of 0.
It can be suppressed within 4 mm. Furthermore, the optical disk 1
Preferably, the skin layer 6 is formed of a material having a water absorption of 0.1% or less. As a result, the optical disk 1 is mounted on the substrate 2 due to a change in temperature or humidity in the use environment.
Can be suppressed to a negligible extent.

Examples of the material for forming the skin layer 6 include polycarbonate ST-3000 (manufactured by Teijin Chemicals Limited), Zeonex E-28R which is a thermoplastic cyclic olefin resin (manufactured by Zeon Corporation), and acrylic resin. A synthetic resin such as PET VH (manufactured by Mitsubishi Rayon Co., Ltd.) is exemplified.

The core layer 7 is desirably formed of a material having a higher glass transition temperature than the skin layer 6. Thereby, in the optical disc 1, the heat resistance of the substrate 2 is improved. Therefore, even when the optical disk 1 is exposed to a high temperature due to heat or the like generated inside the disk drive device, warpage deformation can be suppressed.

The core layer 7 is desirably formed of a material having a higher mechanical internal loss than the skin layer 6. Thereby, the optical disc 1
When mounted on a disk drive and driven to rotate, it is possible to prevent a large vibration from occurring due to a resonance phenomenon. Therefore, the optical disc 1 can perform stable and reliable reproduction.

In the optical disk 1, the rigidity of the substrate 2 is increased and the bending strength in the radial direction is increased because the core layer 7 is formed of a material having high mechanical strength. Therefore, the optical disk 1 can have sufficient strength against warpage deformation even when the thickness of the substrate 2 is reduced as compared with the conventional optical disk. Therefore, the optical disk 1 can easily be used as an optical disk in which the thickness of the light transmitting layer through which the recording / reproducing light passes is formed with the increase in NA.

In general, an optical disk apparatus has a relation in which the inertia of a rotary drive mechanism increases in proportion to the square of the weight of the optical disk. Therefore, the optical disk 1
By reducing the thickness of the substrate 2, the weight is reduced as compared with the conventional optical disk, the load on the rotation drive mechanism of the optical disk device is reduced, and the power consumption of the optical disk device can be reduced. it can.

The material for forming the core layer 7 is as follows.
For example, synthetic resins such as polycarbonate 9000TG (manufactured by Teijin Chemicals Ltd.), ZEONEX L-6 (manufactured by Nippon Zeon Co., Ltd.), and Acrypet IR50 (manufactured by Mitsubishi Rayon Co., Ltd.) are exemplified.

It is desirable that the skin layer 6 and the core layer 7 have a refractive index within 1.55 ± 0.1 as a whole. Thereby, the optical disc 1 can satisfy the optical characteristics defined by the standards of various optical discs conventionally used. Therefore, the optical disk 1
Can easily correspond to various types of optical disks conventionally used.

The signal recording layer 3 is formed on the signal recording surface 2 b of the substrate 2.
It is formed in a thin film on top. The signal recording layer 3 is formed of a phase change material that undergoes a reversible phase change between a crystal and an amorphous phase by a laser beam 11 emitted from an optical disk device. As the phase change material, for example, a simple chalcogen, a chalcogen compound, or the like is used. Specifically, each of Te and Se alone, Ge-Sb-Te, Ge
-Te, In-Sb-Te, In-Se-Te-Ag,
In-Se, In-Se-Tl-Co, In-Sb-S
A chalcogenite-based material such as e, Bi ₂ Te ₃ , BiSe, Sb ₂ Se ₃ , Sb ₂ Te ₃ is used.

The light reflection layer 4 is formed in a thin film on the signal recording layer 3, has a function as a reflection layer for reflecting light transmitted through the signal recording layer 3, and is directed toward the signal recording layer 3. The laser beam 11 has a function as a heat sink for preventing heat from being stored in the signal recording layer 3 by the irradiated laser beam 11. As a material for forming the light reflection layer 4, for example, a metal element, a metalloid element, a semiconductor element, and a compound thereof are preferably used alone or in combination. The light reflection layer 4 is, for example,
u, Al, etc.

The protective film 5 is formed as a thin film on the light reflecting layer 4 by, for example, an ultraviolet curing resin. The protective film 5 has a function of preventing the signal recording layer 3 and the light reflection layer 4 from being oxidized, and also has a function of preventing the respective layers from being damaged. The protective film 5 is made of a thin disk made of various resin sheets, and is made of an ultraviolet curable resin.
It may be bonded and fixed on the top.

The optical disk 1 configured as described above is
Since the substrate 2 is formed by the skin layer 6 and the core layer 7, various physical and / or mechanical characteristics can be combined.

That is, in the optical disc 1, since the light incident surface 2a side and the signal recording surface 2b side of the substrate 2 are formed by the skin layer 6, it is possible to prevent the substrate 2 from absorbing water and the like in the air. Thus, warpage can be prevented, and a fine uneven pattern 2c can be formed on the signal recording surface 2b side with high density and high accuracy. As a result, the optical disk 1 has, for example, a depth of 16
Fine uneven pattern 2 with 0 nm and pitch of about 0.5 μm
c can be formed with high precision, and stable reproduction can be performed.

The optical disk 1 has high heat resistance, high rigidity, and high mechanical internal loss because the core of the substrate 2 is formed by the core layer 7. Therefore, the optical disc 1 has sufficient strength, can suppress the resonance phenomenon at the time of rotational driving, and can suppress deformation such as warpage and sink.

In other words, the optical disc 1 has a structure in which the substrate 2 is formed by the skin layer 6 and the core layer 7 so that the uneven pattern 2c is finely formed in response to the increase in recording density. Thus, stable and reliable reproduction can be performed.

In the optical disc 1, the skin layer 6 and the core layer 7 are formed so as to transmit light to the laser light 11, so that the laser light 11 is incident from the substrate 2 side. , The light can be transmitted toward the signal recording layer 3.

The optical disc 1 may have a structure including a dielectric layer in addition to the above-described structure. Since the optical disc 1 includes the dielectric layer, it is possible to control the optical characteristics such as the reflectance and the thermal characteristics by the multiple interference effect.

In the above description, the first skin layer 6a and the second skin layer 6b are formed on both main surface sides of the substrate 2, respectively. However, the present invention is not limited to such a configuration. Not something. An optical disc to which the present invention is applied has a first resin layer and a second resin layer formed of different materials having different properties of physical properties and / or mechanical properties while having a property of transmitting incident light. You only have to have it. Specifically, for example, the substrate 2 may be formed in a two-layer structure as in an optical disk 20 as shown in FIG.

Hereinafter, an optical disc 20 in which the substrate 2 has a two-layer structure will be described. The optical disk 2
0 is different from the above-described optical disc 1 only in the layer structure of the substrate 2. Therefore, in the following description, description of the same or equivalent parts as the above-described optical disc 1 will be omitted, and the same reference numerals will be given in the drawings.

The substrate 2 of the optical disk 20 has a two-layer structure.
The functions and materials of the three resin layers are the same as those of the skin layer 6 and the core layer 7 of the optical disc 1 described above. Therefore, in the following description, the two resin layers constituting the substrate 2 will be referred to as the skin layer 6 and the core layer 7 for convenience.

As shown in FIG. 3, the optical disk 20 has a substrate 2 composed of a skin layer 6 and a core layer 7.
The skin layer 6 is formed on the surface of the substrate 2 on which the signal recording layer 3 is formed, that is, on the signal recording surface 2b side. The core layer 7 is formed on the surface of the substrate 2 on the side where the laser light 11 is incident, that is, on the light incident surface 2a side. Further, the skin layer 6 and the core layer 7 are formed of a material having a light-transmitting property with respect to the laser beam 11 for performing recording and reproduction.

Since the optical disk 20 has the skin layer 6 on the signal recording surface 2b side, a fine uneven pattern 2c can be formed on the signal recording surface 2b side with high density and high precision. In addition, the optical disk 20 has sufficient strength and suppresses a resonance phenomenon at the time of rotational driving because the core layer 7 is formed of a material having high heat resistance and high rigidity and mechanical internal loss. And deformations such as warpage and sink marks can be suppressed.

Therefore, the optical disk 20 can perform stable and reliable reproduction even when a fine uneven pattern is formed in response to the increase in recording density, and can perform laser light irradiation from the substrate 2 side. 11 can be made incident and transmitted toward the signal recording layer 3.

In the optical disc 20, the skin layer 6 is formed on the signal recording surface 2b side and the core layer 7 is formed on the light incident surface 2a side.
May be reversed. That is, the light incident surface 2
The skin layer 6 may be formed on the side a, and the core layer 7 may be formed on the side of the signal recording surface 2b. In this case, the optical disc 20
It is possible to suppress the substrate 2 from absorbing moisture and the like in the air, and to prevent warpage.

In the above description, the optical disk 1
Although the optical disk 20 is a phase change optical disk, the present invention is not limited to such a configuration.
INDUSTRIAL APPLICABILITY The present invention can be widely applied to an optical recording medium for recording and reproducing a recording signal, and can be applied to, for example, a magneto-optical disk. In this case, the signal recording layer 3 is formed with a magneto-optical recording layer or the like that loses coercive force due to a temperature rise exceeding the Curie temperature and reverses magnetization in the direction of an external magnetic field. The magneto-optical recording layer is, for example, Tb-
It is formed of an amorphous alloy thin film such as Fe—Co or the like, and has a configuration having magneto-optical characteristics such as the Kerr effect and the Faraday effect. The present invention can also be applied to a read-only optical disk. In this case, the optical disc 1 is configured without, for example, the signal recording layer 3, and the pits and projections 2c of the substrate 2 are formed in advance in accordance with the recording signals.

Next, the optical disk 1 shown in FIGS.
A method of manufacturing the device will be described. Substrate 2 of optical disk 1
Is an injection molding apparatus 30 as shown in FIGS. 4, 5 and 6.
And molded through a two-color molding process.

The injection molding apparatus 30 is provided with a mold 31 into which a molten resin is injected in a mold-clamped state, and a mold 31 for molding the molten resin.
A first cylinder 32 and a second cylinder 33 which are connected to an injection port 31a provided in the mold part 31 to inject and fill the molten resin into the mold part 31; And a first hopper 34 and a second hopper 35, into which a resin serving as a raw material of the substrate 2 is introduced.
Screw 37, a first hydraulic motor unit 38 and a second hydraulic motor unit 39 for rotating and driving the first screw 36 and the second screw 37, respectively, and a mold clamping operation for opening and closing the mold unit 31. And a cylinder 40.

First cylinder 32 and second cylinder 33
Is provided with a first screw 36 and a second screw 37, respectively. In addition, the first cylinder 32 and the second cylinder 33 are provided with a plurality of heaters 41 on the outer periphery thereof. Further, the first cylinder 32 and the second cylinder 33 are respectively provided with resin passage portions 32a as passages for the resin material introduced therein.
And a resin passage portion 33a. An injection control section 32b and an injection control section 33b for controlling the injection amount of the resin material are provided at the tip portions of the resin passage section 32a and the resin passage section 33a, respectively. And
At the tip of the injection control unit 32b and the injection control unit 33b,
A connecting portion 42 that connects the resin passage portions 32a and the resin passage portions 33a is provided.

The first cylinder 32 includes a first hopper 34
Is kneaded by the first screw 36 while being heated by the heater 41. Then, the kneaded second resin material 51 is sent to the tip of the first cylinder 32 along the groove of the first screw 36.

The second cylinder 33 is a first cylinder 3
Similarly to 2, the first resin material 50 introduced from the second hopper 35 is kneaded by the second screw 37 while being heated by the heater 41. Then, the kneaded first resin material 50 is sent to the distal end of the second cylinder 33 along the groove of the second screw 37.

Incidentally, the second resin material 51 and the first resin material 50 are cooled and hardened as described later, and finally become the core layer 7 and the skin layer 6 of the optical disk 1, respectively. It is. Therefore, the second resin material 51 and the first resin material 50 need to be transparent to the laser beam 11 that records and reproduces a recording signal on the optical disc 1. Further, the second resin material 51 and the first resin material 50 are preferably materials that are desirable for forming the core layer 7 and the skin layer 6 as described above.

As shown in detail in FIG. 6, the mold part 31 is provided with a fixed mold 31b having an injection port 31a into which resin is injected, and is provided opposite to and fixed to the fixed mold 31b. And a movable mold 31c that operates. Movable mold 3
1c is connected to a mold clamping cylinder 40 via a piston 43, and is driven by the mold clamping cylinder 40 so as to be freely movable toward and away from a fixed mold 31b fixedly installed. In the mold part 31, when the fixed mold 31b and the movable mold 31c are clamped, the closed internal space becomes a cavity 31d.

The movable mold 31 is fixed to the fixed mold 31b.
A stamper 44 on which a predetermined concavo-convex pattern corresponding to a recording signal to be recorded on the optical disc 1 is formed is attached to the surface opposite to the surface c. At the center of the fixed mold 31b and the movable mold 31c, a not-shown perforating means for forming a center hole in the substrate 2 by performing gate cutting is provided. The center hole of the substrate 2 becomes the center hole 1a in the optical disc 1.

The injection molding apparatus 30 configured as described above
To manufacture the substrate 2 of the optical disc 1 using
A first method of simultaneously injecting the first resin material 50 and the first resin material 50 at different injection speeds, and a second resin material 51.
And a second method of injecting the first resin material 50 at the same injection speed with a time difference.

In the first method, first, the second resin material 5
1 is introduced from the first hopper 34 into the first cylinder 32. Then, the first hydraulic motor unit 38 drives the first screw 36 to rotate, so that the second resin material 51 is kneaded and the first screw 3
6 to the tip of the first cylinder 32. At this time, the second resin material 51 is heated by the heater 41 provided on the outer peripheral portion of the first cylinder 32, and the temperature rises from the inside due to the addition of frictional heat generated by the kneading action. State.

Further, the first resin material 50 is introduced from the second hopper 35 into the second cylinder 33. Then, the second screw 37 is rotated by the second hydraulic motor unit 39 to knead the first resin material 50 and to move the second cylinder 33 along the groove of the second screw 37. Send to the tip. At this time, similarly to the second resin material 51, the first resin material 50 is heated by the heater 41 provided on the outer peripheral portion of the second cylinder 33, and friction heat generated by the kneading action is applied. As a result, the temperature also rises from the inside and becomes molten.

Here, the movable mold 31c of the mold section 31 is
As shown in FIG. 6, the mold is moved to a position where it comes into contact with the fixed mold 31b by the mold clamping cylinder 40. And the first
By the screw 36 and the second screw 37,
The second resin material 51 and the first resin material 50 are simultaneously injected from the injection port 31a of the mold part 31 into the cavity 31d. At this time, the injection control unit 32b and the injection control unit 33b reduce the injection speed of the second resin material 51 injected from the first cylinder 32 to the second cylinder 33.
Is made slower than the injection speed of the first resin material 50 injected from the first resin material 50.

Then, the second resin material 51 is injected and filled in the cavity 31d so as to extrude the first resin material 50. As a result, as shown in FIG.
b and the first resin material 50 on the side in contact with the movable mold 31c.
Is distributed, and the second resin material 51 is distributed inside the first resin material 50.

Then, the mold portion 31 is cooled by a temperature adjusting means (not shown) provided in the mold portion 31, so that the second resin material 51 filled in the cavity 31d and the first resin material 51 are cooled. The resin material 50 is cooled and hardened.
As a result, the second resin material 51 becomes the core layer 7 of the substrate 2 in the optical disc 1, and the first resin material 50 becomes the skin layer 6 of the substrate 2. At this time, the concavo-convex pattern provided on the stamper 44 is transferred to the first resin material 50 on the stamper 44 side, and finally becomes the concavo-convex pattern 2c of the optical disk 1.

Thereafter, a hole serving as a center hole 1a is formed in the center of the substrate 2 by a punching means.
After 1c performs the mold opening operation, the substrate 2 is taken out by the substrate taking out means (not shown).

The second method is the same as the first method described above, up to the step of sending the second resin material 51 and the first resin material 50 to the injection controller 32b and the injection controller 33b, respectively. is there.

Thereafter, by controlling the injection time and the injection amount by the injection control section 33b, the first resin material 50 is injected into the cavity 31d of the mold section 31 for a short time, so-called short shot. After that, when the first resin material 50 is still in a semi-molten state, the injection control unit 32b controls the injection amount and the like to thereby obtain the second resin material.
Is injected into the cavity 31d of the mold part 31.

At this time, since the first resin material 50 is cooled and hardened from the surface, it is in a semi-molten state inside. Therefore, the second resin material 51 is filled so as to extrude the inner part of the first resin material 50. Therefore, also in the second method, the state is as shown in FIG. 6, as in the first method.

Thereafter, through a cooling step, the second resin material 51 finally becomes the core layer 7 of the substrate 2 in the optical disk 1 and the first resin material 50 becomes the substrate 2 in the second method. Of the skin layer 6. Then, a hole is made in the center of the substrate 2 by the perforating means, and after the movable mold 31c performs the mold opening operation, the substrate 2 is taken out by the substrate taking out means (not shown).

In the second method, a short shot of the second resin material may cause sink marks and transfer failure. However, since the second resin material 51 occupies the inside and raises the internal pressure, The transfer state on the second resin material is also improved.

Then, the signal recording layer 3 and the light reflection layer 4 are sequentially laminated on the substrate 2 formed by the above-described first method or second method by a thin film forming technique such as sputtering. Then, for example, an ultraviolet curable resin is applied on the light reflecting layer 4 by a spin coating method, and the protective film 5 is formed by irradiating ultraviolet rays, whereby the optical disc 1 shown in FIG. 2 is manufactured.

Next, a method of manufacturing the optical disc 20 shown in FIG. 3 will be described. The substrate 2 of the optical disk 20 is also formed by a two-color forming process using the above-described injection molding apparatus 30. However, in the manufacturing method of the optical disk 20, the mold part 31 of the injection molding apparatus 30 is used.
Only the structure of the mold part 6 shown in FIG.
0 is used.

The mold section 60 includes a fixed mold 61 having an injection port 60a into which the resin material is injected, and a first movable mold 62 provided opposite to the fixed mold and operating to approach and separate. ,
A second movable mold 63 provided inside the cavity 60b closed by the fixed mold 61 and the first movable mold 62 in the mold-clamped state and opposing to and moving away from the fixed mold 61. And an outer peripheral ring 64 interlocked with the second movable mold 63
And

The first movable mold 62 is a mold clamping cylinder 4
0 to move toward and away from the fixed mold 61. The fixed die 61 is provided with a nozzle 61a penetrating from the injection port 60a into the cavity 60b. Then, the molten resin material is injected and filled into the cavity 60b from the injection port 60a via the nozzle 61a.

The second movable mold 63 is moved in a direction indicated by an arrow A in FIG.
Is movable independently of the first movable mold 62. The outer ring 64 moves toward and away from the fixed mold 61 together with the second movable mold 63. The second movable mold 63 is provided with a stamper 65 having a concave / convex pattern formed on a surface facing the fixed mold 61 in accordance with a recording signal to be recorded on the optical disc 1.
At the center of the first movable mold 62 and the second movable mold 63, a punching means (not shown) for forming a central hole in the substrate 2 by performing gate cutting is provided. This substrate 2
Is the center hole 1a in the optical disc 1.
It is what becomes.

Using the injection molding apparatus 30 having the mold section 60 configured as described above, the substrate 2 of the optical disc 20 is used.
When manufacturing the second resin material 51 and the first resin material 50 in the same manner as described above,
b and the injection controller 33b. At this time, the mold part 60 is in a state where the first movable mold 62 and the outer ring 64 are in contact with the fixed mold 61 as shown in FIG.

Next, the first resin material 50 is
It is injected and filled into the cavity 60b through one nozzle 61a. Thereafter, the fixed mold 61, the second movable mold 63, and the outer peripheral ring 64 are cooled by a temperature adjusting means (not shown) provided in the mold section 60, so that the cavity 60b is filled. The first resin material 50 is cooled and hardened, and the concavo-convex pattern of the stamper 65 is transferred to the surface of the first resin material 50. At this time stamper 6
The concavo-convex pattern transferred from 5 to the first resin material 50 becomes the concavo-convex pattern 2c of the substrate 2 in the optical disk 1 to be finally completed.

Next, after the first resin material 50 has sufficiently hardened, as shown in FIG. 9, the second movable mold 63 is moved in the direction shown by the arrow B in the figure by a hydraulic mechanism (not shown). The bottom surface 63a of the second movable mold 63 is brought into contact with the inner bottom surface 62a of the first movable mold 62. At this time, air is injected from the fixed mold 61 side by an air injection mechanism (not shown), and the cured first resin material 50 is moved together with the second movable mold 63.

Next, as shown in FIG. 10, the space is injected and filled with the second resin material 51 by the fixed mold 61, the outer peripheral ring 64 and the first resin material 50 in the same manner as described above. Then, the fixed mold 61, the second
By cooling the movable mold 63 and the outer peripheral ring 64, the second resin material 51 is cooled and hardened. This allows
The second resin material 51 becomes the core layer 7 of the substrate 2 in the optical disc 1, and the first resin material 50 becomes the skin layer 6 of the substrate 2. Then, a hole is made in the center of the substrate 2 by the perforating means, and the first movable mold 62 and the second movable mold 63 perform the mold opening operation, and then the substrate removing means (not shown). Is taken out.

Thereafter, the signal recording layer 3, the light reflection layer 4, and the protective film 5 are sequentially formed on the substrate 2 in the same manner as in the case of manufacturing the optical disk 1 described above, whereby the structure shown in FIG.
Is manufactured.

In the above description, the inside of the cavity 60b is
First, the first resin material 50 is injected and then filled, and then the second resin material 51 is injected and filled. However, the second resin material 51 is first injected and filled, and then the first resin material 50 is injected and filled. You may do it. Thereby, the optical disk 20
Has a core layer 6 formed on the signal recording surface 2b side and a skin layer 7 formed on the light incident surface 2a side.

As described above, according to the method for manufacturing the optical disk 1 and the optical disk 20, an optical disk having the substrate 2 on which the skin layer 6 and the core layer 7 are laminated can be manufactured by the two-color molding process. . Further, as described above, by manufacturing the skin layer 6 and the core layer 7 in the same mold portion, the substrate 2 can be formed very efficiently.

In the above-described step of forming the substrate 2, it is desirable to use, as the first resin material 50, a resin material having a higher fluidity than the second resin material 51 in a molten state. Thereby, the first resin material 5
The fine uneven pattern formed on the stamper 44 or the stamper 65 can be transferred to 0 with high precision. Therefore, the optical disk 1 or the optical disk 20 to be finally completed can be adapted to high recording density.

In the step of forming the substrate 2, the first
Since the resin material 50 is a resin material having a higher fluidity than the second resin material 51 in a molten state, the residual stress generated in the substrate 2 can be reduced.
Therefore, in the optical disk 1 or the optical disk 20 finally completed, the birefringence of the laser beam 11 on the substrate 2 can be reduced.

A resin material having good fluidity generally has a small photoelastic constant. Therefore, the optical disk 1 or the optical disk 20 can stably guide the laser beam 11 incident on the substrate 2 to the signal recording layer 3 and can surely reflect the return light to the pickup. Therefore, in response to the increase in recording density, the substrate 2
Optical disc 1 capable of stably and reliably reproducing recorded signals even when a fine uneven pattern is formed thereon.
Alternatively, the optical disc 20 can be manufactured.

According to the method for manufacturing an optical disk according to the present invention, not only a phase-change optical disk such as the optical disk 1 and the optical disk 20 described in the above description, but also a magneto-optical disk and a read-only optical disk It goes without saying that the present invention can be widely applied to an optical recording medium for recording and reproducing a recording signal.

[0092]

EXAMPLES Hereinafter, specific examples of the present invention will be described based on experimental results. In the following description, in order to examine the resonance characteristics and the water absorption characteristics of the optical disk to which the present invention is applied, the following substrate was prepared and evaluated.

Example 1 In Example 1, as in the case of the optical disk 1, a substrate having a three-layer structure in which skin layers were formed on both main surfaces of the core layer, respectively, was manufactured. First, the following materials were prepared as a resin material for the skin layer and a resin material for the core layer.

<Resin Material for Skin Layer> Resin material: ZEONEX E-28R (manufactured by Zeon Corporation) Glass transition temperature: 136 ° C. Flexural modulus: 23,000 kgf / cm ² Thermal deformation temperature: 122 ° C. Water absorption: 0.01% or less Refractive index: 1.53 nd25 Specific gravity: 1.01 Photoelastic constant: 2 × 10 ^-13 cm ² / dyne Loss tangent (tan δ): 0.004 <Resin material for core layer> Resin material: ZEONEX L-6 (manufactured by Zeon Corporation) Glass transition temperature: 163 ° C Flexural modulus: 28,000 kgf / cm ² Thermal deformation temperature: 141 ° C Water absorption: 0.01% or less Refractive index: 1.53 nd25 Specific gravity: 1.03 photoelastic ^{constant: 6.5 × 10 -13 cm 2 /} dyne loss tangent (tan [delta): 0.006 the injection molding apparatus 30 shown in FIG. 4 There are, injecting and filling simultaneously injection speed of the resin material different resin material and the core layer for the skin layer, the first method described above,
Under the conditions shown below, a thickness of 1.2 mm and a diameter of 12 cm
Was formed.

<Substrate molding conditions> Heating temperature of resin material for skin layer: 330 ° C Heating temperature of resin material for core layer: 360 ° C Heating temperature of nozzle portion: 320 ° C Mold portion temperature: 130 ° C Gold Cooling time of mold part: 16 seconds Depth of uneven pattern of stamper: 100
nm Track pitch of stamper uneven pattern: 0.7
μm Among the characteristics of the resin material of each layer described above, the loss tangent indicates the mechanical internal loss of the resin material, and this measurement is specified in JIS K7198.

Example 2 In Example 2, as in Example 1 described above, a substrate having a three-layer structure in which skin layers were formed on both main surface sides of the core layer, respectively, was produced. First, the following materials were prepared as a resin material for the skin layer and a resin material for the core layer.

<Resin Material for Skin Layer> Resin Material: Polycarbonate ST-3000 (manufactured by Teijin Chemicals Ltd.) Glass transition temperature: 145 ° C. Flexural modulus: 28,700 kgf / cm ² Heat deformation temperature: 133 ° C. Water absorption: 0.15% Refractive index: 1.585 nd25 Specific gravity: 1.13 Photoelastic constant: 45 × 10 ^-13 cm ² / dyne Loss tangent (tan δ): 0.016 <Resin material for core layer> Resin material: polycarbonate AD-9000TG
(Manufactured by Teijin Chemicals Ltd.) Glass transition temperature: 143 ° C. Flexural modulus: 24,000 kgf / cm ² Thermal deformation temperature: 126 ° C. Water absorption: 0.23% Refractive index: 1.55 nd25 Specific gravity: 1.2 Photoelasticity Constant: 80 × 10 ⁻¹³ cm ² / dyne Loss tangent (tan δ): 0.009 And, similarly to the first embodiment, using the injection molding apparatus 30 shown in FIG. , Thickness 1.
A disk-shaped substrate having a diameter of 2 mm and a diameter of 12 cm was formed.

<Substrate molding conditions> Heating temperature of resin material for skin layer: 350 ° C Heating temperature of resin material for core layer: 335 ° C Heating temperature of nozzle portion: 340 ° C Temperature of mold portion: 130 ° C Gold Cooling time of mold part: 12 seconds Depth of uneven pattern of stamper: 100
nm Track pitch of stamper uneven pattern: 0.7
μm The substrate thus formed has a skin layer thickness of 0.2 to 0.2 μm.
0.3 mm, and it was confirmed that the remaining thickness was the structure of the core layer. In the substrate of Example 2, although the refractive index was slightly different between the skin layer and the core layer, no refraction abnormality occurred at the interface between the skin layer and the core layer, and the substrate was compatible with high recording density. It has been confirmed that the optical disk can be sufficiently used.

Example 3 In Example 3, a substrate for a super audio CD (hereinafter, referred to as SA-CD), which is a next-generation high-quality CD (Compact Disk), was manufactured. SA-CD has a diameter of 12c
An optical disk having a thickness of 0.6 mm and a thickness of 0.6 mm is laminated with an optically transparent light-transmitting adhesive to form a CD layer and a DVD layer. In the SA-CD standard, it is necessary to satisfy the standard of the conventional CD which has been used conventionally, and the birefringence is within 60 nm for a 0.6 mm thick optical disk alone, and the thickness of two optical disks is It is required that the thickness be within 100 nm in a state of 1.2 mm. The SA-CD has an angle of warpage of 0.6 ° or less for the CD layer and 0.4 ° for the DVD layer.
゜ is required.

In the third embodiment, the CD layer and the DVD layer were formed in the same two-layer structure as that of the above-described optical disk 20, and the CD layer and the DVD layer were bonded with a light-transmitting adhesive. The substrate for the CD layer was prepared using ZEONEX E-28R (manufactured by ZEON CORPORATION) as a skin layer and using ZEONEX E-48R (manufactured by ZEON Corporation) as a core layer. The substrate of the DVD layer uses ZEONEX L-6 (manufactured by ZEON Corporation) as a core layer and ZEONEX E-48R as a skin layer.
(Manufactured by Nippon Zeon Co., Ltd.).

Embodiment 4 In the fourth embodiment, the CD layer and the D
A substrate having a two-layer structure in which a VD layer was bonded was produced. The substrate of the CD layer is polycarbonate ST-3000.
(Teijin Chemical Co., Ltd.) single layer structure. Also,
The substrate of the DVD layer was manufactured with a single-layer structure of ZEONEX E-28R (manufactured by Zeon Corporation). That is, the optical disk of the fourth embodiment has a structure in which the CD layer and the DVD layer are each formed in a single-layer structure, and as a whole, like the optical disk 20 described above, the substrate is laminated with two types of materials.

Comparative Example 1 Using a conventional injection molding apparatus, a substrate made of a single material was manufactured to have a thickness of 1.2 mm and a diameter of 12 cm. The substrate was manufactured using ZEONEX E-28R (manufactured by Zeon Corporation), which is a resin material generally used for conventional optical disks.

Comparative Example 2 In the same manner as in Comparative Example 1 described above, a substrate made of a single material was manufactured to have a thickness of 1.2 mm and a diameter of 12 cm.
The substrate was manufactured using polycarbonate ST-3000 (manufactured by Teijin Chemicals Limited).

Comparative Example 3 In the same manner as in Example 3 described above, a substrate having a two-layer structure in which a CD layer and a DVD layer were bonded to each other was manufactured. However, in Comparative Example 3, the substrates of the CD layer and the DVD layer were each formed in a single-layer structure of polycarbonate ST-3000 (manufactured by Teijin Chemicals Limited). That is, in the optical disk of Comparative Example 3, the CD layer and the DVD layer are made of the same material, and have the same substrate structure as the conventional CD.

<Vibration Analysis Test> A low-reflection film was formed on each of the substrate surfaces of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 manufactured as described above, and the vibration analysis test was performed as follows. Was done.

Each substrate was vibrated by using a vibrator, and the vibration of each substrate was measured by a laser Doppler vibrometer, and the measured vibration was analyzed by a high-speed Fourier analyzer. In addition, as a vibration device, Type by B & K was used.
Using e4810, as a laser Doppler vibrometer,
LV-1100 manufactured by Ono Sokki Co., Ltd. was used. Also,
When measuring the vibration of each substrate, 49 points on the substrate surface were measured, and the measured values were averaged.

FIG. 11 shows the result of the measurement as described above. In FIG. 11, the horizontal axis is the frequency applied to each substrate, and the vertical axis is the gain. Here, the gain is a ratio of an output to an input, and looks at what amplitude was measured when a certain displacement was applied to the substrate at a certain frequency. Specifically, for example, when a displacement of 1 mm is applied, the gain becomes 0 dB when the measured amplitude is 1 mm. When the measured amplitude is 10 mm, which is ten times the input displacement, the gain is 20 dB.
And the gain is -20 dB when the measured amplitude is 0.1 mm, which is -10 times the input displacement.

As is clear from FIG. 11, the substrates of Examples 1 and 2 formed in a three-layer structure by applying the present invention are similar to the conventional substrates formed in a single-layer structure. Compared to the substrates of Example 1 and Comparative Example 2, it can be seen that the resonance frequency is shifted to a higher frequency range and the rigidity is improved.

<Water Absorption Deformation Test> Next, a water absorption deformation test was performed on the substrates of Examples 3 and 4 and Comparative Example 3 as described below.

Each substrate was left in an environment of a temperature of 30 ° C. and a humidity of 90% for 120 hours.
% For 200 hours. At this time, the result of measuring the angle of the warpage deformation at a position 55.3 mm from the center of each substrate is shown in FIG.

As is clear from FIG. 12, the substrates of Examples 3 and 4 formed of a two-layer structure using different materials by applying the present invention were formed in the same structure as the conventional substrate. It can be seen that the deformation due to water absorption was suppressed as compared with the substrate of Comparative Example 3. The substrates of Example 3 and Example 4 had an angle of warpage of ± 0.4 ° or less, and the SA-
It can be said that the CD standard can be sufficiently satisfied.

As described above, the substrate of the optical disk to which the present invention is applied exhibits higher rigidity and sufficiently suppresses water-absorbing deformation as compared with a conventionally used substrate. I understand. As a result, the optical disk to which the present invention is applied performs stable and reliable recording and reproduction by the laser beam incident from the substrate side even when a fine uneven pattern is formed and the recording density is increased. It can be said that it is possible.

When a substrate having a three-layer structure is manufactured by simultaneously injection-molding different resin materials into the same mold as in the first and second embodiments described above, the resin in the mold is required. To prevent the materials from mixing and becoming opaque,
It is important to select each resin material. As a combination that does not become opaque even when different resin materials are simultaneously injection-molded, in addition to the above, for example, Acrypet VH (manufactured by Mitsubishi Rayon Co., Ltd.), which is an acrylic resin, is used for the skin layer, and the impact resistance is applied to the core layer. Acrypet IR50 acrylic resin (Mitsubishi Rayon Co., Ltd.)
May be used. Thus, it can be said that it is desirable to select the same type of polymer but different skeletons for the resin material forming the skin layer and the core layer.

However, the present invention is not limited to the materials used for the skin layer and the core layer, but is made of a material having a property of transmitting incident light when the respective layers are formed by lamination. The skin layer and the core layer may be formed by a combination of the above.

[0115]

The optical recording medium according to the present invention can have excellent physical and / or mechanical properties as a whole by appropriately selecting a resin material for forming each resin layer, Incident light can be incident from the substrate side. Therefore, the optical recording medium can form a fine uneven pattern with high accuracy and high density in response to the increase in recording density, and can perform stable and reliable recording and reproduction.

Further, in the method for manufacturing an optical recording medium according to the present invention, the first resin layer and the second resin layer are laminated in two or more layers to form a substrate. Second
Is formed of a different material having a property of transmitting incident light. Thereby, a resin material for forming each resin layer can be appropriately selected, and an optical recording medium having excellent physical and / or mechanical properties as a whole can be manufactured. Therefore, it is possible to manufacture an optical recording medium in which a fine concavo-convex pattern is formed with high precision and high density in response to an increase in recording density, and in which stable and reliable recording and reproduction can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an optical disc according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of the optical disc.

FIG. 3 is an enlarged sectional view of a main part showing another optical disc according to the present invention.

FIG. 4 is a schematic view showing an injection molding apparatus used when manufacturing an optical disc according to the present invention.

FIG. 5 is an enlarged sectional view of a main part of the injection molding apparatus.

FIG. 6 is an enlarged sectional view of a main part showing a mold part of the injection molding apparatus.

FIG. 7 is a sectional view showing another mold part of the injection molding apparatus.

FIG. 8 is a cross-sectional view showing the same mold portion and showing how a first resin layer of a substrate is formed.

FIG. 9 is a cross-sectional view showing the same mold portion and showing a state where a second movable mold has moved.

FIG. 10 is a cross-sectional view showing the same mold portion and showing how a second resin layer of the substrate is formed.

FIG. 11 is a diagram showing frequency responses of the optical disk according to the present invention and a conventional optical disk.

FIG. 12 is a diagram showing water absorption deformation of an optical disk according to the present invention and a conventional optical disk.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk, 2 substrates, 3 signal recording layers, 4 light reflection layers, 5 protective films, 6 skin layers, 7 core layers, 10 optical lenses, 11 laser beams

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuji Akiyama 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Toshiyuki Kashiwagi 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 5D029 KA01 KB06 KB08 KC09 KC13 KC20 5D121 AA02 DD05 DD18

Claims (12)

[Claims] An optical recording medium in which at least a signal recording layer is formed on a substrate, and recording and / or reproduction of a recording signal is performed on the signal recording layer by incident light incident from the substrate side. The substrate has a structure in which a first resin layer and a second resin layer are laminated in two or more layers, and the first resin layer and the second resin layer are respectively provided with respect to the incident light. An optical recording medium characterized in that the optical recording medium is formed of different materials having different physical properties and / or mechanical properties while having a light-transmitting property. 2. The light according to claim 1, wherein said substrate has a three-layer structure in which said first resin layer is laminated on both main surfaces of said second resin layer. recoding media. 3. The optical recording medium according to claim 1, wherein the first resin layer has a lower water absorption than the second resin layer. 4. The optical recording medium according to claim 1, wherein the second resin layer has a higher glass transition temperature than the first resin layer. 5. The optical recording medium according to claim 1, wherein the second resin layer has a higher mechanical internal loss than the first resin layer. 6. At least a signal recording layer is formed on a substrate, and recording and / or reproduction of a recording signal is performed on the signal recording layer by incident light incident from the substrate side. When injection molding the substrate of the optical recording medium formed by the first resin layer and the second resin layer having a property of transmitting the incident light, the first resin is formed by a two-color molding process. The second layer is made of a dissimilar material having different physical and / or mechanical properties.
A method for producing an optical recording medium, comprising forming a resin layer of 7. In the two-color molding step, the first
7. The method for manufacturing an optical recording medium according to claim 6, wherein the second resin layer is formed on the first resin layer after forming the resin layer. 8. In the two-color molding step, the second color molding step
7. The method for manufacturing an optical recording medium according to claim 6, wherein the first resin layer is formed by laminating the first resin layer on both main surfaces of the resin layer. 9. The light according to claim 6, wherein the first resin layer is formed of a resin material having a higher fluidity than a resin material forming the second resin layer. Manufacturing method of recording medium. 10. The method according to claim 6, wherein the two-color molding step is performed in the same mold. 11. In the two-color molding step, the speed of injecting the resin material forming the first resin layer into the mold is controlled by controlling the speed of the resin material forming the second resin layer into the mold. The injection speed is higher than the injection speed, and the resin material forming the first resin layer and the resin material forming the second resin layer are simultaneously injected and filled in the same mold. A method for manufacturing an optical recording medium according to claim 10. 12. In the two-color molding step, after injecting and filling a resin material for forming the first resin layer into a mold, and when at least a part of the resin material is in a molten state, 11. The method for manufacturing an optical recording medium according to claim 10, wherein a resin material for forming the second resin layer is injected and filled into the mold.