JP2000298879A - Optical recording medium - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To bond a substrate and a light transmitting member with high accuracy and to keep uniform the distance between the substrate and the light transmitting member. SOLUTION: At least a recording layer is formed on a substrate, and a light transmitting member is bonded on the recording layer,
The substrate has a step portion that is more convex than the recording layer, and a light transmitting member is bonded on the step portion.

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 capable of increasing the recording density by reducing the thickness of a reproducing light transmitting portion.

[0002]

2. Description of the Related Art In recent years, in the field of information recording, researches on optical information recording systems have been advanced in various places. This optical information recording system is capable of recording / reproducing in a non-contact manner, achieving a recording density that is at least an order of magnitude higher than that of a magnetic recording system, and is applicable to read-only, write-once, and rewritable memory types. It has a number of advantages such as compatibility, and is considered as a system that can realize an inexpensive large-capacity file for a wide range of uses from industrial use to consumer use.

In particular, digital audio discs and optical video discs, which are optical discs compatible with a read-only type memory, are widely used.

In an optical disk such as the above digital audio disk, a reflective film made of a metal thin film such as an aluminum film is formed on a transparent substrate on which an uneven pattern such as pits or grooves indicating information signals is formed. A protective film for protecting from moisture and O ₂ in the atmosphere is formed on the reflective film. When reproducing the information of such an optical disc, the concave / convex pattern is irradiated with reproduction light such as laser light from the substrate side of the optical disc,
Information is detected based on the difference between the reflectances of the incident light and the return light.

When manufacturing such an optical disk, first, a substrate having the above-mentioned concave and convex pattern is formed by a method such as injection molding, and a reflective film made of the above-mentioned metal thin film is formed thereon by a method such as vapor deposition. Then, an ultraviolet curable resin or the like is applied thereon to form the protective film.

[0006]

By the way, recently, a higher recording density has been demanded, and in order to cope with this, a numerical aperture (hereinafter referred to as NA and NA) of an objective lens for irradiating a reproduction light of an optical pickup. It is proposed that the spot diameter of the reproduction light be reduced by increasing the diameter of the reproduction light. For example, while the NA of an objective lens of a digital audio disc that has been used so far is 0.45, an optical video that has recently attracted attention because it has a recording capacity of 6 to 8 times that of a digital audio disc. Disc (for example, Digital Versatile Disc, hereinafter, DVD
Called. )), The NA of the objective lens is set to 0.60.
About.

When the NA of the objective lens is increased as described above, it is necessary to further reduce the thickness of the substrate of the optical disk. This is because the tolerance of the angle (tilt angle) at which the disk surface deviates from the perpendicular to the optical axis of the optical pickup becomes small, and this tilt angle is easily affected by aberration and birefringence due to the thickness of the substrate. That's why. Therefore, the thickness of the substrate is reduced to minimize the tilt angle. For example, in the above-mentioned digital audio disk, the thickness of the substrate is about 1.2 mm, whereas the optical video disk which has a recording capacity 6 to 8 times that of a digital audio disk such as a DVD, for example. In, the thickness of the substrate is 0.6
mm.

However, it is expected that a higher recording density will be required in the future, and a further reduction in the thickness of the substrate will be required. Therefore, for example, a recording layer is formed by forming irregularities on one main surface of the substrate, a reflective film is provided thereon, and a light transmitting layer, which is a thin film that transmits light, is provided thereon. An optical recording medium has been proposed in which information on a recording layer is reproduced by irradiating reproduction light. With this configuration, it is possible to cope with an increase in the NA of the objective lens by reducing the thickness of the light transmission layer.

However, when the light transmitting layer is made thinner in this way, it becomes difficult to form the light transmitting layer by injection molding using a thermoplastic resin, which is a common technique in the production of optical discs.

For example, as shown in FIG. 17, a transparent substrate 10 made of polycarbonate or the like and having a thickness of about 0.6 to 1.2 mm is used as an optical disk 100 compatible with a high NA.
1, a light-transmitting layer 103 is formed on the substrate 101 on which the recording layer 102 is formed to a thickness of 0.1 m.
A structure formed as thin as m has been proposed.

In this case, the NA of the objective lens can be increased to 0.78 or more. However, since the thickness unevenness of the light transmitting layer 103 due to the increase in NA is inversely proportional to the fourth power of NA, for example, when the thickness of the light transmitting layer 103 is 100 μm, the thickness unevenness is ± 5.26λ / (NA) Must be in the range of ⁴ . Therefore, when the reproduction light applied to the optical disc 100 is a laser beam having a wavelength of 400 nm, that is, a so-called blue laser beam 104 in accordance with the increase in the recording density, the thickness unevenness described above is kept within ± 4 μm. There must be.

As described above, it is almost impossible and very difficult to manufacture the light transmitting layer 103 which is thin and has a small thickness unevenness by using the conventional injection molding method.

Therefore, as a method for solving this problem,
For example, as shown in FIG. 18, an adhesive 10 made of an ultraviolet curable resin or the like is provided on a substrate 106 on which a recording layer 105 is formed.
7 and a thickness of about 0.1 mm made of a thermoplastic resin.
(Sheet method) has been proposed.

This is because a sheet 108 whose thickness is controlled with high precision, for example, a thickness of about 95 to 100 μm, is bonded to the substrate 106 via an adhesive layer formed as thin as possible, so that uniformity with less thickness unevenness is obtained. It is intended to obtain a light transmitting layer having a large thickness, and for a central value of 103 μm,
The thickness unevenness can be kept within ± 3 μm.

However, in the optical disk manufactured in this manner, the thickness of the adhesive layer is extremely thin. Therefore, dust having a size similar to or greater than the thickness of the adhesive layer is removed from the substrate 106 and the sheet. 108, and as a result, the light transmission layer may have uneven thickness.

For example, dust having a size of 10 μm or more is
In the rotational stretching step in which the sheet 108 is attached to the substrate 106, the sheet 108 is blown outward from above the substrate 106. However, since the size of the dust is smaller than 2 μm at the innermost peripheral portion of the substrate 106, the probability that the dust is sandwiched between the substrate 106 and the sheet 108 increases.

As a method for solving this problem, a method of manufacturing in a clean environment (clean room) in which dust of 1 μm or more is completely removed can be considered. However, a large amount of capital investment is required to make the clean room. Further, in this optical disc, some of the foreign substances generated when the recording layer is formed are not blown off from above the substrate 106 in the above-described rotational stretching step.

Therefore, such an optical disk includes:
When the sheet 108 is attached to the substrate 106, there is a problem in that dust is sandwiched between the substrate 106 and the sheet 108, resulting in uneven thickness of the light transmitting layer.

Further, as for an optical recording medium, an optical disk having a structure having a plurality of recording layers has been proposed from the viewpoint of increasing the capacity.

For example, as shown in FIG. 19, as a practical example, a two-plate structure in which two substrates having a recording layer formed thereon are bonded to each other via an adhesive layer like the above-mentioned DVD. An optical disk 200 can be used. This optical disc 200 is composed of a pair of transparent substrates 201a and 201b made of polycarbonate or the like and having a thickness of about 0.6 mm.
Are bonded via an adhesive layer 203 made of an ultraviolet curable resin such that the recording layers 202a and 202b formed on the pair of substrates 201a and 201b are inside. In the optical disc 200, the recording layers 202a and 202b are irradiated with a laser beam 204 from the same direction to record and reproduce information signals.

Incidentally, in such an optical disc, setting of the reflectance of each recording layer and its variation, or setting of the interval between each recording layer and its variation, etc. are mentioned as problems.

For example, in the optical disc 200, the recording layer 20 formed on the pair of substrates 201a and 201b, respectively.
The distance between 2a and 202b, that is, the thickness of the adhesive layer 203 is set to, for example, about 40 to 70 μm. Further, the variation is 20 (μ) in the plane of the one substrate.
m) pp (peak-to-peak), and within one round, it is standardized to be within about 8 (μm) pp.

As one method of manufacturing the optical disc 200, as shown in FIG.
The recording layers 202a and 202b of the pair of substrates 201a and 201b are supplied with an adhesive 205 made of, for example, an ultraviolet curable resin.
Have been proposed.

However, according to this method, the thickness of the adhesive layer made of the ultraviolet curable resin must be controlled by the viscosity, the number of rotations, the time, and the like of the ultraviolet curable resin at the time of bonding the pair of substrates 201a and 201b. No. For this reason, the adhesive layer may have uneven thickness due to, for example, a variation in the viscosity of the ultraviolet curable resin due to a change in the temperature of the atmosphere, a difference in the wettability of the substrate surface, an uneven number of rotations, and time control.

Therefore, such an optical disk 200
Is caused by uneven thickness of the adhesive layer 203,
A pair of substrates 20 on which the recording layers 202a and 202b are formed
When laminating the recording layers 1a and 201b with the adhesive layer 203 interposed therebetween, there is a problem that the distance between the recording layers 202a and 202b cannot be accurately maintained.

As described above, when the above-described conventional optical recording medium is bonded to the substrate with the light-transmitting member such as the above-described light-transmitting sheet or substrate via the adhesive layer,
When the dust or the like is sandwiched between the substrate and the light transmitting material, the light transmitting member becomes uneven in thickness, and the adhesive layer becomes uneven in thickness, so that the distance between the substrate and the light transmitting member is kept uniform. There was a problem that it was not possible.

In view of the above, the present invention has been proposed in view of such a conventional situation. The present invention has been proposed in which a substrate and a light transmitting member are bonded with high accuracy, and the distance between the substrate and the light transmitting member is kept uniform. It is an object of the present invention to provide an optical recording medium capable of being used.

[0028]

An optical recording medium according to the present invention that achieves the above object has at least a recording layer formed on a substrate and a light transmitting member attached to the recording layer. It has a stepped portion that is more convex than the recording layer, and a light transmitting member is bonded on the stepped portion.

In the optical recording medium according to the present invention configured as described above, the substrate has a stepped portion that is more convex than the recording layer, and the light transmitting member is bonded on the stepped portion. A predetermined gap is formed between the substrate and the light transmitting member. Therefore, even when dust or the like is interposed between the substrate and the light transmitting material, the light transmitting member does not have uneven thickness. Further, in this optical recording medium, since the light transmitting member is attached with the step portion of the substrate as a reference surface, the distance between the substrate and the light transmitting member is kept uniform.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First Embodiment First, an optical recording medium schematically shown in FIG. 1 will be described as a first embodiment of the present invention.

This optical recording medium is an optical disk 1 on which a light-transmitting sheet is bonded as a light-transmitting member. In the optical disc 1, for example, a pit pattern indicating an information signal is formed in a track direction on a transparent substrate 3 formed in a disc shape having a center hole 2 at a center portion, and the pit pattern is formed on the substrate 3. Then, a recording layer 4 is formed by forming a reflection film, and a light-transmitting sheet 6 is bonded to the substrate 3 on which the recording layer 4 has been formed via an adhesive layer 5. 7 is formed.

In the optical disc 1, information signals are reproduced by irradiating the recording layer 4 with reproduction light from the light transmission layer 7 side.

In the optical disc 1, the recording layer 4
May be used as a recording film such as a phase change recording film, an organic dye film, and a magneto-optical recording film, so that an optical disk capable of reproducing, additionally writing, and rewriting may be used.

The optical disc 1 has a signal recording area 8 having a recording layer 4 formed on the main surface thereof, and a non-signal recording area having no recording layer 4 formed on the inner side of the signal recording area 8. 9 and a chucking area 10 centered on the center hole 2 on the inner peripheral side of the non-signal recording area 9. Correspondingly, the first step portion 1 in which the non-signal recording area 9 is more convex than the signal recording area 8 is provided on the substrate 3.
1 and a second step portion 12 in which the chucking area 10 is more convex than the non-signal recording area 9. Therefore, in the substrate 3, the non-signal recording area 9 is formed thicker than the signal recording area 8, and the chucking area 10 is formed thicker than the non-signal recording area 9.

In the optical disc 1, the sheet 6 serving as the light transmitting layer 7 is bonded to the first step portion 1 via the adhesive layer 5.
1, that is, on the surface on which the non-signal recording area 9 is formed. The adhesive layer 5 is formed between the signal recording area 8 of the substrate 3 and the sheet 6.

Here, a specific manufacturing method of such an optical disc 1 will be described.

First, the substrate 3 constituting the optical disk 1 is manufactured by injection molding.

As shown in FIG. 2, the substrate 3 has, for example, a diameter A of 120 mm and a diameter B of the center hole 2 of 15 m.
m, the diameter C of the non-signal recording area 9 is 40 mm, and the diameter D of the chucking area 10 is 33 mm. Further, as shown in FIG. 3, the substrate 3 has, for example, a thickness E of the chucking region 10 of 1.2 mm and a step F of the first step portion 11.
Is 10 μm, and the step G of the second step portion 12 is 90 μm.

When this substrate 3 is injection molded,
The injection molding apparatus 20 shown in FIG. The injection molding apparatus 20 includes a fixed mold 21 that forms one main surface side of the substrate 3, and a substrate that is disposed so as to face the fixed mold 21 and that can freely move toward and away from the fixed mold 21. 3 includes a movable mold 22 that forms the other main surface side, and an outer mold 23 that is incorporated in the fixed mold 21 and forms the outer peripheral surface of the substrate 3. As shown in FIG. 5, the fixed mold 21, the movable mold 22, and the outer peripheral mold 23 form a cavity 24 having a shape corresponding to the substrate 3 formed in a mold clamped state.

The fixed mold 21 is provided with a supply path 25 for injecting and filling the cavity 24 with a substrate material such as molten polycarbonate. In addition, the fixed mold 21 includes:
A stamper 27 positioned by a stamper centering jig 26 is provided on the main surface on the cavity 24 side. On the stamper 27, a concavo-convex pattern 27a corresponding to a pit indicating an information signal is formed. The movable mold 12 is provided with a projection member (not shown) for pushing the molded substrate 3 out of the cavity 24.

In this injection molding apparatus 20, at the joint 28 between the stamper centering jig 26 and the stamper 27, the stamper 27 corresponds to the first stepped portion 11 formed on the substrate 3, The projection 26 is provided on the cavity 24 side with respect to 26. A recess 29 is formed in the centering tool 26 corresponding to the second step 12 formed in the substrate 3. Thereby, in the injection molding apparatus 20, in the mold clamped state, the signal recording area 8,
A cavity 24 for forming the non-signal recording area 9 and the chucking area 10 to a desired thickness is formed.

In the injection molding apparatus configured as described above, the molten substrate material is injected and filled into the cavity 24. Then, the substrate material filled in the cavity 24 is cooled and solidified, and the substrate 3 having the above-described desired shape is formed.
Is produced. The pit pattern is formed on one main surface of the substrate 3 by transferring the concave / convex pattern 27a formed on the stamper 27 to the substrate 3.

Next, a recording layer 4 is formed on the signal recording area 8 of the substrate 3 by forming a reflection film made of aluminum or the like on the pit pattern formed on one main surface of the substrate 3 by sputtering or the like. Form.

Next, as shown in FIG.
A sheet 6 having an inner diameter of 119 mm, an inner diameter I of 33 mm, and a thickness J of 90 μm is prepared. This sheet 6 has a recording layer 4
It is manufactured by injection molding a thermosetting resin such as polycarbonate, for example, into a sheet and punching it into the desired shape described above.

Next, the first step portion 1 formed on the substrate 3
For example, 200 cps as an adhesive so as to fill 1
An ultraviolet curable resin having a viscosity of 3 is dropped on the signal recording area 8 of the substrate 3 in a ring shape. Then, the sheet 6 is placed on the non-signal recording area 9 of the substrate 3, for example, at a rotation speed of 500.
By rotating the sheet at 0 rpm for 30 seconds, the signal is uniformly spread between the signal recording area 8 of the substrate 3 and the sheet 6. By irradiating ultraviolet rays from above the sheet 6 to cure the ultraviolet curing resin, the first step portion 11 of the substrate 3
That is, the sheet 6 is provided on the surface of the non-signal recording area 9 with the adhesive layer 5.
Are pasted together. Thereby, the optical disc 1 in which the light transmitting layer 7 is formed on the substrate 3 on which the recording layer 4 is formed
Is produced.

In the optical disk 1 manufactured as described above, the sum of the thicknesses of the adhesive layer 5 and the sheet 6, that is, the thickness of the light transmitting layer 7 is about 102 mm, and the thickness unevenness of the light transmitting layer 7 is about ± 2 μm. Can be suppressed. The thickness of the adhesive layer 5 formed between the sheet 6 and the signal recording area 8 of the substrate 3 is about 10 to 14 μm.

Therefore, in this optical disc 1, the substrate 3
Even when dust or the like having a size of, for example, 10 μm or less is interposed between the sheet 6 and the sheet 6, the sheet 6 bonded to the substrate 3 via the adhesive layer 5 has uneven thickness, that is, the light transmitting layer 7 has a thickness. Unevenness can be prevented.

In the optical disc 1, the sheet 6 is bonded with the non-signal recording area 9 on the first step portion 11 of the substrate 3 as a reference plane. Therefore, the distance between the substrate 3 and the sheet 6 can be kept uniform via the adhesive layer 5 formed between the signal recording area 8 of the substrate 3 and the sheet 6.

Therefore, in the optical disc 1, the substrate 3 and the sheet 6 can be bonded together with high precision, the distance between the substrate and the sheet can be kept uniform, and high-quality optical recording with improved yield can be achieved. It can be a medium.

The sum of the thickness of the sheet 6 and the thickness of the adhesive layer 5,
That is, the thickness of the light transmitting layer 7 is preferably 177 μm or less. The sheet 6 is preferably formed thinner than the substrate 3. Also, in the substrate 3,
The step of the first step portion 11 is preferably 10 μm to 100 μm.

Second Embodiment Next, an optical recording medium schematically shown in FIG. 7 will be described as a second embodiment of the present invention.

This optical recording medium is an optical disc 30 having a two-layer structure on which a light-transmitting sheet on which a recording layer is formed as a light transmitting member is bonded. This optical disk 3
0 indicates that, for example, a pit pattern indicating an information signal is formed in a track direction on a transparent substrate 32 formed in a disk shape having a center hole 31 at a center portion, and on a substrate 32 on which this pit pattern is formed, A first recording layer 33 is formed by forming a reflection film, and a light-transmitting sheet 35 is bonded to the substrate 32 on which the first recording layer 33 is formed via an adhesive layer 34. Thus, the light transmitting layer 36 is formed. On the sheet 35, a pit pattern indicating an information signal, for example, is formed in the track direction on the main surface on the side of the adhesive layer 34, and a second recording layer 37 on which a translucent reflective film is formed. Are formed.

In the optical disc 30, an information signal is reproduced by irradiating the first recording layer 33 or the second recording layer 37 with reproducing light from the light transmitting layer 36 side.

In the optical disc 30, the first recording layer 33 and / or the second recording layer 37 may be a recording film such as a phase change recording film, an organic dye film, a magneto-optical recording film, etc. An optical disk that can be additionally written and rewritten may be used.

The optical disk 30 has a first recording layer 33 and a second recording layer 33 on its main surface, like the optical disk 1 described above.
And a non-signal recording area 39 in which the first recording layer 33 and the second recording layer 37 are not formed on the inner peripheral side of the signal recording area 38. And a chucking area 40 centered on the center hole 31 on the inner peripheral side of the non-signal recording area 39. Correspondingly, the substrate 32 has a first step portion 41 in which the non-signal recording area 39 is more convex than the signal recording area 38 and a chucking area 40 in which the non-signal recording area 39 is formed.
A second step portion 42 that is more convex than that is formed. Therefore, in the substrate 32, the non-signal recording area 39 is formed thicker than the signal recording area 38, and the chucking area 40 is formed thicker than the non-signal recording area 39.

In the optical disc 30, the above-mentioned sheet 35 serving as the light transmitting layer 36 is bonded via the adhesive layer 34 on the first step portion 41, that is, on the surface on which the non-signal recording area 39 is formed. . The adhesive layer 34 is formed between the signal recording area 38 of the substrate 32 and the sheet 35.

Here, a specific manufacturing method of such an optical disk 30 will be described.

First, the substrate 32 constituting the optical disk 30
Is manufactured by injection molding.

As shown in FIG. 8, the substrate 32 has, for example, a diameter K of 120 mm and a diameter L of the center hole 31 of 15 m.
m, the diameter M of the non-signal recording area 39 is 40 mm, and the diameter N of the chucking area 10 is 33 mm. Also,
As shown in FIG. 9, for example, the substrate 32 has a thickness O of the chucking region 40 of 1.2 mm, a step P of the first step portion 41 of 30 μm, and a step Q of the second step portion 42 of 70 μm.
It has been.

Since the substrate 32 is manufactured in the same manner as the substrate 3 constituting the optical disk 1 except that the dimensions are different, the description will be omitted below.

Next, a reflection film made of aluminum or the like is formed on the pit pattern formed on one main surface of the substrate 32 by sputtering or the like, so that the first recording is performed on the signal recording area 38 of the substrate 32. The layer 33 is formed.

Next, as shown in FIG. 10, for example, the outer diameter H is 119 mm, the inner diameter I is 33 mm, and the thickness J is 70 μm.
The prepared sheet 35 is prepared. The sheet 35 has a light transmittance sufficient to transmit the laser light applied to the first recording layer 33 and the second recording layer 37, and is made of, for example, a thermosetting resin such as polycarbonate. A pit pattern transferred from the master disk is formed on the sheet 35 by a 2p method or a high-temperature heating method, and the sheet 35 is manufactured by punching into the above-described desired shape.

Next, a second recording layer 37 is formed by forming a translucent reflective film such as a dielectric film on the pit pattern formed on one main surface of the sheet 35.

Next, an adhesive such as 300 cp is used to fill the first step 38 formed on the substrate 32.
An ultraviolet curable resin having a viscosity of s is dropped on the signal recording area 38 of the substrate 32 in a ring shape. And this substrate 32
The sheet 35 on the non-signal recording area 39 of the first recording layer 3
3 and the second recording layer 37 are placed so as to face each other, and are rotated, for example, at a rotation speed of 5000 rpm for 30 seconds to spread the ultraviolet curable resin evenly between the signal recording area 38 of the substrate 32 and the sheet 35. Let Then, by irradiating ultraviolet rays from above the sheet 35 to cure the ultraviolet curing resin, the sheet 35 forms the adhesive layer 34 on the first step portion 41 of the substrate 32, that is, on the surface of the non-signal recording area 39. Pasted together. Thus, the optical disc 30 having a two-layer structure in which the first recording layer 33 and the second recording layer 37 are formed is manufactured.

In the optical disk 30 manufactured as described above, the sum of the thicknesses of the adhesive layer 34 and the sheet 35, that is, the thickness of the light transmitting layer 36 is about 102 mm, and the thickness unevenness of the light transmitting layer 36 is about ± 2 μm. Can be suppressed. The thickness of the adhesive layer 34 formed between the sheet 35 and the signal recording area 38 of the substrate 32 is about 30 to 34 μm.

For this reason, in the optical disc 30, even when dust or the like having a size of, for example, 10 μm or less is sandwiched between the substrate 32 and the sheet 35, the optical disk 30 is bonded to the substrate 32 via the adhesive layer 34. It is possible to prevent the sheet 35 from being uneven in thickness, that is, the light transmitting layer 36 from being uneven in thickness.

In this optical disk 30, the substrate 32
The sheet 35 is bonded with the non-signal recording area 39 on the first step portion 41 as a reference plane. Therefore, the distance between the substrate 32 and the sheet 35 can be kept uniform via the adhesive layer 34 formed between the signal recording area 38 of the substrate 32 and the sheet 35.

Therefore, in the optical disc 30, the substrate 32 and the sheet 35 can be bonded together with high accuracy, the distance between the substrate 32 and the sheet 35 can be kept uniform, and the high yield with improved yield can be achieved. It can be an optical recording medium.

The sum of the thickness of the sheet 35 and the adhesive layer 34, that is, the thickness of the light transmitting layer 36 is preferably 177 μm or less. Further, the sheet 35 is preferably formed to be thinner than the substrate 32. Also, the substrate 3
2, the step of the first step 41 is 10 μm to 1 μm.
It is preferably 00 μm.

In the optical recording medium to which the present invention is applied, the optical recording medium to which a light-transmitting sheet is bonded as a light-transmitting member is not limited to the above-described optical disk 1 and optical disk 30.

For example, as shown in FIGS. 11A to 11D, a recording layer 51 is formed on both main surfaces of a substrate 50, or a sheet 53 on which a recording layer 52 is formed is placed via an adhesive layer 54. An optical disc having a multilayer structure may be obtained by superposing a plurality of optical discs. Further, by making the thickness of the signal recording area of the substrate 50 thinner than the non-signal recording area,
An optical disk that is compatible with the development may be used.

Third Embodiment Next, an optical recording medium schematically shown in FIG. 12 will be described as a third embodiment of the present invention.

This optical recording medium is an optical disk 50 on which a light-transmitting substrate is bonded as a light-transmitting member.
It is. This optical disc 60 has a center hole 60a at the center.
A transparent first substrate 61 and a second substrate 62 having
The first recording layer 63 and the second recording layer 64 formed on the first substrate 61 and the second substrate 62 are bonded via an adhesive layer 65 so as to be inside.
The first recording layer 63 is formed by, for example, forming a pit pattern indicating an information signal in the track direction on the first substrate 61, and forming a reflective film thereon. The second recording layer 64 is formed by, for example, forming a pit pattern indicating an information signal in the track direction on the second substrate 62, and forming a translucent reflective film thereon.

In this optical disk 60, the second substrate 62
The information signal is reproduced by irradiating the first recording layer 63 or the second recording layer 64 with reproduction light from the side.

In the optical disk 60, the first recording layer 63 and / or the second recording layer are formed of a recording film such as a phase change recording film, an organic dye film, a magneto-optical recording film, etc.
An optical disk that can be played back and additionally written / rewritable may be used.

The optical disk 60 has a first surface on its main surface.
The signal recording area 66 in which the recording layer 63 and the second recording layer 64 are formed, and the first recording layer 63 and the second recording layer 64 are formed on the inner peripheral side of the signal recording area 38. And a non-signal recording area 67 centered on the center hole 60a. Correspondingly, the first substrate 61 includes
A step 68 is formed in which the non-signal recording area 67 is more convex than the signal recording area 66. Therefore, in the first substrate 61, the non-signal recording area 67 is formed thicker than the signal recording area 66. Then, the adhesive layer 65
Between the signal recording area 66 of the first substrate 61 and the second substrate 62.

Here, a specific manufacturing method of such an optical disk 60 will be described.

First, the first substrate 61 constituting the optical disk 60 is manufactured by injection molding.

As shown in FIG. 13, for example, the first substrate 61 has a diameter U of 120 mm, a diameter V of the center hole 60a of 15 mm, and a diameter W of the non-signal recording area 67 of 34 mm.
It has been. As shown in FIG. 14, the first substrate 61 has a thickness X of the non-signal recording area 67 of 0.6, for example.
mm, and the step Y of the step 68 is 50 μm.

Since the first substrate 61 is manufactured in the same manner as the substrate 3 constituting the optical disk 1 except that the dimensions are different, the description will be omitted below.

Next, for example, a second substrate 62 having an outer diameter of 120 mm, an inner diameter of 34 mm, and a thickness of 0.6 mm is prepared. The second substrate 62 is manufactured by injection molding in the same manner as the first substrate 61 described above, and is formed of a dielectric film or the like on a pit pattern formed on one main surface of the second substrate 62. The second recording layer 64 is formed in the signal recording area 66 of the second substrate 62 by forming the reflection film by sputtering or the like.

Next, as shown in FIG. 15, the first substrate 6
An ultraviolet curable resin 69 having a viscosity of, for example, 500 cps is applied as an adhesive on the step portion 68 formed in the first step.
Is dropped on the signal recording area 66 of the substrate 61. Then, the first substrate 61 and the second substrate 62 are placed with the first recording layer 63 and the second recording layer 64 facing each other so that the center holes 60a thereof coincide with each other. Rotation speed 5000r
pm for 30 seconds to remove the UV curable resin 69
Between the signal recording area 67 of the first substrate 61 and the second substrate 62. Then, ultraviolet rays are irradiated from above the second substrate 62 to cure the ultraviolet curing resin 69, so that the second portion 62 on the step portion 68 of the first substrate 61, that is, on the surface of the non-signal recording area 66. Are bonded together with an adhesive layer 65 interposed therebetween. Thus, an optical disc 60 having a two-layer structure in which the first recording layer 63 and the second recording layer 64 are formed is manufactured.

In the optical disk 60 manufactured as described above, since the step Y of the step 68 is 50 μm, the thickness of the intermediate layer, that is, the thickness of the adhesive layer 34 is 50 μm.
m or less. Therefore, this optical disk 60
In this case, the first substrate 61 and the second substrate 62 can be bonded together with high accuracy, and the distance between the first substrate 61 and the second substrate 62 can be kept uniform. An improved high quality optical recording medium can be obtained.

In the optical recording medium to which the present invention is applied, the optical recording medium to which the light-transmitting substrate is bonded as the light-transmitting member is not limited to the structure of the optical disk 60 described above.

For example, as shown in FIGS. 16A and 16B, on the first substrate 70, a non-signal recording area is located on the inner peripheral side of the signal recording area 72 where the first recording layer 71 is formed. 73, a first stepped portion 75 having a chucking area 74 on the inner peripheral side of the non-signal recording area 73, the non-signal recording area 73 being more convex than the signal recording area 72, and a chucking area. A structure may be employed in which a second step portion 76 in which 74 is more protruded than the non-signal recording area 73 is formed. In this case, the second substrate 77 is provided with the first step portion 75.
The second substrate 7 is placed on the top, that is, on the surface of the non-signal recording area 73.
7 are bonded together with an adhesive layer 78 interposed therebetween. In addition, the first recording layer 71 formed on the first substrate 70 and the second recording layer 79 formed on the second substrate 77 are formed on at least one principal surface side of at least one substrate. The configuration is not particularly limited.

The optical recording medium to which the present invention is applied may have a structure in which a step for mounting a light transmitting member is formed on the outer peripheral side of the substrate.

Further, the optical recording medium to which the present invention is applied may have a structure in which a spacer such as a bead is provided between the light transmitting member and the stepped portion of the substrate on which the light transmitting member is mounted. In this case, fine beads are dispersed in the ultraviolet curable resin and are formed between the step portion of the substrate and the light transmitting member as an adhesive layer, whereby the beads support the light transmitting member in the step portion. . Thereby, further smoothing of the light transmitting member can be realized.

[0089]

As described in detail above, according to the optical recording medium of the present invention, the substrate has a step portion that is more convex than the recording layer, and the light transmitting member is adhered on the step portion. Since they are aligned, a predetermined gap is formed between the substrate and the light transmitting member. Therefore, even when dust or the like is interposed between the substrate and the light transmitting material,
It is possible to prevent the light transmitting member from having uneven thickness. Further, in this optical recording medium, since the light transmitting member is bonded with the step portion of the substrate as a reference surface, the distance between the substrate and the light transmitting member can be kept uniform. Therefore, the substrate and the light transmitting member can be bonded with high precision, and a high quality optical recording medium with improved yield can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an optical disc shown as a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a substrate constituting the optical disc.

FIG. 3 is a sectional view of a main part for explaining a substrate constituting the optical disc.

FIG. 4 is a schematic cross-sectional view for explaining a configuration of an injection molding apparatus used for producing a substrate constituting the optical disc.

FIG. 5 is a view showing a state in which a cavity for molding a substrate is formed by clamping.

FIG. 6 is a cross-sectional view illustrating a sheet constituting the optical disc.

FIG. 7 is a cross-sectional view for explaining a configuration of an optical disc shown as a second embodiment of the present invention.

FIG. 8 is a cross-sectional view for explaining a substrate constituting the optical disc.

FIG. 9 is a cross-sectional view of a main part for describing a substrate constituting the optical disc.

FIG. 10 is a cross-sectional view for explaining sheets constituting the optical disc.

FIG. 11 is a schematic sectional view showing another configuration of the optical recording medium to which the present invention is applied.

FIG. 12 is a cross-sectional view for explaining a configuration of an optical disc shown as a third embodiment of the present invention.

FIG. 13 is a cross-sectional view for explaining a substrate constituting the optical disc.

FIG. 14 is a cross-sectional view of a principal part for describing a substrate constituting the optical disc.

FIG. 15 is a schematic sectional view showing a manufacturing process of the optical disc.

FIG. 16 is a schematic sectional view showing another configuration of the optical recording medium to which the present invention is applied.

FIG. 17 is a schematic cross-sectional view showing a conventional optical disc for reproducing information from a recording layer by irradiating reproduction light from a light transmitting layer side.

FIG. 18 is a diagram showing a manufacturing process of the optical disc.

FIG. 19 is a schematic sectional view showing a conventional optical disk having a plurality of recording layers.

FIG. 20 is a diagram showing a manufacturing process of the optical disc.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 optical disc, 3 first substrate, 4 recording layer, 5 adhesive layer, 6 sheet, 7 light transmission layer, 8 signal recording area, 9
Non-signal recording area, 10 chucking area, 11 first step, 12 second step, 30 optical disc,
32 first substrate, 33 first recording layer, 34 adhesive layer, 35 sheet, 36 light transmitting layer, 37 second recording layer, 38 signal recording area, 39 non-signal recording area, 40
Chucking area, 41 first step, 42 second
Step portion, 60 optical disk, 61 first substrate, 62
2nd substrate, 63 1st recording layer, 64 2nd recording layer, 65 adhesive layer, 66 signal recording area, 67 non-signal recording area, 68 step

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsuyoshi Yamazaki 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Tomomi Yukimoto 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo No. Sony Corporation F term (reference) 5D029 KB12 LA02 LB11 LB17 5D121 AA02 AA04 DD05 FF01

Claims (14)

[Claims] At least a recording layer is formed on a substrate, and a light transmitting member is bonded on the recording layer. The substrate has a step portion that is more convex than the recording layer. An optical recording medium, wherein the light transmitting member is attached to a portion. 2. The optical recording medium according to claim 1, wherein said substrate is formed by injection molding. 3. The recording medium according to claim 1, wherein the step is formed to be higher by 10 μm to 100 μm than a surface on which the recording layer is formed. 4. The optical recording medium according to claim 1, wherein the light transmitting member is a light transmissive sheet bonded via an adhesive layer. 5. The optical recording medium according to claim 4, wherein said sheet is made of a thermoplastic resin. 6. The optical recording medium according to claim 4, wherein said sheet is formed by injection molding. 7. The optical recording medium according to claim 4, wherein said sheet is formed thinner than said substrate. 8. The optical recording medium according to claim 4, wherein a recording layer is formed on at least the main surface of the sheet on the side of the adhesive layer. 9. The optical recording medium according to claim 8, wherein a recording layer is formed on both principal surfaces of the sheet. 10. The optical recording medium according to claim 4, wherein the sum of the thicknesses of the sheet and the adhesive layer is 177 μm or less. 11. The optical recording medium according to claim 4, wherein a plurality of the sheets are stacked via the adhesive layer. 12. The optical recording medium according to claim 1, wherein the light transmitting member is a substrate having a light transmitting property. 13. The optical recording medium according to claim 12, wherein said substrate is formed by injection molding. 14. The recording medium according to claim 1, wherein a recording layer is formed on at least one principal surface of the substrate.
3. The optical recording medium according to 2.