JP2004103070A - Manufacturing method for surface recording flexible optical disk substrate and for flexible optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the curing distortion when a fine ruggedness pattern of a stamper is transferred to a base film and furthermore to suppress the curing distortion of a transfer layer by making the curing shrinkage factor to be ≤10%, as to a manufacturing method for a flexible optical disk substrate utilizing the surface recording method (such that a pregroove surface of the disk positions at a pickup side to record/reproduce information at this surface). <P>SOLUTION: When the fine ruggedness pattern of the stamper is transferred to the base film on the premise of the manufacturing method for the flexible optical disk substrate utilizing the surface recording method, a monomer material not forming the cross-linking structure at the curing time is used. As this monomer material, a monofunctional acrylate monomer material is used. The viscosity of this monofunctional acrylate monomer material is 10-100 mPa s, and the curing shrinkage factor thereof is ≤10%. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a high recording density optical disk and a method for manufacturing the same, and can improve the reliability of a flexible optical disk system by devising a processing technique using a flexible sheet and an appliance made of an ultraviolet curable resin. .
[0002]
[Prior art]
Optical discs are widely used as CDs and DVDs because they are removable and have a large capacity. This is because a recording film is formed on a polycarbonate substrate having a thickness of 1.2 or 0.6 mm to transmit signals. Recording and reproduction are performed by an optical pickup. In order to accurately condense light on the recording surface of the optical disk, a high positional accuracy of the optical pickup with respect to the recording surface is required, so the substrate is flattened, rigidity is secured, and the recording surface flatness is secured. In order to follow the undulation of the recording surface, servo is applied to the optical pickup to obtain the position accuracy of the optical pickup with respect to the recording surface.
At present, research and development for further reducing the diameter of the light spot by increasing the numerical aperture (NA) of the objective lens or shortening the wavelength of the laser in order to further increase the recording capacity are being conducted. When the NA is increased, the distance between the recording surface and the optical pickup becomes smaller, and it is necessary to control this distance with higher accuracy. On the other hand, the response of servo control of the position of the optical pickup is limited, and it is difficult to accurately control the position with the required accuracy. For this reason, in order to increase the NA, the tilt (plane deflection) of the substrate must be reduced to a range where highly accurate position control is possible. For this reason, it is necessary to improve the accuracy of the manufacturing substrate, mount a tilt (plane deflection) servo on the pickup, provide a thin cover layer of about 0.1 mm on the recording recording film, and perform recording / reproduction from the cover side. In order to increase the tilt (surface runout) margin, various measures have been taken.
[0003]
Reducing the tilt (plane runout) can be achieved by devising the material and manufacturing method of the substrate, but has the problem of significantly increasing the cost. Also, in the method of reproducing from the recording film side without passing through the substrate (surface recording type), the distance between the recording film surface and the objective lens can be secured only about 0.1 mm, so that a rotating ordinary optical disk (rigid body) and an objective lens can be used. Means for preventing the collision with the lens include improving the chucking accuracy of the disk so as to reduce the surface runout. However, these all lead to increased costs.
[0004]
Therefore, rather than increasing the rigidity of the optical disk itself to increase its mechanical accuracy, the objective lens is manufactured by manufacturing the disk from a flexible material, providing a guide on the side opposite to the recording / reproducing surface, and rotating the disk. The optical disk is aerodynamically levitated (Bernoulli floating; non-contact) by a guide facing the optical disk and the optical disk, and a constant air bearing layer is formed between the optical disk rotating at a constant rotational speed and the guide. By stabilizing the positional relationship between the optical disk and the guide, the vibration (tilt) of the recording surface with respect to the optical pickup disposed opposite to the guide can be made as close as possible to zero, thereby enabling the surface recording type It can be made to function as an optical disk (for example, Japanese Patent Application No. 2001-118344).
The outline of this flexible optical disk system is as shown in FIG. That is, a stamper is transferred to one surface of a flexible substrate to form a transfer surface, a recording layer is laminated on the transfer surface, a protective layer is laminated on the recording layer to form a flexible optical disk, and an objective lens is disposed on the protective layer side. (Optical pick-up) and the guide that constitutes the dynamic air bearing on the back side of the flexible substrate, and the flexible optical disk is rotated at a high speed. In this way, the distance between the objective lens (optical pickup) and the surface of the protective layer is made small to stabilize the flexible optical disk irrespective of bending, undulation, and the like. -118344).
[0005]
As a conventional method for manufacturing this flexible optical disk substrate, a thermoplastic resin or a thermosetting resin is applied to the surface of a flexible sheet such as a PET film, and this is used as a transfer layer. A heat press method in which a recording film is formed after heat curing, or a UV curable resin is also applied to the surface of a flexible sheet, and this is used as a transfer layer. The fine pattern of the stamper is transferred to this and cured by UV curing. A 2P (Photo Polymerization) method for forming a recording film (Japanese Patent No. 2942430) or a method in which a flexible organic material sheet is heated to a softening point or higher, a stamper is pressed, cooled, and then separated from the sheet ( JP-A-6-60423 (Patent Document 3) and the like. In addition, there is another one described in JP-A-11-273147. This conventional example is a direct embossing method in which a transparent film is thermocompressed, in which the transparent film is pressure-compressed after the temperature is increased.However, according to this method, temperature variations and stress variations in the plane of the transparent film are reduced. It is difficult to make the film extremely small and uniform, so that the optical characteristics, mechanical strength, warpage, and the like of the transparent film tend to vary.
[0006]
Further, the 2P method is excellent in transferability, and the potential for this portion is superior to other transfer methods.
In the case of the 2P method, the total thickness of the flexible optical disk depends on the thickness of the film to be transferred, the transfer layer, and the recording film. Since the film itself is mass-produced industrially, the thickness distribution is suppressed to an accuracy of about ± 1 μm. Also, since the recording film is of the order of nanometers, it is almost negligible for variations in the thickness of the flexible optical disk. The transfer layer is the most severely controlled in the film thickness distribution by this method. As a material for forming a transfer layer of an optical disk, a material mainly composed of a radical polymerization type UV resin is mainly used for the efficiency of transfer process, low cost, stability, reliability and the like.
[0007]
By the way, when curing a radical polymerization type UV resin, depending on the UV resin material, a plurality of materials are blended, and there is a significant difference in the curing speed between each material, and a material having a fast curing speed cures immediately. However, a material having a low curing speed requires time for curing. Commonly used oligomers and polyfunctional monomers form a crosslinked structure during curing, but if a material with a fast curing speed forms a crosslinked structure, it will be incorporated into the crosslinked structure with a material with a slow curing speed. The material that has been cured is insufficiently cured at that stage and remains in a microgel state, which causes irregularities (distortion) on the surface of the transfer layer (see FIG. 9). FIG. 9 (a) shows a microgel that does not remain, and FIG. 9 (b) shows a microgel that remains.
[0008]
On the other hand, in the case of optical disks such as CDs and DVDs, the distance between the recording surface and the optical pickup is relatively large, and the smoothness of the substrate is high, so that the distortion of the recording surface has no problem in relation to the servo response of the optical pickup. In addition, since the rigidity of the substrate is high, the distortion of the transfer surface does not become obvious, and even if it becomes obvious, a slight distortion does not matter. However, in the case of a surface recording type flexible optical disk, the distance between the optical pickup and the recording surface is small (usually 100 μm), and therefore the margin for servo control of the optical pickup is small. On the other hand, the conventional flexible optical disk has a flexible and non-smooth substrate, and furthermore, the distortion of the transfer layer becomes obvious and the distortion of the recording surface is large. For this reason, the residual focus error remaining when the focus servo and tracking servo of the optical pickup are locked becomes large, and the servo becomes unstable and easily comes off, resulting in poor recording / reproducing characteristics. (See FIG. 6A. This figure shows a residual focus error when a transfer layer is formed with a polyfunctional monomer.) Therefore, there is a problem that a highly reliable flexible optical disk system cannot be established.
[0009]
When a phase-change recording film is used, a protective layer is formed to suppress the deterioration of C / N and jitter at the time of direct overwriting, but the surface recording type protective layer needs to function as an optical transmission film. It is essential that the interface with the air layer be a smooth surface.
From the above, the surface recording type flexible optical disk is required to have a surface roughness of 0.1 μm or less as the smoothness of the transfer layer and the protective layer, and to further improve the reliability of recording and reproduction. In addition, it is required to reduce the surface deflection of the flexible optical disk as much as possible.
[0010]
[Patent Document 1] Japanese Patent Application No. 2001-118344
[Patent Document 2] Japanese Patent No. 2942430
[Patent Document 3] JP-A-6-60423
[Patent Document 4] JP-A-11-273147
[0011]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a flexible optical disk having high-quality recording / reproducing signal characteristics by solving the above-mentioned problems of the conventional method for manufacturing a flexible optical disk substrate. The tasks are as follows.
[0012]
[Problem 1] (Corresponding to Claims 1, 2, and 4)
The first problem is that in a method of manufacturing a surface recording type (a pre-groove surface of a disk is provided on a pickup side and recording / reproducing is performed on the pre-groove surface) flexible micro-substrate substrate, when a fine pattern of concavities and convexities of a stamper is transferred to a base film, curing distortion is caused. Is further reduced, and the curing shrinkage is set to 10% or less to further suppress the curing distortion of the transfer layer.
[0013]
[Problem 2] (corresponding to Claims 3 and 6)
A second problem is to suppress the distortion of the transfer layer so that the transfer layer can be formed to have a thickness of 1 to 10 μm.
[Problem 3] (corresponding to claim 5)
The problem 3 is to provide the transfer layer with appropriate rigidity so as to reduce surface runout as much as possible.
[Problem 4] (Corresponding to Claims 7, 8, and 9)
The problem 4 is to make it possible to form a smooth protective layer, and to set the hardness of the protective layer to 2H or more and the thickness of 10 to 50 μm so that the base film and the recording film (recording) can be initialized and recorded. Layer).
[0014]
[Measures taken to solve the problem]
[Solution 1] (corresponding to claim 1)
Means taken to solve the above problem 1 is based on a method of manufacturing a surface recording type flexible optical disk substrate,
When transferring the fine pattern of concavities and convexities of the stamper to the base film, a monomer material which does not have a crosslinked structure at the time of curing is used.
[0015]
[Action]
When transferring the micropatterned pattern of the stamper to the base film, if a monomer material that takes on a crosslinked structure during curing is used, the monomer material with a slower curing rate is incorporated into the monomer material that takes on a crosslinked structure during the curing process of the transfer layer and this is cured. It remains in the state of a microgel having insufficient properties, and causes irregularities in the transfer layer. That is, the thickness of the transfer layer is not stable (see FIG. 5 (a). This figure shows the circumferential film thickness distribution when the transfer layer is formed of a polyfunctional monomer). In the case of a flexible optical disk, the residual focus error remaining when the focus servo and tracking servo of the optical pickup are locked increases, and the servo becomes unstable and easily detached, resulting in poor recording / reproducing characteristics. Is as described above. On the other hand, when a monomer material that does not have a crosslinked structure during curing is used, the curing proceeds uniformly, so that it does not remain in the state of a microgel with insufficient curability, and therefore, a microgel with insufficient curability. The transfer layer does not suffer from unevenness due to remaining in the gel state, and the thickness of the transfer layer is stabilized (see FIG. 5B. The figure shows a monofunctional monomer (monofunctional acrylate monomer). 3) shows the circumferential film thickness distribution when the transfer layer is formed in (2)). Therefore, the distortion of the transfer layer does not overlap with the distortion of the flexible optical disk substrate, so that the distortion of the recording surface does not increase, and no residual focus error occurs (see FIG. 6 (b). This shows a residual focus error when a transfer layer is formed).
[0016]
Embodiment 1
In the first embodiment, a monofunctional acrylate monomer material is used in the method for manufacturing a flexible optical disk substrate according to the first aspect.
[Action]
By using a monofunctional acrylate monomer material as the “monomer material that does not take a crosslinked structure during curing” in Solution 1, the transfer layer cures uniformly because it is a material that does not take a three-dimensional crosslinked structure. Therefore, it is possible to reliably prevent the transfer layer from being unevenly deformed due to remaining in the state of the microgel having insufficient curability, and to stabilize the film thickness.
[0017]
Embodiment 2 (corresponding to claim 3)
The second embodiment is that the monofunctional acrylate monomer material of the first embodiment has a viscosity of 10 to 100 mPa · s.
[Action]
When the viscosity of the monofunctional acrylate monomer material is 10 to 100 mPa · s, the thickness of the transfer layer can be made thin and uniform, and the warpage due to the curing shrinkage of the UV resin is reduced.
FIG. 2 shows the relationship between the viscosity and the film thickness of the monofunctional acrylate monomer. When spin-coating at 5000 rpm, the viscosity is 10 to 100 mPa and the film is spread to a film thickness of 10 μm or less. It is clear from
The relationship between the thickness of the transfer layer and the runout is as shown in FIG. 3. It is apparent from FIG. 3 that when the thickness of the transfer layer is 10 μm or less, the runout is suppressed to 10 μm or less.
[0018]
Embodiment 3 (corresponding to claim 4)
A third embodiment is that the monofunctional acrylate monomer material of the first embodiment has a curing shrinkage of 10% or less.
[Action]
As the curing shrinkage of the monofunctional acrylate monomer material is smaller, the curing strain is smaller, and there is no particular problem if the curing shrinkage is 10% or less. The tendency to be inhibited is significant. Therefore, by using a monofunctional acrylate monomer material having a curing shrinkage of 10% or less, the run-out stability of the disk is not impaired due to reverse warpage due to shrinkage.
[0019]
Embodiment 4 (corresponding to claim 5)
Embodiment 4 is that in the solution 1, the cured transfer layer has a pencil hardness of F to 2H.
[Action]
If the cured transfer layer has a pencil hardness of less than F, rigidity is insufficient during air levitation to stabilize surface runout, and if it exceeds 2H, surface runout is also difficult to stabilize due to lack of flexibility, and recording / reproducing. However, when the pencil hardness is in the range of F to 2H, an appropriate rigidity that does not have the above two problems is provided.
The relationship between the hardness of the transfer layer and the amount of surface runout is as shown in FIG. 4. The hardness is lower than F and the surface runout increases sharply as the hardness is higher than 2H. It is evident that the surface runout was minimal and was suppressed to 10 μm or less.
[0020]
Embodiment 5 (corresponding to claim 6)
Embodiment 5 is that, in Solution 1, the thickness of the transfer layer is 1 to 10 μm.
[Action]
If the thickness of the transfer layer is less than 1 μm, it is difficult to form the transfer layer stably, and if it exceeds 10 μm, the reverse warpage due to curing shrinkage becomes large, and the amount of surface run-out during air floating increases. When the thickness of the transfer layer is 1 to 10 μm, the transfer layer can be formed as much as possible by spin coating as long as the thickness of the transfer layer is uniform and the reverse warpage due to curing shrinkage is not remarkable. Can be made thinner.
[0021]
[Solution 2] (corresponding to claim 7)
Solution 2 is based on the premise of Solution 1, that after forming a phase-change recording film on the base film on which the transfer layer is formed, a protective layer is formed on the recording / reproducing surface side, and the material of the protective layer is a monofunctional acrylate monomer. There is something.
[0022]
[Action]
As for the protective layer of the transfer layer, if a monomer material having a crosslinked structure upon curing is used, the protective layer itself will be distorted as in the case of the transfer layer, and this will increase the distortion of the surface of the flexible optical disk, and the optical disk surface will become an optical pickup. However, since the protective layer is made of a monofunctional acrylate monomer, distortion of the protective layer itself is reduced, and the above risk is reduced.
[0023]
Embodiment 1 (corresponding to claim 8)
Embodiment 1 is that in the solution 2, the hardness of the protective layer is 2H or more in pencil hardness.
[Action]
If the hardness of the protective layer is less than 2H in pencil hardness, the increase in the N level (noise level) is remarkable, and the C / N is suddenly reduced due to the decrease in the C level (carrier level). If so, it is possible to avoid an increase in the N level due to the recording film floating from the substrate during direct overwriting.
[0024]
Embodiment 2 (corresponding to claim 9)
The second embodiment is that the protective layer has a thickness of 10 to 50 μm.
[Action]
When the thickness of the protective layer is less than 10 μm, the C / N ratio after direct overwrite is remarkably reduced. On the other hand, when the thickness exceeds 50 μm, the reverse warpage due to curing shrinkage is too large, and the surface deflection of the disk during air floating is reduced. Difficult to stabilize. Therefore, 10 to 50 μm is an appropriate range that does not cause both of the above problems. In addition, due to the rigidity of the protective layer having this thickness range, separation between the base film and the recording film (recording layer) during initialization and recording / reproducing can be avoided (solution of Problem 4).
[0025]
Embodiment
When manufacturing a flexible optical disk, a material and a method for manufacturing the same that enable high quality C / N and jitter characteristics after direct overwriting by forming a smooth transfer layer and a protective layer. An example will be described with reference to the drawings.
It should be noted that the "monomer material which does not have a crosslinked structure at the time of curing" referred to in Solution 1 is not a monofunctional monomer material. Monofunctional acrylate monomer materials include phenoxyethyl acrylate, nonylphenoxyethyl acrylate, tetrahydrofurfuryloxyethyl acrylate, cyclohexaneoxyethyl acrylate, tetrahydrofurfuryloxyhexanolide acrylate, 1,3-dioxolan acrylate, acryloyl morpholine, tricyclo There are decanyloxy acrylate and the like, and among them, nonylphenoxyethyl acrylate resin is one of the most preferable ones because it can be easily controlled to a desired film thickness by a spin coating method.
[0026]
Embodiment 1
Nonylphenoxyethyl acrylate resin (viscosity: 80 mPa · s), which is a monofunctional acrylate monomer material, is applied on the stamper by a spin coating method to form a transfer layer 10 having a thickness of 5 μm, and a transfer layer 10 having a thickness of 75 μm is formed thereon. By laminating the PET film 11 and separating the stamper and the resin from the stamper, a flexible optical disc substrate having a smooth surface having irregularities for recording information or grooves for tracking is obtained. A phase change recording layer 12 having a thickness of 0.2 μm is formed by a sputtering method on the resin surface of the flexible optical disk substrate (the surface of a transfer layer having irregularities for recording information or grooves for tracking). I do. This is the flexible optical disk substrate shown in FIG. Nonylphenoxyethyl acrylate resin (viscosity: 80 mPa · s) is applied to the recording surface of this flexible optical disk substrate by spin coating to form a protective layer 13 having a thickness of 20 μm, thereby completing the flexible optical disk shown in FIG. Let it.
In the spin coating method described above, the stamper is rotated at a high speed, a molten resin is applied in an annular shape to the inner peripheral portion of the stamper, and the resin is spread radially outward by centrifugal force. This is a method of forming a layer, which is a conventionally known and commonly used thin film coating method. The film thickness is controlled by the viscosity of the acrylate monomer and the rotation speed of the stamper.
[0027]
The flexible optical disk completed as described above is mounted on an evaluation device as shown in FIG. 1, and the guide is brought close to the surface of the film 11 to stabilize the surface deflection of the optical disk in a state where the air is levitated. A test for recording and reproducing data by locking the tracking servo was performed. As a result, it was confirmed that no wrinkles, floating, or cracks occurred in the transfer layer.
The thickness of the transfer layer is appropriately 1 to 10 μm, but in this example, the transfer layer was formed to 5 μm at a spin speed of 5000 rpm.
[0028]
If the thickness of the transfer layer is less than 1 μm, it is difficult to stably form a transfer layer having a constant thickness. If the thickness of the transfer layer is 10 μm or more, reverse warpage due to curing shrinkage increases, and the surface run-out during air levitation is stable. As a result, focus servo cannot be performed, and recording and reproduction cannot be performed.
Further, in order to form the film thickness of the transfer layer uniformly, or because there is a risk that the stamper may fly away from the chucking table due to high-speed spin, it is preferable to set the spin rotation speed to about 5000 rpm. By using the above-mentioned nonylphenoxyethyl acrylate resin (viscosity: 80 mPa · s), a transfer layer having a thickness of 1 to 10 μm can be easily formed.
[0029]
In addition, the surface deflection of the flexible optical disk at the time of air floating is highly dependent on the pencil hardness of the cured film. When the pencil hardness is less than F, the rigidity is insufficient at the time of air floating and the surface deflection is difficult to stabilize. In addition, the surface deflection is also difficult to stabilize due to insufficient flexibility, and recording / reproduction becomes impossible. In this example, the pencil hardness is set to H.
[0030]
The curing shrinkage of the resin is not particularly problematic even if the curing shrinkage is lower than this, but if it exceeds 10%, the amount of reverse warpage due to shrinkage becomes large, and stabilization of disk runout cannot be achieved. . The cure shrinkage of this example was approximately 8.5%, and it was confirmed that the amount of reverse warpage of the flexible optical disk was 0.1 mm or less.
Further, as for the protective layer of the recording film, in the case of a surface recording type optical disk, a function as an optical transmission layer is required, and therefore, like the transfer layer, a monofunctional acrylate monomer material is desirable. If the hardness of the protective layer is 2H or more, it is possible to avoid an increase in the N level due to the floating of the recording film from the substrate during direct overwriting. If it is softer than 2H, the increase in the N level is remarkable, and the C / N decreases at a stretch due to the decrease in the C level, so the hardness of the protective layer in this example is 2H.
Further, if the thickness of the protective layer is less than 10 μm, the C / N ratio after direct overwrite is remarkably reduced. Difficult to stabilize. In this example, the thickness of the protective layer was controlled to approximately 20 μm by setting the rotation speed in spin coating to 4000 rpm. The C / N of the flexible optical disk of this example after direct overwrite was 52 dB, and the surface runout was 5 μm or less, confirming that it was extremely stable.
[0031]
Embodiment 2
The second embodiment is a flexible optical disk manufactured in the same manner as the first embodiment. However, it differs from Example 1 in that tricyclodecanyloxyacrylate (12 mPa · s), which is a monofunctional acrylate monomer, is used as a material for the transfer layer and the protective layer. A transfer layer having a thickness of 2 μm was formed at a spin speed of 5000 rpm, and a protective layer having a thickness of 15 μm was formed at the spin speed of 4000 rpm using the same material.
The test results of Example 2 were almost the same as those of Example 1, and it was confirmed that no wrinkles, floating, and cracks occurred in the transfer layer.
[0032]
Embodiment 3
The third embodiment is a flexible optical disk manufactured in the same manner as the first embodiment. However, it differs from Example 1 in that the material of the transfer layer and the protective layer uses tetrahydrofurfuryloxyhexanolide acrylate (150 mPa · s) which is a monofunctional acrylate monomer.
The transfer layer having a thickness of 8 μm was formed at a spin speed of 5000 rpm, and a protective layer having a thickness of 40 μm was formed at a spin speed of 4000 rpm.
The test result of Example 3 was almost the same as that of Example 1, and no wrinkles, floating, and cracks of the transfer layer were observed.
[0033]
[Comparative Example 1]
In Comparative Example 1, a flexible optical disk was manufactured in the same manner as in Example 1. However, the difference is that a photopolymerizable prepolymer is used as a material for the transfer layer and the protective layer. A transfer layer having a thickness of 8 μm was formed at a spin speed of 5000 rpm, and a protective layer having a thickness of 15 μm was formed at a spin speed of 3500 rpm.
The test result of Comparative Example 1 showed that a microgel was generated during curing, the transfer layer thickness distribution was not stable, the residual focus error was large, and recording / reproduction was impossible.
[0034]
[Comparative Example 2]
In Comparative Example 2, a flexible optical disk was manufactured in the same manner as in Example 1. However, the difference is that a polyfunctional acrylate monomer (viscosity 500 mPa · s) is used as a material for the transfer layer and the protective layer. A transfer layer having a thickness of 10 μm was formed at a spin speed of 5000 rpm, and a protective layer having a thickness of 20 μm was formed at a spin speed of 4000 rpm.
The test result of Comparative Example 2 showed that a microgel was generated during curing, the transfer layer thickness distribution was not stable, the residual focus error was large, and recording / reproduction was impossible.
As described above, a smooth transfer layer cannot be obtained for the transfer layer and the protective layer. Therefore, even if the surface run-out is stabilized by air levitation, a servo error occurs due to the unevenness of the surface, and the recording / reproduction is surely performed. I couldn't. In addition, wrinkles, floating, and cracks were observed in the transfer layer, and the crack area was further enlarged by rotating and floating the disk.
[0035]
【The invention's effect】
The effects of the present invention are summarized below for each main claim.
1. Effects of the Inventions of Claims 1, 2, and 4
In the method of manufacturing a surface recording type flexible optical disc substrate, when transferring the fine pattern of the concavo-convex pattern of the stamper to the base film, a monomer material which does not take a crosslinked structure upon curing, particularly a monofunctional acrylate monomer material (Claim 2) is used. Thereby, there is no distortion of the transfer layer at the time of curing, and curing shrinkage can be suppressed to a small value. Also, the difference in curing speed between the blended materials is small, specifically, the curing shrinkage is 10% or less (claim 4), and no microgel is generated on the cured film surface, and the cured film is smooth. A transfer layer is obtained.
[0036]
2. Effects of the Inventions of Claims 3 and 6
When the viscosity of the monofunctional acrylate monomer material is 10 to 100 mPa · s or less, a thin film of the transfer layer can be formed, and specifically, the thickness of the transfer layer is 1 to 10 μm. In addition, it is possible to reduce warpage due to curing shrinkage.
[0037]
3. Effect of the invention of claim 5
When the pencil hardness of the cured transfer layer is F to 2H, the rigidity of the transfer layer can be made appropriate, whereby the flexible optical disk can be stably aerodynamically levitated.
[0038]
4. Effects of the Inventions of Claims 7, 8, and 9
Even if a phase change recording film is formed on the base film on which the transfer layer is formed, no wrinkles, floating, or cracks occur in the transfer layer. By forming the protective layer which is a monofunctional acrylate monomer material on the recording / reproducing surface side (claim 7), it is possible to form a smooth protective layer, and errors occur in the initialization step and the recording / reproducing step. When the protective layer has a hardness of 2H or more (Claim 8) and a thickness of 10 to 50 μm (Claim 9), it is possible to initialize and record the base film during recording and reproduction. Separation from the film can be avoided, and deterioration of C / N and jitter during direct overwrite can be suppressed.
[0039]
5. Effects of the Inventions of Claims 10 and 11
Since the transfer layer and the protective layer are monofunctional acrylate monomers, the distortion of the surface of the transfer layer and the distortion of the protective layer are remarkably reduced. Remarkably high. Therefore, the focus control can be reliably performed by the servo control of the optical pickup, and the occurrence of a focus control error is significantly reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a state of a flexible optical disk and a drive (an objective lens of a pickup) of the present invention.
FIG. 2 is a graph showing the relationship between resin viscosity and film thickness.
FIG. 3 is a graph showing a relationship between a transfer layer thickness and a disk surface deflection amount.
FIG. 4 is a graph showing the relationship between the pencil hardness of the transfer layer and the amount of runout.
FIG. 5 (a) is a drawing showing a circumferential film thickness distribution when a transfer layer is formed with a polyfunctional monomer, and FIG. 5 (b) is a view when a transfer layer is formed with a monofunctional monomer. 3 is a drawing showing a film thickness distribution in a circumferential direction.
6A is a diagram illustrating a residual focus error when a transfer layer is formed with a polyfunctional monomer, and FIG. 6B is a diagram illustrating a residual focus error when a transfer layer is formed with a monofunctional monomer. FIG.
FIG. 7 is a schematic diagram showing a configuration of a film + a transfer layer + a recording film.
FIG. 8 is a schematic diagram showing a configuration of a film + a transfer layer + a recording film + a protective layer.
FIGS. 9A and 9B are photographs at 200 magnifications showing the surface appearance of a transfer layer using a monofunctional acrylate monomer and a polyfunctional acrylate monomer.
[Explanation of symbols]
10: transfer layer
11: Film
12: Recording layer
13: protective layer

Claims (11)

In the method for manufacturing a surface recording type flexible optical disk substrate,
A method for manufacturing a flexible optical disk substrate, comprising using a monomer material which does not have a crosslinked structure when cured when transferring a fine pattern of concavities and convexities of a stamper to a base film. 2. The method according to claim 1, wherein said monofunctional acrylate monomer material is used. 3. The method according to claim 2, wherein the monofunctional acrylate monomer material has a viscosity of 10 to 100 mPas. 3. The method according to claim 2, wherein the monofunctional acrylate monomer material has a cure shrinkage of 10% or less. 2. The method according to claim 1, wherein the cured transfer layer has a pencil hardness of F to 2H. 2. The method according to claim 1, wherein said transfer layer has a thickness of 1 to 10 [mu] m. On the premise of the method for manufacturing a flexible optical disk substrate according to claim 1, after forming a phase-change recording film on a base film on which a transfer layer is formed, forming a protective layer of a monofunctional acrylate monomer on the recording / reproducing surface side. A method for manufacturing a flexible optical disk, which is characterized in that: 8. The method for manufacturing a flexible optical disk according to claim 7, wherein the hardness of the protective layer is 2H or more in pencil hardness. 8. The method according to claim 7, wherein said protective layer has a thickness of 10 to 50 [mu] m. A surface recording type flexible optical disk substrate comprising a flexible sheet, a transfer layer, and a recording layer, wherein the transfer layer is a transfer layer made of a monofunctional acrylate monomer. A surface recording type flexible optical disk having a flexible sheet, a transfer layer, a recording layer, and a protective layer, wherein the transfer layer and the protective layer are made of a monofunctional acrylate monomer.

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