JP2001344819A - Transmittable sheet roll goods for optical information recording medium and optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide transmittable sheet roll goods for an optical information recording medium, on the transmittable sheet of which indentations and scratches can be prevented from being generated. SOLUTION: Protection sheets 8 are stuck to both sides of the transmittable sheet 4 while interposing an adhesive agent 6 when the transmittable sheet roll goods for the optical information recording medium are manufactured. As a result, indentations and scratches can be prevented from being generated on the transmittable sheet to be used for manufacturing an optical disk D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent sheet material for an optical information recording medium capable of increasing the recording density by reducing the thickness of a reading surface on which a reading or writing laser beam is incident, and a method of manufacturing the same. The present invention relates to an optical information recording medium provided with an incident surface layer by attaching a transparent sheet taken out from the optical information recording medium.

[0002]

2. Description of the Related Art In recent years, optical information recording media such as optical disks have been developed with the aim of achieving high density, large capacity and small size of recorded information. To increase the density of recorded information, shorten the wavelength of the laser beam for reading or writing, or increase the numerical aperture of the objective lens for irradiating the light for recording / reproducing with an optical pickup. This is possible by reducing the light spot diameter at the time. As described above, when the numerical aperture of the objective lens is increased, it is necessary to reduce the thickness of the substrate on the incident surface side of the optical disc through which laser light for reproduction is irradiated and passes therethrough. This is because the allowable amount of the angle (tilt angle) at which the disc surface deviates from the perpendicular to the optical axis of the optical pickup becomes small, and the tilt angle is easily affected by aberration and birefringence due to the thickness of the substrate. It is because it becomes. Therefore, it is necessary to reduce the tilt angle as much as possible by making the thickness of the substrate as thin as possible.

For example, a CD (Compact Dis)
The thickness on the incident surface side of c) is about 1.2 mm, while the DVD (Digital) whose recording capacity is 6 to 8 times that of CD is used.
talVersatile Disc) is about 0.6mm
About. Recently, there has been a demand for a large recording capacity of 15 GB or more per disc of the same size as a CD or DVD. For example, if the substrate thickness on the incident surface side is about 0.3 mm, the recording capacity is 15 GB. When the thickness of the substrate on the incident surface side is about 0.1 mm, the recording capacity becomes 20 GB. Since it is difficult to manufacture such an optical disk having a high recording capacity by a conventional injection molding method because the substrate is too thin, some other disk manufacturing methods have been proposed.

As an example, a substrate made of a polycarbonate resin (hereinafter, also referred to as a PC resin) on which information signals are recorded is manufactured by injection molding or the like in the same manner as a CD or DVD, and aluminum or the like is formed on the information signal surface. A reflective film is formed by sputtering or the like, and a transparent sheet having the same size as the substrate is bonded thereon by a spin coating method using a transparent adhesive. The reading in which the laser beam is incident is performed from the transparent sheet side, and the sum of the thickness of the transparent sheet and the thickness of the adhesive becomes the incident surface layer. For example, if the recording capacity is 15 GB, the thickness of the incident surface layer Becomes about 0.3mm,
If the recording capacity is 20 GB, the thickness of the incident layer is about 0.1 mm.
Becomes At this time, the thickness of the substrate is 0.6 mm or more, at which injection molding is possible.

[0005]

By the way, the above-mentioned permeable sheet is delivered as a roll of a material having a width of about 300 mm to 1500 mm and a length of several hundred meters. Is easily charged, and dust or the like adheres to the sheet during manufacturing, and indentations and scratches that may have occurred due to the sheet itself being wound may enter the permeable sheet. When a sheet is used as an incident surface layer, not only adversely affects signal characteristics such as an error rate, but in the worst case, recorded data may not be reproduced. Also,
Among manufacturers of commercially available permeable sheets, some manufacturers attach a protective sheet to one side of the permeable sheet with an adhesive and deliver it in a roll form. Indentations and abrasions were sometimes observed. Furthermore, in the case where the thickness of the pressure-sensitive adhesive is thin even on the surface on which the protective coat is stuck, or when the pressure-sensitive adhesive becomes harder due to aging or the like than the permeable sheet, indentations and scratches are seen,
Indentations and scratches generated on the permeable sheet have become problems. The present invention has been made in view of the above problems, and has been made in order to effectively solve the problems. The purpose of the present invention is to provide a light-transmitting sheet capable of preventing indentations and scratches from being generated. An object of the present invention is to provide a transparent sheet material for an information recording medium and an optical information recording medium.

[0006]

The invention according to claim 1 is
A transparent sheet raw material for an optical information recording medium, comprising a protective sheet attached to both sides of a transparent sheet via an adhesive. The invention according to claim 2 is a protective sheet on both sides of a transparent sheet material obtained by pasting protective sheets on both sides of a transparent sheet via an adhesive on the information surface side of a substrate on which an information surface is formed. The optical information recording medium is characterized in that the transparent sheet taken out by integrally peeling off the adhesive and the adhesive is joined.

As described above, by attaching the protective sheet to both surfaces of the permeable sheet via the adhesive, it is possible to prevent the permeable sheet itself from being indented or scratched. And such a permeable sheet,
By using the optical information recording medium as an incident surface layer, it is possible to maintain a high recording density while maintaining a high quality of a reproduction signal.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an optical information recording medium according to an embodiment of the present invention; FIG. 1 is a view showing a state in which a raw sheet of a transparent sheet for an optical information recording medium according to the present invention is wound in a roll shape, FIG. 2 is an enlarged view showing a portion A in FIG. 1, and FIG. FIG. 4 is a sectional view showing an optical disc formed by bonding a transparent sheet to a substrate, showing a state in which a protective sheet is peeled off from the opposite side. Here, a case of manufacturing a read-only type (ROM type) optical disk will be described as an example. As shown in FIG. 1, here, the transparent sheet material 2 of the optical information recording medium is wound in a roll shape.
Specifically, as shown in FIG. 2, the permeable sheet material 2 is formed by attaching protective sheets 8, 8 to both surfaces of a permeable sheet 4 via adhesives 6, respectively. This is wound into a roll as described above. When the permeable sheet 4 is used, as shown in FIG. 3, the protective sheet 8 integrated with the adhesive 6 is peeled off from both surfaces of the permeable sheet 2 to take out the permeable sheet 4 inside. At this time, the protective sheet 8 and the adhesive are determined based on the adhesion between the transparent sheet 4 and the adhesive 6 so that the integral body of the adhesive 6 and the protective sheet 8 is peeled off from the surface of the transparent sheet 4 as described above. 6 is set to be stronger. The pressure-sensitive adhesive 6 has a lower hardness than the permeable sheet 4.

Thus, for example, even when dust 10 (see FIG. 2) is attached to the surface of the permeable sheet 4 due to electrification of the permeable sheet 4 at the time of manufacturing the permeable sheet 2, the particle size of the dust is reduced. If the thickness of the pressure-sensitive adhesive 6 is increased, dust enters the pressure-sensitive adhesive 6 so as to be buried in the pressure-sensitive adhesive 6. No scuffing. Further, when the permeable sheet 4 is used, the dust 10 remains in the adhesive 6 that is peeled off from the permeable sheet 4, and does not adhere to the surface of the permeable sheet 4. The hardness is represented by, for example, the depth at which the needle tip enters the measurement object when the needle tip having a predetermined shape is pressed against the surface of the sheet or the measurement object of the adhesive with a constant load. The deeper the depth, the lower the hardness. The reason for adopting this method is that in a hardness test such as the general Vickers method or the Rockwell method, a measuring needle with a fixed shape is pressed against the measurement object, and the hardness is checked by the size of the dent. The reason is that when the pressure is released after pressing the measuring needle, the dents have the property of returning to the original state and cannot be used.

Here, as the material of the transparent sheet 4, any material having excellent optical characteristics such as a polycarbonate sheet, an acrylic sheet, a polyolefin sheet such as Zeonex or Arton, a triacetate sheet, and a vinyl ester sheet can be used. Further, most of the adhesive such as acrylic, silicone, and rubber can be used as the adhesive 6. Further, examples of the material of the protective sheet 8 include polymer materials such as a polyester sheet, a polyethylene sheet, a polypropylene sheet, and a polyethylene terephthalate sheet. As described above, the transparent sheet 4 taken out as shown in FIG. 3 is, as shown in FIG.
Adhesive layer 1 made of, for example, a UV-curable resin
4 and the like, and the optical disc D is formed. Here, the surface of the substrate 4 to which the transmissive sheet 4 is bonded is formed as an information surface by forming, for example, pits 16 of unevenness, and the information surface has a reflection surface made of, for example, aluminum. A film 18 has been deposited. Then, a layer in which the adhesive layer 14 and the transmissive sheet 4 are combined is formed as an incident layer, and a laser beam L for reading or writing enters from the surface on the side of the transmissive sheet 4.

Here, considering the thickness of the transparent sheet 4 and the substrate 12, the thickness of the substrate having a recording capacity of 15 GB is about 0.3 mm as described in the prior art, and It is difficult to form by a conventional injection molding method. On the other hand, considering the total thickness of the high-density optical disk, it is estimated to be 1.2 mm, which is the same as CD and DVD from the handling. Therefore, as an embodiment of a next-generation high-density optical disk, for example, if the thickness of the incident layer is assumed to be 0.3 mm, 0.9%
The information signal-containing substrate 12 having a thickness of 1 mm is formed by an injection molding method or the like, a reflective film 18 is formed on the information surface, and a transparent sheet 4 is further adhered thereon with a transparent adhesive, and laser light is incident. Is performed from the transparent sheet 4 side. When the density is further increased and the thickness of the transparent sheet 4 becomes 0.1 mm, the substrate 12 containing the information signal becomes 1.1 mm. That is, the thickness of the transparent sheet 4 is smaller than that of the substrate 12 containing the information signal.
In the above embodiment, the optical disk is a read-only type (R
OM type), but the present invention is not limited to this, and can be applied to, for example, write-once, rewritable, and magneto-optical disks.

Next, the evaluation was performed by variously changing the optical disk using the transparent sheet material according to the present invention and the optical disk using the same, and the evaluation results will be described. <Example 1> First, a polycarbonate sheet was formed as a transparent sheet 4 to a thickness of 100 µm, and an adhesive mainly composed of an acrylic material was used as an adhesive 6 on both surfaces thereof at a thickness of 10 µm.
The protective sheet 8 was made of a polyester sheet having a thickness of 50 μm. From this sheet 2, a disk-shaped sheet having the same dimensions as the substrate 12, that is, an outer diameter of 120 mm and an inner diameter of 15 mm, is cut, and the protective sheets 8 on both sides are peeled off to take out the transparent sheet 4.

On the other hand, a substrate 12 having an outer diameter of 120 mm, an inner diameter of 15 mm, and a thickness of 1.1 mm containing information signals such as pits 16 is prepared by injection molding, and an aluminum reflective film is formed on the information surface of the substrate 12. 18 was formed to a thickness of 60 nm by sputtering. The disc-shaped transparent sheet 4 manufactured above is placed on the reflective film 18 of the substrate 12 via an ultraviolet-curable adhesive (not shown), and the excess ultraviolet-curable adhesive is removed by rotating the transparent sheet 4. At the same time, the substrate 12 and the transparent sheet 4 are bonded together, and ultraviolet light is irradiated from the transparent sheet 4 side to harden the ultraviolet curable resin.
I got At this time, the thickness of the adhesive layer 14 formed by the hardening of the adhesive was about 5 μm. The surface of the transparent sheet 4 of the optical disk D thus formed was observed with a microscope, and no indentation or scratch was found. It is more preferable from the standpoint of dust control if an ionizer is applied to the surface of the permeable sheet 4 after the protective sheet 8 is peeled off so that the sheet 4 is not dusted by charging.

<Embodiments 2 and 3> FIG.
The thickness of the pressure-sensitive adhesive 6 was set to 10 μm in the roll-shaped permeable sheet material 2 described above. In Examples 2 and 3, the thickness was set to 5 μm and 15 μm, respectively. An optical disk was produced using the transparent sheet 4 of each raw material in the same manner as in Example 1, and the sheet surface was observed. As a result, the thickness of the adhesive is 5
Indentations and abrasions were slightly observed in the μm permeable sheet (Example 2), but were not observed in the 15 μm thick adhesive sheet (Example 3). Therefore, in combination with the results of Example 1, it was found that setting the thickness of the permeable sheet 4 to 10 μm or more hardly caused these indentations and scratches, which proved to be more preferable. The hardness of the pressure-sensitive adhesive 6 and the permeable sheet 4 used for the permeable sheet 2 was also examined here, and the evaluation results will be described. First, at the time of evaluation of the hardness, a needle having an outer diameter of 0.2 mm and a conical tip was attached to each measurement object (adhesives A to D, polycarbonate sheet).
The needle was pressed with a load of g to check the degree of entry of the needle. The result is shown in FIG. In the pressure-sensitive adhesives A to C, the needle penetrated deeper than the polycarbonate sheet (permeable sheet), but the pressure-sensitive adhesive D cured by the aging of the pressure-sensitive adhesive A was equivalent to the polycarbonate sheet. At this time, the thickness of all the measured objects was 0.1 mm.

A roll-shaped sheet material as shown in FIG. 1 was prepared by using the four types of adhesives A to D with a thickness of 10 μm, and an optical disk was produced from the sheet material in the same manner as in Example 1. And the sheet surface was observed. As a result, no dents and scratches were found on the permeable sheet surface of the optical discs of the adhesives A to C, but some dents and scratches were found on the permeable sheet surface of the optical disc of the adhesive D. As a result, it was found that the use of an adhesive softer than the permeable sheet 4 can further improve the effect of preventing indentation and abrasion. The form of the transparent sheet material of the present invention is such that an information signal is formed on the transparent sheet by a 2P method or the like, a reflective film is formed on the information signal surface, and the information signal surface side is inward. It goes without saying that the present invention can be applied to a method for manufacturing another high-density optical disk bonded to a polycarbonate substrate or the like. In this embodiment, the transparent sheet is immediately pasted on the reflective film. However, a protective film such as an ultraviolet curable resin may be applied on the reflective film for the purpose of protecting information signals from the manufacturing process.

[0016]

As described above, according to the transparent sheet material for optical information recording media and the optical information recording medium of the present invention, the following excellent operational effects can be exhibited.
By attaching a protective sheet to both surfaces of the permeable sheet via an adhesive, it is possible to prevent the permeable sheet itself from being indented or scratched. Further, by using such a transmissive sheet as an incident surface layer of an optical information recording medium, it is possible to maintain a high recording density and a high quality of a reproduced signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which an original transparent sheet for an optical information recording medium according to the present invention is wound in a roll shape.

FIG. 2 is an enlarged view showing a portion A in FIG.

FIG. 3 is a diagram showing a state in which a protective sheet is peeled off from a raw material of a transparent seal.

FIG. 4 is a cross-sectional view showing an optical disc formed by bonding a transparent sheet to a substrate.

FIG. 5 is a diagram showing the results of an evaluation performed on the hardness of a pressure-sensitive adhesive and a permeable sheet used for a permeable sheet.

[Explanation of symbols]

2 ... Transparent sheet raw material, 4 ... Transparent sheet, 6 ... Adhesive, 8 ... Protective sheet, 10 ... Dust, 12 ... Substrate, 14 ... Adhesive layer, 16 ... Pit, 18 ... Reflection film, D ... Optical disk ( Optical information recording medium).

Claims (2)

[Claims] 1. A transparent sheet material for an optical information recording medium, wherein protective sheets are stuck on both sides of a transparent sheet via an adhesive. 2. The method according to claim 1, further comprising: attaching the protective sheets on both sides of the transparent sheet on the information surface side of the substrate on which the information surface is formed, by applying a protective sheet to both sides of the transparent sheet via an adhesive. An optical information recording medium, wherein the transparent sheet taken out by being integrally peeled off with an agent is joined.