JPH0652586A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide an optical recording medium having high reliability which can perform a normal function even in the case of using for a long period. CONSTITUTION:An optical recording medium comprises a protective layer 11 provided at an opposite side to a transparent board of an optical recording medium board 12 to be laminated with a functional layer on the board through an adhesive layer 13, wherein the layer 13 is formed of acrylic resin, the layer 11 is formed of polyvinylidene chloride resin, and a thickness of the layer 11 is 1-100mum.

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 for recording, reproducing and erasing information with a light beam. More specifically, it relates to a magneto-optical recording medium suitable for a magnetic field modulation method.

[0002]

2. Description of the Related Art As an optical recording medium for recording, reproducing and erasing information by a light beam, a magneto-optical recording medium is widely known and various structures have been proposed so far. The general structure is as follows. That is, one or several kinds of inorganic dielectrics typified by Si ₃ N ₄ , SiO _x , ZnS, SiC, etc. by a method such as vacuum deposition and sputtering on a resin substrate having a preformatted signal such as a guide groove. A dielectric film made of a combination of GdTb, TbFe, and GdTbF is formed on the dielectric film.
e, an amorphous magneto-optical recording film such as TbFeCo, GdTbFeCo, etc. is provided, a dielectric film similar to the above-mentioned inorganic dielectric film is formed on it, and an ultraviolet curable resin is further applied on it. , To form a mechanical protective film.

[0003]

However, the conventional optical recording medium has a low environmental resistance, for example, in a high temperature and high humidity environment (eg, temperature 80 ° C., humidity 90%) for a long time (eg, 2000). If it is left for a long time, the magneto-optical recording film will be corroded and the recording, reproducing and erasing functions will be abnormal, resulting in low reliability in long-term use.

For example, in the magneto-optical recording medium having the above-mentioned structure, since the rare earth-transition metal amorphous alloy forming the recording layer is chemically extremely active, the inorganic protective film such as nitride is used as described above. It has a sandwich structure and is further coated with an organic polymer film as a protective layer. However, water absorption,
It is difficult to completely prevent oxidative corrosion of the magneto-optical recording film due to moisture permeation or the like.

Further, when an ultraviolet curable resin is applied and cured by a spin coater or the like to form a protective layer, projections of a level of 1 to several tens of μm are generated on the surface of the protective layer due to the splash of liquid and the influence of dust. Since the distance between the magnetic field modulation head and the protective layer is generally 1 to 2 μm, a head crash occurs between the magnetic field modulation head and the magneto-optical recording medium, or the magnetic field modulation head sticks to the magneto-optical recording medium. There is also a problem to do.

Therefore, in view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a highly reliable optical recording medium that normally functions even when used for a long period of time. In particular, it is an object of the present invention to provide a highly reliable magneto-optical recording medium suitable for the magnetic field modulation method.

[0007]

The present invention for achieving the above object provides an optical recording medium having a recording layer on a substrate and a protective layer formed on the recording layer via an adhesive layer. The adhesive layer contains an acrylic resin, the protective layer contains a polyvinylidene chloride resin, and the protective layer has a thickness of 1 to 1.
The optical recording medium is characterized by having a thickness of 00 μm.

According to the present invention, in the above recording medium, the optical recording medium substrate is a transparent substrate, a first dielectric layer, a recording layer,
The second dielectric layer and the reflective layer are sequentially laminated.

Further, according to the present invention, a first dielectric layer made of a transparent dielectric film, a recording layer made of a rare earth-transition metal amorphous alloy thin film, and a second dielectric layer made of a transparent dielectric film are sequentially laminated on a transparent substrate. Formed on the second dielectric layer of the optical recording medium substrate with an adhesive layer, and having a thickness of 5 μm of an ultraviolet curable resin film.
An optical recording medium is provided with a protective layer of 30 μm.

Further, according to the present invention, a first dielectric layer made of a transparent dielectric film, a recording layer made of a rare earth-transition metal amorphous alloy thin film, a second dielectric layer made of a transparent dielectric film, and a reflective layer are formed on a transparent substrate. On the reflective layer of the optical recording medium substrate, which is formed by sequentially stacking
An optical recording medium is provided with a protective layer having a thickness of 30 μm to 30 μm.

Further, according to the present invention, the ultraviolet curable resin film forming the protective layer having a thickness of 5 μm to 30 μm is a cured film of a composition containing 80% by weight or more of a monomer having 5 to 6 functional groups. , The surface of the protective layer is matted, the surface of the protective layer has an antistatic function, the surface of the protective layer has a lubricating function, and / or the protective layer has a filler. It includes what is contained.

The present invention will be described in detail below.

FIG. 1 is a schematic sectional view showing one structural example of the optical recording medium of the first present invention. In the figure, 11 is a protective layer made of polyvinylidene chloride resin, 12 is an adhesive layer made of acrylic resin, and 13 is an optical recording medium substrate.

As the polyvinylidene chloride resin, polyvinylidene chloride, polyvinyl chloride-polyvinylidene chloride copolymer and the like can be used, and these are preferably used in the form of a film. Furthermore, when used as a film,
An adhesive to which adhesive is applied in advance to impart adhesiveness, or a semi-cured adhesive having self-adhesiveness is preferable.

The thickness of the protective layer is 1 μm to 100 μm, preferably 4 μm to 20 μm. This is because if the thickness of the protective layer is 4 μm or less, there is no effect of preventing scratches, and if it is 20 μm or more, the distance between the magnetic head and the recording layer becomes large, and sufficient magnetic field strength cannot be obtained.

As the acrylic resin, polyacrylic acid, polyacrylic acid ester or the like can be used, and in particular, an acrylic acid-acrylic acid ester copolymer obtained by mixing a small amount of acrylic acid with acrylic acid and copolymerizing preferable. These resins may be applied in advance to the polyvinylidene chloride resin film or applied to the optical recording medium substrate.

The thickness of the adhesive layer is not particularly limited, but is preferably 1 μm to 10 μm, particularly preferably 2 μm.
μm to 8 μm.

In the present invention, an ordinary optical recording medium substrate can be used, and the laminated structure of each functional layer such as a dielectric layer, a recording layer and a reflective layer is not particularly limited, but is transparent. A layer formed by sequentially stacking a first dielectric layer, a recording layer, a second dielectric layer and a reflective layer on a substrate is preferably used.

Next, the second optical recording medium of the present invention will be described.

The protective layer formed of the ultraviolet curable resin has a layer thickness of 5 to 30 μm, but if the layer thickness is less than 5 μm, it becomes difficult to bond it to the optical recording medium substrate. .

The UV-curable resin used here includes polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate and the like. In particular, those having a monomer having 5 to 6 or more functional groups are suitably used because they have a high crosslinking density and a low moisture permeability. Further, those containing 80% by weight or more of a monomer having 5 to 6 functional groups are remarkable in the above effect, and at this time, the surface hardness of the protective layer is pencil hardness H or more.

Further, the protective layer is preferably in a so-called matted state in which the surface is appropriately roughened to prevent sticking to the magnetic field modulation head. Due to this matting, the surface roughness of the protective layer is 0.3 μm higher than the height of the surface protrusions.
It is preferably m or less.

Further, this protective layer is provided with an antistatic function to prevent head crush with the magnetic field modulation head. As a method of imparting an antistatic function, a method of forming a protective layer with an ultraviolet curable resin mixed with an antistatic agent is preferable. As the antistatic agent, an anionic surfactant, a cationic surfactant, a nonionic surfactant, a conductive resin, a conductive metal fine powder, a conductive metal oxide or the like can be used. Further, in order to prevent a head crash with the magnetic field modulation head, it is preferable that the protective layer is coated or impregnated with a lubricant. As the lubricant, triacontyltrimethoxysilane, perfluoropolyether or the like can be used.

Further, it is preferable that the protective layer contains a filler in order to prevent sticking to the magnetic field modulation head and head crush. As the filler, inorganic fine particles such as calcium carbonate and alumina, and plastic powder such as polyethylene, polypropylene, silicone resin and methacrylic acid resin can be used. The particle size of the filler is preferably 0.01 to 20 μm, particularly preferably 0.5 to 10 μm.

Further, in the present invention, the first and second dielectric layers are dielectrics made of one kind or a combination of several kinds of inorganic dielectrics typified by Si ₃ N ₄ , SiO _x , ZnS, SiC and the like. It is a film. These dielectric layers need to be transparent.

The recording layer is made of GdTb, TbFe, GdT.
An amorphous magneto-optical recording film of bFe, TbFeCo, GdTbFeCo, or the like.

Now, a preferred method for producing the second optical recording medium of the present invention will be described.

FIG. 3 is a conceptual diagram showing an example of steps for forming a protective layer of the optical recording medium of the present invention. On the optical recording medium substrate 31, a protective layer 32 made of an ultraviolet curable resin film cured on a support 33 is laminated. After pressing this with a roller or the like, the support 33 is peeled off from the main body, and the protective layer 32 is formed on the optical recording medium substrate 31. At this time, the optical recording medium substrate 31 is, as shown in FIG.
The second dielectric layer 44, the recording layer 43, the first dielectric layer 42, and the transparent substrate 41 are formed. Further, FIG. 5 shows a preferred example of the protective layer-providing sheet for easily forming the protective layer on the reflective layer of the recording medium. The protective layer application sheet 50 is made of PE
A release layer 51, a protective layer 32 made of an ultraviolet curable resin film, and an adhesive layer 52 are sequentially laminated on a support 33 such as T,
After the adhesive layer 52 is overlaid on the reflection layer 45 of the optical recording medium 31 and pressure-bonded thereto, the support 33 is peeled off together with the release layer 51, and the protective layer 32 is transferred onto the optical recording medium substrate 31. If the optical recording medium substrate 31 does not employ the reflective layer 45, the second
The protective layer 32 can be similarly formed by stacking the adhesive layer 52 on the dielectric layer 44. Further, in the present invention, as the release layer 51, for example, a polymer film such as a PET film, a PE film and a PP film whose surface is treated with silicon or fluorine can be used, and the adhesive layer 52 is generally used in this field. Adhesive layers can be used.

By the manufacturing method as described above, the protective layer made of the ultraviolet curable resin film can be easily formed on the optical recording medium substrate.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples. The Irgacure 184 used in this example is a curing agent manufactured by Nippon Ciba Geigy Co., Ltd.

Example 1 An optical recording medium as shown in FIG. 1 was produced as follows. First, a polyvinylidene chloride film 8 μm was prepared as the protective layer 11, and the polyvinylidene chloride film 8 μm was placed on the optical recording medium substrate 13 via the adhesive layer 13 made of a solvent-type acrylic resin (trade name Acryft R-17, manufactured by Sumitomo Chemical Co., Ltd.) Then, pressure bonding was performed to manufacture an optical recording medium. At this time, the thickness of the adhesive layer is 2
μm.

FIG. 2 shows the layer structure of the optical recording medium substrate used in this example. This laminated body was manufactured as follows.

On a transparent substrate 21 having guide grooves and signal pits formed thereon, an S film having a film thickness of 1000 Å was formed by a sputtering method.
A dielectric layer 22 made of an i ₃ N ₄ film is formed, and then a film thickness of 2
Magneto-optical recording layer 2 made of an amorphous TbFeCo film of 00Å
3 was further provided, a dielectric layer 24 made of a Si ₃ N ₄ film having a film thickness of 400 Å was further provided, and a reflective layer 25 made of an Al-Cr film having a film thickness of 600 Å was further formed.

Example 2 Instead of the solvent-type acrylic resin used in Example 1, an acrylic acid-acrylic acid ester resin (trade name: Nucrel,
An optical recording medium was prepared in the same manner as in Example 1 except that Mitsui DuPont Polychemical Co., Ltd.) was used as the adhesive layer.

Example 3 An optical recording medium was prepared in the same manner as in Example 1 except that a polyvinyl chloride-polyvinylidene chloride copolymer film was used as a protective layer instead of the polyvinylidene chloride film used in Example 1. did.

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1 except that a polyester film was used instead of the polyvinylidene chloride film used in Example 1.

Comparative Example 2 An optical recording medium was prepared in the same manner as in Example 1 except that an ethylene-vinyl acetate copolymer (EVA) resin was used as an adhesive layer instead of the solvent-type acrylic resin used in Example 1. It was made.

Comparative Example 3 Optical recording was performed in the same manner as in Example 1 except that a polyester adhesive (trade name: Chemit R-188, manufactured by Toray Industries, Inc.) was used in place of the solvent-type acrylic resin used in Example 1. A medium was prepared.

Example 4 <Environmental Durability Test> The optical recording media prepared in Examples 1 to 3 and Comparative Examples 1 to 20 were subjected to an environment of temperature 80 ° C. and humidity 90% for 20 times.
The environment durability was examined after 00 hours. Table 1 shows the bit error rate before and after the environmental durability test (hereinafter, BE.
R. Value) is shown. B. E. R. The measurement was conducted on the optical recording medium before the start of the test and after 2000 hours, under normal temperature and normal humidity. The optical recording media of Examples 1 to 3 did not corrode even after 2000 hours of the durability test, and as shown in Table 1, B. E. R. No change over time was observed. On the other hand, in the optical recording media of Comparative Examples 1 to 3, corrosion was confirmed after the durability test, and as shown in Table 1, B.I. E. R. Has greatly increased.

[0040]

[Table 1] Example 5 <Release layer forming liquid> Acrylic polyol 50 parts Isocyanate 20 parts Silica 5 parts Toluene 100 parts <Protective layer forming UV curable resin composition> 5-functional acrylate 30% by weight 6-functional acrylate 50% by weight Dicyclopentadiene Diacrylate 15% by weight Irgacure 184 5% by weight <Adhesive layer forming liquid> Ethylene-acrylic acid ester copolymer 25 parts Methanol 50 parts Water 40 parts A polyethylene terephthalate film having a thickness of 70 μm biaxially stretched with a release layer forming liquid. It was coated on one side with a Meyer bar and dried at 100 ° C. to form a release layer having a thickness of about 2 μm.

Then, a UV-curable resin composition for forming a protective layer is applied thereon to a thickness of 10 μm, and UV is applied.
A protective layer was obtained by irradiating light and curing. Further, an adhesive layer forming liquid is applied thereon so as to have a thickness of 2 μm, and 100
A protective layer-provided sheet having an adhesive layer laminated thereon was obtained by drying at 0 ° C.

On the other hand, amorphous TbF is used as the magneto-optical recording layer.
An optical recording medium substrate was prepared in the same manner as in Example 1 except that the eCoCr film was used.

The uppermost layer of this optical recording medium substrate, Al-
The adhesive layer of the protective layer-providing sheet was overlaid on the Cr layer, pressed by a roller, and then the release layer of the protective layer-providing sheet was peeled off together with the PET film as the support to obtain the optical recording medium of the present invention. According to this method, the protective layer can be easily transferred onto the Al-Cr layer.

Example 6 <UV-Curable Resin Composition for Forming Protective Layer> 5-functional acrylate 40% by weight 6-functional acrylate 45% by weight Trimethylol propane triacrylate 10% by weight Irgacure 184 5% by weight UV-curable resin composition An optical recording medium was produced in the same manner as in Example 5 except that the composition was changed as described above.

Example 7 <UV curable resin composition for forming a protective layer> 5-functional acrylate 40% by weight 6-functional acrylate 40% by weight Dicyclopentadiene acrylate 15% by weight Irgacure 184 5% by weight Lubricant ( An optical recording medium was produced in the same manner as in Example 5 except that the ultraviolet curable resin composition containing 0.5% by weight of (perfluoropolyether) was used.

Example 8 <UV-Curable Resin Composition for Forming Protective Layer> 5 functional acrylate 40% by weight 6 functional acrylate 45% by weight Trimethylol propane triacrylate 10% by weight Irgacure 184 5% by weight Conductive resin in the above composition An optical recording medium was produced in the same manner as in Example 5 except that an ultraviolet curable resin containing 10% by weight of (trade name STH-87, manufactured by Mitsubishi Yuka Fine Co., Ltd.) was used.

Example 9 <UV curable resin composition for forming protective layer> 5-functional acrylate 40% by weight 6-functional acrylate 45% by weight Dicyclopentadiene acrylate 10% by weight Irgacure 184 5% by weight Alumina filler was added to the above composition. An optical recording medium was prepared in the same manner as in Example 5 except that the ultraviolet curable resin blended in 20% by weight was used.

Comparative Example 4 <UV-Curable Resin Composition for Protective Layer Formation> Bifunctional acrylate 60% by weight Dicyclopentadiene monoacrylate 35% by weight Darocur 1173 (manufactured by Merck Ltd.) 5% by weight Photoinitiator As a comparative example An optical recording medium was prepared in the same manner as in Example 5 except that the above ultraviolet curable resin composition was used.

Example 10 <Environmental endurance test> The environmental endurance test of the optical recording media prepared in Examples 5 to 9 and Comparative Example 4 was carried out in the same manner as in Example 4.
The results are shown in Fig. 6. In the figure, the vertical axis represents B.I. E. R.
The horizontal axis represents the standing time in an environment of temperature 80 ° C. and humidity 90%. In addition, white circles indicate changes in the example, and black triangles indicate changes in the comparative example. As can be seen from the figure, the optical recording media of Examples 5 to 9 had the same B.I. E. R. There is no change in the value of B., and the optical recording medium of Comparative Example 4 has a B.E. E. R. Has increased.

Therefore, it can be seen that the optical recording medium of the present invention has less corrosion than the conventional one and has improved reliability. <Sliding resistance test> FIG. 7 shows the results of evaluating the sliding resistance of the above recording medium by a pin-on-disk test (wear test). In the figure, the vertical axis represents the frictional force, the horizontal axis represents the number of times of contact, the white circles represent the changes of each recording medium of the example, and the black triangles represent the changes of the respective recording media of the comparative example. As can be seen from the figure, the optical recording medium of the embodiment is
While the frictional force hardly changed with time, the optical recording medium of the comparative example increased the frictional force exponentially. This is because in the medium of the comparative example, since the surface roughness of the protective layer is large, the frictional force is originally large, and the surface roughness is further deteriorated while being worn, so that the frictional force is large. It is considered to be.

[0051]

As described above, according to the present invention, by adopting the acrylic resin as the adhesive layer and the polyvinylidene chloride resin as the protective layer, the present invention does not corrode even under a high temperature and high humidity environment and can be used for a long period of time. It is possible to provide a stable optical recording medium.

In addition, the optical recording medium of the present invention protects the recording medium with an ultraviolet curable resin and improves its surface property to (1) prevent the corrosion of the recording layer, thereby improving the long-term reliability of the optical recording medium. Is improved, (2) it is easy to control the surface roughness of the protective layer, (3) the protective layer has high hardness and lubricity,
Since it has an antistatic function, it has an effect of preventing head crash and improving sliding resistance.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a basic configuration example of an optical recording medium of the present invention.

FIG. 2 is a cross-sectional view showing one structural example of an optical recording medium substrate according to the present invention.

FIG. 3 is a process drawing showing a method of forming a protective layer on a magneto-optical recording medium substrate of the present invention.

FIG. 4 is a sectional view showing a layer structure of a magneto-optical recording medium substrate according to the present invention.

FIG. 5 is a cross-sectional view showing a constitution of a protective layer-provided sheet preferable in the present invention.

FIG. 6 is a graph showing the results of an environmental durability test of a magneto-optical recording medium.

FIG. 7 is a graph showing the results of a sliding resistance test of a magneto-optical recording medium.

[Explanation of symbols]

 11 Protective Layer 12 Adhesive Layer 13 Optical Recording Medium Substrate 21 Transparent Substrate 22 First Dielectric Layer 23 Recording Layer 24 Second Dielectric Layer 25 Reflective Layer 31 Optical Recording Medium Substrate 32 Protective Layer 33 Support 41 Transparent Substrate 42 First Dielectric Body layer 43 Recording layer 44 Second dielectric layer 45 Reflective layer 50 Protective layer imparting sheet 51 Release layer 52 Adhesive layer

Claims (9)

[Claims] 1. An optical recording medium comprising a recording layer on a substrate, and a protective layer formed on the recording layer via an adhesive layer, wherein the adhesive layer contains an acrylic resin, and the protective layer. Contains a polyvinylidene chloride resin, and the protective layer has a thickness of 1 to 100 μm. 2. The optical recording medium according to claim 1, wherein the optical recording medium substrate is formed by sequentially laminating a first dielectric layer, a recording layer, a second dielectric layer and a reflective layer on a transparent substrate. 3. A first dielectric layer made of a transparent dielectric film, a recording layer made of a rare earth-transition metal amorphous alloy thin film, and a second dielectric layer made of a transparent dielectric film are sequentially laminated on a transparent substrate. An optical recording medium comprising a second dielectric layer of an optical recording medium substrate, and a protective layer made of an ultraviolet curable resin film having a thickness of 5 to 30 μm provided on the second dielectric layer via an adhesive layer. 4. A first dielectric layer made of a transparent dielectric film, a recording layer made of a rare earth-transition metal amorphous alloy thin film, a second dielectric layer made of a transparent dielectric film, and a reflective layer are sequentially laminated on a transparent substrate. An optical recording medium having a protective layer of 5-30 μm in thickness made of an ultraviolet-curable resin film provided on the reflective layer of the optical recording medium substrate via an adhesive layer. 5. The optical recording according to claim 3, wherein the ultraviolet curable resin film forming the protective layer is a cured film of a composition containing 80% by weight or more of a monomer having 5 to 6 functional groups. Medium. 6. The optical recording medium according to claim 3, wherein the surface of the protective layer is matted. 7. The optical recording medium according to claim 3, wherein the surface of the protective layer has an antistatic function. 8. The optical recording medium according to claim 3, wherein the surface of the protective layer has a lubricating function. 9. The optical recording medium according to claim 3, wherein the protective layer contains a filler.