JPH07130005A - Optical recording medium and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Construction] In an optical recording medium comprising a vacuum film-forming layer comprising at least a recording layer on an optically transparent substrate and an organic protective layer thereon, preferably the organic compound comprising an ultraviolet curable resin is used. The protective layer is divided into two or more layers, and if necessary, a filler is dispersed in the uppermost layer of the organic protective layer, and each layer has a different function. [Effect] Since the step of the convex portion that may be present on the vacuum film-forming layer can be gradually made gentle with the stacking of the organic protective layer, the appearance of the medium due to foreign substances mixed during the formation of the vacuum film-forming layer. The defects can be significantly reduced, and the functions of the organic protective layer can be further enhanced by sharing the different functions among the layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to recording with a laser,
The present invention relates to a rewritable and erasable optical recording medium, and in particular, has a structure that is effective in preventing appearance defects by reducing convex steps appearing on the surface of the organic protective layer due to foreign substances mixed in during formation of the recording layer. The present invention relates to an optical recording medium and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, rewritable magneto-optical disks have been put on the market and are being applied as data files for computer code information and images.

In these disks, a rare earth-transition metal amorphous magnetic layer which is a recording layer, a dielectric protective layer for protecting it, a metal heat dissipation layer, etc. are formed on a clean substrate made of glass or plastic by sputtering or the like. Further, a single-layer organic protective layer is coated on these vacuum film-forming layers.

By the way, these discs are manufactured in a clean room having a high degree of cleanliness so as not to cause defects. However, no matter how careful the disc is manufactured, the film adhered to the inside of the film forming apparatus is peeled off in the process of forming the vacuum film forming layer and adheres to the disc during the film formation. Even if the defects due to the film pieces are of a level that does not pose a problem in recording / reproducing, if alternate sector processing or ECC is applied, if an organic protective layer is coated thereon by using a spinner, the defects are amplified and the convex appearance is defective. This is a cause of lowering the manufacturing yield.

As described above, in the case of the conventional single-layer organic protective layer, if a film piece adheres to the substrate during vacuum film formation, it becomes visible after the organic protective layer is coated unless the film piece is so small. As shown in FIG. 2, the surface of the organic protective layer was projected in a convex shape, resulting in poor appearance.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, the present invention provides a specific structure for an organic protective layer provided on a vacuum film-forming layer so that the organic protective layer can be attached to a medium before the organic protective layer is formed. The purpose of the present invention is to significantly reduce the occurrence of convex appearance defects that appear on the surface of the organic protective layer due to the foreign substances, and further improve the performance of the organic protective layer comprehensively.

Another object of the present invention is to efficiently form the above specific organic protective layer.

[0008]

Means for Solving the Problems (and Action) The present invention which achieves the above object is provided with a vacuum film-forming layer comprising at least a recording layer on an optically transparent substrate and an optical protective layer thereon. The recording medium is an optical recording medium characterized in that the organic protective layer is divided into two or more layers. By providing the organic protective film formed in two or more layers on the vacuum film-forming layer, the steps of the convex portions that may be present on the vacuum film-forming layer are gradually graded as the organic protective layer is laminated. Therefore, it is possible to significantly reduce the appearance defect of the medium due to the foreign substances mixed in during the formation of the vacuum film formation layer.

Further, the present invention is the above optical recording medium, wherein the hardness of the uppermost layer of the organic protective layer is higher than the hardness of the lowermost protective layer. Since the organic protective layer is composed of two or more layers, if a material having a relatively low hardness is used for the lowermost layer, it cannot be used for the uppermost layer because of its high hardness but poor adhesion. Since a material can be used, a medium having a high hardness that has never been obtained can be obtained.

The present invention is also the optical recording medium of any one of the above, wherein a filler is dispersed in the uppermost layer of the organic protective layer. By dispersing the filler in the uppermost layer, an uneven shape can be formed on the surface of the uppermost layer, so that even if there is a convex portion on the surface, it can be prevented from becoming visible to the extent that it can be identified. As a result, appearance defects can be reduced and the yield can be further improved.

Further, the present invention is the optical recording medium according to any one of the above, wherein the organic protective layer is an ultraviolet curable resin. By using the organic protective layer, curing can be performed for a short time, so that two or more organic protective layers can be continuously formed, and work efficiency can be improved.

The present invention is also the optical recording medium according to any one of the above optical recording media, wherein the organic protective layer is formed by a spinner. By forming the organic protective layer with the spinner, the protective layer can be formed without unevenness in the thickness in the circumferential direction, so that stable recording and reproduction without center of gravity deviation can be performed.

The present invention is also the optical recording medium of any one of the above, wherein the optical recording medium is a magneto-optical recording medium. With the above-mentioned optical recording medium structure, in particular, the structure in which the hardness of the uppermost layer is increased or the filler is dispersed, the scratches by the magnetic head and the adsorption to the magnetic head are reduced when the medium is used for the magnetic field modulation recording method. Therefore, stable floating of the recording medium can be achieved.

Further, according to the present invention, in the production of an optical recording medium in which a vacuum film-forming layer composed of at least a recording layer and an organic protective layer thereon are provided on an optically transparent substrate, two organic protective layers are provided. It is a method of manufacturing an optical recording medium, characterized in that a step on the outer surface of the optical recording medium is reduced by applying the coating separately in the above manner. By sequentially coating one organic protective layer including two or more layers, an optical recording medium having the above-described effects can be easily manufactured.

The present invention will be described in detail below.

The optical recording medium according to the present invention basically has a structure in which a vacuum film-forming layer including a recording layer and an organic protective layer are provided on a transparent substrate, and foreign matter is mixed during the formation of the vacuum film-forming layer. Any foreign matter is possible as long as the foreign matter can be manifested as a poor appearance after the formation of the organic protective layer. For example, a magneto-optical recording method, a phase transition recording method, W.
O. Examples thereof include optical recording media such as a system and a ROM system.

The feature of the present invention is that the organic protective layer is
By forming the film in layers or more, it is possible to reduce appearance defects due to film pieces attached to the substrate. The reason why the defective appearance is solved by such means will be described with reference to FIG. The substrate 5 peeled off from the inner wall of the film forming apparatus during film formation
On the surface of the convex portion 11 of the vacuum film forming layer formed on the uppermost heat dissipation layer 5 of the vacuum film forming layers 2 to 5 by the film piece 6 attached to the The first protective layer 7 is formed. At this time, the convex portions 12 on the surface of the first protective layer 7
Has a larger area than the convex portion 11 of the vacuum film forming layer, but has a lower height. Further, the second protective layer 8
When the layers are laminated, the convex portion further spreads in area, but the step is further reduced and becomes smooth. By stacking the organic protective layer in this manner, the convex portion on the surface of the organic protective layer gradually becomes gentle and finally becomes flat,
The appearance is not deteriorated, and the yield is not reduced even if the convex portions 11 of the vacuum film forming layer are formed. Further, even if the convex portion has a considerably large step, by increasing the number of layers of the organic protective layer, the step can be reduced to such an extent that it is not recognized as a defective appearance.

In the above case, in the case of the single-layer organic protective layer, the size of the convex defect appearing on the surface of the optical recording medium as a defective appearance is almost several μm to several tens μm, although it does not cause any problem in recording and reproducing. There is a step, and the size of the foreign matter that can cause the difference is approximately several tens of μm to several hundreds of μm.
It is a piece of film. If a foreign matter larger than this adheres to the substrate, it will hinder the recording and reproduction, and it will be removed as a defective product without causing a problem in appearance, so it is not necessary in the present invention. Even if the thickness of the organic protective layer is the same, by forming the layer with two or more layers, it is possible to reduce the level difference that causes poor appearance to the extent that it is almost unrecognizable.
As the number of layers increases by one, the level difference of the convex portion decreases to around 50%,
Further, since the low area of the convex portion is increased, there is a considerable effect only by increasing the number of layers by one. Here, the total thickness of the organic protective layer is preferably 5 to 40 μm, more preferably 7 to 40 μm.
It is formed in the range of 20 μm. If it is thinner than this, it becomes difficult to obtain the effect as a protective layer, and if it is thicker than this, the disc may warp. Particularly in the case of the magnetic field modulation recording method, if the thickness is too large, the strength of reaching the magnetic layer with respect to the strength of the magnetic field generated by the magnetic head is lowered, so that the thickness is preferably 20 μm or less. The number of layers is 2 or more, preferably 3 to 4
Although a layer is good, therefore, the thickness of one layer is about 2 to 10 μm,
The thickness is preferably about 3 to 5 μm, but may be appropriately selected depending on the size of foreign matter mixed in the vacuum film formation layer, the mixing frequency, the target yield, and the like. Further, if the number of layers is large, it is possible to cover even if the step of the convex portion is high, but the work efficiency is reduced, so the number of layers is appropriately selected. If there are two or more layers, there is no particular upper limit, but the total thickness is made too thick so that the disc does not warp.

As a method for forming the organic protective layer, a coating method using a spinner is preferable because it can form a uniform thickness on the disk, but other methods also have the above-mentioned effects. If it is good, it can be adopted.

The material and composition of each layer constituting the organic protective layer may be the same or different, and can be changed within the range such that the total performance such as color, hardness and surface roughness of each layer is not a problem. For example, each layer of the multi-layer organic protective film is provided with adhesion, hardness, especially in the magnetic field modulation recording method, each layer is responsible for the functions required for the protective film such as antistatic property, lubricity, surface roughness, etc. Total performance can be improved.

As the organic protective film used in the present invention, commercially available resins such as ultraviolet curable resins (epoxy acrylate, urethane acrylate, silicon acrylate, polyester acrylate, etc.), thermosetting resins (epoxy, urethane, silicone, etc.) Can be used
An ultraviolet curable resin that can be cured for a short time and has excellent workability because an organic protective film having two or more layers is continuously formed is particularly excellent.

Further, in order to increase the mechanical strength of the organic protective layer, if an organic protective layer is formed only by a material having a high surface hardness, a material having a high surface hardness generally has a large curing shrinkage rate and deteriorates with time. Since the organic protective film is peeled off or the vacuum-formed film is cracked, a material having a high hardness cannot be used conventionally. In such a case, at least the organic protective layer that is in contact with the vacuum film-forming layer should have a high hardness by making the recording layer of the vacuum film-forming layer soft and having a small curing shrinkage ratio even after curing. Since it can be used as the uppermost layer and the surface hardness of the organic protective layer can be improved, it is difficult to get scratches even if the magnetic head crashes, especially when used in a magnetic field modulation recording medium. You can

Further, by forming fine irregularities on the surface of the uppermost organic protective layer as shown in FIG. 3, the convex portions 12 on the surface of the organic protective layer are difficult to see, and the appearance is less likely to deteriorate.
Yield is further improved. As a method of making unevenness, alumina (Al ₂ O ₃ ), aluminum nitride (AlN), silicon carbide (SiC), silica (SiO ₂ ) is formed on the uppermost organic protective layer.
₂ ), boron nitride (BN), titanium oxide (TiO ₂ ),
Zirconium oxide (ZrO ₂ ), chromium oxide (Cr ₂ O
₃ ), fine particles of silicon nitride (Si ₃ N ₄ ) and the like (particle size of 0.5 to 2.0 μm) per 5 to the corresponding organic protective layer.
40 wt%, preferably 10 to 20 wt% is dispersed and coated to form irregularities having a step difference of 0.5 to 1.0 μm. The magneto-optical disk having fine irregularities on the surface thereof, particularly when used as a medium for the magnetic field modulation recording method, has a rough surface, which causes adsorption of the organic protective film and the slider for the magnetic head. Since it is eliminated, stable levitation can be achieved.

The above-mentioned multilayer organic protective layer can be formed by applying a known method. That is, each layer may be laminated in the same manner as when a single organic protective layer is formed. However, it is necessary to stack the layers so that the next layer is coated after being hardened to maintain the shape of the formed layer. Further, the viscosity of the molten resin for forming the organic protective layer may be appropriately adjusted based on the method of coating the single organic protective layer, such as lowering the viscosity than usual or increasing the rotation speed of the spinner.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Next, 200 optical disks having the structure shown in FIG. That is, Si ₃ is deposited on a polycarbonate substrate 1 having a diameter of 86 mm by using a sputtering device.
Base protection layer 2 of N ₄ , recording layer 3 of TbFeCo, Si ₃
The interference layer 4 of N ₄ and the reflective layer 5 of Al were sequentially formed.

Next, an ultraviolet curable resin (SD-101: manufactured by Dainippon Ink & Co., Inc.) was coated with a spinner to a thickness of 5 μm and cured to form a first protective layer 7. Then, by the same process, the second protective layer 8 and the third protective layer 9
Was formed to form an organic protective layer 10 composed of three layers and having a total thickness of 15 μm. Table 1 shows the results of evaluating the yield by conducting a convex appearance inspection on the surface of the organic protective layer. [Embodiment 2] The first protective layer has a thickness of 8 μm, the second protective layer has a thickness of 7 μm, and the total thickness of the two layers is 15 μm.
200 optical discs were prepared in the same manner as in Example 1 except that the organic protective layer of m was formed. Table 1 shows the results of evaluating the yield by conducting a convex appearance inspection on the surface of the organic protective layer. [Embodiment 3] Alumina filler 14 (average particle size 1.0 μm) is formed in the third protective layer so as to have the structure shown in FIG.
200 optical disks were prepared in the same manner as in Example 1 except that 20% by weight of m) was added to the third layer to form the protective layer 9 ′. The level difference of the unevenness formed on the surface of the third layer is about 0.8 μ.
It was about m. Table 1 shows the results of evaluating the yield by conducting a convex appearance inspection on the surface of the organic protective layer. In addition, a CSS test is carried out using a sample which is a non-defective product here (in the case of a magnetic field modulation recording method, a test method of an organic protective film in which a magnetic head is brought into contact with the medium surface when the disk medium is stopped and the head is floated at the start of rotation). ), The compatibility of the recording medium in magnetic field modulation recording was evaluated.
It was confirmed that there was no problem even if the operation was performed 10,000 times, and that it could be used as a medium of the magnetic field modulation recording system. [Example 4] 200 optical disks were prepared in the same manner as in Example 2 except that 20 wt% of the same alumina filler as in Example 3 was added to the second organic protective layer to form the organic protective layer. Table 1 shows the results of evaluating the yield by conducting a convex appearance inspection on the surface of the organic protective layer. Comparative Example 1 200 optical disks were prepared in the same manner as in Example 1 except that the organic protective layer 13 was formed of only one layer so as to have the structure shown in FIG. Table 1 shows the results of evaluating the yield by conducting a convex appearance inspection on the surface of the organic protective layer.

As shown in Table 1, it can be seen that the optical discs obtained in each of the above-mentioned embodiments have a reduced appearance defect and an improved yield, as compared with the conventional recording medium (Comparative Example 1). The yield of the organic protective layer was evaluated by visually observing a defect in the convexity on the surface of the organic protective layer using a condenser lamp.

[0028]

[Table 1] [Example 5] For the first protective layer of Example 2, a material having a pencil hardness of B after curing and having a good adhesion to Al of the reflective layer (SDS-101: manufactured by Dainippon Ink and Chemicals, Inc.) ) Is used for the second protective layer, the pencil hardness is H and the hardness is A.
A sample was prepared by forming an organic protective layer in the same manner as in Example 2 except that a material (MH-7508: manufactured by Mitsubishi Rayon) having poor adhesion to 1 was used. In this case as well, it is possible to achieve the original purpose of improving the appearance yield, and it becomes possible to use a material that could not be used because of its poor adhesion to Al in the past, and the selection range of materials expands. It was possible to form a hard and strong protective film.

In addition to the above, in order to provide the antistatic property and lubricity required for the magnetic field modulation recording system, in the structure of the organic protective film of Example 1, the first layer is SDS-101 and the second layer is SDS-.
When OD-3 (manufactured by Nippon Kayaku Co., Ltd.) was used as the 101st and 3rd layers to manufacture an optical disk in the same manner, the appearance yield was similarly improved, and a magnetic field modulation recording system was obtained. Further, as a recording medium other than magneto-optical, phase transition and W. O. When the same organic protective layer was formed on the recording medium according to 1., the same effect was obtained.

[0030]

As described above, 2 is formed on the vacuum film-forming layer.
By providing the organic protective film divided into layers or more, the step of the convex portion that may be present on the vacuum film-forming layer can be gradually smoothed as the organic protective layer is laminated, so that a vacuum is formed. It is possible to significantly reduce the appearance defect of the medium due to the foreign substances mixed in during the formation of the film formation layer.

Further, since the organic protective layer is composed of two or more layers, if a material having a relatively low hardness is used for the lowermost layer, the uppermost layer is conventionally hard but has poor adhesion. Since it is possible to use a material that cannot be used for the above, it is possible to obtain a medium having a high hardness that has never been obtained.

Further, by dispersing the filler in the uppermost layer, the surface of the uppermost layer can be provided with an uneven shape, so that even if there is a convex portion on the surface, it can be made visible to the extent that it can be identified. This can be prevented, and as a result, defective appearance can be reduced and the yield can be further improved.

Further, by using the ultraviolet curable resin, it is possible to cure for a short time, so that two or more organic protective layers can be continuously formed, and the work efficiency can be improved.

Further, since the organic protective layer is formed by the spinner, the protective layer can be formed without unevenness in the thickness in the circumferential direction, so that stable recording and reproduction without deviation of the center of gravity becomes possible.

Further, in the above-mentioned optical recording medium structure, in particular, in the structure in which the hardness of the uppermost layer is increased or the filler is dispersed, when used as a medium for the magnetic field modulation recording method, scratches due to the magnetic head and the magnetic head are caused. Since adsorption to the recording medium is reduced, stable floating of the recording medium can be achieved.

Also, an optical recording medium having the above-mentioned effects can be easily manufactured by a method of sequentially coating one organic protective layer consisting of two or more layers.

Further, by sharing the function among the respective layers of the multi-layer organic protective layer, the selection range of the material is widened and the total performance of the organic protective layer can be improved as compared with the conventional single layer organic protective film medium. .

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of an optical recording medium of the present invention.

FIG. 2 is a partial cross-sectional view of a conventional optical recording medium.

FIG. 3 is a partial cross-sectional view showing another embodiment of the optical recording medium of the present invention.

[Explanation of symbols]

 1 Substrate 2 Underlayer protection layer 3 Recording layer 4 Interference layer 5 Reflection layer (heat dissipation layer) 6 Film piece 7 First layer protection layer 8 Second layer protection layer 9, 9'Third layer protection layer 10 , 10 'Organic protective layer of the present invention 11 Convex portion of vacuum film forming layer 12 Convex portion of protective layer surface 13 Conventional organic protective layer 14 Filler

Claims (7)

[Claims] 1. An optical recording medium comprising a vacuum film-forming layer composed of at least a recording layer and an organic protective layer formed on an optically transparent substrate, wherein the organic protective layer is divided into two or more layers. An optical recording medium characterized by being provided. 2. The optical recording medium according to claim 1, wherein the hardness of the uppermost layer of the organic protective layer is higher than that of the lowermost protective layer. 3. An optical recording medium according to claim 1, wherein a filler is dispersed in the uppermost layer of the organic protective layer. 4. The optical recording medium according to any one of claims 1 to 3, wherein the organic protective layer is an ultraviolet curable resin. 5. The optical recording medium according to claim 1, wherein the organic protective layer is formed by a spinner. 6. The optical recording medium according to claim 1, wherein the optical recording medium is a magneto-optical recording medium. 7. In the production of an optical recording medium in which a vacuum film-forming layer comprising at least a recording layer and an organic protective layer thereon are provided on an optically transparent substrate, the organic protective layer is divided into two or more layers. A method for manufacturing an optical recording medium, characterized in that a step on the outer surface of the optical recording medium is reduced by sequentially coating.