JP3518887B2 - Optical information recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium such as a magneto-optical disk, and more particularly, to a method of applying a film supported on one surface of a transparent substrate to a mechanical shock or the like. The present invention relates to a protective film and a lubricating layer that protect against chemical influences. 2. Description of the Related Art In recent years, a magneto-optical disk having a large capacity and capable of rewriting information as many times as possible has been put to practical use as, for example, an optical file system, an external storage device of a computer, and a storage device for audio or video information. ing. There are so-called magnetic field modulation methods and optical modulation methods for recording on the magneto-optical disk. The magnetic field modulation method is used because a new signal can be overwritten on a previously recorded signal. This is advantageous in rewriting information quickly. In magneto-optical recording of the magnetic field modulation system, an optical head is disposed on a substrate side and a magnetic head is disposed on a protective film side via a magneto-optical disk having a single-plate structure, and a laser beam having a predetermined intensity is irradiated from the optical head. While heating the magneto-optical recording film to a temperature close to the Curie temperature or the compensation temperature, a magnetic field is applied from the magnetic head to the temperature-raising portion, and the applied magnetic field is reversed at a high speed, whereby information is recorded on the magneto-optical recording film. Record the sign. Since a magnetic head that applies such a high-speed reversal magnetic field can generate only a very small magnetic field due to various restrictions, it is necessary to arrange the magnetic head as close to the magneto-optical recording film as possible to compensate for this. . If the magnetic head is brought into contact with the protective film, the magnetic head can be brought closest to the magneto-optical recording film. However, in this case, since the protective film is easily damaged by friction with the magnetic head at the time of rotational driving, it is particularly important to form a protective film having excellent scratch resistance and lubricity. Conventionally, a method has been proposed in which a lubricant is mixed into a protective film made of an organic polymer material, or a lubricant is applied on a protective film made of an organic polymer material or an inorganic dielectric material. However, in the method of mixing a lubricant into the protective film, the protective film becomes porous and easily absorbs moisture, which may impair the corrosion resistance of a film such as a magneto-optical recording film. Also,
It is difficult to obtain a sufficient effect in terms of lubricity, and there is a disadvantage that the disk and the magnetic head are easily worn. On the other hand, in the method of applying a lubricant on the protective film, although the lubricating effect is easily obtained, since the wettability of the lubricant on the protective film surface is greatly affected, the lubricating effect is not uniformly applied depending on the location because the lubricant is not uniformly applied. Easy to get uneven. In addition, this method has a disadvantage that the lubricating effect does not last for a long time because the lubricant easily falls off every time the magnetic head slides. Therefore, in order to improve the practicality of the magneto-optical drive device of the magnetic field modulation system,
It is indispensable to develop a protective film material and a lubricant which can provide a sufficient lubricating effect and a protective effect of the film body, easily form a uniform lubricating layer on the protective film, and which are less likely to lose the lubricant when used. The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical information recording medium having excellent lubricity and durability. According to the present invention, in order to achieve the above object, one or more layers including at least a recording film or a reflection film are supported on one surface of a transparent substrate, In an optical information recording medium in which the surface of the film body is coated with a protective film, the protective film is made of an ultraviolet-curable resin composition containing a fluorine compound having at least one or more acryl or methacryl group. At the same time, a lubricating layer made of a fluorine compound containing a perfluoropolyether segment in the molecule was provided on the surface of the protective film. The UV-curable resin composition for forming the protective film is not particularly limited, but those which have been conventionally used as a protective film material for optical information recording media, especially UV-curable acrylates Based resin compositions are preferred. The fluorine compound having an acrylic group or a methacryl group contained in the ultraviolet-curable resin composition includes, for example, trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2 , 3,4,4,4-hexafluorobutyl methacrylate, perfluorooctyl methacrylate and the like. [0010] The thickness of the protective film is preferably 0.1 to 30 µm. If it is less than 0.1 μm, it is difficult to secure a sufficient protective effect because the protective film is too thin. On the other hand, if it exceeds 30 μm, cracks may occur in the protective film due to curing shrinkage of the resin and magneto-optical This is because the strength of the magnetic field reaching the recording film becomes small and a large driving current is required. The protective film is formed, for example, by applying an ultraviolet curable resin composition to a predetermined portion of the substrate on which the magneto-optical recording film is formed by a spin coater, a roll coater, a bar coater, or the like, and then irradiating the resin composition with ultraviolet rays. It can be formed by curing. The perfluoropolyether segments contained in the molecules of the fluorine compound forming the lubricating layer include polyethers represented by the following general formulas (1) and (2) and molecular ends of these polyethers. And a polar group such as a hydroxyl group, a carboxyl group, a phosphoric acid group, a sulfonic acid group, or a salt or ester group thereof. These have excellent lubricity and oxidation resistance. Note that the subscripts x, y, q, and in general formulas (1) and (2)
r is an integer, and each is preferably in the range of 5 to 200. [0013] Embedded image As a method for forming a lubricating layer, a spin coating method is generally used, but the method is not limited to this.
If necessary, a different method can be adopted as appropriate. Further, the fluorine compound for forming the lubricating layer may be diluted with a solvent during use or storage. Further, the thickness of the lubricating layer is preferably 1 nm to 1 μm.
If the thickness of the lubricating layer is less than 1 nm, it is difficult to secure sufficient durability. Conversely, if the thickness exceeds 1 μm, sticking of the magnetic head to the disk surface is likely to occur, so that the running stability of the magnetic head can be improved. This is because there is a possibility that the property may be deteriorated. When a UV-curable resin composition containing a fluorine compound having at least one acryl group or methacryl group is used, a dense protective film can be formed when cured. By forming the film into a film thickness, the film body can be effectively protected from mechanical impact and chemical influence. In addition, when a fluorine compound containing a perfluoropolyether segment is applied on this protective film, the wettability is improved, so that a fluorine-based lubricating layer which is uniform and hard to fall off from the protective film can be formed. As a result, a good lubricating action is continuously exerted, and the magnetic head can be run by directly contacting the disk surface, so that a magneto-optical recording medium capable of recording information with a small external magnetic field can be provided. FIG. 1 schematically shows a cross-sectional structure of an optical information recording medium according to an embodiment. As is clear from this figure, the optical information recording medium of the present example has an enhanced film 3 made of an inorganic dielectric on a preformat pattern forming surface 2 of a transparent substrate 1.
A magneto-optical recording film 4, an inorganic protective film 5 made of an inorganic dielectric, and a reflective film 6 made of metal are sequentially laminated by sputtering, and a protective film 7 is formed so as to cover these film bodies 3 to 6. Further, a lubricating layer 8 is formed on the outer surface of the protective film 7. Reference numeral 9 in the drawing denotes a film-coated substrate having no protective film 7 and no lubricating layer 8. The transparent substrate 1 is formed of a transparent ceramic material such as glass, or a transparent resin material such as a polycarbonate resin, a polymethyl methacrylate resin, a polymethyl pentene resin, an epoxy resin, a photocurable resin, or the like into a desired shape and dimensions. Is done. On one surface of the transparent substrate 1, a preformat pattern 2 such as a guide groove of a recording / reproducing laser beam or an address pit row is formed in a fine uneven shape. Note that the shape, arrangement, forming method, and the like of the preformat patterns 2 are well-known technologies and are not the gist of the present invention, and thus description thereof will be omitted. The enhancement film 3 makes the reproduction laser beam multiple-reflect between the preformat pattern forming surface of the transparent substrate 1 and the magneto-optical recording film 4 and increases the apparent Kerr rotation angle to increase the reproduction CN ratio. For obtaining SiO, SiO ₂ , SiN, Si
The refractive index of the reproducing laser beam, such as ₃ N ₄ , AlN, Al ₂ O ₃ , is formed of an inorganic dielectric material slightly larger than that of the transparent substrate 1. The magneto-optical recording film 4 can be made of any known magneto-optical recording material. In particular, since a relatively large Kerr rotation angle can be obtained, the rare-earth element and the transition element can be used. A perpendicular magnetic film mainly composed of As this type of recording material, Gd-F
binary alloys such as e, Tb-Fe, Dy-Fe, Gd-Co, Gd-Tb-Fe, Gd-Fe-Co, Tb-Fe
Ternary alloys such as -Co, Dy-Fe-Co, Gd-Tb-
There are quaternary alloys such as Fe-Co and Tb-Dy-Fe-Co. The inorganic protective film 5 protects the magneto-optical recording film 4 from mechanical shocks and corrosive atmospheres, and also causes the reproducing laser beam to be reflected between the magneto-optical recording film 4 and the reflective film 6 in a multiple-reflection manner. Large playback CN by increasing the car rotation angle above
It is provided to obtain a ratio, and is formed of the same inorganic dielectric as the enhance film 3. The reflection film 6 is provided to return the reproducing laser beam transmitted through the magneto-optical recording film 4 to the transparent substrate 1 side and to obtain a large signal intensity. For example, aluminum, aluminum alloy, stainless steel And the like. The protective film 7 is formed of an ultraviolet-curable resin composition containing a fluorine compound having at least one acrylic or methacrylic group. On the other hand, the lubricating layer 8 is formed of a fluorine compound containing a perfluoropolyether segment in the molecule. These protective films 7
The lubricating layer 8 will be described below with reference to specific examples and comparative examples. Example 1 An ultraviolet-curable resin composition having the following composition 1 was spin-coated on the reflective film 6 of the substrate 9 with a film shown in FIG. 1, and then irradiated with ultraviolet rays to cure the resin. A protective film 7 having a thickness of 5 μm was formed. Next, a solution of the following composition 2 was spin-coated on the protective film 7,
A lubricating layer 8 was formed to obtain a desired magneto-optical disk. [Composition 1] Tricyclodecane diacrylate 80 parts by weight Dimethylolpropane tetraacrylate 10 parts by weight Photopolymerization initiator (“IRG-184” manufactured by Nippon Ciba Geigy) 5 parts by weight Perfluorooctylethyl methacrylate 0.05 Parts by weight [Composition 2] 1 part by weight of perfluoropolyether (“Krytox” manufactured by DuPont) 100 parts by weight of perfluorooctane <Example 2> Similarly to Example 1, the following composition 3 was formed on the reflective film 6. A protective film 7 and a lubricating layer 8 having the following composition 4 were sequentially formed to obtain a desired magneto-optical disk. Other conditions were the same as in Example 1. [Composition 3] Tricyclodecane diacrylate 75 parts by weight Trimethylolpropane triacrylate 12 parts by weight Photopolymerization initiator (IRG-184) 5 parts by weight Benzophenone 3 parts by weight 2,2,3,3-tetrafluoropropyl 0.1 parts by weight of methacrylate [Composition 4] 1 part by weight of perfluoropolyether (“Demnum” manufactured by Daikin) 100 parts by weight of Freon <Comparative Example 1> The same composition as in Example 1 was formed on the reflective film 6. A protective film of No. 1 and a lubricating layer of the following composition 5 were sequentially formed to manufacture a magneto-optical disk. Other conditions were the same as in Example 1. [Composition 5] 1 part by weight of silicone oil (“KF96” manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts by weight of hexane <Comparative Example 2> Only the protective film of the above composition 2 was formed on the reflective film 6 and lubricated. A magneto-optical disk having no layer was produced.
Other conditions were the same as in Example 1. A spherical slider made of ruby having a radius of curvature of 3 mm is brought into contact with the protective film side of each magneto-optical disk manufactured as described above, and the magneto-optical disk is driven at 500 rpm under a load of 2 g weight. in it is rotated, to observe scratches friction coefficient and surface during 10 ⁵ path sliding. At that time, the measurement position was set to a position 25 mm from the center of rotation of the disc, and the scratch on the disc surface was observed with an optical microscope, and evaluated by the width of the sliding mark. Further, the presence or absence of uneven coating when the lubricating layer was applied was visually observed and evaluated. The result is shown in FIG.
Shown in As is clear from FIG. 2, none of the magneto-optical disks according to the examples has a coating on the lubricating layer.
10 ⁵ coefficient of friction during the path sliding is small, sliding marks of the slider did not occur. Among the magneto-optical disk according to the embodiment, towards the magneto-optical disk according to Example 1, it was smaller coefficient of friction during the 10 ⁵ Path sliding. On the other hand, in the magneto-optical disk according to Comparative Example 1, uneven coating of the lubricating layer occurs, and the friction coefficient at the time of 10 ⁵ pass sliding is 6 to 9 times or more as compared with the magneto-optical disk according to the example. , And a sliding mark of a slider having a width of 70 μm was generated. Magneto-optical disc according to Comparative Example 2, the friction coefficient at the time of 10 ⁵ Path sliding it is further increased and became more larger sliding mark of the slider. Therefore, if the magneto-optical disk according to the embodiment is used, the disk can travel while the magnetic head is in direct contact with the disk surface, so that information can be overwritten with a small external magnetic field. In addition, since a servo mechanism and a flying head mechanism for holding the magnetic head at a position slightly separated from the disk surface are not required, the configuration of the drive device can be simplified, and the magneto-optical disk due to the crash of the magnetic head can be obtained. Can be prevented from being damaged. In the above embodiment, a magneto-optical disk has been described as an example. However, it goes without saying that the present invention can be applied to all optical information recording media having a protective film. Further, an optical information recording medium provided with a protective film on the surface side of the substrate can be applied in the same manner. As described above, according to the present invention,
Since the wettability of the lubricating layer with respect to the protective film is improved, a good lubricating effect can be maintained, and the recording / reproducing characteristics and durability of the optical information recording medium can be remarkably improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a principal part schematically showing a sectional structure of a magneto-optical disk according to an embodiment. FIG. 2 is a table showing the effects of the embodiment. [Description of Signs] 1 transparent substrate 2 preformat pattern 3 to 6 film body 7 protective film 8 lubricating layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-21113 (JP, A) JP-A-61-120340 (JP, A) JP-A-4-209346 (JP, A) JP-A-5-205 166173 (JP, A) JP-A-2-12247 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/24 G11B 11/105

Claims (1)

(57) [Claim 1] One or more layers including at least a recording film or a reflection film are supported on one surface of a transparent substrate, and the surface of the film is covered with a protective film. In the coated optical information recording medium, the protective film is formed of a UV-curable resin composition containing a fluorine compound having at least one or more acrylic or methacrylic group, and is formed on the surface of the protective film. An optical information recording medium comprising a lubricating layer comprising a fluorine compound containing a perfluoropolyether segment in a molecule.