JPH0337844A - Magneto-optical disk - Google Patents

Abstract

PURPOSE:To facilitate overwriting and to enhance environmental resistance by coating at least the surface on the side facing a magnetic field generating means with a compsn. essentially consisting of fluoroplastic soluble in an org. solvent. CONSTITUTION:The magneto-optical disk is formed by forming a dielectric film 2, a magneto-optical recording film 3 and an inorg. protective film 4 in common use as a reflecting film in this order on a transparent plastic substrate 1. The uppermost layer of the magneto-optical disk obtd. in such a manner on the side facing the magnetic field generating means is coated with the protective film 5 consisting of the resin compsn. essentially consisting of the fluoroplastic soluble in an org. solvent. The disk exhibits excellent durability and lubricity in this way and is capable of exhibiting head crash resistance. The fluoroplastic to be used has preferably >=80 deg. contact angle with the water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a magneto-optical disk which has excellent environmental resistance and can be used for overwriting purposes.

[Prior Art 1] In recent years, commercialization and development of optical discs as one type of large-capacity memory have been active. Among them, 81 rewritable light records
Research on the practical use of magneto-optical disks as a medium is being actively conducted.

Conventionally, as a rewritable magneto-optical recording system, methods of using multiple optical heads, such as separate heads for recording and erasing, have been considered. As a 6-layer LxtF system, which is desired to develop a magneto-optical disk that can be overwritten, we believe that it is preferable to use a magnetic field modulation method for magneto-optical recording media in terms of performance, simplicity, etc. In this method, information is recorded and removed by heating the recording film and changing the direction of the external magnetic field. Overwriting becomes possible by modulating the magnetic field, that is, by adjusting the direction of the magnetic field generated by a magnetic field generating means such as an external magnet upward or downward with respect to the disk.However, if the direction of the external magnetic field is fM
In order to change the frequency in a range (usually 1 to 5 MHz), it is necessary to bring a magnetic field generating means such as a magnet close to the disk, and when using a magnetic disk head as the magnetic field generating means, the recording medium It is said that the gap with the surface must be 5 μm or less.

In this case, the magnetic head may come into contact with the disk when the disk starts or stops rotating, or when the medium deforms.
Fa failure of the disk becomes a big problem.

Another big problem in this case is the restriction on the thickness of the protective film.As mentioned above, it is desirable that the distance between the magnetic head and the 5J1 film be as short as possible, and usually 20. It is required to keep it below um. Therefore, the protective film is also required to have a sufficient protective effect with a thickness of 10 μm or less.

As described above, the protective film on the magnetic field generating means side of the magnetic head of a magneto-optical recording medium that can be overwritten has 1) performance as a protective film that provides sufficient durability with a thin film of 10 μm or less, and 2)
) Although durability against head crushing is required, no material with satisfactory performance has been found to date.

[Purpose of the Invention] The present invention was made in view of the current situation, and its purpose is to provide a protective film with a thickness of 10 μm or less that can be used for magnetic field modulation override and has sufficient durability even under high temperature and humidity conditions. The goal is to provide magneto-optical disks with (2) It is an object of the present invention to provide a magneto-optical disk in which deterioration of the optical recording film is prevented by the protective layer and has excellent durability against head crashes that occur when starting or stopping rotation of the disk.

[Nara 1 Effects of the Invention] That is, the present invention provides a magneto-optical disk in which at least the open surface facing the magnetic field generating means is coated with a V11 resin composition which is mainly composed of a flute resin soluble in an organic solvent. This is a magneto-optical disk characterized by being coated with. In the present invention, the resin composition preferably has a contact angle of 80 degrees or more with respect to water of the fluorine thread resin as its main component from the viewpoint of slipperiness, water resistance, etc.

The present invention will be explained in detail below.

The resin composition of the present invention, which has a fluorine-containing resin as a main component that is soluble in organic solvents, exhibits crushing durability, slipperiness, and head crushing resistance compared to conventionally used ordinary resin compositions. It has an effect.

Furthermore, a feature of the present invention is that, as mentioned above, since the lubricant is a compound or resin itself that exhibits lubricating properties, it is possible to use the lubricant constantly without worrying that the lubricant will smear and stain during long-term use. .

The organic solvent-soluble strand resin used in the present invention may be a copolymer of vinylbutylene and hexafluoropropylene, a copolymer mainly composed of a single fL form of vinylidenebutylene, or vinylidenebutylidene. Copolymers of hexafuro-1-copropylene or copolymers containing these monomers as main components,
Copolymers of vinylidene butoxide and vinyl acetate, or partially saponified products thereof, fluoroalkyl (meth)acrylates 1-1
or copolymers thereof.

Among these, for example, in a copolymer of vinyl fluoride and hexafluoropropylene, the content of vinyl fluoride is 60 to 90 mol%, and in a copolymer of vinylidene fluoride and hexafluoropropylene, the content of vinylidene fluoride is 50%. ~90 mol%
Preferably.

There are no particular restrictions on the fluoroalkyl (meth)acrylate-1 or their copolymers.As the monomer, C
Il□=c++coz C1l□ (CF2 n, iC
+'.

CH2=ClIC02CF (CF3) 2,
CH2= CHCO2Cl+2(C'2)z
C) 3, CH2=Cl1CO2Ctl
(CF3) 2, CH2ClIC0□(C
)12) 20Cr(CF3)2, C1l□
=Cl1C02fcH2) 50Cr(CF3) 2
, C112=Cl1CH3COz CH2CF3.

C112= CC)+3 CO2C port (CF3)
2, CH2=CC1(3C02C)(C"
3) z and the like are preferred, and these may be used alone or as a copolymer with other monomers.The fluororesin of the present invention has excellent surface energy properties such as slipperiness, stain resistance, and water resistance. It can be said that a material with a large value is preferable. Moreover, the magnitude of surface energy can be compared by the magnitude of contact angle.

As described above, the flute resin used in the present invention has a contact angle with water of 80" or more, more preferably 0°
It is desirable that there be at least one.

In the present invention, in order to prevent deterioration of the recording film, the resin composition may contain an element that has a greater ionization tendency than the transition metal elements constituting the recording film, and such elements are not particularly limited. Preferably, it is selected from the group consisting of aluminum, dumbbell, magnesium, or rare earth elements, and rare earth elements include terbium (Nb), dysprosium (Dy), gadolinium (Gd), neodymium (Nd), and praseodium. (P'') etc. are particularly preferred. In the present invention, for example, when iron is used in the recording layer, magnesium, aluminum, zinc, neodymium, etc. may be used.

These metals may be used alone, as a mixture, or as an alloy, but if they can be obtained in the form of fine powder, they can be mixed with a resin raw material to form a stable dispersion for the purpose of the present invention. Is it possible to use?

These resins and powders can be mixed using a mixing means such as a ball mill, a V-type blender, or a calendar, and then used.

There are no particular restrictions on the mixing ratio of the resin and the powder, and it can be determined appropriately within the range that allows efficient formation of a stable coating, taking into account coatability and other conditions. The amount of these metals added varies depending on the metal element and resin material used, but in terms of effectiveness, it is preferable to add 5 parts or more per 100 parts by weight of the resin.Are there any restrictions on adding more than this? ($ 1 Determined by considering the overall performance as a membrane. Usually, it is preferably 4 times or less the weight of the resin.

The present invention is a magneto-optical disk in which a protective layer made of the above-mentioned resin composition is provided at least on the surface (2) facing the magnetic field generating means. To form this protective layer, a film forming method commonly used in forming an organic cA protective film for optical discs, such as a spin code method or a dipping method, can be used.

It is also possible to form the resin composition of the present invention into a sheet or film in the form of an acid in advance and then laminate it on the surface of a recording film by a method such as natural fusion.

The coating thickness must be carefully determined when using the above-mentioned override method, as too thick a coating may cause problems, and conversely, if the coating is extremely thin, there may be concerns about efficacy1. Generally, the thickness is preferably 10 μm or less.

In addition, in order to stabilize the dispersion state of the powder, it is possible to use techniques and materials applied in the paint industry, such as adding a dispersion stabilizer, as long as it does not affect the effects of the present invention. It is a useful tool for improving productivity.

In addition, in order to improve contact conditions against head crashes and provide durability, lubricants such as carbon black graphite, mica, talc, kaolin, calcium carbonate, aluminum oxide, silicon oxide, molybdenum sulfide, silicon carbide, and silicon nitride are used in the present invention. These materials that can be mixed into the resin composition and have an interfolding property, such as graphite, mica, molybdenum sulfide, etc., slide in a specific direction or plane and have an interfolding property, so they cannot be affected by external force. When applied, appropriate displacement occurs on the sheared surface and has a lubricating neck-breaking effect.

Furthermore, among the configurations of magneto-optical disks to which the present invention can be applied, there are no limitations on the configuration from the substrate to the recording film or the dielectric film thereon.
The present invention can be applied to all media, including a structure in which a recording film 1 and a dielectric film are laminated, and a structure in which a metal 4 film such as 11 is provided between the dielectric film and the recording film. Regarding the individual elements, transparent substrates include glass, polycarbonate resin,
A transparent substrate such as acrylic resin or 7n as a dielectric film
S, SIO2, AIN, Si3 N4,
A film made of Al10s etc. is used as a magneto-optical recording film.
1bFeco.

TbFe-based alloys such as TbreGd, or Ndr
NdFe-based alloys such as eCo, and even NdDyFeC
A typical example is a film made of an alloy of a rare earth element and a transition metal element, such as an alloy. Note that the present invention is effective for recording layers whose main components are the above-mentioned alloys of rare earth elements and transition metal elements, which easily deteriorate.

These include dielectric films, magneto-optical recording, and metal thin films.

In some cases, the base film is formed by a conventional method such as a physical film forming method (PVD method) such as a thin film sputtering method.

By the way, when the protective layer made of the resin composition of the present invention is provided on the surface of the recording film opposite to the substrate, it may be formed directly on the recording film. From the aspect of preventing deterioration and deterioration of the recording film, it is necessary to use a method developed in physics in a vacuum, similar to the method used to form a thin film such as a dielectric material (as a material for contacting the eI layer). It is more desirable to form a film by using the above method and provide it thereon.

[Effects of the present invention] According to the present invention, in a magneto-optical disk, at least the open surface facing the magnetic field generating means is coated with a composition whose main component is a fluorine thread resin soluble in an organic solvent. Since the modulating magnetic head of the generating means can be placed close to the surface, it is possible to obtain a magneto-optical disk that can be easily overwritten and has a high degree of environmental resistance.

This will be explained below using examples.

FIG. 1 is an explanatory diagram of the laminated structure of Examples and Comparative Examples, in which a dielectric film 2 and a magneto-optical recording film 3 are provided with an inorganic dielectric film 2 and a magneto-optical recording film 3 provided on a transparent plastic substrate 1 to provide moisture protection and other protection. This is an example in which a membrane 4 is provided and a resin composition coating 5 is provided thereon.

Examples 1-5. Ratio I bite case 1 1 (!Using a magnetron sputtering device, lt+
A dielectric film 2 made of friz 03 (650A) was deposited on a transparent plastic substrate 1 made of 5.25-inch disk-shaped polycarbonate l~ using a reco alloy target I'', an Inz 03 target, and an Inz 03 target. A magneto-optical disk was prepared by sequentially depositing a magneto-optical recording film 3 consisting of 500 Å) and an inorganic protective film 4 which also served as a reflective film and consisting of 11 (550 Å).

Next, each of the coating liquids shown in the table was applied to the magneto-optical disks obtained as described above, and the coating liquids were heated and dried at 80'C for 30 minutes to obtain samples of Examples and Comparative Examples shown in the table.

The compositions of coatings MA to H in the table are as follows. The unit of numerical value of 0 composition is parts by weight. Also, 6 contact angle is the contact angle with respect to water.

Coating liquid A: F-1,6 copolymer A (contact angle 92") 5 Diacetone alcohol 10 Cellsolve acetate 5 Coating liquid B: Kifu A AI grain powder AI powder particle size: 7 μm) Coating liquid C: 1 - d = A αA1203 (particle size < 0.5 μm) Coating solution D = Coating/ri, B a -Al103 (particle size < 0.5 μm) Coating E2 F-2,6 copolymer B (contact Angle 93° Diacetyl alcohol cell solve acetate 1 Coating?jF Nitrifluoroethyl methacrylate polymer contact angle 87°) Diacetate alcohol cell solve acetate coating G: Hexafluoroisopropyl acrylate 1 Polymer (contact angle 97゛) Diacene alcohol Cellsolve Acetate 1 Coating liquid H: 0 Trifluoroethyl acrylate styrene diacetone alcohol Cellsolve acetate Coating liquid I: Fudayanal 1N503 (Product name) (Contact angle 64
°) 10 Xylene 10 Coronate-L (Product name) 3.1 Dibutyltin silaurylate 0.1xlO' The details of the polymer used in the above coating liquid are as follows. 6F-1.6 copolymer A Copolymer of vinyl fluoride (80 mol%) and hexafluoropropylene η-0.4 do-2.6 copolymer Fluorinated Copolymer of vinylitine (70 mol%) and hexafluoropropylene η・0.5 trifluoroethyl methacrylate polymer Polymer of trifluoroethyl methacrylate.

η・0.3 Hexafluoroisopropyl acrylate-1-polymer Hexafluoroisopropyl acrylate polymer,
η"0.4 Truffle 1 Chloethyl acrylate, styrene copolymer 1-Lifluoroethyl acrylate h (60 mol%) and styrene copolymer, η"0.3 Tiyanal LR1503: Mitsubishi Rayon■ Solid content 50 %, 00 value 32■K O+
-1/f Coronate single Japanese polyurethane ■ Solid content 75%, NCO content 13.4% And for each sample obtained, 1# (dynamic friction coefficient was measured as an evaluation of crushability. The results are shown in the table. .

Further, regarding durability, each sample was subjected to repeated deterioration testing under the following two conditions, and evaluated by visually observing changes in appearance before and after the test.

Condition 1: Immerse a sample in an IN NaCl aqueous solution for 24 hours and observe the appearance before and after Condition 2: Immerse a part of the sample in a 3wt% NaCl aqueous solution at 80°C for 24 hours: i! fL, observe changes in the appearance mainly of the interface between the immersed part and the non-immersed part (air-liquid interface) before and after fL. Furthermore, 3.1 in the table! The results are based on the following evaluation criteria.

◎: No external abnormality ○: Slight increase in pinball (5 (hard)) Δ: Change in appearance (reflection, etc.) M10% or less or increase in pinholes 20 or less ) change of 10% or more From the results shown in the table, it was confirmed that the present invention has excellent slip properties and excellent durability.

table Examples and comparative examples

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of laminated Ti4 layers of Examples and Comparative Examples. 1: Transparent plastic substrate, 2: Electrical conductor film, 3: Magneto-optical recording film, 4: Black machine protective film, 5, La 1 fat composition protective film

Claims (1)

[Scope of Claims] 1) In a magneto-optical disk in which recording and erasing is performed by applying a magnetic field using a magnetic field generating means, the uppermost layer of the magneto-optical disk on the side facing the magnetic generating means is made of a material soluble in an organic solvent. A magneto-optical disk characterized by being coated with a resin composition containing a fluororesin as a main component. 2) The magneto-optical disk according to claim 1, wherein the fluororesin has a contact angle with water of 80 degrees or more.