JP2678508B2 - Magnetic disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a magnetic disk.

B. 2. Description of the Related Art Although an information recording element is an essential element in an information processing system, magnetic recording in this system in particular has already accumulated a considerable amount of technology, and is cheaper than other recording methods, and recording is not easy. It is the mainstream in this field because it is non-volatile.

In recent years, there has been a strong demand for high density and high capacity. In order to increase the density and capacity of magnetic recording media, (1) Excellent surface smoothness to reduce spacing loss.

(2) Excellent dispersibility and high filling degree of the magnetic material for high output.

Is required.

On the other hand, the higher the capacity of the recording medium, the more durable,
Improvement of reliability is also strongly desired. To improve durability and reliability: (1) The magnetic layer should have excellent wear resistance.

(2) No foreign matter such as dust or dust is attached to the surface of the magnetic layer.

Characteristics such as are desired.

For the magnetic recording as described above, for example, a floppy disk is used, which is a disk-shaped magnetic recording medium having a magnetic layer containing magnetic powder and a binder, and a liner for cleaning the medium in contact with the magnetic layer. And are placed in the case. The above liner is generally made of a non-woven fabric (for example, a rayon braid bonded by thermoplastic polypropylene), and its peripheral portion is joined to the inner surface of the case by heat welding or ultrasonic welding.

However, although conventional non-woven fabrics mainly composed of rayon have relatively good cleaning properties, they often generate resin powder and feathers detached from the non-woven fabric. On the contrary, if the amount of components other than rayon that suppresses the generation (for example, polyester fiber or polypropylene) is increased, the cleaning property is deteriorated or the magnetic layer is damaged, and the dropout increases.

On the other hand, while high density, high output and high durability of floppy disks are required, there is no known binder showing sufficient dispersibility for fine magnetic powder, and high density and high durability. Was difficult to secure.

C. OBJECT OF THE INVENTION It is an object of the present invention to provide a magnetic disk which is excellent in reliability over a long period of time under any environmental condition, and which has high durability and high density and high output.

D. Structure of the Invention That is, the present invention relates to a magnetic disk in which a disk-shaped magnetic recording medium having a magnetic layer containing magnetic powder and a binder, and a liner in contact with the magnetic layer are arranged in a case. The liner is formed by a non-woven fabric containing 30% by weight or more of fibers and / or polyacrylonitrile fiber (30% by weight or more when both fibers are contained), and the binder is a sulfo group, a phospho group or a carboxyl group. A vinyl chloride resin containing at least one selected from the group consisting of groups and alkali metal salts of these groups, and selected from the group consisting of sulfo groups, phospho groups, carboxyl groups and alkali metal salts of these groups. And a polyurethane resin containing at least one kind and a hydroxyl group are used in combination. Which relate.

1 and 3 show a 3.5 inch floppy disk 1 according to an example of the present invention.

FIG. 3 shows the inner surfaces of the upper half 2 and the lower half 3 of the case (shell) of the disc 1 separated from each other. Openings 7 and 8 are formed in each half, and the internal disk medium 10 faces these openings 7 and 8. The openings 7 and 8 are normally shielded by a metal shutter (not shown) having a U-shaped cross section when the disk is not used, and the disk medium 10
Although the (media) is not exposed, the shutter is moved to the open position during disk drive (during magnetic recording), and the recording surface of the disk medium 10 is exposed in the opened openings 7 and 8. There is. In addition, the disk medium 10
Is rotatably accommodated in the body halves 2 and 3 while being fixed to a center hub (not shown) mounted on the drive side spindle. Almost C-shaped liners 4 and 5 attached to the inner surface of each half for cleaning a disk medium
(Shaded in FIG. 3) peripheral portions 4a, 4b and 5a,
5b is bonded and fixed to the inner surface of each half by heat welding or ultrasonic welding. Then, as shown in FIG. 1, when the disc drive is mounted, the disc medium 10 is rotated to move to the lower half 3.
The liner 5, the disk medium 10, and the liner 4 are pressed by the lifter 11 fixed at 11a against the ribs 12 on the upper half 2 side at the lifter position, where sliding contact (that is, cleaning) between the disk and the liner is performed.

The disk medium 10 is, for example, as shown in FIG. 2, provided with a magnetic layer 24 on both surfaces of a non-magnetic support 21 via an undercoat layer 22 if necessary. If desired, an overcoat layer (not shown) may be further provided on the magnetic layer.

In the above-exemplified floppy disk, a nonwoven fabric containing 30% by weight or more of polyester fibers and / or polyacrylonitrile fibers (when both fibers are contained, the total content is 30% by weight or more) is used as the liners 4 and 5. In this non-woven fabric, both the above polyester and polyacrylonitrile fiber not only have the function of binding the braid such as rayon that constitutes the non-woven fabric to prevent the detachment, but the same fiber alone forms the braid of the non-woven fabric. And can exhibit sufficient cleaning property. For this reason, it is essential that the amount of the fibers is 30% by weight or more of the total amount of the nonwoven fabric based on the present invention, and preferably 50% by weight or more.

Specific examples of such liners are shown below (however, E represents polyester, A represents polyacrylonitrile, R represents rayon, and numbers represent weight ratios).

(A) Polyester fiber-containing liner Kendall 149-007 (E = 100) Kendall 149-188 (E50R50) Mitsubishi Rayon TK450D (E50R50) H / V # 1002 (E50R50) Kendall Company's SP-286 (E70R30: Three-layer structure liner) (b) Polyacrylonitrile-containing liner Mitsubishi Rayon VA-250 (A100) Mitsubishi Rayon VK-450 (A50R50) In the above, as a liner component The components other than polyester and polyacrylonitrile include not only rayon but also nylon and the like.

In addition, the liner may contain a lubricant, an antistatic agent, or the like.

Further, it may be a liner having a layered structure as in JP-A-63-184977 and JP-A-63-157876. In this case, it is preferable that the liner layer on the surface in contact with the disk medium contains polyester or polyacrylonitrile.

The thickness of the liner is preferably 100 to 500 μm, more preferably 150 to 300 μm.

On the other hand, the magnetic layer 24 constituting the disk medium 10 described above,
It is a magnetic powder dispersed in a binder.

As the magnetic powder, for example, γ-Fe ₂ O ₃ , Co-containing γ-Fe
₂ O ₃ , Co deposited γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , Co deposited Fe
Oxide magnetic powder such as ₃ O ₄ and CrO ₂ ; Fe, Ni, Co, Fe-Al system, Fe
-Al-Ni system, Fe-Al-Co system, Fe-Al-Zn system, Fe-Ni-Co
System, Fe-Mn-Zn system, Fe-Ni system, Fe-Ni-Al system, Fe-Ni-
Ferromagnetic powders such as Zn-based, Fe-Co-Ni-Cr-based, Fe-Co-Ni-P-based, Co-Ni-based, etc., and metal magnetic powders containing Fe, Ni, Co, etc. as the main components are mentioned.

Then, the binder used for binding the magnetic powder contains at least one selected from the group consisting of a sulfo group, a phospho group, a carboxyl group and an alkali metal salt of these groups according to the present invention. A vinyl chloride resin is used in combination with a polyurethane resin containing a hydroxyl group and at least one selected from the group consisting of sulfo groups, phospho groups, carboxyl groups and alkali metal salts of these groups.

Among these resins, vinyl chloride resin has good dispersion of magnetic powder and improves the mechanical strength of the magnetic layer, and the polyurethane resin improves the wear resistance of the magnetic layer, so that Flexibility can also be imparted.

These resins include -SO ₃ M, -OSO ₃ M, -COOM, -PO
(OM ′) ₂ , —OPO (OM ′) ₂ (where M is hydrogen or an alkali metal such as lithium, potassium and sodium, M ′ is an alkaline metal such as hydrogen, lithium, potassium and sodium) and a negative functional group ( 1 or 2 hydrophilic polar groups)
Includes at least one species and hydroxyl group (in the case of polyurethane type). That is, due to the polar group and hydroxyl group in the molecule,
Familiarity between the resin and the magnetic powder is improved, which improves the dispersibility of the magnetic powder, prevents the magnetic powder from aggregating, and further improves the stability of the coating liquid, which in turn improves the durability of the medium. Can improve.

The vinyl chloride resin having at least one hydrophilic group selected from COOM, SO ₃ M, SO ₄ M, PO ₃ M ′ ₂ and PO ₄ M ′ ₂ and, if necessary, an epoxy group is (1) applicable hydrophilic group. Of a radically polymerizable monomer having a polymerizable group and, if necessary, a monomer having an epoxy group, with vinyl chloride, together with another monomer capable of being copolymerized, if necessary (2) For example, a method of copolymerizing a monomer having an epoxy group with other monomers that can be copolymerized with vinyl chloride using a radical generator having a corresponding hydrophilic group, if necessary,
(3) If necessary, a copolymer of a monomer having an epoxy group, vinyl chloride and another monomer used as necessary,
It can be obtained by a method of partially reacting with a compound having a corresponding hydrophilic group. It is also possible to combine these methods.

Examples of the epoxy group-containing monomer that can be used for the production of vinyl chloride-based resins having these hydrophilic groups and epoxy groups include glycidyl ethers of unsaturated alcohols such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate. , Glycidyl-p-vinyl benzoate, methyl glycidyl itaconate, glycidyl ethyl maleate, glycidyl vinyl sulfonate, glycidyl esters of unsaturated acids such as glycidyl (meth) allyl sulfonate, butadiene monooxide, vinyl cyclohexene monooxide, 2-methyl Examples thereof include epoxide olefins such as -5,6-epoxyhexene.

In the production of the vinyl chloride resin in the present invention, examples of the monomer having a hydrophilic group in the above method (1) include COOM, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, And unsaturated dicarboxylic acids such as fumaric acid and itaconic acid, and their monoesters.

Further, examples of SO ₃ M include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, ethyl (meth) acrylic acid-2-sulfonate, and 2-acrylamido-2-methylpropane. Examples thereof include acids such as sulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid, and alkali metal salts and ammonium salts of these acids. Examples of SO ₄ M include (meth) acrylic acid-2-ethyl sulfate, 3-allyloxy-2
-Acids such as hydroxypropanesulfuric acid and the alkali metal or ammonium salts of these acids.

Examples of PO ₄ M ′ ₂ include acids such as propyl (meth) acrylate-3-chloro-2-phosphate, ethyl (meth) acrylate-2-phosphate, and 3-allyloxy-2-hydroxypropanephosphoric acid, and There are alkali metal salts or ammonium salts of these acids. Examples of PO ₃ M ′ ₂ include acids such as vinylphosphonic acid, acrylamidomethanephosphonic acid, ethyl 2-phosphonate- (meth) acrylate, 3-allyloxy-2-hydroxypropanephosphonic acid, and alkalis of these acids. A metal salt or an ammonium salt can be used.

As an example of the radical generator having a hydrophilic group in the above method (2), COOM is 4,4′-azobis-4-
Cyanovaleric acid etc., SO ₄ M potassium persulfate, ammonium persulfate etc., PO ₄ M ₂ potassium perphosphate,
Examples include sodium superphosphate and the like.

Further, among the compounds used in the method (3) used for introducing a hydrophilic group into the resin by reacting with a copolymer of a monomer having an epoxy group and vinyl chloride, CO
As OM, malonic acid, phthalic acid, etc., as SO ₃ M, sodium sulfite, ammonium sulfite, sodium bisulfite, potassium bisulfite, ammonium thiosulfate, sodium taurine, sodium sulfanilate,
And sodium sulfamate is, as the SO ₄ M, sodium bisulfate, ammonium bisulfate and 2-aminoethyl sodium sulfate, the PO ₃ M _'2, sodium hydrogen phosphite, and phosphorous acid ammonium hydrogen, PO ₄ M _'2
Examples thereof include dipotassium hydrogen phosphate, disodium hydrogen phosphate and the like.

In addition, examples of the monomer other than the epoxy group-containing monomer, vinyl chloride and the hydrophilic group-containing monomer used as necessary include vinyl acetate, vinyl propionate, and other carboxylic acid vinyl esters; Methyl vinyl ether,
Vinyl ethers such as isobutyl vinyl ether and cetyl vinyl ether; vinylidene such as vinylidene chloride and vinylidene fluoride; diethyl maleate, butyl benzyl maleate, di-2-hydroxyethyl maleate;
Dimethyl itaconate, methyl (meth) acrylate, ethyl (meth) acrylate, lauryl (meth) acrylate,
Unsaturated carboxylic acid ester such as (meth) acrylic acid-2-hydroxypropyl; olefin such as ethylene and propylene; unsaturated nitrile such as (meth) acrylonitrile; aromatic such as styrene, α-methylstyrene, p-methylstyrene Examples include vinyl. These monomers are used not only for improving the solubility of the resin while adjusting the compatibility and softening point of the resin of the present invention and other resins when they are mixed, but also for the properties and coating properties of the coating film. It is appropriately selected according to the necessity such as improvement of the process.

Copolymerization of a monomer having an epoxy group and vinyl chloride,
Alternatively, the copolymerization of the monomer having an epoxy group, the monomer having a hydrophilic group and vinyl chloride can be carried out by a usual polymerization method including the case of further copolymerizing another monomer. In addition, the reaction between the copolymer of an epoxy group-containing monomer, vinyl chloride, and another monomer used as necessary, and a compound having a hydrophilic group can be performed by separating the properties of raw materials and products. Depending on process convenience, etc., it can be performed by a usual method.

Regarding the introduction of the polar group into the vinyl chloride-based copolymer, JP-A-57-44227, JP-A-58-108032, and JP-A-59-812.
No. 7, No. 60-101161, No. 60-235814, No. 60-238306
No. 60-238309, No. 60-238371, etc., and these can also be used in the present invention.

COOM, SO ₃ M, SO ₄ M, PO ₃ M ′ ₂ obtained as above
And the amount of the hydrophilic group bonded to the vinyl chloride copolymer resin having at least one hydrophilic group selected from PO ₄ M ′ ₂ and, if necessary, an epoxy group is —COO, —SO ₃ , —SO ₄ , P
O ₄ or desirably 0.05～4.0Wt% as -PO _3. If it is less than 0.05 wt%, the dispersibility of the magnetic powder tends to be insufficient, and if it exceeds 4.0 wt%, the hydrophilicity of the resin tends to be strong and the solubility in the solvent tends to be insufficient. The moisture resistance of the film is lowered, and further, the magnetic powder is agglomerated, so that the dispersibility is rather deteriorated.

The vinyl chloride resin in the present invention is 0.05 wt%
It is preferable to have the above epoxy groups.

The above vinyl chloride copolymer resin has an average degree of polymerization of 100 to 9
00, preferably 200-500, vinyl chloride content 60 wt%
It should be more than that. When the degree of polymerization is less than 100, the abrasion resistance of the magnetic layer is insufficient, and when it exceeds 900, the viscosity of the coating is high and the dispersion of the magnetic powder tends to be insufficient. Also,
When the content of vinyl chloride is less than 60% by weight, the compatibility with the flexible binder is lowered, and the solvent separation of the coating film is significantly lowered, which is apt to cause inconvenience.

The above polyurethane resin used in the present invention, similar -SO ₃ M and described above in the molecule, -OSO ₃ M, -COOM, -PO
It has at least one polar group of (OM ′) ₂ and —OPO (OM ′) ₂ and a hydroxyl group.

Such a polyurethane resin can be produced, for example, as follows.

Generally, a polyurethane resin is synthesized by reacting a polyisocyanate and a polyol, and as such a component, one having the above polar group or hydroxyl group in the molecule is used. The usable polyol component was synthesized by reacting an organic dibasic acid such as phthalic acid, adipic acid, dimerized linoleic acid, maleic acid and the like with glycols such as ethylene glycol, propylene glycol, butylene glycol and diethylene glycol. Polyester polyol; or s-caprolactam, a-methyl-
Lactone polyester polyols synthesized from lactams such as 1-caprolactam, s-methyl-s-caprolactam, γ-butyrolactam; or polyether polyols synthesized from ethylene oxide, propylene oxide, butylene oxide, etc. , Tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, etc. were reacted to produce urethane polyurethane polyester polyurethane, polyether polyurethane, and polycarbonate polyurethane carbonate carbonated with phosgene or diphenyl carbonate. It These polyurethanes are usually produced mainly by the reaction of polyisocyanates and polyols, and also in the form of urethane resins or urethane prepolymers containing free isocyanate groups and / or hydroxyl groups or containing these reactive end groups. It may be one that does not exist (for example, in the form of urethane elastomer).

Since methods for producing polyurethanes, urethane prepolymers, urethane elastomers, curing cross-linking methods and the like are known, detailed description thereof will be omitted.

It is preferable to set the reaction conditions so that the weight average molecular weight of the polyurethane resin is generally in the range of 5,000 to 150,000 (preferably 10,000 to 60,000).

The content of the above polyurethane-based resin in the copolymer of the repeating unit having a polar group is usually 0.01 to 5
It is preferably within the range of mol% (preferably 0.1 to 2.0 mol%). Further, the hydroxyl group content in the resin, the repeating unit having a hydroxyl group is preferably 0.1 to 20 mol%, 1.0
~ 5.0 mol% is even better.

The binder of the magnetic layer of the present invention is a combination of the above vinyl chloride copolymer and polyurethane resin,
Usually, the vinyl chloride copolymer and the polyurethane resin are preferably used within a weight ratio of 80:20 to 20:80 (preferably 70:30 to 40:60).

Thus, by using a vinyl chloride-based copolymer having a specific polar group (and an epoxy group if necessary) introduced therein and a polyurethane-based resin having a specific polar group introduced therein, vinyl chloride The polar group of the system copolymer, the polar group of the polyurethane resin, and the hydroxyl group act to improve the affinity with the ferromagnetic powder, and the ferromagnetic powder is well dispersed in the magnetic layer. Therefore, since the squareness ratio of the magnetic layer is improved, a good reproduction output is exhibited. Furthermore, since the amount of the ferromagnetic powder dispersed in the form of lumps is small, the ferromagnetic powder is not detached during traveling, and therefore the occurrence of clogging of the magnetic head can be reduced.

In the present invention, in addition to the above-mentioned binder, a conventionally used non-modified vinyl chloride resin, polyurethane resin or polyester resin may be mixed, if necessary.
Further, fibrin resin, phenoxy resin, or thermoplastic resin having a specific usage system, thermosetting resin, reactive resin,
You may use electron beam irradiation hardening type resin etc. together.

In addition to the above magnetic powder and binder, a lubricant (eg, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic fatty acid (eg, stearic acid), fatty acid ester, etc.) is added to the magnetic layer. You can do it. In addition, non-magnetic abrasive particles may also be added, including alumina (α-Al ₂ O ₃ (corundum), etc.), artificial corundum, fused alumina, silicon carbide, chromium oxide, diamond, artificial diamond, garnet. , Emery (main components: corundum and magnetite) are used. The content of this abrasive is preferably 20 parts by weight or less with respect to the magnetic powder,
The average particle size is preferably 0.5 μm or less, more preferably 0.4 μm or less. An antistatic agent such as carbon black may be added to the magnetic layer.

In the magnetic desk according to the present invention, the dry thickness of the magnetic layer is preferably 0.5 to 4.0 μm and 1.0 to 3.0.
μm is even better.

When the undercoat layer 22 is provided below the magnetic layer, the undercoat layer may be formed by coating the above-mentioned various binders.

As the material of the support 21, polyethylene terephthalate, plastics such as polypropylene, metals such as Al and Zn, glass, Si carbide, porcelain, ceramics such as pottery and the like are used.

The present invention may be applied to, for example, a video floppy for an electronic still camera other than the above-mentioned floppy disk.

E. Examples Hereinafter, examples of the present invention will be described.

The components, ratios, operation orders, and the like shown below can be variously changed without departing from the spirit of the present invention. In the following examples, "parts" are all parts by weight. "Actual" indicates an example and "ratio" indicates a comparative example.

After the compositions shown in Table 2 below were dispersed in a sand mill, this coating material was filtered with a 1 μm filter, applied on a support, and subjected to non-orientation treatment and calendar treatment,
After predetermined treatment, a magnetic disk medium was prepared.

On the other hand, a non-woven liner having the composition shown in Table 2 was used on the inner surface of the shell of a 3.5-inch floppy disk, and the magnetic disk medium was loaded into the shell to produce a 3.5-inch floppy disk.

The binders in Table-2 are shown in Table-1 below.

For each floppy disk sample obtained above, 3.
2 in a 5 inch high density floppy disk drive
Recording was performed at 50 KHz, and the running time until the reproduction output reached 60% of the initial output was measured in a cycle thermostat of 5 ° C and 60 ° C, and durability was examined.

In addition, these phippy discs were randomly seeked, and the number of discs in which dropout occurred after applying vibration for 1 hour using 100 discs was determined as reliability.

The playback output is mounted on a 3.5-inch high-density floppy disk drive and recorded and played back at 250 KHz.
The output of Comparative Example-7 was measured as 100%.

 The results are shown in Table-2.

From these results, it is possible to provide a high-output disc with excellent reliability and high durability for a long time by producing a floppy disc according to the present invention.

F. Effect of the Invention As described above, the present invention contains 30% by weight or more of polyester and / or polyacrylonitrile fiber in the liner, so that the braid such as rayon that constitutes the non-woven fabric is bonded and released. Not only does it have a preventive effect, but the same fiber alone can form a non-woven braid and exhibit sufficient cleaning properties.

Further, by using a vinyl chloride copolymer having a specific polar group such as a sulfo group introduced therein and a polyurethane resin having a specific polar group and a hydroxyl group introduced therein, a vinyl chloride copolymer can be obtained. The polar group and the polar group and hydroxyl group of the polyurethane-based resin act to improve the affinity with the ferromagnetic powder, and the ferromagnetic powder is well dispersed in the magnetic layer to increase the density and output. Can be realized. Moreover, the original physical properties of both resins can be effectively exhibited.

[Brief description of the drawings]

The drawings are for explaining the present invention. FIG. 1 is an enlarged sectional view of a part of a case where a magnetic disk medium is housed by joining upper and lower halves (a sectional view taken along line I-I in FIG. 3). FIG. 2 is a cross-sectional view of an example of a magnetic disk medium, and FIG. 3 is a plan view of each inner surface showing both halves separated. In the reference numerals shown in the drawings, 1 ... magnetic disk 2 ... upper half 3 ... lower half 4, 5 ... liner 4a, 4b, 5a, 5b ... junction (peripheral part) 10 ... magnetic disk medium 11 ... Lifter 12 ... Rib 21 ... Support 24 ... Magnetic layer.

Claims (1)

(57) [Claims] 1. A magnetic disk in which a disk-shaped magnetic recording medium having a magnetic layer containing magnetic powder and a binder and a liner in contact with the magnetic layer are arranged in a case, wherein a polyester fiber and / or a polyester fiber is used. The liner is formed by a non-woven fabric containing 30% by weight or more of polyacrylonitrile fiber (containing 30% by weight or more when both fibers are contained), and as the binder, a sulfo group, a phospho group, a carboxyl group and these Vinyl chloride resin containing at least one selected from the group consisting of alkali metal salts of groups, and at least one selected from the group consisting of sulfo groups, phospho groups, carboxyl groups and alkali metal salts of these groups A magnetic disk in which a polyurethane resin containing a hydroxyl group and a hydroxyl group is used in combination.