JPH0442434A - Production of disk shape magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability and to maintain good electromagnetic conversion characteristics by carrying out a process of lubricant impregnation before the curing process in the production process including lubricant impregnation, punching into a disk form, and curing of the magnetic layer. CONSTITUTION:In the production process including lubricant impregnation, punching into a disk form, and curing of the magnetic layer, the magnetic layer is impregnated with a lubricant before curing process. Since the binder in the magnetic layer is not cured nor has crosslinking structure, enough amt. of the lubricant can intrude into the magnetic layer. Then when cured in the next process, a proper amt. of the lubricant can be held in the crosslinked structure. By this method, durability of the medium can be improved and the obtd. disk type magnetic recording medium has high electromagnetic conversion characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method of manufacturing a disk-shaped magnetic recording medium.

BACKGROUND ART Conventionally, as a disk-shaped magnetic recording medium for still videos, computers, etc., there has been a magnetic recording medium in which a magnetic layer in which ferromagnetic alloy powder is dispersed in a binder is coated on a non-magnetic support. It is used.

Such a disk-shaped magnetic recording medium, such as an electronic still video floppy disk, is usually manufactured as follows. That is, after preparing a magnetic paint containing magnetic powder (ferromagnetic metal powder), this magnetic paint was filtered to remove poorly dispersible components, and a polyethylene terephthalate film (thickness = 32 μm) was prepared.
The polyisocyanate in the magnetic layer is coated on both sides of the magnetic layer using a reverse roll coater so that the dry thickness of each layer becomes 3.5 μm, and after removing the solvent under heating, a calender treatment is performed. Heat curing for compounds (
After performing a lubricant impregnation process on the magnetic layer, the magnetic layer is punched out into a disk shape of 2 inches in diameter to produce an electronic still video floppy. Before the above punching process (after the lubricant impregnation process), a burnishing (surface hardening process) is performed.

However, as a result of the inventor's studies on the above-mentioned manufacturing method, he discovered that there are the following drawbacks. That is, in the conventional method, the durability of the magnetic layer is insufficient because curing is performed before the lubricant impregnation step. This is thought to be because a complex cross-linked structure is formed between the binder molecules in the magnetic layer by curing, and the lubricant molecules cannot sufficiently penetrate into the cross-linked structure in the next lubricant impregnation step. It will be done. Therefore, a sufficient amount of lubricant is not impregnated into the magnetic layer, resulting in insufficient lubricant seeping onto the surface of the magnetic layer during use of the medium, making it unable to withstand the friction with the head etc. , the coefficient of friction also increases, and durability tends to decrease.

OBJECT OF THE INVENTION An object of the present invention is to provide a method for manufacturing a disk-shaped magnetic recording medium with improved durability and high electromagnetic conversion characteristics.

20 Structure of the Invention That is, the present invention has a step of impregnating a magnetic layer with a lubricant, a step of punching into a disk shape, and a step of curing the magnetic layer, and the step of impregnating the magnetic layer with a lubricant is performed before the curing step. The present invention relates to a method for manufacturing a disk-shaped magnetic recording medium.

The method for manufacturing a disk-shaped magnetic recording medium according to the present invention basically involves applying, for example, a magnetic paint, drying, and then calendering, followed by at least a lubricant impregnation step, a disk-shaped punching step, and a curing step for the magnetic layer. When carrying out this process, a lubricant impregnation process is performed before the curing process.

That is, the above-mentioned coating, drying, and calendering may be performed in a known order and by a known method, but in the subsequent steps, the magnetic layer is impregnated with a lubricant (for example, a lubricant is impregnated into the magnetic layer before the curing step). lubricant is overcoated on the surface of the magnetic layer), the binder in the magnetic layer is in an uncured state and has not yet formed a crosslinked structure.Therefore, the lubricant is present in a sufficient amount in the magnetic layer. and will be moderately retained within the cross-linked structure upon subsequent curing. In other words, the lubricant molecules are held by the cross-linked structure, and when a shortage occurs on the surface of the magnetic layer, the lubricant oozes out from inside the magnetic layer. This allows the Ha coefficient of the magnetic layer to be kept small during use, and it is possible to achieve durability that is more than sufficient to withstand abrasion.

The main steps of the method according to the invention are illustrated in Figures 1 to 3.
There are combinations of steps illustrated in the figure. In FIG. 1, after the lubricant impregnation step, punching into a disk shape and further curing are performed. FIG. 2 shows a method in which curing is performed before punching in FIG. 1, and FIG. 3 shows a method in which punching is performed in FIG. 1 before lubricant impregnation.

Either method has the order of lubricant impregnation → curing according to the present invention, so no matter what point the punching is performed, a sufficient amount of lubricant can be impregnated into the magnetic layer as described above. , durability can be improved. However, if the punching process is performed after the lubricant impregnation process, the lubricant impregnation work (overcoat) will be easier and mass productivity will be better.

Next, in the above, lubricants used in the lubricant impregnation step include fatty acid esters (e.g. isooctyl palmitate), -basic fatty acids (e.g. stearic acid),
silicone oil, graphite, molybdenum disulfide,
Examples include tungsten disulfide, but fatty acid esters are preferred.

The lubricant can be impregnated into the magnetic layer by dissolving the lubricant in a solvent to a predetermined concentration, applying this solution by roll coating, etc., and drying it at a predetermined temperature. 20 equipment is 20~60
屹/d is better, 30-50a/cj is even better, and
The impregnation of the lubricant after punching may be performed using a spin cord that applies the lubricant while rotating the disk body.

Further, the above-mentioned punching step can be performed by a method (punching) of punching the medium semi-finished product with a die while conveying it, and the method itself is known.

Furthermore, the above-mentioned curing is a heating step to completely react the unreacted curing agent in the magnetic layer with the binder to form a crosslinked structure.
It is preferable to carry out the heating for 2 hours, preferably at 65 to 70°C for 48 to 60 hours.

Further, the above-mentioned application, drying, and calendering of the magnetic paint can be performed by known methods.

22, Fe-Aj! as the magnetic powder of the magnetic layer! It is better to use metal magnetic powder (ferromagnetic alloy powder) such as Fe, Ni, Co, etc., but these ferromagnetic metal powders include Fe, Ni, Co,
e-Al system, Fe-Aj! -Ni series, Fe-Al! -C
o series, Fe-Ni-3i series, Fe-An! -Zn-based, F
e-Ni-Co system, Fe-Mn-Zn system, Fe-Ni system, Fe-Ni-Af system, Fe-Ni-Zn system,
)'e-Ni-Mn system, Fe-Co-N1-P system, C
Examples include ferromagnetic powders such as o-Ni-based metal magnetic powders containing Fe, Ni, Co, etc. as main components. Among them, Fe-Al! is particularly useful in terms of corrosion resistance and dispersibility. ,,Fe-Al-N
i.

Fe-Aj! -Zn, Fe-Aj! -CoSFe-Ni
.

Fe-N1-AfSFe-Ni-Zn, Fe-N1-A
j! -31-Zn, F e -N i -AI! -3
i-Mn type metal magnetic powder is preferred.

These metal magnetic powders have high saturation magnetization and coercive force (and are excellent for high-density recording).They also have a specific surface area of 40rrf/
By using the above-mentioned ferromagnetic alloy powder having a specific surface area (BET value) of 42 rrf/g or more, particularly 42 rrf/g or more, the electromagnetic conversion characteristics are greatly improved. Further, the coercive force (coercive force) of the ferromagnetic metal powder is usually 10,000 e or more (preferably 12,000 e or more).

Further, there is no particular restriction on the shape of the magnetic powder that can be used in the present invention, and for example, acicular, spherical, etc. can be used.

Since the above magnetic powder is a metal magnetic powder, it is difficult to disperse it sufficiently, but this can be sufficiently prevented by using the following polyurethane resin as a binder in the magnetic layer, which improves dispersibility. be able to.

That is, the polyurethane resins used are 505M, 0305M, PO(OM')*, -
0PO(OM')* (However, M is hydrogen or an alkali metal such as lithium, potassium, and sodium, and M' is an alkali metal such as hydrogen, lithium, potassium, and sodium.)
It is preferable for the magnetic powder to contain one or more types of negative functional groups (hydrophilic polar groups).These polar groups in the molecule improve the compatibility between the resin and the magnetic powder. It is possible to improve the dispersibility and prevent agglomeration of the magnetic powder, thereby further improving the stability of the coating liquid and, in turn, improving the durability of the medium.

Regarding the synthesis of such polyurethane resins, a commonly used method of reaction between polyosyl and polyisocyanate can be used. As the polyol component, generally used is a polyester polyol obtained by the reaction of a polyol and a polybasic acid. Therefore, by using the above polyester polyol having a polar group as a raw material, a polyurethane having a polar group can be synthesized.

Usable polyols include dibasic acids such as phthalic acid, acihinic acid, trimerized lyluic acid, and maleic acid, and glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol, or trimethylolpropane, A polyester polyol synthesized by reaction with polyhydric alcohols such as hexanetriol, glycerin, trimethylolethane, and pentaerythritol, or any two or more polyols selected from these glycols and polyhydric alcohols; Or S-caprolactam, α-
Lactone polyester polyols synthesized from lactams such as methyl-1-caprolactam, S-methyl-8-caprolactam, T-butyrolactam; or polyether polyols synthesized from ethylene oxide, propylene oxide, butylene oxide, etc. The polyol is tolylene diisocyanate) (TD
I), hexamethylene diisocyanate) (HMD Ri,
Methylene diisocyanate, metaxylylene diisocyanate, diphenylmethane-4,4' diisocyanate (MDI), 1,5-naphthalene diisocyanate (N
DI), Trijinshii.

It is reacted with isocyanate compounds such as isocyanate (TODI) and lysine isocyanate methyl ester (LDI), thereby synthesizing urethanized polyester polyurethane, polyether polyurethane, and polycarbonate polyurethane carbonated with phosgene or diphenyl carbonate. These polyurethanes are usually produced primarily by the reaction of polyisocyanates and polyols and are also in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups, or containing reactive end groups of these. (For example, urethane elastomer type ○) may be used.

Since the methods for producing polyurethane, urethane prepolymers, urethane elastomers, curing and crosslinking methods, etc. are well known, detailed explanation thereof will be omitted.

Alternatively, for example, a polyurethane resin into which polyfunctional -OH has been introduced is produced, and this polyurethane resin is reacted with a compound containing a polar group and chlorine described below (dehydrochloric acid reaction) to impart a polar group to the polyurethane resin. You can use the method of introduction.

Cj!　CHz　CHz　S　Os　M.

CI C) fg CHg OS Os M.

CICHt COOM CICHt PO(OM' )z It is preferable to set the reaction conditions so that the weight average molecular weight of this polyurethane resin is generally within the range of 10,000 to 150,000 (preferably 20,000 to 60,000). .

In addition, the above polyurethane resin usually has a content of repeating units having polar groups in the copolymer from 0.01 to
The content is preferably within the range of 5 mol% (preferably 0.1 to 2.0 mol%).

Regarding the introduction of polar groups into polyurethane, please refer to Japanese Patent Publication No. 5B-41565, Japanese Patent Publication No. 57-92422, Japanese Patent Publication No. 57-92423, Japanese Patent Publication No. 59-8127, Japanese Patent Publication No. 59-5.
No. 423, No. 59-5424, No. 62-121923
There are descriptions in publications such as No., and these can also be used in the present invention.

The above-mentioned polyurethane resin can further improve the abrasion resistance of the magnetic layer and provide appropriate flexibility. and,
When a vinyl chloride resin is used in combination with this polyurethane resin, the magnetic powder can be dispersed well and the mechanical strength of the magnetic layer can be improved. In this case, the weight ratio of vinyl chloride resin and polyurethane resin is usually 80:20 to 20:80 (preferably 70:3).
It is preferable to use it within the range of 0 to 40:60).

Usable vinyl chloride resins can be synthesized by adding to a copolymer containing an OH group, such as a vinyl chloride-vinyl alcohol copolymer, by reaction with a compound containing a polar group and a chlorine atom, as shown below. can do.

CjICHt CHt SOs M.

CI　CHz　CHz　OS　Os　M.

CjICHl PO(OM')□, CjICHt C00M CI CHz CHz S Os N
Taking a as an example, −(C11*CH) + Cj! (CHHz)
5OsNaH → −(CB, −CI) −+ ICfQ
(CHt)g-SOsNa.

There is also a method of copolymerizing all of them with copolymerizable monomers. That is, a predetermined amount of a reactive monomer having an unsaturated bond into which a repeating unit containing a polar group is introduced is placed in a reaction vessel such as an autoclave;
For example, BPO (benzoyl peroxide), AIBN
(Azobisisobutyronitrile) and other radical polymerization initiators, redox polymerization initiators, anionic polymerization initiators, cationic polymerization initiators, and other polymerization initiators.
For example, specific examples of reactive sulfonic acids for introducing sulfonic acid or its salts include unsaturated hydrocarbon sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, and P-styrene sulfonic acid; Examples include salt.

Furthermore, sulfoalkyl esters of acrylic acid or methacrylic acid such as 2-acrylamido-2-methylpropanesulfonic acid, (meth)acrylic acid sulfoethyl ester, (meth)acrylic acid sulfopropyl ester, salts thereof, or acrylic acid. -2-ethyl sulfonate, etc. can be mentioned.

When introducing carboxylic acid or its salt (introduction of COOM), (meth)acrylic acid, maleic acid, etc. are used, and when phosphoric acid or its salt is introduced, (meth)acrylic acid-2-phosphate ester is used. good.

Further, it is preferable that an epoxy group is introduced into the vinyl chloride copolymer.The introduction of the epoxy group improves the thermal stability of the vinyl chloride copolymer. When introducing an epoxy group, the content of repeating units having an epoxy group in the copolymer is preferably 1 to 30 mol% (more preferably 1 to 20 mol%).The monomer for introducing is glycidyl. Regarding the preferred use of acrylate, Japanese Patent Application Laid-open Nos. 57-44227 and 58-1
No. 08052, No. 59-8127, No. 60-1011
No. 61, No. 60-235814, No. 60-23830
No. 6, No. 60-238371, No. 62-121923
No. 62-146432, No. 62-146433, etc., and these can be used in the present invention.

In the present invention, in addition to the binder described above, conventionally used unmodified vinyl chloride resins, polyurethane resins, or polyester resins may be used in combination or alone, and cellulose resins and phenoxy resins may also be used, if necessary. Resins, thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, etc. that have a specific usage method may be used in combination.

In addition to the magnetic powder and binder described above, the magnetic layer contains a lubricant (
For example, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, -basic fatty acids (e.g. stearic acid), fatty acid esters, etc.) may be added.
In addition, alumina (α-Af2
03 (corundum), etc.), artificial corundum, fused alumina, silicon carbide, chromium oxide, diamond, α-
A small amount of Fetus (hematite), artificial diamond, garnet, emery (main components: corundum and magnetite), etc. may also be used in combination.An antistatic agent such as carbon black may be added to the magnetic layer.

Solvents that can be used in magnetic paints include ketones (eg methylethylketone), ether I! (e.g. diethyl
ether), esters (for example, ethyl acetate), aromatic solvents (for example, toluene), alcohol M (for example, methanol), and these can be used alone or in combination.

The disk-shaped magnetic recording medium obtained by the method of the present invention has a magnetic layer 24 provided on both sides of a non-magnetic support 210 via an intermediate layer 22 if necessary, as shown at 10 in FIG. 4, for example. be. If necessary, an overcoat layer (not shown) may be further provided on the magnetic layer.

The dry film thickness of the magnetic layer 24 is preferably 0.5 to 4.5 μm, more preferably 3.0 to 4.0 μm.

When the intermediate layer 22 is provided under the magnetic layer, a subbing layer may be formed by coating the various binders described above. It is provided for the purpose of improving adhesiveness, improving conductivity, etc.

Examples of materials for the support 21 include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonate. be able to. Furthermore, Cu,
Non-magnetic metals such as Af and Zn, glass, so-called new ceramics, etc. can also be used.

The thickness of the support formed using these materials is usually 1
It is within the range of 0 to 80 μm.

A magnetic layer is provided on at least one surface of the support, but usually a magnetic layer is also provided on the other surface as described above. By providing magnetic layers on both sides in this manner, deformation (curling) of the magnetic disk can be effectively prevented. However, it is also possible to prevent curling by providing a back coat layer on the back surface.

Note that the present invention may be applied to magnetic disks such as video floppies and data floppies for electronic still cameras, for example.

E, Example The present invention will be explained in detail below.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention.

(Example 1) The ingredients shown below were sufficiently mixed and dispersed using a disper kneader and a ball mill, and then, immediately before coating, a polyisocyanate compound (coronate was added to Nippon Polyurethane).
Magnetic paint [I] was prepared by adding and mixing 5 parts by weight of Magnetic paint [I].

"One Magnetic Bean llLu" - 100 parts by weight of iron-aluminum ferromagnetic alloy powder (aluminum content: 4% by weight, specific surface area: 4 ft/g, coercive force (Hc): 12500 e-polyurethane resin 6 parts by weight (Toyobo Co., Ltd.) Company-made U
R-8200 Ni So, containing Na group) Vinyl chloride copolymer 10 parts by weight (MRIIO Ni SO, Nippon Zeon, containing Na group) Alumina oxide Af! 10 parts by weight of O3 (average particle size = 0.4 μm) 0.5 parts by weight of carbon black (
Average particle size: 55 nm BET specific surface area: 32 nr/g DBP oil absorption: 180 d/100 g) Oleic acid 1 part by weight Isooctyl palmitate 1 part by weight cyclohexanone
100 parts by weight methyl ethyl ketone
100 parts by weight toluene
100 parts by weight of the obtained magnetic paint was filtered to remove poorly dispersed components, and coated on both sides of a polyethylene terephthalate film (thickness 232 μm) using a reverse roll coater so that the dry thickness of each layer became 3.5 μm. After coating and removing the solvent under heating, calendering was performed.

Next, a 1% solution of isooctyl palmitate (solvent: n-hexanone) is applied to the magnetic layer using a reverse roll coater, and dried at 90°C for 10 seconds. impregnated with palmitate). After this lubricant impregnation step, the polyisocyanate compound in the magnetic layer was heat-cured by punching into a disk shape of 2 inches in diameter and heating at 65° C. for 50 minutes. Thereafter, it was placed in a cassette to produce an electronic still video floppy.

(Example 2) In Example 1, after calendering, a lubricant impregnation step was performed in the same manner, and then heat curing was performed for the polyisocyanate compound. A shape was punched out to produce an electronic still video floppy.

(Example 3) In Example 1, after performing the calender treatment, a disc having a diameter of 2 inches was punched in the same manner, followed by a lubricant impregnation step. ) and manufactured an electronic still video floppy.

(Comparative Example 1) In Example 1, after calendering, the polyisocyanate compound was heated and cured in the same manner, and then punched into a disc shape with a diameter of 2 inches, followed by a lubricant impregnation step. An electronic still video floppy was manufactured.

(Comparative Example 2) In Example 1, after calendering, heat curing for the polyisocyanate compound was carried out in the same manner, followed by a lubricant impregnation process, and then a disk-shaped product with a diameter of 2 inches was prepared. It was punched out to produce an electronic still video floppy.

(Comparative Example 3) In Example 1, after performing the calender treatment, it was similarly punched out into a disk shape with a diameter of 2 inches, followed by heat curing (curing) for the polyisocyanate compound, and then a lubricant impregnation step. and manufactured an electronic still video floppy.

The following performance evaluations were performed on each of the above video floppies, and the results are shown in the table below.

No Seek Commercially available electronic still video floppy recorder (AG8
00, made by Hiroshi Denki Sangyo ■), the image signal is
In the still mode of the electronic still video floppy recorded on all 0 tracks, playback of 4 seconds for each track is repeated continuously from 1 to 50 tracks, and the playback output increases from the initial value to 3.
The time until the image quality decreased by dB or until image quality deterioration such as dropout occurred in the reproduced image was measured. The results are shown in the table below.

In the same table, 300 hours or more means that the reproduction output did not decrease by 3 dB and the image quality did not deteriorate even after 300 hours of reproduction.

A 7 MHz sine wave signal was recorded using M VP-5500 manufactured by Sony Corporation, and the reproduced RF output was measured. The measured reproduced RF outputs are listed in the table below as relative values to the gold reference values. The larger the RF output value, the better the electronic still video floppy.

From this result, by constructing a disk-shaped medium based on the present invention, it is possible to provide a magnetic disk with good durability and high electromagnetic conversion characteristics.

1. Effects of the Invention As described above, in the present invention, when carrying out the lubricant impregnation process, the punching process into a disk shape, and the curing process for the magnetic layer, the lubricant impregnation process is performed before the curing process. Since the binder in the magnetic layer is in an uncured state and has not yet formed a crosslinked structure, a sufficient amount of lubricant can penetrate into the magnetic layer, and crosslinking occurs during subsequent curing. It will be reasonably retained within the structure.

Therefore, the coefficient of friction of the magnetic layer can always be kept small while the medium is in use, and durability can be achieved that is more than sufficient to withstand abrasion.
Moreover, electromagnetic conversion characteristics can also be maintained favorably.

[Brief explanation of drawings]

The drawings are for explaining the present invention, and include FIG.
FIGS. 2 and 3 are charts showing the main flow of the manufacturing process of a disk-shaped medium, and FIG. 4 is a sectional view of an example of the disk-shaped medium according to the present invention. In addition, in the reference numerals shown in the drawings, 21...Nonmagnetic support 22...Intermediate layer 24...Magnetic layer. Agent: Hiroshi Osaka, Patent Attorney (Voluntary) Procedural Amendment July 20, 1990, 1990 Patent Application No. 150398 2, Name of Invention Method for Manufacturing Disc-shaped Magnetic Recording Media 3, Relationship with the Amendment Person Case Patent applicant address: 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name:
(127) Konica Co., Ltd. 4, Agent address: FINE Building e, 2-4-11 Shibasaki-cho, Tachikawa-shi, Tokyo 0425-24-54114156゜7゜Contents of the amendment in the detailed description of the invention in the specification subject to the amendment

Claims (1)

[Claims] 1. Manufacture of a disk-shaped magnetic recording medium that has a lubricant impregnation step for the magnetic layer, a punching step into a disk shape, and a curing step for the magnetic layer, and the lubricant impregnation step is performed before the curing step. Method.