JPS6210782B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to high precision abrasive tapes. Conventionally, polishing tapes containing abrasives or containing a mixture of soft particles and hard particles have been used, but the amount of grinding of the head varies, and the surface roughness of the head after grinding is poor. There were also problems in that chipping was more likely to occur on the end surface of the head, and the head was more likely to be damaged. The main purposes of conventional abrasive tapes were: 1. Finishing the head surface, 2. Creating the shape of the tip of the head, and 3. Eliminating chipping of the head. In both of these cases, the shortest recording wavelength is at most 2
It was effective in the case of μ. In contrast, recent videotapes (e.g. β-
In 1/2-inch video cassette formats such as Max, β-Format, and VHS systems, the recording wavelength is 1μ, which is half of the conventional recording wavelength, and the performance required of the head has accordingly increased significantly. . For this reason, the quality of magnetic heads is no longer satisfactory with the conventional finishing method using abrasive tape. The present invention relates to a method for manufacturing an abrasive tape necessary for manufacturing a high-density recording head of about λ=1 μ. For this head, the finished surface should be 100 Å or less, preferably 50 Å or less, whereas conventionally it was about 500 Å, the tip shape should be free of burrs and scratches, and there should be no chipping (more than 5 μ in length in the width direction of the head). thing)
It is necessary to increase the precision, such as by setting a value of about 2 to 0, and for this purpose, an extremely high-precision abrasive tape is required. As a way to deal with this, it may be possible to change the composition or material of the head, but since the head width has become smaller and the recording density has increased, it is difficult to change the head itself any further in terms of magnetic properties. The head used is single crystal: Fe ₂ O ₃ /
MnO/ZnO (53/32/15), hot pressed:
There are Fe ₂ O ₃ /MnO/ZnO (53/25/22), etc., and these heads used to have very different polishing characteristics due to the small amount of hot press polishing, and were also prone to chipping. However, this difference has recently narrowed, and if hot press polishing is successful, single crystal heads can also be polished. Therefore, the polishing of hot-pressed ferrite will be described below. As a result of repeated research by the present inventors on abrasive tapes suitable for polishing such recent heads, we found that abrasives such as Al ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , and α-
Among the many materials such as Fe ₂ O ₃ , diamond, ZnO ₂ , TiO ₂ , etc., the ones with a good surface finish and low price are α-
It was found that the combination of Fe ₂ O ₃ / Cr ₂ O ₃ was required, the total thickness of the polishing tape was 10 to 100 μ, and the unevenness of the surface of the polishing tape was 0.1 mm or less. This has led to the present invention. Regarding abrasives, Cr ₂ O ₃ increases the amount of polishing, α-Fe ₂ O ₃ has the effect of improving the surface properties of the polishing tape and the finished surface of the head, and the mixing ratio ( α−Fe ₂ O ₃ /Cr ₂ O ₃ ) is 1/9 to 9/
1, preferably 1/2 to 2/1. The thickness should be 10 to 100 microns, preferably 20 to 40 microns, because the thinner the polishing amount will be, and the thicker the head will be chipping. If the size of the abrasive is too large, the unevenness of the abrasive tape will become large and the finished head surface will deteriorate, so the size of the abrasive is 100 μm or less, preferably 5 μm or less. If the irregularities on the surface of the polishing tape are large, chips may easily occur in the head, so
Below, preferably 10μ or less, more preferably 1μ
It is as follows. The polishing tape of the present invention is produced by coating a binder, an abrasive, and other additives dissolved in an organic solvent on a support. As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used. As a thermoplastic resin, the softening temperature is 150℃ or less,
Average molecular weight is 10000~200000, degree of polymerization is about 200~
500, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer,
Vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic Acid ester styrene copolymer, urethane elastomer,
Polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymer,
Polyester resins, chlorovinyl ether acrylic acid ester copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof are used. Examples of these resins are given in Japanese Patent Publication Nos. 37-6877 and 39.
−12528, No. 39-19282, No. 40-5349, No. 40
−20907, No. 41-9463, No. 41-14059, No. 41
−16985, No. 42-6428, No. 42-11621, No. 43
−4623, No. 43-15206, No. 44-2889, No. 44
−17947, No. 44-18232, No. 45-14020, No.
No. 45-14500, No. 47-18573, No. 47-22063,
No. 47-22064, No. 47-22068, No. 47-22069
No. 47-22070, No. 47-27886, etc. The thermosetting resin or reactive resin has a molecular weight of 2×10 ⁵ or less in the state of a coating solution, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example,
Phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy-polyamide resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylate These include mixtures of acid salt copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanates, polyamine resins, and mixtures thereof. Examples of these resins are given in Japanese Patent Publication Nos. 39-8103 and 40.
-9779, 41-7192, 41-8016, 41-
No. 14275, No. 42-18179, No. 43-12081, No. 44
-28023, 45-14501, 45-24902, 45-24902,
No. 46-13103, No. 47-22065, No. 47-22066,
No. 47-22067, No. 47-22072, No. 47-22073
No. 47-28045, No. 47-28048, No. 47-
It is described in publications such as No. 28922. These binders may be used alone or in combination, and other additives may be added. The mixing ratio of the abrasive powder and the binder is in the range of 10 to 200 parts by weight based on 100 parts by weight of the abrasive powder. Additives include dispersants, lubricants, and the like. Support materials include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, and celluloses such as cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, and cellulose acetate propionate. Derivatives, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide and polyamideimide, as well as non-magnetic metals such as aluminum and copper, and ceramics such as glass, pottery and porcelain, depending on the application. , paper, baryta, or paper coated or laminated with α-polyolefin having 2 to 10 carbon atoms, such as polyethylene, polypropylene, or ethylene-butene copolymer, can also be used. These supports may be transparent or opaque depending on the intended use of the abrasive tape. Methods for applying the abrasive layer onto the support include air doctor coating, blade coating, air knife coating, squeeze coating, dip coating, reverse roll coating, and transfer coating.
Roll coat, gravure coat, kiss coat,
Cast coating, spray coating, etc. can be used, and other methods are also possible, and detailed explanations of these can be found in "Coating Engineering" published by Asakura Shoten.
It is described in detail on pages 253 to 277 (published on March 20, 1972). Example 1 A 7μ abrasive layer was coated on a 15μ polyethylene terephthalate base using coating composition (). After that, slit the tape into 1/2 inch pieces, wrap this abrasive tape in place of the tape in a VHS/VTR tape/cassette, and polish the head set in the VTR for 1 minute to measure the amount of wear on the head and the finish of the head. We investigated the unevenness and chipping on the end face of the head. The results are shown in Table 1, 1001~
Shown as 1006. The head is made of the aforementioned hot-pressed ferrite. Coating composition () Abrasive material (A)/Abrasive material (B) Shown in Table 1. Total 300g Vinyl chloride-vinyl acetate copolymer (copolymerization ratio 87:13, degree of polymerization 350) 22.5g Polyester polyol (*) 12g Soybean lecithin 3g Silicone oil (dimethyl polyol) siloxane)
………2g Polyisocyanate (75% by weight ethyl acetate solution of the reaction product of 3 moles of 2,4-tolylene diisocyanate compound and 1 mole of trimethylolpropane) …4.5g Methyl ethyl ketone …400g Toluene … ...900g * 1 mol of adipic acid and 1 mol of diethylene glycol
Mol and 0.06 mole of trimethylolpropane reaction product Viscosity (75℃): 1000 cp, specific gravity 1.18, OH value: 60, acid value: 2 or less Example 2 Using coating composition (), the base thickness of polyethylene terephthalate was changed. , we looked at the effect of the total thickness of the abrasive tape. The results are shown in Table 1 as 2001-2006. The head polishing conditions were the same as in Example 1. Coating liquid composition () Abrasive material (A)/(B) (see Table 1) A+B=300g Vinyl chloride-vinyl acetate copolymer (copolymerization ratio 87:13, degree of polymerization 380) 28.4g Polyester Polyurethane (reaction product of polyester with terminal hydroxyl groups consisting of butane diol and adipic acid and 2,4-diphenylmethane diisocyanate, molecular weight approximately 40,000) 13g Carbon black (average particle size 2μ)
………22.5g Amyl stearate……1.2g Oleic acid……3g Isocyanate compound (3 moles of 2.4-
75% by weight ethyl acetate solution of reaction product of tolylene diisocyanate compound and 1 mol of trimethylolpropane) 17g Nitrile butadiene rubber (NBR) 7.1g Butyl acetate 900g Example 3 Coating composition ( ) was used to make polishing tapes by changing the particle size of the abrasive, and the polishing conditions were the same as in Example 1.
Similarly, we investigated the effect of size. Results first
Shown in 3001 to 3005 of the table. Coating liquid composition () Abrasive material (see Table 1) (A) + (B) = 300g Vinyl chloride vinylidene chloride copolymer (copolymerization ratio = 7:3, degree of polymerization = 400)
………22g Epoxy resin (reaction product of bisphenol A and epichlorohydrin, molecular weight =
900, epoxy equivalent = 460-520, hydroxyl group content = 0.29%, Shell Oil Co Epicote 1001) ......16g Silicone oil (dimethylpolysiloxane)
......3.0g isocyanate compound (3 moles of 2,4-
75% by weight solution of the reaction product of tolylene diisocyanate compound and 1 mole of trimethylolpropane in ethyl acetate, Bayerz
AG Desmodur L-75) 21g Butyl acetate 900g

【table】

[Table] The following can be seen from the data in Table 1. 1 Cr ₂ O ₃ alone has poor surface properties and chipping of the head. 2. The amount of polishing is small when only α-Fe ₂ O ₃ is used. 3. When α-Fe ₂ O ₃ /Cr ₂ O ₃ is in the range of 1/9 to 9/1, a head with excellent surface properties, chipping, and polishing amount can be obtained. 4. When the total thickness of the abrasive tape is between 10 and 100 microns, the head has excellent properties. 5. If the surface irregularities are 100μ or less, chipping can be prevented. When the polishing tape of the present invention is calendered and used, the rarely occurring convex portions of 100μ or more are eliminated, the polishing effect is improved, and the precision of the finished surface of the head is improved. Furthermore, when heated to a temperature of 30° C. or higher for 1 hour, sharp protrusions disappear and an abrasive tape with fewer particles falling off is obtained. Further, within the scope of the present invention, by using abrasive tapes with different sizes of abrasive materials, it is possible to carry out polishing from rough finishing to finishing sequentially.

Claims (1)

[Claims] 1 In a polishing tape consisting of a support and a polishing layer, a combination of Cr ₂ O ₃ and α-Fe ₂ O ₃ in a mixing ratio of 1:9 to 9:1 is used as the polishing material, and the total thickness is 10 to 10. An abrasive tape having a diameter of 100μ and an unevenness on the surface of the abrasive tape of 0.1 mm or less.