JPH0679636A - Abrasive tape - Google Patents

Abstract

PURPOSE:To provide an abrasive tape optimum for the finishing work of a magnetic head and the like of a VTR or a high-grade audio deck, which can remarkably improve the output of the magnetic head after the grinding. CONSTITUTION:In an abrasive tape, two layers of abrasive layers mainly composed of abrasive grains and binder resin are provided on a flexible support element. The mean grain diameter A of the abrasive grain, which is included in the first abrasive layer positioned as the top layer, is set smaller than the mean grain diameter B of the abrasive grain, which is included in the second abrasive layer positioned just under the first abrasive layer. Furthermore, the relationship between the mean grain diameters A, B is desirably set so as to satisfy the expression (B/A)<=0.5 to achieve the purpose effectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing tape used for polishing various objects such as polishing of a magnetic head of a magnetic recording / reproducing apparatus, burnishing, texture, etc. The present invention relates to a polishing tape used for finish polishing of heads and the like.

[0002]

2. Description of the Related Art A magnetic head of a VTR or a high-quality audio deck is required to have a smooth tape sliding surface. Therefore, when a magnetic head is manufactured, an abrasive tape is generally used to smooth the tape sliding surface. . Such a polishing tape is prepared by coating a coating solution obtained by kneading abrasive particles and a binder resin on a support and drying the coating solution to form a polishing layer. Since it is flexible, it can fit the curved shape of the tape contact surface of the magnetic head, and this surface can be precisely polished.

With the recent trend toward higher density recording for magnetic recording, the magnetic head is required to have a low surface hardness and an extremely smooth surface instead of a ferrite magnetic head having a high surface hardness. The use of alloy-based magnetic heads such as is increasing.
Therefore, although high smoothness is required as a magnetic head for high-density recording, it is easily scratched, and when finishing an alloy-based magnetic head such as sendust, improvement of its accuracy is desired, With conventional polishing tapes, the occurrence of scratches on the magnetic head surface has become a major problem. In addition, as a magnetic head, a laminated magnetic head made of materials having different hardness, for example, a ceramic material, an amorphous alloy material, and a glass material is becoming mainstream for high-density recording. Steps occur at each boundary of
It was difficult to obtain a uniform polished surface.

Various methods have been proposed for using a polishing tape to finish polishing a magnetic head without deteriorating the polishing effect and preventing scratches or adhesion of polishing debris on the surface to be polished. For example, in JP-A-62-92205, an intermediate layer containing a non-magnetic powder and a binder resin is provided, and the average particle size of the non-magnetic powder is the average particle size of the abrasive particles in the polishing layer thereabove. It is disclosed that by making the diameter larger than the diameter, a recess for holding shavings during polishing is formed in the polishing layer to prevent the shavings from falling off and prevent the shavings from damaging the surface of the magnetic head. However, in this method, since the average particle size of the intermediate layer is large, the unevenness of the boundary surface between the intermediate layer and the polishing layer is transferred to the surface of the polishing layer to leave the unevenness, and the abrasive particle size of the surface polishing layer is small. However, there is a drawback that the force locally acts and the alloy magnetic head is damaged. Further, in the comparative example described in the above-mentioned publication, if the abrasive particles are as small as 0.01 to 0.1 μm in one polishing layer without an intermediate layer,
The polishing layer itself is easily scraped, the surface of the polishing layer is flattened,
It is disclosed that the shavings are sandwiched between the polishing tape and the magnetic head, thus damaging the magnetic head.

Further, in Japanese Patent Publication No. 4-22283,
For the purpose of cleaning an alloy-based magnetic head such as sendust, a cleaning tape is disclosed in which a ferromagnetic alloy powder is used as a main abrasive, which is applied, dried, and calendered. The hardness of the ferromagnetic alloy powder is lower than that of the abrasive, and the surface of the cleaning layer is smooth by the calendering treatment, so that it is effective in removing dirt without scratching the alloy magnetic head such as sendust. There is no polishing capacity for finishing. Further, the calendar treatment may cause wrinkles on the polishing tape, resulting in poor productivity. Further, in Comparative Example 6 described in the above publication, an abrasive such as α-alumina, which is a relatively large particle having an average particle diameter of 0.5 μm, is used instead of the ferromagnetic alloy powder, and the surface after coating and drying is used. The center line average roughness is 0.05 μm (cut-off value 0.08 μ
It is disclosed that when the magnetic head is cleaned with a cleaning tape which has been subjected to a calendar treatment so as to be m), the magnetic head is scratched and the magnetic head is also considerably worn. As described above, in the polishing layer coated with the small abrasive particles, the polishing layer itself is scraped and the dust is sandwiched between the polishing tape and the magnetic head, so that the magnetic head is scratched, and the large abrasive particles are large. In the polishing layer coated with, even if the polishing layer surface is flattened in a separate step, since minute protrusions remain on the polishing layer surface, scratches are produced on the magnetic head. There was a limit only by controlling the average particle size of the abrasive particles.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and is particularly suitable as a polishing tape for finishing a magnetic head of a VTR or a high-grade audio deck. On the other hand, it is an object of the present invention to provide a polishing tape that can significantly improve the output of the magnetic head by polishing without scratching and by polishing that uniformly flattens the constituent material of the magnetic head surface.

[0007]

The object of the present invention is to:
In a polishing tape having at least two polishing layers mainly composed of abrasive particles and a binder resin on a flexible support,
The average particle size B of the abrasive particles contained in the second polishing layer located immediately below the first polishing layer is smaller than the average particle size A of the abrasive particles contained in the uppermost first polishing layer. This is achieved by the characteristic polishing tape.

In the polishing tape of the present invention, the uppermost first polishing layer, which is in direct contact with the surface to be polished during polishing, has irregularities on the surface of the second polishing layer containing abrasive particles having a relatively small average particle size. Since it is applied on the top surface, the surface of the first polishing layer becomes finer irregularities due to the leveling effect of the coating liquid, and the surface can be made flat as a whole. Therefore, as compared with the case where the first polishing layer is formed as a single layer on the flexible support, the force can be uniformly applied to the surface to be polished of the magnetic head and the occurrence of scratches can be prevented. By selecting abrasive particles having a relatively large average particle diameter as the abrasive particles of the first polishing layer, it is possible to obtain a sufficient polishing effect with a small force on the surface to be polished. Therefore, it is possible to evenly polish a surface to be polished made of materials having different hardness, such as a laminated magnetic head, and by polishing with the polishing tape of the present invention, It is possible to prevent the occurrence of a step at the boundary between different materials, improve the head touch of the tape, and expect to improve the output of the magnetic head. As described above, in the polishing tape of the present invention, the polishing layer is composed of at least two polishing layers characterized by the average particle diameter of the abrasive particles, and the relationship between the average particle diameter of the abrasive particles is the highest. It is important for achieving the object of the present invention that the average particle diameter of the abrasive particles of the second polishing layer located immediately below is smaller than that of the abrasive particles of the upper first polishing layer. . On the contrary, if the average particle size A of the abrasive particles contained in the first polishing layer is smaller than the average particle size B of the abrasive particles contained in the second polishing layer, minute projections are formed on the surface of the first polishing layer. The rest will damage the magnetic head.

To more effectively achieve the object of the present invention, the average particle size A of the abrasive particles contained in the first polishing layer and the average particle size B of the abrasive particles contained in the second polishing layer are set. Preferably has a relationship of (B / A) ≦ 0.5,
More preferably, (B / A) ≦ 0.4. further,
If two kinds of polishing layers are applied by a so-called wet simultaneous multi-layer coating (wet-on-wet coating method) in which the first polishing layer is coated while the coating layer of the second polishing layer is still wet, Compared to the case of so-called sequential multi-layer coating in which the two polishing layers are dried and cured and then coated with the first polishing layer, the coating layers at the interface of the two layers are integrated to make the surface of the uppermost first polishing layer more It can be made smooth, and the above-mentioned effect comes to work more effectively.

The average particle size of the abrasive particles contained in the first polishing layer used in the polishing tape of the present invention can be selected according to the use of finishing, but is preferably 0.1 to 1.0 μm, more preferably 0. 0.5 to 1.0 μm. The average particle size of the abrasive particles in the second polishing layer may be smaller than the average particle size of the abrasive particles in the first polishing layer, but is preferably 0.03 to 0.2 μm. The average particle size of the abrasive particles in the polishing tape of the present invention is obtained by measuring the size of 500 particles arbitrarily extracted in a transmission electron microscope photograph of 100,000 times and taking the average value.

As the total thickness of the polishing layer used in the polishing tape of the present invention, those having a thickness of 5 to 10 μm that can sufficiently adhere to the head and produce a polishing effect can be used.
When the thickness of the flexible support is 23 μm, the total thickness of the polishing layer is preferably about 5 μm. The total thickness of the first polishing layer is 2.0 μm or less, preferably 1.5 μm or less. In addition, even if two or more layers of the second polishing layer are applied, the smoothness effect of the first polishing layer is considered to be further enhanced, but the performance of the second polishing layer alone is sufficient in view of the current coating technology and production efficiency. Can be achieved and is economical.

The abrasive particles contained in the polishing layer used in the polishing tape of the present invention include, for example, α-alumina,
γ-alumina, fused alumina, silicon carbide, chromium oxide,
Cerium oxide, corundum, diamond, α-iron oxide,
There are emery (main components: corundum and magnetite), garnet, silica stone, silicon nitride, boron nitride, etc., mainly those having a Mohs hardness of 6 or more are desirable, and one or more of them can be used in combination. In particular, the first polishing layer mainly uses the above-mentioned abrasive particles, but the second polishing layer can use various inorganic powders, so that the abrasive particles can be saved.

As the binder resin used in the present invention, various binder resins known in the art can be used. These resins can be used alone or in combination of two or more, and examples thereof include thermoplastic resins, thermosetting resins, and reactive resins.

The thermoplastic resin has a softening temperature of 150 ° C.
Hereinafter, those having an average molecular weight of 10,000 to 300,000 and a degree of polymerization of about 50 to 2,000, for example, (meth) acrylic acid ester, (meth) acrylonitrile,
Polymers of butadiene, vinyl ester, (meth) acrylamide, vinyl chloride, vinylidene chloride, etc., or polymers of their derivatives, or polymers and polymers with monomers copolymerizable therewith, such as vinyl vinyl acetate Polymer, vinyl chloride copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic ester acrylonitrile copolymer, acrylic ester vinylidene chloride copolymer, acrylic ester styrene copolymer, methacrylic Acid ester acrylonitrile copolymer, methacrylic acid vinylidene chloride copolymer, methacrylic acid styrene copolymer, urethane elastomer, nylon-silicone resin, nitrocellulose-polyamide resin, polyfucca vinyl, vinyl chloride Den acrylonitrile copolymer,
Butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, ethyl cellulose, methyl cellulose, propyl cellulose, methyl ethyl cellulose, carboxymethyl cellulose, acetyl) (Eg, cellulose), styrene-butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubber-based thermoplastic resins, and mixtures thereof.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution, and can be reacted such as condensation and addition by heating after coating and drying. Specifically, for example, phenol resin, phenoxy 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, mixture of methacrylate copolymer and diisocyanate prepolymer, mixture of polyester polyol and polyisocyanate , Urea formaldehyde resins, low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate mixtures, polyamine resins, polyimine resins and mixtures thereof.

It is also possible to use a known electron beam curable resin. These examples and the manufacturing method thereof are described in detail in JP-A-62-256219.
These thermoplastic resins, thermosetting resins, and reactive resins are
It is desirable to use at least those having polar groups listed below in addition to the main functional groups. In the present invention, the interaction between these resins and the abrasive particles is enhanced, and the dispersibility is improved and the It is desirable to use a polar group containing resin in order to interact with the compound and form an integral polishing layer. As the polar group, an acidic group such as a carboxylic acid group, a sulfenic acid group, a sulfonic acid group, a phosphoric acid group, a sulfuric acid group, a phosphon group, a phosphine group, a boric acid group, a sulfuric acid ester group, a phosphoric acid ester group, or an alkyl ester group thereof. (These acidic groups may be in the form of Na salts, etc.); amino acid groups; aminosulfonic acid groups, aminoalcohol sulfuric acid or phosphoric acid ester groups; alkylbetaine-type amphoteric groups; amino groups; A basic group such as an imino group, an imide group, an amide group; usually contains one or more and 6 or less epoxy group, hydroxyl group, alkoxyl group, thiol group, halogen group, silyl group, siloxy acid group, etc. 1 × 10 ⁻⁶ to 1 × 10 ⁻² equivalent / g of resin
It is desirable to include. Particularly desirable polar groups include an epoxy group, a —SO ₃ M group and the like (where M is H or an alkali metal such as Na or K, or an ammonium ion). These polar groups are copolymerized (co-condensation polymerization) with a monomer containing a polar group,
Alternatively, it can be introduced into the resin by utilizing a polymer reaction.

As the polar group-containing resin, vinyl chloride resin and polyurethane resin are particularly desirable. Particularly, the polar group is preferably an epoxy group or a —SO ₃ M group. The vinyl chloride resin is preferably an epoxy group-containing vinyl chloride-based copolymer, and includes a vinyl chloride repeating unit, an epoxy group-containing repeating unit, and —SO ₃ M (M is the same as the above and is particularly preferably Na). And a vinyl chloride-based copolymer containing a repeating unit having

The polar group content of the polar group-containing resin is 1 × 1.
The range of 0 ⁻⁶ to 1 × 10 ⁻² equivalent / g is desirable. More preferably, it is 1 × 10 ⁻⁶ to 1 × 10 ⁻² equivalent / g. The molecular weight is preferably 10,000 to 200,000. The polar group-containing polyurethane resin is specifically a polyol such as a polyether diol, a polyester diol, a polycarbonate diol, a polycaprolactone diol, and a diisocyanate, and if necessary, a polyhydric alcohol, an aliphatic polyamine, an alicyclic polyamine, It can be prepared with a chain extender such as an aromatic polyamine, and the polar group can be introduced using various means.

For example, it can be obtained by introducing a polar group into a polyester polyol using a polybasic acid or a polyol having a polar group, and reacting the polyester polyol with a polyisocyanate compound. This polyisocyanate compound can be used not only as a component of the polyurethane resin but also as a curing agent for forming a three-dimensional network structure of the resin. Further, in the present invention, any curing agent can be used.

The organic particles used in the present invention for dispersing, kneading and coating the abrasive particles, binder resin and the like can be mixed and used in any ratio. Specific examples are shown below. Acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketones; methanol, ethanol, butanol and other alcohols; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ether. Ester type such as ether; glycol ether type such as ether, glycol dimethyl ether, glycol monoethyl ether, dioxane;
Tar-based compounds (aromatic hydrocarbons) such as benzene, toluene, cresol, chlorobenzene, styrene; chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, N, N-dimethylformaldehyde, hexane, etc. can be used.

The polishing layer of the present invention may contain a lubricant, a dispersant, an antistatic agent or the like as an additive in addition to the organic solvent. The method of dispersion and mixing in the preparation of the coating for forming the polishing layer, which comprises the abrasive particles, the binder resin, the organic solvent, the additive and the like of the present invention, is arbitrary, and conventionally known methods can be applied. For example, several compositions of paint can be divided and mixed later. Various kneaders are used for kneading and dispersing. For example, two roll mill, three roll mill,
Ball mill, pebble mill, tron mill, sand grinder, segvari, attritor,
A high speed impeller disperser, a high speed stone mill, a high speed impact mill, a disper, a kneader, a high speed mixer, a homogenizer, an ultrasonic disperser and the like can be used.

As the flexible support used in the polishing tape of the present invention, for example, polyethylene terephthalate (P
ET), polyethylene naphthalate, polyethylene-
2,6-naphthalate, polypropylene, polycarbonate, polyethylene, polyamide, polyamideimide,
It can be selected from a film or sheet made of a synthetic resin such as polyimide, polysulfone, or polyethersulfone.

As a method for forming the polishing layer on the support, a conventionally known method can be used. For details, see “Coating Engineering” (Asakura Shoten, 1972) or “Latest coating technology / enhanced edition”. (The General Technology Center Co., Ltd., 1984) and the like can be used. As a method for applying the polishing layer on the flexible support, any application device, for example, air doctor coat, blade coat, rod coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer Examples thereof include a method using roll coating, gravure coating, kiss coating, spray coating, extrusion coating, spin coating and the like. A so-called sequential multi-layer coating in which two or more polishing layers are provided by continuously coating the polishing layer after coating and drying the polishing layer by the above-mentioned coating method may also be used, and JP-A-48-98803 (West Germany). Patent DT
-OS 2,309,159), JP-A-48-9923.
3 (West German Patent DT-AS2,309,158
No.) etc., wet simultaneous multi-layer coating (wet-on-wet coating method) may be used in which two or more magnetic layers are simultaneously formed by the multi-layer simultaneous coating method.

Techniques relating to kneading dispersion and coating are described in T.W. C.
The polishing layer can be provided by a multi-layer simultaneous coating method as described in "Paint Flow and Pigment Dispersion" (1975) by Patton (TC Patton). The dry thickness is determined by the use, shape, standard, etc. of the polishing tape. Further, although the purpose is different from that of the present invention, JP
No. 109084, two polishing layers having different polishing properties are provided, the upper polishing layer has a higher polishing property than the lower polishing layer, and the lower polishing layer has a higher precision finishing property than the upper polishing layer. A film is disclosed. The two polishing layers use the same abrasive particles, and have two characteristics by changing the particle concentration. That is, the high polishing property has a high particle concentration and the high precision finishing property has a low particle concentration. After the upper polishing layer is entirely used for roughing, the lower polishing layer appears and is used for finishing. Therefore, it is inconvenient to use it only for improving the finishing accuracy.

[0025]

EXAMPLES Examples and comparative examples of the polishing tape of the present invention will be shown. In the following examples and comparative examples, the expression "part" means "part by weight" unless otherwise specified. Further, it is easily understood as those involved in the art that the components and ratios shown here can be changed without departing from the spirit of the present invention. Therefore, the present invention should not be limited to the examples below.

(Example 1) <Composition of first mixed liquid> Abrasive particles: 300 parts Iron oxide (granular, average particle size 0.2 μm, Mohs hardness 5-6) Binder resin Vinyl chloride / vinyl acetate Polymerized resin: 20 parts Polyamide resin: 30 parts Epoxy resin: 7 parts Solvent: 320 parts After drying the first mixed liquid (viscosity 0.5 poise) having the above composition dispersed using a ball mill. To form a second polishing layer by coating so that the thickness of the polishing layer is 3.5 μm, and the iron oxide of the abrasive particles of the first mixed liquid is formed on the second polishing layer. Diameter 0.5 μm, Mohs hardness 6
To 7) are applied so that the thickness of the dried polishing layer is 1.5 μm to form the first polishing layer, and the total thickness is 5 μm. On a support of polyethylene terephthalate having a thickness of 23 μm, and dried under a speed of 60 m / min, 40 ° C in the front part, 80 ° C in the middle part and 120 ° C in the rear part to dry the polishing layer. After the formation, a 1/2 inch slit was made to manufacture a polishing tape for a magnetic head.

Example 2 In Example 1, the abrasive particles of the second polishing layer were made of titanium oxide (granular, average particle size 0.0
A polishing tape for a magnetic head was manufactured by slitting into 1/2 inch under the same conditions as in Example 1 except that the thickness was changed to 35 μm and Mohs hardness was 6 to 6.5).

(Example 3) The same as Example 1 except that calcium carbonate (granular, average particle size 0.07 μm, Mohs hardness 3) was used as the abrasive particles in the second polishing layer. Slitting to 1/2 inch under the conditions, a polishing tape for a magnetic head was manufactured.

Example 4 In Example 1, the abrasive particles of the second polishing layer were made of alumina (granular, average particle size 0.19).
A polishing tape for a magnetic head was manufactured by slitting into 1/2 inch under the same conditions as in Example 1 except that the thickness was changed to μm and Mohs hardness 9).

(Comparative Example 1) In Example 1, except that the thickness of the first polishing layer was changed to 5 μm and the second polishing layer was omitted, slitting was carried out in 1/2 inch under the same conditions as in Example 1. To produce a magnetic head polishing tape.

(Comparative Example 2) In Example 1, except that the abrasive particles of the second polishing layer were replaced by the same chromium oxide as that of the first polishing layer, 1/2 inch was obtained under the same conditions as in Example 1. Slitting was performed to manufacture a polishing tape for a magnetic head.

(Comparative Example 3) In Example 1, iron oxide (granular, average particle size 0. A polishing tape for a magnetic head was manufactured by slitting into 1/2 inch under the same conditions as in Example 1 except that the polishing tape was changed to 3 μm, Mohs hardness 5-6).

Then, using a commercially available Optronics polishing machine, an 8 mm VTR magnetic head was polished with a total of 7 types of polishing tapes of Examples 1 to 4 and Comparative Examples 1 to 3 at the same tape tension and after the same polishing time. The magnetic head reproduction level was measured by setting this magnetic head in a dedicated measuring machine to measure the output level of the magnetic head. The results are shown in Table 1.

[0034]

[Table 1]

From the results obtained in Examples 1 to 4 and Comparative Examples 1 to 3 described above, the single-layer coating of Comparative Example 1 and the two-layer same-type abrasive coating of Comparative Example 2 produced a video magnetic head output of 0 db. On the other hand, it was found that the polishing tapes manufactured in Examples 1 to 4 significantly increased the output of the video magnetic head.

[0036]

In the polishing tape of the present invention, the uppermost first polishing layer that is in direct contact with the surface to be polished during polishing is on the second polishing layer containing abrasive particles having a relatively small average particle size. As a result, the leveling effect of the coating liquid makes the surface of the first polishing layer a flat surface as a whole, with few minute protrusions. Therefore, as compared with the case where the first polishing layer is formed as a single layer on the flexible support, the force can be uniformly applied to the surface to be polished of the magnetic head and the occurrence of scratches can be prevented. Then, by selecting abrasive particles having a relatively large average particle diameter as the abrasive particles of the first polishing layer, a sufficient polishing effect can be obtained with a small force on the surface to be polished. Therefore, even a surface to be polished made of materials having different hardness, such as a laminated magnetic head, can be uniformly polished, and a step difference at the boundary between different materials of the laminated magnetic head can be prevented. Also, the head touch of the tape is improved and the output of the magnetic head can be improved. It should be noted that by using an inexpensive inorganic powder other than the abrasive in the second polishing layer, the expensive abrasive can be saved, and at the time of applying the first polishing layer, the extrusion coating method can be used simultaneously rather than the roll coating method. By applying it, the applied streaks can be reduced and the improvement of the yield can be expected.

Claims (2)

[Claims] 1. A polishing tape comprising at least two polishing layers comprising abrasive particles and a binder resin as a main component on a flexible support, wherein the average of the abrasive particles contained in the uppermost first polishing layer. A polishing tape characterized in that the average particle size B of the abrasive particles contained in the second polishing layer located immediately below the first polishing layer is smaller than the particle size A. 2. The average particle size A of the abrasive particles contained in the first polishing layer and the average particle size B of the abrasive particles contained in the second polishing layer are (B / A) ≦ 0.5. The polishing tape according to claim 1, which has the relationship of.