JPH0659629B2 - Polishing tape manufacturing method - Google Patents

Description

The present invention relates to a polishing tape used for polishing the surface of a magnetic disk, a magnetic head, or the like.

[Conventional technology]

The hard disk of a computer is made by plating an aluminum alloy substrate with nickel, phosphorus, etc., and then sputtering or plating iron, chromium, cobalt, etc. on this surface. At that time, in order to fix the sputtered or plated metal and improve the magnetic characteristics, nickel,
It is necessary to polish the surface plated with phosphorus etc. to make fine scratches (textures) on the surface. A polishing tape is used for this polishing and polishing process. In video or audio magnetic heads, smoothness of the surface on which the magnetic tape slides is particularly required, and polishing tape is also used to finish this surface.

Such a polishing tape has a flexible polishing coating liquid prepared by kneading a fine abrasive (abrasive grains), a binder (binder) and various additives used as necessary in a solvent. It is manufactured by coating on a support tape having the same and drying it. The method for producing this polishing tape is as follows, for example, as described in JP-B-53-68490. 1. A coating liquid preparation step in which an abrasive, a binder, an additive (for example, a crosslinking agent, a curing agent), and the like are kneaded with an organic solvent, dispersed, and filtered. 2. A coating / drying and winding step in which the coating liquid is applied onto a flexible support and dried to form an abrasive layer on the support tape, and the product is rolled into a roll. 3. A curing process in which the roll-shaped product is treated at a predetermined temperature and humidity for a certain period of time. It consists of a process to commercialize rolled products into a certain width and a certain length according to the customer's request. As described above, in the manufacturing process of the polishing tape, the product is wound into a roll and the roll-shaped product is cured at a predetermined temperature and humidity because it is more efficient to carry out the process as described above. .

[Problems to be Solved by the Invention]

However, there is a problem that when carrying out rolling in a roll form, the polishing tape is thermally deformed, and a difference in grindability and polishability easily occurs between the inside (start of winding) and the outside (end of winding) of the roll. (This phenomenon is referred to as "winding"-"loosenness" below.) This phenomenon depends on the brand of the product even if the product is wound into a roll and the curing is performed in a roll, even if carrying is carried out under mild conditions. It is a phenomenon that is observed to a greater or lesser extent regardless of the above.

A second problem to be solved by the present invention is that a conventional polishing tape manufactured by using a linear polyester resin as a binder causes scratches on the surface of an object to be polished.

In recent plating magnetic disks, there is a strong demand for higher recording density, smaller size, and higher performance. Therefore, in terms of electromagnetic conversion characteristics, it is necessary to reduce noise and increase output, but error From the viewpoint of characteristics, it is necessary to reduce defects due to such scratches. For this reason, even if fine and fine scratches (texture) are generated in the polishing finish of the nickel and phosphorus intermediate layers by the polishing tape, the demand for a polishing tape that does not generate scratches (scratches) is further increasing.

Particularly, in a magnetic head, for example, a video magnetic head, the recording wavelength is further shortened due to the increase in the capacity of the video tape, and accordingly, the performance required for the magnetic head is further enhanced. For this reason, it is not possible to meet these requirements in terms of quality with finishing using conventional polishing tapes, and in addition to making the finished surface highly smooth, it is necessary to provide polishing tapes that do not cause burrs, scratches, chipping, etc. on the magnetic head. Required by the industry.

Therefore, the present invention is to wind an abrasive tape in a roll shape, and when the roller is cured, winding tightening-unwinding does not occur, and grinding is performed at the beginning and end of winding of the roll, and there is no difference in abrasiveness. It is an object to provide a manufacturing method thereof.

Another object of the present invention is to provide a polishing tape which does not cause scratches on the finish polishing surface of an object to be polished such as a magnetic disk or a magnetic head, and a method for manufacturing the same.

[Means for Solving the Problems]

In order to solve the above problems, the present inventors have made diligent studies on components used in the production of polishing sheets, particularly binders. As a result, when polyester resin is used as a binder for polishing tapes, linear polyester is used. When a branched polyester resin is used instead of resin, winding-tightening does not occur when the polishing tape is cured in roll form, and even if it is used for polishing finish such as magnetic disk or magnetic head It was found that an abrasive tape that does not cause scratches can be produced, and the present invention was reached. The present invention was made as follows.

Many proposals have hitherto been made to use a thermoplastic resin, a thermosetting resin, a reactive resin, or a mixture thereof as a binder for an abrasive sheet (for example, JP-A-55-1).
29927, 62-94267, 62-94269, 62-176771, 62-1
99364, 62-203767, 62-203768, 63-16979, 63-
No. 84879, old Japanese Unexamined Patent Publication No. 54-97408, pages 2 and 3).

However, as a binder, (1) it may be dissolved in an organic solvent when preparing a coating liquid, and (2) when it is manufactured into a polishing tape, the binder may not soften or melt until it is thermally decomposed. Required.

Therefore, in the production of the polishing sheet, a thermoplastic resin which is easily dissolved in a solvent is used as a binder, and a chain extender and / or a cross-linking agent is added to the binder, which is applied and dried on a flexible support tape, and then cured. It is common to convert the binder layer into a heat-resistant thermosetting resin by performing treatment. In such a manufacturing process, a biaxially stretched polyethylene terephthalate film is industrially used as a flexible support to be applied.

Therefore, a saturated thermoplastic polyester resin having high adhesiveness with this film is widely used as a binder in the production of abrasive sheets (for example, Japanese Patent Publication No. 53-6).
8490). This saturated thermoplastic polyester resin (hereinafter abbreviated as polyester resin) is a copolymerized polyester resin containing a dicarboxylic acid mixture as an acid component and alkylene glycol, polyalkylene glycol or a mixture thereof as a glycol component. It is possible to change the structural composition of the polymer such as acid component, copolymerization ratio, molecular weight and block property.

Therefore, when the binder of the polishing sheet that can achieve the above objects was studied, the present inventors have found that when a polyester resin is used as the binder for the polishing tape,
If a branched polyester resin is used instead of a linear polyester resin, winding tightening-roll loosening does not occur when the polishing tape is cured in a roll shape, and it can be used for polishing finishing such as magnetic disks and magnetic heads. It has been found that it is possible to manufacture an abrasive tape that does not cause scratches on its finished surface.

The term "branched polyester resin" as used herein refers to a polyester resin containing alkylene glycol, polyalkylene glycol or a mixture thereof as an acid component of a dicarboxylic acid mixture by copolymerizing a compound having three or more ester forming functional groups. A copolymerized polyester resin having a branch in the polymer molecular chain, which may be either a random copolymer or a block copolymer, or a mixture thereof, and a linear polyester copolymer It does not matter even if it is a mixture of.

It has already been proposed to use a branched polyester resin as an adhesive structure (Japanese Patent Publication No. 48-3).
No. 7974, Japanese Examined Patent Publication No. 48-37975), all of these proposals are related to the adhesive and not to the binder of the polishing tape.

Examples of the divalent carboxylic acid used in the production of the branched polyester used in the present invention include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and phthalic acid, adipic acid, suberic acid, azelaic acid and sebacic acid. Examples thereof include aliphatic dicarboxylic acids having 2 to 12 atoms and ester-forming derivatives of these acids. Examples of the alkylene glycol include those having 2 to 10 carbon atoms such as ethylene glycol, propylene glycol, 1,4-butanediol and neopentyl glycol, as well as hydroxycarboxylic acids such as ε-oxycaproic acid and β-hydroxyethoxybenzoic acid. Acid and its ester,
Further, examples of the polyalkylene glycol include diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol and the like.

Examples of the compound having 3 or more ester forming functional groups for introducing branching into the polyester molecular chain include tricarballylic acid, trimesic acid, trimellitic acid and ester forming derivatives of these acids, and 3 or more hydroxyl groups. Specific examples of the polyols include trimethylolpropane, pentaerythritol, glycerin and sorbitol. The production of the polyester comprising these components is optional, but a usual polyester production method such as a direct esterification method or a transesterification method can be employed.

To block-copolymerize two different polyesters (for example, polyester for hard segment and polyester for soft segment), both polyesters can be mixed in the molten state for a short time or a functional group capable of reacting with the polyester end group. A diisocyanate having two or more
Any method such as bonding both polyesters with N-acylbislactam can be used.

As the chain extender and the cross-linking agent used in the present invention, 2 to 3 functional groups capable of reacting with a hydroxyl group or a carboxyl group at the polyester terminal to form a bond such as a urethane bond or an ester bond are used. Compounds having are preferred. Specific examples are: Alkylene diisocyanate and / or alkylene triisocyanate compound, for example, 2,4-tolylene diisocyanate, and its trimethylol propane adduct, 2,6-tolylene diisocyanate, triphenylmethane triisocyanate,
Hexamethylene diisocyanate modified product, etc. Epoxy compound ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, polypropylene glycol diglycidyl ether,
Diglycidiether of [bis (4-hydroxyphenyl) dimethylethane] and the like.

3. Aziridine compounds include, for example, tris (1-aziridinylphosphine oxide), trimethylolpropane-tri-β-azinyl pyropionate and the like.

In practice, the polyester is used by dissolving it in a solvent. Examples of the solvent include acetone, methyl ethyl ketone, cyclohexanone, toluene, xylene, ethyl acetate and a mixed solvent thereof. In addition, an antistatic agent, a dispersant, a coupling agent or the like may be used in combination as an additive.

Abrasives used in the present invention are corundum, emery, garnet, aluminum oxide, α-iron oxide, silicon carbide, zirconium oxide, chromium oxide, silicon nitride, diamond and the like, and these are one kind or a mixture of two or more kinds. Can be used. The average particle size of the abrasive is usually 0.3
˜40 μm, preferably 0.5˜30 μm.

Mixing these abrasives with the polyester resin solution,
Kneading is performed using a roll mill or the like to obtain a uniform polishing slurry solution. This polishing slurry solution is filtered in a filtration device using a membrane filter or the like. Then, before or after this filtration, the above chain extender and crosslinking agent are added to the polishing slurry solution. The filtered polishing slurry solution is stored in a reservoir with a stirrer to avoid settling of the abrasive particles.

The slurry solution stored in the storage tank is uniformly coated on a flexible support tape, and the coating tape is dried by evaporating the solvent by a dryer and wound into a roll by a winder. .

Effect When the present invention is carried out, the polishing tape is wound into a roll,
When the roll is cured, tightening-loosening does not occur, and there is almost no difference in grinding and polishing properties between the beginning and end of winding of the roll.

Further, even when a magnetic disk, a magnetic head, or the like is polished with the produced polishing tape, scratches do not occur on the finish polishing surface of the object to be polished.

〔Example〕

Tightening-grindability on the inside and outside of the roll due to looseness,
The difference in polishability is extremely small. Therefore, a vigorous new evaluation method was developed and provided for the evaluation. That is,
As a result of testing various objects to be polished, it was found that the pencil lead is a material suitable for the purpose of this test and gives reliable and reproducible results. Therefore, we created a jig in which the pencil lead was placed vertically and a load could be applied arbitrarily to it. This jig was placed on a polishing tape set on an XY turntable, and a constant load was applied to polish the core under predetermined conditions (travel speed, travel distance). Then, the decrease in the length of the core after polishing was measured to the unit of micron using a microscope. The measurement was repeated 5 times, and the average value was calculated as the polishing amount. In order to quantitatively display the winding tightness and looseness of the roll, the amount of polishing at the beginning of the roll (core side of the roll) is used as a reference to compare the amount of polishing at the middle and at the end of the roll (outside of the roll). The ratio was calculated and expressed as a percentage.

When using the polishing tape of the experimental example for polishing magnetic disks and magnetic heads, the evaluation was made under the same conditions (rotation speed, tape feed rate, nickel-phosphorus substrate (small piece)).
Polishing time, type of polishing liquid and its flow rate),
After cleaning the polished disc with a predetermined liquid, the surface of the disc was observed (for uneven polishing, presence of scratches, roughness, etc.).

A specific example of the present invention will be described below. However, these are examples of the present invention and do not limit the present invention in any way.

Experimental Examples 1 to 3 and Comparative Example 70 parts by weight of aluminum oxide (average particle size 3 μm) was dried in a dryer at 120 ° C. for 1 hour. The polyester resin as shown in the following table was added to a mixed solvent of toluene, methyl ethyl ketone and ethyl acetate (5: 4: 2 weight ratio), and the aluminum oxide was mixed with this and stirred well. A chain extender and a cross-linking agent as shown in the table were further added thereto, and then filtered using a cartridge filter having a hole size of 1 micron (nominal) to prepare a coating liquid.

This coating solution was evenly coated on a biaxially stretched polyethylene terephthalate film having a thickness of 25 μm to a thickness of 40 μm, and then a first stage dryer kept at 90 ° C.
The solvent was evaporated by a second stage dryer kept at 20 ° C., dried and wound on a paper core having an outer diameter of 95 mm. The winding length was 1000 m throughout this test.

Curing treatment was carried out at a temperature of 60 ° C. and a humidity of 60% for 24 hours in a drying chamber provided separately with the wound roll-shaped polishing tape. Finally, it was slit with a slitter to a width of 50 mm and wound on a product core having an outer diameter of 31 mm.

The temperature and humidity shown here are examples, and the temperature during processing is preferably 40 to 180 °, and the humidity is preferably 50% or more.

For the test of grindability and polishability, the product wound on the core has a diameter of 55 mm (roll end part), 75 mm diameter (roll middle part), 100 mm diameter (roll start part). The polishing tape wound around was sampled for testing.

In the following table, polyester resin (A) is a linear linear copolymerized polyester, (B) is a block copolymerized branched polyester of hard segment and soft segment, (C) is a random copolymerized branched polyester, which are both commercially available or The ones that were sold and provided as trial products were obtained and tested.
An isocyanate curing agent was used as a chain extender and a crosslinking agent.

As is clear from the above detailed description and the above table, it is understood that the polishing tape produced by the method of the present invention has no winding tightness or winding looseness and has a very small difference in grindability between the beginning and end of winding of the roll.

Also, as can be seen from the comparison with the comparative example, the surface quality of the polished surface with the polishing tape using the branched polyester resin as the binder is remarkably improved as compared with the case where the conventional linear polyester resin is used as the binder. I found out that it would be done.

Claims (6)

[Claims] 1. An abrasive is mixed with a binder solution and stirred, and then a chain extender and / or a cross-linking agent is added before or after the mixture slurry solution is filtered through a filter, and then the mixture slurry solution is made flexible. Of a polishing tape that is evenly coated on a support tape having the above-mentioned coating tape, is dried by evaporating the solvent in a dryer, and is wound into a roll by a winder, and the roll is cured. A method in which a mixed binder containing a saturated thermoplastic branched polyester in at least a part thereof is used as the binder in the production method. 2. The method according to claim 1, wherein the chain extender and the crosslinking agent are difunctional and / or trifunctional isocyanate compounds. 3. The method according to claim 1, wherein the chain extender and the crosslinking agent are bifunctional and trifunctional aziridyl compounds. 4. The method according to claim 1, wherein the chain extender and the crosslinking agent are bifunctional and / or trifunctional epoxy compounds. 5. The method according to claim 1, wherein the roll is treated in a temperature environment of 40 to 180 ° C. for a predetermined time. 6. The method according to claim 1, wherein after coating, drying and winding the slurry solution, the support tape on which the polishing layer is formed is placed in a humidity atmosphere of 50% or more.