JPH0985629A - Polishing body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the occurrence of a scratch with a grinding function kept at a high level by applying the constitution that a bonding agent contained in an upper polishing layer is soluble in water and a bonding agent contained a lower polishing layer formed between a nonmagnetic carrier and the upper abrasive layer is such type as hardly soluble in water. SOLUTION: A polishing body 1 (polishing tape) is formed out of a lower polishing layer 3 laid on a nonmagnetic carrier 2, and an upper polishing layer 4 on the lower polishing layer 3. Also, the lower polishing layer 3 contains abrasives 31 having a large grain size distributed via a water soluble bonding agent 32. The upper polishing layer 4 contains abrasives 41 having a small grain size distributed via a water soluble bonding agent 42. In this case, the thickness of the lower polishing layer 3 is taken at a value between 5μm and 10μm, and the grain size of the abrasives 31 thereof is approximately between 4μm and 10μm. Furthermore, the upper polishing layer 4 is formed to have thickness between 1μm and 3μm, and the grain size of the abrasives 41 thereof is taken at a value approximately between 1μm and 3μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing body such as a polishing tape used for polishing the surface of a hard disk substrate.

[0002]

2. Description of the Related Art Conventionally, a polishing body such as a polishing tape having a polishing layer mainly composed of abrasive particles and a binder on a support has been used for various polishing. ing.

For example, a hard disk (hereinafter, "HD")
Is formed by providing a magnetic layer on the surface of a substrate usually made of aluminum. The substrate surface is appropriately polished (textured) to prevent head adsorption during HD use. Although fine "streaks" are formed, this texture treatment is performed using a polishing body such as a polishing tape.

Further, in an ordinary polishing body, the binder used for the polishing layer is sparingly soluble in water, and the polishing agent acts on the polishing layer without being separated from the polishing layer. Therefore, the polishing force is strong and the object to be polished is scratched and scratched. Is likely to occur.

From the above point of view, as a polishing body for performing the texture treatment, for example, Japanese Patent Laid-Open No. 7-100769.
As disclosed in JP-A-6-304874 and the like, the binder of the polishing layer is composed of a water-soluble binder, and a coolant liquid (washing water) is used during polishing so that the binder dissolves. Is used as free abrasive grains to reduce the occurrence of scratches, but this has a problem that the polishing force is also reduced.

Further, in an ordinary polishing body, the polishing agent contained in the polishing layer is used as it is without any treatment,
The polishing power was adjusted by changing the particle size of the polishing agent or using different types of polishing agents having different hardness.

By the way, as the above-mentioned polishing body, the polishing power is large and the predetermined polishing is completed in a short time, and when the surface property of the object to be ground is in a predetermined state, an unexpectedly large abnormal polishing scratch ( It is required that scratches do not occur, but both are conflicting requirements. That is, the particle size of the polishing agent contained in the polishing layer is related to the polishing force and the generation of scratches. For example, if the polishing layer contains a polishing agent having a large particle size, the polishing force is large, but scratches are likely to occur. . On the other hand, if the polishing layer contains an abrasive having a small particle size,
Although scratches are less likely to occur, the polishing power becomes small, and both requirements cannot be satisfied at the same time by adjusting the polishing power as described above.

[0008]

Therefore, the inventors of the present invention have diligently studied a method of suppressing a decrease in polishing force for reducing the occurrence of scratches by using the abrasive contained in the surface polishing layer as free abrasive grains. As a result, they have found that the provision of a plurality of polishing layers can simultaneously satisfy the contradictory requirements that the polishing force is large and that scratches are unlikely to occur.

The present invention has been made in view of the above circumstances, and by combining a polishing layer made of a water-soluble binder and a polishing layer containing a sparingly water-soluble binder, a high scratching power can be ensured while maintaining a high scratching power. It is intended to provide a polishing body which suppresses the generation and can secure a good surface property.

[0010]

The polishing body of the present invention, which has solved the above-mentioned problems, has a plurality of polishing layers mainly containing an abrasive and a binder on a non-magnetic support, and among these polishing layers, an upper layer. The binder contained in the polishing layer is a water-soluble binder, and the binder contained in the lower polishing layer provided between the non-magnetic support and the upper polishing layer is a poorly water-soluble binder. It is characterized by that.

The average particle size of the abrasive contained in the upper polishing layer is preferably smaller than the average particle size of the abrasive contained in the lower polishing layer. Further, it is preferable that the upper polishing layer has a thickness of 1 to 3 μm, and the lower polishing layer has a thickness of 5 to 10 μm.

The lower polishing layer of the above-mentioned polishing body is composed of a sparingly water-soluble binder, and the polishing power is increased by the uneven shape of the surface, and the upper polishing layer is composed of a water-soluble binder. In the polishing, the free abrasive grains in which the water-soluble binder is dissolved and the abrasive is separated during the polishing are used for polishing, and good polishing can be performed without causing scratches on the object to be polished.

[0013]

According to the present invention as described above, a poorly water-soluble lower polishing layer is provided on the support side, and an appropriate uneven shape is formed on the surface of the lower layer, so that the lower polishing layer is The water-soluble upper polishing layer formed in the above reflects the uneven shape of the lower polishing layer, and it is possible to obtain a good polishing force in a state before the upper polishing layer is dissolved and in a dissolved state, and to dissolve it. The loosened abrasive can be prevented from biting into the surface of the object to be polished, the occurrence of scratches can be reduced, the polishing power is large, and the desired polishing surface property can be obtained.

Therefore, the polishing body of the present invention is, for example, HD
Not only the texture treatment of the substrate but also the polishing of various magnetic heads, the polishing treatment of various surfaces, the cleaning and the like can be performed, and good polishing without scratches can be realized.

In particular, when the particle size of the abrasive in the upper layer is smaller than that of the abrasive in the lower layer, the above-mentioned effect becomes remarkable, the uneven shape of the lower layer becomes large and the polishing power is increased, and the free abrasive grains are removed. Finer scratches can be further prevented. Further, the thickness of the upper polishing layer is 1 to
When it is formed as thin as 3 μm, the uneven shape of the lower polishing layer is remarkably reflected, and the effect of improving the polishing power is enhanced.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to embodiments of the polishing body of the present invention. FIG. 1 is a schematic view showing the structure of the polishing body of this example.

The polishing body 1 (polishing tape) of this example is one in which a lower polishing layer 3 is formed on a non-magnetic support 2, and an upper polishing layer 4 is formed on the lower polishing layer 3. In the lower polishing layer 3, an abrasive 31 having a large particle size is dispersed in a sparingly water-soluble binder 32. In the upper polishing layer 4, a polishing agent 41 having a small particle size is dispersed in a water-soluble binder 42.

The lower polishing layer 3 has a thickness of 5 to 10 μm, the abrasive 31 has a particle size of 4 to 10 μm, the upper polishing layer 4 has a thickness of 1 to 3 μm, and the abrasive 41 has a particle size. Is 1 to 3 μm.

Examples of the non-magnetic support usable in the present invention include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and vinyl based materials such as polyvinyl chloride. In addition to plastics such as resins, polycarbonate, polyimide, polyamide, polysulfone, polyphenyl sulfone and polybenzoxazole, metals such as aluminum and copper and ceramics such as glass can be used. Prior to coating, these supports may be subjected to corona discharge treatment, plasma treatment, undercoating treatment, heat treatment, dust removal treatment, metal deposition treatment, and alkali treatment.

In the case of an abrasive tape or the like, the center line average surface roughness Ra of these supports is preferably 0.001 to 1.5 μm (cutoff value 0.25 mm). The thickness of the support is
The thickness is preferably 2.5 to 500 μm, more preferably 3 to 75 μm. Further, it is desirable that the Young's modulus of either the longitudinal direction or the width direction of the support is 400 kg / mm ² or more.

Further, as abrasives usable for the lower and upper polishing layers, alumina, chromium oxide, α-alumina, silicon carbide, diamond, γ-alumina, fused alumina, corundum, artificial diamond, garnet,
Materials mainly having high Mohs hardness such as emery (main components: corundum and magnetite) and garnet can be used alone or in combination.

In addition to the above-mentioned polishing agent, powder having a small particle size may be contained in the above-mentioned polishing layer, and carbon black can be used as this powder. For example, furnace for rubber, thermal for rubber, black for color, Acetylene black or the like can be used. Its specific surface area is 5
~ 500m ² / g, DBP oil absorption is 10 ~ 400ml /
100 g, pH 2-10, water content 0.1-10%,
The tap density is preferably 0.1 to 1 g / cm ² . Specific examples of this carbon black include BLACKPEARLS 2000, 13 manufactured by Cabot Corporation.
00, 1000, 900, 800, 700, manufactured by Mitsubishi Chemical Corporation: 650B, 950B, 3250B, 850, 9
00,960,980,1000,2300,240
0,2600 and the like. In addition, carbon black that has been subjected to surface treatment with a dispersant or the like or graphitized with a resin can also be used.

Typical examples of the water-soluble binder used for the upper polishing layer include sodium salt of carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PV).
A), carboxyl group-containing polyurethane or the like is used.

The solvent of the water-soluble binder is water,
Also, water-soluble alcohols such as methyl alcohol and ethyl alcohol, and mixed liquids thereof are used.

As the poorly water-soluble binder for the lower layer, conventionally known thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, ultraviolet curable resins, visible light curable resins, and the like are used. Mixtures of can be used.

The thermoplastic resin has a softening temperature of 150 ° C. or lower and an average molecular weight of 10,000 to 30,000.
0, the degree of polymerization is about 50 to 2000, and more preferably about 200 to 700. For example, vinyl chloride vinyl acetate copolymer, vinyl chloride copolymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, vinyl chloride. Vinyl alcohol copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic ester acrylonitrile copolymer, acrylic ester vinylidene chloride copolymer, acrylic ester styrene copolymer, methacrylic ester acrylonitrile Copolymers, methacrylic acid ester vinylidene chloride copolymers, methacrylic acid ester styrene copolymers, urethane elastomers, nylon-silicone resins, nitrocellulose-polyamide resins, polyfucca vinyl, vinylidene 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, carboxy) (Methyl cellulose, acetyl cellulose, etc.), styrene-butadiene copolymer, polyester resin, polycarbonate resin, chlorovinyl ether acrylate copolymer, amino acid resin, various synthetic rubber thermoplastic resins, and mixtures thereof.

Further, the thermosetting resin or the reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and is condensed by heating and humidifying after coating and drying.
Those having an infinite molecular weight due to a reaction such as addition are preferably used. Further, among these resins, those not softened or melted before the resin is thermally decomposed are particularly preferable. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane resin, polyester resin, polyurethane polycarbonate resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin (electron beam curing 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 resin, low molecular weight glycol / high molecular weight Mixtures of diol / triphenylmethane triisocyanate, polyamine resins, polyimine resins and mixtures thereof.

These thermoplastic resins, thermosetting resins, and reactive resins have carboxylic acid (COOM), sulfinic acid, sulfenic acid, sulfonic acid (SO ₃ M), phosphoric acid (PO) as functional groups in addition to the main functional groups. (OM) (OM)), phosphonic acid, sulfuric acid (OSO ₃ M), and acidic groups (M is H, alkali metal, alkaline earth metal, hydrocarbon group) such as ester groups thereof, amino acids; amino sulfone Acids, sulfuric acid or phosphoric acid esters of amino alcohols, amphoteric groups such as sulfobetaine, phosphobetaine, and alkylbetaine type, amino groups, imino groups, imide groups, amide groups, etc., and also hydroxyl groups, alkoxyl groups, thiol groups, alkylthio Group, halogen group (F, Cl, Br, I), silyl group, siloxane group, epoxy group, isocyanato group, cyano group, nitrile group Oxo group, acryl group, include within six Usually one or more phosphine groups is preferably each functional group containing ^{1 × 10 -6 ~1 × 10 -2} eq per resin 1g.

In the abrasive body of the present invention, these binders are used alone or in combination thereof, and if necessary, other additives such as dispersants, lubricants, antistatic agents and antioxidants are used. , Antifungal agents, colorants, solvents and the like are added.

The polyisocyanate used as a curing agent in the polishing layer of the present invention includes tolylene diisocyanate,
Isocyanates such as 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, isophorone diisocyanate, and the isocyanates. It is possible to use products with polyalcohols, diisocyanate polyisocyanates produced by condensation of isocyanates, and products with polyisocyanates and polyurethanes whose terminal functional groups are isocyanates. The average molecular weight of these polyisocyanates is preferably 100 to 20,000.

Commercially available trade names of these polyisocyanates are Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate MTL (manufactured by Nippon Polyurethane Co., Ltd.),
Takenate D-102, Takenate D-110N, Takenate D-200, Takenate D-202, Takenate 300S, Takenate 500 (manufactured by Takeda Pharmaceutical Co., Ltd.), Sumidule T-80, Sumidule 44S, Sumidule P
F, Sumidule L, Sumidule N, Death module L, Death module IL, Death module N, Death module HL, Death module T65, Death module 1
5, Desmodule R, Desmodule RF, Desmodule SL, Desmodule Z4273 (manufactured by Sumitomo Bayer Co., Ltd.), etc., and these are used alone or in combination of two or more by utilizing the difference in curing reactivity. can do.

For the purpose of accelerating the curing reaction, a hydroxyl group (butanediol, hexanediol, having a molecular weight of 100
Compounds having an amino group (monomethylamine, dimethylamine, trimethylamine, etc.), a metal oxide catalyst, and a catalyst such as iron acetylacetonate can also be used in combination. It is desirable that these compounds having a hydroxyl group or an amino group are polyfunctional. These polyisocyanates are 2 per 100 parts by weight of the total amount of binder resin and polyisocyanate.
It is preferably used in an amount of ˜70 parts by weight, more preferably 5 to 50 parts by weight.

The method for dispersing and kneading the upper and lower polishing layer components is not particularly limited, and the order of addition of each component (resin, powder, lubricant, solvent, etc.), addition position during dispersion / kneading, The dispersion temperature (0 to 80 ° C.) and the like can be set appropriately. An ordinary kneading machine can be used for preparing the polishing layer paint.

The method for applying the coating solution for the lower polishing layer on the support and the method for applying the coating solution for the upper polishing layer on the lower polishing layer have a viscosity of 1 to 200.
After adjusting to 00 centistokes (25 ° C), air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss coater, cast coater, spray coater, rod coater , Forward rotation roll coater,
A curtain coater, an extrusion coater, a bar coater, a lip coater, etc. can be used, and other methods can also be used, and a detailed explanation of these methods can be found in "Coating Engineering" (published by Showa 46.20.46) issued by Asakura Shoten. For details, see pages 253 to 277. The order of application of these coating liquids can be arbitrarily selected, and a corona discharge treatment or the like may be performed before application of a desired liquid to improve adhesion to an undercoat layer or a support.

[0035]

EXAMPLES Examples and comparative examples of the present invention will be shown below to evaluate the polishing characteristics.

<Examples 1 to 5> This example has a thickness of 25.
On a support made of polyethylene terephthalate (PET) with a thickness of 0.1 μm, an undercoat layer made of polyester polyurethane resin is applied in a thickness of 0.1 μm, and a poorly water-soluble binder (polyurethane resin, sodium sulfonate 1 × 10 ⁻³ equivalent) / G resin-containing, Mw70 000), solvent (methyl ethyl ketone / cyclohexanone = 2/1), abrasive (alumina, particle size 5 μm), and an additive-dispersed coating liquid for the lower polishing layer having a thickness of 5 after drying. A lower polishing layer was formed by applying a bar coat coating so as to have a thickness of 10 μm and drying.

Then, a coating solution for the upper polishing layer in which a water-soluble binder (CMC), a solvent (water), a polishing agent (alumina, particle size 1.5 μm), and an additive are dispersed on the lower polishing layer. Was applied by bar coat application so that the thickness after drying was 1 to 3 μm, and an upper polishing layer was provided by drying to prepare a polishing tape sample.

In this example, the thickness of the upper polishing layer and the thickness of the lower polishing layer were changed to obtain various examples.
That is, the upper layer having a thickness of 1 μm and the lower layer having a thickness of 8 μm was used in Example 1, and the upper layer having a thickness of 2 μm and the lower layer having a thickness of 8 μm.
The thickness of the upper layer is 3 μm and the thickness of the lower layer is 8 μm, and the thickness of the upper layer is 2 μm and the thickness of the lower layer is 5 μm. Film thickness is 2μ
It is Example 5 in which the thickness of the lower layer is 10 μm.

Comparative Examples 1 and 2 In this comparative example, a single-layer polishing layer was formed on the same support as in the above-mentioned example, and the binder of this polishing layer was the lower layer of the above-mentioned example. The same sparingly water-soluble binder as used for the polishing layer was used, and the particle size of the polishing agent (alumina) was 1.5 μm in Comparative Example 1 and 5 μm in Comparative Example 2.
m, and the film thicknesses of the polishing layers are both 10 μm.

Comparative Examples 3 and 4 In this Comparative Example, a single-layer polishing layer was formed as in Comparative Examples 1 and 2 above.
As the binder for this polishing layer, the same water-soluble binder as that used for the upper polishing layer in the above example was used, and the particle size of the polishing agent (alumina) was 1.5 μm in Comparative Example 3 and 5 μm in Comparative Example 4. The polishing layer has a thickness of 10 μm.

Comparative Example 5 This Comparative Example has a lower polishing layer and an upper polishing layer as in the above Example, but both layers were made of a poorly water-soluble binder and both layers were formed. The film thickness and the particle size of the abrasive are set in the same manner as in Example 2.

Examples 1 to 1 of the present invention prepared as described above
Table 1 shows the results of the polishing test using the polishing tapes of Comparative Example No. 5 and Comparative Examples 1 to 5.

[0043]

[Table 1]

In the polishing test, an Ni-P-plated aluminum substrate (hard disk substrate) as an object to be polished was polished (textured) with each of the above-mentioned polishing tapes under the following conditions. Circle marks with a diameter of 5 mm were set at 4 places on the circumference of each of the 4 places on the circumference, and the center line average surface roughness Ra of the polished surface was measured randomly using the Taly step under the following conditions. Then, the inside of this circle was photographed at 800 times using a differential interference microscope, and the number of scratches generated was measured.

(1) The above-mentioned texture treatment conditions are: HD substrate rotation speed; 100 rpm tape feeding speed; 8 mm / sec swing; cross hatch cross angle is 30 degrees; treatment time; 20 seconds; cleaning liquid; Johnson coolant liquid. is there.

(2) The HD substrate surface roughness (center line average roughness Ra) is measured by the following apparatus: TAYLOR-HOBSON Taristep Measuring length: 0.25 mm Measuring speed: 0.025 mm / sec Cutoff; 25 Hz height magnification: 200,000 times.

The evaluation criteria for the evaluation of the grinding force and scratch characteristics in Table 1 and the overall evaluation are as follows: (a) Grinding force [Ra of HD] [Evaluation result] ⊙ 0.0085 μm or more ∙ Grinding force excellent level ∙ 0.005 to 0.0085 μm Good grinding power level △… 0.0035 to 0.005 μm Grinding power is slightly insufficient, but possible ×… Less than 0.0035 μm… Not possible due to insufficient grinding power (b) Scratches [Number of large scratches] [Evaluation result] ◎… 0 to 1 Excellent scratches ○… 2 to 3… Scratch good △… 4 to 11… Scratch slightly large, but good × …… 11 or more… Scratch not great (c) Comprehensive evaluation (evaluation considering grinding force and scratch) ◎ … Comprehensive evaluation excellent ○… Comprehensive evaluation good △… Comprehensive evaluation possible ×… Comprehensive evaluation not possible.

From the results shown in Table 1 above, in the example of the present invention, the generation of scratches can be suppressed while ensuring a good grinding force. Among them, when the film thickness of the upper polishing layer is increased, the grinding force is decreased, while the occurrence of scratches tends to be good, and when the film thickness of the lower polishing layer is increased, the polishing force is similarly increased. It tends to decrease, and the occurrence of scratches tends to be good.

On the other hand, in Comparative Examples 1, 2 and 5,
Since the polishing layer on the surface is poorly soluble in water, the polishing power is good, but since it is not free abrasive grains, the number of scratches is large and it is a defective product. In Comparative Examples 3 and 4,
Since the polishing layer is wholly dissolved, if the particle size of the abrasive is small, the polishing power will be insufficient, and if the particle size is large, scratches will frequently occur.

[Brief description of drawings]

FIG. 1 is a schematic view showing the structure of a polishing body according to the present invention.

[Explanation of symbols]

 1 polishing tape (polishing body) 2 support 3 lower polishing layer 4 upper polishing layer 31,41 polishing agent 32,42 binder

Claims (3)

[Claims] 1. A polishing body having a plurality of polishing layers mainly containing an abrasive and a binder on a non-magnetic support, wherein the binder contained in the upper polishing layer of the polishing layers is a water-soluble binder. And a binder contained in the lower polishing layer provided between the non-magnetic support and the upper polishing layer is a poorly water-soluble binder. 2. The abrasive body according to claim 1, wherein the average particle size of the abrasive contained in the upper polishing layer is smaller than the average particle size of the abrasive contained in the lower polishing layer. . 3. The polishing body according to claim 1, wherein the upper polishing layer has a thickness of 1 to 3 μm, and the lower polishing layer has a thickness of 5 to 10 μm.