JPH10315142A - Polishing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly polish a base material surface without giving a large flaw to the base material surface, and increase a grinding quantity by constituting a polishing sheet out of nonwoven fabric containing fiber entangled by fibrillation. SOLUTION: Fibrillated fiber is contained, and since retainability of a fine polishing particle is excellent, a base material surface is uniformly polished, and a fine texture can be formed. Since the fibrillated fiber is entangled, fiber is fixed so as to have a certain degree of flexibility, and since the polishing particle is not forcibly pressed to the base material surface, a large flaw is hardly given to the base material surface. Since the fibrillator fiber is entangled, flexibility of the fiber is restrained more than when fiber having a fiber diameter not more than 10 μm is used, and since the polishing particle can be firmly pressed to the base material surface, a polishing sheet having a large grinding quantity can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing sheet, and more particularly to a polishing sheet that can be used for texture processing when manufacturing precision equipment such as a magnetic recording medium.

[0002]

2. Description of the Related Art For example, when manufacturing a magnetic recording medium such as a magnetic disk, a non-magnetic plating base material is formed by subjecting a base material such as an aluminum alloy to a non-magnetic plating treatment such as alumite treatment or nickel-phosphorus plating. After texturing the surface of the non-magnetic plating base material, an underlayer (generally made of chromium or the like), a magnetic thin film layer (generally made of a cobalt-based alloy or the like), and a protective layer (generally (Made of carbonaceous material or the like). In the magnetic recording medium manufactured in this manner, since it is required to further reduce the distance (that is, the flying height) between the magnetic disk and the magnetic head, the magnetic recording medium is smoothed so that there are no protrusions on the surface of the magnetic disk. It is necessary to.

On the other hand, if the smoothing of the magnetic disk surface proceeds too much, the magnetic head will be attracted to the magnetic disk surface,
A phenomenon that does not float may occur. In order to prevent this, texture processing for forming fine grooves in the non-magnetic plating substrate is generally performed. That is, the texture processing is a step of polishing the surface of the non-magnetic plating base material to uniformly form fine scars (texture).

As the abrasive used in the texturing, a nonwoven fabric in which fibers having a fiber diameter of about 3 μm are fixed with urethane resin, a woven fabric made of fibers having a fiber diameter of about 5 μm, or a fiber having a fiber diameter of about 14 μm has been used. There was a flocking sheet and the like.

However, a nonwoven fabric in which fibers having a fiber diameter of about 3 μm are fixed with urethane resin has a large degree of freedom in the fibers, and may cause a large damage to the surface of the base material during polishing, or the urethane resin may fall off. Thus, they adhere to the surface of the base material, and make the surface of the base material non-uniform. In addition, a woven fabric composed of fibers having a fiber diameter of about 5 μm may cause a large damage to the surface of the base material, probably because of the lack of flexibility of the fibers. Because of the arrangement, the substrate surface was easily damaged.

For this reason, the applicant of the present application has filed Japanese Patent Application No. 9-231.
No. 49 proposed a polishing sheet having at least one surface of a layer of an entangled nonwoven fabric or a meltblown nonwoven fabric containing 80% or more of fibers having a fiber diameter of 10 µm or less. This polishing sheet solves the above-mentioned problem and is capable of uniformly forming fine scars by polishing uniformly without making a large scratch on the substrate surface. However, since a nonwoven fabric made of fibers having a small fiber diameter is used, a new problem that the grinding amount is small, that is, the grinding speed is low is included.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can uniformly polish a substrate without damaging the surface of the substrate. An object is to provide a large number of polishing sheets.

[0008]

The polishing sheet of the present invention comprises a nonwoven fabric containing fibrillated and entangled fibers. Since it contains the fibrillated fibers and is excellent in holding fine abrasive particles, the base material surface can be polished uniformly to form a fine texture. In addition, the fibrillated fibers are entangled,
The fibers are fixed so that they have some flexibility,
Since the abrasive particles are not forcibly pressed against the substrate surface,
It is difficult to make large scratches on the substrate surface. Furthermore, since the fibrillated fibers are entangled, the flexibility of the fibers is suppressed as compared with the conventional case where fibers having a fiber diameter of 10 μm or less are used, and the abrasive particles can be pressed firmly against the substrate surface. Therefore, the polishing sheet has a large amount of grinding. That is, since the fibers are appropriately fixed by the entanglement of the fibrillated fibers, the polishing sheet can appropriately press the abrasive particles against the surface of the base material.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The abrasive sheet of the present invention can be uniformly polished by the action of fibrillated and entangled fibers without causing significant damage to the substrate surface, and has a large amount of grinding. . The fibrillated state refers to a state in which the fine fibers are not completely separated, but are connected to other fibers somewhere in the fine fibers. This state can be easily confirmed by an electron micrograph.

[0010] The state of being entangled means a state in which the adhesive is not used and the form is stable. For example, the tensile elongation in at least one direction of a non-woven fabric which does not use an adhesive is used. It means a state that is 60% or less. This tensile elongation refers to a value measured using an Instron type tensile strength / elongation measuring instrument. The measurement condition was 5
using a non-woven fabric having a width of 23 cm and a length of 23 cm;
The distance D (mm) required until the nonwoven fabric breaks at 0 mm and a tensile speed of 100 mm / min is measured. From this measurement result, the tensile elongation can be calculated by the following equation. Tensile elongation (%) = D / 100 × 100 = D

Examples of the fibrillated fiber or fibrillable fiber include liquid crystal polyester fiber, aromatic polyamide fiber, synthetic pulp, wood pulp, vegetable pulp, cellulose fiber formed by a solvent spinning method, One or more types of acrylic fibers and vinylon fibers formed by solvent wet cooling gel spinning as disclosed in 2-175915 and the like can be used. Among them, the liquid crystal polyester fiber has high rigidity of the fiber and can increase the grinding amount, and the polishing sheet of the present invention is preferably polished while supplying a slurry liquid containing abrasive particles. Since the strength does not decrease, it can be suitably used.

The preferred liquid crystal polyester fiber can be formed by spinning a liquid crystal polyester resin. In the present specification, a liquid crystal polyester-based resin refers to a polymer capable of forming an anisotropic molten phase. This type of polymer contains a regular parallel arrangement in the molecular chain and is generally elongated, flat, and rigid along the long axis of the molecule. The anisotropic molten phase can be confirmed by, for example, a normal polarization measurement method using a crossed polarizer.

The liquid crystal polyester resin used in the present invention is not particularly limited, but may be a wholly aromatic polyester resin alone or in an appropriate combination of an aromatic diol, an aromatic dicarboxylic acid, or an aromatic hydroxycarboxylic acid. Is preferred. Among these wholly aromatic polyester resins, liquid crystal polyester fibers composed of a copolymer of p-hydroxybenzoic acid and 2-hydroxynaphthalene-6-carboxylic acid can be suitably used because they have appropriate rigidity.

As the aromatic diol, aromatic dicarboxylic acid and aromatic hydroxycarboxylic acid, for example, the following can be used. (1) Aromatic diol

Embedded image (Wherein R ¹ and R ² are each independently a hydrogen atom,
Halogen atom (for example, chlorine atom, bromine atom, iodine atom, fluorine atom), alkyl group (for example, having 1 to 4 carbon atoms)
A lower alkyl group), a phenyl group, or a phenyl group substituted with a halogen atom (eg, a chlorine atom, a bromine atom, an iodine atom, a fluorine atom) or an alkyl group (eg, a lower alkyl group having 1 to 4 carbon atoms) Is)

Embedded image (In the formula, A _{-CH 2 -, - C (CH} 3) 2 -, or -S
O _2- )

Embedded image (2) Aromatic dicarboxylic acid

Embedded image (Wherein, R ³ is a hydrogen atom, a halogen atom (eg, a chlorine atom, a bromine atom, an iodine atom, a fluorine atom), or an alkyl group (eg, a lower alkyl group having 1 to 4 carbon atoms))
Is)

Embedded image (3) aromatic hydroxycarboxylic acid

Embedded image (Wherein, R ⁴ is a hydrogen atom, a halogen atom (eg, a chlorine atom, a bromine atom, an iodine atom, a fluorine atom), or an alkyl group (eg, a lower alkyl group having 1 to 4 carbon atoms))

Embedded image

When spinning the liquid crystal polyester resin, in order to improve spinnability, a substituent may be introduced into an aromatic ring, a non-linear monomer may be used, or a bent chain may be introduced. good.

The rigidity of the liquid crystal polyester fiber obtained by spinning such a liquid crystal polyester resin can be improved by heat treatment at a temperature lower by about 50 ° C. than the melting point of the liquid crystal polyester resin. , Heat treatment for a long time makes it difficult to fibrillate,
It is preferable not to perform the heat treatment for a long time. To facilitate fibrillation, it is preferable to use a liquid crystal polyester fiber that has not been subjected to any heat treatment after spinning the fiber.

The content of the fibrillated fibers as described above varies depending on the state of the nonwoven fabric. However, when the nonwoven fabric consists of one layer, it is contained in the nonwoven fabric. It is sufficient that the content is 3 mass% or more, preferably 5 mass% or more, and most preferably 10 mass% or more. The content of fibrillated fiber is 3 mass%
If the amount is less than the above, there is a possibility that the retention of the abrasive particles and the appropriate flexibility of the fiber cannot be obtained. On the other hand, when the content of the fibrillated fiber exceeds 50 mass%, the flexibility of the fiber is lost and there is a possibility that the surface of the base material may be greatly damaged. Therefore, the content is preferably 50 mass% or less.

As the fibers other than the fibrillated fibers, ultrafine fibers having a fiber diameter of 10 μm or less are used so as to be excellent in holding fine abrasive particles and to form a fine texture by uniformly polishing the substrate surface. Preferably, it contains ultrafine fibers having a fiber diameter of 8 μm or less, more preferably ultrafine fibers having a fiber diameter of 6 μm or less. On the other hand, the fiber diameter is preferably 0.01 μm or more, and more preferably 1 μm or more, so that the ultrafine fibers are not broken by friction during polishing. When the cross-sectional shape of the microfiber is non-circular, the diameter of a circle having the same area as the cross-sectional area is regarded as the fiber diameter of the microfiber. The content of the ultrafine fibers is preferably 50 to 97 mass%, more preferably 50 to 95 mass%, in view of the relationship with the fibrillated fibers.
, And most preferably 50 to 90 mass%.

The ultrafine fibers having a fiber diameter of 10 μm or less are made of, for example, two or more resin components, and are divided into ultrafine fibers which can be divided into ultrafine fibers by physical and / or chemical treatment, or melt blown. Can be formed. Among these, the ultrafine fibers generated by dividing the splittable fibers are more excellent in fiber strength, and can be suitably used because the ultrafine fibers are harder to break due to friction during polishing. The physical treatment includes, for example, a needle, a fluid flow such as a water flow, a calendar treatment, and the like.The chemical treatment includes, for example, a treatment for dissolving and removing a resin component with a solvent or a process for swelling the resin component. is there.

Examples of the splittable fibers that can be used when generating ultrafine fibers from the preferable splittable fibers include, for example,
As shown in the schematic cross-sectional view of the fiber in FIG. 1, a sea-island type fiber in which a component B which is difficult to remove is arranged and / or dispersed in an island form in a component A which can be removed with the remover. There is
By removing the component A of the sea-island type fiber, it is possible to generate an ultrafine fiber composed of the component B. Note that A
If the components can be divided by a physical action, two kinds of ultrafine fibers, at least an ultrafine fiber consisting of the component A and an ultrafine fiber consisting of the component B, can be generated by applying the physical action. The island component does not need to be composed of one type of resin component, and may be composed of two or more types of resin components. Furthermore, the size of the island components does not need to be uniform, and if island components of various sizes are mixed, polishing can be performed more uniformly without damaging the surface of the base material. More specifically, it preferably contains ultrafine fibers having a fiber diameter of 1 to 5 μm (preferably 2 to 3 μm) and ultrafine fibers having a fiber diameter of 0.8 μm or less (preferably 0.5 μm or less). The fiber diameter is 1 to 5 μm (preferably 2 to 5 μm).
The ratio of the number of ultrafine fibers of 3 μm) to the number of ultrafine fibers of a fiber diameter of 0.8 μm or less (preferably 0.5 μm or less) is 0.
1: 99.9 to 5:95 (preferably 1:99 to 3: 9
7) is preferable.

The removing agent varies depending on the resin component, but includes, for example, a solvent, an enzyme, and a microorganism. Among these, the solvent is preferably used because it has a high removal rate and is easy to handle. Among these solvents, aqueous solvents can be suitably used because they are easier to handle and process. In the present invention, the term “removable” means that 95% by mass or more of the resin component can be removed, and the term “removability” means that when the resin component is exposed under the conditions at the time of removing the resin component removable by the remover. , 30m of this resin component
It means that the mass is reduced only by less than ass%.

As another splittable fiber that can be used in the present invention, for example, as shown in FIG. 2, a schematic cross-sectional view of the fiber, the component A and the component B, which is poorly compatible with the component A, are alternately laminated in layers. There is a multiplexed bimetallic fiber as described above, and if a physical action is applied to the multiplexed bimetallic fiber, two types of ultrafine fibers, an ultrafine fiber composed of component A and an ultrafine fiber composed of component B, can be generated. FIG. 2 shows a case in which the splittable fiber is composed of two types of resin components. However, if it is composed of three types of resin components, three types of ultrafine fibers can be generated. A variety of microfibers can be generated. In addition, when the A component and the B component are not poorly compatible and a resin component having different solubility and swelling property with respect to the removing agent is combined, ultrafine fibers can be generated by the removing agent.

The poor compatibility means that a bonded conjugate fiber is spun from two kinds of target resins, and a shear force is applied to the bonded conjugate fiber with a finger to separate each resin component. Refers to the case where division is possible.

As another splittable fiber that can be used in the present invention, for example, as shown in FIG. 3 and FIG. 4, a schematic cross-sectional view of the fiber, component A is applied from the inside of the fiber (preferably the fiber axis) to the fiber surface. There is a chrysanthemum flower type fiber which is extended and is divided by the poorly compatible B component with the A component. By applying physical action to this chrysanthemum flower type fiber, two kinds of ultrafine fibers consisting of the A component and extra fine fibers consisting of the B component are obtained. Fiber can be generated. FIGS. 3 and 4 show the case where the splittable fiber is composed of two types of resin components. However, if it is composed of three types of resin components, three types of ultrafine fibers can be generated. If it becomes 4
Various types of ultrafine fibers can be generated. When the A component and the B component are not poorly compatible and are composed of resin components having different solubility and swelling property with respect to the removing agent, the removing agent can generate ultrafine fibers.

Further, examples of other splittable fibers that can be used in the present invention include those in which the island component of the sea-island fiber is a sea-island type (see FIG. 5) and those in which the island component of the sea-island fiber is a multi-bimetal type. Or at least one resin component of the multi-bimetal type fiber is a sea-island type (see FIG. 6), and at least one resin component of the multi-bimetal type fiber is a multi-bimetal type or chrysanthemum type. Or at least one resin component of the chrysanthemum flower fiber is a sea-island type (see FIG. 7), or at least one resin component of the chrysanthemum flower fiber is a multi-bimetal type or a chrysanthemum flower type. There are things that are. If these splittable fibers are used, ultrafine fibers having a small fiber diameter can be easily generated.

The resin component constituting the splittable fiber may be a combination of two or more resin components which have a fiber-forming ability and can be split by physical and / or chemical treatment. 6, nylon 66, polyamide such as nylon-based copolymer, polyethylene terephthalate, polyethylene terephthalate-based copolymer,
Polybutylene terephthalate, polyester such as polybutylene terephthalate copolymer, polyethylene, polypropylene, polyolefin such as polymethylpentene, polyurethane, polyacrylonitrile, vinyl polymer, or polyglycolic acid, glycolic acid copolymer, polylactic acid, Aliphatic polyester-based polymers such as lactic acid copolymers, and aliphatic polyesters in which aliphatic amides such as coupler amide, tetramethylene adipamide, undecanamide, laurolacamide, and hexamethylene adipamide are copolymerized with the aliphatic polyester-based polymer A resin such as an amide copolymer may be appropriately combined.

As a method of polishing with a polishing sheet,
Since it is preferable to carry out while supplying a slurry liquid containing abrasive particles, a splittable fiber capable of generating ultrafine fibers made of polyamide having excellent hydrophilicity so that the abrasive particles are hardly aggregated and hardly damage the substrate surface. Is preferred. Further, a splittable fiber capable of generating a polyester ultrafine fiber having higher rigidity is preferable so that the amount of grinding by the abrasive particles can be increased. Therefore, it is most preferable to use a splittable fiber capable of generating at least a polyamide ultrafine fiber and a polyester ultrafine fiber.

Such a splittable fiber which can be used in the present invention can be easily spun by a conventional composite spinning method, a mixed spinning method, or an appropriate combination thereof. Also, as long as the spinnability and fiber strength are not reduced,
A flame retardant, an antistatic agent, a moisture absorbent, a colorant, a dye, a conductive agent, a hydrophilic agent, and the like may be mixed.

The polishing sheet of the present invention comprises a non-woven fabric containing fibril-entangled fibers as described above. If the fibrillated and entangled fibers are entangled by the water flow, the fibrillated fibers are highly entangled,
This is a suitable polishing sheet because the flexibility of the fibers can be further suppressed, and as a result, the amount of grinding can be increased. Further, since the nonwoven fabric entangled by the water flow is uniformly entangled, the surface of the base material can be polished uniformly, and since the nonwoven fabric can be a thinner nonwoven fabric having a lower surface density, the polishing sheet is wound. When used, the winding length can be increased.

The polishing sheet of the present invention comprises the above-mentioned nonwoven fabric. The polishing sheet of the present invention is preferably polished while supplying a slurry liquid containing abrasive particles. Therefore, when the amount of water in which the abrasive particles are dispersed is reduced, the abrasive particles are likely to aggregate and easily damage the surface of the base material.In addition to the nonwoven fabric described above, a layer containing hydrophilic fibers, for example, hydrophilic It is preferable to provide a layer of nonwoven fabric or knitted fabric containing conductive fibers.

The hydrophilic fiber is a fiber having an official moisture regain of 5% or more, for example, fiber such as rayon fiber, polynosic fiber, cupra fiber, acetate fiber, tencel fiber (cellulose fiber obtained by a solvent extraction method) and the like. Can be used. Among them, rayon fiber and Tencel fiber are softened when wet, and can be suitably used because the abrasive particles are not forcibly pressed against the surface of the base material. Tencel fiber can be used more preferably because the decrease in strength during wet is small. The hydrophilic fiber is preferably contained in the layer in an amount of 20 mass% or more, and the layer containing the hydrophilic fiber is preferably adjacent to the nonwoven fabric so that moisture can be supplied to the nonwoven fabric.

If the polishing sheet of the present invention undergoes a dimensional change when it is polished, the surface of the substrate cannot be polished uniformly. Therefore, a reinforcing layer is provided to impart morphological stability to the polishing sheet. Is preferred. The reinforcing layer is a layer in which the polishing sheet satisfies the following conditions by providing the reinforcing layer. When a polishing sheet having a width of 5 cm is fixed between chucks having an interval of 10 cm and a load of 2 kgf is applied to the polishing sheet, the width of the polishing sheet at the center of the polishing sheet (the center between the chucks) decreases. 2 mm or less

As such a reinforcing layer, for example, yarn,
A net, a woven fabric, a nonwoven fabric or a knitted fabric fixed by a thermoplastic fiber, a film, or the like can be used. Among these, a film can be suitably used because it has a uniform thickness and is excellent in strength. When the polishing sheet has a layer containing hydrophilic fibers and a reinforcing layer, the layer containing hydrophilic fibers is preferably adjacent to the nonwoven fabric, as described above. Preferably, the outermost layer is formed adjacent to the fiber layer. Further, the reinforcing layer and the layer containing the hydrophilic fiber may be the same layer, such as a layer made of a hydrophilic fiber and a thermoplastic fiber, such as a layer fixed with the thermoplastic fiber.

Hereinafter, the method for producing the abrasive sheet of the present invention will be briefly described.

First, fibrillated fibers and / or fibrillable fibers are prepared. Preferably a fiber diameter of 1
At least one of a splittable fiber capable of generating an ultrafine fiber of 0 μm or less, an ultrafine fiber of a fiber diameter of 10 μm or less, and a thermoplastic resin capable of forming a fiber web by a melt blow method or a spun bond method is prepared. The fibrillated fiber can be formed from a fibrillable fiber by a beater, a refiner, or the like. Fibrillable fibers are commercially available and are readily available. The splittable fiber can be spun by a conventional method, or can be easily obtained because it is commercially available. An ultrafine fiber having a fiber diameter of 10 μm or less can be easily formed by dividing a splittable fiber by physical and / or chemical treatment. Thermoplastic resins capable of forming a fibrous web by a melt blow method or a spun bond method are commercially available and can be easily obtained.

Next, a fiber web containing these fibers is
For example, dry method such as card method and air-lay method, wet method,
Alternatively, it is formed by a direct method such as a melt blow method or a spun bond method. The fiber length varies depending on the method of forming the fiber web.
In the case where a fiber of 110 mm is used and formed by a wet method, a fiber of 1 to 30 mm is used. The fiber diameter of the fibrillated fiber is preferably 10 μm or less, and the fibrillable fiber may have any fiber diameter capable of generating a fibril having a fiber diameter of 10 μm or less, and is preferably 20 μm or less. Further, the fiber diameter of the splittable fiber is not particularly limited as long as it can generate an ultrafine fiber having a fiber diameter of 10 μm or less. The fiber web may be a laminate of two or more fiber webs.

When fibrillable fibers (preferably including splittable fibers) are used, they may be fibrillated (divided) at any stage before the formation of the nonwoven fabric.
In production, it is preferable to fibrillate (divide) at the same time as or after forming the nonwoven fabric. In the present invention,
Because the fibrillated fibers must be entangled,
It is preferable to fibrillate simultaneously with the formation of the nonwoven fabric which does not require an additional entanglement step. In addition, as a fibrillation method, for example, there are a fluid flow such as a needle and a water flow, and a calender treatment.

Next, the fiber web is entangled by, for example, a method using a water stream or a method using a needle.
Among them, a method using a water flow is preferable because the fibrillated fibers can be highly entangled and the flexibility of the fibers can be further suppressed. Another advantage is that the entire fiber web can be uniformly entangled, and a thinner polishing sheet can be formed with a lower surface density. When fibers that can be fibrillated (preferably also include splittable fibers) are included, they can be entangled and fibrillated simultaneously by this entanglement treatment.

The conditions of the water entanglement, which is this preferred entanglement method, include, for example, a nozzle diameter of 0.05 to 0.3 mm, preferably 0.08 to 0.2 mm, and a pitch of 0.2 to 3 mm.
Preferably, a nozzle plate having a pressure of 1 MPa to 30 MPa, preferably 5 MPa to 25 MPa is jetted using nozzle plates of 0.4 to 2 mm arranged in one or more rows. The pressure of the water stream may be changed, or the nozzle may be swung or vibrated. Also, when the fiber web is entangled with the water stream,
If the non-opening part of the support such as net or mesh is large,
A nonwoven fabric having pores can be formed in appearance, and a nonwoven fabric having a small non-opening portion can form a uniform nonwoven fabric having no holes in appearance. When polishing precision equipment, a fine mesh of 50 mesh or more, or a perforated plate equivalent to this, consisting of a fine wire with a wire diameter of 0.25 mm or less, so that the substrate surface can be polished more uniformly It is preferred to use.

When a splittable fiber that can be chemically split is used, or when the splittable fiber is not sufficiently split, the resin component is dissolved and removed with a solvent after the entanglement treatment to split the splittable fiber. It is preferable to divide the resin component by swelling the resin component, or to divide the resin component sufficiently by calendering.

The layer containing hydrophilic fibers may be made of a non-woven fabric or a knitted fabric. The non-woven fabric may be formed by a method of entanglement with a needle or a water stream, a method of fixing with a binder, a thermoplastic fiber other than the hydrophilic fiber. There is a method in which fibers are included and fixed by fusing the thermoplastic fibers. In addition, a fiber web containing hydrophilic fibers is laminated on a fiber web containing fibrillated fibers and / or fibrillable fibers, and the fibrillated fibers and / or
Or, at the same time as the entanglement of the fibrillable fibers, if the fiber web containing hydrophilic fibers is also entangled, the step of integrating the nonwoven fabric and the layer containing hydrophilic fibers can be omitted. This is a method for forming a layer. However, when a layer containing hydrophilic fibers is formed by this method, fibrillated fibers and / or fibrils are formed so that the fibers constituting the fiber web containing hydrophilic fibers are not exposed on the polishing surface of the polishing sheet. It is preferable to perform the entanglement treatment only from the fiber web side containing the convertible fiber. In addition, the layer containing the hydrophilic fiber is prepared by mixing thermoplastic fibers in addition to the hydrophilic fiber and plasticizing the thermoplastic fiber (the layer containing the hydrophilic fiber is also a reinforcing layer), or It can be integrated with the nonwoven fabric by another binder. When integrated with the nonwoven fabric by this another binder, so as not to prevent the transfer of moisture from the layer containing hydrophilic fibers to the nonwoven fabric,
Partial bonding is preferred.

The reinforcing layer of the present invention may be, for example, a yarn, a net,
Woven fabric, non-woven fabric or knitted fabric fixed by thermoplastic fiber,
For example, the nonwoven fabric fixed by thermoplastic fibers is formed by plasticizing a fiber web formed by a dry method and / or a wet method by passing it between hot calender rolls and fixing. it can. In addition, as a method of integrating this reinforcing layer with a layer containing a nonwoven fabric or a hydrophilic fiber, a fiber web containing a fibrillated fiber and / or a fibrillable fiber,
Or, a layer containing a hydrophilic fiber (for example, a fiber web) is laminated with a fiber web serving as a reinforcing layer, and simultaneously with the entanglement of the fiber web containing the fibrillated fiber and / or the fibrillable fiber, The reinforcing layer can be integrated. In addition, they may be integrated by a binder, or if the reinforcing body is thermoplastic, may be integrated using the thermoplasticity of the reinforcing body. When the reinforcing layer is formed of a film, the melt-extruded film is laminated on a layer containing a nonwoven fabric or a hydrophilic fiber, and if necessary, can be easily integrated by applying pressure.

The polishing sheet obtained in this manner can be polished uniformly without causing significant damage to the surface of the base material, and has a large amount of grinding, so that it can be used for magnetic disks (for example, hard disks). It can be suitably used in a polishing step, particularly a texture step, when producing a magnetic recording medium from a base material. In particular, it can be suitably used for texturing a non-magnetic plating base material for a magnetic disk. When used for texturing a non-magnetic plating base material for a magnetic disk, see Japanese Unexamined Patent Publication No.
As described in JP-A-96355, the substrate surface can be polished while supplying a slurry liquid containing abrasive particles.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0045]

【Example】

(Example 1) As a fibrillable fiber, it is made of a copolymer of p-hydroxybenzoic acid and 2-hydroxynaphthalene-6-carboxylic acid, is not heat-treated after spinning, and can be fibrillated by a water stream. , Fiber diameter 16μ
m, a liquid crystal polyester fiber (Vectran NT, manufactured by Kuraray Co., Ltd.) having a fiber length of 51 mm was prepared. On the other hand, as the splittable fiber, a polyester component (A) as shown in FIG.
Is divided into eight sections by a polyamide component (B) extending from the center of the fiber toward the fiber surface, has a chrysanthemum flower-shaped cross-section, is dividable by water flow, has a fineness of 3 denier, and has a fiber length of 51 m.
m (DF-5, manufactured by Daiwabo Co., Ltd., capable of generating eight ultrafine fibers with a fiber diameter of 4.6 μm made of a polyester component and eight ultrafine fibers with a fiber diameter of 4.6 μm made of a polyamide component) Was prepared.

Next, the liquid crystal polyester fiber 30mas
s% and 70 mass% of splittable fibers, and a crossed fiber web in which a carded unidirectional fiber web and a unidirectional fiber web formed in the same manner as the unidirectional fiber web are crossed by a cross layer. Were laminated at a mass ratio of 1: 4 to form a laminated fiber web.

Next, this laminated fiber web was treated with a wire diameter of 0.1
After being placed on a 100-mesh net made of a 5 mm wire, water is jetted from a nozzle plate having a diameter of 0.15 mm and a pitch of 0.6 mm at a pressure of 12 MPa to alternately process both sides of the laminated fiber web three times at a time. Then, fibrillation of liquid crystal polyester fibers, division of splittable fibers, and entanglement of these fibers are performed to form an entangled nonwoven fabric having an areal density of 80 g / m ² , a thickness of 0.32 mm, and a tensile elongation of 40%. did.

On the other hand, unstretched polyester fiber (denier 5 denier, fiber length 38 mm) 40 mass% and stretched polyester fiber (denier 3 denier, fiber length 64 mm) 60
mass%, and carded to form a unidirectional fiber web. Then, this unidirectional fiber web is laminated on the unidirectional fiber web side of the entangled nonwoven fabric,
At the same time, the unidirectional fiber web is bonded (as a result, a reinforcing layer) by passing between the calender rolls at 0 ° C. and a linear pressure of 60 kg / cm, and simultaneously bonded and integrated with the entangled nonwoven fabric.
A polishing sheet having an area density of 130 g / m ² and a thickness of 0.22 mm was formed. The ultrafine fibers constituting the entangled nonwoven fabric were not fused. In addition, polishing sheet (5cm width)
Was fixed between chucks having an interval of 10 cm, and when a load of 2 kgf was applied to the polishing sheet, the reduction in the width of the polishing sheet at the center of the polishing sheet (center between the chucks) was 0 mm.

(Example 2) 5 fibrillable fibers were used.
The same as in Example 1 except that the mass% and the splittable fiber were 95 mass%, and the area density was 80 g /
An entangled nonwoven fabric having m ² , thickness of 0.35 mm and tensile elongation of 50% was formed. Next, a reinforcing layer was applied to this entangled nonwoven fabric in exactly the same manner as in Example 1, and the area density was 130 g / m ² ,
A polishing sheet having a thickness of 0.22 mm was formed. The ultrafine fibers constituting the entangled nonwoven fabric were not fused.
Further, a polishing sheet (5 cm width) is fixed between chucks having an interval of 10 cm, and when a load of 2 kgf is applied to the polishing sheet, the width of the polishing sheet at the center of the polishing sheet (the center between the chucks) is reduced. The reduction was 0 mm.

Comparative Example 1 A nylon pile having a fiber diameter of 13.7 μm and a length of 0.6 mm was electrostatically planted on a plain woven fabric made of a blended yarn of rayon fiber and polyester fiber and having a surface density of 200 g / m ² . The flocking sheet was used as a polishing sheet.

Comparative Example 2 A fiber web was formed using sea-island type splittable fibers as shown in FIG. 1 and entangled.
An entangled fiber web made of a nylon fiber having a fiber diameter of 2.5 to 3.5 μm formed by dissolving and removing the sea component of the splittable fiber was fixed with a urethane resin of an amount of about 40 g / m ² , and the area density was 100 g. / M ² , 0.5 mm thick nonwoven fabric (Exeine, manufactured by Toray Industries, Inc.) was used as the polishing sheet.

(Comparative Example 3) A plain fabric (Zavina, manufactured by Kanebo Co., Ltd.) having a surface density of 200 g / m ² and a thickness of 0.3 mm mainly composed of ultrafine polyester fibers having a fiber diameter of 5.1 μm was used as an abrasive sheet. .

(Comparative Example 4) Except that a drawn polyester fiber having a fiber diameter of 12.4 μm and a fiber length of 38 mm was used, the area density was 100 g /
An entangled nonwoven fabric having a thickness of m ² and a thickness of 0.5 mm was formed. This entangled nonwoven fabric was used as a polishing sheet.

(Evaluation of Polishing Characteristics) Using a test tape obtained by cutting the polishing sheets of Examples 1 and 2 and Comparative Examples 1 to 4 to 50 mm, a diamond slurry having an average particle size of 0.3 μm (abrasive particle concentration = 0. 4 mass%), using a testing machine as shown in FIG.
The aluminum disk substrate subjected to the phosphor plating treatment was textured. Note Rotation speed of disk substrate: 250 rpm Oscillation number: 1000 times / min Oscillation amplitude: 2 mm Pressing pressure of test tape onto disk: 196 kPa Feeding speed of test tape: 5 mm / second Polishing time: 50 seconds Slurry supply amount: 10 ml / Min

After the texturing, the surface of the disk substrate was observed with an electron microscope to confirm whether or not there were any large scratches. Further, the average surface roughness Ra of the disk substrate (the smaller the value, the better), and the maximum depth Rv of the concave portion from the average point of the irregularities on the surface of the disk substrate (the larger the numerical value, the deeper (larger) the flaw is. Was measured using a surface roughness / fine shape measuring device (Tencor P-12; manufactured by Tencor). Further, a change in weight before and after the texture processing, that is, a grinding amount was calculated. These results are shown in Table 1.
As shown in FIG. From these results, it can be seen that the polishing sheet of the present invention can be polished uniformly without causing significant damage to the substrate surface, and has a large amount of grinding.

[0056]

[Table 1]

[0057]

The polishing sheet of the present invention comprises a nonwoven fabric containing fibrillated and entangled fibers. Since it contains the fibrillated fibers and is excellent in holding fine abrasive particles, the base material surface can be polished uniformly to form a fine texture. In addition, since the fibrillated fibers are entangled, the fibers are fixed so as to have a certain degree of flexibility, and the abrasive particles are not forcibly pressed against the surface of the base material. It is difficult to attach. Furthermore, since the fibrillated fibers are entangled, the flexibility of the fibers is suppressed as compared with the conventional case where fibers having a fiber diameter of 10 μm or less are used, and the abrasive particles can be pressed firmly against the substrate surface. For,
This is a polishing sheet with a large amount of grinding. That is, since the fibers are appropriately fixed by the entanglement of the fibrillated fibers, the polishing sheet can appropriately press the abrasive particles against the surface of the base material.

[Brief description of the drawings]

FIG. 1 is an example of a sectional shape of a splittable fiber that can be used in the present invention.

FIG. 2 shows another example of a cross-sectional shape of a splittable fiber that can be used in the present invention.

FIG. 3 shows another example of the cross-sectional shape of the splittable fiber that can be used in the present invention.

FIG. 4 shows another example of the cross-sectional shape of the splittable fiber that can be used in the present invention.

FIG. 5 shows another example of the cross-sectional shape of the splittable fiber that can be used in the present invention.

FIG. 6 shows another example of the cross-sectional shape of the splittable fiber that can be used in the present invention.

FIG. 7 shows another example of the cross-sectional shape of the splittable fiber that can be used in the present invention.

FIG. 8 is an explanatory view showing a state in which a non-magnetic plating base material is textured using the polishing sheet of the present invention.

[Explanation of symbols]

 Reference Signs List A resin component B resin component a resin component b resin component 11 slurry supply nozzle 12 disk substrate 13 test tape 14 pressing roller

Claims (10)

[Claims] 1. A polishing sheet comprising a nonwoven fabric containing fibrillated and entangled fibers. 2. The polishing sheet according to claim 1, wherein the fibrillated fibers are liquid crystal polyester fibers. 3. The polishing sheet according to claim 2, wherein the liquid crystal polyester fiber comprises a copolymer of p-hydroxybenzoic acid and 2-hydroxynaphthalene-6-carboxylic acid. 4. The polishing sheet according to claim 1, wherein the polishing sheet contains 3 mass% or more of fibrillated fibers. 5. A fiber having a fiber diameter of 1 in addition to the fibrillated fiber.
The polishing sheet according to any one of claims 1 to 4, comprising ultrafine fibers of 0 µm or less. 6. The polishing sheet according to claim 5, wherein the ultrafine fibers include polyester ultrafine fibers. 7. The polishing sheet according to claim 1, wherein the polishing sheet is entangled by a water flow. 8. The polishing sheet according to claim 1, further comprising a layer containing hydrophilic fibers. 9. The polishing sheet according to claim 1, further comprising a reinforcing layer. 10. The polishing sheet according to claim 1, wherein the polishing sheet is used for manufacturing a magnetic recording medium.