JP2003340728A - Grinding sheet and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding sheet of grinding performance and flexibility, and excellent integrity of a grinding material with a sheet base material without any interlaminar separation accompanied by lamination of the grinding sheet of a lamination structure or any trouble of mixture of foreign matters between laminates, and to provide a manufacturing method for easily and efficiently manufacturing the grinding sheet. <P>SOLUTION: A grinding material 2 is distributed in an inclined manner in the thickness direction in a sheet base material 3 of a single layer formed of an elastic material, and the grinding material is closer to a grinding sheet 1 exposed to a surface on the side of high distribution density. In the manufacturing method of the grinding sheet 1, a raw elastic material is formed of at least two reactive raw materials, a dispersoid of the grinding material is manufactured by performing the kneading and dispersion of the grinding material in the first reactive raw material in advance, the dispersoid of the grinding material, the first reactive raw material and a second reactive raw material are mixed to manufacture a liquid mixture with the grinding material uniformly dispersed, and the liquid mixture is centrifugally casted. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing sheet mainly used for precision polishing, and more particularly to a polishing sheet suitably used for polishing an end face of an optical connector ferrule and a hard disk.

[0002]

2. Description of the Related Art When polishing precision parts such as optical connector ferrules, hard disks, magnetic disks and semiconductor chips, a polishing sheet for precision polishing is used. For example, when trying to polish the end face of an optical connector ferrule, the end face of the optical connector ferrule is not scratched, and the end face of the ferrule and the optical fiber is polished so as not to cause a step difference. It is necessary to reduce the amount and improve the optical characteristics.

Conventionally, for polishing such precision parts, for example, particles of an abrasive such as alumina or silica having a particle size of 5 to 30 μm, for example, on a base material of a polyester film having a thickness of 50 to 100 μm, The one provided with a polishing layer made of a binder resin for fixing the particles of the abrasive is used.

[0004]

However, in order to prepare such a conventional polishing sheet, after subjecting a polyester film as a base material to corona treatment and primer treatment,
It is necessary to prepare a binder resin in which an abrasive is precisely dispersed and which is mixed with an adhesive component with a base material, is applied on the base material by a gravure reverse method, and then cured and adhered by heating etc. The process is very complicated. Therefore, there are problems that the manufacturing cost of the polishing sheet is considerably high, that the abrasive material falls off from the binder resin, and that the life of the polishing sheet is short.

Further, for example, as a polishing means for polishing the end face of the optical connector ferrule into a spherical shape, the polishing means disclosed in Japanese Patent Laid-Open No. 9-248771 is known. That is, the polishing means is configured by disposing an elastic pad on a rotating metal plate and fixing a polishing sheet on the elastic pad. Then, in order to polish the end face of the optical connector ferrule by the polishing means, while the rotating metal plate is rotated, the end face is pressed onto the polishing sheet while rotating the optical connector ferrule itself so that the polishing sheet is elastic. The end face of the optical connector ferrule is polished into a spherical shape by utilizing the bending of the body pad.

However, in order to polish by such a polishing means, there is a problem in that both the polishing sheet and the elastic pad have to be prepared with high precision, and both must be surely bonded and integrated. Further, when dust or dust is caught between the polishing sheet and the elastic pad during the bonding, the polishing surface becomes non-uniform, which may cause polishing failure.

The applicant of the present invention, as a polishing sheet for solving the above-mentioned problems, mixes a filler (abrasive) and a resin material, pours them into a mold, and uses different fillers in a state where the resin material is primary cured. A functional resin structure (polishing sheet) is proposed in which a resin material is mixed and poured, and both resin materials are chemically bonded (Japanese Patent Application No. 2001-34721).
5). However, the one proposed in this application has a constitution in which two or more functional layers are chemically bonded, has a simpler process than the above-mentioned conventional example, is less likely to cause delamination, and has excellent polishing performance. However, since there are many restrictions on manufacturing such as stacking timing, further improvement is required in terms of quality control and manufacturing cost.

In view of the above problems of the prior art, the present invention has no troubles such as delamination and mixing of foreign matters into the layers, which is seen in a laminated body, and has excellent polishing performance. An object of the present invention is to provide a polishing sheet excellent in the integrity of the polishing material and the sheet base material, and to provide a method of manufacturing the polishing sheet, which can easily and efficiently manufacture the polishing sheet.

[0009]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found the following inventions. That is, the present invention is characterized in that the abrasive is distributed in the thickness direction in a single-layer sheet base material made of an elastic body, and the abrasive is exposed on the surface on the side of high distribution density. Provide a polishing sheet. In the polishing sheet, preferably, 60% by weight or more of the polishing material is distributed within a range of a surface having a high distribution density (hereinafter, also referred to as “surface”) and a thickness of 200 μm. Further, the JIS-A hardness measured by applying a pressing needle to the surface of the abrasive having a low distribution density (hereinafter, also referred to as “back surface”) is preferably 30 to 97. As the elastic body, thermosetting polyurethane can be preferably used. Further, the present invention is characterized in that, in the polishing sheet, the abrasive is exposed by grinding.

In the polishing sheet having such a structure, since the polishing material has a gradient distribution in the thickness direction, it has both excellent polishing performance and elastic performance similar to those of the laminated structure, and
Since it is composed of a single-layer sheet base material, it has a unique effect that it can be molded once as compared with a laminated structure, and there is no risk of foreign matter mixing between layers.

Further, according to the present invention, a mixed liquid for molding an elastic body, in which an abrasive is kneaded and dispersed, is centrifugally molded, and the abrasive is distributed in a gradient direction in the thickness direction of a sheet base material made of an elastic body to form a single layer A polishing sheet manufacturing method for manufacturing a polishing sheet, wherein a mixture liquid for molding an elastic body comprises two or more reactive raw materials, and an abrasive is kneaded and dispersed in one reactive raw material in advance. Polishing is prepared, and the abrasive dispersion is mixed with the one reactive raw material and another reactive raw material to prepare a mixed liquid in which the abrasive is uniformly dispersed in the elastic raw material. A method for manufacturing a sheet is provided.

Further, in the present invention, in the method for producing an abrasive sheet, preferably, a surface (that is, a surface) of the centrifugally molded sheet base material having a high distribution density of the abrasive material is ground to remove the abrasive material. Is exposed.

According to such a method for producing a polishing sheet, it is possible to easily and efficiently produce a polishing sheet which has both excellent polishing performance and elastic function, and at the same time is free from the risk of foreign matter. In particular, a method is adopted in which an abrasive dispersion is prepared by kneading and dispersing an abrasive in one reactive raw material in advance, and the abrasive dispersion is mixed with one reactive raw material and another reactive raw material. This makes it possible to prepare a mixed liquid for elastic body molding in which the abrasive is uniformly dispersed. By centrifugally molding this, the density of the abrasive material on the outer side in the thickness direction of the elastic body (sheet base material) is increased by centrifugal force, and a polishing sheet uniformly dispersed in the surface direction is easily and efficiently manufactured. be able to.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a polishing sheet and a method for manufacturing the same according to the present invention will be described in detail with reference to the drawings.

In the polishing sheet according to the present invention, as shown in FIG. 1, in the single-layer sheet base material 3 made of an elastic material, the polishing material 2 has a gradient distribution in the thickness direction and a high distribution density side. The surface 4 has the abrasive 2 exposed on the surface.

As the elastic body used as the sheet base material 3, a thermosetting polyurethane can be preferably used in which the raw material is liquid and has reactivity, and the raw material is mixed and cured by heating or the like to be an elastic body. . Polyurethane has a viscosity of a mixture liquid for elastic body molding (measurement of ease of pouring) by adjusting the type and composition of polyol and isocyanate, which are reactive raw materials, the type and composition of crosslinking agent, and the mixing ratio of these. There is an advantage that the physical properties of the obtained elastic body can be controlled. In addition, since isocyanate also functions as an adhesive, it has a unique effect that the abrasive can be firmly fixed in the elastic body during the step of heating and curing the mixed liquid for molding the elastic body. An excellent polishing sheet can be created.

Polyol, which is one of the reactive raw materials of polyurethane, is not particularly limited, and polyether polyols such as polytetramethylene glycol, polypropylene glycol and polyethylene glycol, condensed polyesters such as polyethylene adipate and polybutylene adipate. Known polyhydric alcohols such as system polyols, ring-opening-polymerized polyester polyols of polycaprolactam, polycarbonate polyols, and polyolefin polyols can be used. Among them, the polyether polyol can be preferably used because it has a viscosity suitable for centrifugal molding and facilitates operations such as mixing and pouring.

Isocyanate which is the other reactive raw material of polyurethane is not particularly limited, and aromatic isocyanates such as diphenylmethane diisocyanate and tolylene diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate and isophorone diisocyanate. Any known one can be used. Among them, the reaction is slow, and there is a time margin from mixing to injection into the centrifugal molding die, and
Aliphatic isocyanate, which can further increase the inclination of the abrasive by centrifugal force even after the injection, can be preferably used.

The cross-linking agent is also not particularly limited, and alcohol cross-linking agents such as ethylene glycol and butanediol, 4,4'-diamino-diphenylamine, 3,3'-dichloro-4, Aromatic diamines such as 4'-diaminodiphenylamine (MOCA),
Amine-based cross-linking agents such as aliphatic diamines such as ethylenediamine and butylenediamine can be appropriately selected and used according to hardness and reactivity.

On the other hand, the abrasive is not particularly limited, and examples thereof include alumina, cerium oxide, silicon oxide, zirconium oxide, silicon carbide, iron oxide,
It is possible to select and use one kind or two or more kinds from substances having abrasiveness such as titanium oxide, strontium titanate, calcium carbonate and diamond. The particle size and blending amount of the abrasive are not particularly limited, and can be appropriately adjusted depending on the use of the abrasive sheet and the degree of ubiquity due to centrifugal molding, but the particle size of the abrasive is generally about 0.1 to 10 μm. The compounding amount of the abrasive with respect to 100 parts by weight of the elastic raw material is preferably about 3 to 100 parts by weight.

Next, a method of manufacturing the polishing sheet according to the present invention will be described.

First, any one of the above-mentioned reactive raw materials is selected, and an abrasive is added to the reactive raw material, kneaded, and dispersed to obtain a uniform abrasive dispersion. To do. The reactive raw material for kneading and dispersing the polishing material in advance is not particularly limited, but a material having low reactivity is preferable. Therefore, for example, when polyurethane is used as the elastic body as described above, it is preferable to select polyol as the reactive raw material for kneading and dispersing the abrasive in advance. By preparing an abrasive dispersion using a polyol, a stable dispersion can be obtained, and the abrasive can be uniformly dispersed in the polyurethane molding mixture without affecting the polyurethane forming reaction. it can.

Further, in the case of producing an abrasive dispersion, in order to uniformly disperse the abrasive in the reactive raw material, a known kneading means such as a bead mill or a paint roll is usually used.

The case where the elastic body is polyurethane will be specifically described. First, abrasive particles are added to and mixed with a polyol whose viscosity has been lowered by heating, and then the mixture is kneaded with a roll-type kneader such as a paint roll. Then, an abrasive dispersion is prepared. Next, the remaining polyol and the cross-linking agent were mixed at a predetermined ratio, defoamed under reduced pressure, and then a predetermined amount of isocyanate was added and mixed, and the abrasive was uniformly dispersed in the elastic material, and was suitable for casting. A polyurethane molding mixture having a predetermined viscosity is prepared.

Then, the thus-prepared mixed liquid is immediately poured into a mold of a centrifugal molding machine which is heated to a predetermined temperature in advance and rotated, and the mold is rotated while being heated, and a centrifugal force is exerted. The elastic raw material is cured.

An example of the centrifugal molding machine used for centrifugal molding is shown in FIG. That is, as the centrifugal molding machine 10, a drive shaft 12 rotated by a motor or the like, a cylindrical cup-shaped mold 13 attached to the tip of the drive shaft and rotatably supported by a cantilever, The heater 14 fixedly arranged on the outer periphery of the mold 13, a heat insulating case 15 covering the heater 14, and a hatch 16 opened in the heat insulating case 15.
And a door 17 for opening and closing the hatch 16 can be used.

In centrifugal molding, it is preferable to adjust the raw material type, composition, mixing ratio, temperature, etc. so that the viscosity of the mixed solution injected into the mold is 100 to 5000 mPa · s. If it is less than 100 mPa · s, the liquid will enter the gap between the molds and it will be difficult to release the mold after curing. The viscous resistance received by is too strong against the centrifugal force, and it becomes difficult to make a dense gradient distribution outward (inner peripheral surface of the centrifugal molding die). The term "viscosity" used herein means a value measured by a B-type viscometer at the liquid temperature (for example, 100 ° C in the case of polyurethane) of the mixed liquid for elastic body molding immediately before being poured into the centrifugal molding die.

When the abrasive is distributed in a gradient,
60% by weight of abrasive material within a thickness of 200 μm from the surface
It is preferable to set the centrifugal molding conditions (rotation speed, temperature, etc.) so that the above is distributed. By thus providing the gradient distribution, it becomes possible to impart desired polishing performance to the front surface side of the polishing sheet. If 60% by weight or more of the abrasive is not distributed within the range of 200 μm from the surface and is widely distributed over the entire polishing sheet, not only is it difficult to obtain polishing characteristics for precision polishing, but also the elasticity of the back surface side It is not preferable because it may impair the function of the body.

At the initial stage of centrifugal molding, the abrasive dispersed in the mixture for molding the elastic body is likely to move to the inner surface (outside) of the die due to the difference in specific gravity, but the reaction proceeds and the elastic body is molded. As the viscosity of the mixed liquid for use increases, it becomes more difficult to move, and when it hardens to become an elastic body, the abrasive is embedded and fixed.

In this way, there is a large amount of abrasive on the inner surface (outside) of the die, and there is substantially no abrasive on the inner surface of the hollow surface. A sheet (hereinafter, also referred to as a molded article for polishing sheet) is formed.

Further, the molded article for an abrasive sheet thus obtained has a thin coating on the surface thereof and the abrasive is buried in the sheet base material. Therefore, the surface of the molded article is ground. It is preferable to expose the abrasive. As a grinding method, a method of grinding a cylindrical jig for the abrasive sheet molded body obtained by the centrifugal molding, a method of grinding using a cylindrical grinder, or a flat sheet cut out from the abrasive sheet molded body,
A method of fixing on a pedestal and grinding using a flat plate grinder can be mentioned.

The hardness of the polishing sheet thus obtained is 3 according to JIS-A hardness measured by pressing a pressing needle on the surface (ie, the back surface) on the side where the distribution density of the abrasive is low.
It is preferably 0 to 97. When the JIS-A hardness is less than 30, tackiness appears in the elastic body, and when used as a polishing sheet, polishing scraps may adhere to the polishing sheet and enter the polishing surface, which may have a bad effect. Further, if the JIS-A hardness exceeds 97, it is difficult to bend following the object to be polished, and it becomes difficult to polish it into a predetermined shape. The "JIS-A hardness" in the present invention means JI.
According to SK 7312 (method A), laminating the polishing sheets so as to have a thickness of about 3 mm.
The hardness measured by applying a push needle of a type hardness meter.

In the polishing sheet according to the present invention, not only a large amount of the abrasive is distributed on the surface used as the polishing surface,
The abrasive is firmly fixed to the sheet base material by hydrogen bonding or the like due to the curing reaction. Therefore, the polishing sheet,
Even when a force is applied to the polishing of the optical connector ferrule or the like, the abrasive material is less likely to be detached, and the polishing performance is excellent in that scratch scratches and the like are less likely to occur.

On the other hand, there is substantially no abrasive on the back surface (air surface) side, the elasticity is not hindered by the abrasive, and the sheet base material has desired elasticity. Therefore, for example, in polishing an optical connector ferrule, the optical connector ferrule is easily bent according to the pressing force of the optical connector ferrule, and the tip of the optical connector ferrule can be polished into a desired curved shape.

The polishing sheet according to the present invention is obtained by centrifugal molding by injecting the mixed solution once into the front surface side portion and the back surface side portion having the above-mentioned characteristics. Therefore, compared with the conventional one that is configured by stacking layers, it can be manufactured in a smaller number of steps, and there is no problem of foreign matter or air mixing between the layers unlike the conventional one, and it has excellent integrity. Becomes

In the above embodiment, the case where the abrasive having a larger specific gravity than the elastic body is mixed has been described, but the present invention is not limited to this, and an abrasive having a smaller specific gravity than the elastic body is used. It is also possible to distribute the abrasive on the air surface side.

Although polyurethane is used as the elastic body, the present invention is not limited to this, and any resin can be used as long as it is an elastic body made of a plurality of reactive raw materials.

Further, in addition to the abrasive, the abrasive sheet of the present invention may have a slipperiness imparting material such as fluorinated graphite, zinc stearate, and metal oxide powder, an azine compound, and a quaternary ammonium as required. A charge control agent such as a salt or a metal-containing azo dye, or a conductivity-imparting material such as conductive carbon can be added.

[0039]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Elastic Material) Polytetramethylene glycol (Hodogaya Chemical Co., Ltd., PTMG1000SN, hydroxyl value 111.8 mgK) as a polyol which is a raw material of polyurethane
OH / g), as an isocyanate, a mixture of two kinds of aliphatic isocyanate (Sumitomo Bayer Urethane Co., Sumidule N3300, NCO = 22% and Mitsui Takeda Chemical Co., Cosmonate NBDI, NCO = 40.8%).
1: 1) and an aromatic diamine-based curing agent (Sumitomo Bayer Urethane Co., Ltd., Vitec 1604, amine equivalent 121) were used as a curing agent to prepare an elastic material.

(Preparation of Abrasive Dispersion) Polyol 8
To 0 parts and 40 parts of aromatic diamine, 100 parts of high-purity alumina having an average particle diameter of 0.4 to 0.5 μm (UA-5053 true specific gravity = 3.97, manufactured by Showa Denko KK) was added as an abrasive, and 2 Pre-mixing was performed for 10 minutes at 100 rpm using a shaft planetary type mixing and kneading machine (manufactured by Tokushu Kika Kogyo Co., Ltd.), and then kneaded and dispersed by a paint roll (Zero Zero manufactured by Inoue Seisakusho) to obtain an alumina dispersion.

(Centrifugal molding) 25 parts of an aromatic diamine curing agent heated to 100 ° C. to be dissolved, 100 parts of polytetramethylene glycol, and 18.8 parts of the above-mentioned alumina dispersion were placed in an ordinary rotary stirrer. And stir for 2 minutes at 100 ℃
After defoaming overnight in the vacuum oven of No. 6, 61.6 parts of the above isocyanate was added and mixed with a rotary mixer so as not to bite the foam to prepare a mixed solution. Then, using a centrifugal molding machine equipped with a cup-shaped cylindrical metal mold having a diameter of 340 mm and a width of 350 mm, a mold release agent was applied in advance and 120 ° C.
The mixed solution was poured at one time while rotating the mold heated at 150 rpm at 150 rpm, and after pouring completely, 1500
Rotate to rpm and hold for 10 minutes, then 2
The number of rotations was reduced to 50 rpm, the temperature was maintained for 50 minutes, and heat curing was performed. After that, remove the mold from the mold, and at 110 ℃ 1
After-curing for 2 hours, a molded body for polishing sheet having a thickness of 0.5 mm was obtained.

The cross section of the obtained molded article for polishing sheet is SE
When observed with M, the range in which the abrasive is distributed is 2 from the surface.
It was 0 μm. Further, the rubber hardness measured by stacking four molded articles for polishing sheets and applying a pressing needle to the surface having a small amount of abrasive distribution was 89 degrees in JIS-A hardness.

Furthermore, since an extremely thin polyurethane film was formed on the surface (mold surface) of the abrasive sheet molded body in which a large amount of the abrasive was distributed, after fixing the sheet piece cut out from the molded body to the pedestal. By polishing and removing the film on the surface of the sheet piece with a rotating rubber grinding wheel, a polishing sheet having an abrasive exposed on the surface was obtained. The center line surface roughness Ra of the obtained polishing sheet was 0.8 μm.

(Polishing of End Face of Optical Connector Ferrule) The polishing sheet produced as described above was directly attached to the rotating metal plate without interposing the elastic pad, and finish polishing of the ferrule end face of the optical connector was performed. As a result, no polishing scratches were found on the end face of the optical connector ferrule, there was no step between the ferrule and the optical fiber, and the return loss was 4
An optical connector ferrule of 0 dB or more could be obtained.

[0045]

As described above, according to the polishing sheet of the present invention, a large amount of the abrasive is integrally distributed on the one surface of the single-layer sheet base material made of an elastic material and exposed. Since the other surface consists essentially of an elastic body,
It has desired elasticity and excellent durability. Further, according to the method for producing a polishing sheet according to the present invention, a polishing sheet excellent in flexibility and integrity can be easily produced by centrifugal molding.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a polishing sheet according to the present invention.

FIG. 2 is a sectional view showing an example of a centrifugal molding machine used in the present invention.

[Explanation of symbols]

1 ... Abrasive sheet, 2 ... Abrasive material, 3 ... Sheet base material (elastic body), 4 ... Abrasive exposed surface, 10 ... Centrifugal molding machine

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Claims (7)

[Claims] 1. A polishing characterized in that an abrasive is distributed in a thickness direction in a single-layer sheet base material made of an elastic body, and the abrasive is exposed on the surface on the side of high distribution density. Sheet. 2. The polishing sheet according to claim 1, wherein 60% by weight or more of the polishing material is distributed within a range of a thickness of 200 μm from the surface having a high distribution density. 3. The polishing sheet according to claim 1, wherein the JIS-A hardness measured by applying a pressing needle to the surface of the abrasive having a low distribution density is 30 to 97. 4. The polishing sheet according to claim 1, wherein the elastic body is thermosetting polyurethane. 5. The polishing sheet according to claim 1, wherein the abrasive is exposed by grinding. 6. A polishing sheet for producing a polishing sheet by centrifugally molding a mixed liquid for molding an elastic body, in which an abrasive is kneaded and dispersed, and distributing the abrasive in an inclined distribution in the thickness direction of a sheet base material made of an elastic body. The method for producing an elastic body, wherein the mixed liquid for elastic body molding comprises two or more reactive raw materials, and an abrasive is kneaded and dispersed in one reactive raw material in advance to prepare an abrasive dispersion. A method for producing a polishing sheet, which comprises mixing a dispersion with the one reactive raw material and another reactive raw material to prepare a mixed liquid for elastic body molding in which an abrasive is uniformly dispersed. 7. The method of manufacturing an abrasive sheet according to claim 6, wherein the surface of the centrifugally molded sheet base material having a high abrasive material distribution density is ground to expose the abrasive material.