JP2003049158A - Abrasive particle and abrasive body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inexpensive abrasive particles having excellent polishing ability which replaces conventional diamond particles as particles for polishing optical connectors. SOLUTION: The abrasive particles are composed of metal oxide particles, having plate-like shape and 10-1,000 nm average particle diameter in a direction of particle plate surface, in which >=50% particles have holes in a thickness direction of the plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a polishing body such as polishing particles and a polishing sheet used for polishing an end face of an optical connector, particularly for rough polishing before finish polishing.

[0002]

2. Description of the Related Art Optical connectors are used in communication using optical fibers to connect optical fibers with each other or with optical fibers and equipment such as an optical / electrical converter. In this optical connector, a glass fiber is fixed to the axial center of a ferrule made of ceramics such as zirconia, and its end face is highly accurately polished in such a ceramic / glass composite structure.

The end face of the optical connector is finished through a plurality of polishing steps such as rough polishing and finish polishing, and the finish polishing has a great influence on performances such as light reflection attenuation rate and connection loss. The finishing polishing has been studied from the viewpoint of improving the accuracy of the optical connector, and for example, Japanese Patent Laid-Open No. 10-277957.
In the publication, it is preferable to use a polishing liquid or a polishing sheet containing silica as a polishing agent.

By the way, a plurality of optical connectors are polished at the same time.
There may be a slight difference in the optical return loss. Upon investigating the cause of this, the polishing state of the ferrule before final polishing had an effect, and when deep scratches were formed on the ferrule polished surface during the rough polishing stage, minute scratches were produced after the final polishing with silica, which had low abrasiveness, as the abrasive. Remained, and the light reflection attenuation rate was lowered.

In the case where the light reflection attenuation factor is low as described above, the minute scratches can be removed by repeating the finish polishing, and the light reflection attenuation factor can be increased to the specified value. However, such re-polishing results in a longer polishing time, which tends to hinder the productivity of the optical connector. Therefore, it is desirable to prevent deep scratches on the ferrule polished surface during the rough polishing.

Conventionally, in the rough polishing, a polishing sheet or a polishing liquid using high hardness diamond particles alone as an abrasive has been used. When diamond particles alone are used as an abrasive, the ceramic ferrule's abrasivity is improved, but the glass fiber part at the center of the axis is excessively abraded to increase the fiber pull-in step, and the ferrule end face becomes chipped or scratched. Cheap.

As a countermeasure, it is considered to use diamond particles having a small particle size and a uniform particle size. Diamond particles are generally adjusted to a specific size by crushing crystals having a relatively large particle size, but in order to make the particle sizes uniform, it is necessary to select, the yield is poor, and the process However, there is a disadvantage in that the cost becomes high because of the complexity.

[0008]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention uses abrasive particles, which are inexpensive and have excellent polishing ability, as an alternative to conventional diamond particles for polishing optical connectors and the like. It is intended to provide a polishing body such as a polished sheet.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies as to the above objects, and as a result, have a metal oxide particle having a specific particle diameter, which has a plate shape and has pores in the plate thickness direction. The present invention has been completed by knowing that the use of the above-mentioned product makes it possible to obtain abrasive particles which are inexpensive and have excellent polishing ability and an abrasive body such as an abrasive sheet using the same.

That is, according to the present invention, the particles have a plate-like shape, and the average particle diameter in the particle plate surface direction is from 10 nm to 1.00.
Abrasive particles characterized by being in the range of 0 nm and 50% or more of the particles being metal oxide particles having pores in the plate thickness direction, in particular, the size of the pores is in the range of 1 nm to 100 nm on average. Abrasive particles having the above-mentioned configuration,
The above-mentioned metal oxide particles are related to the abrasive particles having the above-mentioned constitution, which mainly contains iron or iron and further contains at least one element selected from aluminum, silicon, rare earth elements and zirconium.

Further, according to the present invention, in a polishing body comprising a flexible support and a polishing layer in which the polishing agent is dispersed in a binder, the above-mentioned polishing agent comprises polishing particles having the above-mentioned constitution. The present invention relates to a characteristic polishing body. The abrasive body includes various forms such as a tape shape, a disk shape, and a card shape in addition to the polishing sheet.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the abrasive particles have a plate-like shape and have an average particle diameter in the plate surface direction of 10 nm to 1,000 nm, and 50%.
The above particles are characterized by using metal oxide particles having pores in the plate thickness direction. Such polishing particles can exhibit excellent polishing ability for end face polishing of an optical connector having a ceramic / glass composite structure.

That is, the above-mentioned abrasive particles of the present invention are composed of metal oxide particles whose hardness is essentially lower than that of diamond particles, so that the low-hardness member will not be excessively polished and the low-hardness member will not be excessively polished. On the other hand, since the shape is plate-like and has holes in the plate thickness direction, the number of end faces increases due to these holes, and the polishing ability is improved accordingly. The high-hardness member has excellent polishing properties and can be sufficiently applied to the high-hardness member. In addition, dust generated during polishing is trapped in the above holes, and the effect that polishing residues that cause scratches on the polishing surface is less likely to occur is also obtained.

On the other hand, the conventional diamond particles are excellent in polishing property for high hardness members such as ceramic ferrules, but are low for objects to be polished in which soft members such as glass having lower hardness than ceramics coexist. The hardness member is excessively polished and the desired shape or surface property cannot be obtained.
The present invention overcomes the drawbacks of the diamond particles, exhibits excellent polishing ability for polishing the end face of an optical connector having a ceramic / glass composite structure, and at the same time can prevent the occurrence of polishing scratches. Since no expensive particles such as the above are used, the cost can be reduced.

By the way, ring-shaped iron oxide particles having pores near the center of the particles are already known in the publications of JP-A-61-266311 and JP-A-61-266313, and discotic goethite particles are known. Has been proposed to be used as a magnetic powder for magnetic recording by heating, dehydrating, and reducing it into cyclic magnetite particles, which is modified with cobalt. Further, in Japanese Examined Patent Publication No. 3-21489, iron chloride aqueous solution is added dropwise to an aqueous solution containing sodium hydroxide and alkylamine to precipitate iron hydroxide, and after aging, washing and pH adjustment, hydrothermal treatment is performed. To obtain disc-shaped goethite particles, heat and dehydrate them to obtain annular hematite particles with holes in the center, magnetite particles, gamma iron oxide particles, pigments for paint reinforcement, composite materials, etc. It has been proposed to use as a reinforcing agent, a medical material, and an electronic material as a magnetic powder.

The present inventors have focused their attention on the application of hematite particles as an abrasive among the iron oxide particles having such pores. That is, it is considered that the pores present in the particles increase the particle end faces to obtain a high polishing ability, and that the polishing residue is trapped in the pores, and the polishing residue is less likely to be generated. We extensively studied the particle size of hematite particles, the size of pores, and the distribution of the number of pores. As a result, in addition to the plate-shaped hematite particles having a hole in the center, plate-shaped hematite particles having many holes in the particles were also obtained, and it was found that these particles all exhibit excellent performance as an abrasive. . Also, some of the iron in the hematite particles may be aluminum or zirconium,
It was also found that by substituting with another metal element, the hardness of the iron oxide particles can be controlled, and thereby a more excellent polishing ability can be exhibited.

A method for producing hematite particles will be described below as an example of the method for producing abrasive particles of the present invention. First, an aqueous iron chloride solution is added dropwise to an alkaline aqueous solution, for example, an aqueous solution containing sodium hydroxide and an alkylamine, and the mixture is stirred to precipitate iron hydroxide. At that time, since the liquid temperature influences the particle shape, particle size, pore size and number, etc., an appropriate temperature is selected. Generally, the higher the liquid temperature, the larger the particle size, the larger the number of pores,
On the contrary, the lower the particle size, the smaller the particle size and the number of holes, and the shape has one hole in the center. The liquid temperature is usually preferably in the range of 0 to 40 ° C. Even if the temperature is lower than 0 ° C, the change in particle size is small,
There is a disadvantage that the cooling cost becomes high, and if it is higher than 40 ° C., amorphous substances other than plate-like substances are likely to be mixed.

Next, the iron hydroxide thus precipitated is aged, washed and adjusted to pH by adding sodium hydroxide or the like, and then hydrothermally treated in an autoclave,
Plate-like goethite particles are obtained. Here, the hydrothermal treatment temperature is usually preferably in the range of 120 to 250 ° C. When the temperature is lower than 120 ° C., it is difficult to grow crystals into a plate shape, and when the temperature is higher than 250 ° C., a high water vapor pressure is generated, which increases the load on the apparatus, which is not preferable.

Then, the plate-like goethite particles are subjected to a heat dehydration treatment to form plate-like hematite particles (α-Fe ₂ O ₃ particles) having pores in the particles. Before applying the heat dehydration treatment, it is desirable to perform a deposition treatment with silica or alumina for the purpose of preventing inter-particle sintering during heat dehydration. Heat dehydration treatment is performed in air,
Usually, it is good to carry out in the temperature range of 200 to 800 ° C. Two
When the temperature is lower than 00 ° C., pores are not easily formed in the particles, and when the temperature is higher than 800 ° C., sintering between particles is likely to occur and the plate-like shape is likely to collapse.

The hematite particles produced by such a method have a plate-like particle shape and an average particle diameter of 10 n.
It is in the range of m to 1,000 nm. Average particle size is 10
If it is less than nm, the polishing ability is small, and if it exceeds 1,000 nm, the polished surface tends to be rough. Whether the particle shape is plate-like is determined by the shadowing method (the plate thickness is measured from the length of the shadow when metal is vapor-deposited from an oblique direction, and compared with the particle diameter to determine whether it is plate-like or not. Method). Further, in the case of the abrasive body in which the hematite particles are dispersed in the polishing layer, the cross-section observation method (the plate thickness is measured from the cross-section observation and compared with the particle diameter obtained from the surface observation to determine whether it is plate-like It can be confirmed by the method of determining whether). The plate ratio (plate thickness / particle diameter) is usually preferably in the range of 2 to 20.

Although almost all the hematite particles have pores in the plate thickness direction, one or more pores are present in each particle. The size (that is, diameter) of the holes should be in the range of 1 nm to 100 nm on average. If it is less than 1 nm, the effect of capturing polishing residue becomes small,
If it exceeds 100 nm, the effect of improving the polishing ability becomes small.
The size of the holes in the plate thickness direction is preferably in the range of 5 to 90% of the particle diameter in the particle plate surface direction. The above-mentioned holes mean through-holes or dents, and such holes are white or particles that appear whitish than the particles themselves when observed by a transmission electron micrograph. For the hole portion, the blackness degree of the portion without particles is 0, and the blackness degree of the particle portion without holes is 10
In this case, the blackening degree is 8 or less. The magnification of a transmission electron micrograph varies depending on the particle diameter and pore diameter of the plate-like particles to be observed, but is usually 1 to 1,000,000 times the magnification at which pores appear to be 1 mm to 10 mm.

Further, the above-mentioned hematite particles are mainly composed of iron or iron. In the above-mentioned production method, when the iron hydroxide is precipitated, aluminum chloride or chloride is added to the aqueous solution of iron chloride. When other metal salts such as zirconium are added, hematite particles finally containing these metal elements, that is, metal oxide particles having a structure in which a part of iron in the hematite particles is replaced with the other metal element described above. Can be generated. The other metal elements include aluminum and zirconium, as well as silicon and rare earth elements. By substituting these elements, the hardness of the iron oxide particles can be controlled, and thereby the polishing ability can be further enhanced. .

Although the above examples relate to iron or iron oxide-based particles mainly composed of iron, the abrasive particles of the present invention are not limited to this, and the shape of the particles produced by the same method as described above is a plate. As long as the particles have an average particle diameter in the plate surface direction in the range of 10 nm to 1,000 nm and have pores in the plate thickness direction, various metal oxide particles are included.
At that time, all of the metal oxide particles, that is, 100
% Need not have the above holes, and 50% or more of the particles may have the above holes.

In the present invention, the plate-shaped metal oxide particles represented by such hematite particles as the abrasive particles exhibit the above-mentioned excellent polishing ability, so that they are used for polishing liquids and polishing bodies such as polishing sheets. A polishing liquid and a polishing body that are optimal as polishing agents, and that are inexpensive and have excellent polishing ability for polishing optical connectors and the like can be provided. The abrasive body of the present invention will be described in more detail below.

The polishing body of the present invention is provided with a polishing layer in which a polishing agent is dispersed in a binder on a flexible support, and has various forms such as a sheet shape, a tape shape, a disk shape and a card shape. As the above-mentioned abrasive, the abrasive particles of the present invention, that is, the particles have a plate shape, and the average particle diameter in the particle plate surface direction is in the range of 10 nm to 1,000 nm,
Further, the main feature is that 50% or more of the particles are metal oxide particles having pores in the plate thickness direction.

As the binder for dispersing the abrasive, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl alcohol copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, vinyl chloride. -Hydroxyl group-containing alkyl acrylate copolymer resin, nitrocellulose, polyester resin, polyurethane resin, etc.,
Of these, one kind or a combination of two or more kinds is used. In particular, it is preferable to use a vinyl chloride resin and a polyurethane resin together, or to use a polyester resin. As the above polyurethane resin, polyester polyurethane, polyether polyurethane,
Examples include polyether polyester polyurethane, polycarbonate polyurethane, and polyester polycarbonate polyurethane. These binders are used for the abrasive particles 10
5 to 45 parts by weight, preferably 10 per 0 parts by weight
It is used in a proportion of about 40 parts by weight.

In addition to the above-mentioned binder, a thermosetting cross-linking agent which bonds with a functional group contained in the binder and cross-links may be used together. As such a cross-linking agent, tolylene diisocyanate, hexamethylene diisocyanate,
Various polyisocyanates such as isophorone diisocyanate, a reaction product of these isocyanates with a compound having a plurality of hydroxyl groups such as trimethylolpropane, and a condensation product of the above isocyanates are used. These crosslinking agents are usually used in a proportion of 5 to 30 parts by weight per 100 parts by weight of the binder.

In addition to the above-mentioned abrasive and binder, a dispersant for improving the dispersibility of the abrasive and a lubricant for imparting lubricity can be added to the abrasive layer. In addition, carbon black can be added to prevent charging. As the dispersant, any of the conventionally known dispersants can be used. As the lubricant, solid lubricants such as graphite and molybdenum disulfide, and conventionally known liquid lubricants can be used alone or in combination of two or more. Among these lubricants, fatty acids having 12 to 24 carbon atoms are preferably used.

When a lubricant is used, it is preferable to employ a method of directly adding the lubricant to the coating liquid for forming the polishing layer, which does not require a separate step from the viewpoint of productivity.
In this case, the ratio of the lubricant such as fatty acid is 0.2 to 10 parts by weight, preferably 0.5 to 5 parts by weight, per 100 parts by weight of the abrasive. Further, it is desirable that the carbon black for antistatic is usually 0.1 to 50 parts by weight per 100 parts by weight of the abrasive.

As the flexible support, any conventionally used non-magnetic support can be used. Specifically, it is made of polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, cellulose triacetate, polycarbonate, polyamide, polyimide, polyamideimide, polysulfone, aramid, aromatic polyamide, etc., and usually has a thickness of 3 to 300 μm. Film or sheet of is used.

The abrasive body having the above-mentioned structure of the present invention is, for example,
Abrasive in organic solvent, its binder, if necessary dispersant,
It can be prepared by preparing a coating liquid for forming a polishing layer, which is obtained by mixing and dispersing a lubricant, carbon black, etc., coating the coating liquid on the above flexible support, and drying.

The organic solvent used for preparing the coating solution is
Aromatic solvents such as benzene, toluene, xylene, ketone solvents such as acetone, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate,
In addition to acetic acid ester solvents such as butyl acetate, carbonic acid ester solvents such as dimethyl carbonate and diethyl carbonate, alcohol solvents such as ethanol and isopropanol, hexane, tetrahydrofuran, dimethylformamide and the like can be mentioned.

If the thickness of the polishing layer thus formed is too thick, the contact between the ferrule and the polishing sheet will be poor. Therefore, the thickness is preferably 30 μm or less, usually 1 to 30 μm, and preferably 2 to 25 μm. More preferably.

In the preparation of the polishing body, a coating liquid for forming a polishing layer is applied onto a flexible support, dried and, if necessary, surface treated by a calendar using a cotton roll, a plastic roll or a metal roll. You may go.
By carrying out this calendering treatment, the surface roughness of the polishing layer can be adjusted well, and by doing so, more favorable results can be obtained in improving the finished surface of the ferrule and preventing scratches.

[0035]

EXAMPLES The present invention will be described in more detail below by way of its examples. However, the present invention is not limited to these examples. In each of the following examples, "parts" means "parts by weight".

Example 1 <Production of plate-shaped alpha iron oxide particles having pores> The following two types of aqueous solutions were prepared. Solution A: Ferric chloride (FeCl ₃ .6H ₂ O) 20 g Water 500 cc Solution B: Sodium hydroxide 30 g Monoethanolamine 50 cc Water 1,000 cc

The above liquids A and B were kept at 12 ° C.,
The liquid A was added dropwise to the liquid B over about 1 hour with stirring. After completion of dropping, the mixture was further stirred for 1 hour. The precipitate thus obtained is left at room temperature for about 20 hours,
Wash with pure water, adjust the pH to 11.3 by adding sodium hydroxide aqueous solution, and use an autoclave at 150 ° C.
Was subjected to hydrothermal treatment for 1 hour. By this hydrothermal treatment, plate-like goethite (α-FeOOH) particles were obtained.

For the plate-like goethite particles, Si
An aqueous solution of sodium silicate was added with stirring so that the content of O ₂ was 1% by weight, the pH was adjusted to 7.3 with hydrochloric acid, and coating with SiO ₂ was performed. After filtering and drying, the product was heated and dehydrated in air at 600 ° C. for 1 hour.
By this heat dehydration treatment, alpha iron oxide (α-Fe ₂ O ₃ ) particles having pores were obtained. This particle was a plate-like particle having an average particle diameter of 65 nm in the particle plate surface direction and having pores with an average diameter of 30 nm near the center. FIG. 1 is an electron micrograph of the alpha iron oxide particles.

[0039]   <Coating liquid components for forming polishing layer>     Plate-shaped alpha iron oxide particles having pores 200 parts     (Average particle diameter: 65 nm, average diameter of pores: 30 nm)     Vinyl chloride-vinyl acetate copolymer 30 parts     ("VAGH" made by UCC)     Polyurethane resin 25 parts     ("Byron UR8300" manufactured by Toyobo)     Methyl ethyl ketone 150 parts     150 parts of toluene     Cyclohexanone 130 parts

After stirring and mixing the above-mentioned coating liquid components,
It was dispersed by a sand mill to prepare a coating liquid for forming a polishing layer. This coating solution is applied to one surface of a flexible support made of polyethylene terephthalate film having a thickness of 75 μm so that the thickness after calendaring is 10 μm,
Dried. After being mirror-finished with a calendar, it was cut into a predetermined width to produce a polishing tape.

Example 2 The average particle diameter in the particle plate surface direction was the same as in Example 1 except that the holding temperature of both solutions was changed from 12 ° C. to 24 ° C. when the solution A was dropped into the solution B. Is 210 nm and the diameter is 10
Alpha iron oxide particles having a large number of 30 nm pores were obtained.
FIG. 2 shows an electron micrograph of the alpha iron oxide particles. Using the alpha iron oxide particles, a polishing tape was prepared in the same manner as in Example 1.

[0042] As Example 3 A solution of ferric chloride in place of 20g used, ferric chloride 16g, aluminum chloride (AlCl ₃ · 6
H ₂ O) 3.5 g and when the solution A is dropped into the solution B, the holding temperature of both solutions is changed from 12 ° C. to 24 ° C.
Further, the pH before the hydrothermal treatment is 11.3 to 10.
In the same manner as in Example 1 except that the particle size was changed to 5, the average particle size in the particle plate surface direction was 200 nm, and the diameter was 15 to 40 n.
Aluminum-containing alpha iron oxide particles having a large number of m pores were obtained. FIG. 3 shows an electron micrograph of the alpha iron oxide particles. Using the alpha iron oxide particles, a polishing tape was prepared in the same manner as in Example 1.

Comparative Example 1 A coating solution was prepared in the same manner as in Example 1 except that single crystal diamond fine particles having a nominal center particle size of 0.15 μm were used in place of the plate-like alpha iron oxide particles having pores. Was prepared, and further an abrasive tape was prepared.

COMPARATIVE EXAMPLE 2 A commercially available alpha iron oxide particle having an average particle diameter of 0.13 μm and a Mohs hardness of 5 having a nearly spherical shape was used in place of the plate-like alpha iron oxide particle having pores. A coating solution was prepared in the same manner as in Example 1, and a polishing tape was prepared.

Comparative Example 3 A plate-like alpha iron oxide particle having a mean particle size of 0.22 μm and a Mohs hardness of 5 and having no hole was used in place of the plate-like alpha iron oxide particle having a hole. Example 1
A coating solution was prepared in the same manner as in, and an abrasive tape was prepared.

Using each of the polishing tapes of Examples 1 to 3 and Comparative Examples 1 to 3 described above, a polishing test was performed on zirconia ceramics by the following method to evaluate the performance. The results are as shown in Table 1.

<Polishing Test> Both ends of the polishing tape were fixed on a glass plate, and the surface was wet with water by using a surface property measuring instrument (“HEIDON-14DR” manufactured by Shinto Scientific Co., Ltd.). Dynamic speed 3,000 mm / min, sliding scale 20 mm,
A zirconia ball having a diameter of 5 mm (manufactured by Nikkato) was reciprocally slid 100 times under a load of 20 g, and the degree of wear of the zirconia ball and the wear marks on the surface of the zirconia ball were observed with a microscope and evaluated as follows. §. Degree of wear ×: Almost not worn △: Slightly worn ○: Very worn ◎: Remarkably worn §. Abrasion mark ×: There are 5 or more scratches on the surface Δ: There are 3 to 4 scratches on the surface ○: There are 1 to 2 scratches on the surface ◎: There is no scratch on the surface

[0048]

As is clear from the results shown in Table 1, the polishing tape of Comparative Example 1 using diamond particles as the abrasive has a large degree of wear and is excellent in polishing ability.
Many abrasive scratches have also occurred. Further, the polishing tape of Comparative Example 2 using spherical alpha iron oxide particles has few scratches, but is clearly inferior in polishing ability. Further, the polishing tape of Comparative Example 3 using the plate-shaped alpha iron oxide particles slightly improved the polishing ability as compared with Comparative Example 2 described above, but it was still not sufficient.

On the other hand, the polishing tapes of Examples 1 to 3 of the present invention all have a polishing ability slightly lower than that of the polishing tape of Comparative Example 1 using diamond particles, but within a satisfactory range. In addition, it was found that there were few scratches, and the polishing tape was well balanced and practically excellent.

[0051]

As described above, according to the present invention, metal oxide particles having a specific particle diameter, which are plate-shaped and have pores in the plate thickness direction, are used in place of conventional diamond particles. As a result, it is possible to provide abrasive particles that are inexpensive and have excellent abrasive ability for polishing optical connectors and the like, and abrasive bodies such as abrasive sheets using the abrasive particles.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a particle structure of abrasive particles produced in Example 1.

2 is an electron micrograph showing the particle structure of abrasive particles produced in Example 2. FIG.

FIG. 3 is an electron micrograph showing a particle structure of abrasive particles produced in Example 3.

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Claims (4)

[Claims] 1. The particles have a plate-like shape, and the average particle diameter in the particle plate surface direction is in the range of 10 nm to 1,000 nm.
Also, 50% or more of the particles are metal oxide particles having pores in the plate thickness direction, and are abrasive particles. 2. The average pore size is 1 nm to 100 n.
The abrasive particles according to claim 1, which are in the range of m. 3. The metal oxide particle according to claim 1, which contains iron or iron as a main component and further contains at least one element selected from aluminum, silicon, a rare earth element and zirconium. Abrasive particles. 4. A polishing body comprising a flexible support and a polishing layer in which the polishing agent is dispersed in a binder, wherein the polishing agent is the polishing particles according to any one of claims 1 to 3. A polishing body comprising: