JP7322957B2 - Abrasive, method for polishing glass, and method for manufacturing glass - Google Patents

Description

TECHNICAL FIELD The present invention relates to an abrasive, a method for polishing glass, and a method for manufacturing glass.

Colloidal silica is generally used as an abrasive for the surface of the glass plate. Furthermore, in recent years, the demand for smoothness of the glass plate has increased, and a higher level of smoothness is required particularly when used as an optical material such as a light guide plate. For example, Patent Document 1 describes that fumed silica is used as an abrasive, Patent Document 2 describes that a resin is used as an abrasive, and Patent Document 3 describes that diamond is polished. It is described that it is used as a drug.

JP 2009-50920 A International Publication No. 2015/046542 JP 2016-216703 A

However, there is room for improvement in abrasives for improving the smoothness of glass. Therefore, it is desired to provide an abrasive that can improve the smoothness of glass.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an abrasive capable of improving the smoothness of glass, a method for polishing glass, and a method for manufacturing glass.

In order to solve the above-described problems and achieve the object, the abrasive according to the present disclosure contains hydrophobic abrasive grains and water.

In order to solve the above-described problems and achieve the object, a glass polishing method according to the present disclosure polishes glass using the polishing agent.

In order to solve the above-described problems and achieve the object, a glass manufacturing method according to the present disclosure manufactures glass using the above glass polishing method.

According to the present invention, the smoothness of glass can be improved.

FIG. 1 is a schematic diagram for explaining the method for manufacturing glass according to the present embodiment.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited by this embodiment, and when there are a plurality of embodiments, the present invention includes a combination of each embodiment. In addition, the range of rounding is included for numerical values.

Abrasive A according to the present embodiment is an abrasive used for polishing the glass 10 . Abrasive A contains water and hydrophobic abrasive B. The water here is preferably pure water. The abrasive grains B in the present embodiment preferably have a value W defined by the following formula (1) of 0.50 or less, more preferably 0.20 or less, and a value W of 0.20 or less. 05 or less is more preferable. When the value W is 0.50 or less, the hydrophobicity is appropriately secured, and the smoothness of the glass 10 can be improved. When the value W is 0.20 or less, the hydrophobicity is more appropriately secured. Therefore, the smoothness of the glass 10 can be more appropriately improved, and by setting the value W to 0.05 or less, the hydrophobicity can be more appropriately secured, and the smoothness of the glass 10 can be more appropriately improved.

W=W ₁ (g)/3.0 (g) (1)

The mass W ₁ (g) is derived as follows.
1: Add 27.0 g of distilled water to 3.0 g of abrasive grain B to form abrasive A, and stir until evenly dispersed.
2: Abrasive A is centrifuged at 15000 rpm for 10 minutes.
3: After centrifugation, remove all but abrasive A sediments.
4: Place the precipitate in a dryer and dry at 90°C for 2 hours.
5: Measure the mass W ₁ (g) of the precipitate after drying.

The abrasive grain B can be said to be a material containing a hydrophobic group on the surface, or a material having a hydrophobic group as a terminal. Hydrophobic groups include, for example, dimethylsilyl groups, trimethylsilyl groups, dimethylpolysiloxane, alkylsilyl groups, methacrylsilyl groups, and fluoro groups. Moreover, the abrasive grains B preferably contain one or more selected from the group consisting of silica, alumina, titania, resin, and carbon. The abrasive grain B more preferably contains one or more selected from the group consisting of silica having a hydrophobic group on its surface, alumina having a hydrophobic group on its surface, and titania having a hydrophobic group on its surface.

The abrasive grains B may be produced by subjecting them to hydrophobic treatment. In particular, when the abrasive grains B are made of a hydrophilic material, it is preferable to make the abrasive grains B hydrophobic by subjecting the material of the abrasive grains B to a hydrophobic treatment. The hydrophobizing treatment is a treatment for providing a hydrophobic group on the surface of a material, in other words, a treatment for providing a hydrophobic group at the end of the material. A known technique can be used as the hydrophobizing treatment method. As a hydrophobization treatment method, for example, a method using a silane coupling agent described in JP-A-2018-141958 and a hydrophobization by a fluorination treatment described in JP-A-2018-141958 are known. In addition, commercially available products after hydrophobizing treatment can be easily obtained.

The average primary particle size of the abrasive grains B is preferably in the range of 5 nm to 500 nm, more preferably in the range of 20 nm to 100 nm. The primary particle size refers to the particle size of one particle, and the average primary particle size refers to the average value of the primary particle sizes. Further, 5 nm to 500 nm here means 5 nm or more and 500 nm or less, and the same applies hereinafter. By setting the average primary particle size to 5 nm or more, the surface roughness of the glass 10 can be reduced, and by setting the average primary particle size to 500 nm or less, the formation of scratches on the surface of the glass 10 can be suppressed.

Although the method for measuring the average primary particle size of the abrasive grains B in the present embodiment is arbitrary, for example, the specific surface area (m ² /g) measured by the BET method and the density of the abrasive grains B (in the case of carbon , for example, 7.215 g cm ³ ), the BET diameter may be determined assuming that the particles are spherical and the abrasive grains have no pores, and the average primary particle diameter may be calculated from the BET diameter. .

In the present embodiment, the total content of the abrasive grains B and water in the polishing agent A is preferably 90% or more, in other words, from 90% to 90% of the total amount of the polishing agent A. 100% is preferred. Further, in the present embodiment, the content of the abrasive grains B in the polishing agent A is preferably 0.0001% to 20%, preferably 0.0005%, in terms of mass ratio with respect to the entire polishing agent A. More preferably ~1%. The glass 10 can be appropriately polished when the total content of the abrasive grains B and water is 90% or more. Further, when the content of the abrasive grains B is 0.0001% or more, the glass 10 can be appropriately polished, and when it is 20% or less, the formation of scratches on the surface of the glass 10 can be suppressed. Further, when the content of the abrasive grains B is 0.0005% or more, the glass 10 can be polished more appropriately, and when it is 1% or less, the formation of scratches on the surface of the glass 10 can be more preferably suppressed.

[Other ingredients]
In addition to the abrasive grains B and water, the polishing agent A contains, as other components, known additives such as PH adjusters such as acids and alkalis, and dispersants. It may contain up to 10% in ratio. Examples of the dispersant include polymers containing terminal carboxyl groups, sulfone groups, hydroxyl groups, etc., nonionic surfactants, anionic surfactants, cationic surfactants, and the like. By adding a dispersing agent to the abrasive grains B, the hydrophobic abrasive grains B can be appropriately dispersed in water to make the polished surface of the glass 10 uniform. For example, the content of the dispersant in the polishing agent A is preferably 0.001% to 10% by mass relative to the entire polishing agent A. When the content of the dispersant is 0.001% or more, the abrasive grains B can be appropriately dispersed in water, and when the content of the dispersant is 10% or less, excessive consumption of the dispersant is avoided. can be suppressed.

In the present embodiment, the glass 10 is polished using the abrasive A as described above to manufacture the glass 10 . Abrasive A can polish glass of any composition. Examples of the glass 10 to be polished with the abrasive A include soda lime glass, borosilicate glass, crystallized glass, and quartz glass. The glass 10 is a flat glass plate in this embodiment, and may be flat or curved. However, the shape of the glass 10 may be arbitrary.

A method for manufacturing the glass 10 according to this embodiment will be described below. FIG. 1 is a schematic diagram for explaining the method for manufacturing glass according to the present embodiment. As shown in FIG. 1, in the manufacturing method according to the present embodiment, first, glass 10 before polishing is prepared (step S10). For example, the glass 10 before polishing is prepared by cutting out a glass manufactured by an arbitrary method such as a melt casting method into a predetermined size and thinning (wrapping) the cut glass. As a method for thinning, for example, dry polishing of the cut glass with a whetstone can be mentioned. However, the method of preparing the glass 10 before polishing is not limited to the above description and is arbitrary.

After preparing the glass 10 before polishing, the glass 10 before polishing is subjected to a cerium oxide polishing step (step S12). In the cerium oxide polishing step, the glass 10 is polished using the cerium oxide polishing agent A1 as a polishing agent. The cerium oxide polishing agent A1 is a polishing agent containing cerium oxide as abrasive grains and water. The cerium oxide contained in the cerium oxide polishing agent A1 is non-hydrophobic cerium oxide, more specifically, hydrophilic cerium oxide having hydrophilic groups on the surface. In the cerium oxide polishing step, the glass 10 is polished using a polishing device D having a polishing pad Da on its surface. In the cerium oxide polishing step, the liquid cerium oxide polishing agent A1 is supplied to the surface of the glass 10, and the polishing pad Da is rotated while being pressed against the surface of the glass 10. Polish the surface. By polishing the surface of the glass 10 using the cerium oxide polishing agent A1, the surface roughness Ra (arithmetic mean roughness) of the surface of the polished glass 10 is, for example, within the range of 0.2 nm to 0.6 nm. and In the cerium oxide polishing step, at least one of the one surface 10a of the glass 10 and the surface 10b opposite to the surface 10a is polished. Further, after performing the cerium oxide polishing step, the glass 10 may be washed by a method similar to step S16 described later. In the cerium oxide polishing step, the polishing apparatus D having the structure shown in FIG. may be polished.

After polishing the glass 10 using the cerium oxide polishing agent A1, a silica polishing step is performed on the glass 10 polished using the cerium oxide polishing agent A1 (step S14). In the silica polishing step, the glass 10 is polished using silica polishing agent A2 as a polishing agent. Silica polishing agent A2 is a polishing agent containing silica as abrasive grains and water. The silica contained in the silica polishing agent A2 is non-hydrophobic silica, more specifically, hydrophilic silica having hydrophilic groups on its surface. Colloidal silica may be used as the silica contained in the silica abrasive A2. In the silica polishing step, the polishing device D is used to polish the glass 10 . In the silica polishing step, the surface of the glass 10 is polished by rotating the polishing pad Da while pressing the polishing pad Da against the surface of the glass 10 while supplying the liquid silica polishing agent A2 to the surface of the glass 10. Grind. By polishing the surface of the glass 10 with the silica polishing agent A2, the surface roughness Ra of the surface of the polished glass 10 is set within the range of 0.1 nm to 0.3 nm, for example. In addition, in the silica polishing step, at least one of the one surfaces 10a and 10b of the glass 10 is polished. In addition, in the silica polishing step, the glass 10 is not limited to being polished using the polishing apparatus D, and the glass 10 may be polished by any method as long as the silica polishing agent A2 is used.

After polishing the glass 10 with the silica polishing agent A2, the glass 10 is washed (step S16). In step S16, the glass 10 polished with the silica polishing agent A2 is put into the washing container E and washed. For example, the cleaning container E is filled with a liquid such as water, and the liquid is aerated by an aerator. The glass 10 is washed by being immersed in the liquid in the washing vessel E and aerated by an aerator. However, the method for cleaning the glass 10 is not limited to this and may be arbitrary. Also, cleaning the glass 10 is not essential.

After cleaning the glass 10, a polishing step is performed on the cleaned glass 10 (step S18). In the polishing step, the polishing agent A is used to polish the glass 10, but a dummy polishing step may be provided in advance under the same conditions as the polishing step. In the polishing step, the glass 10 is polished using the polishing device D1. The polishing apparatus D1 includes, for example, a cylindrical polishing pad D1a. The surface of the glass 10 is polished by relatively moving the glass. In the polishing step, the surface of the glass 10 is polished by supplying the liquid polishing agent A to the surface of the glass 10 and relatively moving the polishing pad D1a while being pressed against the surface of the glass 10 . By polishing the surface of the glass 10 with the polishing agent A, the surface roughness Ra of the polished surface of the glass 10 is, for example, within a range of 0.03 nm or more and less than 0.07 nm. In the polishing step, at least one of the surfaces 10a and 10b of the glass 10 is polished. In the polishing step, the cylindrical polishing pad D1a is not limited to polishing the glass. For example, the polishing device D may be used for polishing. That is, in the polishing step, the glass 10 may be polished by any method as long as the polishing agent A is used.

In the polishing step, the amount of polishing agent A supplied to the surface of the glass 10 per unit time is preferably 1 mL/min to 30 mL/min. By setting the supply rate of polishing agent A to 1 mL/min or more, a sufficient amount of abrasive grains is supplied to the polishing pad D1a, and the surface smoothness is improved. can be suppressed. Further, in the polishing step, the pressing force, which is the pressure for pressing the polishing pad against the surface of the glass 10, is preferably 40 g/cm ² to 200 g/cm ² . By setting the pressing force to 40 g/cm ² or more, the glass 10 can be appropriately polished, and by setting it to 200 g/cm ² or less, formation of scratches on the surface of the glass 10 can be suppressed. The pressing force of the polishing pad in the polishing step may be set smaller than the pressing force of the polishing pad in the cerium oxide polishing step and the silica polishing step. Further, in the polishing step, it is preferable to set the polishing time with the polishing pad to 1 minute or more and 10 minutes or less. By setting the polishing time to 1 minute or longer, the glass 10 can be appropriately polished, and by setting the polishing time to 10 minutes or shorter, formation of scratches on the surface of the glass 10 can be suppressed. The polishing time in the polishing step may be set shorter than the polishing time in the cerium oxide polishing step and the silica polishing step.

After polishing the glass 10 with the polishing agent A, the glass 10 is washed (step S20). In step S20, the glass 10 is put into the cleaning container E using the abrasive A, and the glass 10 is cleaned in the same manner as in step S16. However, the method for cleaning the glass 10 in step S20 is also arbitrary, and step S20 is not an essential process.

As described above, in the present embodiment, the glass 10 is polished with the cerium oxide polishing agent A1, and after polishing with the cerium oxide polishing agent A1, the glass 10 is polished with the silica polishing agent A2 and then with the silica polishing agent A2. The polished glass 10 is polished with a polishing agent A. By polishing the glass 10 in this manner, the glass 10 having a small surface roughness and high smoothness can be manufactured. However, the polishing process for the glass 10 is not limited to this, and for example, the polishing with the silica polishing agent A2 (step S14) may not be performed. In this case, the glass 10 is polished with the cerium oxide polishing agent A1, and the glass 10 polished with the cerium oxide polishing agent A1 is polished with the polishing agent A. Polishing with the cerium oxide polishing agent A1 is not essential, and at least the glass 10 may be polished with the polishing agent A in this embodiment.

As described above, the abrasive A according to this embodiment contains the hydrophobic abrasive grains B and water. By using the hydrophobic abrasive grains B as the polishing agent A, the surface roughness of the glass 10 can be reduced and the smoothness of the glass 10 can be improved.

Moreover, the abrasive grains B preferably contain one or more selected from the group consisting of silica, alumina, titania, resin, and carbon. By using these materials as the abrasive grains B, the surface roughness of the glass 10 can be reduced and the smoothness of the glass 10 can be improved.

Further, the abrasive grain B preferably contains one or more selected from the group consisting of silica having a hydrophobic group on its surface, alumina having a hydrophobic group on its surface, and titania having a hydrophobic group on its surface. By using these materials as the abrasive grains B, the surface roughness of the glass 10 can be reduced and the smoothness of the glass 10 can be improved.

Further, the abrasive grains B preferably have a value W defined below of 0.50 or less. When the value W is 0.50 or less, the hydrophobic property is appropriately ensured, and the smoothness of the glass 10 can be improved.
1: Add 27.0 g of distilled water to 3.0 g of abrasive grains to form a polishing agent, and stir until it is uniformly dispersed.
2: The abrasive is centrifuged at 15000 rpm for 10 minutes.
3: After centrifugation, remove all but abrasive sediments.
4: Place the precipitate in a dryer and dry at 90°C for 2 hours.
5: Measure the mass (g) of the precipitate after drying.
6: W = (mass of precipitate after drying (g) / 3.0 (g))

Also, the content of the abrasive grains B is preferably in the range of 0.0001% to 20% by mass relative to the entire polishing agent A. When the content of the abrasive grains B is 0.0001% or more, the glass 10 can be appropriately polished, and when the content of the abrasive grains B is 20% or less, the formation of scratches on the surface of the glass 10 can be suppressed. .

Moreover, it is preferable that the abrasive A further contains a dispersant. By adding a dispersant to the polishing agent A, the hydrophobic abrasive grains B can be appropriately dispersed in water, and the polished surface of the glass 10 can be made uniform.

Abrasive A is also used for glass polishing. By polishing the glass 10 with the abrasive A, the smoothness of the glass 10 can be improved.

Further, in the method for polishing the glass 10 according to the present embodiment, the polishing agent A is used to polish the glass 10 . By polishing the glass 10 with the abrasive A, the smoothness of the glass 10 can be improved.

Further, the method for polishing the glass 10 according to the present embodiment includes a cerium oxide polishing step and a polishing step performed after the cerium oxide step. In the cerium oxide polishing step, the glass 10 is polished with a cerium oxide polishing agent A1 containing cerium oxide. In the polishing step, the glass 10 is polished with polishing agent A after the cerium oxide polishing step. In this polishing method, the surface roughness Ra of the glass 10 can be reduced and the smoothness of the glass 10 can be improved by polishing the glass 10 with the cerium oxide polishing agent A1 and then polishing the glass with the polishing agent A.

In addition, the method for polishing glass 10 according to the present embodiment further includes a silica polishing step of polishing glass 10 with silica polishing agent A2 containing silica after the cerium oxide polishing step. In the polishing step, the glass 10 is polished with polishing agent A after the silica polishing step. In this polishing method, the glass 10 polished with the cerium oxide polishing agent A1 and the silica polishing agent A2 is polished with the polishing agent A, thereby reducing the surface roughness Ra of the glass 10 and improving the smoothness of the glass 10. can be improved to

Moreover, the manufacturing method of the glass 10 which concerns on this embodiment manufactures the glass 10 using the polishing method of the glass 10 which concerns on this embodiment. In this manufacturing method, the smoothness of the glass 10 can be improved by polishing the glass 10 with the abrasive A to manufacture the glass 10 . In particular, since the glass 10 polished with the polishing agent A has high smoothness, it can be suitably used as an optical element such as a light guide plate.

(Example)
Next, examples will be described. It should be noted that the embodiment may be changed as long as the effect of the invention is exhibited. In Examples and Comparative Examples, different abrasives were prepared, the glass was polished using each abrasive, and the surface roughness Ra of the glass after polishing was measured. The abrasive was evaluated based on. A more detailed description will be given below.

[Glass for evaluation]
In the examples and comparative examples, the length of the first side was 50 mm, the length of the second side intersecting the first side was 50 mm, the thickness was 1.0 mm, and the surface roughness Ra (arithmetic mean roughness A glass with a thickness of 0.150 nm was prepared. As glasses, alkali-free borosilicate glass, more specifically AN100 manufactured by AGC Corporation, and aluminosilicate glass, more specifically Rollland α' manufactured by AGC Corporation, were prepared. In Example 6, Rollland α' was used.

[Abrasive]
Then, the prepared glass was prepared with abrasives having compositions shown in Examples and Comparative Examples shown in Table 1 below.
Abrasive grains of the abrasives of Examples 1 and 6 are hydrophobic silica using AEROSIL RX200 manufactured by Nippon Aerosil Co., Ltd. Abrasive grains of the polishing agent of Example 2 are hydrophobic silica using AEROSIL RY200 manufactured by Nippon Aerosil Co., Ltd. Abrasive grains of the polishing agent of Example 3 are hydrophobic alumina using AEROXIDE Alu C805 manufactured by Nippon Aerosil Co., Ltd. The abrasive grains of the abrasive of Example 4 are hydrophobic resins using XC99 A8808 manufactured by Momentive Performance Materials Japan. Abrasive grains of the polishing agent of Example 5 are hydrophobic titania using AEROXIDE TiO2 T805 manufactured by Nippon Aerosil Co., Ltd.
Abrasive grains of the polishing agent of Comparative Example 1 are hydrophilic silica using AEROSIL 200 manufactured by Nippon Aerosil Co., Ltd. Abrasive grains of the abrasive of Comparative Example 2 are hydrophilic alumina using AEROXIDE Alu C manufactured by Nippon Aerosil Co., Ltd. Abrasive grains of the polishing agent of Comparative Example 3 are hydrophilic titania using AEROXIDE TiO2 P25 manufactured by Nippon Aerosil Co., Ltd.

[Evaluation condition]
Further, the value W specified in the above embodiment was calculated for each abrasive grain of Examples and Comparative Examples.
The hydrophobicity of abrasive grains with a value W of 0.05 or less is evaluated as A,
The hydrophobicity of abrasive grains with a value W greater than 0.05 and 0.20 or less is rated B,
The hydrophobicity of abrasive grains with a value W of greater than 0.20 and less than or equal to 0.50 was given a C rating.
Evaluation from A evaluation to C evaluation is evaluated as hydrophobic,
Abrasive grains with a value W greater than 0.50 were rated as being hydrophilic rather than hydrophobic.

1 g of abrasive grains shown in Table 1 and 99 g of water were mixed and stirred until the abrasive grains were uniformly dispersed in the water to prepare respective abrasives. Using this abrasive, the prepared glass was polished under the following conditions. That is, FAM12BS manufactured by Speedfam Co., Ltd. was used as the polishing apparatus, suede pad NP787 manufactured by FILWEL was used as the polishing pad, the rotation speed of the surface plate was 40 rpm, and the pressing force of the polishing pad was 44 g/cm ² . The time was set to 1 minute, and the supply amount of the abrasive was set to 5 ml/min.

The surface roughness Ra (arithmetic surface roughness) of the glass thus polished using each polishing agent was measured by CypherS AFM manufactured by Asylum Research.
For glass after cerium oxide polishing,
The case where the surface roughness Ra is smaller than 0.050 nm is circled,
Triangular when the surface roughness Ra is 0.050 nm or more and less than 0.070 nm,
A case where the surface roughness Ra was 0.070 nm or more was regarded as x.
Circles and triangles were rated as passing.

As shown in Table 1, it can be seen that the evaluation result of the surface roughness Ra is acceptable in the example, while the evaluation result of the surface roughness Ra is unacceptable in the comparative example. That is, it can be seen that the use of hydrophobic abrasive grains as a polishing agent can reduce the surface roughness of the glass and improve the smoothness of the glass. It can also be seen that the higher the hydrophobicity, that is, the smaller the value of W, the smaller the value of the surface roughness Ra. Moreover, as shown in Example 6, it can be seen that the smoothness of the glass can be improved even if the type of glass is changed when hydrophobic abrasive grains are used as the polishing agent.

Although the embodiment of the present invention has been described above, the embodiment is not limited by the contents of this embodiment. In addition, the components described above include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the components described above can be combined as appropriate. Furthermore, various omissions, replacements, or modifications of components can be made without departing from the gist of the above-described embodiments.

10 Glass A Polishing agent A1 Cerium oxide polishing agent A2 Silica polishing agent B Abrasive grain

Claims (9)

A polishing agent containing hydrophobic abrasive grains and water,
The content of the hydrophobic abrasive grains is in the range of 0.0005% to 1% by mass with respect to the entire abrasive,
The abrasive grains are
containing a dimethylsilyl group, a trimethylsilyl group, a dimethylpolysiloxane, an alkylsilyl group, a methacrylsilyl group, or a fluoro group as a hydrophobic group on the surface ;
An abrasive whose W defined below is 0.50 or less.
1: Add 27.0 g of distilled water to 3.0 g of abrasive grains to form a polishing agent, and stir until it is uniformly dispersed.
2: The abrasive is centrifuged at 15000 rpm for 10 minutes.
3: After centrifugation, remove all but abrasive sediments.
4: Place the precipitate in a dryer and dry at 90°C for 2 hours.
5: Measure the mass (g) of the precipitate after drying.
6: W = (mass of precipitate after drying (g) / 3.0 (g)) 2. The abrasive according to claim 1, wherein said hydrophobic abrasive grains contain one or more selected from the group consisting of silica, alumina, titania, resin and carbon. Said hydrophobic abrasive grains contain one or more selected from the group consisting of silica containing a hydrophobic group on the surface, alumina containing a hydrophobic group on the surface, and titania containing a hydrophobic group on the surface. Item 3. The abrasive according to item 2. 4. The abrasive according to any one of claims 1 to 3 , further comprising a dispersing agent. 5. The abrasive according to any one of claims 1 to 4 , which is used for polishing glass. A method for polishing glass, comprising polishing glass using the polishing agent according to any one of claims 1 to 5 . a cerium oxide polishing step of polishing the glass with a cerium oxide abrasive containing cerium oxide;
a polishing step of polishing the glass with the abrasive after the cerium oxide polishing step;
The method for polishing glass according to claim 6 , comprising: further comprising, after the cerium oxide polishing step, polishing the glass with a silica polishing agent containing silica;
8. The method of polishing glass according to claim 7 , wherein the glass is polished with the polishing agent after the silica polishing step. A method for producing glass, comprising producing glass using the method for polishing glass according to any one of claims 6 to 8 .

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